Prophylactic activity of orally administered dry-heat-sterilized Acremonium egyptiacum against Trypanosoma congolense-induced animal African trypanosomosis

Animal African trypanosomosis (AAT) is an important global disease of livestock that causes economic losses of up to 4.5 billion US dollars per year. Thus, eliminating AAT in endemic countries will improve agricultural productivity and economic growth. To prevent AAT, vector control and the development of prophylactic drugs are crucial. Ascofuranone (AF) is a bioactive fungal compound with proven in vitro trypanocidal potency and in vivo treatment efficacy. However, the complex stereoselective synthesis of AF has prevented its cost-effective industrial production. Recently, a genetically modified strain of Acremonium egyptiacum fungus that produces a high yield of AF was developed. Therefore, we hypothesized that the oral administration of the AF-producing fungus itself may be effective against AAT. Hence, this study aimed to evaluate the prophylactic activity of orally administered dry-heat-sterilized A. egyptiacum against Trypanosoma congolense IL3000 infection using a mouse model. The survival rate was significantly prolonged (p = 0.009), and parasitemia was suppressed in all AF-fungus-treated groups (Group 1-9) compared with that in the untreated control group (Group 10). Hence, the trypanocidal activity of AF was retained after dry-heat-sterilization of the AF-producing fungus and that its oral administration effectively prevented AAT. Since AAT is endemic to rural areas with underdeveloped veterinary infrastructure, dry-heat-sterilized A. egyptiacum would be the most cost-effective potential treatment for AAT.

Mass Drug Administration to Reduce Malaria Transmission: A Systematic Review and Meta-Analysis

Malaria remains a significant cause of morbidity and mortality, even in low-transmission settings. With the advent of longer acting, more effective, and well-tolerated antimalarials, there is renewed interest in the efficacy of mass drug administration (MDA) to accelerate to elimination. We conducted a systematic review and meta-analysis to assess the efficacy of MDA to reduce the incidence and prevalence of Plasmodium falciparum (Pf) and Plasmodium vivax (Pv) infection. From 1,044 articles screened, 14 articles, including 10 randomized controlled trials (RCTs), were identified. Five included data on Pf only; five included Pf and Pv. Two of the Pf studies were conducted in areas of high-moderate transmission, the remainder were in areas of low-very low transmission. In higher transmission areas, MDA reduced incidence of Pf parasitemia (rate ratio = 0.61, 95% CI: 0.40-0.92; moderate certainty) 1 to 3 months after drug administration; no significant effect of MDA on Pf parasitemia prevalence was detected 1 to 3 months post-MDA (risk ratio [RR] = 1.76, 95% CI: 0.58-5.36; low certainty). In lower transmission settings, both incidence and prevalence of Pf parasitemia were reduced 1 to 3 months post-MDA (rate ratio = 0.37, 95% CI: 0.21-0.66; RR = 0.25, 95% CI: 0.15-0.41, respectively). Pv prevalence was reduced 1 to 3 months post-MDA (RR = 0.15, 95% CI: 0.10-0.24); there were no RCTs providing data on incidence of Pv. There was no significant effect of MDA at later time points. MDA may have short-term benefits; however, there was no evidence for longer term impact, although none of the trials assessed prolonged interventions.

Relative effects of climate factors and malaria control interventions on changes of parasitaemia risk in Burkina Faso from 2014 to 2017/2018

BACKGROUND

In Burkina Faso, the prevalence of malaria has decreased over the past two decades, following the scale-up of control interventions. The successful development of malaria parasites depends on several climatic factors. Intervention gains may be reversed by changes in climatic factors. In this study, we investigated the role of malaria control interventions and climatic factors in influencing changes in the risk of malaria parasitaemia.

METHODS

Bayesian logistic geostatistical models were fitted on Malaria Indicator Survey data from Burkina Faso obtained in 2014 and 2017/2018 to estimate the effects of malaria control interventions and climatic factors on the temporal changes of malaria parasite prevalence. Additionally, intervention effects were assessed at regional level, using a spatially varying coefficients model.

RESULTS

Temperature showed a statistically important negative association with the geographic distribution of parasitaemia prevalence in both surveys; however, the effects of insecticide-treated nets (ITNs) use was negative and statistically important only in 2017/2018. Overall, the estimated number of infected children under the age of 5 years decreased from 704,202 in 2014 to 290,189 in 2017/2018. The use of ITNs was related to the decline at national and regional level, but coverage with artemisinin-based combination therapy only at regional level.

CONCLUSION

Interventions contributed more than climatic factors to the observed change of parasitaemia risk in Burkina Faso during the period of 2014 to 2017/2018. Intervention effects varied in space. Longer time series analyses are warranted to determine the differential effect of a changing climate on malaria parasitaemia risk.

Asymptomatic and submicroscopic Plasmodium infections in an area before and during integrated vector control in Homa Bay, western Kenya

BACKGROUND

Long-lasting insecticidal nets (LLINs) have been the primary vector control strategy until indoor residual spraying (IRS) was added in Homa Bay and Migori Counties in western Kenya. The objective of this study was to evaluate the impact of LLINs integrated with IRS on the prevalence of asymptomatic and submicroscopic Plasmodium infections in Homa Bay County.

METHODS

A two-stage cluster sampling procedure was employed to enroll study participants aged ≥ 6 months old. Four consecutive community cross-sectional surveys for Plasmodium infection were conducted in residents of Homa Bay county, Kenya. Prior to the start of the study, all study households received LLINs, which were distributed between June 2017 and March 2018. The first (February 2018) and second (June 2018) surveys were conducted before and after the first round of IRS (Feb-Mar 2018), while the third (February 2019) and fourth (June 2019) surveys were conducted before and after the second application of IRS (February-March 2019). Finger-prick blood samples were obtained to prepare thick and thin smears for microscopic determination and qPCR diagnosis of Plasmodium genus.

RESULTS

Plasmodium spp. infection prevalence by microscopy was 18.5% (113/610) before IRS, 14.2% (105/737) and 3.3% (24/720) after the first round of IRS and 1.3% (11/849) after the second round of IRS (p < 0.0001). Submicroscopic (blood smear negative, qPCR positive) parasitaemia reduced from 18.9% (115/610) before IRS to 5.4% (46/849) after IRS (p < 0.0001). However, the proportion of PCR positive infections that were submicroscopic increased from 50.4% (115/228) to 80.7% (46/57) over the study period (p < 0.0001). Similarly, while the absolute number and proportions of microscopy positives which were asymptomatic decreased from 12% (73/610) to 1.2% (9/849) (p < 0.0001), the relative proportion increased. Geometric mean density of P. falciparum parasitaemia decreased over the 2-year study period (p < 0.0001).

CONCLUSIONS

These data suggest that two annual rounds of IRS integrated with LLINs significantly reduced the prevalence of Plasmodium parasitaemia, while the proportion of asymptomatic and submicroscopic infections increased. To reduce cryptic P. falciparum transmission and improve malaria control, strategies aimed at reducing the number of asymptomatic and submicroscopic infections should be considered.

Effectiveness and compliance to the use of sulphadoxine-pyrimethamine as a prophylaxis for malaria among pregnant women in Port Harcourt, Rivers State, Nigeria

BACKGROUND

Malaria during pregnancy escalates the damaging consequence to the mother and neonate. The usage of intermittent preventive treatment of malaria (IPTp) with sulfadoxine-pyrimethamine (SP) is recommended for averting the deleterious consequences of malaria in pregnancy. This study evaluated the effectiveness of, and compliance with the use of SP for malaria among pregnant women in Port Harcourt Rivers State, Nigeria.

METHOD

A total of 300 samples of maternal peripheral blood (MPB), 84 neonatal cord blood (NCB) and 84 placental blood (PLB) were collected from consenting mothers. Malaria parasitaemia were analysed using standard parasitological methods, and bio-data of consenting mothers were collected through questionnaires and from ANC records.

RESULTS

Out of the samples examined for MPB, 59(19.7%) tested positive to malaria. Those with only primary education (57.1%) and women of age ≤ 20yrs (25%) had higher prevalence. Women who took SP had significantly lower prevalence (17.6%) than those that took other drugs (36.4%) (p < 0.05). Malaria prevalence was highest among women who had 3 months interval between each dose (39.1%), followed by those of 2months (23.7%) and those of 1 month (7.0%) (p < 0.05). The primigravidaes (22.8%) had an insignificantly higher prevalence than secundigravidae (19.4%) and multigravidae (15.9%). Also, 30.5% of women who registered in their third trimester of pregnancy had a significantly higher malaria parasitaemia than those who registered during their first 8.10%, or second trimesters, 19.4%. Of the 84 MPB-NCB-PLB pairedamples examined, 16.7%, 8.3% and 25% respectively were infected with malaria parasitaemia. On frequency of compliance, mothers who took SP once (37.5%) had a significantly higher MPB parasitaemia than those who took it twice (7.84%) and those of thrice (6.25%). Neonatal cord blood parasitaemia prevalence revealed that those that took SP once, that is, 25%, had a higher prevalence than others like those of twice (5.88%) and thrice (0%) respectively.

CONCLUSION

The use and compliance of SP reduced the prevalence of malaria among pregnant women and their new-borns.

Drivers of long-lasting insecticide-treated net utilisation and parasitaemia among under-five children in 13 States with high malaria burden in Nigeria

BACKGROUND

Although Nigeria has made some progress in malaria control, there are variations across States. We investigated the factors associated with utilisation of long-lasting insecticide-treated net (LLIN) and parasitaemia among under-five children in 13 States with high malaria burden.

METHOD

Data from the 2015 Nigeria Malaria Indicator Survey and 2018 Demographic and Health Survey were obtained and analysed. The 2015 and 2018 data were compared to identify States with increase or reduction in parasitaemia. Analysis was done for all the 13 study States; four States with increased parasitaemia and nine States with reduction. Random-effects logit models were fitted to identify independent predictors of LLIN utilisation and parasitaemia.

RESULTS

LLIN was used by 53.4% of 2844 children, while parasitaemia prevalence was 26.4% in 2018. Grandchildren (AOR = 5.35, CI: 1.09-26.19) were more likely to use LLIN while other relatives (AOR = 0.33, CI: 0.11-0.94) were less likely compared to children of household-heads. LLIN use was more common in children whose mother opined that only weak children could die from malaria (AOR = 1.83, CI: 1.10-3.10). Children whose mothers obtained net from antenatal or immunisation clinics (AOR = 5.30, CI: 2.32-12.14) and campaigns (AOR = 1.77, CI: 1.03-3.04) were also more likely to use LLIN. In contrast, LLIN utilisation was less likely among children in female-headed households (AOR = 0.51, CI: 0.27-0.99) and those in poor-quality houses (AOR = 0.25, CI: 0.09-0.72). Children aged 24-59 months compared to 0-11 months (AOR = 1.78, CI: 1.28-2.48), those in whom fever was reported (AOR = 1.31, CI: 1.06-1.63) and children of uneducated women (AOR = 1.89, CI: 1.32-2.70) were more likely to have parasitaemia. The likelihood of parasitaemia was higher among children from poor households compared to the rich (AOR = 2.06, CI: 1.24-3.42). The odds of parasitaemia were 98% higher among rural children (AOR = 1.98, CI: 1.37-2.87).

CONCLUSION

The key drivers of LLIN utilisation were source of net and socioeconomic characteristics. The latter was also a key factor associated with parasitaemia. These should be targeted as part of integrated malaria elimination efforts.

Baseline Asymptomatic Malaria Infection and Immunogenicity of Recombinant Vesicular Stomatitis Virus-Zaire Ebola Virus Envelope Glycoprotein

BACKGROUND

The effect of malaria infection on the immunogenicity of the recombinant vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein (GP) vaccine (rVSVΔG-ZEBOV-GP) (ERVEBO) is unknown.

METHODS

The Sierra Leone Trial to Introduce a Vaccine Against Ebola (STRIVE) vaccinated 7998 asymptomatic adults with rVSVΔG-ZEBOV-GP during the 2014-2016 Ebola epidemic. In STRIVE's immunogenicity substudy, participants provided blood samples at baseline and at 1, 6, and 9-12 months. Anti-GP binding and neutralizing antibodies were measured using validated assays. Baseline samples were tested for malaria parasites by polymerase chain reaction.

RESULTS

Overall, 506 participants enrolled in the immunogenicity substudy and had ≥1 postvaccination antibody titer. Of 499 participants with a result, baseline malaria parasitemia was detected in 73 (14.6%). All GP enzyme-linked immunosorbent assay (ELISA) and plaque reduction neutralization test (PRNT) geometric mean titers (GMTs) at 1, 6, and 9-12 months were above baseline, and 94.1% of participants showed seroresponse by GP-ELISA (≥2-fold rise and ≥200 ELISA units/mL), while 81.5% showed seroresponse by PRNT (≥4-fold rise) at ≥1 postvaccination assessment. In participants with baseline malaria parasitemia, the PRNT seroresponse proportion was lower, while PRNT GMTs and GP-ELISA seroresponse and GMTs showed a trend toward lower responses at 6 and 9-12 months.

CONCLUSION

Asymptomatic adults with or without malaria parasitemia had robust immune responses to rVSVΔG-ZEBOV-GP, persisting for 9-12 months. Responses in those with malaria parasitemia were somewhat lower.

Increased malaria parasitaemia among adults living with HIV who have discontinued cotrimoxazole prophylaxis in Kitgum district, Uganda

Background

Although WHO recommends cotrimoxazole (CTX) discontinuation among HIV patients who have undergone immune recovery and are living in areas of low prevalence of malaria, some countries including Uganda recommend CTX discontinuation despite having a high malaria burden. We estimated the prevalence and factors associated with malaria parasitaemia among adults living with HIV attending hospital outpatient clinic before and after discontinuation of CTX prophylaxis.

Methods

Between March and April 2019, 599 participants aged 18 years and above, and attending Kitgum hospital HIV clinic in Uganda were enrolled in a cross study. A standardized questionnaire was administered and physical examination conducted. A finger-prick blood sample was collected for identification of malaria parasites by microscopy. The prevalence of parasitaemia was estimated and compared among participants on and those who had discontinued CTX prophylaxis, and factors associated with malaria parasitaemia assessed.

Results

Of the enrolled participants, 27 (4.5%) had malaria parasites and 452 (75.5%) had stopped CTX prophylaxis. Prevalence of malaria parasitaemia was significantly higher in participants who had stopped CTX prophylaxis (5.5% versus 1.4% p = 0.03) and increased with increasing duration since the discontinuation of prophylaxis. Compared to participants taking CTX, those who discontinued prophylaxis for 3–5 months and >5 months were more likely to have malaria parasites (adjusted prevalence ratio (aPR) = 1.64, 95% CI 0.37–7.29, p = 0.51, and aPR = 6.06, 95% CI 1.34–27.3, P = 0.02). Low CD4 count (< 250cells/mm³) was also associated with increased risk of having parasites (aPR = 4.31, 95% CI 2.13–8.73, p <0.001).

Conclusion

People from malaria endemic settings living with HIV have a higher prevalence of malaria parasitaemia following discontinuation of CTX compared to those still on prophylaxis. The risk increased with increasing duration since discontinuation of the prophylaxis. HIV patients should not discontinue CTX prophylaxis in areas of Uganda where the burden of malaria remains high. Other proven malaria control interventions may also be encouraged in HIV patients following discontinuation of CTX prophylaxis.

A systematic review and meta-analysis of dihydroartemisinin-piperaquine versus sulphadoxine-pyrimethamine for malaria prevention in pregnancy

BACKGROUND

Intermittent preventive treatment (IPT) with sulphadoxine-pyrimethamine (SP) is recommended for preventing maternal and fetal effects of malaria in pregnancy. Increasing parasite resistance to SP has necessitated the search for an alternative medication.

OBJECTIVE

To compare dihydroartemisinin-piperaquine (DP) and sulphadoxine-pyrimethamine in preventing malaria during pregnancy.

SEARCH STRATEGY

Databases including CENTRAL, MEDLINE, and ICTRP were searched until August 2018.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials that compared DP with SP given to pregnant women to prevent adverse maternal or fetal effects of malaria were included.

DATA COLLECTION AND ANALYSIS

Quality of evidence was determined with GRADE criteria. Effectiveness measures were calculated using odds ratios at 95% confidence intervals.

RESULTS

Three randomized controlled trials were included. Compared with IPT-SP, moderate certainty evidence indicated that women who received IPT-DP had significantly lower risks of clinical malaria during pregnancy. High certainty evidence showed intermittent screening and treatment with DP did not reduce placental malaria or maternal parasitemia at delivery. Effect of DP on low birth weight and adverse birth outcomes was minimal.

CONCLUSIONS

Moderate certainty evidence suggests that IPT-DP may reduce maternal and placental malaria compared with IPT-SP, and monthly DP is more effective than SP in reducing placental malaria.

PROSPERO ID

CRD42018084651.

A therapeutic vaccine prototype induces protective immunity and reduces cardiac fibrosis in a mouse model of chronic Trypanosoma cruzi infection

Chagas disease, caused by the parasite Trypanosoma cruzi, develops into chronic Chagas’ cardiomyopathy in ~30% of infected individuals, characterized by conduction disorders, arrhythmias, heart failure, and even sudden cardiac death. Current anti-parasitic treatments are plagued by significant side effects and poor efficacy in the chronic phase of disease; thus, there is a pressing need for new treatment options. A therapeutic vaccine could bolster the protective T_H1-mediated immune response, thereby slowing or halting the progression of chronic Chagas’ cardiomyopathy. Prior work in mice has demonstrated therapeutic efficacy of a Tc24 recombinant protein vaccine in the acute phase of Chagas disease. However, it is anticipated that humans will be vaccinated therapeutically when in the chronic phase of disease. This study investigates the therapeutic efficacy of a vaccine prototype containing recombinant protein Tc24, formulated with an emulsion containing the Toll-like receptor 4 agonist E6020 as an immunomodulatory adjuvant in a mouse model of chronic T. cruzi infection. Among outbred ICR mice vaccinated during chronic T. cruzi infection, there is a significant increase in the number of animals with undetectable systemic parasitemia (60% of vaccinated mice compared to 0% in the sham vaccine control group), and a two-fold reduction in cardiac fibrosis over the control group. The vaccinated mice produce a robust protective T_H1-biased immune response to the vaccine, as demonstrated by a significant increase in antigen-specific IFNγ-production, the number of antigen-specific IFNγ-producing cells, and IgG2a antibody titers. Importantly, therapeutic vaccination significantly reduced cardiac fibrosis in chronically infected mice. This is a first study demonstrating therapeutic efficacy of the prototype Tc24 recombinant protein and E6020 stable emulsion vaccine against cardiac fibrosis in a mouse model of chronic T. cruzi infection.

Chagas disease is a parasitic infection that can cause severe heart disease. Current treatments do not work well and have significant side effects. Because of this, the authors created a new vaccine prototype with the goal that it could be given to infected people to prevent Chagas-associated heart disease. The vaccine contains a manufactured protein identical to a protein in the parasite (called Tc24) as well as a component to help the body produce a protective immune response (a vaccine adjuvant called E6020). The vaccine would boost the body’s natural immune response to the parasite infection, reducing the number of parasites in the body, and protecting the heart. Frequently, people are not diagnosed until later in the infection, because the early (or acute) stage of disease can be mistaken for a common cold. Because of this, it is important to test the vaccine when given in the later (or chronic) stage of infection. The authors tested the vaccine in a mouse model of chronic T. cruzi infection and found that the vaccinated mice had lower levels of parasites in their body and less damage to their hearts. This research shows promising value of a therapeutic vaccine to prevent Chagas-associated heart disease in a mouse model, with the hope that the same effect could be found in humans one day.

Cytomegalovirus vectors expressing Plasmodium knowlesi antigens induce immune responses that delay parasitemia upon sporozoite challenge

The development of a sterilizing vaccine against malaria remains one of the highest priorities for global health research. While sporozoite vaccines targeting the pre-erythrocytic stage show great promise, it has not been possible to maintain efficacy long-term, likely due to an inability of these vaccines to maintain effector memory T cell responses in the liver. Vaccines based on human cytomegalovirus (HCMV) might overcome this limitation since vectors based on rhesus CMV (RhCMV), the homologous virus in rhesus macaques (RM), elicit and indefinitely maintain high frequency, non-exhausted effector memory T cells in extralymphoid tissues, including the liver. Moreover, RhCMV strain 68-1 elicits CD8+ T cells broadly recognizing unconventional epitopes exclusively restricted by MHC-II and MHC-E. To evaluate the potential of these unique immune responses to protect against malaria, we expressed four Plasmodium knowlesi (Pk) antigens (CSP, AMA1, SSP2/TRAP, MSP1c) in RhCMV 68-1 or in Rh189-deleted 68-1, which additionally elicits canonical MHC-Ia-restricted CD8+ T cells. Upon inoculation of RM with either of these Pk Ag expressing RhCMV vaccines, we obtained T cell responses to each of the four Pk antigens. Upon challenge with Pk sporozoites we observed a delayed appearance of blood stage parasites in vaccinated RM consistent with a 75-80% reduction of parasite release from the liver. Moreover, the Rh189-deleted RhCMV/Pk vectors elicited sterile protection in one RM. Once in the blood, parasite growth was not affected. In contrast to T cell responses induced by Pk infection, RhCMV vectors maintained sustained T cell responses to all four malaria antigens in the liver post-challenge. The delayed appearance of blood stage parasites is thus likely due to a T cell-mediated inhibition of liver stage parasite development. As such, this vaccine approach can be used to efficiently test new T cell antigens, improve current vaccines targeting the liver stage and complement vaccines targeting erythrocytic antigens.

Safety and effectiveness of antimalarial therapy in sickle cell disease: a systematic review and network meta-analysis

BACKGROUND

About 80% of all reported sickle cell disease (SCD) cases in children anually are recorded in Africa. Although malaria is considered a major cause of death in SCD children, there is limited data on the safety and effectiveness of the available antimalarial drugs used for prophylaxis. Also, previous systematic reviews have not provided quantitative measures of preventive effectiveness. The purpose of this research was to conduct a systematic review and meta-analysis of the available literature to determine the safety and effectiveness of antimalarial chemoprophylaxis used in SCD patients.

METHODS

We searched in PubMed, Medline, CINAHL, POPLine and Cochrane library, for the period spanning January 1990 to April 2018. We considered randomized or quasi-randomized controlled trials comparing any antimalarial chemoprophylaxis to, 1) other antimalarial chemoprophylaxis, 2) placebo or 3) no intervention, in SCD patients. Studies comparing at least two treatment arms, for a minimum duration of three months, with no restriction on the number of patients per arm were reviewed. The data were extracted and expressed as odds ratios. Direct pairwise comparisons were performed using fixed effect models and the heterogeneity assessed using the I-square.

RESULTS

Six qualified studies that highlighted the importance of antimalarial chemoprophylaxis in SCD children were identified. In total, seven different interventions (Chloroquine, Mefloquine, Mefloquine artesunate, Proguanil, Pyrimethamine, Sulfadoxine-pyrimethamine, Sulfadoxine-pyrimethamine amodiaquine) were evaluated in 912 children with SCD. Overall, the meta-analysis showed that antimalarial chemoprophylaxis provided protection against parasitemia and clinical malaria episodes in children with SCD. Nevertheless, the risk of hospitalization (OR = 0.72, 95% CI = 0.267-1.959; I2 = 0.0%), blood transfusion (OR = 0.83, 95% CI = 0.542-1.280; I2 = 29.733%), vaso-occlusive crisis (OR = 19, 95% CI = 1.713-2.792; I2 = 93.637%), and mortality (OR = 0.511, 95% CI = 0.189-1.384; I2 = 0.0%) did not differ between the intervention and placebo groups.

CONCLUSION

The data shows that antimalarial prophylaxis reduces the incidence of clinical malaria in children with SCD. However, there was no difference between the occurrence of adverse events in children who received placebo and those who received prophylaxis. This creates an urgent need to assess the efficacy of new antimalarial drug regimens as potential prophylactic agents in SCD patients.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42016052514).

Evaluation of the protective effect of a prime-boost strategy with plasmid DNA followed by recombinant adenovirus expressing BmAMA1 as vaccines against Babesia microti infection in hamster

In the present study, we have investigated the protective effect of a heterologous prime-boost strategy with priming plasmid DNA followed by recombinant adenovirus, both expressing BmAMA1, against Babesia microti infection. Four groups consisting of 3 hamsters per group were immunized with pBmAMA1/Ad5BmAMA1, pNull/Ad5BmAMA1, pBmAMA1/Ad5Null and pNull/Ad5Null, followed by challenge infection with B. microti. Our results showed that hamsters immunized with plasmid and adenovirus expressing BmAMA1 developed a robust IgG and IgG2a antibody response against BmAMA1, suggesting the DNA vaccine or viral vector vaccine tend to induce a Th1-biased response. Compared to the control hamsters, the hamsters vaccinated either with the prime-boost strategy or one of the two "vaccines" exhibited no significant protection against B. microti challenge. Although a slight difference in terms of parasitemia and hematocrit values at days 14-16 post challenge infection was observed, no other statistical difference was detected. Our results indicate that the prime-boost vaccination strategy of injection of plasmid and adenovirus expressing BmAMA1 is not efficient in protecting against B. microti infection.

Effectiveness of pregnant women's active participation in their antenatal care for the control of malaria and anaemia in pregnancy in Ghana: a cluster randomized controlled trial

BACKGROUND

The burden of malaria and anaemia in pregnancy remains high despite the availability of proven efficacious antenatal care interventions. Sub-optimal uptake of the interventions may be due to inadequate active participation of pregnant women in their antenatal care. It was hypothesized that providing opportunities for pregnant women to improve upon active participation in their antenatal care through malaria and anaemia point-of-care testing would improve adherence to ANC recommendations and interventions and lead to better pregnancy outcomes.

METHODS

Fourteen antenatal clinics in the Ashanti region of Ghana were randomized into intervention (pregnant women participating in their care plus current routine care) and control (current routine care) arms. Pregnant women attending the clinics for the first time were recruited and followed up until delivery. Haemoglobin levels and malaria parasitaemia were measured at baseline, 4-8 weeks after recruitment and at 36-40 weeks gestation. Birth weight and pregnancy outcomes were also recorded.

RESULTS

The overall mean age, gestational age and haemoglobin at baseline were 26.4 years, 17.3 weeks and 110 g/l, respectively, with no significant differences between groups; 10.7% had asymptomatic parasitaemia; 74.6% owned an ITN but only 48.8% slept under it the night before enrolment. The adjusted risk ratio by 8 weeks follow up and at 36-40 weeks gestation in the intervention versus the control was 0.97 (95% CI 0.78-1.22) and 0.92 (95% CI 0.63-1.34) for anaemia and 1.17 (95% CI 0.68-2.04) and 0.83 (95% CI 0.27-2.57) for parasitaemia. The adjusted risk ratio for low birth weight was 0.93 (95% CI 0.44-1.97) and for pregnancy complications (abortions, intrauterine fetal deaths and still births) was 0.77 (95% CI 0.17-3.52) in the intervention group versus controls.

CONCLUSION

Although its potential was evident, this study found no significant beneficial effect of women participating in their malaria and haemoglobin tests on pregnancy outcomes. Exploring factors influencing health worker compliance to health intervention implementation and patient adherence to health interventions within this context will contribute in future to improving intervention effectiveness. Trial registration ISRTCTN88917252.

Immunization with AgTRIO, a Protein in Anopheles Saliva, Contributes to Protection against Plasmodium Infection in Mice

Plasmodium infection begins with the bite of an anopheline mosquito, when sporozoites along with saliva are injected into a vertebrate host. The role of the host responses to mosquito saliva components in malaria remains unclear. We observed that antisera against Anopheles gambiae salivary glands partially protected mice from mosquito-borne Plasmodium infection. Specifically, antibodies to A. gambiae TRIO (AgTRIO), a mosquito salivary gland antigen, contributed to the protection. Mice administered AgTRIO antiserum showed lower Plasmodium liver burden and decreased parasitemia when exposed to infected mosquitoes. Active immunization with AgTRIO was also partially protective against Plasmodium berghei infection. A combination of AgTRIO antiserum and antibodies against Plasmodium circumsporozoite protein, a vaccine candidate, further decreased P. berghei infection. In humanized mice, AgTRIO antiserum afforded some protection against mosquito-transmitted Plasmodium falciparum. AgTRIO antiserum reduced the movement of sporozoites in the murine dermis. AgTRIO may serve as an arthropod-based target against Plasmodium to combat malaria.

Doxycycline inhibits experimental cerebral malaria by reducing inflammatory immune reactions and tissue-degrading mediators

Malaria ranks among the most important infectious diseases worldwide and affects mostly people living in tropical countries. Mechanisms involved in disease progression are still not fully understood and specific treatments that might interfere with cerebral malaria (CM) are limited. Here we show that administration of doxycycline (DOX) prevented experimental CM (ECM) in Plasmodium berghei ANKA (PbA)-infected C57BL/6 wildtype (WT) mice in an IL-10-independent manner. DOX-treated mice showed an intact blood-brain barrier (BBB) and attenuated brain inflammation. Importantly, if WT mice were infected with a 20-fold increased parasite load, they could be still protected from ECM if they received DOX from day 4-6 post infection, despite similar parasitemia compared to control-infected mice that did not receive DOX and developed ECM. Infiltration of T cells and cytotoxic responses were reduced in brains of DOX-treated mice. Analysis of brain tissue by RNA-array revealed reduced expression of chemokines and tumour necrosis factor (TNF) in brains of DOX-treated mice. Furthermore, DOX-administration resulted in brains of the mice in reduced expression of matrix metalloproteinase 2 (MMP2) and granzyme B, which are both factors associated with ECM pathology. Systemic interferon gamma production was reduced and activated peripheral T cells accumulated in the spleen in DOX-treated mice. Our results suggest that DOX targeted inflammatory processes in the central nervous system (CNS) and prevented ECM by impaired brain access of effector T cells in addition to its anti-parasitic effect, thereby expanding the understanding of molecular events that underlie DOX-mediated therapeutic interventions.

The contribution of malaria control interventions on spatio-temporal changes of parasitaemia risk in Uganda during 2009-2014

BACKGROUND

In Uganda, malaria vector control interventions and case management with Artemisinin Combination Therapies (ACTs) have been scaled up over the last few years as a result of increased funding. Data on parasitaemia prevalence among children less than 5 years old and coverage of interventions was collected during the first two Malaria Indicator Surveys (MIS) conducted in 2009 and 2014, respectively. In this study, we quantify the effects of control interventions on parasitaemia risk changes between the two MIS in a spatio-temporal analysis.

METHODS

Bayesian geostatistical and temporal models were fitted on the MIS data of 2009 and 2014. The models took into account geographical misalignment in the locations of the two surveys and adjusted for climatic changes and socio-economic differentials. Parasitaemia risk was predicted over a 2 × 2 km2 grid and the number of infected children less than 5 years old was estimated. Geostatistical variable selection was applied to identify the most important ITN coverage indicators. A spatially varying coefficient model was used to estimate intervention effects at sub-national level.

RESULTS

The coverage of Insecticide Treated Nets (ITNs) and ACTs more than doubled at country and sub-national levels during the period 2009-2014. The coverage of Indoor Residual Spraying (IRS) remained static at all levels. ITNs, IRS, and ACTs were associated with a reduction in parasitaemia odds of 19% (95% BCI: 18-29%), 78% (95% BCI: 67-84%), and 34% (95% BCI: 28-66%), respectively. Intervention effects varied with region. Higher socio-economic status and living in urban areas were associated with parasitaemia odds reduction of 46% (95% BCI: 0.51-0.57) and 57% (95% BCI: 0.40-0.53), respectively. The probability of parasitaemia risk decline in the country was 85% and varied from 70% in the North-East region to 100% in Kampala region. The estimated number of children infected with malaria declined from 2,480,373 in 2009 to 825,636 in 2014.

CONCLUSIONS

Interventions have had a strong effect on the decline of parasitaemia risk in Uganda during 2009-2014, albeit with varying magnitude in the regions. This success should be sustained by optimizing ITN coverage to achieve universal coverage.

Malaria Control Interventions Contributed to Declines in Malaria Parasitemia, Severe Anemia, and All-Cause Mortality in Children Less Than 5 Years of Age in Malawi, 2000-2010

Malaria control intervention coverage increased nationwide in Malawi during 2000-2010. Trends in intervention coverage were assessed against trends in malaria parasite prevalence, severe anemia (hemoglobin < 8 g/dL), and all-cause mortality in children under 5 years of age (ACCM) using nationally representative household surveys. Associations between insecticide-treated net (ITN) ownership, malaria morbidity, and ACCM were also assessed. Household ITN ownership increased from 27.4% (95% confidence interval [CI] = 25.9-29.0) in 2004 to 56.8% (95% CI = 55.6-58.1) in 2010. Similarly intermittent preventive treatment during pregnancy coverage increased from 28.2% (95% CI = 26.7-29.8) in 2000 to 55.0% (95% CI = 53.4-56.6) in 2010. Malaria parasite prevalence decreased significantly from 60.5% (95% CI = 53.0-68.0) in 2001 to 20.4% (95% CI = 15.7-25.1) in 2009 in children aged 6-35 months. Severe anemia prevalence decreased from 20.4% (95% CI: 17.3-24.0) in 2004 to 13.1% (95% CI = 11.0-15.4) in 2010 in children aged 6-23 months. ACCM decreased 41%, from 188.6 deaths per 1,000 live births (95% CI = 179.1-198.0) during 1996-2000, to 112.1 deaths per 1,000 live births (95% CI = 105.8-118.5) during 2006-2010. When controlling for other covariates in random effects logistic regression models, household ITN ownership was protective against malaria parasitemia in children (odds ratio [OR] = 0.81, 95% CI = 0.72-0.92) and severe anemia (OR = 0.82, 95% CI = 0.72-0.94). After considering the magnitude of changes in malaria intervention coverage and nonmalaria factors, and given the contribution of malaria to all-cause mortality in malaria-endemic countries, the substantial increase in malaria control interventions likely improved child survival in Malawi during 2000-2010.

Providing lipid-based nutrient supplement during pregnancy does not reduce the risk of maternal P falciparum parasitaemia and reproductive tract infections: a randomised controlled trial

BACKGROUND

Maternal infections are associated with maternal and foetal adverse outcomes. Nutrient supplementation during pregnancy may reduce the occurrence of infections by improving maternal immunity. We aimed to investigate the impact of small-quantity lipid-based nutrient supplement (SQ-LNS) on the occurrence of Plasmodium falciparum parasitaemia during pregnancy and trichomoniasis, vaginal candidiasis and urinary tract infection (UTI) after delivery.

METHODS

Pregnant Malawian women enrolled in the iLiNS-DYAD trial receiving daily supplementation with SQ-LNS, multiple micronutrients (MMN) or iron & folic acid (IFA) from <20 gestation weeks (gw) were assessed for P. falciparum parasitaemia at 32 gw using rapid diagnostic testing (RDT), at 36 gw using polymerase chain reaction (PCR) and at delivery using both RDT and PCR; and at one week after delivery for trichomoniasis and vaginal candidiasis using wet mount microscopy and for UTI using urine dipstick analysis. The prevalence of each infection by intervention group was estimated at the prescribed time points and the global null hypothesis was tested using logistic regression. Adjusted analyses were performed using preselected covariates.

RESULTS

The prevalence of P. falciparum parasitaemia was 10.7% at 32 gw, 9% at 36 gw, and 8.3% by RDT and 20.2% by PCR at delivery. After delivery the prevalence of trichomoniasis was 10.5%, vaginal candidiasis was 0.5%, and UTI was 3.1%. There were no differences between intervention groups in the prevalence of any of the infections.

CONCLUSION

In this population, SQ-LNS did not influence the occurrence of maternal P. falciparum parasitaemia, trichomoniasis, vaginal candidiasis or UTI.

TRIAL REGISTRATION

Identifier: NCT01239693 (10 November 2010).

Efficacy and safety of intermittent preventive treatment in schoolchildren with sulfadoxine/pyrimethamine (SP) and SP plus piperaquine in Democratic Republic of the Congo: a randomised controlled trial

In endemic areas, malaria and its adverse effects in schoolchildren may be prevented by intermittent preventive treatment (IPTsc). However, the most appropriate drug regimen for IPTsc remains to be identified. A randomised controlled trial was conducted in Kinshasa, DRC. Enrolled schoolchildren were assigned to a passive control arm (n = 212), sulfadoxine/pyrimethamine (SP) (n = 202) or SP plus piperaquine (SP/PQ) (n = 202). The primary endpoint was haemoglobin (Hb) change. Secondary endpoints were anaemia, parasitaemia prevalence and clinical malaria incidence. Data were analysed by modified intention-to-treat (mITT) and per-protocol. A linear mixed mode was used due to repeated measurements. Of 616 enrolled children, 410 (66.6%) were eligible for mITT analysis. The control arm was used as reference. After 12 months, the Hb level increased by 0.20 g/dL (95% CI -0.61 to 0.47; P = 0.168) and 0.39 g/dL (0.12-0.66; P <0.01) in the SP and SP/PQ arms, respectively. SP treatment reduced anaemia, malaria parasitaemia and clinical malaria by 10% (0-20%; P = 0.06), 19% (2-33%; P = 0.042) and 25% (-32 to 57%; P = 0.37), respectively. The corresponding values for SP/PQ were 28% (19-37%; P <0.001), 40% (26-52%; P <0.001) and 58% (17-79%; P <0.01). No deaths or severe adverse events (SAEs) were observed. SP/PQ offered substantial protection against anaemia, malaria parasitaemia and clinical malaria and showed no SAEs. SP/PQ, a combination of two long-acting non-artemisinin-based antimalarials, may be a valuable option for IPTsc in Africa.

THERAPEUTIC POTENTIALS OF ETHANOLIC EXTRACT OF LEAVES OF HOLARRHENA FLORIBUNDA (G. DON) DUR. AND SCHINZ (APOCYNACEAE)

BACKGROUND

Holarrhena floribunda is a plant of wide usage in the Togolese folk medicine. A previous ethnobotanical survey on the latex plants of the Maritime region of the country revealed that this plant was included in several recipes curing malaria and microbial infections. Therefore, this study aimed to seek for the effectiveness of the ethanolic extract of the plant in the treatment of these diseases.

METHODS

The antimicrobial test was performed using the agar well-diffusion and the NCCLS broth microdilution methods, while the in vivo antimalarial activity was evaluated following the four-day suppressive test of Peters. The acute toxic effects of the extract were monitored after a single oral dose (5,000 mg/kg body weight) administration in NMRI mice.

RESULTS

The results indicated that the ethanolic extract of leaves of H. floribunda was active on Staphylococcus aureus ATCC 29213 and clinical strains of Staphylococcus aureus, Salmonella typhi and Klebsiella pneumoniae with MICs ranging from 0.62 to 1.25 mg/mL. The extract also showed significant parasitaemia suppression in a dose-dependent manner. In the acute toxicity assay, the oral administration of the extract to the mice did not affect the relative weight of vital organs, and there were no signs of toxicity or death during the study period. The LD50 of the tested extract was found to be greater than 5,000 mg/kg, indicating its safety.

CONCLUSION

This study demonstrates the antibacterial and antimalarial activities of leaves of H. floribunda and then, supports its medicinal use in the treatment of microbial infections.

Protection against malaria at 1 year and immune correlates following PfSPZ vaccination

An attenuated Plasmodium falciparum (Pf) sporozoite (SPZ) vaccine, PfSPZ Vaccine, is highly protective against controlled human malaria infection (CHMI) 3 weeks after immunization, but the durability of protection is unknown. We assessed how vaccine dosage, regimen, and route of administration affected durable protection in malaria-naive adults. After four intravenous immunizations with 2.7 × 10(5) PfSPZ, 6/11 (55%) vaccinated subjects remained without parasitemia following CHMI 21 weeks after immunization. Five non-parasitemic subjects from this dosage group underwent repeat CHMI at 59 weeks, and none developed parasitemia. Although Pf-specific serum antibody levels correlated with protection up to 21-25 weeks after immunization, antibody levels waned substantially by 59 weeks. Pf-specific T cell responses also declined in blood by 59 weeks. To determine whether T cell responses in blood reflected responses in liver, we vaccinated nonhuman primates with PfSPZ Vaccine. Pf-specific interferon-γ-producing CD8 T cells were present at ∼100-fold higher frequencies in liver than in blood. Our findings suggest that PfSPZ Vaccine conferred durable protection to malaria through long-lived tissue-resident T cells and that administration of higher doses may further enhance protection.

Assessing the effects of malaria interventions on the geographical distribution of parasitaemia risk in Burkina Faso

BACKGROUND

Burkina Faso conducted its first nationally representative household malaria survey in 2010/2011. The survey collected among others, information on malaria interventions, treatment choices and malaria parasite prevalence in children aged 6-59 months.

METHODS

In this study, Bayesian geostatistical models were employed to assess the effects of health interventions related to insecticide-treated bed nets (ITN), indoor residual spray (IRS), artemisinin-based combination therapy (ACT) coverage associated with childhood malaria parasite risk at national and sub-national level, after taking into account geographical disparities of climatic/environmental and socio-economic factors. Several ITN coverage measures were calculated and Bayesian variable selection was used to identify the most important ones. Parasitaemia risk depicting spatial patterns of infections were estimated.

RESULTS

The results show that the predicted population-adjusted parasitaemia risk ranges from 4.04 % in Kadiogo province to 82 % in Kompienga province. The effect of ITN coverage was not important at national level; however ITNs have an important protective effect in Ouagadougou as well as in three districts in the western part of the country with high parasitaemia prevalence and low to moderate coverage. There is a large variation in ACT coverage between the districts. Although at national level the ACT effects on parasitaemia risk was not important, at sub-national level 18 districts around Ouagadougou deliver effective treatment.

CONCLUSION

The produced maps show great variations in parasitaemia risk across the country and identify the districts where interventions are being effective. These outputs are valuable tools that can help improve malaria control in Burkina Faso.

Pre-infection administration of asiatic acid retards parasitaemia induction in Plasmodium berghei murine malaria infected Sprague-Dawley rats

BACKGROUND

Malaria prevention has remained a critical area in the absence of efficacious vaccines against malaria. Drugs currently used as chemotherapeutics are also used in chemoprophylaxis increasing possible drug resistance. Asiatic acid is a natural phytochemical with oxidant, antioxidant and anti-inflammatory properties with emerging anti-malarial potential. The influence of asiatic acid administration prior to Plasmodium berghei infection of Sprague-Dawley rats on parasitaemia induction is here reported.

METHODS

Sprague-Dawley rats (90-120 g) were administered with asiatic acid (10 mg/kg) 48 h before intraperitoneal infection with P. berghei. Parasitaemia induction and progression, food and water intake as well as weight were compared to 30 mg/kg chloroquine-treated and infected control rats during sub-chronic studies (21 days).

RESULTS

Asiatic acid pre-infection administration preserved food and water intake as well as increase in percentage weight gain of infected animals. In pre-infection treated animals, the pre-patent period was extended to day 6 from 72 h. Asiatic acid suppressed parasitaemia while oral chloroquine (30 mg/kg) did not influence malaria induction.

CONCLUSIONS

Per-oral, pre-infection, asiatic acid administration influenced parasitaemia patency and parasitaemia progression, food, water, and weight gain percentage. This may suggest possible chemoprophylaxis effects of asiatic acid in malaria.

Monthly sulphadoxine-pyrimethamine combination versus daily proguanil for malaria chemoprophylaxis in sickle cell disease: a randomized controlled study at the Jos University Teaching Hospital

BACKGROUND

Malaria carries a high case fatality among patients with sickle cell disease. In Jos University Teaching Hospital, at the time of this study, the use of Proguanil was the acceptable mode of chemoprophylaxis for preventing malaria in these patients. Intermittent Preventive Treatment (IPT) with Sulphadoxine-Pyrimethamine [SP] has shown great potential for reducing the prevalence of malaria and anaemia among pregnant women, infants and travellers. We hypothesised that monthly SP was superior to daily Proguanil in reducing malaria parasitaemia, clinical malaria attacks and sickle cell crises in such patients.

OBJECTIVE

To assess the efficacy and affordability of monthly SP versus daily Proguanil for malaria chemoprophylaxis in patients attending Sickle Cell Clinic at Jos University Teaching Hospital, Plateau State, Nigeria.

METHODS

One hundred and fifty four patients [114 children and 40 adults] with Sickle Cell Disease in their steady state were randomized to monthly SP or daily Proguanil for malaria chemoprophylaxis. Active detection of malaria parasite in the peripheral blood and packed cell volumes were done at each monthly visit to the clinic over a period of three months. The primary outcome measure was the proportion of patients with malaria parasite in the peripheral blood at the end of 3 months. The secondary outcome measures included episodes of clinical malaria attacks, frequency and type of sickle cell crises and adverse effects of the medication.

RESULTS

Ninety four percent [72/77] of patients in the SP group and 91% [70/77] in the Proguanil group respectively completed three months of follow up. SP reduced the prevalence of malaria parasitaemia by 25% [(14%) 10/72] compared to 6.4% [(30%) 21/70] in the proguanil group. [X2 54; p = 0.01]. Seventeen percent [12/72] of the patients receiving monthly SP had malaria attacks compared to 57% [40/70] on prophylaxis with Proguanil. [X2 =25; p< 0.0003]. Thirty three percent [24/72] of the patients receiving SP had at least an episode of bone pain crises compared to 69% [48/70] of the patients receiving Proguanil. [X2 =17.6; p<0.0001]. SP was 8 times cheaper than Proguanil.

CONCLUSION

Monthly chemoprophylaxis with SP was more efficacious than daily Proguanil in reducing the prevalence of asymptomatic malaria parasitaemia, clinical malaria attack and sickle cell crises in patients with sickle cell disease. SP was 8 times cheaper than Proguanil. No significant side effect was recorded in both groups. The current practice of routinely prescribing daily Proguanil to SCD patients for malaria chemoprophylaxis needs to be reviewed.

Current concepts in the prevention of pathogen transmission via blood/plasma-derived products for bleeding disorders

The pathogen safety of blood/plasma-derived products has historically been a subject of significant concern to the medical community. Measures such as donor selection and blood screening have contributed to increase the safety of these products, but pathogen transmission does still occur. Reasons for this include lack of sensitivity/specificity of current screening methods, lack of reliable screening tests for some pathogens (e.g. prions) and the fact that many potentially harmful infectious agents are not routinely screened for. Methods for the purification/inactivation of blood/plasma-derived products have been developed in order to further reduce the residual risk, but low concentrations of pathogens do not necessarily imply a low level of risk for the patient and so the overall challenge of minimising risk remains. This review aims to discuss the variable level of pathogenic risk and describes the current screening methods used to prevent/detect the presence of pathogens in blood/plasma-derived products.

Coadministration of cruzipain and GM-CSF DNAs, a new immunotherapeutic vaccine against Trypanosoma cruzi infection

Therapeutic vaccine research and development are especially important in Chagas disease considering the characteristics of the chronic infection and the number of people in the Americas living with a parasite infection for decades. We have previously reported the efficacy of attenuated Salmonella enterica (S) carrying plasmid encoding cruzipain (SCz) to protect against Trypanosoma cruzi infection. In the present work we investigated whether Cz DNA vaccine immunotherapy could be effective in controlling an ongoing T. cruzi infection in mice. We here report the intramuscular administration of naked Cz DNA or the oral administration of Salmonella as Cz DNA delivery system as therapeutic vaccines in mice during acute or chronic infection. The coadministration of a plasmid encoding GM-CSF improved vaccine performance, indicating that the stimulation of innate immune cells is needed in the event of an ongoing infection. These therapeutic vaccines were able to address the response to a protective and sustained Th1 biased profile not only against Cz but also against a variety of parasite antigens. The combined therapeutic vaccine during the chronic phase of infection prevents tissue pathology as shown by a reduced level of enzyme activity characteristic of tissue damage and a tissue status compatible with normal tissue. The obtained results suggest that immunotherapy with Cz and GM-CSF DNAs, either alone or in combination with other drug treatments, may represent a promising alternative for Chagas disease therapy.

VEGF and LPS synergistically silence inflammatory response to Plasmodium berghei infection and protect against cerebral malaria

Malaria infection induces, alongside endothelial damage and obstruction hypoxia, a potent inflammatory response similar to that observed in other systemic diseases caused by bacteria and viruses. Accordingly, it is increasingly recognised that cerebral malaria (CM), the most severe and life threatening complication of Plasmodium falciparum infection, bears a number of similarities with sepsis, an often fatal condition associated with a misregulated inflammatory response triggered by systemic microbial infections. Using a Plasmodium berghei ANKA mouse model, histology, immunohistochemistry and gene expression analysis, we showed that lipopolysaccharide S (LPS), at doses that normally induce inflammation tolerance, protects P. berghei infected mice against experimental CM (ECM). Vascular endothelial growth factor (VEGF) preserved blood vessel integrity, and the combination with LPS resulted in a strong synergistic effect. Treated mice did not develop ECM, showed a prolonged survival and failed to develop a significant inflammatory response and splenomegaly in spite of normal parasite loads. The protective role of VEGF was further confirmed by the observation that the treatment of P. berghei infected C57BL/6 and Balb/c mice with the VEGF receptor inhibitor axitinib exacerbates cerebral pathology and aggravates the course of infection. Infected mice treated with VEGF and LPS showed an induction of the anti-inflammatory genes Nrf2 and HO-1 and a suppression to basal levels of the genes IFN-γ and TNF-α. These results provide the rationale for developing new therapeutic approaches against CM and shed new light on how the inflammatory process can be modulated in the presence of systemic infectious diseases.

Angiotensin II Moderately Decreases Plasmodium Infection and Experimental Cerebral Malaria in Mice

Angiotensin II, a peptide hormone that regulates blood pressure, has been proposed as a protective factor against cerebral malaria based on a genetic analysis. In vitro studies have documented an inhibitory effect of angiotensin II on Plasmodium growth, while studies using chemical inhibitors of angiotensin II in mice showed protection against experimental cerebral malaria but not major effects on parasite growth. To determine whether the level of angiotensin II affects Plasmodium growth and/or disease outcome in malaria, elevated levels of angiotensin II were induced in mice by intradermal implantation of osmotic mini-pumps providing constant release of this hormone. Mice were then infected with P. berghei and monitored for parasitemia and incidence of cerebral malaria. Mice infused with angiotensin II showed decreased parasitemia seven days after infection. The development of experimental cerebral malaria was delayed and a moderate increase in survival was observed in mice with elevated angiotensin II, as confirmed by decreased number of cerebral hemorrhages compared to controls. The results presented here show for the first time the effect of elevated levels of angiotensin II in an in vivo model of malaria. The decreased pathogenesis observed in mice complements a previous human genetic study, reinforcing the hypothesis of a beneficial effect of angiotensin II in malaria.

Recombinant scorpine produced using SUMO fusion partner in Escherichia coli has the activities against clinically isolated bacteria and inhibits the Plasmodium falciparum parasitemia in vitro

Scorpine, a small cationic peptide from the venom of Pandinus imperator, which has been shown to have anti-bacterial and anti-plasmodial activities, has potential important applications in the pharmaceutical industries. However, the isolation of scorpine from natural sources is inefficient and time-consuming. Here, we first report the expression and purification of recombinant scorpine in Escherichia coli, using small ubiquitin-related modifier (SUMO) fusion partner. The fusion protein was expressed in soluble form in E. coli, and expression was verified by SDS-PAGE and western blotting analysis. The fusion protein was purified to 90% purity by nickel-nitrilotriacetic acid (Ni2+-NTA) resin chromatography. After the SUMO-scorpine fusion protein was cleaved by the SUMO protease, the cleaved sample was reapplied to a Ni2+-NTA column. Tricine/SDS-PAGE gel results indicated that Scorpine had been purified successfully to more than 95% purity. The recombinantly expressed Scorpine showed anti-bacterial activity against two standard bacteria including Staphylococcus aureus ATCC 29213 and Acinetobacter baumannii ATCC 19606, and clinically isolated bacteria including S. aureus S, S. aureus R, A. baumannii S, and A. baumannii R. It also produced 100% reduction in Plasmodium falciparum parasitemia in vitro. Thus, the expression strategy presented in this study allowed convenient high yield and easy purification of recombinant Scorpine for pharmaceutical applications in the future.

From genome screening to creation of vaccine against Trypanosoma cruzi by use of immunoinformatics

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi, and activation of CD8(+) T cells is crucial for a protective immune response. Therefore, the identification of antigens with major histocompatibility complex class I epitopes is a crucial step for vaccine development against T. cruzi. Our aim was to identify novel antigens and epitopes by immunoinformatics analysis of the parasite proteome (12 969 proteins) and to validate their immunotherapeutic potential in infected mice. We identified 172 predicted epitopes, using NetMHC and RANKPEP. The corresponding protein sequences were reanalyzed to generate a consensus prediction, and 26 epitopes were selected for in vivo validation. The interferon γ (IFN-γ) recall response of splenocytes from T. cruzi-infected mice confirmed that 10 of 26 epitopes (38%) induced IFN-γ production. The immunotherapeutic potential of a mixture of all 10 peptides was evaluated in infected mice. The therapeutic vaccine was able to control T. cruzi infection, as evidenced by reduced parasitemia, cardiac tissue inflammation, and parasite burden and increased survival. These findings illustrate the benefits of this approach for the rapid development of a vaccine against pathogens with large genomes. The identified peptides and the proteins from which they are derived are excellent candidates for the development of a vaccine against T. cruzi.

Submicroscopic malaria infection during pregnancy and the impact of intermittent preventive treatment

BACKGROUND

Malaria during pregnancy results in adverse outcomes for mothers and infants. Intermittent preventive treatment (IPT) with sulphadoxine-pyrimethamine (SP) is the primary intervention aimed at reducing malaria infection during pregnancy. Although submicroscopic infection is common during pregnancy and at delivery, its impact throughout pregnancy on the development of placental malaria and adverse pregnancy outcomes has not been clearly established.

METHODS

Quantitative PCR was used to detect submicroscopic infections in pregnant women enrolled in an observational study in Blantyre, Malawi to determine their effect on maternal, foetal and placental outcomes. The ability of SP to treat and prevent submicroscopic infections was also assessed.

RESULTS

2,681 samples from 448 women were analysed and 95 submicroscopic infections were detected in 68 women, a rate of 0.6 episodes per person-year of follow-up. Submicroscopic infections were most often detected at enrolment. The majority of women with submicroscopic infections did not have a microscopically detectable infection detected during pregnancy. Submicroscopic infection was associated with placental malaria even after controlling for microscopically detectable infection and was associated with decreased maternal haemoglobin at the time of detection. However, submicroscopic infection was not associated with adverse maternal or foetal outcomes at delivery. One-third of women with evidence of placental malaria did not have documented peripheral infection during pregnancy. SP was moderately effective in treating submicroscopic infections, but did not prevent the development of new submicroscopic infections in the month after administration.

CONCLUSIONS

Submicroscopic malaria infection is common and occurs early in pregnancy. SP-IPT can clear some submicroscopic infections but does not prevent new infections after administration. To effectively control pregnancy-associated malaria, new interventions are required to target women prior to their first antenatal care visit and to effectively treat and prevent all malaria infections.

Protective efficacy of Babesia gibsoni culture-derived exoantigens against the challenge infection in dogs

The aim of this study is to determine the efficacy of exoantigens derived from Babesia gibsoni cultures to induce protective immunity against challenge exposure of virulent organisms. An attenuated B. gibsoni Oita strain was maintained in vitro by the microaerophilus stationary phase (MASP) method, and exoantigens-containing supernatant fluids were collected for preparation of the immunization. Two dogs received three subcutaneous immunizations with a 20-day interval of B. gibsoni exoantigens plus 0.5 mg saponin (Quil A). On day 68 after the prime immunization, the immunized dogs and control dogs were challenged intravenously with 2 × 10(8) virulent parasites of a homologous B. gibsoni strain. The results showed that exoantigens could induce a high degree of protection against virulent homologous challenge exposure. Two dogs immunized with exoantigens showed a lower parasitemia, accompanied by a slight decrease in the PCV that returned to normal values. Control dogs developed typical acute clinical signs, including severe anemia and hyperthermia. The immunization elicited humoral immune responses. In dogs immunized with exoantigens, the maximum antibody titer was 2,560 and 5,120 by indirect fluorescent antibody test (IFAT), respectively. Preliminary Western blot analysis of the immunogen revealed five dominant proteins of molecular weights of 18, 37, 43, 50, and 57 kDa. These results suggested that the culture-derived exoantigens were candidates for non-viable vaccine.

Impact of intermittent screening and treatment for malaria among school children in Kenya: a cluster randomised trial

BACKGROUND

Improving the health of school-aged children can yield substantial benefits for cognitive development and educational achievement. However, there is limited experimental evidence of the benefits of alternative school-based malaria interventions or how the impacts of interventions vary according to intensity of malaria transmission. We investigated the effect of intermittent screening and treatment (IST) for malaria on the health and education of school children in an area of low to moderate malaria transmission.

METHODS AND FINDINGS

A cluster randomised trial was implemented with 5,233 children in 101 government primary schools on the south coast of Kenya in 2010-2012. The intervention was delivered to children randomly selected from classes 1 and 5 who were followed up for 24 months. Once a school term, children were screened by public health workers using malaria rapid diagnostic tests (RDTs), and children (with or without malaria symptoms) found to be RDT-positive were treated with a six dose regimen of artemether-lumefantrine (AL). Given the nature of the intervention, the trial was not blinded. The primary outcomes were anaemia and sustained attention. Secondary outcomes were malaria parasitaemia and educational achievement. Data were analysed on an intention-to-treat basis. During the intervention period, an average of 88.3% children in intervention schools were screened at each round, of whom 17.5% were RDT-positive. 80.3% of children in the control and 80.2% in the intervention group were followed-up at 24 months. No impact of the malaria IST intervention was observed for prevalence of anaemia at either 12 or 24 months (adjusted risk ratio [Adj.RR]: 1.03, 95% CI 0.93-1.13, p = 0.621 and Adj.RR: 1.00, 95% CI 0.90-1.11, p = 0.953) respectively, or on prevalence of P. falciparum infection or scores of classroom attention. No effect of IST was observed on educational achievement in the older class, but an apparent negative effect was seen on spelling scores in the younger class at 9 and 24 months and on arithmetic scores at 24 months.

CONCLUSION

In this setting in Kenya, IST as implemented in this study is not effective in improving the health or education of school children. Possible reasons for the absence of an impact are the marked geographical heterogeneity in transmission, the rapid rate of reinfection following AL treatment, the variable reliability of RDTs, and the relative contribution of malaria to the aetiology of anaemia in this setting.

TRIAL REGISTRATION

www.ClinicalTrials.gov NCT00878007.

MALARIA PARASITAEMIA AMONG FEBRILE CHILDREN INFECTED WITH HUMAN IMMUNODEFICIENCY VIRUS IN THE CONTEXT OF PROPHYLACTIC COTRIMOXAZOLE AS STANDARD OF CARE: A CROSS- SECTIONAL SURVEY IN WESTERN KENYA

OBJECTIVE

To document the prevalence of malaria parasitaemia among the HIV infected febrile children in a malaria endemic area.

DESIGN

A cross-sectional study.

SETTING

An ambulatory paediatric HIV clinic in Western Kenya, between November 2011 and December 2012.

SUBJECTS

A total of 245 febrile HIV infected children aged less than 14 years attending the HIV clinic in the Webuye level IV hospital were included in the study. A systematic sampling method was used.

MAIN OUTCOMES

A blood sample was taken for malaria parasite testing. Presence or absence of malaria parasites was documented. Clinical and socio-demographic characteristics of the participants were also recorded.

RESULTS

A total of 245 participants were recruited mean age being 5.53 years. Malaria prevalence was 81.9%. Most participants (97%) were on cotrimoxazole prophylaxis. Some of the factors found to be positively associated with malaria parasitaemia were; male sex, care taker category (parent), WHO stage 3 and 4 of HIV disease, and a high absolute CD4 count. However, only the caretaker association was statistically significant.

CONCLUSION

The frequency of malaria parasitaemia among febrile HIV infected children is still high regardless of the high cotrimoxazole prophylaxis uptake. It is also noted that there is a shift in the age group of fever among children toward the older age group. This implies that policies may need to be relooked at to include the older age group in the aggressive malaria prevention measures to avoid losing on the already made gains.

The chemotherapy of rodent malaria. LXII. Drug combinations to impede the selection of drug resistance, part 5: rates of development of resistance to some inhibitors of folate metabolism and to artesunate

In recent years infection with chloroquine-resistant Plasmodium falciparum has been combatted with two long-acting antimalarials, pyrimethamine and sulfadoxine, in the combination known as Fansidar that exerts a strong, synergistic action on the asexual stages of the parasite. This second-line regimen, however, is failing increasingly because of the selection of resistant clones in endemic areas, and effective, safe, alternative drugs or drug combinations that are also affordable are urgently needed. Antimalarial drugs with shorter half-lives than those of pyrimethamine or sulfadoxine are likely to be slower to select resistant parasites. In the experiments reported here, the baseline in-vivo responses of rodent malarial parasites to chlorproguanil and proguanil and their active metabolites, chlorcycloguanil and cycloguanil, as well as those to dapsone and artesunate, were explored. In general, the most sensitive parasite to all of these compounds was P. chabaudi. When the drugs were used, individually, to select resistance via the '2%-relapse technique', relatively stable resistance to each was obtained in P. chabaudi as well as in P. berghei and P. yoelii ssp. NS, the last of these being also highly resistant to chloroquine. Of most concern was the rapidity and high level of resistance developed by P. chabaudi to artesunate. The experiments also validated the use of chlorcycloguanil or cycloguanil as surrogates for chlorproguanil or proguanil. Further studies to investigate the possible value of administering chlorproguanil-dapsone, with or without artesunate, are under way and will be reported separately.

Gametocyte dynamics and the role of drugs in reducing the transmission potential of Plasmodium vivax

BACKGROUND

Designing interventions that will reduce transmission of vivax malaria requires knowledge of Plasmodium vivax gametocyte dynamics.

METHODS

We analyzed data from a randomized controlled trial in northwestern Thailand and 2 trials in Papua, Indonesia, to identify and compare risk factors for vivax gametocytemia at enrollment and following treatment.

RESULTS

A total of 492 patients with P. vivax infections from Thailand and 476 patients (162 with concurrent falciparum parasitemia) from Indonesia were evaluable. Also, 84.3% (415/492) and 66.6% (209/314) of patients with monoinfection were gametocytemic at enrollment, respectively. The ratio of gametocytemia to asexual parasitemia did not differ between acute and recurrent infections (P = .48 in Thailand, P = .08 in Indonesia). High asexual parasitemia was associated with an increased risk of gametocytemia during follow-up in both locations. In Thailand, the cumulative incidence of gametocytemia between day 7 and day 42 following dihydroartemisinin + piperaquine (DHA + PIP) was 6.92% vs 29.1% following chloroquine (P < .001). In Indonesia, the incidence of gametocytemia was 33.6% following artesunate + amodiaquine (AS + AQ), 7.42% following artemether + lumefantrine, and 6.80% following DHA + PIP (P < .001 for DHA + PIP vs AS + AQ).

CONCLUSIONS

P. vivax gametocyte carriage mirrors asexual-stage infection. Prevention of relapses, particularly in those with high asexual parasitemia, is likely the most important strategy for interrupting P. vivax transmission.

Insights into the preclinical treatment of blood-stage malaria by the antibiotic borrelidin

BACKGROUND AND PURPOSE

Blood-stage Plasmodium parasites cause morbidity and mortality from malaria. Parasite resistance to drugs makes development of new chemotherapies an urgency. Aminoacyl-tRNA synthetases have been validated as antimalarial drug targets. We explored long-term effects of borrelidin and mupirocin in lethal P. yoelii murine malaria.

EXPERIMENTAL APPROACH

Long-term (up to 340 days) immunological responses to borrelidin or mupirocin were measured after an initial 4 day suppressive test. Prophylaxis and cure were evaluated and the inhibitory effect on the parasites analysed.

KEY RESULTS

Borrelidin protected against lethal malaria at 0.25 mg·kg⁻¹·day⁻¹. Antimalarial activity of borrelidin correlated with accumulation of trophozoites in peripheral blood. All infected mice treated with borrelidin survived and subsequently developed immunity protecting them from re-infection on further challenges, 75 and 340 days after the initial infection. This long-term immunity in borrelidin-treated mice resulted in negligible parasitaemia after re-infections and marked increases in total serum levels of antiparasite IgGs with augmented avidity. Long-term memory IgGs mainly reacted against high and low molecular weight parasite antigens. Immunofluorescence microscopy showed that circulating IgGs bound predominantly to late intracellular stage parasites, mainly schizonts.

CONCLUSIONS AND IMPLICATIONS

Low borrelidin doses protected mice from lethal malaria infections and induced protective immune responses after treatment. Development of combination therapies with borrelidin and selective modifications of the borrelidin molecule to specifically inhibit plasmodial threonyl tRNA synthetase should improve therapeutic strategies for malaria.

Preconditioning with hemin decreases Plasmodium chabaudi adami parasitemia and inhibits erythropoiesis in BALB/c mice

Increased susceptibility to bacterial and viral infections and dysfunctional erythropoiesis are characteristic of malaria and other hemolytic hemoglobinopathies. High concentrations of free heme are common in these conditions but little is known about the effect of heme on adaptive immunity and erythropoiesis. Herein, we investigated the impact of heme (hemin) administration on immune parameters and steady state erythropoiesis in BALB/c mice, and on parasitemia and anemia during Plasmodium chabaudi adami infection. Intra-peritoneal injection of hemin (5 mg/Kg body weight) over three consecutive days decreased the numbers of splenic and bone marrow macrophages, IFN-γ responses to CD3 stimulation and T(h)1 differentiation. Our results show that the numbers of erythroid progenitors decreased in the bone marrow and spleen of mice treated with hemin, which correlated with reduced numbers of circulating reticulocytes, without affecting hemoglobin concentrations. Although blunted IFN-γ responses were measured in hemin-preconditioned mice, the mice developed lower parasitemia following P.c.adami infection. Importantly, anemia was exacerbated in hemin-preconditioned mice with malaria despite the reduced parasitemia. Altogether, our data indicate that free heme has dual effects on malaria pathology.

Zinc and pregnancy: Marked changes on the immune response following zinc therapy for pregnant females challenged with Trypanosoma cruzi

BACKGROUND & AIMS

The occurrence of infectious disease processes during pregnancy has significant effects on maternal health and can lead to adverse pregnancy outcomes. The aim of the present study was to examine the potential role of zinc treatment during Trypanosoma cruzi infection in pregnant animals.

METHODS

Female Wistar rats weighing 180-200 g were used in all experiments. Production of nitric oxide, peritoneal macrophages counts, and concentrations of IFN-γ and TNF-α were measured, and the potential protective effects of zinc on fetal development were assessed at 14-day post-infection.

RESULTS

Nitric oxide concentrations were higher in pregnant zinc-treated animals than in their untreated counterparts, despite similar levels of the macrophages, IFN-γ and TNF-α. Zinc therapy was associated with a significant reduction in parasitemia and cardiac parasite burden. Higher placental and birth weights were observed in animals given prenatal zinc supplementation compared to untreated animals.

CONCLUSIONS

These data confirm the critical importance of adequate zinc intake during the peri-conceptional period and indicate that zinc has an effective role in preventing adverse outcomes of pregnancy and reducing the risk of common infections such as Chagas' disease.

Impact of indoor residual spraying with lambda-cyhalothrin on malaria parasitemia and anemia prevalence among children less than five years of age in an area of intense, year-round transmission in Malawi

Little is known about the impact of indoor residual spraying (IRS) in areas with intense malaria transmission such as sub-Saharan Africa. In Malawi, IRS with lambda-cyhalothrin has been applied annually in an area of intense year-long transmission since 2007. We evaluated the impact of IRS on parasitemia and anemia prevalence in children less than five years of age by using a cross-sectional household survey conducted in 2009, six months after the second IRS spray round. We measured malaria parasitemia and anemia (hemoglobin level < 11 g/dL) in 899 children less than five years of age and used binomial regression to assess the impact of IRS by comparing children living in a household sprayed with IRS (direct IRS) with those in a household not sprayed with IRS, but in an IRS area (indirect IRS) and those living in a household not sprayed with IRS and not in an IRS area (no IRS). In the IRS area, 77% of households reported receiving IRS. Adjusting for bed net use, house construction, and socioeconomic status, we found that receiving direct IRS and indirect IRS were significantly associated with a 33% (95% confidence interval [CI] = 1–54%) and 46% (95% CI = 20–64%) reduction in parasitemia and a 21% (95% CI = 4–34%) and 30% (95% CI = 12–45%) reduction in anemia prevalence, respectively.

Actively induced antigen-specific CD8+ T cells by epitope-bearing parasite pre-infection but not prime/boost virus vector vaccination could ameliorate the course of Plasmodium yoelii blood-stage infection

The lack of MHC molecules on red blood cells (RBCs) has led to questions regarding the immunological function of CD8(+) T cells against malarial blood-stage (MBS). However, several recent reports contradicting with this concept have suggested that they play an important role in the course of MBS infection. The present study generated genetically engineered murine malaria, Plasmodium yoelii, which expresses a well-defined Trypanosoma cruzi-derived, H-2K(b)-restricted CD8(+) T cell epitope, ANYNFTLV. Prime/boost vaccination by the use of recombinant adenovirus and recombinant modified vaccinia virus Ankara (MVA), which induced an enhanced number of ANYNFTLV-specific CD8(+) T cells, failed to prevent a pathological outcome to occur upon ANYNFTLV-expressing murine MBS infection. This outcome did not change even with the combination of passive transfer of an appreciable number of in vitro-expanded ANYNFTLV-specific CD8(+) T cells. In contrast, the pre-infection of mice with T. cruzi, which intrinsically bears the same CD8(+) T cell epitope significantly improved the survival of ANYNFTLV-expressing malaria-infected mice but not that of control malaria-infected ones. This protective effect was abrogated by the use of a CD8(+) T cell-depleting monoclonal antibody. Although the protective effect was observed only in certain situations, the actively induced antigen-specific CD8(+) T cells could ameliorate the pathologies caused by the MBS. This is the first study to implicate that the active induction of antigen-specific CD8(+) T cells should be included in the development of a vaccine against MBS.

Antimalarial plant remedies from Burkina Faso: their potential for prophylactic use

ETHNOPHARMACOLOGICAL RELEVANCE

Saye, a combination remedy prepared from Cochlospermum planchonii Hook.f. (Cochlospermaceae), Cassia alata L. (Fabaceae) and Phyllanthus amarus Schumach. et Thonn. (Euphorbiaceae), N'Dribala, a Cochlospermum planchonii root decoction, and a fruit preparation of Azadirachta indica A. Juss. (Meliaceae) are plant remedies of the folk medicine in Burkina Faso and are commonly used by traditional healers for the treatment of malaria.

AIM OF THE STUDY

This study aimed at validating the antiplasmodial activity of the preparations and at estimating their potential for prophylaxis, using the murine malaria system Plasmodium berghei/Anopheles stephensi.

MATERIALS AND METHODS

Aqueous extracts were orally administered to mice (6 animals per treatment group) at a daily dose of 200mg/kg body weight for nine days, applying protocols that mimic as much as possible traditional recipes and treatment schemes.

RESULTS

Saye, N'Dribala and Azadirachta indica preparations revealed prophylactic activity, reducing parasitaemia in treated mice, with respect to controls, by 52.0% (CI(95) 46.1-57.9), 45.5% (CI(95) 44.5-46.5) and 45.0% (CI(95) 41.1-48.9), respectively. No evidence of transmission blocking effects was detected with any of the tested remedies.

CONCLUSIONS

This study confirms, in the murine malaria system, the antiplasmodial properties of the examined remedies on the Plasmodium stages developing in the vertebrate host, thus encouraging studies aiming at identifying the active fractions and compounds responsible for the described activity and to develop standardized prophylactic remedies.

Immunization with L. sigmodontis microfilariae reduces peripheral microfilaraemia after challenge infection by inhibition of filarial embryogenesis

BACKGROUND

Lymphatic filariasis and onchocerciasis are two chronic diseases mediated by parasitic filarial worms causing long term disability and massive socioeconomic problems. Filariae are transmitted by blood-feeding mosquitoes that take up the first stage larvae from an infected host and deliver it after maturation into infective stage to a new host. After closure of vector control programs, disease control relies mainly on mass drug administration with drugs that are primarily effective against first stage larvae and require many years of annual/biannual administration. Therefore, there is an urgent need for alternative treatment ways, i.e. other effective drugs or vaccines.

METHODOLOGY/PRINCIPAL FINDINGS

Using the Litomosoides sigmodontis murine model of filariasis we demonstrate that immunization with microfilariae together with the adjuvant alum prevents mice from developing high microfilaraemia after challenge infection. Immunization achieved 70% to 100% protection in the peripheral blood and in the pleural space and furthermore strongly reduced the microfilarial load in mice that remained microfilaraemic. Protection was associated with the impairment of intrauterine filarial embryogenesis and with local and systemic microfilarial-specific host IgG, as well as IFN-γ secretion by host cells from the site of infection. Furthermore immunization significantly reduced adult worm burden.

CONCLUSIONS/SIGNIFICANCE

Our results present a tool to understand the immunological basis of vaccine induced protection in order to develop a microfilariae-based vaccine that reduces adult worm burden and prevents microfilaraemia, a powerful weapon to stop transmission of filariasis.

In vivo sensitivity monitoring of chloroquine for the treatment of uncomplicated vivax malaria in four bordered provinces of Thailand during 2009-2010

BACKGROUND & OBJECTIVES

Chloroquine (CQ), followed by 14 - day primaquine, is the recommended regimen for the treatment of Plasmodium vivax infection in Thailand. CQ resistant P. vivax (CRPv) has not yet challenged the efficacy of the drug. The present study was conducted to assess the current response of P. vivax to CQ alone in Thailand.

METHODS

A 28-day in vivo therapeutic efficacy study was conducted from June 2009 to December 2010 in 4 sentinel sites. Recurrence of parasitaemia and the clinical condition of patients were assessed on each visit during follow -up. The drug levels in recurrent patients' blood were measured using HPLC. Data were analyzed using the WHO 2008 program for the analysis of in vivo tests.

RESULTS

Of the total 212 patients included in the study, 201 completed the 28-days follow- up, while 11 were excluded. In five patients (2.5%), parasitaemia reappeared within the 28-days follow - up. On the day of recurrent parasitaemia, the level of chloroquine/desethylchloroquine (CQ - DCQ) was above the minimum effective concentration (>100 ng/ml) in one patient, but lower in four patients.

CONCLUSION

Reappearance of the parasite within 28 days of follow - up in one of five patients was due to parasite resistance to CQ. The 2.5% prevalence of CQ treatment failure for P. vivax malaria in the study areas signals the need to launch monitoring activities for CQ resistant P. vivax in malaria endemic areas in order to detect further development of parasite resistance and to estimate the level of burden across the country.

Quantifying the importance of MSP1-19 as a target of growth-inhibitory and protective antibodies against Plasmodium falciparum in humans

Background

Antibodies targeting blood stage antigens are important in protection against malaria, but the key targets and mechanisms of immunity are not well understood. Merozoite surface protein 1 (MSP1) is an abundant and essential protein. The C-terminal 19 kDa region (MSP1-19) is regarded as a promising vaccine candidate and may also be an important target of immunity.

Methodology/Findings

Growth inhibitory antibodies against asexual-stage parasites and IgG to recombinant MSP1-19 were measured in plasma samples from a longitudinal cohort of 206 children in Papua New Guinea. Differential inhibition by samples of mutant P. falciparum lines that expressed either the P. falciparum or P. chabaudi form of MSP1-19 were used to quantify MSP1-19 specific growth-inhibitory antibodies. The great majority of children had detectable IgG to MSP1-19, and high levels of IgG were significantly associated with a reduced risk of symptomatic P. falciparum malaria during the 6-month follow-up period. However, there was little evidence of PfMSP1-19 specific growth inhibition by plasma samples from children. Similar results were found when testing non-dialysed or dialysed plasma, or purified antibodies, or when measuring growth inhibition in flow cytometry or microscopy-based assays. Rabbit antisera generated by immunization with recombinant MSP1-19 demonstrated strong MSP1-19 specific growth-inhibitory activity, which appeared to be due to much higher antibody levels than human samples; antibody avidity was similar between rabbit antisera and human plasma.

Conclusions/Significance

These data suggest that MSP1-19 is not a major target of growth inhibitory antibodies and that the protective effects of antibodies to MSP1-19 are not due to growth inhibitory activity, but may instead be mediated by other mechanisms. Alternatively, antibodies to MSP1-19 may act as a marker of protective immunity.

Exosomes from Plasmodium yoelii-infected reticulocytes protect mice from lethal infections

Exosomes are 30-100-nm membrane vesicles of endocytic origin that are released after the fusion of multivesicular bodies (MVBs) with the plasma membrane. While initial studies suggested that the role of exosomes was limited to the removal of proteins during the maturation of reticulocytes to erythrocytes, recent studies indicate that they are produced by different types of cells and are involved in promoting inter-cellular communication and antigen presentation. Here, we describe the isolation and characterization of exosomes from peripheral blood of BALB/c mice infected with the reticulocyte-prone non-lethal Plasmodium yoelii 17X strain. Importantly, proteomic analysis revealed the presence of parasite proteins in these vesicles. Moreover, immunization of mice with purified exosomes elicited IgG antibodies capable of recognizing P. yoelii-infected red blood cells. Furthermore, lethal challenge of immunized mice with the normocyte-prone lethal P. yoelii 17XL strain caused a significant attenuation in the course of parasitaemia, increased survival time, and altered the cell tropism to reticulocytes. These results were obtained also when the exosomes were isolated from a P. yoelii-infected reticulocyte culture indicating that reticulocyte-derived exosomes carry antigens and are involved in immune modulation. Moreover, inclusion of CpG ODN 1826 in exosome immunizations elicited IgG2a and IgG2b antibodies and promoted survival, clearance of parasites and subsequent sterile protection of 83% of the animals challenged with P. yoelli 17XL. To our knowledge, this is the first report of immune responses elicited by exosomes derived from reticulocytes opening new avenues for the modulation of anti-malaria responses.

Protection from experimental cerebral malaria with a single dose of radiation-attenuated, blood-stage Plasmodium berghei parasites

Background

Whole malaria parasites are highly effective in inducing immunity against malaria. Due to the limited success of subunit based vaccines in clinical studies, there has been a renewed interest in whole parasite-based malaria vaccines. Apart from attenuated sporozoites, there have also been efforts to use live asexual stage parasites as vaccine immunogens.

Methodology and Results

We used radiation exposure to attenuate the highly virulent asexual blood stages of the murine malaria parasite P. berghei to a non-replicable, avirulent form. We tested the ability of the attenuated blood stage parasites to induce immunity to parasitemia and the symptoms of severe malaria disease. Depending on the mouse genetic background, a single high dose immunization without adjuvant protected mice from parasitemia and severe disease (CD1 mice) or from experimental cerebral malaria (ECM) (C57BL/6 mice). A low dose immunization did not protect against parasitemia or severe disease in either model after one or two immunizations. The protection from ECM was associated with a parasite specific antibody response and also with a lower level of splenic parasite-specific IFN-γ production, which is a mediator of ECM pathology in C57BL/6 mice. Surprisingly, there was no difference in the sequestration of CD8+ T cells and CD45+ CD11b+ macrophages in the brains of immunized, ECM-protected mice.

Conclusions

This report further demonstrates the effectiveness of a whole parasite blood-stage vaccine in inducing immunity to malaria and explicitly demonstrates its effectiveness against ECM, the most pathogenic consequence of malaria infection. This experimental model will be important to explore the formulation of whole parasite blood-stage vaccines against malaria and to investigate the immune mechanisms that mediate protection against parasitemia and cerebral malaria.

Characterization of peripheral blood T lymphocyte subsets in Chinese rhesus macaques with repeated or long-term infection with Plasmodium cynomolgi

T lymphocytes play a vital role in antimalaria immunity, but there is little information about the role of T cells in malaria infection. In order to explore the profile of T cells in malaria immunity, we infected Chinese rhesus macaques with the malaria parasite (Plasmodium cynomolgi) and examined the dynamics of T cell subsets. Both repeated and long-term infections were involved. Our results showed that the monkeys in the repeated infection group acquired protective immunity through primary infection, which was evidenced by a much lower parasitemia, milder anemia, and milder fever during reinfection; the monkeys in the long-term infection group also developed protective immunity, but this was not sufficient to eliminate the parasite. The total counts of leukocytes, neutrophils, CD3+ T cells, CD4+ or CD8+ T cells, and naïve and memory CD4+ and CD8+ T cells declined during the acute phase of malaria but increased after the parasite was controlled. The total number of activated CD4+ T cells significantly increased during malaria in animals with a long-term infection, which remained at least 3 months after the termination of malaria. However, the activated CD4+ T cells decreased during the acute phase of infection in the repeated infection group and converted to preinfection levels after malaria was cured. Regulatory CD4+ T cells continued to increase during the malaria infections and quickly reverted to preinfection levels after the parasite was controlled. Our study provides a systematic analysis of the kinetic profiles of T lymphocyte subsets during malaria infections and provides some experimental insight into malaria immunology.

Testing the efficacy of a multi-component DNA-prime/DNA-boost vaccine against Trypanosoma cruzi infection in dogs

Background

Trypanosoma cruzi, the etiologic agent of Chagas Disease, is a major vector borne health problem in Latin America and an emerging infectious disease in the United States.

Methods

We tested the efficacy of a multi-component DNA-prime/DNA-boost vaccine (TcVac1) against experimental T. cruzi infection in a canine model. Dogs were immunized with antigen-encoding plasmids and cytokine adjuvants, and two weeks after the last immunization, challenged with T. cruzi trypomastigotes. We measured antibody responses by ELISA and haemagglutination assay, parasitemia and infectivity to triatomines by xenodiagnosis, and performed electrocardiography and histology to assess myocardial damage and tissue pathology.

Results

Vaccination with TcVac1 elicited parasite-and antigen-specific IgM and IgG (IgG2>IgG1) responses. Upon challenge infection, TcVac1-vaccinated dogs, as compared to non-vaccinated controls dogs, responded to T. cruzi with a rapid expansion of antibody response, moderately enhanced CD8⁺ T cell proliferation and IFN-γ production, and suppression of phagocytes’ activity evidenced by decreased myeloperoxidase and nitrite levels. Subsequently, vaccinated dogs controlled the acute parasitemia by day 37 pi (44 dpi in non-vaccinated dogs), and exhibited a moderate decline in infectivity to triatomines. TcVac1-immunized dogs did not control the myocardial parasite burden and electrocardiographic and histopatholgic cardiac alterations that are the hallmarks of acute Chagas disease. During the chronic stage, TcVac1-vaccinated dogs exhibited a moderate decline in cardiac alterations determined by EKG and anatomo-/histo-pathological analysis while chronically-infected/non-vaccinated dogs continued to exhibit severe EKG alterations.

Conclusions

Overall, these results demonstrated that TcVac1 provided a partial resistance to T. cruzi infection and Chagas disease, and provide an impetus to improve the vaccination strategy against Chagas disease.

Immunization of dogs with DNA-prime/DNA-boost vaccine (TcVac1) enhanced the Trypanosoma cruzi-specific type 1 antibody and CD8⁺ T cell responses that resulted in an early control of acute parasitemia and a moderate decline in pathological symptoms during chronic phase. Further improvement of vaccine-induced immunity would be required to achieve clinical and epidemiological benefits and prevent transmission of parasites from vaccinated/infected dogs to triatomines.