Helminths, human immunodeficiency virus and tuberculosis

Intestinal helminth co-infection and associated factors among pulmonary tuberculosis patients in Africa and Asia: a systematic review and meta-analysis

INTRODUCTION

Tuberculosis (TB) and intestinal helminths have huge public health importance, and they are geographically overlapped. Data about the burden of intestinal helminth and TB co-infection in these areas are fragmented. In this systematic review and meta-analysis we compile the current literatures and generate pooled prevalence. We also identity factors associated with intestinal helminth co-infection among TB patients.

METHODS

Original articles published in English language up to March 23, 2022 were systematically searched from electronic database (PubMed/Medline, Scopus, Science Direct, Google Scholars and HINARI). The search was done using medical subject heading terms and keywords. Identified articles were exported into the EndNote library. The identified articles were screened using PRISMA flow diagram. Then the methodological quality of included articles was evaluated and rated using the modified version of Newcastle-Ottawa Scale. Data were extracted using Microsoft Excel. Sensitivity analysis and Egger regression test were used for the assessment of heterogeneity and publication bias. Finally the results are presented with a meta-analysis of pooled estimates, forest plots, and tables. The quantitative data were analyzed using Stata version 14.

RESULTS

From a total of 5457 searched articles, 22 eligible articles were included in the review. The pooled prevalence of helminth co-infection among TB cases was 29.69% (95%CI: 21.10, 38.29). TB patients were found to more frequently harbor one or more intestinal helminths than TB negative individuals (OR = 1.72 (95%CI: 1.20, 2.48)). Among the reported helminths, Schistosoma mansoni and Strongyloides stercoralis had the highest pooled prevalence among TB cases. However, unlike other individual helminths, only Strongyloides stercoralis (OR = 2.67 (95% CI, 1.20-6.76)) had significant association with TB cases compared to TB negatives. BMI was significantly associated with intestinal helminth co-infection among TB patients (OR = 2.75 (95%CI: 1.19, 6.38)).

CONCLUSIONS

Patients with TB have been shown to harbor co-infection with one or more intestinal helminths with considerable proportions when compared with TB-negative individuals. The higher prevalence of helminth infection in TB cases might indicate that co-infection promotes active TB disease. Thus, routine intestinal helminth screening and assessment of their nutritional status is suggested for TB patients.

Magnitude and predisposing factors of intestinal parasitosis and tuberculosis coinfection at five health institutions in Southern Ethiopia: A cross-sectional study

Background and Aims

Intestinal parasites affect the tuberculosis disease outcome by shifting the cell-mediated to humoral immune response and host immune system suppression. However, Mycobacterium tuberculosis (MTB) infection favors the immune escape of parasites. Hence, exploring the rate of intestinal parasitic coinfection with pulmonary tuberculosis (PTB) and its predisposing factors to take better preventive, control, and management measures.

Methods

A facility-based cross-sectional study was conducted from September to December 2020 at five health institutions in Hawassa city. A total of 214 PTB patients were diagnosed using the GeneXpert assay and enrolled in this study. Demographic, clinical, and risk factors data were collected using a structured questionnaire. Stool samples were collected using a clean, labeled, and leak-proof stool cup. Stool samples were examined using direct saline microscopy and the formal-ether concentration technique. The data were entered and coded in SPSS software for analysis. Bivariate and multivariate logistic regression were employed to identify the associated risk factors. A p-value less than  0.05 was considered statistically significant.

Results

The overall rate of intestinal parasitic-MTB coinfection was 36.9%. The most dominant intestinal parasite was Gardia lamblia (17.8%, 38), followed by Entamoeba histolytica/dispar (9.3%, 20). Intestinal parasitosis coinfection of PTB was associated with being rural resident (adjusted odds ratio [AOR] = 2.42; 95% confidence interval [CI]: 1.23-4.8), not washing of fruits and vegetables before eating [AOR = 4.14; 95% CI: 1.92-9], being at the early stage of anti-TB treatment [AOR = 3; 95% CI: 1.5-6.3] and presence of chronic diseases [AOR = 7; 95% CI: 3.4-14].

Conclusion

The burden of intestinal parasites-MTB coinfection was high. Those who wash fruits and vegetables before eating should be encouraged, early treatment of PTB patients and avoiding the practice of open-field defecation, especially in rural communities, is necessary. The dual effect of coinfection on disease severity and treatment success needs further cohort study.

Severe disseminated tuberculosis in HIV-negative refugees

In high-income countries, the presentation of tuberculosis is changing, primarily because of migration, and understanding the specific health needs of susceptible populations is becoming increasingly important. Although disseminated tuberculosis is well documented in HIV-positive patients, the disease is poorly described and less expected in HIV-negative individuals. In this Grand Round, we report eight HIV-negative refugees, who presented with extensively disseminated tuberculosis. We discuss the multifactorial causes, such as deprivations during long journeys, precarious living conditions, and the experience of violence, which might add to nutritional factors and chronic disorders, eventually resulting in a state of predisposition to immune deficiency. We also show that disseminated tuberculosis is often difficult to diagnose when pulmonary symptoms are absent. Communication difficulties between refugees and health-care workers are another major hurdle, and every effort should be made to get a valid patient history. This medical history is crucial to guide imaging and other diagnostic procedures to establish a definite diagnosis, which should be confirmed by a positive tuberculosis culture. Because many of these patients are at risk for multidrug-resistant tuberculosis, drug susceptibility testing is imperative to guide therapy. In the absence of treatment guidelines for this entity, clinicians can determine treatment duration according to recommendations provided for extrapulmonary tuberculosis and affected organs. Paradoxical expansion of tuberculous lesions during therapy should be treated with corticosteroids. In many cases, treatment duration must be individualised and might even exceed 12 months.

Effects of fluconazole on the clinical outcome and immune response in fungal co-infected tuberculosis patients

With overuse of the broad-spectrum antibiotics, the pulmonary fungal infection increasingly becomes the most common complication associated with senile pulmonary tuberculosis (TB) and attracts intensive attentions from clinicians. Here we presented the retrospective analysis of impact of fluconazole treatment on the clinical outcome and immune response in fungal co-infected tuberculosis patients. A randomized, double-blind, placebo-controlled trial of fluconazole (100 mg per day for consecutive weeks) in fungal-positive senile tuberculosis patients was conducted in our hospital. Peripheral eosinophil counts were computed by the automatic hematology analyzer. The secretory inflammatory cytokines interferon (IFN)-γ, tumor necrosis factor (TNF)-α and chemokines chemokine C-X-C motif ligand (CXCL)9, CXCL10, CXCL11 were determined with enzyme-linked immunosorbent assay kits. The peripheral T helper 1 cells (Th1) and regulatory T cells (Treg) population were analyzed by flow cytometry. None of significant difference in respect to baseline TB score was observed between placebo and fluconazole groups. Administration of fluconazole significantly stimulated eosinophils population and secretion of inflammatory cytokines IFN-γ and TNF-α. Simultaneously, the peripheral Th1% and chemokines including CXCL9, CSCL10, CXCL11 were markedly induced in response to fluconazole treatment. Fungal infection significantly affected host immunity during tuberculosis which was effectively reversed by fluconazole treatment.

Clinical response of tuberculosis patients, a prospective cohort study

Clinical response means a response to drug intake that can be detected and appreciated by a change in signs and symptoms. The objectives of this study were to assess time to clinical response, the incidence density for clinical response and determinants of clinical response of tuberculosis (TB) patients in the intensive phases of TB treatment. Prospective cohort study design was implemented. The target population for this study was all patients following the directly observed therapy. Baseline data has been collected during the start of the directly observed TB treatment strategy. We have been collected updated data after the seven days of the baseline data collection, then after every seven days updated data has been collected from each pulmonary and extra pulmonary TB patients. Kaplan Meier curve was used to estimate time to clinical response. Incidence density using person days was used to estimate incidence of clinical response. Cox proportional hazard model was used to identify the predictors of clinical responses. A total of 1608 TB patients were included with a response rate at 99.5%. The mean age of the respondents was 24.5 years [standard deviation (SD) 14.34 years]. The incidence density for clinical response was 1429/38529 person days. One fourth of the TB patients showed clinical response at day 14, 25% of at day 21 and 75% o at day 31. Predictors of clinical response for TB patients includes: age (AHR 1.007 [95% CI 1.003-1.011]), type of TB (AOR 2.3[95% CI 2.04-2.59]), Previous history of TB (AHR 0.18 [95% CI 0.11-0 .30]), Intestinal parasitic infection (AOR 0.22[95% CI 0.19-0.26]), hemoglobin (AOR 2.35 [95% CI 2.18-2.54]), weight gain (AOR 1.11 [95% CI 1.05-1.17]), Micronutrient supplementation (AOR 9.71 [95% CI 8.28-11.38]), male sex (AOR 0.87 [95% CI 0.79-0.97]).The clinical responses for extra-pulmonary TB patients were slower than pulmonary TB. Deworming and micronutrient supplementation should be considered as the additional TB treatment strategy for TB patients.

Parasitismo intestinal y tuberculosis

Introducción.La tuberculosis es coendémica en áreas con alta prevalencia de parasitismo intestinal. Se ha sugerido que, en pacientes con tuberculosis latente, la parasitosis intestinal por helmintos puede desencadenar progresión hacia la forma pulmonar activa, pero esta relación es controversial.Objetivo. Realizar una revisión narrativa de la literatura respecto a la relación existente entre el parasitismo intestinal y la infección por Mycobacterium tuberculosis.Materiales y métodos. Se llevó a cabo una búsqueda de la literatura publicada en las bases de datos ProQuest, EBSCO, ScienceDirect, Pubmed, LILACS, Embase, Trip Database, SciELO y Cochrane Library, con los términos: [Tuberculosis] AND [Intestinal diseases, parasitic] AND [Helminths]; [Tuberculosis] AND [Intestinal diseases, parasitic]; [Tuberculosis] AND [Helminths] en inglés y con sus equivalentes en español. Esta búsqueda se limitó a revisiones sistemáticas con o sin metaanálisis, estudios de cohorte y casos y controles.Resultados. Se encontraron 1 revisión sistemática, 2 estudios de cohorte y 44 estudios de casos y controles con información relevante para el desarrollo de la presente revisión.Conclusiones. La evidencia disponible fue insuficiente para afirmar que el parasitismo intestinal predispone al desarrollo de la enfermedad tuberculosa. Los estudios realizados hasta ahora han encontrado resultados estadísticamente no significativos.

Effects of Helminth Eradication on the Immune System

Introduction:

Helminth infection has a profound effect on the immune system. However, the precise nature of the immune changes that are elicited by helminth infection have not been sufficiently characterized. Furthermore, the reversibility of these changes after treatment has not been documented sufficiently. We studied the immune profiles of Ethiopian immigrants to Israel at baseline, that is on arrival and at one-year follow-up and compared individuals who received antihelminth treatment during the study period with those who missed the treatment.

Methods:

A longitudinal follow up study involving different groups of subjects was conducted. Baseline data was recorded from the newly arrived Ethiopian immigrants for a series of peripheral blood tests, including: IgE and Eosinophil levels, T-cell populations, T-cell receptor phenotypes, and cytokine measurement. These tests were all repeated after a 1-year interval. Results were compared between the newly arrived Ethiopian immigrants (NEW-Eth-Il), long term Ethiopian immigrants (LT-Eth-Il), and non Ethiopian Israeli controls (NON-Imm-Il).

Results:

Of the 184 individuals, 111 were NEW-Eth-Il, who had a high prevalence of helminth infection, the immunological changes were elevated IgE levels and eosinophil counts, decreased CD4/CD8 ratio, increased proportion of HLA-DR+CD3+, HLA-DR+CD4+ and HLA-DR+CD8+ cells, decreased proportion of CD45RA+CD4+ (naive) and CD28+CD8+ cells, increased proportion of CD45RO+CD4+ (memory) cells, and increased secretion of IL-4 and IL-5 (Th2 type cytokines). In the 42 LT-Eth-Il participants, who all had negative tests for helminth infection, we did not observe these immune changes and their immune profile did not differ markedly from that of the NON-Imm-Il controls. The follow-up immune profiles of 33 NEW-Eth-Il who received succesful antihelminth treatment, showed a significant normalization in the above-mentioned variables that was not observed in the 19 NEW-Eth-Il who missed and did not receive the antihelminth treatment.

Conclusions:

These findings demonstrate that helminth infection is associated with profound immune changes that are normalized within a short time after helminth eradication. They also strengthen the hypothesis that effective antihelminth interventions, in areas endemic for intestinal helminths, may have an impact on AIDS and tuberculosis epidemics.

Vitamin D deficiency among newly diagnosed tuberculosis patients and their household contacts: a comparative cross-sectional study

Background

Recent studies suggest that the incidence and severity of tuberculosis is associated with low levels of vitamin D. Even though individuals living in Ethiopia have a high exposure to sunlight which is a source of vitamin D, tuberculosis is still one of the major causes of morbidity and mortality in the country. Therefore, this study aimed to determine the prevalence and associated factors of vitamin D deficiency in newly diagnosed tuberculosis patients, household contacts and community controls in Gondar, Ethiopia.

Methods

A comparative cross-sectional study design was conducted. Blood samples were collected from newly diagnosed smear positive pulmonary TB patients, their household contacts and community controls. Serum 25(OH)-vitamin D₃ was determined by an Enzyme Linked Immunosorbent Assay. A serum level of 25(OH)-vitamin D₃ below < 50 nmol/L was defined as vitamin D deficiency and <25 nmol/L as severe vitamin D deficiency.

Results

A total of 126 newly diagnosed smear positive TB patients, 57 house hold contacts and 70 apparently community controls were included in the study. The mean ± SD age (years) of TB patients, house hold contacts and community controls was 29.8 ± 11.9, 24.3 ± 14.7 and 27.3 ± 7.6 respectively. Ninety out of 126 (71.4%) TB patients were underweight with a BMI of < 18.5 kg/m². The mean 25(OH)-vitamin D₃ level of TB patients (30.1 ± 19.3 nmol/L) was significantly lower than community controls (38.5 ± 20.9 nmol/L, P = 0.005 and household contacts (37.7 ± 12.8 nmol/L, P =0.031).). The prevalence of vitamin D deficiency was higher in TB patients (83.3%) than in community controls (67.1%, P = 0.009). The prevalence of vitamin D deficiency was also found higher in household contacts (80.7%). Severe vitamin D deficiency was observed in 53%(67/126), 30% (21/70), 19.3%(11/57) of TB patients, community controls and household contacts respectively. Low BMI (AOR = 2.13; 95%CI: 1.02, 3.28) and being positive for tuberculosis (AOR = 1.93; 95%CI: 1.06, 2.86) were significant predictors of severe vitamin D deficiency.

Conclusion

High prevalence of vitamin D deficiency was found among newly diagnosed TB patients and in their household contacts. The present study warrants further studies to determine the role of vitamin D supplementation in the prevention and treatment of tuberculosis in Ethiopia.

Intestinal helminth co-infection and associated factors among tuberculosis patients in Arba Minch, Ethiopia

BACKGROUND

Helminths affect the outcome of tuberculosis by shifting cell mediated immune response to humoral and by total suppression of the host immune system. On the reverse, Mycobacterium infection favors immune escape of helminths. Therefore assessing helminth co-infection rate and predisposing factors in tuberculosis patients is mandatory to set strategies for better case management.

METHODS

Facility based cross-sectional study was conducted in Arba Minch to assess the prevalence and associated factors of intestinal helminths among pulmonary tuberculosis patients from January to August, 2016. A structured questionnaire was used to capture data about socio-demographic characteristics, clinical history and possible risk factors for intestinal helminth infections. Height and weight were measured to calculate body-mass index. Appropriate amount of stool was collected and processed by direct saline and formol-ether concentration techniques following standard protocols. All the data were analyzed using SPSS version 20.0.

RESULTS

A total of 213 (57.3% male and 42.7% female) pulmonary tuberculosis patients were participated in the study. The overall co-infection rate of intestinal parasites was 26.3%. The infection rate of intestinal helminths account 24.4% and that of intestinal protozoa was 6.1%. Ascaris lumbricoides accounted the highest frequency of 11.3%. Living in rural residence (AOR = 3.175, 95% CI: 1.102-9.153, p = 0.032), Eating vegetables/ fruits without washing or peeling off (AOR = 2.208, 95% CI: 1.030-4.733, p = 0.042) and having body-mass index <18.5 (AOR = 3.511, 95% CI: 1.646-7.489, p = 0.001) were associated with intestinal helminth infection.

CONCLUSION

The infection rate by intestinal helminths was 24.4%. Ascaris lumbricoides was the most prevalent helminth. Residence, habit of washing vegetables/fruits before use and body-mass index were associated factors with intestinal helminthiasis. Therefore health care providers should screen and treat TB patients for intestinal helminthiasis in order to ensure good prognosis.

Concurrent loss of co-stimulatory molecules and functional cytokine secretion attributes leads to proliferative senescence of CD8(+) T cells in HIV/TB co-infection

The role of T-cell immunosenescence and functional CD8(+) T-cell responses in HIV/TB co-infection is unclear. We examined and correlated surrogate markers of HIV disease progression with immune activation, immunosenescence and differentiation using T-cell pools of HIV/TB co-infected, HIV-infected and healthy controls. Our investigations showed increased plasma viremia and reduced CD4/CD8 T-cell ratio in HIV/TB co-infected subjects relative to HIV-infected, and also a closer association with changes in the expression of CD38, a cyclic ADP ribose hydrolase and CD57, which were consistently expressed on late-senescent CD8(+) T cells. Up-regulation of CD57 and CD38 were directly proportional to lack of co-stimulatory markers on CD8(+) T cells, besides diminished expression of CD127 (IL-7Rα) on CD57(+)CD4(+) T cells. Notably, intracellular IFN-γ, perforin and granzyme B levels in HIV-specific CD8(+) T cells of HIV/TB co-infected subjects were diminished. Intracellular CD57 levels in HIV gag p24-specific CD8(+) T cells were significantly increased in HIV/TB co-infection. We suggest that HIV-TB co-infection contributes to senescence associated with chronic immune activation, which could be due to functional insufficiency of CD8(+) T cells.

Mechanistic insights on immunosenescence and chronic immune activation in HIV-tuberculosis co-infection

Immunosenescence is marked by accelerated degradation of host immune responses leading to the onset of opportunistic infections, where senescent T cells show remarkably higher ontogenic defects as compared to healthy T cells. The mechanistic association between T-cell immunosenescence and human immunodeficiency virus (HIV) disease progression, and functional T-cell responses in HIV-tuberculosis (HIV-TB) co-infection remains to be elaborately discussed. Here, we discussed the association of immunosenescence and chronic immune activation in HIV-TB co-infection and reviewed the role played by mediators of immune deterioration in HIV-TB co-infection necessitating the importance of designing therapeutic strategies against HIV disease progression and pathogenesis.

Quadruple burden of HIV/AIDS, tuberculosis, chronic intestinal parasitoses, and multiple micronutrient deficiency in ethiopia: a summary of available findings

Human immunodeficiency virus (HIV), tuberculosis (TB), and helminthic infections are among the commonest public health problems in the sub-Saharan African countries like Ethiopia. Multiple micronutrient deficiencies also known as the “hidden hunger” are common in people living in these countries either playing a role in their pathogenesis or as consequences. This results in a vicious cycle of multiple micronutrient deficiencies and infection/disease progression. As infection is profoundly associated with nutritional status resulting from decreased nutrient intake, decreased nutrient absorption, and nutrient losses, micronutrient deficiencies affect immune system and impact infection and diseases progression. As a result, micronutrients, immunity, and infection are interrelated. The goal of this review is therefore to provide a summary of available findings regarding the “quadruple burden trouble” of HIV, TB, intestinal parasitic infections, and multiple micronutrient deficiencies to describe immune-modulating effects related to disorders.

Atorvastatin reduces T-cell activation and exhaustion among HIV-infected cART-treated suboptimal immune responders in Uganda: a randomised crossover placebo-controlled trial

OBJECTIVE

T-cell activation independently predicts mortality, poor immune recovery and non-AIDS illnesses during combination antiretroviral therapy (cART). Atorvastatin showed anti-immune activation effects among HIV-infected cART-naïve individuals. We investigated whether adjunct atorvastatin therapy reduces T-cell activation among cART-treated adults with suboptimal immune recovery.

METHODS

A randomised double-blind placebo-controlled crossover trial, of atorvastatin 80 mg daily vs. placebo for 12 weeks, was conducted among individuals with CD4 increase <295 cells/μl after seven years of suppressive cART. Change in T-cell activation (CD3 + CD4 + /CD8 + CD38 + HLADR+) and in T-cell exhaustion (CD3 + CD4 + /CD8 + PD1 + ) was measured using flow cytometry.

RESULTS

Thirty patients were randomised, 15 to each arm. Atorvastatin resulted in a 28% greater reduction in CD4 T-cell activation (60% reduction) than placebo (32% reduction); P = 0.001. Atorvastatin also resulted in a 35% greater reduction in CD8-T-cell activation than placebo (49% vs. 14%, P = 0.0009), CD4 T-cell exhaustion (27% vs. 17% in placebo), P = 0.001 and CD8 T-cell exhaustion (27% vs. 16%), P = 0.004. There was no carry-over/period effect. Expected adverse events were comparable in both groups, and no serious adverse events were reported.

CONCLUSION

Atorvastatin reduced T-cell immune activation and exhaustion among cART-treated adults in a Ugandan cohort. Atorvastatin adjunct therapy should be explored as a strategy to improve HIV treatment outcomes among people living with HIV in sub-Saharan Africa.

Effects of albendazole on the clinical outcome and immunological responses in helminth co-infected tuberculosis patients: a double blind randomised clinical trial

Despite several review papers and experimental studies concerning the impact of chronic helminth infection on tuberculosis in recent years, there is a scarcity of data from clinical field studies in highly endemic areas for these diseases. We believe this is the first randomised clinical trial investigating the impact of albendazole treatment on the clinical and immunological outcomes of helminth co-infected tuberculosis patients. A randomised, double-blind, placebo-controlled trial of albendazole (400mg per day for 3 days) in helminth-positive tuberculosis patients was conducted in Gondar, Ethiopia. The primary outcome was clinical improvement (ΔTB score) after 2 months. Among secondary outcomes were changes in the levels of eosinophils, CD4+ T cells, regulatory T cells, IFN-γ, IL-5 and IL-10 after 3 months. A total of 140 helminth co-infected tuberculosis patients were included with an HIV co-infection rate of 22.8%. There was no significant effect on the primary outcome (ΔTB score: 5.6±2.9 for albendazole versus 5.9±2.5 for placebo, P=0.59). The albendazole-treated group showed a decline in eosinophil cells (P=0.001) and IL-10 (P=0.017) after 3 months. In an exploratory analysis after 12 weeks, the albendazole treated group showed a trend towards weight gain compared with the placebo group (11.2±8.5 kg versus 8.2±8.7 kg, P=0.08)). The reductions in eosinophil counts and IL-10 show that asymptomatic helminth infection significantly affects host immunity during tuberculosis and can be effectively reversed by albendazole treatment. The clinical effects of helminth infection on chronic infectious diseases such as tuberculosis merit further characterisation.

Gastrointestinal helminths may affect host susceptibility to anthrax through seasonal immune trade-offs

Background

Most vertebrates experience coinfections, and many pathogen-pathogen interactions occur indirectly through the host immune system. These interactions are particularly strong in mixed micro-macroparasite infections because of immunomodulatory effects of helminth parasites. While these trade-offs have been examined extensively in laboratory animals, few studies have examined them in natural systems. Additionally, many wildlife pathogens fluctuate seasonally, at least partly due to seasonal host immune changes. We therefore examined seasonality of immune resource allocation, pathogen abundance and exposure, and interactions between infections and immunity in plains zebra (Equus quagga) in Etosha National Park (ENP), Namibia, a system with strongly seasonal patterns of gastrointestinal (GI) helminth infection intensity and concurrent anthrax outbreaks. Both pathogens are environmentally transmitted, and helminth seasonality is driven by environmental pressures on free living life stages. The reasons behind anthrax seasonality are currently not understood, though anthrax is less likely directly driven by environmental factors.

Results

We measured a complex, interacting set of variables and found evidence that GI helminth infection intensities, eosinophil counts, IgE and IgGb antibody titers, and possibly IL-4 cytokine signaling were increased in wetter seasons, and that ectoparasite infestations and possibly IFN-γ cytokine signaling were increased in drier seasons. Monocyte counts and anti-anthrax antibody titers were negatively associated with wet season eosinophilia, and monocytes were negatively correlated with IgGb and IgE titers. Taken together, this supports the hypothesis that ENP wet seasons are characterized by immune resource allocation toward Th-2 type responses, while Th1-type immunity may prevail in drier seasons, and that hosts may experience Th1-Th2 trade-offs. We found evidence that this Th2-type resource allocation is likely driven by GI parasite infections, and that these trade-offs may render hosts less capable of concurrently mounting effective Th1-type immune responses against anthrax.

Conclusions

This study is one of the first to examine laboratory-demonstrated Th1-Th2 trade-offs in a natural system. It provides evidence that seasonally bound pathogens may affect, through immunology, transmission dynamics of pathogens that might otherwise not be seasonally distributed. It suggests that, by manipulating the internal host ecosystem, GI parasites may influence the external ecosystem by affecting the dynamics of another environmentally transmitted pathogen.

Electronic supplementary material

The online version of this article (doi:10.1186/s12898-014-0027-3) contains supplementary material, which is available to authorized users.

Mycobacterium bovis BCG infection severely delays Trichuris muris expulsion and co-infection suppresses immune responsiveness to both pathogens

BACKGROUND

The global epidemiology of parasitic helminths and mycobacterial infections display extensive geographical overlap, especially in the rural and urban communities of developing countries. We investigated whether co-infection with the gastrointestinal tract-restricted helminth, Trichuris muris, and the intracellular bacterium, Mycobacterium bovis (M. bovis) BCG, would alter host immune responses to, or the pathological effect of, either infection.

RESULTS

We demonstrate that both pathogens are capable of negatively affecting local and systemic immune responses towards each other by modifying cytokine phenotypes and by inducing general immune suppression. T. muris infection influenced non-specific and pathogen-specific immunity to M. bovis BCG by down-regulating pulmonary TH1 and Treg responses and inducing systemic TH2 responses. However, co-infection did not alter mycobacterial multiplication or dissemination and host pulmonary histopathology remained unaffected compared to BCG-only infected mice. Interestingly, prior M. bovis BCG infection significantly delayed helminth clearance and increased intestinal crypt cell proliferation in BALB/c mice. This was accompanied by a significant reduction in systemic helminth-specific TH1 and TH2 cytokine responses and significantly reduced local TH1 and TH2 responses in comparison to T. muris-only infected mice.

CONCLUSION

Our data demonstrate that co-infection with pathogens inducing opposing immune phenotypes, can have differential effects on compartmentalized host immune protection to either pathogen. In spite of local and systemic decreases in TH1 and increases in TH2 responses co-infected mice clear M. bovis BCG at the same rate as BCG only infected animals, whereas prior mycobacterial infection initiates prolonged worm infestation in parallel to decreased pathogen-specific TH2 cytokine production.

Cystic echinococcosis in South Africa: the worst yet to come?

A considerable number of cases of cystic echinococcosis (CE) are reported from South Africa, but the exact epidemiology remains unknown. In addition, southern Africa is one of the global regions worst afflicted by an excessively high HIV- and TB co-endemicity. As deductable from anecdotal observation, the immune modulation caused by all three diseases seems to affect the clinical courses of all of them. Due to the ongoing high HIV and TB infection rates and the long latency period of CE, South Africa may experience increasing numbers of CE with potentially unusual and severe clinical courses due to concomitant immune suppression. The extent of the problem and the additional complexity of appropriate patient care remain to be recognized.

Shortening the 'short-course' therapy- insights into host immunity may contribute to new treatment strategies for tuberculosis

Achieving global control of tuberculosis (TB) is a great challenge considering the current increase in multidrug resistance and mortality rate. Considerable efforts are therefore being made to develop new effective vaccines, more effective and rapid diagnostic tools as well as new drugs. Shortening the duration of TB treatment with revised regimens and modes of delivery of existing drugs, as well as development of new antimicrobial agents and optimization of the host response with adjuvant immunotherapy could have a profound impact on TB cure rates. Recent data show that chronic worm infection and deficiencies in micronutrients such as vitamin D and arginine are potential areas of intervention to optimize host immunity. Nutritional supplementation to enhance nitric oxide production and vitamin D-mediated effector functions as well as the treatment of worm infection to reduce immunosuppressive effects of regulatory T (Treg) lymphocytes may be more suitable and accessible strategies for highly endemic areas than adjuvant cytokine therapy. In this review, we focus mainly on immune control of human TB, and discuss how current treatment strategies, including immunotherapy and nutritional supplementation, could be optimized to enhance the host response leading to more effective treatment.

Immunological mechanisms by which concomitant helminth infections predispose to the development of human tuberculosis

Helminthic infections afflict over 1.5 billion people worldwide, while Mycobacterium tuberculosis infects one third of the world's population, resulting in 2 million deaths per year. Although tuberculosis and helminthic infections coexist in many parts of the world, and it has been demonstrated that the T-helper 2 and T-regulatory cell responses elicited by helminths can affect the ability of the host to control mycobacterial infection, it is still unclear whether helminth infections in fact affect tuberculosis disease. In this review article, current progress in the knowledge about the immunomodulation induced by helminths to diminish the protective immune responses to bacille Calmette-Guerin vaccination is reviewed, and the knowledge about the types of immune responses modulated by helminths and the consequences for tuberculosis are summarized. In addition, recent data supporting the significant reduction of both M. tuberculosis antigen-specific Toll-like receptor (TLR) 2 and TLR9 expression, and pro-inflammatory cytokine responses to TLR2 and TLR9 ligands in individuals with M. tuberculosis and helminth co-infection were discussed. This examination will allow to improve understanding of the immune responses to mycobacterial infection and also be of great relevance in combating human tuberculosis.

The impact of asymptomatic helminth co-infection in patients with newly diagnosed tuberculosis in north-west Ethiopia

BACKGROUND

Areas endemic of helminth infection, tuberculosis (TB) and HIV are to a large extent overlapping. The aim of this study was to assess the impact of asymptomatic helminth infection on the immunological response among TB patients with and without HIV, their house hold contacts and community controls.

METHODOLOGY

Consecutive smear positive TB patients (n = 112), their household contacts (n = 71) and community controls (n = 112) were recruited in Gondar town, Ethiopia. Stool microscopy, HIV serology, serum IgE level, eosinophil and CD4 counts were performed and tuberculosis patients were followed up for 3 months after initiation of anti-TB treatment.

RESULTS

Helminth co-infection rate was 29% in TB patients and 21% in both community control and household contacts (p = 0.3) where Ascaris lumbricoides was the most prevalent parasite. In TB patients the seroprevalence of HIV was 47% (53/112). Eosinophilia and elevated IgE level were significantly associated with asymptomatic helminth infection. During TB treatment, the worm infection rate of HIV+/TB patients declined from 31% (10/32) at week 0 to 9% (3/32) at week 2 of TB treatment, whereas HIV-/TB patients showed no change from baseline to week 2, 29% (13/45) vs. 22.2% (10/45). This trend was stable at week 8 and 12 as well.

CONCLUSION

One third of smear positive TB patients were infected with helminths. Eosinophilia and elevated IgE level correlated with asymptomatic worm infection, indicating an effect on host immunity. The rate of worm infection declined during TB treatment in HIV+/TB co-infected patients whereas no decline was seen in HIV-/TB group.

Prevalence and management of helminthiasis among underfives living with HIV/AIDS at Amana Hospital, Tanzania

OBJECTIVE

This was a cross-sectional study intended to assess the prevalence and management of helminthiasis (HL) among underfives living with HIV/AIDS (ULHA).

METHODOLOGY

Clinical histories of ULHA were scrutinized for HIV/AIDS status, antiretroviral therapy (ART), HL prevalence, and their management.

RESULTS

About 364 ULHA were studied, 213 (58.5%) were girls and 151 (41.5%) were boys. Of the 364 ULHA, 171 (47.5%) had HL and 64.3% were treated with albendazole (ABZ). Trichuriasis was ascribed to 23.6% of HL. Majority (72.5%) of ULHA had a CD4 count below 200 cells/mm³. Direct association was observed between CD4 counts and HL. About 55% ULHA were on lamivudine (3TC)-stavudine (d4T)-nevirapine (NVP; LSN) combination therapy. The ABZ-LSN combination was frequently used for HIV/AIDS and HL management.

CONCLUSION

High prevalence of HL and vivid correlation between HIV status and HL were observed. The LSN-ABZ combination was frequently employed for management of HIV/AIDS and HL. We recommended prompt diagnosis of HL to avoid acceleration of HIV infection to AIDS.

Assessment of the impact of adherence and other predictors during HAART on various CD4 cell responses in resource-limited settings

OBJECTIVE

The aim of this study was to quantify, by modeling, the impact of significant predictors on CD4 cell response during antiretroviral therapy in a resource-limited setting.

METHODS

Modeling was used to determine which antiretroviral therapy response predictors (baseline CD4 cell count, clinical state, age, and adherence) significantly influence immunological response in terms of CD4 cell gain compared to a reference value at different periods of monitoring.

RESULTS

At 6 months, CD4 cell response was significantly influenced by baseline CD4 count alone. The probability of no increase in CD4 cells was 2.6 higher in patients with a baseline CD4 cell count of ≥200/mm(3). At 12 months, CD4 cell response was significantly influenced by both baseline CD4 cell count and adherence. The probability of no increase in CD4 cells was three times higher in patients with a baseline CD4 cell count of ≥200/mm(3) and 0.15 times lower with adherent patients. At 18 months, CD4 cell response was also significantly influenced by both baseline CD4 cell count and adherence. The probability of no increase in CD4 cells was 5.1 times higher in patients with a baseline CD4 cell count of ≥200/mm(3) and 0.28 times lower with adherent patients. At 24 months, optimal CD4 cell response was significantly influenced by adherence alone. Adherence increased the probability (by 5.8) of an optimal increase in CD4 cells. Age and baseline clinical state had no significant influence on immunological response.

CONCLUSION

The relationship between adherence and CD4 cell response was the most significant compared to that of baseline CD4 cell count. Counseling before initiation of treatment and educational therapy during follow-up must always help to strengthen adherence and optimize the efficiency of antiretroviral therapy in a resource-limited setting.

High T-cell immune activation and immune exhaustion among individuals with suboptimal CD4 recovery after 4 years of antiretroviral therapy in an African cohort

BACKGROUND

Antiretroviral therapy (ART) partially corrects immune dysfunction associated with HIV infection. The levels of T-cell immune activation and exhaustion after long-term, suppressive ART and their correlation with CD4 T-cell count reconstitution among ART-treated patients in African cohorts have not been extensively evaluated.

METHODS

T-cell activation (CD38+HLA-DR+) and immune exhaustion (PD-1+) were measured in a prospective cohort of patients initiated on ART; 128 patient samples were evaluated and subcategorized by CD4 reconstitution after long-term suppressive treatment: Suboptimal [median CD4 count increase 129 (-43-199) cells/μl], N = 34 ], optimal [282 (200-415) cells/μl, N = 64] and super-optimal [528 (416-878) cells/μl, N = 30].

RESULTS

Both CD4+ and CD8 T-cell activation was significantly higher among suboptimal CD4 T-cell responders compared to super-optimal responders. In a multivariate model, CD4+CD38+HLADR+ T-cells were associated with suboptimal CD4 reconstitution [AOR, 5.7 (95% CI, 1.4-23, P = 0.014)]. T-cell exhaustion (CD4+PD1+ and CD8+PD1+) was higher among suboptimal relative to optimal (P < 0.001) and super-optimal responders (P < 0.001). T-cell exhaustion was significantly associated with suboptimal responders [AOR, 1.5 (95%CI, 1.1-2.1), P = 0.022].

CONCLUSION

T-cell activation and exhaustion persist among HIV-infected patients despite long-term, sustained HIV-RNA viral suppression. These immune abnormalities were associated with suboptimal CD4 reconstitution and their regulation may modify immune recovery among suboptimal responders to ART.

The health implications of wastewater reuse in vegetable irrigation: a case study from Malamulele, South Africa

Malamulele is located in an arid region where small-scale irrigation with wastewater is rife. A study was conducted to investigate the health implications of wastewater reuse in vegetable irrigation. Results showed that there are potential health hazards associated with this practice. The wastewater contained 103 helminth eggs/100 ml and zero helminth eggs for control group; vegetable wash water had 3 helminth eggs/100 ml for the exposed group and zero for control. The wastewater results exceeded the WHO guidelines whereas the vegetable wash water counts were within the guideline. Stool samples of farmers and their children indicated common infections with hookworm and Giardia lamblia. Hookworm infections were high (42%) among exposed group in comparison to the control group (27.5%). The farmers were able derive their livelihood from the sale of vegetables. The findings suggest that the health risks of using wastewater are real but can be managed by using the incomes that the farmers earn.

Regulation of type 1 diabetes, tuberculosis, and asthma by parasites

Helminth infection is a worldwide health problem. In addition to directly causing disease, helminthic infection also affects the incidence and progression of other diseases by exerting immune modulatory effects. In animal models, infection with helminthic parasites can prevent autoimmune diseases and allergic inflammatory diseases, but worsens protective immunity to certain infectious pathogens. In this review, we summarize current findings regarding the effects of helminth infection on type 1 diabetes, tuberculosis, and asthma and discuss possible mechanisms through which helminthic parasites modulate host immunity. Investigating these mechanisms could lead to treatment strategies that specifically modulate the immune response as well as address fundamental questions in immunobiology.

Do antenatal parasite infections devalue childhood vaccination?

On a global basis, both potent vaccine efficacy and high vaccine coverage are necessary to control and eliminate vaccine-preventable diseases. Emerging evidence from animal and human studies suggest that neglected tropical diseases (NTDs) significantly impair response to standard childhood immunizations. A review of efficacy and effectiveness studies of vaccination among individuals with chronic parasitic infections was conducted, using PUBMED database searches and analysis of data from the authors' published and unpublished studies. Both animal models and human studies suggest that chronic trematode, nematode, and protozoan infections can result in decreased vaccine efficacy. Among pregnant women, who in developing countries are often infected with multiple parasites, soluble parasite antigens have been shown to cross the placenta and prime or tolerize fetal immune responses. As a result, antenatal infections can have a significant impact on later vaccine responses. Acquired childhood parasitic infections, most commonly malaria, can also affect subsequent immune response to vaccination. Additional data suggest that antiparasite therapy can improve the effectiveness of several human vaccines. Emerging evidence demonstrates that both antenatal and childhood parasitic infections alter levels of protective immune response to routine vaccinations. Successful antiparasite treatment may prevent immunomodulation caused by parasitic antigens during pregnancy and early childhood and may improve vaccine efficacy. Future research should highlight the varied effects that different parasites (alone and in combination) can have on human vaccine-related immunity. To optimize vaccine effectiveness in developing countries, better control of chronic NTDs may prove imperative.

Immune homeostasis in the respiratory tract and its impact on heterologous infection

Innate immunity at mucosal surfaces requires additional restraint to prevent inflammation to innocuous antigens or commensal microorganisms. The threshold above which airway macrophages become activated is raised by site-specific factors including the receptors for transforming growth factor beta, interleukin 10 and CD200; the ligands for which are produced by, or expressed on, respiratory epithelium. We discuss such site-specific regulation and how this is continually altered by prior infections. Resetting of innate reactivity represents a strategy for limiting excessive inflammation, but in some may pre-dispose to secondary bacterial pneumonia.

Sub-optimal CD4 reconstitution despite viral suppression in an urban cohort on antiretroviral therapy (ART) in sub-Saharan Africa: frequency and clinical significance

BACKGROUND

A proportion of individuals who start antiretroviral therapy (ART) fail to achieve adequate CD4 cell reconstitution despite sustained viral suppression. We determined the frequency and clinical significance of suboptimal CD4 reconstitution despite viral suppression (SO-CD4) in an urban HIV research cohort in Kampala, Uganda.

METHODS

We analyzed data from a prospective research cohort of 559 patients initiating ART between 04/04-04/05. We described the patterns of SO-CD4 both in terms of:- I) magnitude of CD4 cell increase (a CD4 count increase < 50 CD4 cells/microl at 6 months, <100 cells/microl at 12 months; and <200 cells/microl at 24 months of ART) and II) failure to achieve a CD4 cell count above 200 cells/microl at 6,12 and 24 months of ART. Using criteria I) we used logistic regression to determine the predictors of SO-CD4. We compared the cumulative risk of clinical events (death and/or recurrent or new AIDS-defining illnesses) among patients with and without SO-CD4.

RESULTS

Of 559 patients initiating ART, 386 (69%) were female. Median (IQR) age and baseline CD4 counts were 38 yrs (33-44) and 98 cells/microl (21-163) respectively; 414 (74%) started a d4T-based regimen (D4T+3TC+NVP) and 145 (26%) a ZDV-based regimen (ZDV+3TC+EFV). After 6, 12 and 24 months of ART, 380 (68%), 339 (61%) and 309 (55%) had attained and sustained HIV-RNA viral suppression. Of these, 78 (21%), 151 (45%) and 166 (54%) respectively had SO-CD4 based on criteria I), and 165(43%), 143(42%) and 58(19%) respectively based on criteria II). With both criteria combined, 56 (15%) and 129 (38%) had SO-CD4 at 6 and 12 months respectively. A high proportion (82% and 58%) of those that had SO-CD4 at 6 months (using criteria I) maintained SO-CD4 at 12 and 24 months respectively. There were no statistically significant differences in the incidence of clinical events among patients with [19/100PYO (12-29)] and without SO-CD4 [23/100PYO (19-28)].

CONCLUSION

Using criteria I), the frequency of SO-CD4 was 21% at 6 months. Majority of patients with SO-CD4 at 6 months maintained SO-CD4 up to 2 years. We recommend studies of CD4 T-cell functional recovery among patients with SO-CD4.

Efficacy of different chemotherapeutic schemes for hookworm-infected villagers in China

A comparative analysis has been made of the efficacy of different chemotherapeutic schemes against hookworm infections in China. Hookworm eggs were detected by the improved Kato's thick smear method. Benzimidazole was offered to residents in the tested villages, while NaHCO3 was used as placebo in control villages. Data were analysed by negative binomial distribution with statistic software R2.2.1. In the tested village as a result of the application of selective chemotherapy, hookworm infection rate decreased from 58.79% to 1.08%, while the average of eggs per gram (EPG) reduced from 526.29 to 56.91. The infection rates in the target chemotherapy village and in the mass chemotherapy village declined from 6.90% to 1.92% and 10.10% to 0.65% respectively. It was concluded that the consecutive selective chemotherapy could rapidly decrease the infection rate and EPG of hookworm and maintain the infection rate at low level. The curative effect of the target chemotherapy was similar to that of the mass chemotherapy in the low hookworm endemic area.

Controlling soil-transmitted helminthiasis in pre-school-age children through preventive chemotherapy

Pre-school age children account for 10%–20% of the 2 billion people worldwide who are infected with soil-transmitted helminths (STHs): Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm), and Ancylostoma duodenale/Necator americanus (hookworms). Through a systematic review of the published literature and using information collated at World Health Organization headquarters, this paper summarizes the available evidence to support the recommendation that pre-school children should be included in regular deworming programmes. The first section describes the burden of STH disease in this age group, followed by a summary of how infection impacts iron status, growth, vitamin A status, and cognitive development and how STHs may exacerbate other high mortality infections. The second section explores the safety of the drugs themselves, given alone or co-administered, drug efficacy, and the importance of safe administration. The third section provides country-based evidence to demonstrate improved health outcomes after STH treatment. The final section provides country experiences in scaling up coverage of pre-school children by using other large scale public health interventions, including vitamin A programmes, immunization campaigns, and Child Health days. The paper concludes with a number of open research questions and a summary of some of the operational challenges that still need to be addressed.

HIV and parasitic co-infections in tuberculosis patients: a cross-sectional study in Mwanza, Tanzania

A cross-sectional study was conducted in Mwanza, Tanzania, to determine the burden of HIV and parasitic co-infections among patients who were confirmed or suspected cases of pulmonary tuberculosis (PTB). Of the 655 patients investigated, 532 (81.2%) had been confirmed as PTB cases, by microscopy and/or culture (PTB+), whereas the other 123 (18.8%) were only suspected cases, on the basis of other clinical criteria (PTB-). Hookworm and Schistosoma mansoni infections were common in the patients, with prevalences of 18% and 34%, respectively. Malarial, Ascaris lumbricoides, Trichuris trichiura and Strongyloides stercoralis infections were less common, each recorded at a prevalence of <5%. The PTB+ patients were less likely to be HIV-positive than the PTB- patients (43.6% v. 62.6%; P<0.0001). Among the PTB+ patients, the HIV-positive had a significantly lower prevalence (12.1% v. 25%; P<0.0001) and mean intensity (49 v. 123 eggs/g; P=0.003) of hookworm infection than the HIV-negative. The PTB patients in the study area were, however, still frequently co-infected with HIV and with parasitic infections that may increase morbidity and accelerate the progression of HIV disease.

Immunohistochemical diagnosis of abdominal and lymph node tuberculosis by detecting Mycobacterium tuberculosis complex specific antigen MPT64

Background

The aim of this study was to evaluate the diagnostic potential of immunohistochemistry using an antibody to the secreted mycobacterial antigen MPT64, in abdominal and lymph node tuberculosis.

Methods

We used formalin-fixed histologically diagnosed abdominal tuberculosis (n = 33) and cervical tuberculous lymphadenitis (n = 120) biopsies. These were investigated using a combination of Ziehl-Neelsen method, culture, immunohistochemistry with an antibody to MPT64, a specific antigen for Mycobacterium tuberculosis complex organisms. Abdominal and cervical lymph node biopsies from non-mycobacterial diseases (n = 50) were similarly tested as negative controls. Immunohistochemistry with commercially available anti-BCG and nested PCR for IS6110 were done for comparison. Nested PCR was positive in 86.3% cases and the results of all the tests were compared using nested PCR as the gold standard.

Results

In lymph node biopsies, immunohistochemistry with anti-MPT64 was positive in 96 (80%) cases and 4 (12.5%) controls and with anti-BCG 92 (76.6%), and 9 (28%) respectively. The results for cases and controls in abdominal biopsies were 25 (75.7%) and 2 (11.1%) for anti-MPT64 and 25 (75.7%) and 4 (22%) for anti-BCG. The overall sensitivity, specificity, positive and negative predictive values of immunohistochemistry with anti-MPT64 was 92%, 97%, 98%, and 85%, respectively while the corresponding values for anti-BCG were 88%, 85%, 92%, and 78%.

Conclusion

Immunohistochemistry using anti-MPT64 is a simple and sensitive technique for establishing an early and specific diagnosis of M. tuberculosis infection and one that can easily be incorporated into routine histopathology laboratories.

Chronic helminth infections may negatively influence immunity against tuberculosis and other diseases of public health importance

Tuberculosis (TB) has once again become a major public health threat owing to the combined effects of deteriorating socioeconomic situations and the emergence of the HIV/AIDS pandemic. The only vaccine available against TB, although effective in reducing the burden of childhood TB, shows enormous variability in its efficacy against pulmonary TB, which is the most common form of the disease in adults. Most areas of high TB incidence and poor TB vaccine efficacy have a high prevalence of intestinal helminth infections. Such infections have been shown to cause a range of immunomodulation characterized by enhanced T helper 2-type cytokine profile, high immunoglobulin E levels and upregulated regulatory T-cell activity, as well as chronic immune activation. An altered background immune profile could have adverse effects on the outcome of subsequent infections and vaccinations. In support of this hypothesis, studies conducted in animals and humans living in worm-endemic areas have shown that helminths impair resistance against a number of infections of major public health importance, including TB, malaria and HIV/AIDS. Understanding such interactions could assist in the design of vaccines against these diseases.

Impairment of dendritic cell function by excretory-secretory products: A potential mechanism for nematode-induced immunosuppression

To determine whether helminth-derived products modulate dendritic cell (DC) function, we investigated the effects of excretory-secretory products (ES) and adult worm homogenate (AWH) derived from the gastrointestinal nematode Heligmosomoides polygyrus (Hp) on murine bone marrow-derived DC (BMDC). Compared to the TLR9 ligand CpG, Hp-derived products alone failed to induce DC activation. ES, but not AWH, inhibited BMDC cytokine and chemokine production and co-stimulatory molecule expression (CD40, CD86 and MHC class II) induced by TLR ligation. TLR ligand-independent, PMA-induced DC activation was unaffected by ES. Recipients of ES-treated BMDC pulsed with OVA had suppressed Ab responses in vivo, irrespective of the Th1 or Th2 isotype affiliation, compared to recipients of control OVA-pulsed BMDC. Importantly, suppression occurred even in the presence of the potent type 1 adjuvant CpG. In contrast to untreated OVA-pulsed BMDC, ES-treated BMDC pulsed with OVA had reduced co-stimulatory molecule and cytokine expression. CD4(+)CD25(+)Foxp3(-) T cells, which secreted high IL-10 levels, were generated in co-cultures of OT-II OVA-specific TCR-transgenic CD4(+) T cells and ES-treated BMDC. These IL-10-secreting T cells suppressed effector CD4(+) T cell proliferation and IFN-gamma production, the latter effect mediated by an IL-10-dependent mechanism. Together, these results demonstrate that nematode ES impaired DC function and suppressed both Th1 and Th2 adaptive immune responses possibly by inducing regulatory T cells.

HIV and helminth co-infection: is deworming necessary?

We have previously suggested that helminth infections play a major role in the pathogenesis of HIV-1 infection in Africa and other developing areas, due to their profound effects on the host immune system, which make those infected more susceptible to HIV-1 infection and less able to cope with it. Chronic immune activation with a dominant Th2 profile, and anergy, are the hallmarks of chronic helminth infection, and may therefore account for most of these effects. In the present review, we summarize the studies that have addressed these issues and argue that despite some conflicting results, the cumulative immunological and epidemiological evidence is in favour of deworming as a preventive and possible therapeutic measure vis-à-vis HIV-1 infection. We suggest that it should be at least tested on a wider and larger scale than has been done until now, because of its immense potential impact on the still raging AIDS epidemic in developing countries.

Helminthes could influence the outcome of vaccines against TB in the tropics

Helminthes, infections widespread in the tropics, are known to elicit a wide range of immunomodulation characterized by dominant Th2 type immune responses, chronic immune activation as well as up-regulated regulatory T cell activity. Such a wide range of immunomodulation caused by helminthes may have an impact on the host's ability to cope with subsequent infections and/or may affect the efficacy of vaccination. Indeed studies conducted in humans living in helminth-endemic areas and in animal models showed that helminth infection makes the host more permissive to mycobacterial infections and less able to benefit from vaccination. These observations have fundamental practical consequences if confirmed by large and appropriately controlled clinical studies. Eradication of worms could offer an affordable, simple and novel means to reduce the burden of the tuberculosis problem that at the moment seems to be getting out of control in sub-Saharan Africa. This information would also be of great relevance in the design of vaccines against diseases of major public health importance, including malaria and HIV/AIDS.

Amelioration of influenza-induced pathology in mice by coinfection with Trichinella spiralis

Illness due to respiratory virus infection is often induced by excessive infiltration of cells into pulmonary tissues, leading to airway occlusion. We show here that infection with Trichinella spiralis results in lower levels of tumor necrosis factor in bronchoalveolar lavage fluid and inhibits cellular recruitment into the airways of mice coinfected with influenza A virus. Infiltration of neutrophils and CD4+ and CD8+ lymphocytes was reduced, resulting in animals gaining weight more rapidly following the initial phase of infection. Influenza resulted in a generalized increase in vascular permeability in pulmonary tissues, and this was suppressed by parasite infection, although the effects were restricted to the early phase of trichinosis. Moreover, the number of cells producing interleukin-10 (IL-10), and the local levels of this cytokine, were reduced, suggesting that amelioration of pulmonary pathology by parasite infection occurs independently of IL-10 production.

Reduced protective efficacy of a blood-stage malaria vaccine by concurrent nematode infection

Helminth infections, which are prevalent in areas where malaria is endemic, have been shown to modulate immune responses to unrelated pathogens and have been implicated in poor efficacy of malaria vaccines in humans. We established a murine coinfection model involving blood-stage Plasmodium chabaudi AS malaria and a gastrointestinal nematode, Heligmosomoides polygyrus, to investigate the impact of nematode infection on the protective efficacy of a malaria vaccine. C57BL/6 mice immunized with crude blood-stage P. chabaudi AS antigen in TiterMax adjuvant developed strong protection against malaria challenge. The same immunization protocol failed to induce strong protection in H. polygyrus-infected mice. Immunized nematode-infected mice produced significantly lower levels of malaria-specific antibody than nematode-free mice produced. In response to nematode and malarial antigens, spleen cells from immunized nematode-infected mice produced significantly lower levels of gamma interferon but more interleukin-4 (IL-4), IL-13, and IL-10 in vitro than spleen cells from immunized nematode-free mice produced. Furthermore, H. polygyrus infection also induced a strong transforming growth factor beta1 response in vivo and in vitro. Deworming treatment of H. polygyrus-infected mice before antimalarial immunization, but not deworming treatment after antimalarial immunization, restored the protective immunity to malaria challenge. These results demonstrate that concurrent nematode infection strongly modulates immune responses induced by an experimental malaria vaccine and consequently suppresses the protective efficacy of the vaccine against malaria challenge.

Increased TGF-beta, Cbl-b and CTLA-4 levels and immunosuppression in association with chronic immune activation

In this study we investigated the mechanisms mediating T-cell hyporesponsiveness in chronically immune-activated individuals. We analyzed in healthy and persistently helminth-infected individuals the relationship between immune activation and general T-cell hyporesponsiveness, Th3/regulatory T-cell expression, transforming growth factor-beta (TGF-beta) secretion, CTL-associated antigen 4 (CTLA-4) levels, Casitas B-cell lymphoma-b (Cbl-b) (a negative regulator of T-cell activation) levels and phosphorylation of mitogen-activated protein kinases/extracellular signal-regulated kinase (ERK)-1 and -2. We found a very significant increase in plasma levels of TGF-beta and intracellular pools of CTLA-4 and Cbl-b in association with immune activation, which correlates with decreased T-cell responses to anti-CD3 stimulation. We demonstrate that the impaired activity of ERK of peripheral T cells in highly immune-activated individuals is associated with increased levels of CTLA-4 and Cbl-b. Interestingly, in some, but not in all, of these immune-activated individuals, induction of Cbl-b intracellular pools occurs by TGF-beta or CTLA-4 stimulation. We suggest that the higher levels of CTLA-4 and TGF-beta, both involved in the induction of Cbl-b, point at potential mechanisms underlying general and antigen-specific immune hyporesponsiveness in chronically infected individuals.

Incorporating a rapid-impact package for neglected tropical diseases with programs for HIV/AIDS, tuberculosis, and malaria

Hotez et al. argue that achieving success in the global fight against HIV/AIDS, tuberculosis, and malaria may well require a concurrent attack on the neglected tropical diseases.

HIV-1 burden influences host response to co-infection with Neisseria gonorrhoeae in vitro

There is considerable evidence that co-infection with the sexually transmitted pathogen Neisseria gonorrhoeae (Gc) can increase the likelihood of both transmitting and acquiring HIV-1 worldwide. However, less information is available on how host immune response to co-infection differs with immune response to HIV-1 infection alone. To evaluate HIV-1 burden effects on host response to co-infection with Gc, we performed gene-expression profiling of human PBMCs infected over a broad range of viral titers (HIV-1 series) and upon exposure to a single infectious dose of Gc (HIV-1/Gc series). The transcriptional profiles differed substantially between each series (P < 0.0001). Major shifts in the transcriptional landscape were identified in contour plots based on fold stimulation and hierarchical clustering. Prominent regions of transcriptional activity were evaluated for statistical enrichment to identify up-regulated pathways associated with immune response, infection and T-cell stimulation. Notably, gene enrichment was dependent on HIV-1 burden and shifted during co-infection to reveal a disproportionate effect on lymphocyte signaling, apoptosis and proteasome activity. Further evaluation of these findings may help to better understand the role of viral burden in defining cellular contribution to host immune response upon co-infection with secondary sexually transmitted pathogens.

TLR9 expression is related to immune activation but is impaired in individuals with chronic immune activation

Millions of individuals in developing countries are infected with helminths and other chronic infectious diseases, such as HIV-1, which lead to persistent immune activation and unbalanced immune state. We have suggested that the capacity of chronically immune activated individuals to protect themselves, cope with infections, and mount protective immunity following vaccination, is highly impaired. Here we examined the expression of toll-like receptor 9 (TLR9), as an essential component in the recognition of immunostimulating bacterial CpG-DNA motifs, in different subsets of human peripheral blood mononuclear cells (PBMC) obtained from chronically immune activated and non-activated individuals. TLR9 expression was correlated to immune cell activation and was upregulated following phytohemagglutinin or anti-CD3 activation. PBMC obtained from chronically immune activated individuals had a different overall pattern of TLR9 expression, including reduced upregulation of this receptor following additional immune activation, and diminished responsiveness to CpG-DNA stimulation, in comparison to non-activated individuals. These differences may partly account for the reduced capacity of chronically immune activated individuals to mount effective immune responses and strengthen the notion that the host immune background should be considered in the design and trial of potential adjuvants and vaccines.

HUMAN RIGHTS, BIOMEDICAL SCIENCE, AND INFECTIOUS DISEASES AMONG SOUTH AMERICAN INDIGENOUS GROUPS

Despite the efforts of international health agencies to reduce global health inequalities, indigenous populations around the world remain largely unaffected by such initiatives. This chapter reviews the biomedical literature indexed by the PubMed database published between 1963 and 2003 on South American indigenous populations, a total of 1864 studies that include 63,563 study participants. Some language family groupings are better represented than are others, and lowland groups are better represented than are highland groups. Very few studies focus on major health threats (e.g., tuberculosis, influenza), public health interventions, or mestizo-indigenous epidemiological comparisons. The prevalence rates of three frequently studied infections—parasitism, human T-cell lymphotropic viral infection (HTLV), and hepatitis—are extraordinarily high, but these facts have been overlooked by national and international health agencies. This review underscores the urgent need for interventions based on known disease prevalence rates to reduce the burden of infectious diseases in indigenous communities.

Can worms defend our hearts? Chronic helminthic infections may attenuate the development of cardiovascular diseases

The established risk factors for atherosclerosis fail to fully explain the extent and severity of coronary artery diseases in 50% of the patients. Thus, the causative agents and processes, which may be involved in the pathogenesis of atherosclerosis, are being sought. Notoriously, atherosclerosis and cardiovascular event rates are much lower in developing countries. Clinically, severe infections by intracellular pathogens are widespread mostly in developing countries with poor sanitation, nutrition and massive worm infections. A link between atherosclerosis and helminth infections has never been examined. Based on the present knowledge of immune and infectious mechanisms related to atherosclerosis, it is proposed that chronic helminthic infections can have a significant bearing on the epidemiology of cardiovascular diseases. How can helminthic infections affect the cardiovascular risk? (1) Helminths evade or suppress host immune responses, by producing anti-inflammatory and other immunomodulatory molecules. (2) Helminths induce chronic Th2 activation, which can modify cytokine profiles and immunological responses to heat shock proteins, Chlamydia pneumoniae and cytomegalovirus. (3) The chronic Th2 profile may modulate monocyte activation and chemotaxis to inflammatory sites (atherosclerotic plaques). (4) Chronic Th2 activation may lead to a cytokine profile that could be beneficial for attenuation of atherosclerosis development (upregulation of IL-4, IL-10 and IL-13 and downregulation of proinflammatory cytokines). (5) Helminthic infections may reduce plasma LDL level not only by affecting the host nutrition, but also via modulation of naturally occurring antibodies to cholesterol. Studies are needed to clarify these suggestions. If the hypothesis that helminthic infections impact atherosclerosis is correct, it should be taken into consideration in atherosclerosis immunomodulation therapy and especially in the design of vaccines and vaccine trials.

Regulation of allergy and autoimmunity in helminth infection

Parasitic infections are a major theme in the "hygiene hypothesis", as allergies and autoimmune diseases are less prevalent in countries with higher burdens of helminths and other parasitic organisms. Helminths"-the grouping of multicellular worm parasites including nematodes, cestodes and trematodes-tend to establish long-lived, chronic infections indicating successful down-modulation of the host immune system. In this review, we describe the intricate immunology of host-helminth interactions and how parasites manipulate immune responses to enhance their survival. In so doing, they often minimise immunopathology and, it is suggested, reduce host susceptibility to, and severity of allergic and autoimmune diseases. Studies on helminth-infected communities and individuals support the hypothesis that an immuno-regulatory network promoted by parasites extends its influence to limiting allergies. Experimental models are now probing more deeply into the area of immune modulation by helminths, and we discuss the likely mechanisms by which helminths could be establishing a strongly regulatory environment. Understanding and harnessing the modulatory capacity of helminths may uncover novel therapeutic interventions, mimicking and exploiting their evolution for our benefit. Parasitic infections are a major theme in the "hygiene hypothesis", as allergies and autoimmune diseases are less prevalent in countries with higher burdens of helminths and other parasitic organisms. Helminths"-the grouping of multicellular worm parasites including nematodes, cestodes and trematodes-tend to establish long-lived, chronic infections indicating successful down-modulation of the host immune system. In this review, we describe the intricate immunology of host-helminth interactions and how parasites manipulate immune responses to enhance their survival. In so doing, they often minimise immunopathology and, it is suggested, reduce host susceptibility to, and severity of allergic and autoimmune diseases. Studies on helminth-infected communities and individuals support the hypothesis that an immuno-regulatory network promoted by parasites extends its influence to limiting allergies. Experimental models are now probing more deeply into the area of immune modulation by helminths, and we discuss the likely mechanisms by which helminths could be establishing a strongly regulatory environment. Understanding and harnessing the modulatory capacity of helminths may uncover novel therapeutic interventions, mimicking and exploiting their evolution for our benefit.