Comparative evaluation of four rapid diagnostic tests that detect human Trypanosoma cruzi-specific antibodies to support diagnosis of Chagas Disease in urban population of Argentina

BACKGROUND

Chagas disease (CD), caused by the parasite Trypanosoma cruzi, is the most important endemic anthropozoonosis in Argentina. Since 2010, the World Health Organization has highlighted the urgent need to validate diagnostic systems that allow rapid detection of T. cruzi, infection in primary healthcare centers. Serological rapid diagnostic tests (RDTs) for T. cruzi, infection could be used to improve case management, as RDTs do not require specialized laboratories or highly trained staff to use them. We aimed to generate unbiased performance data of RDTs in Argentina, to evaluate their usefulness for improving T. cruzi, diagnosis rates.

METHODS AND PRINCIPAL FINDINGS

This is a retrospective, laboratory-based, diagnostic evaluation study to estimate the clinical sensitivity/specificity of four commercially available RDTs for T. cruzi, using the Chagas disease diagnostic algorithm currently used in Argentina as the reference standard. In total, 400 serum samples were tested, 200 from individuals with chronic T. cruzi infection and 200 from individuals not infected with T. cruzi. All results were registered as the agreement of at least two operators who were blinded to the reference standard results. The sensitivity estimates ranged from 92.5-100% (95% confidence interval (CI) lower bound 87.9-98.2%); for specificity, the range was 76-96% (95% CI lower bound 69.5-92.3%). Most RDTs evaluated showed performances comparable with the reference standard method, showing almost perfect concordance (Kappa 0.76-0.92).

CONCLUSIONS

Our study demonstrates that, under controlled laboratory conditions, commercially available RDTs for CD have a performance comparable to the Argentinian diagnostic algorithm, which is based on laboratory-based serological tests. For the next stage of our work, the RDTs will be evaluated in real-world settings.

Effectiveness of the repurposed drug isotretinoin in an experimental murine model of Chagas disease

Benznidazole and nifurtimox are the drugs currently used for the treatment of Chagas disease, however its side effects may affect patient adherence. In the search for new alternative therapies, we previously identified isotretinoin (ISO), an FDA-approved drug widely used for the treatment of severe acne through a drug repurposing strategy. ISO shows a strong activity against Trypanosoma cruzi parasites in the nanomolar range, and its mechanism of action is through the inhibition of T. cruzi polyamine and amino acid transporters from the Amino Acid/Auxin Permeases (AAAP) family. In this work, a murine model of chronic Chagas disease (C57BL/6 J mice), intraperitoneally infected with T. cruzi Nicaragua isolate (DTU TcI), were treated with different oral administrations of ISO: daily doses of 5 mg/kg/day for 30 days and weekly doses of 10 mg/kg during 13 weeks. The efficacy of the treatments was evaluated by monitoring blood parasitemia by qPCR, anti-T. cruzi antibodies by ELISA, and cardiac abnormalities by electrocardiography. No parasites were detected in blood after any of the ISO treatments. The electrocardiographic study of the untreated chronic mice showed a significant decrease in heart rate, while in the treated mice this negative chronotropic effect was not observed. Atrioventricular nodal conduction time in untreated mice was significantly longer than in treated animals. Mice treated even with ISO 10 mg/kg dose every 7 days, showed a significant reduction in anti-T. cruzi IgG levels. In conclusion, the intermittent administration of ISO 10 mg/kg would improve myocardial compromise during the chronic stage.

Serological reactivity against T. cruzi-derived antigens: Evaluation of their suitability for the assessment of response to treatment in chronic Chagas disease

Chagas disease, caused by the protozoan Trypanosoma cruzi, affects more than 6 million people worldwide. Following a mostly asymptomatic acute phase, the disease progresses to a long-lasting chronic phase throughout which life-threatening disorders to the heart and/or gastrointestinal tract will manifest in about 30% of those chronically infected. During the chronic phase, the parasitemia is low and intermittent, while a high level of anti-T. cruzi antibodies persist for years. These two features hamper post-chemotherapeutic follow-up of patients with the tools available. The lack of biomarkers for timely assessment of therapeutic response discourages a greater use of the two available anti-parasitic drugs, and complicates the evaluation of new drugs in clinical trials. Herein, we investigated in a blinded case-control study the serological reactivity over time of a group of parasite-derived antigens to potentially address follow up of T. cruzi chronically infected subjects after treatment. We tested PFR2, KMP11, HSP70, 3973, F29 and the InfYnity multiplexed antigenic array, by means of serological assays on a multi-national retrospective collection of samples. Some of the antigens exhibited promising results, underscoring the need for further studies to determine their potential role as treatment response biomarkers.

Prospective multicenter evaluation of real time PCR Kit prototype for early diagnosis of congenital Chagas disease

BACKGROUND

Current algorithm for Congenital Chagas Disease (cCD) diagnosis is unsatisfactory due to low sensitivity of the parasitological methods. Moreover, loss to follow-up precludes final serodiagnosis after nine months of life in many cases. A duplex TaqMan qPCR kit for Trypanosoma cruzi DNA amplification was prospectively evaluated in umbilical cord (UCB) and peripheral venous blood (PVB) of infants born to CD mothers at endemic and non-endemic sites of Argentina.

METHODS

We enrolled and followed-up 370 infants; qPCR was compared to gold-standard cCD diagnosis following studies of diagnostic accuracy guidelines.

FINDINGS

Fourteen infants (3·78%) had cCD. The qPCR sensitivity and specificity were higher in PVB (72·73%, 99·15% respectively) than in UCB (66·67%, 96·3%). Positive and negative predictive values were 80 and 98·73% and 50 and 98·11% for PVB and UCB, respectively. The Areas under the Curve (AUC) of ROC analysis for qPCR and micromethod (MM) were 0·81 and 0·67 in UCB and 0·86 and 0·68 in PVB, respectively. Parasitic loads ranged from 37·5 to 23,709 parasite equivalents/mL. Discrete typing Unit Tc V was identified in five cCD patients and in six other cCD cases no distinction among Tc II, Tc V or Tc VI was achieved.

INTERPRETATION

This first prospective field study demonstrated that qPCR was more sensitive than MM for early cCD detection and more accurate in PVB than in UCB. Its use, as an auxiliary diagnostic tool to MM will provide more accurate records on cCD incidence.

FUNDING

FITS SALUD 001-CHAGAS (FONARSEC, MINCyT, Argentina) to the Public-Private Consortium (INGEBI-CONICET, INP-ANLIS MALBRAN and Wiener Laboratories); ERANET-LAC-HD 328 to AGS and PICT 2015-0074 (FONCYT, MinCyT) to AGS and FA.

Emergency contraception and risk habits in a university population

OBJECTIVE

The aim of our study was to determine the self-reported prevalence of use of emergency contraception (EC), identify factors associated with EC use, and measure the prevalence in university students of pregnancy and abortion among users and non-users of EC.

METHODS

A cross-sectional descriptive study of university students using a self-administered questionnaire was carried out in 2016. The main dependent variable was EC use at any time. Independent variables included sociodemographic factors and factors related to harmful habits and sexual behaviour.

RESULTS

The study sample consisted of 1309 students (median age 20 years). Forty per cent of participants reported using EC; condom failure was given as the main reason. Variables associated with EC use in both men and women were illegal drug consumption and having had more than 10 sexual partners. In women, other factors associated with EC use were age at first coitus and non-centrist political views. The prevalence of pregnancy was 6.5% and the prevalence of voluntary abortion was 2.9%. This prevalence was similar for men and women and for EC users and non-users.

CONCLUSION

EC use in university students was more likely in those who experienced contraceptive failure or used no contraception. There were differences between men and women. Those at higher risk of unplanned pregnancy were more likely to report EC use, which may explain why there was no difference in the rates of unwanted pregnancies between EC users and non-users.

Discourses on the postcoital pill in young women

BACKGROUND

Emergency contraception (EC) is an effective postcoital contraceptive method for reducing the risk of unwanted pregnancy after unprotected intercourse. The estimated effectiveness of EC is between 70 and 89% if taken within 72 h following intercourse. Most of the studies carried out in Spain are quantitative and from the perspective of health professionals. In this study, we intend to explore the knowledge of, attitudes towards and discourse regarding the use of EC in women aged 15 to 25 years.

METHODS

Sample: A qualitative study including in-depth interviews with 19 women between 15 and 25 years of age was performed.

INCLUSION CRITERIA

Participants were natives of Spain or of a Latin American country. Segmentation criteria: Participants had experience in the use of EC.

DATA COLLECTION

Participants were selected by health care informants and by the snowball technique among university students.

DATA ANALYSIS

A thematic analysis was performed. Preliminary analyses were made during the course of the field work to adapt the script and to assess data saturation. A preliminary code tree was developed by two researchers, and the coding of the text was done with the Atlas.ti 5.0 software.

RESULTS

EC is perceived positively by women. They do not express issues with taking it, although some feel guilty. The reason for taking EC is to avoid unwanted pregnancy and abortion. Women also feel that EC should be used in moderation. False beliefs and misconceptions regarding EC are held: EC delivers an excess of hormones, induces abortion and causes severe side effects. Women mention that the health professionals who provide EC have moral beliefs. Women use it because of condom breakage associated with their first coital relations.

CONCLUSIONS

The results of this study have public health implications: The sexual-affective health education received by young people should incorporate clear information about the mechanism of action of the EC pill and its side effects together with empowerment strategies addressing guilt and moralistic messages. Programmes and training activities for health professionals must be designed to prevent the communication of inappropriate messages such as those that exaggerate the side effects of EC and those that promote fear and guilt, because they represent a barrier to the responsible use of this medication.

Evidence of advanced stage colorectal cancer with longer diagnostic intervals: a pooled analysis of seven primary care cohorts comprising 11 720 patients in five countries

Background:

The benefits from expedited diagnosis of symptomatic cancer are uncertain. We aimed to analyse the relationship between stage of colorectal cancer (CRC) and the primary and specialist care components of the diagnostic interval.

Methods:

We identified seven independent data sets from population-based studies in Scotland, England, Canada, Denmark and Spain during 1997–2010 with a total of 11 720 newly diagnosed CRC patients, who had initially presented with symptoms to a primary care physician. Data were extracted from patient records, registries, audits and questionnaires, respectively. Data sets were required to hold information on dates in the diagnostic interval (defined as the time from the first presentation of symptoms in primary care until the date of diagnosis), symptoms at first presentation in primary care, route of referral, gender, age and histologically confirmed stage. We carried out reanalysis of all individual data sets and, using the same method, analysed a pooled individual patient data set.

Results:

The association between intervals and stage was similar in the individual and combined data set. There was a statistically significant convex (∩-shaped) association between primary care interval and diagnosis of advanced (i.e., distant or regional) rather than localised CRC (P=0.004), with odds beginning to increase from the first day on and peaking at 90 days. For specialist care, we saw an opposite and statistically significant concave (∪-shaped) association, with a trough at 60 days, between the interval and diagnosis of advanced CRC (P<0.001).

Conclusions:

This study provides evidence that longer diagnostic intervals are associated with more advanced CRC. Furthermore, the study cannot define a specific ‘safe’ waiting time as the length of the primary care interval appears to have negative impact from day one.

Survivorship care plans in Spain: A need that cannot be postponed

In Spain, as around the world, the number of cancer survivors is increasing. There were an estimated 500,000 cancer survivors in 2010. In spite of recognition that Survivorship Care Plans (SCPs) are needed, their implementation in Spain has been slower than in other countries and only in very recent years some small initiatives have been carried out. This editorial addresses the difficulties to implement SCPs in the Spanish Health Services and which are the opportunities that favour a scenario in which PCPs and oncologists can offer a real patient-centred care to cancer survivors.

Comparative efficacy of two interventions to discontinue long-term benzodiazepine use: cluster randomised controlled trial in primary care

BACKGROUND

Benzodiazepines are extensively used in primary care, but their long-term use is associated with adverse health outcomes and dependence.

AIMS

To analyse the efficacy of two structured interventions in primary care to enable patients to discontinue long-term benzodiazepine use.

METHOD

A multicentre three-arm cluster randomised controlled trial was conducted, with randomisation at general practitioner level (trial registration ISRCTN13024375). A total of 532 patients taking benzodiazepines for at least 6 months participated. After all patients were included, general practitioners were randomly allocated (1:1:1) to usual care, a structured intervention with follow-up visits (SIF) or a structured intervention with written instructions (SIW). The primary end-point was the last month self-declared benzodiazepine discontinuation confirmed by prescription claims at 12 months.

RESULTS

At 12 months, 76 of 168 (45%) patients in the SIW group and 86 of 191 (45%) in the SIF group had discontinued benzodiazepine use compared with 26 of 173 (15%) in the control group. After adjusting by cluster, the relative risks for benzodiazepine discontinuation were 3.01 (95% CI 2.03-4.46, P<0.0001) in the SIW and 3.00 (95% CI 2.04-4.40, P<0.0001) in the SIF group. The most frequently reported withdrawal symptoms were insomnia, anxiety and irritability.

CONCLUSIONS

Both interventions led to significant reductions in long-term benzodiazepine use in patients without severe comorbidity. A structured intervention with a written individualised stepped-dose reduction is less time-consuming and as effective in primary care as a more complex intervention involving follow-up visits.

Factors triggering medical consultation for symptoms of colorectal cancer and perceptions surrounding diagnosis

This study aims to find out how the presenting symptoms of colorectal cancer are interpreted by those who get them, to identify the main triggering factors that lead someone with colorectal cancer symptoms to consult a doctor, and to describe how those affected perceive the process of being diagnosed with colorectal cancer. It is a qualitative study performed within the theoretical framework of symbolic interactionism and from a gender perspective. Grounded theory has been used for the analysis. Semi-structured interviews were conducted. Twelve individuals with colorectal cancer - seven men and five women - were interviewed. At first, both the men and women attributed their symptoms to trivial causes. Changes in symptoms or the persistence of symptoms trigger medical consultation. Close relatives, especially the closest female family members, can trigger medical consultation, particularly among men. The women said nothing to their families until they had already gone to the doctor. Knowledge about colorectal cancer could be a factor triggering medical consultation. The time between consulting the family doctor and seeing a specialist feels drawn out. Gender-related differences have been observed in respect to help-seeking in colorectal cancer. Health education programmes focusing on knowledge about cancer are needed.

[Perception of difficulties in family medicine in the delivery of health to economic immigrants]

OBJECTIVES

To find the problems, as seen by family doctors, in care for immigrants, with description of proposed solutions.

DESIGN

Transversal and descriptive.

PARTICIPANTS

262 doctors from 18 health centres in a district.

MEASUREMENTS

Each professional received a questionnaire containing social and demographic variables, number of immigrants seen per day, their place of origin, 6 items on accessibility, 5 on barriers to care, 6 on clinic, and 7 on solutions.

RESULTS

159 doctors, 57.2% women, replied. Average age was 41.1; 64% saw 2-3 immigrants a day. 52.3% (95% CI, 45.0%-61.4%) recognised that care for immigrants posed professional problems. They said that immigrants attended as an emergency more often (81.1%); they more often had no clinical records (74.7%); and they had difficulties obtaining a health card (53%). 67% expressed no difficulties for getting to the hospital. Perceived barriers were the mobility of immigrants (82.9%), language (82.3%), and culture (71.3%). Solutions suggested were translators (95.6%) or cultural intermediary (82.7%). Clinically, doctors saw no differences of pathology in immigrants (56.7%), and no greater psychiatric pathology (66%). Lack of skill in contagious pathologies hampered care (60.3%). 82.8% affirmed that specific protocols were needed. 80.3% argued for a unit of imported diseases. Among care priorities were information on health circuits and making the health card easier to obtain.

CONCLUSIONS

The difficulties sustained by a broad range of professionals are diverse, with access and linguistic-cultural questions standing out. To palliate them, sensitivity from health staff and action from management are needed.

La salud mental en los médicos de familia: efectos de la satisfacción y el estrés en el trabajo

OBJECTIVES

To asses "burnout" and psychiatric morbidity among family physicians and its relationship with stress and satisfaction at work.

METHODS

The 346 family doctors and 84 pediatricians in the Primary Health Care district of Majorca were invited to fill-out a questionnaire. Psychiatric morbidity was evaluated using the 28-item General Health Questionnaire. The three components of "burnout" (emotional exhaustion, depersonalization and low personal accomplishment) were assessed with the Maslach Burnout inventory. Satisfaction and stress at work were assessed with the Font Roja and Tabarca scales, respectively.

FINDINGS

266 family doctors and pediatricians answered the questionnaire (61.86%). Estimated prevalence of psychiatric morbidity was 25.7%. No significant differences were found between those with GHQ results and demographic and job variables. Fifty three per cent had high emotional exhaustion, 47.1% high depersonalization and low personal accomplishment were found in 33.3% of the doctors. Non significant differences were identified in the distribution of burnout dimensions and demographic and job characteristics. Satisfaction at work seems to protect doctors from mental distress and burnout. Job stress is related to higher emotional exhaustion and depersonalization but not with psychiatric morbidity.

CONCLUSIONS

Family practitioner's mental health is likely to be protected in those who are more satisfied at work and threatened in those doctors with high job stress. These facts have to be assumed not so much as an individual problem but rather as a general problem of all health organizations.

Therapeutic use of muscarinic acetylcholine receptor peptide to prevent mice chagasic cardiac dysfunction

Therapeutic use of a peptide corresponding to the aminoacid sequence of the second extracellular loop of human M2 muscarinic acetylcholine receptor (M2 mAChR peptide) was studied. Expression and biological activity of M2 mAChR in association with circulating M2 mAChR-related antibodies in cardiac tissue from chagasic mice were evaluated. Mice infected or not with trypomastigotes Tulahuen strain either treated or not treated with M2 mAChR peptide were sacrificed at 8-9 weeks post-infection. Morphological, binding and contractility studies were performed on all animal groups. Hearts from infected mice showed a mAChR-related dysfunction, with a decrease in heart contractility, impaired response to exogenous mAChR agonist (carbachol) and a significant reduction of mAChR binding sites. Treating infected mice with M2 mAChR peptide reversed those effects. Moreover, autoantibodies from infected mice recognized the M2 mAChR peptide. In addition, serum from infected mice and the corresponding affinity purified IgG was capable of interacting with cardiac mAChR, reducing the number of binding sites and inhibiting the contractile response to exogenous agonist. In conclusion, (1) the development of alterations in mAChR related to cardiac dysfunction, may be associated with the presence of circulating antibodies against these receptors and (2) the chronic treatment with M2 mAChR peptide prevented infected mice heart dysfunction. The mechanism could be explained by the ability of the M2 mAChR peptide to inhibit the chronic interaction of autoantibodies specific to mAChR. The implication of M2 mAChR peptide treatment in the host's immune response is discussed.

Trypanosoma cruzi: methoprene is a potent agent to sterilize blood infected with trypomastigotes

The effects of methoprene, a juvenile hormone analogue (JHA), on Trypanosoma cruzi bloodstream trypomastigotes (Tulahuen strain, Tul 2 stock) were studied. It was observed that 150microM of methoprene in in vitro experiments cause cellular death of T. cruzi. In contrast, methoprene was not able to clear bloodstream trypomastigotes in in vivo experiments, but it was observed a decrease of parasitemia levels of infected mice treated with 200microg of methoprene/mouse/day during 5 days. According to these results and the low toxicity of methoprene, we suggest that this compound will serve as an effective agent to sterilize blood for transfusions.

[The "quality of life" concept in medical students and postgraduate residents in a university hospital]

We investigated the quality of life's concept and its uses by both residents and interns as well as last year medical students in the University Hospital in Caracas (HUC). A random sample by strata, without replacement of 123 persons, completed a self administered questionnaire which included a set of closed questions and one of open questions related to the quality of life's concept. The mean age was 29 years for both sexes (3.55 standard deviation or SD). There was not a statistically significant difference between males and females. More than 50% read about quality of life in either newspapers, journals and fiction literature. There was no difference among the groups (p = 0.25). Only 68% had heard in a different sort of academical institution the term "quality of life" such as in the school of medicine, highschool or in some discussion groups with no differences among the groups (p = 0.15). However, there was no agreement as from whom and where they learned about quality of life (p < 0.001). Although everybody considered that the quality of life was an important element in medical actions such as diagnostic or therapeutics, its importance was reduced for diagnosis compared to treatment (p < 0.0001). All the elements that were considered as part of the concept were also considered as important, regardless of the group and was statistically significant (p < 0.05). The open question analysis showed that the non-medical definitions represent 85.15% of the group, 50% out of them included terms of potentiality or condition. Among the elements included in the definition was the social in 27.65%, psychological in 23.53% and, the economical in 12.35% of the questionnaires. The great majority of the "quality of life" definitions did not include a clearly defined subject and in many cases it was exclusively related to ill persons. Finally, there is an informal and not well oriented form of learning about "quality of life" in residents, interns and last year medical students with a lack of a good applicability in the medical practice. Therefore, there is a need for a formal training on quality of life along the medical studies and its uses in the medical practice in general and with special emphasis on diagnosis and therapeutics.

Terminal cancer. duration and prediction of survival time

The duration of the terminal period of cancer allows us to determine its prevalence, which is necessary to plan palliative care services. Clinical prediction of survival influences access to palliative care and the healthcare approach to be adopted. The objective of this study was to determine the duration of the terminal period, the prognostic ability of healthcare professionals to predict this terminal period and the factors that can improve the prognostic accuracy. In the island of Mallorca, Spain, we followed 200 cancer patients at the inception of the terminal period. Twenty-one symptoms, quality of life, prognosis and duration of survival were measured. Using a Cox regression model, a predictive survival model was built. Median duration was 59 days; 95% confidence interval (CI)=49-69 days, mean=99 days. The oncologists were accurate in their predictions (+/-1/3 duration) in 25.7% of cases, the nurses in 21.5% of cases and the family physicians in 21.7% of cases. Errors of overestimation occurred 2.86-4.14 times more frequently than underestimation. In the final model, in addition to clinical prognosis (P=0.0094), asthenia (P=0.0257) and the Hebrew Rehabilitation Centre for Aged Quality of Life (HRCA-QL) Index (P=0.0002) were shown to be independent predictors of survival. In this study, the estimated duration of the terminal period was greater than that reported in a series of palliative care programmes, and survival was overestimated. Oncologists could estimate prognosis more accurately if they also take into account asthenia and HRCA-QL Index.

The cytostome of Trypanosoma cruzi epimastigotes is associated with the flagellar complex

Okuda, K., Esteva, M., Segura, E. L., and Bijovsky, A. T. 1999. The cytostome of Trypanosoma cruzi epimastigotes is associated with the flagellar complex. Experimental Parasitology 92, 223-231. Proliferative forms of Trypanosoma cruzi, amastigotes and epimastigotes, have a cytostome, a specialized structure formed by an invagination of the flagellar pocket's membrane surrounded by microtubules and frequently followed by a row of vesicles. All this assemblage penetrates deeply into the cytoplasm overpassing the nucleus. This structure, together with the flagellar pocket, appears to play an important role in the nutrition of the parasite. We demonstrated that the monoclonal antibody 2C4, made-up against isolated flagellar complex of T. cruzi epimastigotes, recognizes a protein doublet of 76 and 87 kDa in total epimastigotes homogenate. The 76-kDa polypeptide is enriched in the detergent-soluble fraction whereas the 87-kDa polypeptide is highly represented in the insoluble fractions and the purified flagella. Immuno-fluorescence assays show the antigen as a small spot at the flagellar pocket region. Immunogold labeling of ultrathin sections of epimastigote forms reveals gold particles at the opening of flagellar pocket, concentrated in the cytostome region. Immunocytochemistry of epimastigote whole-mount cytoskeletons reveals the labeling on an array of three to four microtubules that appears attached to flagellum, running in the direction of the nucleus. Ultrastructural observations have shown that the posterior region of isolated flagella, corresponding to the level of the flagellar pocket, possesses a microtubular structure compatible with that from the cytostome. The relationship between the cytostome, an endocytic organelle, and the flagellum is here described for the first time.

Inhibition of trypomastigotes' infectivity by a monoclonal antibody directed to a glycoconjugated fraction of epimastigotes of Trypanosoma cruzi

In this work it was shown that the infectivity of trypomastigote forms of Trypanosoma cruzi was affected upon the interaction with the Monoclonal Antibody (McAb) 2E9, which was raised against a glycoconjugated fraction of membranes of epimastigotes (Tulahuen strain). Characterization of the epitope recognized by this McAb, as well as its effects on complement mediated lysis and host cell invasion are reported. Immunocytochemical analysis showed that the McAb was reactive with two macromolecules (41-58 kDa) present on Trypanosoma cruzi epimastigotes (Tulahuen and Y strain), while it recognized several trypomastigotes macromolecules, showing a more intense reactivity with a band of 80 kDa. By indirect immunofluorescence, it was found there were subpopulations of blood and tissue culture derived trypomastigotes which attach the antibody to varying degrees. Studies using chemical or enzymatically treated antigens suggested that the McAb 2E9 was directed against carbohydrate epitopes, which were identified as being--galactosyl residues. In addition, preliminary results are shown, suggesting that the epitope recognized by the McAb 2E9 is involved in adhesion/or internalization of trypomastigotes.

The nitric oxide transduction pathway in Trypanosoma cruzi

A nitric oxide synthase was partially purified from soluble extracts of Trypanosoma cruzi epimastigote forms. The conversion of L-arginine to citrulline by this enzyme activity required NADPH and was blocked by EGTA. The reaction was activated by Ca2+, calmodulin, tetrahydrobiopterin, and FAD, and inhibited by N omega-methyl-L-arginine. L-Glutamate and N-methyl-D-aspartate stimulated in vivo conversion of L-arginine to citrulline by epimastigote cells. These stimulations could be blocked by EGTA, MK-801, and ketamine and enhanced by glycine. A sodium nitroprusside-activated guanylyl cyclase activity was detected in cell-free, soluble preparations of T. cruzi epimastigotes. L-Glutamate, N-methyl-D-aspartate, and sodium nitroprusside increased epimastigote cyclic GMP levels. MK-801 bound specifically to T. cruzi epimastigote cells. This binding was competed by ketamine and enhanced by glycine or L-serine. Evidence thus indicates that in T. cruzi epimastigotes, L-glutamate controls cyclic GMP levels through a pathway mediated by nitric oxide.

Effects of juvenile hormone analogues (JHA) on the development of Trypanosoma cruzi

Juvenile hormone analogues were tested for their lytic activity on Trypanosoma cruzi Chagas, 1909 blood tripomastigotes cultivated in vitro. The results indicated that the carbamate 4 and the phenoxyphenol derivative 1 are considered good candidates for blood sterilization. The compounds were also assayed for inhibition of development of parasites in infected mice showing a moderated degree of activity.

Monoclonal antibodies against the flagellar fraction of epimastigotes of Trypanosoma cruzi: immunoprotection against metacyclic trypomastigotes obtained by immunization of mice with an affinity-purified antigen

Subcellular fractions of Trypanosoma cruzi (epimastigotes) were assayed in their capacity to induce protective or aggressive effects in experimental animals. The flagellar fraction showed the best immunoprotective properties without tissular aggression. Monoclonal antibodies were prepared from mice immunized with this fraction. One of them, FCH-F8-4, was able to neutralize the infectivity of bloodstream trypomastigotes, to produce complement-mediated lysis on cell culture-derived trypomastigotes and to recognize the surface of trypomastigotes and epimastigotes by immunofluorescence. FCH-F8-4 reacted in Western blotting with several epimastigote proteins ranging from 50 to 150 kDa, showing a more intense reactivity with 4 bands while it reacted with two molecules on trypomastigote preparations (15 and 48 kDa). Purified antibody was coupled to CNBr-activated Sepharose and used to purify antigens from epimastigote extracts. These antigens were used to immunize BALB/c mice in the presence of Bordetella pertussis as adjuvant. Animals were protected against a challenge with 10(3) metacyclic forms of T. cruzi (Tulahuén strain). Only 40% of immunized mice presented detectable parasites in blood after challenge. Parasitemia decreased 90% in relation to controls in those animals. Survival of immunized mice was 100% in all immunoprotection experiments. These results suggest that the epitope recognized by FCH-F8-4 present in the purified antigens keeps the protective characteristics of flagellar fraction and could be a candidate for the development of a vaccine against T. cruzi infection.

Characterization of major surface and excretory-secretory immunogens of Trypanosoma cruzi trypomastigotes and identification of potential protective antigen

The surface antigens of Trypanosoma cruzi trypomastigotes were identified by immunoprecipitation and were compared with metabolically labelled excretory-secretory products (ES) released by the parasites in vitro. A series of major immunogenic components in the ES antigens were revealed (160 kDa, 130 kDa and 80-110 kDa). The trypomastigote surface also bears the 130 kDa band and the 80-110 kDa complex. Competition experiments demonstrated the common antigenic structure of the ES and the surface antigens. Two-dimensional analysis of ES antigens immunoprecipitated by human Chagasic serum revealed several spots in the 80-110 kDa region with a wide range of isoelectric points (PI between 5.4 and 6.7). This reflects a charge heterogeneity of these polypeptides. The trypomastigote 85 kDa polypeptide was also identified in the ES antigens by using a monoclonal antibody against this antigen. Two-dimensional analysis of the 85 kDa proteins shed from the surface of trypomastigotes and immunoprecipitated by the monoclonal antibody 155D3 showed 2 major spots: a major part of the 85 kDa polypeptide was found at pH 6.5-6.6, whereas a substantial amount of the antigen was found at pH 5.7. An additional component with molecular weight of approximately 58 kDa and isoelectric points of 6.5 and 6.6, was also visualized. Detection of the 85 kDa polypeptide circulating in serum from patients with acute and chronic Chagas' disease was achieved using an enzyme-linked immunosorbent assay. In addition, the data obtained showed that a polyclonal antibody to the 85 kDa polypeptide could be used to passively induce a partial protection of Fischer rats against acute lethal infection. Thus, the antigens recognized by polyclonal antibody appear to play a role in the development of protective immunity against T. cruzi.

Cyclic AMP-dependent protein kinase activity in Trypanosoma cruzi

A cyclic AMP-dependent protein kinase activity from epimastigote forms of Trypanosoma cruzi was characterized. Cytosolic extracts were chromatographed on DEAE-cellulose columns, giving two peaks of kinase activity, which were eluted at 0.15 M- and 0.32 M-NaCl respectively. The second activity peak was stimulated by nanomolar concentrations of cyclic AMP. In addition, a cyclic AMP-binding protein co-eluted with the second kinase activity peak. Cyclic AMP-dependent protein kinase activity was further purified by gel filtration, affinity chromatography on histone-agarose and cyclic AMP-agarose, as well as by chromatography on CM-Sephadex. The enzyme ('holoenzyme') could be partially dissociated into two different components: 'catalytic' and 'regulatory'. The 'regulatory' component had specific binding for cyclic AMP, and it inhibited phosphotransferase activity of the homologous 'catalytic component' or of the 'catalytic subunit' from bovine heart. Cyclic AMP reversed these inhibitions. A 'holoenzyme preparation' was phosphorylated in the absence of exogenous phosphate acceptor and analysed by polyacrylamide-gel electrophoresis. A 56 kDa band was phosphorylated. The same preparation was analysed by Western blotting, by using polyclonal antibodies to the regulatory subunits of protein kinases type I or II. Both antibodies reacted with the 56 kDa band.

[Effect of ovariectomy on plasma levels of progesterone, free and conjugated estrone in pregnant sheep]

Progesterone, free and conjugated estrone were determined in peripheral plasma from ovariectomized and control pregnant ewes in order to observe the ovary contribution to these hormonal levels. Progesterone levels during pregnancy were lower in the ovariectomized ewes than in control, although the differences were significant only until the 120th day of pregnancy. From the 130th day to the 3rd-5th day prepartum, an increase in the hormone levels was observed in both groups of ewes indicating a placentary contribution. Very similar patterns were followed by the free and conjugated estrone concentrations, their levels not being significantly different in either group. Production of conjugated estrone both preceded and reached higher values than that of free estrone. Both hormones showed an abrupt increase in concentration two days before the parturition, decreasing after that. Parturition mechanisms, foetus viability and the length of pregnancy were not affected by ovariectomy.

Monoclonal antibodies against the flagellar fraction of epimastigotes of Trypanosoma cruzi: complement-mediated lytic activity against trypomastigotes and passive immunoprotection in mice

Trypanosoma cruzi, the causative agent of Chagas' disease, is widely spread in Central and South America. The present report describes three monoclonal antibodies (mAbs) directed against the flagellar fraction of epimastigotes (Ffe) of the parasite, Tulahuén strain. The three mAbs were of IgG1 isotype. Indirect immunofluorescence assays revealed that the three mAbs bind to epimastigotes, the FCH-F8-1 and -3 bind to blood trypomastigotes (BT) and FCH-F8-1 is the only one that binds to amastigotes. Three different proteins of the parasite were recognized by the mAbs in immunoprecipitation assays: an 85 kDa of BT with the FCH-F8-1 mAb, a 40 kDa of Ffe with the FCH-F8-2 mAb, and a 90 kDa of Ffe and of BT with the FCH-F8-3 mAb. Positive complement mediated lysis (CML) of BT and metacyclic forms, obtained from the insect vector feces, were shown by the FCH-F8-1, while FCH-F8-3 only showed CML against the metacyclic trypomastigotes. FCH-F8-2 did not mediate any CML activity. Passive transference of the mAbs to BALB/c mice conferred protection, in terms of survival, ranging from 50 (FCH-F8-2 and -3) to 80% (FCH-F8-1) against a challenge with 1 X 10(3) BT. These results suggest that FCH-F8-1 may be a useful tool to purify proteins in order to investigate their role in immunoprotection experiments.

Immunoprotection of mice against Trypanosoma cruzi with a lyophilized flagellar fraction of the parasite plus adjuvant

The immunization with the flagellar (F) fraction from epimastigotes of Trypanosoma cruzi has been shown to protect mice against a challenge of bloodstream trypomastigotes of the parasite, both in terms of mortality and decrease in parasitemia. We have compared the immunoprotective properties of the fresh F fraction with those of a lyophilized F (LF) fraction, alone or together with Bordetella pertussis (Bp) as adjuvant. The best results were obtained with LF + Bp: after challenge with 1 X 10(3) metacyclic trypomastigotes, 100% of the mice immunized with LF + Bp survived, and 60% of them showed no signs of parasitemia. Only the animals in which patent parasitemia was demonstrated presented heart and muscle infiltrates.

Protective immunity and pathology induced by inoculation of mice with different subcellular fractions of Trypanosoma cruzi

Mice were immunized with subcellular fractions obtained by differential centrifugation from epimastigotes of Trypanosoma cruzi (Tulahuén strain). In a chronic model of Chagas' disease, they were challenged each with 25 bloodstream trypomastigotes. Non-immunized, non-challenged and non-immunized challenged animals were kept as controls. Among the challenged mice, those immunized with 105,000 g pellet (Mc) and 105,000 g supernatant (Cs) fractions presented positive xenodiagnosis, myocarditis and myositis similar to those shown by non-immunized challenged controls. The fractions enriched in flagella, the 5000 g pellet (P5) and the flagellar fraction (F) resulted in fewer animals with positive xenodiagnosis and in hosts partially protected from the development of myocarditis. In the absence of infection, Mc and Cs induced an intense myocarditis while F induced mild lesions similar to those found in the controls. P5 caused a myocarditis intermediate between that elicited by Mc and that in the controls. 50% of the animals immunized with Cs presented pathological electrocardiograms in the absence of challenge. The animals immunized with F and P5 and challenged were protected against the development of pathological electrocardiograms, whereas those immunized with Mc and Cs behaved like the non-immunized controls. The immunized, non-challenged animals presented anti-T. cruzi IgG antibodies, with titres which were lower than those shown by the immunized and challenged mice.--The results show the possibility of obtaining tissue lesions with antigenic preparations of T. cruzi in the absence of infection, and suggest that the mechanisms involved in the generation of myocarditis and electrocardiographic alterations are probably different, since these pathologies can be elicited by different subcellular fractions. Among the antigenic components of the parasite, the flagellar fraction gave the best immunoprotective properties, with little or no immunoaggressive effects.

Induction of heart alterations by immunization with subcellular fractions from Crithidia fasciculata

Immunization of mice with subcellular fractions of C. fasciculata led to myocarditis and electrocardiographic alterations similar to those induced by immunization with T. cruzi, the etiological agent of Chagas' disease, suggesting the presence of similar cardiotoxic antigens in both trypanosomatid flagellates.

Purification and properties of anti-Trypanosoma cruzi antibodies isolated from patients with chronic Chagas' disease

Three purified human IgG antibodies against Trypanosoma cruzi (anti-F, anti-Mc and anti-Cs) showed different reactivities in vitro. While all of them agglutinated specifically sensitized sheep red cells the complement-fixing capacity of anti-Fc and anti-Cs was higher than that of anti-Mc antibody. This one also showed a minimal precipitating activity. When the ability to neutralize mice bloodstream trypomastigotes was analyzed, the results obtained indicated that anti-F antibody was the most effective.