ANIMAL MODELS FOR THE STUDY OF LEISHMANIASIS IMMUNOLOGY

Leishmaniasis remains a major public health problem worldwide and is classified as Category I by the TDR/WHO, mainly due to the absence of control. Many experimental models like rodents, dogs and monkeys have been developed, each with specific features, in order to characterize the immune response to Leishmania species, but none reproduces the pathology observed in human disease. Conflicting data may arise in part because different parasite strains or species are being examined, different tissue targets (mice footpad, ear, or base of tail) are being infected, and different numbers (“low” 1×102 and “high” 1×106) of metacyclic promastigotes have been inoculated. Recently, new approaches have been proposed to provide more meaningful data regarding the host response and pathogenesis that parallels human disease. The use of sand fly saliva and low numbers of parasites in experimental infections has led to mimic natural transmission and find new molecules and immune mechanisms which should be considered when designing vaccines and control strategies. Moreover, the use of wild rodents as experimental models has been proposed as a good alternative for studying the host-pathogen relationships and for testing candidate vaccines. To date, using natural reservoirs to study Leishmania infection has been challenging because immunologic reagents for use in wild rodents are lacking. This review discusses the principal immunological findings against Leishmania infection in different animal models highlighting the importance of using experimental conditions similar to natural transmission and reservoir species as experimental models to study the immunopathology of the disease.

HEPATITIS B VACCINATION COVERAGE AND POSTVACCINATION SEROLOGIC TESTING AMONG MEDICAL STUDENTS AT A PUBLIC UNIVERSITY IN BRAZIL

The aim of this cross-sectional study was to determine the hepatitis B vaccination coverage among medical students at a public university in Rio de Janeiro, Brazil, and their compliance with the postvaccination serologic testing recommendations. Of the total of 858 students, 675 (78.7%) participated in the study. Among the participants, 48.9% (95% CI: 45.1% to 52.7%) were vaccinated against hepatitis B (received ≥ 3 doses of the vaccine), 31.6% were not (received 0, 1 or 2 doses), and 19.6% did not know their vaccination status. Hepatitis B vaccination coverage increased from 26.0% among first-year students to 70.6% among sixth-year students while the prevalence of unknown vaccination status decreased from 39.7% among first-year students to 2.4% among sixth-year students. The frequency of unvaccinated students ranged from 23.7% among fifth-year students to 34.4% among first-year students. Only 34.8% of the vaccinated students performed the anti-HBs testing after vaccination. Among these medical students, we found a low adherence to the hepatitis B vaccination and to the postvaccination serologic testing. A comprehensive hepatitis B immunization program should be offered to students at this medical school.

The use of different concentrations of leishmanial antigen in skin testing to evaluate delayed hypersensitivity in american cutaneous leishmaniasis

Three concentrations of Leishmania mexicana amazonensis sonicated whole promastigote antigen (30, 9.6 and 3 ug N in 0.1 ml) wereprepared and 0.1 ml of each inoculated intradermally intopatients who live in one endemic leishmaniasis region in Brazil. Patients were divided into groups with active cutaneous leishmaniasis (ACL), healed cutaneous leishmaniasis (HCL), mucosal leishmaniasis (ML), and Controls (C). Skin reactions were recorded by measuring induration 48 hours after inoculation. Skin tests using 9.6 ugN/0.1 mlyielded the best diagnostic resultssince 97% of 30 patients with active lesions (cutaneous or mucosal) and 83% with HCL showed reactions of 5 mm orgreater as compared with 4% Controls. Tests using 30ug N/O. 1 ml causedan unacceptable levei of skin reactions with necrosis (10% of ACL patients tested and 17% of HCL, respectively). Tests using 3 ug N/O. 1 ml were less sensitive since only 87% of patients with active lesions and 68% with HCL had reactions of 5mm orgreater. The 3 ug N/O. 1 ml dose was utilized to ask the questions whether skin delayed hypersensitivity decreased with time after the initial lesion and whether mucosal involvement is associated with enhaced hypersensitivity to leishmanial antigen. Decreased delayed hypersensitivity was noted only in those patients who had an initial lesion more than 30 years ago. The mean induration of the reaction in 10 patients with ML was 11.3 mm ± 7.15, in 41 patients with HCL, 9.27 mm ± 6.78 and in 20patients with ACL 10. 7 mm ± 6.10 mm. The percent of patients with 5 mm orgreater induration was ML 80%, HCL 71%, ACL 90%. Thus, we could not confirm an association between enhanced delayed hypersensitivity and mucosal involvement in leishmaniasis.

The influence of the regional basic diet from northeast Brazil on health and nutritional conditions of mice infected with Schistosoma mansoni

Protein nutritionalstatus indicators were studied in weanling albino Swiss mice infected with S. mansoni andfed the Regional Basic Diet (RBD)from Northeast Brazil, a multideficient diet of low-protein content. Each mouse was infected percutaneously with 80 cercariae. The experiment lasted 63 days. The growth curve, food consumption, protein intake, weight gain, Protein Efficiency Ratio (PER) and Net Protein Ratio (NPR) were the parameters investigated. RBD-fed mice showed a marked weight loss, a lower food and protein intake, a slower body weight gain and lower rates of food protein utilization when compared to casein-fed animals. Differences between infected and non-infected mice were not consistent. The present results suggest that the effects of RBD-induced malnutrition on health and nutritional conditions of the mice are more severe than those of Manson's schistosomiasis, in the initial phase of the disease.

Influence of light conditions on adult mortality and egg-laying of Triatoma brasiliensis neiva, 1911 (Hemiptera: Reduviidae: Triatominae)

We compared, for Triatoma brasiliensis, the egg-laying process and the mortality of adults under conditions of almost permanent darkness and with normal laboratory luminosity. Mortality did not differ between groups. The egg-laying per vial and per female was significantly greater in the group of normal luminosity. We consider that it is not recommendable to keep the adults of this species under complete darkness. Other biological aspects should be analysed in relation to luminosity.

Excito-repellency effect of deltamethrin on triatomines under laboratory conditions

This work demonstrates that deltamethrin in low doses produces an excito-repellency effect on triatomines, as already observed for mosquitoes. A wooden box covered with a cloth impregnated with deltamethrin at doses of 2.5 and 5mg ai/m² was utilized for the experiment. The triatomine species studied were Triatoma infestans, Panstrongylus megistus, Rhodnius neglectus and Triatoma sordida. Adults were released in one of the sides of the box and their position was noted in subsequent periods. The observations were realized on the day the cloth was impregnated and subsequently repeated at 30 and 60 days for T. sordida; on day 120, the remaining species were included. Insect mortality and attempts at flight from the box were also observed. Excito-repellency was evident for all species and doses up to day 120. The only species that attempted to fly was P. megistus. The excito-repellency effect may be considered as an additional advantage to the insecticide power, as it should be able to prevent the installation of new colonies by females that fly into the homes, and at the moment of the spraying, it should promote the flushing out of triatomines from the wall crevices and from other shelters.

Environmental sanitation conditions and health impact: a case-control study

This epidemiological investigation examines the impact of several environmental sanitation conditions and hygiene practices on diarrhea occurrence among children under five years of age living in an urban area. The case-control design was employed; 997 cases and 999 controls were included in the investigation. Cases were defined as children with diarrhea and controls were randomly selected among children under five years of age. After logistic regression adjustment, the following variables were found to be significantly associated with diarrhea: washing and purifying fruit and vegetables; presence of wastewater in the street; refuse storage, collection and disposal; domestic water reservoir conditions; feces disposal from swaddles; presence of vectors in the house and flooding in the lot. The estimates of the relative risks reached values up to 2.87. The present study revealed the feasibility of developing and implementing an adequate model to establish intervention priorities in the field of environmental sanitation.

Evaluation of an immunochromatography test for malaria diagnosis under different storage conditions

This study aimed to evaluate the second-generation OptiMal test for malaria diagnosis under various storage conditions. It detected all the positive samples, except for two Plasmodium malariae samples. Further research evaluating diverse environmental conditions are important for ICT test applicability in Brazilian malaria areas.

In vitro maintenance of Angiostrongylus costaricensis does not provide physiological conditions for egg laying

Fifteen pairs (male/female) of Angiostrongylus costaricensis were kept in vitro in Waymouth medium for three days to evaluate the amount and duration of egg laying. At 24, 48 and 72 hours, the mean egg counts were 321, 24 and 4 eggs/10 microliters, respectively. Most of the eggs were eliminated within the first 24 hours, suggesting they are expelled under non-physiological conditions. These results indicate that in vitro conditions are not appropriate for drug trials of egg-laying inhibitors for treatment of abdominal angiostrongylosis.

Prevalence of anti-hepatits A antibodies in children of different socioeconomic conditions in Vila Velha, ES

This report describes the prevalence of anti-HAV antibodies in children from elementary school in the Municipality of Vila Velha, ES, Brazil. Anti-HAV antibodies were investigated by ELISA method in the serum of 606 children (four to fourteen years old) from three elementary schools, located in neighborhoods with varying household monthly income levels: São José School, 200 chidren, household income higher than US$700; São Torquato School, 273 children, US$200 to 300; and Cobi School, 133 children, less than US$200. From each children data on age, gender, skin color, sanitary conditions, frequency of contact with sea or river water and family history of hepatitis were recorded. Anti-HAV antibodies were present in 38.6% of all children, 9% in São José School, 49.1% in São Torquato School and 61.7% in Cobi School. Logistic regression analysis demonstrated a positive correlation of positive anti-HAV test with age, non white color of the skin, absence of sewage treatment and domestic water filter, and a past history of hepatitis. The prevalence of anti-HAV antibodies in school children in Vila Velha, ES, was lower than that observed in the same age group in North and Northeast Brazil and was significantly higher in children from families with low socioeconomic status. In addition the results indicate a changing epidemiologic pattern of hepatitis A in our country, with an increasing number of children and adolescents with high risk for HAV infection, mainly in high socioeconomic class. A consideration must be given to the feasibility of vaccination programs for children and adolescents in our country.

Life cycle and reproductive patterns of Triatoma rubrovaria (Blanchard, 1843) (Hemiptera: Reduviidae) under constant and fluctuating conditions of temperature and humidity

The aim of this study was to evaluate the temperature and relative humidity influence in the life cycle, mortality and fecundity patterns of Triatoma rubrovaria. Four cohorts with 60 recently laid eggs each were conformed. The cohorts were divided into two groups. In the controlled conditions group insects were maintained in a dark climatic chamber under constant temperature and humidity, whereas triatomines of the ambiental temperature group were maintained at room temperature. Average incubation time was 15.6 days in the controlled conditions group and 19.1 days in the ambiental temperature. In group controlled conditions the time from egg to adult development lasted 10 months while group ambiental temperature took four months longer. Egg eclosion rate was 99.1% and 98.3% in controlled conditions and ambiental temperature, respectively. Total nymphal mortality in controlled conditions was 52.6% whereas in ambiental temperature was 51.8%. Mean number of eggs/female was 817.6 controlled conditions and 837.1 ambiental temperature. Fluctuating temperature and humidity promoted changes in the life cycle duration and in the reproductive performance of this species, although not in the species mortality.

Chagas disease as a mechanistic model for testing a novel hypothesis

The association between depression and cardiovascular disease is well documented. Nevertheless, the process through which they are linked remains unknown, as does the direction of this relationship. Studies have suggested both that depression is a risk factor for heart disease and that heart disease is a risk factor for depression. A number of studies have established that a relationship exists between depression and inflammation, with alterations in the levels of inflammatory markers (IL-1, IL-6, TNF-alpha and others). Depressive symptoms have also been identified in many diseases characterized by inflammatory processes e.g. rheumatoid arthritis, bronchial asthma, diabetes, tuberculosis and cardiovascular diseases. In this brief viewpoint, we explain and propose how to use Chagas disease, a disorder characterized by inflammatory processes and leading to cardiovascular and autonomic problems, as a model for studying the directionality of the relationship between heart disease and depression.