Identification of a novel G245R polymorphism in the IL-2 receptor beta membrane proximal domain associated with human visceral leishmaniasis

Binding of the interleukin-2 (IL-2) to the IL-2 receptor (IL-2R) triggers a series of intracellular events culminating in lymphocyte proliferation and differentiation. We report here the identification of a novel G245R polymorphism in the membrane proximal domain of the IL-2 receptor beta chain (IL-2Rbeta). Present at a frequency of 7.2%, the IL-2-Rbeta G245R was identified in a population of Eastern Sudan exposed to a severe outbreak of visceral leishmaniasis (VL), a disease associated with a marked depression of T-cell antigen-specific responses. The location of the G245R polymorphism next to the box1/box2 proximal cytokine receptor homology segment and suggestive genetic association with the development of disease (P=0.043), suggest that it may affect Janus kinase (JAK) association and impair growth signal transduction. However, additional genetic association with a synonymous single nucleotide polymorphism (IL2RB+8777T) suggests that other variations of IL2RB or nearby genes participate in the highly significant linkage with VL at 22q12 previously reported for this population.

Coeliac disease in Sudanese children with clinical features suggestive of the disease

Our prospective hospital-based study examined frequency, clinical presentation and serological indicators of coeliac disease that correlated with intestinal biopsy among high-risk Sudanese children. From July 2001 to July 2002, 80 children aged 15 months-18 years presented with poor appetite, weight loss, pallor and proximal muscle wasting. We diagnosed coeliac disease in 18 (22.5%). Antigliadin antibodies (AGA-IgG, AGA-IgA or both) were high in 44; endomysial antibody retest was high in 30. Guardians of 12 children refused consent for biopsy. The other 18 were biopsied: 5 had total villous atrophy, 8 subtotal and 5 partial. All improved with gluten-free diet. Degree of villous atrophy did not correlate with diarrhoea duration or severity, anaemia severity or serological titres.

Antileishmanial antibodies in an outbreak of visceral leishmaniasis in eastern Sudan: high antibody responses occur in resistant subjects and are not predictive of disease

A 3-year longitudinal survey was carried out from 1998 to 2000 in a village in eastern Sudan where a visceral leishmaniasis (VL) outbreak occurred. Leishmania-specific antibodies were analysed by enzyme-linked immunosorbent assay and immunoblotting. Immunoblot analysis detected antibodies to Leishmania in 80% of the healthy subjects and half of them harboured high immunoglobulin (Ig) G antibody levels, similar to those of VL patients. These antibodies belonged to the IgG1 and IgG3 subclasses but neither their respective levels nor the immunoblot recognition patterns were predictive of VL. During this epidemic, a large proportion of subjects had a high antileishmanial antibody response, indicating that they were infected by Leishmania though most of them remained healthy during the whole study period. These results obtained in the context of an outbreak contrast with those obtained from studies performed in endemic areas characterized by lower parasite transmission levels. Furthermore, the clinical and serological follow-up of our study subjects showed that VL occurred mainly in subjects who had been serologically positive for 5-24 months rather than resulting from primo infection by the parasite.

Field evaluation of latex agglutination test for detecting urinary antigens in visceral leishmaniasis in Sudan

A latex agglutination test to detect urinary antigens for visceral leishmaniasis (VL) was studied. In 204 patients with suspected VL, KAtex had a sensitivity of 95.2% with good agreement with microscopy smears but poor agreement with 4 different serology tests. It was also positive in 2 confirmed VL cases co-infected with HIV. In all K4tex-positive confirmed cases actively followed up after treatment, the test became negative 1 month after completion of treatment. While IC4tex had a specificity of 100% in healthy endemic and non-endemic controls, the direct agglutination test (DAT) was positive in 14% of the KAtex-negative healthy endemic controls. KAtex is a simple addition to the diagnostics of VL particularly at field level and as a complementary test for the diagnosis of VL in smear-negative cases with positive DAT results.

Genetic control of visceral leishmaniasis in a Sudanese population: candidate gene testing indicates a linkage to the NRAMP1 region

There is some evidence showing that genetic factors are involved in human susceptibility to parasitic diseases such as schistosomiasis and malaria. Studies have shown that the Nramp1 and H-2 genes are implicated in the control of Leishmania donovani infection in mice. We sought genetic loci involved in the control of susceptibility to visceral disease caused by L. donovani in humans. We studied 37 families with at least two affected sibs living in a village in eastern Sudan, where an outbreak of visceral leishmaniasis occurred between 1995 and 2000. The genetic markers located in five chromosomal regions containing candidate genes were typed: 2q35 (NRAMP1), 5q31-q33 (Th2 cytokine cluster), 6p21 (HLA/TNF-alpha), 6q23 (INFGRI) and 12q15 (INF-gamma). Linkage (multipoint lod-score=1.08; P=0.01) was observed for the 5'(CA) repeat polymorphism in the NRAMP1 promoter. This suggests that genetic variations of this gene affect susceptibility to visceral leishmaniasis in this population.

The sandfly fauna in the visceral-leishmaniasis focus of Gedaref, in the Atbara-River area of eastern Sudan

Visceral leishmaniasis (VL) is an acute public-health problem in Sudan. Between 1997 and 2000, four, brief entomological surveys were carried out in Barbar El Fugarra, a village in the state of Gedaref, in the Atbara-River area of eastern Sudan. Between 1996 and 1999, 658 cases of VL occurred among the village's population of about 4000. CDC miniature light-traps set inside and outside human dwellings were used to collect a total of 12,745 sandflies, including five species of the genus Phlebotomus and 19 of Sergentomyia. Phlebotomus papatasi and P. orientalis made up 7% and 5% of the collected sandflies, respectively. Seasonal variation was observed in the numbers of P. orientalis, P. papatasi, S. schwetzi and S. magna caught. Almost all (88%) of the sandflies collected were caught inside houses or granaries and there appeared to be particularly large indoor populations of P. orientalis, P. papatasi, S. schwetzi, S. magna and S. clydei. Phlebotomus orientalis could be responsible for the indoor transmission of the parasites causing the local VL, between humans and between humans and local dogs (which have been found infected by some of the Leishmania zymodemes found in humans). The co-occurrence in this focus of P. papatasi and Arvicanthis niloticus, which are known vectors and reservoir hosts, respectively, of L. major, indicates the possibility that outbreaks of human cutaneous leishmaniasis might occur in the area.