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.

Longitudinal quantification of incipient carious lesions in postorthodontic patients using a fluorescence method.

The aims of this study were to evaluate the effect of two caries-preventive programs, and to apply the laser fluorescence method, DIAGNOdent, for longitudinal quantification of changes in incipient carious lesions. Twelve subjects with 127 test teeth exhibiting white spot lesions on the buccal surfaces after completed orthodontic therapy were enrolled in the study. Visual examination was performed at baseline and after 12 months. The subjects were divided into two groups: one group received repeated professional tooth cleaning combined with oral hygiene instruction; and the control group received repeated oral hygiene instruction only. The white spot lesions were measured by DIAGNOdent at baseline, and at 3, 6, 9, and 12 months thereafter. There was a significant difference in the DIAGNOdent readings between the first and the final evaluations. However, there was no statistically significant difference between the two treatment groups regarding changes of DIAGNOdent values over time. In conclusion, it may be possible to use DIAGNOdent for longitudinal quantification of carious lesions on smooth surfaces over a period of 1 yr under in vivo conditions. The combination of professional tooth cleaning and oral hygiene instruction had a similar efficacy to professional tooth cleaning only for promoting the remineralization of white spot lesions.

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.