Effects of selenium deficiency in the development of trypanosomes and humoral immune responses in mice infected with Trypanosoma musculi.

The selenium-deficient mouse-trypanosome system was used to study the effects of selenium deficiency in Swiss Webster mice infected with Trypanosoma musculi. In selenium-deficient mice, a low parasitemia was observed and infection was cleared by day 16 post-inoculation (PI), whereas control mice sustained the parasitemia until day 24 PI. There were no significant differences in size variability of the trypanosomes; however the range of variability in the length of parasites differed significantly between the three groups. In comparison to mice on complete or pair-fed diets, the selenium-deficient mice produced lower concentrations of IgG(1), IgG(2b), IgG(3), and IgM. The levels of IgG(2a) and IgA were lower than normal controls. The results of the present study indicated that there was a severe depression in primary and secondary antibody responses to sheep red blood cells in all inoculated mice. However, these responses were significantly less depressed in selenium-deficient mice.

Molecular studies of Biomphalaria glabrata, an intermediate host of Schistosoma mansoni.

The freshwater gastropod Biomphalaria glabrata is one of the most important invertebrate hosts of the helminth parasite Schistosoma mansoni. Investigators are using different strategies to determine the molecular basis of this snail-parasite relationship. Of particular interest are the identification of parasite resistance genes in the snail, and the application of molecular probes to better understand the epidemiology of schistosomiasis. This review will focus on recent advances that have been made on genome analysis of B. glabrata. Much of this work has centred on the use of random amplification of polymorphic DNA-PCR-based technology, with restriction fragment length polymorphism analysis and the generation of expressed sequence tags from the snail. A brief discussion of how parasite products may complicate this analysis is also given, along with an indication of the scope of the problems that lie ahead.