Early Exposure of Infants to GI Nematodes Induces Th2 Dominant Immune Responses Which Are Unaffected by Periodic Anthelminthic Treatment

We have previously shown a reduction in anaemia and wasting malnutrition in infants <3 years old in Pemba Island, Zanzibar, following repeated anthelminthic treatment for the endemic gastrointestinal (GI) nematodes Ascaris lumbricoides, hookworm and Trichuris trichiura. In view of the low intensity of worm infections in this age group, this was unexpected, and it was proposed that immune responses to the worms rather than their direct effects may play a significant role in morbidity in infants and that anthelminthic treatment may alleviate such effects. Therefore, the primary aims of this study were to characterise the immune response to initial/early GI nematode infections in infants and the effects of anthelminthic treatment on such immune responses. The frequency and levels of Th1/Th2 cytokines (IL-5, IL-13, IFN-γ and IL-10) induced by the worms were evaluated in 666 infants aged 6–24 months using the Whole Blood Assay. Ascaris and hookworm antigens induced predominantly Th2 cytokine responses, and levels of IL-5 and IL-13 were significantly correlated. The frequencies and levels of responses were higher for both Ascaris positive and hookworm positive infants compared with worm negative individuals, but very few infants made Trichuris-specific cytokine responses. Infants treated every 3 months with mebendazole showed a significantly lower prevalence of infection compared with placebo-treated controls at one year following baseline. At follow-up, cytokine responses to Ascaris and hookworm antigens, which remained Th2 biased, were increased compared with baseline but were not significantly affected by treatment. However, blood eosinophil levels, which were elevated in worm-infected children, were significantly lower in treated children. Thus the effect of deworming in this age group on anaemia and wasting malnutrition, which were replicated in this study, could not be explained by modification of cytokine responses but may be related to eosinophil function

Passerine MHC: genetic variation and disease resistance in the wild

The passerine major histocompatibility complex (MHC) class I and IIB genes are different from those of the avian model species the chicken because passerines have (1) a larger number of MHC genes, (2) MHC genes with longer introns, and (3) MHC genes that are pseudo-genes. Most passerine MHC genes are transcribed (coding), extremely variable and subject to balancing selection. The high genetic diversity of the MHC genes of passerines is most likely maintained by selection from a large number of different pathogens. Association between MHC alleles and resistance to avian malaria infections have been reported in House Sparrows and Great Reed Warblers. Passerines are infected by a large number of different avian malaria infections. Therefore passerines and avian malaria is a study system that is well-suited to investigations of balancing selection and associations between MHC genes and disease resistance