Irradiated larval vaccination and antibody responses evaluated in relation to the expression of immunity to Heligmosomoides polygyrus

Infections induced in NIH mice by irradiated (300 Gy) larvae of Heligmosomoides polygyrus effectively stimulated immunity to challenge, whereas unirradiated larvae did not. Importantly, this difference was lost by the elimination of the adult worms arising from unirradiated sensitising infections by drug treatment prior to challenge. No difference in the level of parasite-specific serum and mucosal IgG, IgG1, IgG2a or IgA was detected between immune mice sensitised either with drug-abbreviated unirradiated or irradiated larval infections and non-immune mice receiving two superimposed unirradiated infections. An enzyme-linked immunosorbent assay (ELISA) and immunoblotting data suggested that parasite-specific IgG1 was the predominant antibody class in both serum and intestinal perfusates. IgA exhibited differences in antigen specificity between the serum and the intestine. In serum, IgA responses were directed predominantly to L4 somatic antigens, whereas at the mucosal surface they were biased towards L4 excretory/secretory (ES) antigens. No correlation was found between the intensity of the serum or mucosal antibody responses and the mean worm burdens in groups of immune or non-immune mice. Moreover, no correlation was found between levels of parasite-specific serum or mucosal IgG, IgG1, IgG2a or IgA and the loss of worms in individual mice.