Human antibody responses to Schistosoma mansoni: the influence of epitopes shared between different life‐cycle stages on the response to the schistosomulum

Abstract

Sera from 120 Kenyan schoolchildren who were infected with S. mansoni were individually examined, using an enzyme-linked immunoabsorbent assay (ELISA), for the presence of IgG and IgM antibodies reactive with antigens derived from adult worms, the outer membrane of the schistosomulum or from the parasite egg. In addition, antibodies against more purified egg antigens, an egg stage-specific glycoprotein preparation and a polysaccharide egg antigen known to share epitopes with the schistosomular surface were measured in ELISA, as were antibodies reactive with trichloroacetic acid-soluble and periodate-insensitive antigens derived from the outer membrane of schistosomulum and antigens shed when schistosomula were cultured in vitro. IgG subclass responses to the unfractionated egg antigen were also measured. The results from each of these assays were compared with the results of each other assay and with the number of parasite eggs excreted by each child, using Spearmans rank correlations. These comparisons revealed a number of statistically significant positive correlations. IgG4 anti-egg antibodies correlated better with intensity of infection than did other IgG subclasses. Total IgG responses against polysaccharide antigens did not correlate with intensity of infection as well as IgG responses against other antigens; epitopes shared between the schistosomulum surface and the adult worm were different to those shared with the parasite egg; and, there was antigen-directed restriction of IgG subclass responses to some egg and adult worm antigens which carried these shared epitopes. It is argued that this might have a qualitative effect on the nature of the antibodies directed against the schistosomulum by infected individuals and therefore have important consequences for the outcome of a subsequent exposure to infection with the same parasite.

Identification of a Novel Antigen ofSchistosoma mansoniShared withPlasmodium falciparumand Evaluation of Different Cross-Reactive Antibody Subclasses Induced by Human Schistosomiasis and Malaria

“…However, in this Ugandan community, there were significant positive correlations between the intensity of S. mansoni infection and IgG4 responses to S. mansoni antigens, including SmLRR, and anti-SmLRR IgG4 responses were strongly positively correlated with anti-Pfs IgG4 responses. The IgG4 response is a major human response to chronic helminthiasis (6,8,14,27) and is often the only IgG subclass response that correlates with the intensity of schistosome (20,24) and other helminth (20) infections. As seen previously, the IgG3 responses to malaria and schistosome antigens, including SmLRR, positively correlated with each other but were not related to the intensity of S. mansoni infection.…”

Specific immunoglobulin measurements related to exposure and resistance to Schistosoma mansoni infection in Sudanese canal cleaners

“…Within endemic areas, infected individuals of all ages have high levels of circulating antibody with anti-schistosome specificity, including antibodies which react with the surface of the schistosomulum. However, the class and subclass composition of these antibodies vary with age and intensity of infection [4][5][6]. Since antibody isotypes differ greatly in their ability to mediate various immune effects, the isotype composition of anti-schistosome responses may have a major influence on the efficiency of antibody-dependent cytotoxic effector mechanisms, and consequently on the expression of protective immunity during schistosome infection.…”

Studies on human schistosomiasis: chemotherapy, immunity and morbidity

“…Evidence was obtained that the reason why immunity takes so long to develop in these children is not that the younger children fail to mount a protective response, but rather that they also pro duce inappropriate antibodies that block the expression of the protective response (Butterworth et al, 1987;Dunne et al, 1988). These blocking antibodies are elicted mainly in response to egg polysaccharide antigens: they cross-react with carbohydrate epitopes expressed at the schistosomulum sur face: they comprise both IgM and IgG2 antibodies: and they slowly decline with age, permitting the expression of the pro tective responses and hence of immunity.…”