Age-related antibody profiles in Schistosoma haematobium infections in a rural community in Zimbabwe

Antibody responses to soluble Schistosoma haematobium egg (SEA) and worm (SWA) antigens in a rural Zimbabwean study population were examined by ELISA. One hundred and sixteen S. haematobium infected and 124 non-infected individuals representing individuals greater than five years old, were included. Non-endemic control ser a were obtained from a schistosomiasis non-endemic part of Zimbabwe and from Norwegian blood donors. A possible association between IgE antibody responses and resistance to S. haematobium infection was indicated by a negative correlation between IgE anti-SEA levels and intensity of S. haematobium infection, and by a positive correlation between IgE responses to SEA and SWA and age. Similarly, an association between IgA and anti-SWA and resistance to S. haematobium was suggested by a negative cor relation to intensity of infection and a positive correlation with age. A probably association between IgM and IgG4 with susceptibility to S. haematobium infection was described; intensity of S. haematobium infection correlated positively with IgG, IgG4 and IgM responses to SEA and with IgG4 and IgM responses to SWA, also age correlated negatively with IgG4 and IgM responses to SEA and with IgG4 responses to SWA. These findings support the concept of IgG4 and IgM as blocking antibodies. Significant positive correlations between antibody responses to SEA and SWA suggests cross-reactivity between eggs and adult worms. In addition, the recognition by IgE and IgG4 of the same schistosomulum antigens in immunoblotting suggests competition for the same antigens.