Use of human infection and vaccine-protected baboon sera for the characterisation of cloned Schistosoma haematobium antigen genes.

A Schistosoma haematobium adult worm cDNA library was screened with sera from demonstrably immune baboons (mean worm reduction 94%) vaccinated with highly-irradiated cercariae (VBabS) and also with sera from adult S. haematobium-infected humans (HIS Sh). As species-specificity is a characteristic feature of the immunity induced by irradiated cercariae, S. haematobium species-specific clones were identified by rescreening positives with sera from S. mansoni-vaccinated animals or infected humans. Six species-specific clones, 3 initially detected with vaccinated baboon sera (D11, D14 and D26) and 3 with human infection sera (E1, E2 and E16) were further characterized by Western blotting. The three HIS-selected clones did not react significantly with VBabS or acutely-infected baboon sera (ABabS) while D11, D14 and D26 showed increasing reactivity with successive vaccinations. In addition D11 and D14 but not D26 responded to ABabS. When tested against HIS Sh from 24 patients of varying ages, D11 and D26 reacted most frequently with sera from individuals in the older age groups (> 17 yrs). A species cross reactive clone, D12, which was used as a positive control throughout, was found to react with all schistosome specific sera tested.