Differential responsiveness of humans with early-stage schistosomiasis haematobium to Schistosoma haematobium soluble adult-worm and egg antigens

Abstract

Schoolchildren (7–8 years old) infected with Schistosoma haematobium were tested for lymphocyte proliferative responses, in vitro granuloma formation (IVGF), and cytokine release in T-cell Western assays and for serum antibody reactivity by enzyme-linked immunosorbent assay (ELISA) and immunoblotting against S. haematobium soluble adult-worm (SAWA) and egg (SEA) antigens. The lymphoproliferative response rate of individual subjects against 10 SAWA and 15 SEA electroseparated bands ranged from 0 to 33 % and from 11 to 66 %, respectively. The SAWA bands essentially failed to elicit significant IVGF, in contrast to the SEA bands, all of which were capable of inducing IVGF from peripheral blood mononuclear cells (PBMC) of 30–80 % of individual donors. The exclusive ability of SEA bands to induce IVGF could not be attributed to selective release of interleukin 2 (IL-2), IL-4, or interferon-gamma, as SEA and SAWA bands were capable of eliciting release of a similar array of cytokines in supernatants of 4-day PBMC cultures. The antibody response to SEA was stronger than that to SAWA, yet the proportion of SAWA bands binding humoral antibodies of individual donors was significantly larger than that observed for SEA. The study thus suggests that humans with early-stage S. haematobium infection respond poorly to SAWA but mount strong cellular immune responses to SEA that result in granuloma and antibody formation.