IFN-gamma is associated with risk of Schistosoma japonicum infection in China.

Before the start of the schistosomiasis transmission season, 129 villagers resident on a Schistosoma japonicum-endemic island in Poyang Lake, Jiangxi Province, 64 of whom were stool-positive for S. japonicum eggs by the Kato method and 65 negative, were treated with praziquantel. Forty-five days later the 93 subjects who presented for follow-up were all stool-negative. Blood samples were collected from all 93 individuals. S. japonicum soluble worm antigen (SWAP) and soluble egg antigen (SEA) stimulated IL-4, IL-5 and IFN-gamma production in whole-blood cultures were measured by ELISA. All the subjects were interviewed nine times during the subsequent transmission season to estimate the intensity of their contact with potentially infective snail habitats, and the subjects were all re-screened for S. japonicum by the Kato method at the end of the transmission season. Fourteen subjects were found to be infected at that time. There was some indication that the risk of infection might be associated with gender (with females being at higher risk) and with the intensity of water contact, and there was evidence that levels of SEA-induced IFN-gamma production were associated with reduced risk of infection.

Comparison of the live vaccine potential of different geographic isolates of Schistosoma mansoni.

We have investigated the capacity of irradiated larvae of each of six different isolates of Schistosoma mansoni to protect mice against challenge infections from the homologous or a different isolate. The isolates differed in respect of their geographic origins, and in the lengths of time they had been maintained in the laboratory. All isolates induced significant protection against unattenuated challenge infections, and neither the degree of geographic disimilarity between vaccinating and challenge parasites, nor the numbers of laboratory cycles, appeared to influence the degree of protection induced by irradiation-attenuated larvae.