More on the Search for a Schistosomiasis Vaccine

Abstract

A candidate vaccine for human schistosomiasis, recombinant glyceraldehyde 3-phosphate dehydrogenase of Schistosoma mansoni (rSG3PDH)[ 1 El Ridi R. et al. J. Infect. Dis. 1998; 177: 1364-1372 Crossref PubMed Scopus (26) Google Scholar ], given intramuscularly, subcutaneously and/or intranasally, two or four times at three-week intervals, without adjuvant or mixed with Alum, Allison's or RIBI adjuvant, induces strong T-cell and B-cell immune reactivity in outbred Swiss mice. Immune responses to rSG3PDH and whole soluble adult worm antigens include lymphoproliferation, production of interleukin 2 (IL-2) and release of IgG1, IgG2a and IgG2b antibodies. However, these immune reactions do not lead to protection of the mice against challenge infection with cercariae of S. mansoni (R. El Ridi et al., Abstract) 1El Ridi, R. et al. The final Schistosomiasis Research Project (SRP) meeting, Cairo, Egypt, 15–19 March 1998. Abstract No. 072. 1 El Ridi, R. et al. The final Schistosomiasis Research Project (SRP) meeting, Cairo, Egypt, 15–19 March 1998. Abstract No. 072. . This result should not have been unexpected since SG3PDH occurs within the tegument of schistosomula but is not an outer membrane protein (R. El Ridi et al., Abstract) 2El Ridi, R. et al. The final Schistosomiasis Research Project (SRP) meeting, Cairo, Egypt, 15–19 March 1998. Abstract No. 073. 2 El Ridi, R. et al. The final Schistosomiasis Research Project (SRP) meeting, Cairo, Egypt, 15–19 March 1998. Abstract No. 073. . In immunized hosts, challenge larvae suffering natural attrition may release SG3PDH to evoke a memory response, but the enzyme in the parasite is not available for interaction with activated effector cells or antibodies.