PROTECTION AGAINST SCHISTOSOMA-MANSONI INFECTION WITH A RECOMBINANT BACULOVIRUS-EXPRESSED SUBUNIT OF CALPAIN

Infections by human schistosomes, in particular Schistosoma mansoni, a ccount for significant morbidity and mortality every year in tropical and sub-tropical areas. The eggs of the parasite induce pathological c hanges in the infected host; in chronic and heavy infections, these ch anges may lead to death. A well-designed anti-schistosomal vaccine, al one or in concert with existing control measures such as chemotherapy, may prove to be a safe, inexpensive, and effective means of reducing the occurrence of severe disease and death in S. mansoni infection. Pr evious studies have demonstrated the importance of the syncytial layer containing the apical plasma membrane (APM) of S. mansoni in both the survival of the parasite in the mammalian host and as a potential sou rce of immunogens which may be utilized as vaccine candidates. In this paper, we present evidence for the protective capacity of several sch istosomal antigen preparations, including a calcium binding protein of the APM, S. mansoni calpain (GenBank accession no. M74233). We have c onstructed and characterized expression of a recombinant baculovirus e xpressing the large subunit of S. mansoni calpain, Sm-p80. This recomb inant Sm-p80 is recognized by IgA, IgM, IgG1, and IgG3 isotype antibod ies found in S. mansoni-infected human sera and partially-purified rec ombinant Sm-p80 provided a 29-39% reduction in worm burden in immunize d mice challenged with S. mansoni. Our data indicate that Sm-p80 may b e a useful vaccine antigen for the reduction of the morbidity associat ed with S. mansoni infections of mammalian hosts. (C) 1997 Elsevier Sc ience Ltd.