Lung-stage schistosomula are the target of protective immunity in mice vaccinated with attenuated cercariae of Schistosoma
mansoni. Therefore, proteins present at this developmental stage, and in particular those which are secreted, are a potential
source of novel vaccine candidates. However, little information is available about such molecules. Here we describe the
cDNA clones identified by screening expression libraries with serum raised against proteins released by lung-stage
schistosomula. In total, 11 different cDNA species were identified, 6 of which have been described previously in S.
mansoni; these included fructose 1,6-bisphosphate aldolase and Sm21.7 which together accounted for two-thirds of all
positive clones. Of the 5 newly described schistosome genes, 1 cDNA had a high degree of homology to the s5a subunit
of 26S proteasomes, most significant being with the human protein. The remaining 4 clones showed no significant
homologies to any genes sequenced previously. Fructose 1,6-bisphosphate aldolase, Sm21.7, the proteasome homologue
and 1 unknown clone (A26) have been expressed in a bacterial expression system and serum produced against each
recombinant protein. Immunolocalization showed fructose 1,6-bisphosphate aldolase, Sm21.7 and the proteasome homologue
to be most abundant in muscle cells whilst clone A26 was distributed throughout many tissues, but was most
abundant in the tegument. Analysis of the cellular immune responses of vaccinated mice showed 3 of the 4 expressed
clones to be highly immunogenic, inducing the secretion of large quantities of the Th1-type cytokine interferon gamma.