Vaccines in schistosomiasis using homologous antigens have
been studied extensively in experimentally infected mammalian hosts.
Vaccines using heterologous antigens have received comparatively less
attention. This review summarizes recent work on a heterologous 12 kDa
Fasciola hepatica antigenic polypeptide which cross reacts with
Schistosoma mansoni. A cDNA has been cloned and sequenced, and the
predicted amino acid sequence of the recombinant protein has been shown
to have significant (44 %) identity with a 14 kDa S. mansoni fatty
acid binding protein. Thus in the parasitic trematodes fatty acid binding
proteins may be potential vaccine candidates. The F. hepatica recombinant
protein has been overexpressed and purified and denoted rFh15. Preliminary
studies show that rFh15 migrates more slowly (i.e. may be slightly larger)
than nFh12 on SDS-PAGE and has a predicted pI of 6.01 vs. observed pI of
5.45. Mice infected with F. hepatica develop antibodies to nFh12 by 2
weeks of infection vs. 6 weeks of infection to rFh15; on the other hand,
mice with schistosomiasis mansoni develop antibodies to both nFh12 and
rFh15 by 6 weeks of infection. Both the F. hepatica and S. mansoni
cross-reactive antigens may be cross-protective antigens
with the protection inducing capability against both species.