The surface coat of bloodstream forms of Trypanosoma musculi from mice

Iodination and immunoprecipitation techniques together with indirect fluorescent antibody tests identified two polypeptides (SP) of molecular weights 88,000-92,000 and 66,000-70,000 in the surface coat of bloodstream forms of the mouse trypanosome, Trypanosoma musculi. As parasites multiply and enter the early plateau phase of infection the 88,000-92,000 SP is present while the 66,000-70,000 SP is only detectable after the mid-plateau phase. Western blotting of parasite extracts showed that the 88,000-92,000 SP was present throughout the course of infection, but it appears to become masked by the 66,000-70,000 SP or possibly immunoglobulin from about 16 days after infection. Based on results when Western blots of parasite extracts were probed with antibodies affinity purified against the 88,000-92,000 SP, the two SP appear to be immunologically related and the smaller may be a cleavage product of the larger. This would explain why affinity purified antibodies to each SP bound to trypanosomes collected 8 days after infection, when only the 88,000-92,000 is detectable in parasite extracts. However, the failure of antibodies affinity purified against the 66,000-70,000 SP to bind to the 88,000-92,000 SP in Western blots suggests that the smaller SP has some epitopes that are immunologically distinct from those of the larger SP.