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.