Trypanosoma lewisi: stage-specific surface antigens and exoantigens recognized by monoclonal antibodies.

The stage-specific expression of surface antigens by Trypanosoma lewisi was investigated using monoclonal antibodies directed against this parasite. Hybridomas secreting monoclonal antibodies were produced by the fusion of SP2/0-Ag 14 mouse plasmacytomas with spleen cells from rats infected previously with the Taliaferro strain of T. lewisi. Additivity enzyme-linked immunosorbent assays and indirect immunofluorescent antibody tests indicated the determinant recognized by monoclonal antibody TL40.3 (IgM) was different from those recognized by monoclonal antibodies TL40.1 (IgA), TL40.2 (IgM), and TL40.6 (IgG2 alpha). Monoclonal antibody TL40.3 agglutinated trypanosomes collected 3 days after parasite inoculation while monoclonal antibodies TL40.1, TL40.2, and TL40.6 agglutinated trypanosomes collected 6 days after inoculation. Since agglutinin titers against trypanosomes from irradiated (700 rad from a 60Co source) and nonirradiated rats were similar, expression of the antigens recognized by the monoclonal antibodies appeared to be independent of the immunological state of the host and the morphology of the parasite. The reproduction of T. lewisi in in vitro trypanostatic assays was inhibited only when the monoclonal antibodies were present in concentrations greater than or equal to those needed to agglutinate the trypanosomes. Monoclonal antibodies TL40.1 and TL40.3, but not TL40.2 and TL40.6, agglutinated erythrocytes collected later in the infection from irradiated, infected rats. None of the monoclonal antibodies agglutinated erythrocytes from nonirradiated, infected rats, from irradiated, noninfected rats or from nonirradiated, noninfected rats. This suggests that immunocompetent rats may make blocking antibodies against the exoantigens recognized by monoclonal antibodies TL40.1 and TL40.3.