Antigenic analysis by agglutination of Trypanosoma brucei brucei parasitemias initiated in mice with in vitro-produced metacyclics.

Trypanosomes from 14 first-peak parasitemias initiated in mice by injection of in vitro-produced metacyclics were stabilated. Strains derived from these stabilates were analyzed for their antigenic composition by cross-agglutination with immune sera produced in rabbits against 12 of the stabilates. The antigenic composition of the 14 stabilates was compared also with two first-peak parasitemias from mice inoculated with fly-derived metacyclics, the variant-specific antigen of the strain used to initiate the cultures that ultimately became infective, and the antigenic variant that was used to infect the flies. One variant-specific, presumably basic, antigen was found, either as the predominant (nine parasitemias) or as a minor (seven parasitemias) antigen, in all first peak-parasitemia strain initiated with culture- or fly-derived metacyclics; it was absent, however, from the strains (not first-peak parasitemias) used to start the cultures or to infect the flies. Only one of the first-peak parasitemias appeared to have the basic antigen alone. The remaining parasitemia populations seemed to have from about two to six antigens, some of which were common to culture- and fly-derived infections. There was very little, if any, antigenic relationship between the foregoing populations and the strains employed for initiation of cultures or for infection of flies. It is evident from the results that much antigenic similarity exists between the culture- and tsetse fly-derived first-peak parasitemias.