Isolation and characterization of a new serodeme of Trypanosoma rhodesiense.

: The isolation and characterization of a new serodeme of Trypanosoma brucei rhodesiense is described. A clone of organisms derived from a human infection produced chronic infections in mice. Additional clones of differing antigenic specificities were isolated from peaks of parasitemia which occurred in these mice. The variable antigen types (VATs) of these clones were determined by agglutination, immunofluorescence, and protection of actively immunized mice. Thirteen distinct VATs were isolated and designated Walter Reed Army Trypanozoon antigenic types. The described methodology and reagents, together with the chronicity of the infection produced in mice by this serodeme, provide a model for further study of immunopathology and antigenic variation in African trypanosomiasis. The use of these reagents in determining the incidence of VATs in an endemic area may allow an assessment of the feasibility of immunoprophylaxis.