Variation in the sensitivity of successive variable antigen types in a Trypanosoma (Trypanozoon) brucei subspecies clone to some African game animal sera.

Abstract

A Trypanosoma brucei subspecies clone was passaged in rats at ten-day intervals and the sensitivity/resistance to a variety of mammalian sera, of the successive variable antigen types (VATs) produced, was examined sequentially in a modified version of the blood incubation infectivity test (BIIT). A proven homogeneous VAT was used to initiate this series of tests, in which seven successive and different VATs were each exposed in vitro at 38.5 degrees C for 2 h to standard samples of pooled rat serum (PRS), normal human serum (NHS) and to sera from two different eland and three different hippopotami. Samples were then inoculated into susceptible rats to determine the effects of the individual sera on the subsequent infectivity of the trypanosomes. The seven VATs were found to vary widely in their sensitivity to the different game sera, though all remained strongly resistant to the pooled rat and the normal human serum samples. BII testing of isolates from positive test rats in the sequential study showed that their resistance to normal human serum was unaffected by their exposure in vitro to the different game sera.