Seven out of 11 bovines infected with different clones of Trypanosoma brucei showed 2 peaks of antibody activity against the infecting clone within 7 weeks, as measured by immunofluorescence, radioimmunoassay, and neutralization of infectivity tests. Using other clones from an unrelated Stock, antibodies to these clones were not detectable, indicating that the antibodies produced were specific to the infecting organisms. These results suggest that there was a reappearance or increase in numbers of the infecting organisms or of organisms with variable surface antigens similar to those of the infecting clones. The reappearance of variable antigen types in the presence of specific antibodies would imply that antibody plays a selective rather than an inductive role in the process of antigenic variation in African trypanosomes.

SUMMARYPrecipitin lines formed between serum from a goat infected with caprine arthritis encephalitis virus (CAEV) and radiolabelled viral proteins in polyethylene glycolconcentrated culture medium were excised from immunodiffusion (ID) plates and analysed by polyacrylamide gel electrophoresis. The two major precipitin lines contained the 135 000 mol. wt. glycoprotein (gp135) and the internal 28000 mol. wt. structural protein (p28). This method obviates the use of purified proteins or monospecific antisera to positively determine viral constituents in ID precipitin lines formed between a crude antigen preparation and antiserum against whole virus.