Genomic rearrangements correlated with antigenic variation in Trypanosoma brucei.

The capacity of African trypanosomes to express sequentially a large repertoire of different surface antigens during an infection enables the parasite to evade the immune response of its host, and makes attempts to produce a vaccine against the disease difficult. It is evident that point mutations cannot account for antigen diversity. Variable antigens like immunoglobulins are derived from an extensive family of genes of which only one is expressed in a given cell. As somatic tic recombination is involved in the immunoglobulin gene system, this similarity prompted us to search for somatic rearrangements in trypanosome variable antigen genes. We have constructed a recombinant plasmid containing approximately half the DNA sequence coding for a Trypanosoma brucei variable antigen and hybridised the inserted sequences to various restriction enzyme digests of nuclear DNA from different trypanosome clones. Differences in the sizes of restriction tion fragments hybridising to the inserted variable antigen coding sequence show altered positions of enzyme sites relative to this sequence, indicating different arrangements of DNA sequences around this gene in different trypanosome clones.