Absence of the LiTat 1.3 (CATT antigen) gene in Trypanosoma brucei gambiense stocks from Cameroon

Antibodies to the variable antigen type (VAT) designated LiTat 1.3 are common in sera from parasitologically confirmed patients with gambian sleeping sickness. For this reason, LiTat 1.3 has been considered a suitable antigen for detecting Trypanosoma brucei gambiense in the Card Agglutination Test for Trypanosomiasis (CATT; Testryp-CATT, Smith Kline-RIT). However, surveys in the T.b. gambiense endemic focus of Fontem in Cameroon have suggested that expression of LiTat 1.3 might be rare or absent. We show here that the gene for LiTat 1.3 was indeed absent from some T.b. gambiense stocks isolated from this focus, and a LiTat 1.3-like gene was present in others. The divergent gene differed from the cloned version of LiTat 1.3. In addition, antibodies to LiTat 1.3 could not be detected in rabbits infected with either of the two kinds of T.b. gambiense from the Fontem area. We suggest that the absence of LiTat 1.3 expression in this focus may have important implications for the epidemiology and control of sleeping sickness, especially if heavy reliance is placed on the CATT.