@entity3177 contains a repertoire of more than 100 different genes for Variant Surface Glycoproteins (VSGs). A small and strain-specific fraction of these genes is expressed in the salivary glands of the tsetse @entity238 (M-genes), giving rise to metacyclic Variable Antigen Types (M-VATs). Antibodies produced in a chronic trypanosome infection initiated by syringe inoculation of bloodstream forms into mammals (i.e. against B-VATs), will react with most of the M-VATs suggesting that these B-VATs express @entity69202 genes that are similar or identical to M-genes. We have cloned DNA complementary to the @entity69202 mRNA of four of such B-VATs and used this to characterize the corresponding @entity69202 genes. In three of the four VATs we find a single @entity69202 gene hybridizing with the cDNA probe and we provide supporting evidence that this gene is expressed as an M-gene. In the bloodstream repertoire these genes appear to be activated by duplicative translocation to another telomere. In all four variants the putative M-genes are telomeric and in the three cases where the location of the genes on chromosome-sized DNA molecules could be determined, the genes were located in large DNA, whereas the majority of the telomeric @entity69202 genes are in chromosomes less than 1000 kb. Our results are best explained by models for M-gene activation involving telomeric expression sites for these genes which are separate from those used by bloodstream forms. The implications of these results for vaccination are discussed.

Characteristics of trypanosome variant antigen genes active in the tsetse XXXX .

@entity69202 :: ('39137(Tax:7227)', 'Gene') :: ['VSG'] @entity238 :: ('7227', 'Species') :: ['fly'] @entity3177 :: ('5691', 'Species') :: ['Trypanosoma brucei']
@entity238 :: (7227,Species) :: ['fly']
