ABSTRACT
The African trypanosomiases are exceedingly amenable to control by vaccination. Accordingly, trypanosomes are rapidly recognized and destroyed by the immune system. As infection with Trypanosoma brucei proceeds, the host mounts strong antibody responses against the highly immunogenic variant surface glycoprotein (VSG) and clears the parasitemia. The inescapable conclusion is that vaccination based on tackling the sequence of appearance of variable antigen types (VATs) has been selected against in trypanosome evolution. Trypanosoma rhodesiense displays major differences between locations although within a given focus only one serodeme may be present. In common with what has been observed for other simple organisms, the trypanosome's genome is efficiently organized. The general immunosuppression which occurs in small laboratory animals during chronic trypanosome infection is well recorded and well reviewed. If the trypanosome is diverting host molecules to its own ends, the host and parasite will in many cases use biochemically very similar systems.
