It was hoped that a vaccine could be developed against this disease but the work of Keith Vickerman and colleagues showed that the host is not able to mount and effective immune response against the parasite because the trypanosome presents antigenic variation, constantly changing its outer surface producing variable antigen types (VATs).

In the tsetse fly the trypanosome are referred to as metacyclic forms and Vickerman's work of focused on these forms because it had been suggested that trypanosome population revert to a 'basic' antigen type at the end of their cyclical development in the tsetse fly's salivary glands. Prospects of vaccination, and of early serodiagnosis of trypanosomiasis, would be greatly improved by use of such a basic VAT.

Keith Vickerman

"The teacher read to us from Paul de Kruif’s The Microbe Hunters. I was spellbound"

However, using new specific immunofluorescence and immune lysis tests it was possible to identify the VAT of individual trypanosomes and the results showed that VAT heterogeneity was present in the metacyclic population and it did not revert back to a basic antigenic type which could be used for the development of a vaccine.

The implications of this finding have had a huge impact on subsequent research on trypanosomiasis.