Immunology
The prospect of a vaccine for human trypanosomiasis is bleak. This pessimism is occasioned in part by the trypanosome’s ability to alter rapidly surface antigens, apparently to evade the host’s humoral immunity.
Nevertheless, immune mechanisms may be involved in several aspects of the disease. This is probably the case for endemic gambiense disease in western and central Africa, where sleeping sickness is known to be an ancient disease, and where early field workers sometimes observed the phenomenon of asymptomatic carriers. During gambiense infection, trypanosomes multiply, and, with increased parasitemia, the victim suffers fever after which the parasitemia recedes in apparent response to the production of antibodies. Soon the parasites again multiply, but this generation produces antigenic material against which the previous antibodies are ineffective. It is this phenomenon of “antigenic variation” that greatly reduces the prospect of producing an effective vaccine, and at present very little research is underway on vaccine development (Boothroyd 1985).
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