The invariant surface glycoprotein ISG75 : a target for vaccination and diagnosis of trypanosomiasis

Trypanosomes are flagellated kinetoplastid protozoa that diverged early in the evolution of the eukaryotic lineage. These unicellular parasites cause fatal diseases in both mans and animals; yet attempt of trypanosome eradication so far have been an impossible challenge. Human African trypanosomiasis or sleeping sickness is the third most important global burden of parasitic diseases after malaria and schistosomiasis. The causative agent Trypanosoma brucei is transmitted by tsetse flies of the Glossina genus that infects a vast sub-saharan region covering 36 countries. Currently sleeping sickness threatens more than 50 million people and causes high morbidity and mortality in the endemic countries. While there is little prospect of anti-trypanosome vaccination, the treatment of sleeping sickness is toxic. Once the trypanosomes penetrate the central nervous system, the arsenical-based medication alone causes reactive encephalopathy in 10% of the patients, 50% of which result in mortality. The disease, in either chronic or acute form, is invariably fatal if untreated and provokes great social and economic constraints. Animal trypanosomiasis is the most important livestock disease in Africa. T.congolense, T. vivax and T. brucei causing the wasting disease nagana are transmitted by the tsetse flies, thus rendering 10 million km2 of grazing land in the sub-Saharan region unsuitable for livestock production. Furthermore, T. evansi causing surra is spread outside the African continent into South America, the Middle East, Asia and Europe, and T. vivax also occurs in Latin America, as these two species are transmitted mechanically by haematophagous biting flies. T.equiperdum, causing dourine, is distributed through sexual contacts among equines. Trypanosome infections influence every aspect of animal production, including poor meat and milk production, poor growth of young stock, loss of stamina and strength, reduction of fertility and high rates of mortality. Trypanosomiasis can induce immune-suppression, rendering the animals more susceptible to secondary infections, such as by Clostridium spp and Bacillus anthracis. In Africa, animal trypanosomiasis kills approximately 3 million cattle each year, with a further 50 million at risk from the disease. Therefore, trypanosomiasis has huge impacts on public health and rural development, both through direct human infections and considerable loss on animal production.