Variant Surface Glycoprotein 4, a potential diagnostic candidate for the detection of Trypanosoma brucei rhodesiense infections

In the course of a Human African Trypanosomiasis (HAT) infection, there is a protracted and fluctuating course of parasitaemia during which different variant surface glycoproteins (VSGs) are expressed in a hierarchical fashion, where some VSGs appear preferentially early in infection and others only later. VSG 4; previously found to be one of the most frequently expressed VSGs in early stage of T. b. rhodesiense infections, was chosen as a putative diagnostic VSG candidate in this study. A total of 67 human blood samples from Kenya and Uganda were tested using a VSG 4 based Polymerase Chain Reaction (PCR). VSG 4 protein was also expressed in E. coli and tested for reactivity with HAT patient sera. A detection of 95.8% and 86% among blood samples from Kenya and Uganda respectively was observed in this PCR. Western blot showed a smear around 55-65KDa; probably a VSG, since VSGs have molecular weights in this region. These results suggest that the detection of VSG 4 would make a more sensitive diagnostic assay in the early diagnosis and treatment follow-up of T. b. rhodesiense infections.