Characterization of Trypanosomes and Determination of Trypanosome Immunogenic Proteins in Cattle in Ghana

Abstract

Livestock production is one of the farming systems and has a great impact on food and economic security in most developing countries. Animal African trypanosomiasis is a major limitation to livestock production in Africa, particularly cattle production. The disease is caused by Trypanosoma spp., a broad range of protozoan parasites of wild and domestic animals through cyclical and mechanical transmission. Cross-sectional studies conducted in Ghana reveal the common species of trypanosomes infecting cattle using molecular techniques as T. brucei brucei, T. congolense, T. vivax, T. theileri and T. simiae. Despite the seriousness of the disease, no study has been conducted on lifetime trypanosome infections in Ghanaian cattle. Antigenic variation of the variant surface glycoprotein (VSG) of trypanosomes is a hindrance to the successful development of a vaccine against trypanosomiasis. Therefore, alternative approaches such as exploiting the immunogenicity of other trypanosomes proteins and understanding antibody response during lifetime infection with parasites maybe useful in vaccine development. In this study, trypanosome species throughout the natural infection cycle in cattle were characterized over a two year period. In addition, the antibody response in the individual cattle over time and potential trypanosome immunogenic proteins were determined. Two herds of cattle (20 each) at Accra and Adidome were selected on the basis of geographical location, tsetse fly density, trypanosomiasis prevalence and the breed of cattle at the sites. Blood and serum samples were collected at approximately four to five-week intervals for about two years. The infecting trypanosomes were identified and characterized using an in-house developed tagged multiplex nested polymerase chain reaction (PCR) targeting a portion of the trypanosome tubulin gene cluster and next generation sequencing. Total GUTat 3.1 T. brucei protein were prepared and antibody reactivity against T. brucei proteins as well as identified T. brucei immunogenic proteins recognized by cattle sera were performed by indirect ELISA, SDS-PAGE, western blot, immunoprecipitation and LC-MS/MS. Cattle were infected throughout the natural infection cycle at both study sites, Adidome and Accra with cases of mixed infections. T. vivax, T. brucei, T. theileri and T. congolense were the major infecting species at both study sites with T. vivax being predominant [incidence rate of 84% (282 samples) for Adidome and incidence rate of 70.3% (353 samples) for Accra]. T. vivax was also the principal trypanosome species existing within both young and old aged cattle, among males and females and the different cattle breeds at both study sites. Cattle sera (215 samples) had high antibody response at Adidome with a seroprevalence of 97% compared to Accra with a seroprevalence of 73% out of 172 sera samples. Mass spectrometric analysis of the T. brucei proteins immunoprecipitated by trypanosome immune antibodies identified beta-tubulin and triosephosphate isomerase to be selectively recognized by infected sera in natural infection. Data from this study has given an insight on the biology of trypanosome infection and informed policy makers of better control measures to be adopted in the infected area. In addition possible biomarkers have been identified for diagnosing cattle trypanosomiasis in Ghana and for potential vaccine development.