A recombinant protein (MyxoTLm) for the serological diagnosis of acute and chronic Trypanosoma vivax infection in cattle

Abstract

Human trypanosomiases and animal trypanosomoses are caused by distinct protozoan parasites of the genus Trypanosoma. The etiological agents of bovine trypanosomosis (BT) are T. vivax, T. congolense, or T. brucei, whose acute infections are initially characterized by hyperthermia, following moderate to severe anemia, subcutaneous edema, lethargy, reduced milk production, progressive weight loss, enlarged lymph nodes, reproductive disorders and death. Animals that survive the acute phase might recover and progress to the chronic, often asymptomatic, phase of infection. Despite their low sensitivity due to the characteristic low parasitemia, simple and costless direct parasitological examinations are the preferred diagnostic methods for animals. Thus, most of the epidemiological studies of BT are based on serological techniques using crude antigen. In this study, we describe the use of the MyxoTLm recombinant protein as an antigen on serological assays. Anti-T. vivax IgM and anti-T. vivax IgG ELISA assays using purified MyxoTLm revealed specificity rates of 91.30 % and 95.65 % and sensitivity rates of 82.35 % and 88.23 %, respectively, being higher than reported for crude antigens. Also, MyxoTLm demonstrated a good performance to detect IgM (ROC curve area = 0.8568) and excellent performance to detect IgG (ROC curve area = 0.9565) when compared to a crude antigen. T. evansi crude antigen used in the indirect anti-T. vivax IgM ELISA reached 70.58 % sensitivity and 78.26 % specificity, and had a lower test performance (ROC curve area = 0.7363). When applied to the anti-T. vivax IgG ELISA, the crude antigen reached 82.35 % sensitivity and 69.56 % specificity, also presenting a low performance with area under the ROC curve of 0.7570. Therefore, the use of MyxoTLm as an antigen on serological diagnosis of BT revealed to increase the sensitivity and the specificity if compared to crude antigens.