Diagnosis of Trypanosoma brucei gambiense sleeping sickness using an antigen detection enzyme-linked immunosorbent assay.

A monoclonal antibody-based enzyme-linked immunosorbent assay (antigen ELISA) developed for detection of trypanosome antigens in the serum and cerebrospinal fluid (CSF) of patients as a means for diagnosis of Trypanosoma brucei gambiense sleeping sickness was evaluated at the Bureau Central de la Trypanosomiase, Kinshasa, Zaire. Sixty-nine (89.6%) of 77 parasitologically confirmed cases examined at the Daloa clinic had antigens in serum; 35 (45.5%) had antigens in CSF and, in 4 of these, the antigens were detected in CSF only. Taking the serum and CSF results together, 73 (94.8%) of the 77 patients were positive in the assay. In the Kinshasa series, 168 (89.4%) of 188 parasitologically confirmed cases were positive by antigen ELISA. The controls, who included 165 blood donors and 40 patients with malaria, 2 with hydatidosis and 12 with leishmaniasis, were negative by antigen ELISA. Analysis of CSF results for 35 patients who had antigens in CSF revealed that 34 (97.1%) had elevated CSF white cell counts, 29 (82.9%) had elevated protein levels, and 23 (65.7%) had trypanosomes in their CSF. Moreover, analysis of results for 34 patients whose CSF had been shown to harbour trypanosomes by the double centrifugation technique showed that 24 (70.6%) had antigens in CSF, 28 (82.6%) had elevated protein levels, and 33 (97.1%) had elevated CSF white cell counts. Antigens were rapidly cleared from peripheral circulation following institution of treatment. Antigen clearance was accompanied by a rapid fall in CSF protein levels and white cell counts. These results demonstrate the potential of antigen ELISA, not only as a tool for diagnosis, but also for clinical staging and treatment follow-up of patients with T. b. gambiense sleeping sickness.