A monoclonal antibody-based enzyme immunoassay for detecting parasite antigenemia in bancroftian filariasis.

We evaluated a monoclonal antibody-based enzyme immunoassay for detecting soluble parasite antigen in sera collected in an area in South India endemic for Wuchereria bancrofti. Filarial antigen was detected in sera from 56 of 57 microfilaremic patients, 9 of 64 aminofilaremic patients with clinical filariasis, and 11 of 70 endemic controls. Antigen was not detected in sera from patients from nonendemic areas who had a variety of other filarial and nonfilarial helminth infections. Parasite antigen titers were significantly correlated with microfilarial counts in night blood smears (r = .64, P less than .01). Negative antigen tests in patients with clinical filariasis may be explained in part by antibody-mediated clearance of circulating antigen. Antibodies to circulating W. bancrofti antigen were detected in 41 of 55 antigen-negative sera from patients with clinical filariasis. Despite this limitation, detecting parasite antigen by enzyme immunoassay provides significant advantages over previously available methods for diagnosing active W. bancrofti infection.