Rapid Wuchereria bancrofti-Specific Antigen Wb123-Based IgG4 Immunoassays as Tools for Surveillance following Mass Drug Administration Programs on Lymphatic Filariasis

The Global Programme to Eliminate Lymphatic Filariasis has an urgent need for rapid assays to detect ongoing transmission of lymphatic filariasis (LF) following multiple rounds of mass drug administration (MDA). CurrentWHO guidelines support using the antigen card immunochromatographic test (ICT), which detects active filarial infection but does not detect early exposure to LF. Recent studies found that antibody-based assays better serve this function. In the present study, two tests, a rapid IgG4 en-zyme-linked immunosorbent assay (ELISA) and a lateral-flow strip immunoassay, were developed based on the highly sensitive and specificWuchereria bancrofti antigenWb123. A comparison ofW. bancrofti-infected and-uninfected patients (with or without other helminth infections) demonstrated that both tests had high sensitivities and specificities (93 and 97 % [ELISA] and 92 and 96 % [strips], respectively). When theW. bancrofti-uninfected group was separated into those with other filarial/hel-minth infections (i.e., onchocerciasis, loiasis, and strongyloidiasis) and those who were parasite uninfected, the specificities of the assays varied between 91 and 100%. In addition, the geometric mean response by ELISA ofW. bancrofti-infected patients was significantly higher than the response of those withoutW. bancrofti infection (P< 0.0001). Furthermore, theWb123 ELISA and the lateral-flow strips had high positive and negative predictive values, giving valuable information on the size of survey population needed to be reasonably certain whether or not transmission is ongoing. These highly sensitive and specific IgG4 tests to theW. bancroftiWb123 protein give every indication that they will serve as useful tools for post-MDAmonitoring. The Global Programme to Eliminate Lymphatic Filariasis(GPELF), begun in 2000, has led to 952 million treated indi