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

Abstract

bThe 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). Current WHO 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 enzyme-linked immunosorbent assay (ELISA) and a lateral-flow strip immunoassay, were developed based on the highly sensitive and specific Wuchereria bancrofti antigen Wb123. A comparison of W. 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 the W. bancrofti-uninfected group was separated into those with other filarial/helminth 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 of W. bancrofti-infected patients was significantly higher than the response of those without W. bancrofti infection (P < 0.0001). Furthermore, the Wb123 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 the W. bancrofti Wb123 protein give every indication that they will serve as useful tools for post-MDA monitoring.

Rapid Point-of-Contact Tool for Mapping and Integrated Surveillance of Wuchereria bancrofti and Onchocerca volvulus Infection

“…We recently reported on the performance of the Wb123 lateral flow strips using a panel of sera from patients with W. bancrofti, O. volvulus, L. loa, and Strongyloides stercoralis, as well as sera from non-helminth-infected individuals (11). A subset of these sera was also used to analyze the performance of Ov16 in a single antigen format strip (10).…”

“…The protocol for the production of the lateral flow strips and for testing the strips with serum (and whole blood) has been described previously (10,11), and the present study utilized a second-generation design to allow for the striping of both antigens with similar results in sensitivity and specificity (Fig. 1A).…”

“…The protocol for testing the strips was identical to that described previously (11). Briefly, 2.5 l of patient serum or plasma was added to the nitrocellulose membrane on the test strip approximately 4 mm from the conjugate pad, and the strip was then placed vertically in a well of a flatbottom plate with 100 l of lateral flow test running buffer.…”

“…Fortunately, Ov16 and Wb123 antigens have recently been developed as individual, standalone, rapid (10-to 20-min) lateral flow tests for point-of-contact detection of O. volvulus-specific or W. bancrofti-specific IgG4 antibodies (10)(11)(12). These tests can be used with serum, whole blood, or eluates of dried blood spots and have been shown to detect specific antibodies in individuals with infections that span many geographically diverse regions of the world where filarial infection is endemic.…”

Expanding the MDx toolbox for filarial diagnosis and surveillance

“…A Brugia Rapid TM test (Reszon Diagnostics, Malaysia), which detects antibodies to BmR1 in both B. malayi and B. timori infections, is commercially available [19]. For bancroftian LF, a recently developed rapid IgG4 ELISA and a lateral-flow strip immunoassay based on the Wb123 antigen were reported [20]. Similarly, for diagnosis of L. loa infection, assays based on antibody responses to recombinant antigens Ll-SXP-1 [21] and repeat 3 of the nematode polyprotein antigen [22] were proposed.…”