Development and evaluation of a rapid flow-through immuno filtration test using recombinant filarial antigen for diagnosis of brugian and bancroftian filariasis

There is an imperative need to develop a rapid antibody test that can be used for diagnosis of clinical cases in travelers and expatriates, primary surveillance in areas of unknown endemicity, detection of early infection in childhood and for monitoring chemotherapeutic programs. A rapid-format, simple and qualitative flow through immuno filtration test has been developed for the identification of total IgG antibodies to recombinant filarial antigen WbSXP-1. This test system employs colloidal gold-protein A reagent as the antibody capture reagent. The sensitivity and specificity of the test was evaluated in a total of 1,230 serum samples. The sensitivity of the test was found to be 90.8% with brugian (n=70) and 91.4% with bancroftian (n = 140) microfilaraemic subjects. The test showed minimum reactivity (4/10) with Loa loa microfilaria (MF) positive sera and no reactivity (0/20) with Onchocerca MF positive sera. This rapid diagnosis is found to be non-reactive with individuals having other parasitic diseases including schistosomiasis (n=10), soil-transmitted helminthiases (n=34) and protozoan infections (n=33) indicating the potential of this test as a prospective method of diagnosis for both brugian and bancroftian lymphatic filariasis. Stability kinetics was studied at different temperatures and different time periods. The rapid flow-through immuno filtration test is advantageous since it can be stored at room temperature, is user friendly and is particularly applicable in the field as an initial screening method, for epidemiological monitoring of filarial infections in bancroftian and brugian endemic regions of the world.