Lymphatic filariasis in man: demonstration of circulating antigens in Wuchereria bancrofti infection.

Five hundred and twenty-nine sera obtained from people dwelling in an area endemic for bancroftian filariasis were analysed for the presence of soluble circulating antigens (SCA) of filarial origin by counter immunoelectrophoresis and 303 were found positive. It, therefore, appears that 57.3% subjects could be diagnosed by the detection of SCA irrespective of their clinical status. Of the three groups investigated, microfilaraemic, amicrofilaraemic and clinical, SCA could be demonstrated in maximum number of sera obtained from clinical cases. The parasite specificity of the SCA was determined by enzyme linked immunosorbent assay (ELISA), immunofluorescent antibody test (IFAT), counter immunoelectrophoresis (CIEP) and gel diffusion (GD) using antisera raised against Litomosoides carinii in rabbits and antigens derived from Wuchereria bancrofti microfilariae or antigens present in sera of patients with bancroftian filariasis. This anti-carinii hyperimmune serum under study did not show positive reactions with parasites other than filaria, or with the sera obtained from pre-immunized rabbits and non-endemic controls. A demonstration of a distinct precipitin band in CIEP and GD indicates that either monospecific hyperimmune sera or monoclonal antibodies could be raised for the development of a simple method for immunodiagnosis of bancroftian filariasis.