Evaluation of fractionated circulating filarial antigen in diagnosis of bancroftian filariasis.

Circulating filarial antigen (CFA) isolated from the plasma of microfilaraemic patients was fractionated on an Ultrogel ACA 34 column. The second protein peak (CFA2) showing filarial antigen was further fractionated by DEAE-cellulose column chromatography into two fractions (CFA2 DE1 and DE2). CFA2 DE1 fraction, showing antigenic activity, was further evaluated in an ELISA for its diagnostic use in bancroftian filariasis. Studies with CFA2 DE1 and anti-CFA2 DE1 antibody showed that they were highly active in the detection of filarial antibody and antigen in asymptomatic microfilaraemia sera and thus obviate the need for the tedious night blood collection and examination. Fractionated filarial plasma can be another candidate antigen for immunodiagnosis of bancroftian filariasis.

Filarial antigen, antibody and circulating immune complexed antigen levels in Bancroftian filariasis by stick ELISA.

Filarial antigen, antibody and circulating immune complexed antigen (CIC-Ag) profiles were studied by stick ELISA in the sera of patients who were in different stages of Bancroftian filarial infection. The geometric mean titres (GMT), of filarial IgG antibody in patients with microfilaraemia (424) and all three grades of clinical filariasis (1485, 3845 and 40216 for grades I, II and III respectively), were significantly higher than in normal controls from endemic areas (47). If a filarial antibody titre of greater than 300 is considered positive, the sera of 94% of patients with microfilaraemia and all those with clinical filariasis were positive. The sera of only 11% of normal subjects from endemic areas and none from non-endemic areas were positive for filarial antibody. The antibody titres were significantly higher in patients with grades II and III clinical filariasis than in those with grade I clinical filariasis or microfilaraemia. Analysis of sera for filarial antigen by inhibition ELISA showed higher GMTs in patients with microfilaraemia (5778) and grades I (3917) and II (676) clinical filariasis compared to grade III (66) clinical filariasis or normal subjects from endemic areas (57). Thus 81% of patients with microfilaraemia, 85% with grade I, 88% with grade II and 20% with grade III clinical filariasis and none of the normal subjects from either endemic or non-endemic areas had a filarial antigen titre of greater than 300. CIC-Ag was found to be present in 8% of patients with grade I, 21% with grade II and 79% with grade III clinical filariasis and in none of those with microfilaraemia or normal controls. While the detection of filarial antibody is useful for diagnosing. microfilaraemia and clinical filariasis, the detection of filarial antigen may be superior for diagnosis of microfilaraemia and grade I clinical filarial infection. Assay of CIC-Ag is useful for diagnosing a grade III clinical infection in the absence of microfilariae in the blood.

Wb E34 monoclonal antibody: further characterization and diagnostic use in bancroftian filariasis.

The Wb E34 monoclonal antibody raised against Wuchereria bancrofti microfilarial excretory secretory (mf ES) antigen was reported to be useful in detecting the filarial antigen in W. bancrofti and Brugia malayi infected sera. Further studies in this laboratory showed that this monoclonal antibody reacts with a stage-specific antigen of W. bancrofti filarial parasite. Wb E34 identified three antigenic components with molecular weights, 55, 57.5, and 63 kilodaltons (Kd) in western blot analysis. The target antigen of Wb E34 was found to be located in the cytoplasm of microfilariae by indirect immunofluorescence technique. The inhibitory antibodies to Wb E34 were detected in a higher percentage of microfilaraemic sera (81%) than in clinical filarial (33%) or tropical eosinophilia sera (35%). Thus the inhibition ELISA using W. bancrofti mf ES antigen and Wb E34-penicillinase may be useful in detecting the filarial antibody associated with the active stage of infection.