A four year follow up study of filaria specific IgE response in individuals with hydrocele.

BACKGROUND & OBJECTIVES: Hydrocele is the most common clinical manifestation in males infected with Wuchereria bancrofti. IgE response to a filarial allergen Sd30 was evaluated in hydrocele patients living in a W. bancrofti endemic region of Orissa, India. METHODS: IgE levels to Sd30, an antigenic fraction isolated from Setaria digitata, were determined by ELISA in sera from patients of filariasis (n = 93). IgG and IgM levels were also determined. RESULTS: It was observed that microfilaraemic patients with hydrocele (n = 16) exhibited considerably reduced (P < 0.01) IgE levels in comparison to hydrocele patients without microfilariae (n = 27) and to other filarial groups (elephantiasis, asymptomatic microfilaraemics). The reduced IgE response in microfilariae positive patients with hydrocele persisted even after a gap of four years in the majority of patients. INTERPRETATION & CONCLUSIONS: The results show low IgE levels in microfilaraemic patients with hydrocele in comparison to other groups in filaria endemic regions. The exact mechanism of this reduction in IgE is not known but these patients make a distinct group in filaria endemic regions and should be considered separately for immunological evaluation.

Diagnostic use of filarial antibody and antigen isolated from hydrocele fluid for human filariasis.

Paired samples of serum and hydrocele fluid of filarial patients associated with hydrocele were analysed for filarial antibody and antigen. Sera samples showed higher titers of filarial antibody and antigen compared to their corresponding hydrocele fluid samples. HFIgG isolated from hydrocele fluid was equally useful as FSIgG isolated from serum and detected filarial antigen in 23 out of 26 microfilaraemic sera, 7 out of 10 chronic sera and 3 out of 18 endemic normal sera by inhibition ELISA. Filarial antigen was isolated from hydrocele fluid. In inhibition ELISA antigen fraction, HFA-9 (20-25 kDa) isolated by sodium-dodecyl sulphate-polyacrylamide gel electrophoresis showed high reciprocal antigen titer of 2048. This active antigen fraction was evaluated for its diagnostic utility in comparison with Wuchereria bancrofti microfilariae excretory-secretory antigen (Wb mf ES Ag) in inhibition ELISA. Both antigen preparations detected filarial antigen in about 80% of microfilaraemic sera, 60% chronic sera and 20-30% of endemic normal sera. This study showed that antibody and antigen isolated from hydrocele fluid were equally sensitive as FSIgG and Wb mf ES Ag in the detection of filarial antigen by inhibition ELISA. Thus hydrocele fluid may be used as an alternative source for the isolation of antibody and antigen of immunodiagnostic importance.