The effect of diethylcarbamazine treatment of Bancroftian filariasis on the immunological reactivity of microfilaraemic individuals

Patent filarial infection has been correlated with a profound suppression of humoral and cellular responses to filarial antigens. In the present study, the filarial antigen-specific humoral and cellular reactivity of 30 Haitian subjects with patent Wuchereria bancrofti infection was monitored before and after treatment with diethylcarbamazine. Microfilarial density was reduced from a pre-treatment mean of 1778/ml to 9/ml, with residual microfilaraemias detectable in 10 subjects. Peripheral blood mononuclear cells from 18 of the 30 patients responded to an extract of Brugia pahangi before treatment, and this number increased to 25 after treatment. There was no significant change in the mean level of response to B. pahangi in patients who were responsive to filarial antigen before treatment; however, the mean responsiveness to B. pahangi of individuals who were classified as nonresponders before treatment was significantly increased following treatment. Cellular reactivity to purified protein derivative and geometric mean titres to soluble B. pahangi, measured by enzyme-linked immunosorbent assay, were unaffected by treatment. Similarly, most post-treatment sera did not recognize new B. pahangi bands on Western blots, compared to pre-treatment controls. These observations imply that the relationship between microfilariae and immunosuppression is complex.