Antibody response to a filarial antigen fraction in individuals exposed toWuchereria bancrofti infection in India

An antigen fraction (Dssd(I)) was isolated from the aqueous-insoluble compo nents of adult Setaria digitata. Rabbit antiserum to Dssd(I) labeled the sh eaths of Wuchereria and Setaria microfilariae suggesting Dssd(I) to be surf ace associated. Antibody responses to Dssd(I) were determined in Wuchereria in bancrofti exposed individuals. IgM titre was highest in endemic normals (EN; asymptomatic amicrofilaraemic) followed by chronic filarial patients (CP) and asymptomatic microfilaraemics (AS). IgG titer was high in both chr onic filariasis and endemic normals. The microfilaraemic group had the lowe st titer. The seropositivity rate in AS was 28% for IgG and 10% for IgM, in CP 100% for IgG and 33% for IgM, and in EN 86% for both antibodies. An age -dependency of IgM but not of Ige antibodies was observed in endemic normal s, with IgM prevalence reaching a plateau by 12 years of age. The subclass composition of the antibody response to Dssd(I) appeared to be primarily Ig G(3) in endemic normals, IgG(1) in chronic filariasis and IgG(4) in asympto matic microfilaraemics. Diethylcarbamazine (DEC) treatment led to a signifi cant increase in IgG and IgM levels in microfilaraemic individuals, Of inte rest, the expression of IgG subclasses altered. There was an increased IgG( 3) and IgG(1) response associated with a reciprocal decrease in IgG(4) foll owing DEC therapy. (C) 1999 Elsevier Science B.V. All rights reserved.