IMMUNITY TO ONCHOCERCIASIS - IDENTIFICATION OF A PUTATIVELY IMMUNE POPULATION IN A HYPERENDEMIC AREA OF ECUADOR

The existence of immunity to Onchocerca volvulus (Ov) infection is sug gested by the presence of uninfected persons in hyperendemic areas. A major barrier to the study of immunity has been the correct identifica tion of putatively immune (PI) subjects. To identify a PI group in a h yperendemic area in Ecuador, clinical and epidemiologic information wa s combined with a polymerase chain reaction (PCR)-based assay identify ing Ov DNA in skin snips and a recombinant antigen-based ELISA. Compar ison of immune responses revealed that PI subjects had significantly l ower levels of Ov-specific IgG, IgG subclasses, and IgE than infected (INF) subjects. Female subjects were significantly more likely to be P I than male subjects, and INF female subjects had significantly lower levels of Ov-specific IgG, IgG1, and IgG3 than Inf male subjects. Thus , the use of molecular-based techniques has helped to define more prec isely the PI state in onchocerciasis.