Instituto de Investigaciones, Universidad del Valle de Guatemala, Division of Parasitic Diseases, Center for Infectious Diseases, Centers for Disease Control, Public Health Service, U.S. Department of Health and Human Services, Apartado Postal 82, Guatemala, Guatemala, Georgia
An enzyme-linked immunosorbent assay (ELISA) using a crude soluble antigen from adult Onchocerca volvulus was developed and used as a serodiagnostic test for Guatemalan onchocerciasis. A total of 456 sera from residents in an area with endemic onchocerciasis were tested, and results were compared with previous findings by the indirect fluorescent antibody (IFA) test on the same population. Control “normal” sera from 50 U.S. residents were also tested, as were 144 sera from persons who lived in an area not endemic for onchocerciasis but who had a variety of other helminthiases. None of the “normal” sera were ELISA-positive at a serum dilution of 1:160; however, sera from persons with other intestinal helminths showed cross-reactivity in 17.4% of the individuals tested. A total of 84.4% of the individuals from the endemic area had ELISA endpoints of 1:160 or greater. Only 2.6% of the individuals who were shown to be infected by the presence of microfilariae in skin snips had ELISA titers of less than 1:160. Upon partial separation of proteins of O. volvulus by isoelectric focusing, four of the six major protein peaks were found in the acidic range (pH 3.1 to 6.8) while two were in the alkaline range (pH 9.55 to 10.9). Four major antibody reactive peaks were observed, all of which were in the acidic range. In these findings the ELISA test proved to be more sensitive for the detection of antibodies than the IFA test and could be employed in the future as a valuable tool for seroepidemiologic studies. In addition, the use of partially separated antigenic components may improve the specificity of the test.