MOLECULAR-CLONING, EXPRESSION, AND LOCALIZATION OF E1, AN ONCHOCERCA-VOLVULUS ANTIGEN WITH SIMILARITY TO BRAIN ANKYRIN

Protective immunity against human onchocerciasis may best be reflected by the existence of individuals who in spite of exposure to the filar ial nematode Onchocerca volvulus do not develop disease (putatively im mune). We observed preferential recognition of an O, volvulus antigen of approximately 90 kDa by sera from putatively immune individuals com pared with sera from diseased individuals, Screening of an adult worm cDNA library with one serum recognizing this antigen almost exclusivel y led to the identification of a full length clone of 2043 base pairs designated E1. The open reading frame of 462 amino acid residues shows similarity to human brain ankyrin, El appears to represent a small tr anscript of the O. volvulus ankyrin gene. The nonfusion protein obtain ed by expression of the complete E1 cDNA exhibits an apparent molecula r mass of 90 kDa on SDS polyacrylamide gel electrophoresis. An antiser um against the recombinant protein reacts with the 90-kDa antigen in O , volvulus extract. In O. volvulus, El was localized in the neuronal c ell bodies, the nerve ring, and the extracellular clefts of the basal labyrinth, These results identify an ankyrin-related O, volvulus prote in as an immunogen to putatively immune individuals, suggesting that n euronal proteins may be important targets for immunity against O. volv ulus in vivo.