Abstract
Protective immunity against human onchocerciasis may best be reflected by the existence of individuals who in spite of exposure to the filarial nematode Onchocerca volvulus do not develop disease (putatively immune). We observed preferential recognition of an O. volvulus antigen of approximately 90 kDa by sera from putatively immune individuals compared with sera from diseased individuals. Screening of an adult worm cDNA library with one serum recognizing this antigen almost exclusively 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. E1 appears to represent a small transcript of the O. volvulus ankyrin gene. The nonfusion protein obtained by expression of the complete E1 cDNA exhibits an apparent molecular mass of 90 kDa on SDS-polyacrylamide gel electrophoresis. An antiserum against the recombinant protein reacts with the 90-kDa antigen in O. volvulus extract. In O. volvulus, E1 was localized in the neuronal cell bodies, the nerve ring, and the extracellular clefts of the basal labyrinth. These results identify an ankyrin-related O. volvulus protein as an immunogen to putatively immune individuals, suggesting that neuronal proteins may be important targets for immunity against O. volvulus in vivo.
Highlights
Human onchocerciasis, a chronic disease caused by infection with the filarial nematode Onchocerca volvulus, affects millions of people in Africa and Latin America (1)
Screening of cDNA Libraries—A gt11 cDNA expression library derived from adult O. volvulus was screened with a serum from a putatively immune individual reactive almost exclusively to the 90-kDa O. volvulus antigen according to described methods (12)
Further analysis of a ZAP cDNA library prepared from adult O. volvulus using a radioactively labeled 157-bp polymerase chain reaction product of the 5Ј end of the known sequence led to the identification of a full-length clone of 2043 bp, designated E1
Summary
A chronic disease caused by infection with the filarial nematode Onchocerca volvulus, affects millions of people in Africa and Latin America (1). Screening of cDNA Libraries—A gt11 cDNA expression library derived from adult O. volvulus was screened with a serum from a putatively immune individual reactive almost exclusively to the 90-kDa O. volvulus antigen according to described methods (12).
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