cDNA clones of Onchocerca volvulus low molecular weight antigens provide immunologically specific diagnostic probes.
We report here a panel of cDNA clones from Onchocerca volvulus which were isolated on the basis of being uniquely recognised by onchocerciasis sera and not by sera from patients infected with the major lymphatic filarial nematode parasite Wuchereria bancrofti. Over 90% of O. volvulus recombinants from a primary screen were found to cross-react with lymphatic filariasis sera and were discarded. The subset of specific clones, selected with pooled sera, was then screened with panels of individual patient sera. Individual onchocerciasis cases showed a highly heterogeneous pattern of recognition of recombinant peptides, but several clones were identified which could be combined in a cocktail of antigenic epitopes to successfully detect all infected cases in the study. All these clones encode low molecular weight proteins of the parasite, confirming earlier reports that antigens of this size class show greater species specificity. Several clones encode proteins of 20-23 kDa, the same molecular weight range as the major surface protein of adult worms. The two most commonly recognised clones, Ov22/31M and Ov20/36M were subcloned into the vector pNGS 8 which produces fusion proteins attached to a polyasparagine leader. The fusion peptides of both Ov22/31M and Ov20/36M were soluble and easily purified by gel filtration. Purified fusion protein was used in ELISA to assess reactivity of infected patients giving 90% sensitivity with 100% specificity.
Department of Biology, Imperial College of Science, Technology and Medicine, London, U.K.
J E
JE
Bradley
R
R
Helm
M
M
Lahaise
R M
RM
Maizels
D000818:Animals; D000947:Antigens, Helminth / Q000235:genetics / Q000276:immunology*; D015153:Blotting, Western; D002850:Chromatography, Gel; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D015342:DNA Probes; D004797:Enzyme-Linked Immunosorbent Assay; D015801:Helminth Proteins / Q000235:genetics / Q000276:immunology*; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics; D008970:Molecular Weight; D009854:Onchocerca / Q000235:genetics* / Q000276:immunology; D009855:Onchocerciasis / Q000175:diagnosis; D011993:Recombinant Fusion Proteins / Q000276:immunology; D014958:Wuchereria bancrofti / Q000276:immunology
D000947:Antigens, Helminth; D015342:DNA Probes; D015801:Helminth Proteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D004247:DNA