NOVEL CUTICULAR COLLAGEN OVCOL-1 OF ONCHOCERCA-VOLVULUS IS PREFERENTIALLY RECOGNIZED BY IMMUNOGLOBULIN G3 FROM PUTATIVELY IMMUNE INDIVIDUALS

The cDNA sequence encoding an Onchocerca volvulus collagen, Ovcol-1, h as been isolated and the corresponding native antigen has been identif ied. The cDNA encodes an open reading frame of 96 amino acid residues containing and uninterrupted 66-residue Gly-X-Y repeat triple-helical (TH) domain (where X and Y may be any amino acids) flanked by a 26-res idue amino non-TH domain and a 4-residue carboxyl non-TH domain. The s ize (9.7 kDa) and structure of the deduced molecule are unique among p reviously identified collagen chains. This novel collagen type has bee n designated ''mini-chain collagen.'' Native Ovcol-1 is aqueous solubl e and resolves by sodium dodecyl sulfate-polyacrylamide gel electropho resis at 14.2 kDa under reducing conditions. Immunoelectron microscopy of adult female O. volvulus localized Ovcol-1 to the cuticles of both the adult worm and uterine microfilaria. A group of individuals from an area in Ecuador where O. volvulus is hyperendemic have been classif ied as putatively immune (PI) to O. volvulus infection. Analysis of th e humoral immune responses to Ovcol-1 demonstrated that immunoglobulin G3 (IgG3) of PI individuals preferentially recognized this antigen in comparison to IgG3 of infected individuals.