Cloning of specific diagnostic antigens of Onchocerca volvulus

Specific, serological diagnosis is one of the main goals in onchocerciasis research. To date this objective has been hampered by (a) scarcity of parasite material, and (b) antigenic cross-reaction between Onchocerca volvulus and other nematode species. In order to obtain specific antigens, and in amounts suitable for study, molecular biological techniques have been adopted. A lambda gt11 cDNA expression library prepared from O. volvulus adult female worms was screened using infected human sera from onchocerciasis patients and rabbit hyperimmune sera raised against Onchocerca and genus-specific Onchocerca antigen extracts. Five clones were selected and their inserts expressed as beta-galactosidase fusion proteins. The fusion proteins were examined using individual sera from patients with O. volvulus or Wuchereria bancrofti infections. Three of the fusion proteins were recognised by more than 80% of O. volvulus sera and exhibited weak reactivity with a few W. bancrofti sera. One of these three clones was recognised to a significantly greater degree by sera from sowda than from generalised onchocerciasis patients.