A MONOCLONAL BLOCKING-ELISA FOR DETECTION OF ORTHOPOXVIRUS ANTIBODIESIN FELINE SERA

A double sandwich blocking-ELISA using a genus-specific neutralizing m onoclonal antibody (MAb) against the vaccinia virus 32 kD adsorption p rotein (D8L open reading frame; ORF) was developed to detect orthopoxv irus (OPV) antibodies in sera. A collection of 2173 feline serum sampl es was examined in an epidemiological study. The blocking-ELISA reveal ed 44 (2%) sera with positive titres of 1:2-1:256. ELISA results were confirmed by the plaque-reduction test. A close correlation between ti tres of both assays could be observed (r = 0.986). In general, the sen sitivity of the blocking ELISA was two to four times higher. Neutraliz ing OPV-antibodies were found in nine sera with ELISA-titres > 1:4. An tibody specificity to OPV was also demonstrated by Western blotting an alysis with selected feline sera. The epidemiographical distribution o f the ELISA-positive sera and case histories of 37 seropositive cats a vailable from the referring veterinarians are demonstrated. The blocki ng-ELISA enables a rapid serological diagnosis and can be used in vete rinary and human medicine. It allows OPV-antibody screening in human a nd other animal species.