Monoclonal antibody-based competitive enzyme-linked immunosorbent assay for detection of morbillivirus antibody in marine mammal sera

A competitive enzyme-linked immunosorbent assay (cELISA), using two monoclo nal antibodies (MAbs), was developed and compared with the standard virus n eutralization test (VNT) for detecting antibodies against canine distemper virus (CDV) and phocine distemper virus (PDV) in sera from dogs and various species of marine mammals. The test depends on the blocking of MAb binding to solid-phase antigen in the presence of positive serum. Test conditions were optimized by using control VNT-negative and -positive sera specific fo r CDV and PDV. A positive cutoff value of 30% inhibition, which represents the mean cutoff of a VNT-negative population (n = 623) plus 2 standard devi ations, was adopted for the test, A total of 736 serum samples were tested by the new cELISA and by the VNT as the "gold standard." An unexpected but useful finding was the ability of this CDV- and PDV-specific cELISA to also detect antibodies against the related pair dolphin morbillivirus and porpo ise morbillivirus. Based on a subpopulation of 625 sera used in statistical analyses, the overall sensitivity and specificity of cELISA relative to th ose of the VNT were 94.9 and 97.7%, respectively. Because the cELISA proved to be nearly as sensitive and specific as the VNT while being simpler and more rapid, it would be an adequate screening test for suspect CDV or PDV c ases and would also be useful for epidemiological surveillance of morbilliv iral infections in marine mammal populations.