Detection of IgM antibodies against a recombinant nucleocapsid protein of canine distemper virus in dog sera using a dot-blot assay

A dot-blot assay for the detection of IgM antibodies (ABs) against canine d istemper virus (CDV) in canine serum is described. The diagnostic potential of this technique was evaluated by analysing sera from three test groups: (i) specific pathogen-free (SPF) beagle dogs experimentally infected with V irulent CDV; (ii) SPF dogs immunized with a combined Vaccine containing CDV , and (iii) SPF dogs immunized with a CDV-free vaccine. As antigen for the dot-blot assay we used the recombinant nucleocapsid protein (N protein) of the Virulent A75/17 CDV strain. All 12 dogs of group i, infected with virul ent CDV, showed detectable CDV-specific IgM levels in their serum. AU dogs of group 2 were also positive for anti-CDV IgM after the first immunization with the CDV-containing vaccine. The four dogs immunized with a CDV-free V accine (group iii) remained negative throughout the course of the experimen t. From these results, we conclude that the IgM detection test, which requi res only a single serum sample, is a useful method for diagnosing current o r recent CDV infection in CDV-infected or CDV-immunized dogs under experime ntal conditions.