Characterization and recombination mapping of an antigenic and host range mutation of canine parvovirus

A mutant of canine parvovirus (CPV) was derived after culture of a highly passaged isolate of CPV in the NLFK feline cell line. The virus (CPV-102/10) differed from the parental strain in its antigenic type when tested with a panel of neutralizing monoclonal antibodies, and in its relative ability to replicate in a dog cell line or in dogs. The mutant formed little replicative form DNA in the canine cells. Five single recombinants and two double recombinants between CPV-102/10 and a wild type CPV were constructed by digesting purified viral replicative form DNA with restriction enzymes, ligating the separated ends from the different strains, and examining the viruses isolated after transfecting the DNA into cell cultures. Analysis of the recombinant viruses showed that the mutation(s) determining both the antigenic and host range differences mapped between 64 and 73 map units in the genome, within the capsid protein gene. Sequencing the DNA from that region revealed differences of two adjacent amino acids, both resulting in nonconservative differences in the predicted amino acid sequences of the viruses. These results show that the ability of CPV to infect dogs or their cultured cells is determined, at least in part, by the conformation of the surface of the virus capsid.