Canine parvovirus (CPV) vaccination: Comparison of neutralizing antibody responses in pups after inoculation with CPV2 or CPV2b modified live virus vaccine

Canine parvovirus type 2 (CPV2) emerged in 1978 as causative agent of a new disease of dogs. New antigenic variants (biotypes), designated CPV2a and C PV2b, became widespread during 1979 to 1980 and 1984, respectively. At the present time the original CPV2 has disappeared in the dog population and ha s been replaced by the two new viruses, In the present study the comparison of neutralizing antibody titers in two groups of pups (18 pups in each gro up) inoculated with CPV2 and CPV2b modified live virus vaccines is reported . Using the hemagglutination inhibition (HI) test, relevant differences bet ween antibody titers, against either the homologous or the heterologous vir us, were not constantly observed, Using the neutralization (Nt) test, howev er, the pups inoculated with CPV2 had antibody titers which were approximat ely 30 times higher to the homologous virus (mean, 4,732) than to the heter ologous virus (CPV2b) (mean, 162), The results of these experiments support two conclusions: (i) the HI test may not always accurately evaluate the tr ue immune status of dogs with respect to CPV, and (ii) dogs inoculated with CPV2 vaccine develop relatively low Nt antibody titers against the heterol ogous virus (CPV2b), These data may suggest an advantage for new vaccines, considering that most presently licensed vaccines are produced with CPV2, w hich no longer exists in the dog population.