RACCOON POXVIRUS FELINE PANLEUKOPENIA VIRUS VP2 RECOMBINANT PROTECTS CATS AGAINST FPV CHALLENGE

An infectious raccoon poxvirus (RCNV) was used to express the feline p anleukopenia virus (FPV) open reading frame VP2. The recombinant, RCNV /FPV, was constructed by homologous recombination with a chimeric plas mid for inserting the expression cassette into the thymidine kinase (T K) locus of RCNV. Expression of the VP2 DNA was regulated by the vacci nia virus late promoter P-11. Southern blot and polymerase chain react ion (PCR) analyses confirmed the cassette was in the TK gene of the RC NV genome. An immunofluorescent antibody assay using feline anti-FPV p olyclonal serum showed the expressed viral antigen in the cytoplasm of infected cells. Radioimmunoprecipitation with the same antiserum dete cted a 67-kDa VP2 protein which exactly matched the migration of the a uthentic FPV VP2 protein by SDS-polyacrylamide gel electrophoresis, Ni ne five-month-old cats were vaccinated and 21 days later were boosted with the recombinant virus. Peroral FPV challenge 2 weeks after the bo oster showed that the cats were fully protected as measured by examini ng clinical signs and total white blood cell counts in peripheral bloo d. Cats not immunized developed low to very low leukocyte counts follo wing peroral FPV challenge. The nine vaccinated cats showed high FPV n eutralization antibody prior to challenge, whereas nonvaccinated cats formed anti-FPV antibodies only after challenge. (C) 1996 Academic Pre ss, Inc.