The molecular biology of swinepox virus. II. The infectious cycle.

Studies based on low-stringency hybridizations of radiolabeled swinepox virus (SPV) DNA to Southern blots containing DNA of representative members of the Orthopoxvirus, Leporipoxvirus, and Avipoxvirus genera and the Entomopoxvirus subfamily have revealed no DNA homology at this level of resolution. Antigenic relatedness between SPV and vaccinia was also analyzed using immunoprecipitations and revealed little if any cross-reactivity. The growth characteristics of SPV in tissue culture were examined by light microscopy and revealed both a delayed and a different cytopathology than that of vaccinia virus. SPV causes foci in pig kidney cells that are not evident until at least 4 days postinfection, whereas vaccinia rapidly generates plaques on these cells. The kinetics of DNA accumulation, protein expression, and RNA transcription of SPV have been examined and indicate that each of these facets of the SPV growth cycle is also considerably delayed when compared to vaccinia virus. Our data indicate that swinepox virus is unique from other poxviruses characterized to date and supports the classification of swinepox virus into a separate genus, Suipoxvirus, within the poxvirus family.