Reticuloendotheliosis Virus Sequence Integrated Into The Fowlpox Virus Genomes Of Field Strain And Vaccine Strain

It has been reported that Reticuloendotheliosis Virus,retrovirus could integrate into the genome of fowlpox virus which has a large DNA genome. This event probably result in that commercial fowl poxvirus vaccines failed to confer complete protection against challenge with the field Strains.Seven field strains of fowlpox virus isolated from diverse outbreaks of fowlpox in Shandong and Henan province were screened for the presence of REV sequences potentially integrated into their genomes by PCR peimers specific to the long terminal repeat (LTR) region, env, gag, pol genes of REV genome, respectively. The results showed that each field isolate carried a nearly intact provirus in their genomes at the same site. In contrast, eight fowlpox vaccines retained only a 5'282-bp LTR fusion.The interference to antibody titres of ND vaccine immunization of two field isolates and one vaccine strain carrying intact or partial REV integration in their genome were also investigated, and slight differences were observed between treated groups and control, but there were not statistical differences between each group.The integration of a near-full-length and apparently infectious REV provirus into FPV may provide additional transmission routes for the retrovirus by the replication of FPV, in turn increase the pathogenicity of virulent FPV and reduce the efficacy of...