| In order to give theoretic evidence to the phenomenon of REV genome integrated into FPV genome in China, we do research with 5 Poxvirus vaccines strains and 4 field strains.The methords including polymerase chain reaction,dot-blot and immunfluoscese analysis. IFA used as a methord to determine whether the FPV strains were contaminated with REV.Dot-blot was convenient and more suitable to large amount of samples.PCR was a more correct methord.Result indicated that the integration of REV into FPV has been common in FPV vaccines strains and field strains in China.With REV-LTR and REV-env were found in FPV,but without REV-pol and REV-gag.By use of genomic DNA prepare from 5 fowlpox virus (FPV) vaccines made in China (from Shandong,Beijing,Liaoning,Zhejing and Shanghai respectively)as the templates, reticuloendotheliosis virus (REV) LTR was amplified in PCR with a pair of primers synthesized according to the sequences flanking the integrated REV-5'LTR in FPV genomes published in US and Australian. Sequence analysis indicated that the REV-5'LTR integration sites in genomes of all 5 Chinese PFV vaccine products were identical to American and Australian FPV vaccines with integrated REV-5'LTR. Among the 5 FPV vaccine products made in China, 3 productes Vac-B-Ch,Vac-D-Ch and Vac-E-Ch had the integrated REV-5'LTR sequences of 223bp with 100% homology to that in American vaccine Vac-3-Am and Australian vaccine Vac-M3-Au. The integrated 505bp REV-LTR sequences in another Chinese products Vac-A-Ch and Vac-C-Ch had 99.6% homology to the integrated REV-LTR of American vaccine Vac-1-Am and Australian vaccine Vac-S-Au. However, REV-5'LTR integrated in all 5 FPV vaccines made in China gave only 75.4%~91.5% homology to LTR of a Chinese field strain HA9901. Based on the above results, it is reasonable to speculate that the virus stocks for the 5 Chinese FPV vaccine products were rather originally imported with their integrated REV LTR than recombinated with LTR of REV local field strains in China.
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