DIFFERENTIATION OF VACCINE VIRUS FROM FIELD ISOLATES OF FELINE PANLEUKOPENIA VIRUS BY POLYMERASE CHAIN-REACTION AND RESTRICTION-FRAGMENT-LENGTH-POLYMORPHISM ANALYSIS

In an attempt to distinguish feline panleukopenia virus (FPLV) live va ccine strains from FPLV field isolates in Japan, we compared restricti on fragment length polymorphisms (RFLP) of polymerase chain reaction ( PCR)-amplified fragments of live FPLV vaccine strains with those of FP LV Japanese field isolates. On the basis of nucleotide sequence differ ences between PLI-IV, a live vaccine strain, and FPV-483, a recent fie ld isolate, two restriction enzymes, Dra I and Afa I, were selected fo r PCR-RFLP analysis of nucleotide (nt) differences at nt 3695 and 4508 , respectively. Three live vaccine strains including the PLI-IV strain could be distinguished from the Japanese field isolates by their PCR- RFLP patterns by Afa I, but one live vaccine strain was indistinguisha ble from the Japanese isolates when Dra I and Afa I were used, The jap anese field isolates were divided into two groups by the profile of PC R-RFLP patterns generated by Dra I and Afa I, suggesting that PCR-RFLP analysis using several enzymes provides a good genetic estimate of st rain differentiation. No isolate that shows a Dia I-negative/Afa I-neg ative pattern has emerged in Japan, indicating the possibility that th e live vaccine viruses with a Dra I-negative/Afa I-negative pattern, s uch as the PLI-IV strain, are candidates for use as live FPLV vaccine strain in Japan where they can be genetically distinguished from field strains.