Restriction endonuclease analysis of field isolates of feline herpesvirus type 1 and identification of heterogeneous regions.

The genomic heterogeneity of 78 isolates of feline herpesvirus type 1 (FHV-1) recently isolated from cats suspected to have feline viral rhinotracheitis was analyzed by examining the digestion patterns found with restriction endonuclease MluI. The FHV-1 field isolates were classified into at least three genotypes, namely, the C7301, F2 (an attenuated vaccine strain), and C7805 types. The C7301 type seems to be a major type, since 64 of the 78 isolates belonged to this type. Eight and six isolates belonged to the F2 and C7805 types, respectively. Compared with the C7301 type, the heterogeneous region of the F2 type was localized to a 4.3-kbp EcoRI fragment within the US segment and the heterogeneous region of the C7805 type was localized to a 5.5-kbp XbaI fragment within the UL segment. Northern (RNA) blot analysis revealed no differences in the products transcribed from these regions. In addition, nucleotide sequence analysis showed that the MluI sites not found in the F2 and C7805 types were located in the regions homologous to the herpes simplex virus type 1 gI and UL5 genes, respectively.