Feline herpesvirus type 1 (FHV-1) is a causative agent of feline viral rhinotracheitis and belongs to the subfamily Alphaherpesvirinae of the family Herpesviridae. The positive rate of FHV and FCV in domestic cats were 44% and 74%, respectively. Ion-exchange and gel-exclusion chromatographies were also capable of purifying the detergent-soluble crude hemagglutinin. There was no correlation between virus infectivity titers and the HA titers at various harvesting times, and besides, hemagglutinins were found in intracellular samples at the early stage of infection. The predicted precursor polypeptide derived from this open reading frame could have a calculated Mr of 106 kDa in unglycosylated form and contains ten potential N-linked glycosylation sites and a probable internal proteolytic cleavage site. Sequence analysis and comparison of the putative polypeptide encoded by US8.5 revealed that this ORF was unique to FHV-1. The optimal concentrations of each detergent for solubilizing hemagglutinin were 0.05 (v/v)%, 0.5 (w/v)%, and 0.1-0.2 (w/v)%, respectively.
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. Therefore, either hemagglutinin could be used as HA antigen for the hemagglutination-inhibition test.