Immunological Characterization of the Feline Herpesvirus-1 Glycoprotein B and Analysis of Its Deduced Amino Acid Sequence

Abstract

Feline herpesvirus 1 (FHV-1) is an important viral pathogen of cats. Like other alphaherpesviruses, FHV-1 contains a HSV-1 glycoprotein B (gB) homolog. In this study, monospecific antisera to HSV-1 gB reacted with three FHV-1 proteins (100, 64, and 58 kDa) present in virion lysates by immunoprecipitation and immunoblot analyses. Reduced stringency hybridization experiments using a HSV-1 gB probe localized the FHV-1 gB gene to a 9.6-kb Sa/l fragment in the unique long region of the genome. Northern blot analyses further localized the entire coding region within a 3.3-kb Sacl fragment. The nucleotide sequence of this fragment was determined and two overlapping open reading frames (ORFs) encoding gB and ICP 18.5 were predicted. The amino acid sequence of the 2829 bp gB ORF was shown to have a high degree of homology with gB analogs of HSV-1, EHV-1, BHV-1, EHV-4, and especially PRV. Two unique characteristics of gB of FHV-1 were the unusually long signal sequence of 73 residues and two potential internal cleavage sites, RTRRS and RSRRS. An evolutionary tree based on gB homologs from 12 alphaherpesviruses suggests that feline herpesvirus-1 evolved along similar lines as the varicelloviruses, pseudorabies virus, bovine herpesvirus type 1, and equine herpesvirus types 1 and 4. The gB gene of FHV-1 was expressed in vaccinia virus (WR). This recombinant induced fairly high titers of virus neutralizing antibodies in rabbits. In Western blot analyses with potassium tartratepurified virions, a 60-kDa polypeptide reacted with the rabbit antisera.