Feline rhinotracheitis virus: a feline Herpesvirus

Genetic rearrangements in the gC gene of the feline herpesvirus type 1

In the field isolate, 91-58, of feline herpesvirus type 1 (FHV-1), one of the major immunogenic proteins was found to have different molecular masses of 75 and 130 kDa from those in the other field isolates (Maeda et al., J Vet Med Sci 57, 147-150, 1995). Immunoblot analysis using monoclonal antibodies (MAbs) indicated that the protein is glycoprotein C (gC). The gC gene of 91-58 was amplified by polymerase chain reaction (PCR) and shown to have an inserted fragment of approximately 160 base pairs (bp). Restriction endonuclease analysis of the PCR product with various restriction enzymes was carried out, indicating that the insertion located within 262 bp between Eco RV and DraI sites. Nucleotide sequence analysis indicated that the inserted fragment was 156 bp encoding 52 amino acids and composed repeat sequences. Next, five recent isolates were also examined by immunoblot analysis using anti-FHV-1 cat serum or MAbs. The result showed that one isolate, 98-064, also had the gC with different molecular weights. PCR and nucleotide sequence analyses indicated that 98-064 had an inserted sequence of 78 bp at the corresponding region identified in the gC gene of 91-58, although the inserted sequence was different from that of 91-58. These results indicated that some of FHV-1 isolates had the genetic rearrangements in the gC gene and detection of such mutations would be useful for differentiation among FHV-1 field isolates.

Properties and functions of feline herpesvirus type 1 glycoproteins

Feline herpesvirus type 1 (FHV-1) is a causative agent of feline viral rhinotracheitis and belongs to the subfamily Alphaherpesvirinae of the family Herpesviridae. Since first isolated in 1958 by Crandell and Maurer, FHV-1 is distributed worldwide and is the most clinically significant agent for respiratory infections in cats. In this review, we describe the recent findings with properties and functions of FHV-1 glycoproteins, especially hemagglutinins.

The diversity and unity of Herpesviridae

The family herpesviridae contains over 100 viruses endogenous to humans and to a wide variety of eukaryotic organisms. Inclusion in the family is based on architecture of the virion. The viruses differ significantly with respect to base composition and sequence arrangements of their DNAs, but share many biologic properties including the ability to remain latent in their hosts. On the basis of their biologic properties the herpesviruses have been classified into three subfamilies, i.e. alphaherpesvirinae, betaherpesvirinae and gammaherpesvirinae. The members of each subfamily share many properties including greater conservation and colinear arrangements of their genes. As a rule, more than one herpesvirus has been isolated from animals of economic importance and both humans have yielded viruses belong to all three subfamilies of the herpesviridae.

Biochemical study of the Feline Herpesvirus 1. Identification of glycoproteins by affinity

Feline Viral Rhinotracheitis herpesvirus (Feline Herpesvirus 1; FHV-1) was purified by rate zonal isopycnic centrifugation. Viral nucleocapsids were isolated from the nuclei and purified. Analysis of the purified and radiolabelled viral polypeptides and glycoproteins by gradient SDS polyacrylamide gel electrophoresis revealed that 23 viral proteins and 6 glycoproteins were present in the whole virus particle. Tween 80-diethylether treatment removed the major glycoproteins. FHV-1 viral glycoproteins were detected using [14C] glucosamine and a lectin binding procedure. The fluorescein isothiocyanate-Concanavalin A (FITC-Con A) specificity was checked by trials on other viruses whose glycoproteins had already been described. The FITC-Con A allows a very simplified procedure for glycoprotein determination after slab acrylamide gel electrophoresis and can be used prior to Coomassie blue staining of proteins.

Lesions produced by feline picornaviruses of different virulence in pathogen-free cats

Sixteen pathogen-free cats were exposed by aerosol to either of two feline picornavirus isolates. The isolates used were picornavirus-255 and kidney-cell-degenerating virus. These viruses were selected to represent picornavirus prototypes of high and low virulence, respectively. Picornavirus-255 consistently produced depression, anorexia, and pneumonia. There were no lesions in the upper respiratory tract or conjunctiva, nor were there clinical signs of upper respiratory disease. The pulmonary lesions began as multifocal exudative pneumonia that progressed rapidly to interstitial pneumonia characterized by marked adenomatoid proliferation of pneumocytes. Three weeks after exposure the pulmonary lesions were principally resolved. It also produced discrete lingual and palatine ulcers that were easily detected. Experimental infection with kidney-cell-degenerating virus resulted only in transient fever and tiny vesicles and ulcerations of the lingual and tonsillar mucosae that could easily escape detection. No significant respiratory lesions were induced by kidney cell degenerating virus.

Characteristics of a virus isolated from a feline fibrosarcoma

A virus was isolated from a radioresistant feline fibrosarcoma. It induced multi-nucleated giant-cell formation and lysis in a cell line derived from a canine fibro-sarcoma, which was used to characterize the virus. End-point titrations in these cells required 28 days. The virus was sensitive to ether and heat and was destroyed at pH 3. Replication was not inhibited by 5-bromodeoxyuridine. Electron microscopy revealed assembly by a budding process from the plasma membrane of infected cells. The average diameter of the virion was 106 nm. Intracisternal particles with an average diameter of 45 nm were present within infected cells. In two instances secondary monolayers of feline renal cells underwent morphological transformation after inoculation of the virus. The two strains of transformed cells are now in continuous culture and do not yield infectious virus.

Feline herpesvirus infection in fused cultures of naturally resistant human cells

Feline herpesvirus (FHV) attaches to, but does not penetrate, naturally resistant human embryonic lung cells. When the cells with attached virus are subsequently fused with inactivated Sendai virus, FHV causes characteristic cytopathic effects, but no infectious virus can be recovered from the infected cells.