The Truncated Form of Glycoprotein gp2 of Equine Herpesvirus 1 (EHV-1) Vaccine Strain KyA Is Not Functionally Equivalent to Full-Length gp2 Encoded by EHV-1 Wild-Type Strain RacL11

Abstract

Equine herpesvirus 1 (EHV-1), a member of Varicellovirus genus in the Alphaherpesvirinae subfamily, is one of the most prevalent viruses affecting equine populations worldwide. Infection with EHV-1 may result in rhinopneumonitis, abortion, and often fatal encephalomyelitis. The continuing threat imposed by EHV-1 results in ongoing efforts aiming at a better understanding of EHV-1 pathogenesis and at developing safe and effective vaccines (27). Herpesviral glycoproteins are involved in different stages of virus infection and are major targets of the host's immune response. Envelope glycoproteins of EHV-1 are designated gB, gC, gD, gE, gG, gH, gI, gK, gL, and gM according their homologues in herpes simplex virus type 1 (HSV-1) (reviewed in reference 28). Compared to HSV-1 and other Alphaherpesvirinae, however, EHV-1 encodes two additional glycoproteins. One of the glycoproteins unique to EHV-1 was originally designated gp2 or gp300 (2, 45) and is expressed from gene 71 (EUS4) (38,42). Homologues of gp2 are found in EHV-1, EHV-4, and asinine herpesvirus 3 (8) and are among the mostabundant and -immunogenic glycoproteins in EHV-1 and EHV-4 virions (1, 7). EHV-1 gp2 is rich in serine and threonine residues and is a heavily O-glycosylated protein with a molecular mass in the range of 192 to Ͼ400 kDa (38,39,45). In contrast to EHV-4 gp2, the EHV-1 glycoprotein was shown to be partially cleaved into two polypeptides in infected cells (19). Endoproteolytic cleavage occurs after each of two adjacent arginine (R) residues at positions 506 and 507 in the sequence HRGRAGGR 506 R 507 G, and results in a 42-kDa carboxy-terminal subunit, which contains the transmembrane anchor, and an N-terminal serine/threonine-rich component that is highly O-glycosylated (19, 43). In the absence of gp2, EHV-1 strains were shown to be impaired in virus egress, while secondary envelopment appears to occur with unaltered kinetics and efficiency (31,32,37). It was also reported that deletion of gene 71 in EHV-1 strain Ab4 resulted in attenuation, and the generated virus mutant used as an experimental vaccine conferred protection against pulmonary disease in mice after challenge with wild-type virus (21).A number of EHV-1 strains with different biological properties have been described. While the RacL11 strain was isolated in the late 1950s from an aborted foal and exhibits high virulence in the natural host and laboratory animals, strain KyA, a candidate vaccine strain, is completely apathogenic for both mice and horses after serial passage in mouse L-M cells (6,25,26). As a result of a long history of passages in nonhomologous cells, KyA exhibits several genomic alterations,

In Vitro and In Vivo Relevance of Infectious Laryngotracheitis Virus gJ Proteins That Are Expressed from Spliced and Nonspliced mRNAs

“…EHV-1 mutants which completely lacked gp2 or expressed a truncated form of this protein were apathogenic in a mouse model (30,54). We show that gJ of ILTV is also a virulence factor, since a gJ-negative mutant was strongly attenuated in chickens, the natural host of ILTV.…”

Identification and Characterization of Equine Herpesvirus Type 1 pUL56 and Its Role in Virus-Induced Downregulation of Major Histocompatibility Complex Class I

“…In addition, the expression of gp2 was restored in the Ab4 parental virus (vAb4), Ab4G⌬1 (vAb4⌬1), Ab4G⌬1_TM (vAb4⌬1_TM) mutants, and the parental RacL11 virus (vRacL11) by cotransfection of RK13 cells with BAC DNA and plasmid DNA containing full-length gene 71, followed by plaque purification (31). Restoration of gp2 was confirmed by Western blot analysis of virusinfected cells using the anti-EHV-1 gp2 MAb 8B6, exactly as previously described (43,45).…”

“…Mouse anti-MHC-I monoclonal antibody (MAb) H58A (isotype IgG2a) and anti-CD44 MAb BAT31A (isotype IgG1) were purchased from VMRD and used at a 1/100 dilution. Rabbit anti-EHV-1 UL49.5 polyclonal antibodies (pAbs), mouse anti-EHV-1 gM MAb F6, and mouse anti-EHV-1 gp2 and biotinylated equine polyclonal anti-EHV-1 antibodies have been previously described (32,42,45). Rabbit anti-EHV-1 pUL56 pAbs (1/500) were designed and produced by GenScript Corporation (NJ).…”

Herpesvirus Chemokine-Binding Glycoprotein G (gG) Efficiently Inhibits Neutrophil Chemotaxis In Vitro and In Vivo

“…Animal Welfare Act, under the supervision of the Cornell Institutional Animal Care and Use Committee, and were conducted as described previously with some modifications (21). Briefly, 4-wk-old female BALB/c mice (16 mice per group) were infected with vL11⌬gG or vL11⌬gGR by the intranasal route at 4 ϫ 10 4 PFU/mouse.…”