A Single Intramuscular Vaccination of Mice with the HSV-1 VC2 Virus with Mutations in the Glycoprotein K and the Membrane Protein UL20 Confers Full Protection against Lethal Intravaginal Challenge with Virulent HSV-1 and HSV-2 Strains

Abstract

Herpes Simplex Virus type-1 (HSV-1) and type-2 (HSV-2) establish life-long infections and cause significant orofacial and genital infections in humans. HSV-1 is the leading cause of infectious blindness in the western world. Currently, there are no available vaccines to protect against herpes simplex infections. Recently, we showed that a single intramuscular immunization with an HSV-1(F) mutant virus lacking expression of the viral glycoprotein K (gK), which prevents the virus from entering into distal axons of ganglionic neurons, conferred significant protection against either virulent HSV-1(McKrae) or HSV-2(G) intravaginal challenge in mice. Specifically, 90% of the mice were protected against HSV-1(McKrae) challenge, while 70% of the mice were protected against HSV-2(G) challenge. We constructed the recombinant virus VC2 that contains specific mutations in gK and the membrane protein UL20 preventing virus entry into axonal compartments of neurons, while allowing efficient replication in cell culture, unlike the gK-null virus, which has a major defect in virus replication and spread. Intramuscular injection of mice with 107 VC2 plaque forming units did not cause any significant clinical disease in mice. A single intramuscular immunization with the VC2 virus protected 100% of mice against lethal intravaginal challenge with either HSV-1(McKrae) or HSV-2(G) viruses. Importantly, vaccination with VC2 produced robust cross protective humoral and cellular immunity that fully protected vaccinated mice against lethal disease. Quantitative PCR did not detect any viral DNA in ganglionic tissues of vaccinated mice, while unvaccinated mice contained high levels of viral DNA. The VC2 virus may serve as an efficient vaccine against both HSV-1 and HSV-2 infections, as well as a safe vector for the production of vaccines against other viral and bacterial pathogens.

Intramuscular Immunization of Mice with the Live-Attenuated Herpes Simplex Virus 1 Vaccine Strain VC2 Expressing Equine Herpesvirus 1 (EHV-1) Glycoprotein D Generates Anti-EHV-1 Immune Responses in Mice

“…It has previously been reported that the parental VC2 vaccine strain did not produce any significant clinical disease after intramuscular administration in mice (15). Similarly, there were no adverse clinical signs noted after intramuscular injection of either VC2 or VC2-EHV-1-gD in mice throughout the vaccination period (8 weeks).…”

“…The construction and characterization of HSV-1 VC2 have been described previously (15). The VC2 genome cloned into a bacterial artificial chromosome (BAC) plasmid was utilized for the construction of VC2-EHV-1-gD.…”

“…The HSV-1 VC2 strain has been shown to elicit robust humoral and cellular immune responses in mice, nonhuman primates, and guinea pigs and to confer protection against HSV-2 challenge in mice (15), nonhuman primates (45), and guinea pigs (B. A. Stanfield et al, unpublished data).…”

“…Herein, we report the construction and testing of an effective HSV-1-vectored vaccine designed to prevent EHV-1 infections. The HSV-1 VC2 strain contains gK with the deletion of amino acids 31 to 68 and the deletion of the amino-terminal 19 amino acids of UL20, which render the virus unable to enter into the distal axons of ganglionic neurons, while the virus replicates efficiently in epithelial and fibroblast cells and generates robust and protective immune responses in mice (15) and guinea pigs (B. A. Stanfield and K. G. Kousoulas, unpublished data).…”

Deletion of a Predicted β-Sheet Domain within the Amino Terminus of Herpes Simplex Virus Glycoprotein K Conserved among Alphaherpesviruses Prevents Virus Entry into Neuronal Axons

“…In support of this prediction, we have recently shown that the HSV-1 (VC2) vaccine strain containing the gK⌬31-68 mutation protected mice against lethal intravaginal challenge with either virulent HSV-1 or HSV-2 in mice (84). The funders had no role in study design, data collection and interpretation, or decision to submit the work for publication.…”