Delaying the Expression of Herpes Simplex Virus Type 1 Glycoprotein B (gB) to a True Late Gene Alters Neurovirulence and Inhibits the gB-CD8 ⁺ T-Cell Response in the Trigeminal Ganglion

Abstract

Following herpes simplex virus type 1 (HSV-1) ocular infection of C57BL/6 mice, activated CD8؉ T cells specific for an immunodominant epitope on HSV-1 glycoprotein B (gB-CD8 cells) establish a stable memory population in HSV-1 latently infected trigeminal ganglia (TG), whereas non-HSV-specific CD8 ؉ T cells are lost over time. The retention and activation of gB-CD8 cells appear to be influenced by persistent viral antigenic exposure within the latently infected TG. We hypothesized that the low-level expression of gB from its native promoter before viral DNA synthesis is critical for the retention and activation of gB-CD8 cells in the TG during HSV-1 latency and for their ability to block HSV-1 reactivation from latency. To test this, we created a recombinant HSV-1 in which gB is expressed only after viral DNA synthesis from the true late gC promoter (gCp-gB). Despite minor growth differences compared to its rescuant in infected corneas, gCp-gB was significantly growth impaired in the TG and produced a reduced latent genome load. The gCp-gB-and rescuantinfected mice mounted similar gB-CD8 effector responses, but the size and activation phenotypes of the memory gB-CD8 cells were diminished in gCp-gB latently infected TG, suggesting that the stimulation of gB-CD8 cells requires gB expression before viral DNA synthesis. Surprisingly, late gB expression did not compromise the capacity of gB-CD8 cells to inhibit HSV-1 reactivation from latency in ex vivo TG cultures, suggesting that gB-CD8 cells can block HSV-1 reactivation at a very late stage in the viral life cycle. These data have implications for designing better immunogens for vaccines to prevent HSV-1 reactivation.Herpes simplex virus type 1 (HSV-1) is a ubiquitous human pathogen that is responsible for repeated corneal infections that can induce blinding keratitis. The murine model of ocular HSV-1 infection has elucidated the role of host immunity in the establishment and maintenance of viral latency in trigeminal ganglia (TG). HSV-1 infection of a scarified mouse cornea leads to a short-lived epithelial lesion caused by acute viral replication in and destruction of corneal epithelial cells. During replication in culture, viral genes are expressed in a tightly regulated temporal cascade characterized by the sequential expression of immediate-early (IE) (␣) genes and early (␤) genes before viral DNA synthesis. The late ␥ genes are maximally expressed after viral DNA replication and can be subdivided into ␥1 genes, which are expressed in small amounts before viral DNA replication, and ␥2 genes, which are absolutely dependent on DNA replication for expression (7). Confirmation of the expression kinetics of HSV-1 genes in vivo has proven to be difficult, as uniform infections cannot be established. Previous studies seeking to address viral replication kinetics in neurons have given rise to controversial conclusions (31). However, our group has previously demonstrated that during reactivation, the ␥1 gene promoter of glycoprotein B (gB) is active before the ␥2 gene...

A Lentiviral Vector-Based, Herpes Simplex Virus 1 (HSV-1) Glycoprotein B Vaccine Affords Cross-Protection against HSV-1 and HSV-2 Genital Infections

“…(ii) gB1 induces strong humoral and cell-mediated immune responses (17,35). (iii) It contains "protective" cytotoxic-T-lymphocyte (CTL) epitopes that are preferentially recognized by asymptomatic subjects, are important to prevent recurrent diseases, and maintain HSV-1 in a latent state (12,45). (iv) Finally, gB1 is highly conserved within and between HSV-1 and HSV-2 serotypes.…”

“…The strategies tested included genetically attenuated live virus, whole inactivated virion preparations, recombinant subunit vaccines, gene-delivery vehicles expressing structural or nonstructural HSV antigens, and DNA plasmid expressing HSV antigens (reviewed in references 17 and 38). Most of these approaches failed during animal study or in early phases of human trials, but a few have received the more consideration since they were able to reduce the rate of acquiring HSV-2 genital infection in HSV-seronegative women (45). These results offered hope that vaccination against HSV-2 is possible but also showed that improvement of current and development of novel concepts were clearly necessary (17).…”

Phosphorylation of a Herpes Simplex Virus 1 dUTPase by a Viral Protein Kinase, Us3, Dictates Viral Pathogenicity in the Central Nervous System but Not at the Periphery

“…The more striking feature in the present study was that the phosphorylation, as well as the enzymatic activity, of vdUTPase played no role in viral replication and pathogenicity in the eyes and vaginas of mice following ocular and vaginal inoculation, respectively. To our knowledge, HSV proteins or their domains critical for viral replication and virulence in the CNS of mice following intracranial inoculation are, in almost all cases, also involved in pathogenicity in peripheral sites, such as eyes and vaginas, following peripheral (ocular and vaginal) inoculation (7,10,11,15,27,41,(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59). Therefore, this phosphorylation reaction, which promoted the vdUTPase activity, is a unique indication of a specific mechanism involved in HSV-1 replication and virulence in and replication in mice.…”

γ-Herpesvirus Reactivation Differentially Stimulates Epitope-Specific CD8 T Cell Responses

“…The regulation of T cell responses during persistent infections may vary depending on several factors, including the quality of T cell priming, the anatomical sites of viral persistence, the inflammatory microenvironment, and the timing and duration of cognate antigen presentation (29-34). It is unclear how the antiviral T cell response is maintained long-term during persistent γ-herpesvirus infections.…”