Human Asymptomatic Epitope Peptide/CXCL10-Based Prime/Pull Vaccine Induces Herpes Simplex Virus-Specific Gamma Interferon-Positive CD107 ⁺ CD8 ⁺ T Cells That Infiltrate the Corneas and Trigeminal Ganglia of Humanized HLA Transgenic Rabbits and Protect against Ocular Herpes Challenge

Abstract

Herpes simplex virus 1 (HSV-1) is a prevalent human pathogen that infects the cornea, causing potentially blinding herpetic disease. A clinical herpes vaccine is still lacking. In the present study, a novel prime/pull vaccine was tested in a human leukocyte antigen (HLA) transgenic rabbit model of ocular herpes (HLA Tg rabbits). Three peptide epitopes were selected, from the HSV-1 membrane glycoprotein C (UL44), the DNA replication binding helicase (UL9), and the tegument protein (UL25), all preferentially recognized by CD8 T cells from "naturally protected" HSV-1-seropositive healthy asymptomatic (ASYMP) individuals (who never had recurrent corneal herpetic disease). HLA Tg rabbits were immunized with a mixture of these three ASYMP CD8 T cell peptide epitopes (UL44, UL9, and UL25), which were delivered subcutaneously with CpG adjuvant (prime). Fifteen days later, half of the rabbits received a topical ocular treatment with a recombinant neurotropic adeno-associated virus type 8 (AAV8) vector expressing the T cell-attracting CXCL10 chemokine (pull). The frequency and function of HSV-specific CD8 T cells induced by the prime/pull vaccine were assessed in the peripheral blood, cornea, and trigeminal ganglion (TG). Compared to the cells generated in response to peptide immunization alone, the peptide/CXCL10 prime/pull vaccine generated frequent polyfunctional gamma interferon-positive (IFN-γ) CD107 CD8 T cells that infiltrated both the cornea and TG. CD8 T cell mobilization into the cornea and TG of prime/pull-vaccinated rabbits was associated with a significant reduction in corneal herpesvirus infection and disease following an ocular HSV-1 (strain McKrae) challenge. These findings draw attention to the novel prime/pull vaccine strategy for mobilizing antiviral CD8 T cells into tissues to protect against herpesvirus infection and disease. There is an urgent need for a vaccine against widespread herpes simplex virus infections. The present study demonstrates that immunization of HLA transgenic rabbits with a peptide/CXCL10 prime/pull vaccine triggered mobilization of HSV-specific CD8 T cells locally into the cornea and TG, the sites of acute and latent herpesvirus infections, respectively. Mobilization of antiviral CD8 T cells into the cornea and TG of rabbits that received the prime/pull vaccine was associated with protection against ocular herpesvirus infection and disease following an ocular HSV-1 challenge. These results highlight the importance of the prime/pull vaccine strategy to bolster the number and function of protective CD8 T cells within infected tissues.

Blockade of PD-1 and LAG-3 Immune Checkpoints Combined with Vaccination Restores the Function of Antiviral Tissue-Resident CD8+TRMCells and Reduces Ocular Herpes Simplex Infection and Disease in HLA Transgenic Rabbits

“…HLA transgenic and New Zealand wild-type rabbits. An HLA transgenic rabbit colony was bred at the University of California-Irvine (UC Irvine) (8,28,39,(59)(60)(61), and the New Zealand White (NZW) rabbits, purchased from Western Oregon Rabbit Co., were used for all the experiments. All rabbits were housed and treated in accordance with ARVO (Association for Research in Vision and Ophthalmology), AAALAC (Association for Assessment and Accreditation of Laboratory Animal Care), and NIH (National Institutes of Health) guidelines.…”

“…An immune surveillance role for corneaand TG-resident HSV-specific CD8 ϩ T cells has been established (11,16,25,(36)(37)(38). When rabbits are exposed to stress, there is an enhancement of HSV-1 reactivation that can cause the development of recurrent corneal disease (28,39,40). Tissue-resident CD4 ϩ and CD8 ϩ T RM cells appear to be involved in controlling virus reactivation from latently TG (28,39).…”

“…When rabbits are exposed to stress, there is an enhancement of HSV-1 reactivation that can cause the development of recurrent corneal disease (28,39,40). Tissue-resident CD4 ϩ and CD8 ϩ T RM cells appear to be involved in controlling virus reactivation from latently TG (28,39). To our knowledge, this is the first report in the HLA Tg rabbits that shows (i) LAG-3-related functional exhaustion of HSV-specific CD8 ϩ T cells in both the HLA Tg rabbits were bled on days 12 p.i., and the frequencies of epitope-specific CD8 ϩ T cells were determined using the corresponding HLA-A*02:01-peptides/tetramers.…”

Therapeutic Mucosal Vaccination of Herpes Simplex Virus 2-Infected Guinea Pigs with Ribonucleotide Reductase 2 (RR2) Protein Boosts Antiviral Neutralizing Antibodies and Local Tissue-Resident CD4 + and CD8 + T RM Cells Associated with Protection against Recurrent Genital Herpes

“…It is becoming increasingly clear that the acquired herpes immunity in SYMP individuals is not sufficient for protection against virus reactivation and virus replication and disease at the genital tract (18). This implies that a successful herpes vaccine must be able to either boost the natural immune responses or initiate a protective immune mechanism that does not occur following natural exposure to the virus (13,34,35). Such protective immune responses might be directed against different Ags than those by the immune system from SYMP individuals.…”

“…Currently, the medical opinion is that an effective antiviral therapeutic vaccine would constitute the best approach to protect from recurrent genital herpetic disease (2,4). It is becoming increasingly clear that the acquired immune responses that develop following first exposure to the virus are not sufficient for protection against recurrent genital herpes in symptomatic women (12)(13)(14). This implies that a successful therapeutic vaccine must be able to boost an immune response that is stronger and/or different than the acquired immunity induced by the virus itself (15).…”