Evidence from C57BL/6 mice suggests that CD8+ T cells, specific to the immunodominant HSV-1 glycoprotein B (gB) H-2b–restricted epitope (gB498–505), protect against ocular herpes infection and disease. However, the possible role of CD8+ T cells, specific to HLA-restricted gB epitopes, in protective immunity seen in HSV-1–seropositive asymptomatic (ASYMP) healthy individuals (who have never had clinical herpes) remains to be determined. In this study, we used multiple prediction algorithms to identify 10 potential HLA-A*02:01–restricted CD8+ T cell epitopes from the HSV-1 gB amino acid sequence. Six of these epitopes exhibited high-affinity binding to HLA-A*02:01 molecules. In 10 sequentially studied HLA-A*02:01–positive, HSV-1–seropositive ASYMP individuals, the most frequent, robust, and polyfunctional CD8+ T cell responses, as assessed by a combination of tetramer, IFN-γ-ELISPOT, CFSE proliferation, CD107a/b cytotoxic degranulation, and multiplex cytokine assays, were directed mainly against epitopes gB342–350 and gB561–569. In contrast, in 10 HLA-A*02:01–positive, HSV-1–seropositive symptomatic (SYMP) individuals (with a history of numerous episodes of recurrent clinical herpes disease) frequent, but less robust, CD8+ T cell responses were directed mainly against nonoverlapping epitopes (gB183–191 and gB441–449). ASYMP individuals had a significantly higher proportion of HSV-gB–specific CD8+ T cells expressing CD107a/b degranulation marker and producing effector cytokines IL-2, IFN-γ, and TNF-α than did SYMP individuals. Moreover, immunization of a novel herpes-susceptible HLA-A*02:01 transgenic mouse model with ASYMP epitopes, but not with SYMP epitopes, induced strong CD8+ T cell–dependent protective immunity against ocular herpes infection and disease. These findings should guide the development of a safe and effective T cell–based herpes vaccine.

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The best hope of controlling the herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) pandemic is the development of an effective vaccine. However, in spite of several clinical trials, starting as early as 1920s, no vaccine has been proven sufficiently safe and efficient to warrant commercial development. In recent years, great strides in cellular and molecular immunology have stimulated creative efforts in controlling herpes infection and disease. However, before moving towards new vaccine strategy, it is necessary to answer two fundamental questions: (i) why past herpes vaccines have failed? (ii) Why the majority of HSV seropositive individuals (i.e., asymptomatic individuals) are naturally “protected” exhibiting few or no recurrent clinical disease, while other HSV seropositive individuals (i.e., symptomatic individuals) have frequent ocular, orofacial, and/or genital herpes clinical episodes? We recently discovered several discrete sets of HSV-1 symptomatic and asymptomatic epitopes recognized by CD4+and CD8+T cells from seropositive symptomatic versus asymptomatic individuals. These asymptomatic epitopes will provide a solid foundation for the development of novel herpes epitope-based vaccine strategy. Here we provide a brief overview of past clinical vaccine trials, outline current progress towards developing a new generation “asymptomatic” clinical herpes vaccines, and discuss future mucosal “asymptomatic” prime-boost vaccines that could optimize local protective immunity.

Mounting evidence suggests that neonatal tissue damage evokes alterations in spinal pain reflexes which persist into adulthood. However, less is known about potential concomitant effects on the transmission of nociceptive information to the brain, as the degree to which early injury modulates synaptic integration and membrane excitability in mature spinal projection neurons remains unclear. Here we demonstrate that neonatal surgical injury leads to a significant shift in the balance between synaptic excitation and inhibition onto identified lamina I projection neurons of the adult mouse spinal cord. The strength of direct primary afferent input to mature spinoparabrachial neurons was enhanced following neonatal tissue damage, whereas the efficacy of both GABAergic and glycinergic inhibition onto the same population was compromised. This was accompanied by reorganization in the pattern of sensory input to adult projection neurons, which included a greater prevalence of monosynaptic input from low-threshold A-fibers when preceded by early tissue damage. In addition, neonatal incision resulted in greater primary afferent-evoked action potential discharge in mature projection neurons.Overall, these results demonstrate that tissue damage during early life causes a long-term increase in the gain of spinal nociceptive circuits, and suggest that the prolonged consequences of neonatal trauma may not be restricted to the spinal cord but rather include excessive ascending signaling to supraspinal pain centers.

Herpes simplex virus type 1 (HSV-1) is a prevalent human pathogen that infects over 3.72 billion individuals worldwide and can cause potentially blinding recurrent corneal herpetic disease. HSV-1 establishes latency within sensory neurons of trigeminal ganglia (TG) and TG-resident CD8+ T cells play a critical role in preventing its reactivation. The repertoire, phenotype and function of protective CD8+ T cells are unknown. Bolstering the apparent feeble numbers of CD8+ T cells in TG remains a challenge for immunotherapeutic strategies. In this study, a comprehensive panel of 467 HLA-A*0201-restricted CD8+ T cell epitopes were predicted from the entire HSV-1 genome. CD8+ T cell responses to these genome-wide epitopes were compared in HSV-1 seropositive symptomatic (SYMP) individuals (with a history of numerous episodes of recurrent herpetic disease) vs. asymptomatic (ASYMP) individuals (who are infected but never experienced any recurrent herpetic disease). Frequent polyfunctional HSV-specific effector memory IFN-γ+CD107a/b+CD44highCD62LlowCD8+ TEM cells were detected in ASYMP individuals and were mainly directed against three “ASYMP” epitopes. In contrast, SYMP individuals have more mono-functional central memory CD44highCD62LhighCD8+ TCM cells. Furthermore, therapeutic immunization with an innovative prime/pull vaccine, based on priming with multiple “ASYMP” epitopes (prime) and neurotropic TG delivery of the T-cell attracting chemokine CXCL-10 (pull), boosted the number and function of CD44highCD62LlowCD8+ TEM and tissue-resident CD103highCD8+ TRM cells in TG of latently infected HLA-A*0201 Tg mice and reduced recurrent ocular herpes following UV-B induced reactivation. These findings have profound implications in the development of T-cell-based immunotherapeutic strategies to treat blinding recurrent herpes infection and disease.

Pacemaker neurons with an intrinsic ability to generate rhythmic burst-firing have been characterized in lamina I of the neonatal spinal cord, where they are innervated by high-threshold sensory afferents. However, little is known about the output of these pacemakers, as the neuronal populations which are targeted by pacemaker axons have yet to be identified. The present study combines patch clamp recordings in the intact neonatal rat spinal cord with tract-tracing to demonstrate that lamina I pacemaker neurons contact multiple spinal motor pathways during early life. Retrograde labeling of premotor interneurons with the trans-synaptic virus PRV-152 revealed the presence of burst-firing in PRV-infected lamina I neurons, thereby confirming that pacemakers are synaptically coupled to motor networks in the spinal ventral horn. Notably, two classes of pacemakers could be distinguished in lamina I based on cell size and the pattern of their axonal projections. While small pacemaker neurons possessed ramified axons which contacted ipsilateral motor circuits, large pacemaker neurons had unbranched axons which crossed the midline and ascended rostrally in the contralateral white matter. Recordings from identified spino-parabrachial and spino-PAG neurons indicated the presence of pacemaker activity within neonatal lamina I projection neurons. Overall, these results show that lamina I pacemakers are positioned to regulate both the level of activity in developing motor circuits as well as the ascending flow of nociceptive information to the brain, thus highlighting a potential role for pacemaker activity in the maturation of pain and sensorimotor networks in the CNS.

Following ocular herpes simplex virus type 1 infection, HSV-specific CD8+ T cells are induced, selectively retained in latently infected trigeminal ganglia and appear to decrease HSV-1 reactivation. The LAT gene increases HSV-1 reactivation. We hypothesized that increased numbers and/or function of HSV-specific functional CD8+ T-cells in TG might be involved in the decreased reactivation seen with LAT(-)mutants. Mice were ocularly infected with either LAT(+) or LAT(-) viruses and the number and function of CD8+ T-cells in TG were examined during latency. Although fewer total CD8+ T-cells were found with LAT(-) viruses, TG had more functional HSV-gB-specific CD8+ T cells compared to LAT(+) TG which had many exhausted HSV-gB-specific CD8+ T cells, as judged by high levels of PD-1, impaired cytotoxicity, and decreased IFN-γ and TNF-α production. In addition, mouse Neuro2A cells expressing LAT, had elevated PD-L1 and MHC-I compared to LAT(-) Neuro2A cells and were resistant to lysis by allogeneic CD8+ T cells. Collectively, our findings suggest that TG from mice latently infected with LAT(-) viruses had more HSV-specific functional CD8+ T-cells than did TG from mice infected with LAT(+) viruses. In addition LAT appeared specifically able to upregulate both PD-L1 and MHC-I. These findings may constitute a novel immune evasion mechanism whereby LAT promotes dysfunctional HSV-specific CD8+ T cells in latently infected TG, resulting in more virus reactivation