Persistence of mucosal T-cell responses to herpes simplex virus type 2 in the female genital tract

Interferon inhibits the release of herpes simplex virus-1 from the axons of sensory neurons

IMPORTANCE

Herpes simplex virus-1 (HSV-1) is a human pathogen known to cause cold sores and genital herpes. HSV-1 establishes lifelong infections in our sensory neurons, with no cure or vaccine available. HSV-1 can reactivate sporadically and travel back along sensory nerves, where it can form lesions in the oral and genital mucosa, eye, and skin, or be shed asymptomatically. New treatment options are needed as resistance is emerging to current antiviral therapies. Here, we show that interferons (IFNs) are capable of blocking virus release from nerve endings, potentially stopping HSV-1 transmission into the skin. Furthermore, we show that IFNγ has the potential to have widespread antiviral effects in the neuron and may have additional effects on HSV-1 reactivation. Together, this study identifies new targets for the development of immunotherapies to stop the spread of HSV-1 from the nerves into the skin.

Boosting of vaginal HSV-2-specific B and T cell responses by intravaginal therapeutic immunization results in diminished recurrent HSV-2 disease

Boosting herpes simplex virus (HSV)-specific immunity in the genital tissues of HSV-positive individuals to increase control of HSV-2 recurrent disease and virus shedding is an important goal of therapeutic immunization and would impact HSV-2 transmission. Experimental therapeutic HSV-2 vaccines delivered by a parenteral route have resulted in decreased recurrent disease in experimental animals. We used a guinea pig model of HSV-2 infection to test if HSV-specific antibody and cell-mediated responses in the vaginal mucosa would be more effectively increased by intravaginal (Ivag) therapeutic immunization compared to parenteral immunization. Therapeutic immunization with HSV glycoproteins and CpG adjuvant increased glycoprotein-specific IgG titers in vaginal secretions and serum to comparable levels in Ivag- and intramuscular (IM)-immunized animals. However, the mean numbers of HSV glycoprotein-specific antibody secreting cells (ASCs) and IFN-γ SCs were greater in Ivag-immunized animals demonstrating superior boosting of immunity in the vaginal mucosa compared to parenteral immunization. Therapeutic Ivag immunization also resulted in a significant decrease in the cumulative mean lesion days compared to IM immunization. There was no difference in the incidence or magnitude of HSV-2 shedding in either therapeutic immunization group compared to control-treated animals. Collectively, these data demonstrated that Ivag therapeutic immunization was superior compared to parenteral immunization to boost HSV-2 antigen-specific ASC and IFN-γ SC responses in the vagina and control recurrent HSV-2 disease. These results suggest that novel antigen delivery methods providing controlled release of optimized antigen/adjuvant combinations in the vaginal mucosa would be an effective approach for therapeutic HSV vaccines. IMPORTANCE HSV-2 replicates in skin cells before it infects sensory nerve cells where it establishes a lifelong but mostly silent infection. HSV-2 occasionally reactivates, producing new virus which is released back at the skin surface and may be transmitted to new individuals. Some HSV-specific immune cells reside at the skin site of the HSV-2 infection that can quickly activate and clear new virus. Immunizing people already infected with HSV-2 to boost their skin-resident immune cells and rapidly control the new HSV-2 infection is logical, but we do not know the best way to administer the vaccine to achieve this goal. In this study, a therapeutic vaccine given intravaginally resulted in significantly better protection against HSV-2 disease than immunization with the same vaccine by a conventional route. Immunization by the intravaginal route resulted in greater stimulation of vaginal-resident, virus-specific cells that produced antibody and produced immune molecules to rapidly clear virus.

Immunomodulatory Role of Interferons in Viral and Bacterial Infections

Interferons are a group of immunomodulatory substances produced by the human immune system in response to the presence of pathogens, especially during viral and bacterial infections. Their remarkably diverse mechanisms of action help the immune system fight infections by activating hundreds of genes involved in signal transduction pathways. In this review, we focus on discussing the interplay between the IFN system and seven medically important and challenging viruses (herpes simplex virus (HSV), influenza, hepatitis C virus (HCV), lymphocytic choriomeningitis virus (LCMV), human immunodeficiency virus (HIV), Epstein-Barr virus (EBV), and SARS-CoV coronavirus) to highlight the diversity of viral strategies. In addition, the available data also suggest that IFNs play an important role in the course of bacterial infections. Research is currently underway to identify and elucidate the exact role of specific genes and effector pathways in generating the antimicrobial response mediated by IFNs. Despite the numerous studies on the role of interferons in antimicrobial responses, many interdisciplinary studies are still needed to understand and optimize their use in personalized therapeutics.

Novel Adjuvant S-540956 Targets Lymph Nodes and Reduces Genital Recurrences and Vaginal Shedding of HSV-2 DNA When Administered with HSV-2 Glycoprotein D as a Therapeutic Vaccine in Guinea Pigs

Herpes simplex virus type 2 (HSV-2) is a leading cause of genital ulcer disease and a major risk factor for acquisition and transmission of HIV. Frequent recurrent genital lesions and concerns about transmitting infection to intimate partners affect the quality of life of infected individuals. Therapeutic vaccines are urgently needed to reduce the frequency of genital lesions and transmission. S-540956 is a novel vaccine adjuvant that contains CpG oligonucleotide ODN2006 annealed to its complementary sequence and conjugated to a lipid that targets the adjuvant to lymph nodes. Our primary goal was to compare S-540956 administered with HSV-2 glycoprotein D (gD2) with no treatment in a guinea pig model of recurrent genital herpes (studies 1 and 2). Our secondary goals were to compare S-540956 with oligonucleotide ODN2006 (study1) or glucopyranosyl lipid A in a stable oil-in-water nano-emulsion (GLA-SE) (study 2). gD2/S-540956 reduced the number of days with recurrent genital lesions by 56%, vaginal shedding of HSV-2 DNA by 49%, and both combined by 54% compared to PBS, and was more efficacious than the two other adjuvants. Our results indicate that S-540956 has great potential as an adjuvant for a therapeutic vaccine for genital herpes, and merits further evaluation with the addition of potent T cell immunogens.

HSV-2-Specific Human Female Reproductive Tract Tissue Resident Memory T Cells Recognize Diverse HSV Antigens

Antigen-specific T_RM persist and protect against skin or female reproductive tract (FRT) HSV infection. As the pathogenesis of HSV differs between humans and model organisms, we focus on humans with well-characterized recurrent genital HSV-2 infection. Human CD8+ T_RM persisting at sites of healed human HSV-2 lesions have an activated phenotype but it is unclear if T_RM can be cultivated in vitro. We recovered HSV-specific T_RM from genital skin and ectocervix biopsies, obtained after recovery from recurrent genital HSV-2, using ex vivo activation by viral antigen. Up to several percent of local T cells were HSV-reactive ex vivo. CD4 and CD8 T cell lines were up to 50% HSV-2-specific after sorting-based enrichment. CD8 T_RM displayed HLA-restricted reactivity to specific HSV-2 peptides with high functional avidities. Reactivity to defined peptides persisted locally over several month and was quite subject-specific. CD4 T_RM derived from biopsies, and from an extended set of cervical cytobrush specimens, also recognized diverse HSV-2 antigens and peptides. Overall we found that HSV-2-specific T_RM are abundant in the FRT between episodes of recurrent genital herpes and maintain competency for expansion. Mucosal sites are accessible for clinical monitoring during immune interventions such as therapeutic vaccination.

Tissue-resident memory T cells in the urogenital tract

Our understanding of T cell memory responses changed drastically with the discovery that specialized T cell memory populations reside within peripheral tissues at key pathogen entry sites. These tissue-resident memory T (T_RM) cells can respond promptly to an infection without the need for migration, proliferation or differentiation. This rapid and local deployment of effector functions maximizes the ability of T_RM cells to eliminate pathogens. T_RM cells do not circulate through peripheral tissues but instead form isolated populations in the skin, gut, liver, kidneys, the reproductive tract and other organs. This long-term retention in the periphery might allow T_RM cells to fully adapt to the local conditions of their environment and mount customized responses to counter infection and tumour growth in a tissue-specific manner. In the urogenital tract, T_RM cells must adapt to a unique microenvironment to confer protection against potential threats, including cancer and infection, while preventing the onset of auto-inflammatory disease. In this Review, we discuss insights into the diversification of T_RM cells from other memory T cell lineages, the adaptations of T_RM cells to their local environment, and their enhanced capacity to counter infection and tumour growth compared with other memory T cell populations, especially in the urogenital tract.

Human mucosal tissue-resident memory T cells in health and disease

Memory T cells are fundamental to maintain immune surveillance of the human body. During the past decade, it has become apparent that non-recirculating resident memory T cells (TRMs) form a first line memory response in tissues to tackle re-infections. The fact that TRMs are essential for local immunity highlights the therapeutic potential of targeting this population against tumors and infections. However, similar to other immune subsets, TRMs are heterogenous and may form distinct effector populations with unique functions at diverse tissue sites. Further insight into the mechanisms of how TRM function and respond to pathogens and malignancies at different mucosal sites will help to shape future vaccine and immunotherapeutic approaches. Here, we review the current understanding of TRM function and biology at four major mucosal sites: gastrointestinal tract, lung, head and neck, as well as female reproductive tract. We also summarize our current knowledge of how TRM targets invading pathogens and developing tumor cells at these mucosal sites and contemplate how TRMs may be exploited to protect from infections and cancer.

Trivalent nucleoside-modified mRNA vaccine yields durable memory B cell protection against genital herpes in preclinical models

Nucleoside-modified mRNA vaccines have gained global attention because of COVID-19. We evaluated a similar vaccine approach for preventing a chronic, latent genital infection rather than an acute respiratory infection. We used animal models to compare an HSV-2 trivalent nucleoside-modified mRNA vaccine with the same antigens prepared as proteins, with an emphasis on antigen-specific memory B cell responses and immune correlates of protection. In guinea pigs, serum neutralizing-antibody titers were higher at 1 month and declined far less by 8 months in mRNA- compared with protein-immunized animals. Both vaccines protected against death and genital lesions when infected 1 month after immunization; however, protection was more durable in the mRNA group compared with the protein group when infected after 8 months, an interval representing greater than 15% of the animal's lifespan. Serum and vaginal neutralizing-antibody titers correlated with protection against infection, as measured by genital lesions and vaginal virus titers 2 days after infection. In mice, the mRNA vaccine generated more antigen-specific memory B cells than the protein vaccine at early times after immunization that persisted for up to 1 year. High neutralizing titers and robust B cell immune memory likely explain the more durable protection by the HSV-2 mRNA vaccine.

Distinct populations of antigen-specific tissue-resident CD8+ T cells in human cervix mucosa

The ectocervix is part of the lower female reproductive tract (FRT), which is susceptible to sexually transmitted infections (STIs). Comprehensive knowledge of the phenotypes and T cell receptor (TCR) repertoire of tissue-resident memory T cells (TRMs) in the human FRT is lacking. We took single-cell RNA-Seq approaches to simultaneously define gene expression and TCR clonotypes of the human ectocervix. There were significantly more CD8+ than CD4+ T cells. Unsupervised clustering and trajectory analysis identified distinct populations of CD8+ T cells with IFNGhiGZMBloCD69hiCD103lo or IFNGloGZMBhiCD69medCD103hi phenotypes. Little overlap was seen between their TCR repertoires. Immunofluorescence staining showed that CD103+CD8+ TRMs were preferentially localized in the epithelium, whereas CD69+CD8+ TRMs were distributed evenly in the epithelium and stroma. Ex vivo assays indicated that up to 14% of cervical CD8+ TRM clonotypes were HSV-2 reactive in HSV-2-seropositive persons, reflecting physiologically relevant localization. Our studies identified subgroups of CD8+ TRMs in the human ectocervix that exhibited distinct expression of antiviral defense and tissue residency markers, anatomic locations, and TCR repertoires that target anatomically relevant viral antigens. Optimization of the location, number, and function of FRT TRMs is an important approach for improving host defenses to STIs.

B cells join T cell clusters in the host response to recurrent herpes simplex virus 2 infection

Recurrent genital herpes lesions are infiltrated by various leukocytes, yet the role of B cell subsets in this process is unknown. In this issue of the JCI, Ford et al. describe the presence and antibody-secreting role of local B cell populations in herpes simplex virus 2 (HSV-2) recurrent lesions. The authors analyzed a comprehensive array of sequential skin biopsy specimens from HSV-2-infected patients over time and at various stages of infection. Using immunofluorescence and in situ hybridization, the authors show the presence of rare IgD+ naive B cells and IgG-expressing antibody-secreting cells (ASCs) in recurrent HSV-2 lesions embedded in CD4+ T cell-rich dermal immune infiltrates, levels of which transiently increase during lesion reactivation and healing. Notably, local increases in HSV-2-specific antibodies in recurrent lesions were detected, whereas serum HSV-2 antibody levels remained stable. Future research is needed to understand the precise role of these tissue-visiting B cells in disease resolution.

Genital HSV-1 DNA detection is associated with a low inflammatory profile in HIV-uninfected South African women

OBJECTIVES

Genital herpes simplex virus (HSV) infections are common in South Africa and worldwide. While HSV-2 is known to cause genital lesions, HSV-1 is better known to cause oral infections. Due to the global rise in genital HSV-1 infections, we aimed to compare the genital cytokine environment associated with HSV-1 and HSV-2 infections and their relation to the proinflammatory genital immune environment associated with HIV risk in African women.

METHODS

HSV-1 and HSV-2 DNA were detected by quantitative real-time PCR in menstrual cup specimens collected from 251 HIV-negative women participating in the CAPRISA 083 study in Durban, South Africa. HSV shedding was defined as detection at >150 copies/mL. Forty-eight cytokines were measured in genital fluid by multiplexed ELISA, and multivariable regression models determined associations between genital cytokines and HSV DNA detection.

RESULTS

HSV-1 DNA detection (24/251 (9.6%)) and shedding (13/24 (54.2%)) was more common than HSV-2 (detection in 14/251 (5.6%), shedding in 0/14). None of the women with detectable HSV had evidence of genital lesions. HSV-2 DNA detection was associated with increased interleukin (IL)-18 and decreased cutaneous T-cell attracting chemokine concentrations, but only in univariable analysis. By contrast, in both univariable and multivariable analyses, the detection of HSV-1 DNA was associated with reduced concentrations of granulocyte-colony stimulating factor, IL-7, IL-4, platelet-derived growth factor-ββ and five proinflammatory cytokines associated with HIV risk: IL-6, IL-1β, macrophage inflammatory protein (MIP)-1α, MIP-1β and tumour necrosis factor-α.

CONCLUSIONS

That HSV-1 DNA was more commonly detected and shed than HSV-2 emphasises the need for clinical screening of both viruses, not just HSV-2 in young women. Efforts to reduce genital inflammation may need to consider implementing additional strategies to mitigate a rise in HSV replication.

[The role of herpesviruses in development of diseases of the urogenital tract and infertility in women]

This review presents the data on the spreading of all known human herpesviruses (НHVs) in female urogenital tract. According to the WHO almost 500 million people worldwide suffer from genital infection caused by НHVs. НHVs were detected in various inflammatory diseases of female upper and lower genital tract (vaginitis and cervicitis), in extrauterine pregnancy (in fallopian tubes), in infertility (cervical channel, endometrium and ovaries). Herpes simplex virus 1 (HSV‑1) was identified for the first time in oocytes after failed in vitro fertilization (IVF). НHVs produce negative effect on the entire reproductive process from conception to childbirth. It was established that HSV, cytomegalovirus (CMV) and human herpesvirus 6 (HHV-6) markedly increase the risk of spontaneous abortion, preterm birth and stillbirth. Intrauterine НHV infection is a major cause of congenital malformations. Data on humoral and cell immunity in genital herpesvirus infections (НHVI) are also reviewed. Intravaginal HSV‑2 infection changes cell composition of vaginal mucosa, i.e., together with cells mobilized from the blood, protective role is performed by resident memory T‑cells (TRM), natural killer cells (NK‑cells) and regulatory T‑cells (Treg) whose function consists in maintaining the balance of the activities of lymphocytes. Constant НHVI spreading is largely explained by transition of primary infection to potentially reactivating latent form, since latent virus is unavailable to immune recognition and medicines. The genome editing system CRISPR/Cas9 can recognize and modify not only active but also latent viruses. The promising pilot results with the use of this system offer the possibility of developing innovative technologies for НHV elimination and НHVI eradication.

Subclinical Genital Herpes Shedding in HIV/Herpes Simplex Virus 2-Coinfected Women during Antiretroviral Therapy Is Associated with an Increase in HIV Tissue Reservoirs and Potentially Promotes HIV Evolution

Antigen (Ag)-specific immune responses to chronic infections, such as herpes simplex virus type 2 (HSV-2) in HIV/HSV-coinfected persons, may sustain HIV tissue reservoirs by promoting T-cell proliferation but are poorly studied in women on antiretroviral therapy (ART). Mixed anogenital swabs and cervical secretions were self-collected by nine HIV/HSV-2-coinfected women during ART for 28 days to establish subclinical HSV DNA shedding rates and detection of HIV RNA by real-time PCR. Typical herpes lesion site biopsy (TLSB) and cervical biopsy specimens were collected at the end of the daily sampling period. Nucleic acids (NA) isolated from biopsy specimens had HIV quantified and HIV envC2-V5 single-genome amplification (SGA) and T-cell receptor (TCR) repertoires assessed. Women had a median CD4 count of 537 cells/μl (IQR: 483 to 741) at enrollment and HIV plasma viral loads of <40 copies/ml. HSV DNA was detected on 12% of days (IQR: 2 to 25%) from anogenital specimens. Frequent subclinical HSV DNA shedding was associated with increased HIV DNA tissue concentrations and increased divergence from the most recent common ancestor (MRCA), an indicator of HIV replication. Distinct predominant TCR clones were detected in cervical and TLSB specimens in a woman with frequent HSV DNA shedding, with mixing of minor variants between her tissues. In contrast, more limited TCR repertoire mixing was observed in two women with less frequent subclinical HSV DNA shedding. Subclinical HSV shedding in HIV/HSV-coinfected women during ART may sustain HIV tissue reservoirs via Ag exposure or HIV replication. This study provides evidence supporting further study of interventions targeting suppression of Ag-specific immune responses as a component of HIV cure strategies.IMPORTANCE Persons with HIV infection are frequently coinfected with chronic herpesviruses, which periodically replicate and produce viable herpes virions, particularly in anogenital and cervical tissues. Persistent protein expression results in proliferation of CD8+ and CD4+ T cells, and the latter could potentially expand and sustain HIV tissue reservoirs. We found HSV genital shedding rates were positively correlated with HIV DNA concentrations and HIV divergence from ancestral sequences in tissues. Our work suggests that immune responses to common coinfections, such as herpesviruses, may sustain HIV tissue reservoirs during suppressive ART, suggesting future cure strategies should study interventions to suppress replication or reactivation of chronic herpes infections.

Estradiol Enhances Antiviral CD4+ Tissue-Resident Memory T Cell Responses following Mucosal Herpes Simplex Virus 2 Vaccination through an IL-17-Mediated Pathway

Estradiol (E2) is a sex hormone which has been shown to be protective against sexually transmitted infections such as herpes simplex virus 2 (HSV-2). However, few studies have examined the underlying mechanisms by which this occurs. Here, we investigated the effect of E2 on the establishment of memory T cells post-intranasal immunization with HSV-2. CD4⁺ T cell responses first appeared in the upper respiratory tract (URT) within 3 days postimmunization before being detected in the female reproductive tract (FRT) at 7 days. E2 treatment resulted in greater and earlier T_h17 responses, which preceded augmented T_h1 responses at these sites. The CD4⁺ T cells persisted in the URT for up to 28 days, and E2 treatment resulted in higher frequencies of memory T cells. Intranasal immunization also led to the establishment of CD4⁺ tissue-resident memory T cells (T_RM cells) in the FRT, and E2 treatment resulted in increased T_h1 and T_h17 T_RM cells. When the migration of circulating T cells into the FRT was blocked by FTY720, immunized E2-treated mice remained completely protected against subsequent genital HSV-2 challenge compared to non-E2 controls, confirming that T_RM cells alone are adequate for protection in these mice. Finally, the enhanced vaginal T_h1 T_RM cells present in E2-treated mice were found to be modulated through an interleukin 17 (IL-17)-mediated pathway, as E2-treated IL-17A-deficient mice had impaired establishment of T_h1 T_RM cells. This study describes a novel role for E2 in enhancing CD4⁺ memory T cells and provides insight on potential strategies for generating optimal immunity during vaccination.IMPORTANCE Herpes simplex virus 2 (HSV-2) is a highly prevalent sexually transmitted infection for which there is currently no vaccine available. Interestingly, the female sex hormone estradiol has been shown to be protective against HSV-2. However, the underlying mechanisms by which this occurs remains relatively unknown. Our study demonstrates that under the influence of estradiol treatment, intranasal immunization with an attenuated strain of HSV-2 leads to enhanced establishment of antiviral memory T cell responses in the upper respiratory tract and female reproductive tract. In these sites, estradiol treatment leads to greater T_h17 memory cells, which precede enhanced T_h1 memory responses. Consequently, the T cell responses mounted by tissue-resident memory cells in the female reproductive tract of estradiol-treated mice are sufficient to protect mice against vaginal HSV-2 challenge. This study offers important insights regarding the regulation of mucosal immunity by hormones and on potential strategies for generating optimal immunity during vaccination.

Herpes Simplex Virus Type 1 Interactions with the Interferon System

The interferon (IFN) system is one of the first lines of defense activated against invading viral pathogens. Upon secretion, IFNs activate a signaling cascade resulting in the production of several interferon stimulated genes (ISGs), which work to limit viral replication and establish an overall anti-viral state. Herpes simplex virus type 1 is a ubiquitous human pathogen that has evolved to downregulate the IFN response and establish lifelong latent infection in sensory neurons of the host. This review will focus on the mechanisms by which the host innate immune system detects invading HSV-1 virions, the subsequent IFN response generated to limit viral infection, and the evasion strategies developed by HSV-1 to evade the immune system and establish latency in the host.

Multivalent DNA vaccine protects against genital herpes by T-cell immune induction in vaginal mucosa

Genital herpes is one of the most common sexually transmitted infections (STIs), and it is mainly caused by the neurotropic herpes simplex virus (HSV-2). Not only does this infection cause ulcers, but HSV-2 can also stay in a latent state in the nervous system of the host throughout their lifespan. As a result, many people do not know that they harbor this infection. Moreover, HSV-2 serves as a major risk factor for human immunodeficiency virus (HIV) infection and can be transmitted to the fetus. Despite the high risk of infection and adverse effects, attempts at development of an effective vaccine for HSV-2 have not yet been successful. In this study, we developed a DNA vaccine for HSV-2 (SL-V20). This multivalent DNA vaccine effectively reduced the pathological symptoms of infection and induced efficient elimination of the virus in a mouse model. Intramuscular injection of SL-V20 led to induction of an HSV-2-specific T-cell response in the vagina, the major infection site, and in draining lymph organs. Dendritic cells (DCs), especially basic leucine zipper ATF-like transcription factor 3 (Baft3)⁺ DCs and partially interferon regulatory factor 4 (Irf4)⁺ DCs, were involved in this T-cell-mediated protective response, while B cells were dispensable for these prophylactic effects. This study demonstrates that SL-V20 offers a novel and effective vaccine against vaginal HSV-2 infection and may be applicable to patients, pending validation in clinical studies.

Biologic interactions between HSV-2 and HIV-1 and possible implications for HSV vaccine development

Development of a safe and effective vaccine against herpes simplex virus type 2 (HSV-2) has the potential to limit the global burden of HSV-2 infection and disease, including genital ulcer disease and neonatal herpes, and is a global sexual and reproductive health priority. Another important potential benefit of an HSV-2 vaccine would be to decrease HIV infections, as HSV-2 increases the risk of HIV-1 acquisition several-fold. Acute and chronic HSV-2 infection creates ulcerations and draws dendritic cells and activated CD4+ T cells into genital mucosa. These cells are targets for HIV entry and replication. Prophylactic HSV-2 vaccines (to prevent infection) and therapeutic vaccines (to modify or treat existing infections) are currently under development. By preventing or modifying infection, an effective HSV-2 vaccine could limit HSV-associated genital mucosal inflammation and thus HIV risk. However, a vaccine might have competing effects on HIV risk depending on its mechanism of action and cell populations generated in the genital mucosa. In this article, we review biologic interactions between HSV-2 and HIV-1, consider HSV-2 vaccine development in the context of HIV risk, and discuss implications and research needs for future HSV vaccine development.

Increased Frequency of Virus Shedding by Herpes Simplex Virus 2-Infected Guinea Pigs in the Absence of CD4+ T Lymphocytes

Reactivation of herpes simplex virus 2 (HSV-2) results in infection of epithelial cells at the neuro-epithelial junction and shedding of virus at the epithelial surface. Virus shedding can occur in either the presence or absence of clinical disease and is usually of short duration, although the shedding frequency varies among individuals. The basis for host control of virus shedding is not well understood, although adaptive immune mechanisms are thought to play a central role. To determine the importance of CD4⁺ T cells in control of HSV-2 shedding, this subset of immune cells was depleted from HSV-2-infected guinea pigs by injection of an anti-CD4 monoclonal antibody (MAb). Guinea pigs were treated with the depleting MAb after establishment of a latent infection, and vaginal swabs were taken daily to monitor shedding by quantitative PCR. The cumulative number of HSV-2 shedding days and the mean number of days virus was shed were significantly increased in CD4-depleted compared to control-treated animals. However, there was no difference in the incidence of recurrent disease between the two treatment groups. Serum antibody levels and the number of HSV-specific antibody-secreting cells in secondary lymphoid tissues were unaffected by depletion of CD4⁺ T cells; however, the frequency of functional HSV-specific, CD8⁺ gamma interferon-secreting cells was significantly decreased. Together, these results demonstrate an important role for CD4⁺ T lymphocytes in control of virus shedding that may be mediated in part by maintenance of HSV-specific CD8⁺ T cell populations. These results have important implications for development of therapeutic vaccines designed to control HSV-2 shedding.IMPORTANCE Sexual transmission of HSV-2 results from viral shedding following reactivation from latency. The immune cell populations and mechanisms that control HSV-2 shedding are not well understood. This study examined the role of CD4⁺ T cells in control of virus shedding using a guinea pig model of genital HSV-2 infection that recapitulates the shedding of virus experienced by humans. We found that the frequency of virus-shedding episodes, but not the incidence of clinical disease, was increased by depletion of CD4⁺ T cells. The HSV-specific antibody response was not diminished, but frequency of functional HSV-reactive CD8⁺ T cells was significantly diminished by CD4 depletion. These results confirm the role of cell-mediated immunity and highlight the importance of CD4⁺ T cells in controlling HSV shedding, suggesting that therapeutic vaccines designed to reduce transmission by controlling HSV shedding should include specific enhancement of HSV-specific CD4⁺ T cell responses.

Herpes Simplex Virus Type 2 Infection-Induced Expression of CXCR3 Ligands Promotes CD4+ T Cell Migration and Is Regulated by the Viral Immediate-Early Protein ICP4

HSV-2 infection-induced CXCR3 ligands are important for the recruitment of virus-specific CD8⁺ T cells, but their impact on CD4⁺ T cell trafficking remains to be further determined. Given that recruitment of CD4⁺ T cells to infection areas may be one of the mechanisms that account for HSV-2 infection-mediated enhancement of HIV-1 sexual transmission, here we investigated the functionality of HSV-2 infection-induced CXCR3 ligands CXCL9, CXCL10, and CXCL11 in vivo and in vitro, and determined the viral components responsive for such induction and the underlying mechanisms. We first found that the expression of CXCR3 ligands CXCL9, CXCL10, and CXCL11 was increased in mice following vaginal challenge with HSV-2, while CXCL9 played a predominant role in the recruitment of CD4⁺ T cells to the vaginal foci of infected mice. HSV-2 infection also induced the production of CXCL9, CXCL10, and CXCL11 in human cervical epithelial cells. Of note, although HSV-2 induced the expression of all the three CXCR3 ligands, the induced CXCL9 appeared to play a predominant role in promoting CD4⁺ T cell migration, reflecting that the concentrations of CXCL10 and CXCL11 required for CD4⁺ T cell migration are higher than that of CXCL9. We further revealed that, ICP4, an immediate-early protein of HSV-2, is crucial in promoting CXCR3 ligand expression through the activation of p38 MAPK pathway. Mechanistically, ICP4 binds to corresponding promoters of CXCR3 ligands via interacting with the TATA binding protein (TBP), resulting in the transcriptional activation of the corresponding promoters. Taken together, our study highlights HSV-2 ICP4 as a vital viral protein in promoting CXCR3 ligand expression and CXCL9 as the key induced chemokine in mediating CD4⁺ T cell migration. Findings in this study have shed light on HSV-2 induced leukocyte recruitment which may be important for understanding HSV-2 infection-enhanced HIV-1 sexual transmission and the development of intervention strategies.

Asian Elephant T Cell Responses to Elephant Endotheliotropic Herpesvirus

Elephant endotheliotropic herpesvirus (EEHV) can cause lethal hemorrhagic disease in juvenile Asian elephants, an endangered species. One hypothesis to explain this vulnerability of some juvenile elephants is that they fail to mount an effective T cell response to the virus. To our knowledge, there have been no studies of Asian elephant T cell responses to EEHV. To address this deficiency, we validated the gamma interferon (IFN-γ) enzyme-linked immunospot assay for tracking antigen-directed T cell activity by monitoring rabies-specific responses in vaccinated elephants. In addition, we generated monoclonal antibodies to Asian elephant CD4 and CD8 to facilitate phenotypic T cell profiling. Using these tools, we screened healthy elephants with a history of EEHV infection for reactivity against nine EEHV proteins whose counterparts in other herpesviruses are known to induce T cell responses in their natural hosts. We identified glycoprotein B (gB) and the putative regulatory protein E40 as the most immunogenic T cell targets (IFN-γ responses in five of seven elephants), followed by the major capsid protein (IFN-γ responses in three of seven elephants). We also observed that IFN-γ responses were largely from CD4⁺ T cells. We detected no activity against the predicted major immediate early (E44) and large tegument (E34) proteins, both immunodominant T cell targets in humans latently infected with cytomegalovirus. These studies identified EEHV-specific T cells in Asian elephants for the first time, lending insight into the T cell priming that might be required to protect against EEHV disease, and will guide the design of effective vaccine strategies.

IMPORTANCE Endangered Asian elephants are facing many threats, including lethal hemorrhagic disease from elephant endotheliotropic herpesvirus (EEHV). EEHV usually establishes chronic, benign infections in mature Asian elephants but can be lethal to juvenile elephants in captivity and the wild. It is the leading cause of death in captive Asian elephants in North America and Europe. Despite the availability of sensitive tests and protocols for treating EEHV-associated illness, these measures are not always effective. The best line of defense would be a preventative vaccine. We interrogated normal healthy elephants previously infected with EEHV for T cell responses to nine EEHV proteins predicted to induce cellular immune responses. Three proteins elicited IFN-γ responses, suggesting their potential usefulness as vaccine candidates. Our work is the first to describe T cell responses to a member of the proposed fourth subfamily of mammalian herpesviruses, the Deltaherpesvirinae, within a host species in the clade Afrotheria. An EEHV vaccine would greatly contribute to the health care of Asian and African elephants that are also susceptible to this disease.

Enrichment of herpes simplex virus type 2 (HSV-2) reactive mucosal T cells in the human female genital tract

Local mucosal cellular immunity is critical in providing protection from HSV-2. To characterize and quantify HSV-2-reactive mucosal T cells, lymphocytes were isolated from endocervical cytobrush and biopsy specimens from 17 HSV-2-infected women and examined ex vivo for the expression of markers associated with maturation and tissue residency and for functional T-cell responses to HSV-2. Compared with their circulating counterparts, cervix-derived CD4+ and CD8+ T cells were predominantly effector memory T cells (CCR7-/CD45RA-) and the majority expressed CD69, a marker of tissue residency. Co-expression of CD103, another marker of tissue residency, was highest on cervix-derived CD8+ T cells. Functional HSV-2 reactive CD4+ and CD8+ T-cell responses were detected in cervical samples and a median of 17% co-expressed CD103. HSV-2-reactive CD4+ T cells co-expressed IL-2 and were significantly enriched in the cervix compared with blood. This first direct ex vivo documentation of local enrichment of HSV-2-reactive T cells in the human female genital mucosa is consistent with the presence of antigen-specific tissue-resident memory T cells. Ex vivo analysis of these T cells may uncover tissue-specific mechanisms of local control of HSV-2 to assist the development of vaccine strategies that target protective T cells to sites of HSV-2 infection.

Diminished CD103 (αEβ7) Expression on Resident T Cells from the Female Genital Tract of HIV-Positive Women

Background:

Tissue resident memory T cells (TrM) provide an enhanced response against infection at mucosal surfaces, yet their function has not been extensively studied in humans, including the female genital tract (FGT).

Methods:

Using polychromatic flow cytometry, we studied TrM cells, defined as CD62L-CCR7-CD103⁺CD69⁺ CD4⁺ and CD8⁺ T cells in mucosa-derived T cells from healthy and HIV-positive women.

Results:

We demonstrate that TrM are present in the FGT of healthy and HIV-positive women. The expression of the mucosal retention receptor, CD103, from HIV-positive women was reduced compared to healthy women and was lowest in women with CD4 counts < 500 cells/mm³. Furthermore, CD103 expression on mucosa-derived CD8⁺ T cells correlated with antigen-specific IFN-γ production by mucosal CD4⁺ T cells and was inversely correlated with T-bet from CD8⁺CD103⁺ mucosa-derived T cells.

Conclusions:

These data suggest that CD4⁺ T cells, known to be impaired during HIV-1 infection and necessary for the expression of CD103 in murine models, may play a role in the expression of CD103 on resident T cells from the human FGT.

Subclinical Herpes Simplex Virus Type 1 Infections Provide Site-Specific Resistance to an Unrelated Pathogen

HSV-1 infections of the cornea range in severity from minor transient discomfort to the blinding disease herpes stromal keratitis, yet most patients experience a single episode of epithelial keratitis followed by re-establishment of a clear cornea. We asked whether a single transient episode of HSV-1 epithelial keratitis causes long-term changes in the corneal microenvironment that influence immune responses to subsequent corneal infection or trauma. We showed that C57BL/6 mouse corneas infected with HSV-1 KOS, which induces transient herpes epithelial keratitis without herpes stromal keratitis sequelae, possessed a significant leukocytic infiltrate composed primarily of CD4⁺ T cells and macrophages along with elevated chemokines and cytokines that persisted without loss of corneal clarity (subclinical inflammation). Chemokine and cytokine expression was CD4⁺ T cell dependent, in that their production was significantly reduced by systemic CD4⁺ T cell depletion starting before infection, although short-term (3-d) local CD4⁺ T cell depletion postinfection did not influence chemokine levels in cornea. Corneas with subclinical inflammation developed significantly greater trauma-induced inflammation when they were recipients of syngeneic corneal transplants but also exhibited significantly increased resistance to infections by unrelated pathogens, such as pseudorabies virus. The resistance to pseudorabies virus was CD4⁺ T cell dependent, because it was eliminated by local CD4⁺ T cell depletion from the cornea. We conclude that transient HSV-1 corneal infections cause long-term alterations of the corneal microenvironment that provide CD4-dependent innate resistance to subsequent infections by antigenically unrelated pathogens.

Evolution of rational vaccine designs for genital herpes immunotherapy

Immunotherapeutic vaccines have emerged as a novel treatment modality for genital herpes, a sexually transmitted disease mainly caused by herpes simplex virus type 2. The approaches to identify potential vaccine antigens have evolved from classic virus attenuation and characterization of antibody and T cell responses in exposed, but seronegative individuals, to systematic screens for novel T cell antigens. Combined with implementation of novel vaccine concepts revolving around immune evasion and local recruitment of immune effectors, the development of a safe and effective therapeutic vaccine is within reach. Here, we describe the vaccine approaches that currently show promise at clinical and pre-clinical stages and link them to the evolving scientific strategies that led to their identification.

A novel HSV-2 subunit vaccine induces GLA-dependent CD4 and CD8 T cell responses and protective immunity in mice and guinea pigs

BACKGROUND/OBJECTIVES

There is currently no licensed prophylactic or therapeutic vaccine for HSV-2 infection.

METHODS

We developed a novel preclinical vaccine candidate, G103, consisting of three recombinantly expressed HSV-2 proteins (gD and the UL19 and UL25 gene products) adjuvanted with the potent synthetic TLR4 agonist glucopyranosyl lipid A (GLA) formulated in stable emulsion. The vaccine was tested for immunogenicity and efficacy in pre-clinical models for preventative and therapeutic vaccination.

RESULTS

Vaccination of mice with G103 elicited antigen-specific binding and neutralizing antibody responses, as well as robust CD4 and CD8 effector and memory T cells. The T cell responses were further boosted by subsequent challenge with live virus. Prophylactic immunization completely protected against lethal intravaginal HSV-2 infection in mice, with only transient replication of virus in the genital mucosa and sterilizing immunity in dorsal root ganglia. Supporting the use of G103 therapeutically, the vaccine expanded both CD4 and CD8 T cells induced in mice by previous infection with HSV-2. In the guinea pig model of recurrent HSV-2 infection, therapeutic immunization with G103 was approximately 50% effective in reducing the number of lesions per animal as well as the overall lesions score.

CONCLUSIONS

Taken together, the data show that G103 is a viable candidate for development of a novel prophylactic and therapeutic HSV-2 vaccine.

The Sordid Affair Between Human Herpesvirus and HIV

Both human immunodeficiency virus (HIV) and human herpesvirus (HHV) infections persist lifelong, and almost all individuals infected with HIV are also infected with ≥1 HHV. These coinfections are not independent processes or benign. In this review, we discuss how HHVs, and cytomegalovirus in particular, interact with concurrent HIV infection, and we describe the next steps necessary to understand and address these connections.

Seminal Shedding of CMV and HIV Transmission among Men Who Have Sex with Men

As in many urban areas in the United States, the largest burden of the HIV epidemic in San Diego is borne by men who have sex with men (MSM). Using data from well-characterized HIV transmitting and non-transmitting partner pairs of MSM in San Diego, we calculated the population attributable risk (PAR) of HIV transmissions for different co-infections common among MSM in this area. We found that over a third of HIV transmissions could be potentially attributed to genital shedding of cytomegalovirus (CMV) (111 transmission events), compared to 21% potentially attributed to bacterial sexually transmitted infections (STI) (62 events) and 17% to herpes simplex virus type-2 (HSV-2) (51 events). Although our study cannot infer causality between the described associations and is limited in sample size, these results suggest that interventions aimed at reducing CMV shedding might be an attractive HIV prevention strategy in populations with high prevalence of CMV co-infection.