Identification of novel virus-specific antigens by CD4⁺ and CD8⁺ T cells from asymptomatic HSV-2 seropositive and seronegative donors

Therapeutic vaccines for herpesviruses

Herpesviruses establish latent infections, and most reactivate frequently, resulting in symptoms and virus shedding in healthy individuals. In immunocompromised patients, reactivating virus can cause severe disease. Persistent EBV has been associated with several malignancies in both immunocompromised and nonimmunocompromised persons. Reactivation and shedding occur with most herpesviruses, despite potent virus-specific antibodies and T cell immunity as measured in the blood. The licensure of therapeutic vaccines to reduce zoster indicates that effective therapeutic vaccines for other herpesviruses should be feasible. However, varicella-zoster virus is different from other human herpesviruses in that it is generally only shed during varicella and zoster. Unlike prophylactic vaccines, in which the correlate of immunity is antibody function, T cell immunity is the correlate of immunity for the only effective therapeutic herpesvirus vaccine-zoster vaccine. While most studies of therapeutic vaccines have measured immunity in the blood, cellular immunity at the site of reactivation is likely critical for an effective therapeutic vaccine for certain viruses. This Review summarizes the status of therapeutic vaccines for herpes simplex virus, cytomegalovirus, and Epstein-Barr virus and proposes approaches for future development.

Therapeutic Prime/Pull Vaccination of HSV-2 Infected Guinea Pigs with the Ribonucleotide Reductase 2 (RR2) Protein and CXCL11 Chemokine Boosts Antiviral Local Tissue-Resident and Effector Memory CD4+ and CD8+ T Cells and Protects Against Recurrent Genital Herpes

Following acute herpes simplex virus type 2 (HSV-2) infection, the virus undergoes latency in sensory neurons of the dorsal root ganglia (DRG). Intermittent virus reactivation from latency and shedding in the vaginal mucosa (VM) causes recurrent genital herpes. While T-cells appear to play a role in controlling virus reactivation and reducing the severity of recurrent genital herpes, the mechanisms for recruiting these T-cells into DRG and VM tissues remain to be fully elucidated. The present study investigates the effect of CXCL9, CXCL10, and CXCL11 T-cell-attracting chemokines on the frequency and function of DRG- and VM-resident CD4+ and CD8+ T cells and its effect on the frequency and severity of recurrent genital herpes. HSV-2 latent-infected guinea pigs were immunized intramuscularly with the HSV-1 RR2 protein (Prime) and subsequently treated intravaginally with the neurotropic adeno-associated virus type 8 (AAV-8) expressing CXCL9, CXCL10, or CXCL11 T-cell-attracting chemokines (Pull). Compared to the RR2 therapeutic vaccine alone, the RR2/CXCL11 prime/pull therapeutic vaccine significantly increased the frequencies of functional tissue-resident (TRM cells) and effector (TEM cells) memory CD4+ and CD8+ T cells in both DRG and VM tissues. This was associated with less virus shedding in the healed genital mucosal epithelium and reduced frequency and severity of recurrent genital herpes. These findings confirm the role of local DRG- and VM-resident CD4+ and CD8+ TRM and TEM cells in reducing virus reactivation shedding and the severity of recurrent genital herpes and propose the novel prime/pull vaccine strategy to protect against recurrent genital herpes.

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.

An Empirical Antigen Selection Method Identifies Neoantigens That Either Elicit Broad Antitumor T-cell Responses or Drive Tumor Growth

Neoantigens are critical targets of antitumor T-cell responses. The ATLAS bioassay was developed to identify neoantigens empirically by expressing each unique patient-specific tumor mutation individually in Escherichia coli, pulsing autologous dendritic cells in an ordered array, and testing the patient's T cells for recognition in an overnight assay. Profiling of T cells from patients with lung cancer revealed both stimulatory and inhibitory responses to individual neoantigens. In the murine B16F10 melanoma model, therapeutic immunization with ATLAS-identified stimulatory neoantigens protected animals, whereas immunization with peptides associated with inhibitory ATLAS responses resulted in accelerated tumor growth and abolished efficacy of an otherwise protective vaccine. A planned interim analysis of a clinical study testing a poly-ICLC adjuvanted personalized vaccine containing ATLAS-identified stimulatory neoantigens showed that it is well tolerated. In an adjuvant setting, immunized patients generated both CD4⁺ and CD8⁺ T-cell responses, with immune responses to 99% of the vaccinated peptide antigens. SIGNIFICANCE: Predicting neoantigens in silico has progressed, but empirical testing shows that T-cell responses are more nuanced than straightforward MHC antigen recognition. The ATLAS bioassay screens tumor mutations to uncover preexisting, patient-relevant neoantigen T-cell responses and reveals a new class of putatively deleterious responses that could affect cancer immunotherapy design.This article is highlighted in the In This Issue feature, p. 521.

Human Epitopes Identified from Herpes Simplex Virus Tegument Protein VP11/12 (UL46) Recall Multifunctional Effector Memory CD4+ TEM Cells in Asymptomatic Individuals and Protect from Ocular Herpes Infection and Disease in "Humanized" HLA-DR Transgenic Mice

While the role of CD8+ T cells in the control of herpes simplex virus 1 (HSV-1) infection and disease is gaining wider acceptance, a direct involvement of effector CD4+ T cells in this protection and the phenotype and function of HSV-specific human CD4+ T cell epitopes remain to be fully elucidated. In the present study, we report that several epitopes from the HSV-1 virion tegument protein (VP11/12) encoded by UL46 are targeted by CD4+ T cells from HSV-seropositive asymptomatic individuals (who, despite being infected, never develop any recurrent herpetic disease). Among these, we identified two immunodominant effector memory CD4+ TEM cell epitopes, amino acids (aa) 129 to 143 of VP11/12 (VP11/12129-143) and VP11/12483-497, using in silico, in vitro, and in vivo approaches based on the following: (i) a combination of the TEPITOPE algorithm and PepScan library scanning of the entire 718 aa of HSV-1 VP11/12 sequence; (ii) an in silico peptide-protein docking analysis and in vitro binding assay that identify epitopes with high affinity to soluble HLA-DRB1 molecules; and (iii) an ELISpot assay and intracellular detection of gamma interferon (IFN-γ), CD107a/b degranulation, and CD4+ T cell carboxyfluorescein succinimidyl ester (CFSE) proliferation assays. We demonstrated that native VP11/12129-143 and VP11/12483-497 epitopes presented by HSV-1-infected HLA-DR-positive target cells were recognized mainly by effector memory CD4+ TEM cells while being less targeted by FOXP3+ CD4+ CD25+ regulatory T cells. Furthermore, immunization of HLA-DR transgenic mice with a mixture of the two immunodominant human VP11/12 CD4+ TEM cell epitopes, but not with cryptic epitopes, induced HSV-specific polyfunctional IFN-γ-producing CD107ab+ CD4+ T cells associated with protective immunity against ocular herpes infection and disease.IMPORTANCE We report that naturally protected HSV-1-seropositive asymptomatic individuals develop a higher frequency of antiviral effector memory CD4+ TEM cells specific to two immunodominant epitopes derived from the HSV-1 tegument protein VP11/12. Immunization of HLA-DR transgenic mice with a mixture of these two immunodominant CD4+ T cell epitopes induced a robust antiviral CD4+ T cell response in the cornea that was associated with protective immunity against ocular herpes. The emerging concept of developing an asymptomatic herpes vaccine that would boost effector memory CD4+ and CD8+ TEM cell responses is discussed.

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.

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

Chronic viruses such as herpes simplex virus 1 (HSV-1) evade the hosts' immune system by inducing the exhaustion of antiviral T cells. In the present study, we found that exhausted HSV-specific CD8⁺ T cells, with elevated expression of programmed death ligand-1 (PD-1) and lymphocyte activation gene-3 (LAG-3) receptors were frequent in symptomatic patients, with a history of numerous episodes of recurrent corneal herpetic disease, compared to asymptomatic patients who never had corneal herpetic disease. Subsequently, using a rabbit model of recurrent ocular herpes, we found that the combined blockade of PD-1 and LAG-3 pathways with antagonist antibodies significantly restored the function of tissue-resident antiviral CD8⁺ T_RM cells in both the cornea and the trigeminal ganglia (TG). An increased number of functional tissue-resident HSV-specific CD8⁺ T_RM cells in latently infected rabbits was associated with protection against recurrent herpes infection and disease. Compared to the PD-1 or LAG-3 blockade alone, the combined blockade of PD-1 and LAG-3 appeared to have a synergistic effect in generating frequent polyfunctional Ki-67⁺, IFN-γ⁺, CD107⁺, and CD8⁺ T cells. Moreover, using the human leukocyte antigen (HLA) transgenic rabbit model, we found that dual blockade of PD-1 and LAG-3 reinforced the effect of a multiepitope vaccine in boosting the frequency of HSV-1-specific CD8⁺ T_RM cells and reducing disease severity. Thus, both the PD-1 and the LAG-3 exhaustion pathways play a fundamental role in ocular herpes T cell immunopathology and provide important immune checkpoint targets to combat ocular herpes.IMPORTANCE HSV-specific tissue-resident memory CD8⁺ T_RM cells play a critical role in preventing virus reactivation from latently infected TG and subsequent virus shedding in tears that trigger the recurrent corneal herpetic disease. In this report, we determined how the dual blockade of PD-1 and LAG-3 immune checkpoints, combined with vaccination, improved the function of CD8⁺ T_RM cells associated with a significant reduction in recurrent ocular herpes in HLA transgenic (Tg) rabbit model. The combined blockade of PD-1 and LAG-3 appeared to have a synergistic effect in generating frequent polyfunctional CD8⁺ T_RM cells that infiltrated both the cornea and the TG. The preclinical findings using the established HLA Tg rabbit model of recurrent herpes highlight that blocking immune checkpoints combined with a T cell-based vaccine would provide an important strategy to combat recurrent ocular herpes in the clinic.

A Randomized, Double-Blinded, Placebo-Controlled, Phase 1 Study of a Replication-Defective Herpes Simplex Virus (HSV) Type 2 Vaccine, HSV529, in Adults With or Without HSV Infection

BACKGROUND

Herpes simplex virus 2 (HSV2) causes genital herpes in >400 million persons worldwide.

METHODS

We conducted a randomized, double-blinded, placebo-controlled trial of a replication-defective HSV2 vaccine, HSV529. Twenty adults were enrolled in each of 3 serogroups of individuals: those negative for both HSV1 and HSV2 (HSV1-/HSV2-), those positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+), and those positive for HSV1 and negative for HSV2 (HSV1+/HSV2-). Sixty participants received vaccine or placebo at 0, 1, and 6 months. The primary end point was the frequency of solicited local and systemic reactions to vaccination.

RESULTS

Eighty-nine percent of vaccinees experienced mild-to-moderate solicited injection site reactions, compared with 47% of placebo recipients (95% confidence interval [CI], 12.9%-67.6%; P = .006). Sixty-four percent of vaccinees experienced systemic reactions, compared with 53% of placebo recipients (95% CI, -17.9% to 40.2%; P = .44). Seventy-eight percent of HSV1-/HSV2- vaccine recipients had a ≥4-fold increase in neutralizing antibody titer after 3 doses of vaccine, whereas none of the participants in the other serogroups had such responses. HSV2-specific CD4+ T-cell responses were detected in 36%, 46%, and 27% of HSV1-/HSV2-, HSV1±/HSV2+, and HSV1+/HSV2- participants, respectively, 1 month after the third dose of vaccine, and CD8+ T-cell responses were detected in 14%, 8%, and 18% of participants, respectively.

CONCLUSIONS

HSV529 vaccine was safe and elicited neutralizing antibody and modest CD4+ T-cell responses in HSV-seronegative vaccinees.

CLINICAL TRIALS REGISTRATION

NCT01915212.

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+ TRM Cells Associated with Protection against Recurrent Genital Herpes

Reactivation of herpes simplex virus 2 (HSV-2) from latency causes viral shedding that develops into recurrent genital lesions. The immune mechanisms of protection against recurrent genital herpes remain to be fully elucidated. In this preclinical study, we investigated the protective therapeutic efficacy, in the guinea pig model of recurrent genital herpes, of subunit vaccine candidates that were based on eight recombinantly expressed HSV-2 envelope and tegument proteins. These viral protein antigens (Ags) were rationally selected for their ability to recall strong CD4+ and CD8+ T-cell responses from naturally "protected" asymptomatic individuals, who, despite being infected, never develop any recurrent herpetic disease. Out of the eight HSV-2 proteins, the envelope glycoprotein D (gD), the tegument protein VP22 (encoded by the UL49 gene), and ribonucleotide reductase subunit 2 protein (RR2; encoded by the UL40 gene) produced significant protection against recurrent genital herpes. The RR2 protein, delivered either intramuscularly or intravaginally with CpG and alum adjuvants, (i) boosted the highest neutralizing antibodies, which appear to cross-react with both gB and gD, and (ii) enhanced the numbers of functional gamma interferon (IFN-γ)-producing CRTAM+ CFSE+ CD4+ and CRTAM+ CFSE+ CD8+ TRM cells, which express low levels of PD-1 and TIM-3 exhaustion markers and were localized to healed sites of the vaginal mucocutaneous (VM) tissues. The strong B- and T-cell immunogenicity of the RR2 protein was associated with a significant decrease in virus shedding and a reduction in both the severity and frequency of recurrent genital herpes lesions. In vivo depletion of either CD4+ or CD8+ T cells significantly abrogated the protection. Taken together, these preclinical results provide new insights into the immune mechanisms of protection against recurrent genital herpes and promote the tegument RR2 protein as a viable candidate Ag to be incorporated in future genital herpes therapeutic mucosal vaccines.IMPORTANCE Recurrent genital herpes is one of the most common sexually transmitted diseases, with a global prevalence of HSV-2 infection predicted to be over 536 million worldwide. Despite the availability of many intervention strategies, such as sexual behavior education, barrier methods, and the costly antiviral drug treatments, eliminating or at least reducing recurrent genital herpes remains a challenge. Currently, no FDA-approved therapeutic vaccines are available. In this preclinical study, we investigated the immunogenicity and protective efficacy, in the guinea pig model of recurrent genital herpes, of subunit vaccine candidates that were based on eight recombinantly expressed herpes envelope and tegument proteins. We discovered that similar to the dl5-29 vaccine, based on a replication-defective HSV-2 mutant virus, which has been recently tested in clinical trials, the RR2 protein-based subunit vaccine elicited a significant reduction in virus shedding and a decrease in both the severity and frequency of recurrent genital herpes sores. This protection correlated with an increase in numbers of functional tissue-resident IFN-γ+ CRTAM+ CFSE+ CD4+ and IFN-γ+ CRTAM+ CFSE+ CD8+ TRM cells that infiltrate healed sites of the vaginal tissues. Our study sheds new light on the role of TRM cells in protection against recurrent genital herpes and promotes the RR2-based subunit therapeutic vaccine to be tested in the clinic.

Herpes Simplex Virus Evasion of Early Host Antiviral Responses

Herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) have co-evolved with humans for thousands of years and are present at a high prevalence in the population worldwide. HSV infections are responsible for several illnesses including skin and mucosal lesions, blindness and even life-threatening encephalitis in both, immunocompetent and immunocompromised individuals of all ages. Therefore, diseases caused by HSVs represent significant public health burdens. Similar to other herpesviruses, HSV-1 and HSV-2 produce lifelong infections in the host by establishing latency in neurons and sporadically reactivating from these cells, eliciting recurrences that are accompanied by viral shedding in both, symptomatic and asymptomatic individuals. The ability of HSVs to persist and recur in otherwise healthy individuals is likely given by the numerous virulence factors that these viruses have evolved to evade host antiviral responses. Here, we review and discuss molecular mechanisms used by HSVs to evade early innate antiviral responses, which are the first lines of defense against these viruses. A comprehensive understanding of how HSVs evade host early antiviral responses could contribute to the development of novel therapies and vaccines to counteract these viruses.

Blockade of LAG-3 Immune Checkpoint Combined With Therapeutic Vaccination Restore the Function of Tissue-Resident Anti-viral CD8+ T Cells and Protect Against Recurrent Ocular Herpes Simplex Infection and Disease

Recurrent viral diseases often occur after the viruses evade the hosts' immune system, by inducing exhaustion of antiviral T cells. In the present study, we found that functionally exhausted herpes simplex virus type 1 (HSV-1) -specific CD8⁺ T cells, with elevated expression of lymphocyte activation gene-3 (LAG-3), an immune checkpoint receptor that promotes T cell exhaustion, were frequent in symptomatic (SYMP) patients with a history of numerous episodes of recurrent corneal herpetic disease. Similarly, following UV-B induced virus reactivation from latency the symptomatic wild-type (WT) B6 mice that developed increase virus shedding and severe recurrent corneal herpetic disease had more exhausted HSV-specific LAG-3⁺CD8⁺ T cells in both trigeminal ganglia (TG) and cornea. Moreover, a therapeutic blockade of LAG-3 immune checkpoint with antagonist antibodies combined with a therapeutic immunization with gB_498-505 peptide immunodominant epitope of latently infected B6 mice significantly restored the quality and quantity of functional HSV-1 gB_498-505 specific CD8⁺ T cells in both TG and cornea and protected against UV-B induced recurrent corneal herpes infection and disease. In contrast to dysfunctional HSV-specific CD8⁺ T cells from WT B6 mice, more functional HSV-specific CD8⁺ T cells were detected in LAG-3^-/- deficient mice and were associated with less UV-B induced recurrent corneal herpetic disease. Thus, the LAG-3 pathway plays a fundamental role in ocular herpes T cell immunopathology and provides an important immune checkpoint target that can synergizes with T cell-based therapeutic vaccines against symptomatic recurrent ocular herpes.

A trivalent gC2/gD2/gE2 vaccine for herpes simplex virus generates antibody responses that block immune evasion domains on gC2 better than natural infection

Vaccines for prevention and treatment of genital herpes are high public health priorities. Our approach towards vaccine development is to focus on blocking virus entry mediated by herpes simplex virus type 2 (HSV-2) glycoprotein D (gD2) and to prevent the virus from evading complement and antibody attack by blocking the immune evasion domains on HSV-2 glycoproteins C (gC2) and E (gE2), respectively. HSV-2 gC2 and gE2 are expressed on the virion envelope and infected cell surface where they are potential targets of antibodies that bind and block their immune evasion activities. We demonstrate that antibodies produced during natural infection in humans or intravaginal inoculation in guinea pigs bind to gC2 but generally fail to block the immune evasion domains on this glycoprotein. In contrast, immunization of naïve or previously HSV-2-infected guinea pigs with gC2 subunit antigen administered with CpG and alum as adjuvants produces antibodies that block domains involved in immune evasion. These results indicate that immune evasion domains on gC2 are weak antigens during infection, yet when used as vaccine immunogens with adjuvants the antigens produce antibodies that block immune evasion domains.

Phenotypic and Functional Signatures of Herpes Simplex Virus-Specific Effector Memory CD73+CD45RAhighCCR7lowCD8+ TEMRA and CD73+CD45RAlowCCR7lowCD8+ TEM Cells Are Associated with Asymptomatic Ocular Herpes

HSV type 1 (HSV-1)-specific CD8⁺ T cells protect from herpes infection and disease. However, the nature of protective CD8⁺ T cells in HSV-1 seropositive healthy asymptomatic (ASYMP) individuals (with no history of clinical herpes disease) remains to be determined. In this study, we compared the phenotype and function of HSV-specific CD8⁺ T cells from HLA-A*02:01-positive ASYMP and symptomatic (SYMP) individuals (with a documented history of numerous episodes of recurrent ocular herpetic disease). We report that although SYMP and ASYMP individuals have similar frequencies of HSV-specific CD8⁺ T cells, the "naturally" protected ASYMP individuals have a significantly higher proportion of multifunctional HSV-specific effector memory CD8⁺ T cells (CD73⁺CD45RA^highCCR7^lowCD8⁺ effector memory RA (T_EMRA) and CD73⁺CD45RA^lowCCR7^lowCD8⁺ effector memory (T_EM) as compared with SYMP individuals. Similar to humans, HSV-1-infected ASYMP B6 mice had frequent multifunctional HSV-specific CD73⁺CD8⁺ T cells in the cornea, as compared with SYMP mice. Moreover, in contrast to wild type B6, CD73^-/- deficient mice infected ocularly with HSV-1 developed more recurrent corneal herpetic infection and disease. This was associated with less functional CD8⁺ T cells in the cornea and trigeminal ganglia, the sites of acute and latent infection. The phenotypic and functional characteristics of HSV-specific circulating and in situ CD73⁺CD8⁺ T cells, demonstrated in both ASYMP humans and mice, suggest a positive role for effector memory CD8⁺ T cells expressing the CD73 costimulatory molecule in the protection against ocular herpes infection and disease. These findings are important for the development of safe and effective T cell-based herpes immunotherapy.

Preclinical and clinical development of neoantigen vaccines

Cancer neoantigens are antigens that result from somatic mutations present in individual cancers. Neoantigens are considered important targets for cancer immunotherapy because of their immunogenicity and lack of expression in normal tissues. Next-generation sequencing technologies and computational analysis have recently made neoantigen discovery possible. Although neoantigens are important targets of checkpoint blockade therapy, neoantigen vaccines are currently being investigated in preclinical models and early-phase human clinical trials. Preliminary results from these clinical trials demonstrate that dendritic cell, synthetic long peptide, and RNA-based neoantigen vaccines are safe, and capable of inducing both CD8+ and CD4+ neoantigen-specific T-cell responses. We and others are testing neoantigen vaccines in melanoma, breast cancer, non-small-cell lung cancer and other cancer types. Since cancers have evolved mechanisms to escape immune control, it is particularly important to study the efficacy of neoantigen vaccines in combination with other immunotherapies including checkpoint blockade therapy, and immune therapies targeting the immunosuppressive tumor microenvironment.

Prophylactic herpes simplex virus type 2 vaccine adjuvanted with a universal CD4 T cell helper peptide induces long-term protective immunity against lethal challenge in mice

Induction of robust and long-term immune responses at the portal of entry remains a big challenge for HSV-2 vaccine development. The adoption of a CD4 T cell helper peptide in the vaccine is thought to be beneficial for the enhancement of immune responses, however, its effect on HSV-2 vaccines has not yet been studied. In this study, we designed a DNA vaccine (gD-TpD) simultaneously expressing HSV-2 gD ectodomain and a universal CD4 T cell helper peptide (TpD), and tested its efficacy on a murine model. Mice were immunized 3 times with gD-TpD or control DNA formulations, and then were rested until Day 150 when they were vaginally challenged with lethal doses of HSV-2. Our data showed that gD-TpD significantly increased gD-specific IgG and IgA in both sera and vaginal washes. Furthermore, the increased antibody responses showed enhanced neutralization activity in vitro. In addition, gD-TpD induced balanced Th1/2 cellular responses and CD8⁺ T cell-dependent CTL activity. Although immune responses dropped over time after the final immunization, robust and rapid antibody and T cell responses were induced upon virus challenge in gD-TpD group. Moreover, gD-TpD provided full protection against lethal viral challenge in immunized mice. Together, our findings indicate that the inclusion of the CD4 T cell helper peptide TpD in HSV-2 gD subunit vaccine could induce long-term protective immunity, providing information for a rational design of vaccines against HSV-2 or even other viruses.

Updates on the use of vaccines in dermatological conditions

Numerous vaccines are being actively developed for use in dermatologic diseases. Advances in the fields of immunotherapy, genetics and molecular medicine have allowed for the design of prophylactic and therapeutic vaccines with immense potential in managing infections and malignancies of the skin. This review addresses the different vaccines available for use in dermatological diseases and those under development for future potential use. The major limitation of our review is its complete reliance on published data. Our review is strictly limited to the availability of published research online through available databases. We do not cite any of the authors' previous publications nor have we conducted previous original research studies regarding vaccines in dermatology. Strength would have been added to our paper had we conducted original studies by our research team regarding the candidate vaccines delineated in the paper.

Functional failure of TLR3 and its signaling components contribute to herpes simplex encephalitis

Herpes simplex encephalitis (HSE) is a severe neurological disease in children and adults caused by herpes simplex virus. This review discusses recent findings on the role of Toll-like receptor 3 (TLR3) deficiencies in the HSE development. Critical checkpoints in the TLR3 signaling that contribute to innate response are discussed, including the importance of TLR3 ligand recognition site and transportation in the cell. We also indicate unresolved issues in the TLR3 functioning that might lead to thorough understanding of immunity during HSE. Such a knowledge base will lead to discovery and design of a rationale therapeutic and preventive approach against HSE.

Meeting report: Initial World Health Organization consultation on herpes simplex virus (HSV) vaccine preferred product characteristics, March 2017

The development of vaccines against herpes simplex virus (HSV) is an important global goal for sexual and reproductive health. A key priority to advance development of HSV vaccines is the definition of preferred product characteristics (PPCs), which provide strategic guidance on World Health Organization (WHO) preferences for new vaccines, specifically from a low- and middle-income country (LMIC) perspective. To start the PPC process for HSV vaccines, the WHO convened a global stakeholder consultation in March 2017, to define the priority public health needs that should be addressed by HSV vaccines and discuss the key considerations for HSV vaccine PPCs, particularly for LMICs. Meeting participants outlined an initial set of overarching public health goals for HSV vaccines in LMICs, which are: to reduce the acquisition of HIV associated with HSV-2 infection in high HIV-prevalence populations and to reduce the burden of HSV-associated disease, including mortality and morbidity due to neonatal herpes and impacts on sexual and reproductive health. Participants also considered the role of prophylactic versus therapeutic vaccines, whether both HSV-2 and HSV-1 should be targeted, important target populations, and infection and disease endpoints for clinical trials. This article summarizes the main discussions from the consultation.

An escalating dose study to assess the safety, tolerability and immunogenicity of a Herpes Simplex Virus DNA vaccine, COR-1

This paper describes a single site, open-label Phase I clinical trial evaluating the safety, tolerability and immunogenicity in healthy volunteers of a herpes simplex polynucleotide vaccine that has previously been shown to enhance immunogenicity and protect against lethal herpes simplex virus type 2 (HSV-2) challenge in mice. Five escalating doses of the vaccine, COR-1, were given by intradermal injection to HSV-1 and 2 seronegative healthy individuals. COR-1 was found to be safe and well-tolerated; the only vaccine-related adverse events were mild. While vaccine-induced antibody responses were not detectable, cell-mediated immune responses to HSV-specific peptide groups were identified in 19 of the 20 subjects who completed the study, and local inflammation at the immunisation site was observed. This study indicates COR-1 has potential to be used as a therapeutic vaccine for HSV-2 infection.

A Herpes Simplex Virus Type 2 Deleted for Glycoprotein D Enables Dendritic Cells to Activate CD4+ and CD8+ T Cells

Herpes simplex virus type 2 (HSV-2) is highly prevalent in the human population producing significant morbidity, mainly because of the generation of genital ulcers and neonatal encephalitis. Additionally, HSV-2 infection significantly increases the susceptibility of the host to acquire HIV and promotes the shedding of the latter in the coinfected. Despite numerous efforts to create a vaccine against HSV-2, no licensed vaccines are currently available. A long-standing strategy, based on few viral glycoproteins combined with adjuvants, recently displayed poor results in a Phase III clinical study fueling exploration on the development of mutant HSV viruses that are attenuated in vivo and elicit protective adaptive immune components, such as antiviral antibodies and T cells. Importantly, such specialized antiviral immune components are likely induced and modulated by dendritic cells, professional antigen presenting cells that process viral antigens and present them to T cells. However, HSV interferes with several functions of DCs and ultimately induces their death. Here, we propose that for an attenuated mutant virus to confer protective immunity against HSV in vivo based on adaptive immune components, such virus should also be attenuated in dendritic cells to promote a robust and effective antiviral response. We provide a background framework for this idea, considerations, as well as the means to assess this hypothesis. Addressing this hypothesis may provide valuable insights for the development of novel, safe, and effective vaccines against herpes simplex viruses.

Prophylactic Herpes Simplex Virus 2 (HSV-2) Vaccines Adjuvanted with Stable Emulsion and Toll-Like Receptor 9 Agonist Induce a Robust HSV-2-Specific Cell-Mediated Immune Response, Protect against Symptomatic Disease, and Reduce the Latent Viral Reservoir

Several prophylactic vaccines targeting herpes simplex virus 2 (HSV-2) have failed in the clinic to demonstrate sustained depression of viral shedding or protection from recurrences. Although these vaccines have generated high titers of neutralizing antibodies (NAbs), their induction of robust CD8 T cells has largely been unreported, even though evidence for the importance of HSV-2 antigen-specific CD8 T cells is mounting in animal models and in translational studies involving subjects with active HSV-2-specific immune responses. We developed a subunit vaccine composed of the NAb targets gD and gB and the novel T cell antigen and tegument protein UL40, and we compared this vaccine to a whole-inactivated-virus vaccine (formaldehyde-inactivated HSV-2 [FI-HSV-2]). We evaluated different formulations in combination with several Th1-inducing Toll-like receptor (TLR) agonists in vivo In mice, the TLR9 agonist cytosine-phosphate-guanine (CpG) oligodeoxynucleotide formulated in a squalene-based oil-in-water emulsion promoted most robust, functional HSV-2 antigen-specific CD8 T cell responses and high titers of neutralizing antibodies, demonstrating its superiority to vaccines adjuvanted by monophosphoryl lipid A (MPL)-alum. We further established that FI-HSV-2 alone or in combination with adjuvants as well as adjuvanted subunit vaccines were successful in the induction of NAbs and T cell responses in guinea pigs. These immunological responses were coincident with a suppression of vaginal HSV-2 shedding, low lesion scores, and a reduction in latent HSV-2 DNA in dorsal root ganglia to undetectable levels. These data support the further preclinical and clinical development of prophylactic HSV-2 vaccines that contain appropriate antigen and adjuvant components responsible for programming elevated CD8 T cell responses.IMPORTANCE Millions of people worldwide are infected with herpes simplex virus 2 (HSV-2), and to date, an efficacious prophylactic vaccine has not met the rigors of clinical trials. Attempts to develop a vaccine have focused primarily on glycoproteins necessary for HSV-2 entry as target antigens and to which the dominant neutralizing antibody response is directed during natural infection. Individuals with asymptomatic infection have exhibited T cell responses against specific HSV-2 antigens not observed in symptomatic individuals. We describe for the first time the immunogenicity profile in animal models of UL40, a novel HSV-2 T cell antigen that has been correlated with asymptomatic HSV-2 disease. Additionally, vaccine candidates adjuvanted by a robust formulation of the CpG oligonucleotide delivered in emulsion were superior to unadjuvanted or MPL-alum-adjuvanted formulations at eliciting a robust cell-mediated immune response and blocking the establishment of a latent viral reservoir in the guinea pig challenge model of HSV-2 infection.

Therapeutic Vaccine for Genital Herpes Simplex Virus-2 Infection: Findings From a Randomized Trial

Background

Genital herpes simplex virus type 2 (HSV-2) infection causes recurrent lesions and frequent viral shedding. GEN-003 is a candidate therapeutic vaccine containing HSV-2 gD2∆TMR and ICP4.2, and Matrix-M2 adjuvant.

Methods

Persons with genital herpes were randomized into 3 dose cohorts to receive 3 intramuscular doses 21 days apart of 10 µg, 30 µg, or 100 µg of GEN-003, antigens without adjuvant, or placebo. Participants obtained genital swab specimens twice daily for HSV-2 detection and monitored genital lesions for 28-day periods at baseline and at intervals after the last dose.

Results

One hundred and thirty-four persons received all 3 doses. Reactogenicity was associated with adjuvant but not with antigen dose or dose number. No serious adverse events were attributed to GEN-003. Compared with baseline, genital HSV-2 shedding rates immediately after dosing were reduced with GEN-003 (from 13.4% to 6.4% for 30 μg [P < .001] and from 15.0% to 10.3% for 100 µg [P < .001]). Lesion rates were also significantly (P < .01) reduced immediately following immunization with 30 µg or 100 µg of GEN-003. GEN-003 elicited increases in antigen binding, virus neutralizing antibody, and T-cell responses.

Conclusions

GEN-003 had an acceptable safety profile and stimulated humoral and cellular immune responses. GEN-003 at doses of 30 µg and 100 µg reduced genital HSV shedding and lesion rates.

Clinical Trials Registration

NCT01667341 (funded by Genocea).

Human Asymptomatic Epitopes Identified from the Herpes Simplex Virus Tegument Protein VP13/14 (UL47) Preferentially Recall Polyfunctional Effector Memory CD44high CD62Llow CD8+ TEM Cells and Protect Humanized HLA-A*02:01 Transgenic Mice against Ocular Herpesvirus Infection

Herpes simplex virus 1 (HSV-1) infection is widespread among humans. The HSV-1 virion protein 13/14 (VP13/14), also known as UL47, is a tegument antigen targeted by CD8⁺ T cells from HSV-seropositive individuals. However, whether VP13/14-specific CD8⁺ T cells play a role in the natural protection seen in asymptomatic (ASYMP) individuals (individuals who have never had a clinical herpetic disease) has not been elucidated. Using predictive computer-assisted algorithms, we identified 10 potential HLA-A*02:01-restricted CD8⁺ T-cell epitopes from the 693-amino-acid sequence of the VP13/14 protein. Three out of 10 epitopes exhibited a high to moderate affinity of binding to soluble HLA-A*02:01 molecules. The phenotype and function of CD8⁺ T cells specific for each epitope were compared in HLA-A*02:01-positive ASYMP individuals and symptomatic (SYMP) individuals (individuals who have frequent clinical herpetic diseases) using determination of a combination of tetramer frequency and the levels of granzyme B, granzyme K, perforin, gamma interferon, tumor necrosis factor alpha, and interleukin-2 production and CD107^a/b cytotoxic degranulation. High frequencies of multifunctional CD8⁺ T cells directed against three epitopes, VP13/14 from amino acids 286 to 294 (VP13/14_286-294), VP13/14 from amino acids 504 to 512 (VP13/14_504-512), and VP13/14 from amino acids 544 to 552 (VP13/14_544-552), were detected in ASYMP individuals, while only low frequencies were detected in SYMP individuals. The three epitopes also predominantly recalled more CD45RA^low CD44^high CCR7^low CD62L^low CD8⁺ effector memory T cells (T_EM cells) in ASYMP individuals than SYMP individuals. Moreover, immunization of HLA-A*02:01 transgenic mice with the three CD8⁺ T_EM-cell epitopes from ASYMP individuals induced robust and polyfunctional HSV-specific CD8⁺ T_EM cells associated with strong protective immunity against ocular herpesvirus infection and disease. Our findings outline the phenotypic and functional features of protective HSV-specific CD8⁺ T cells that should guide the development of a safe and effective T-cell-based herpes simplex vaccine.

IMPORTANCE

Although most herpes simplex virus 1 (HSV-1)-infected individuals shed the virus in their body fluids following reactivation from latently infected sensory ganglia, the majority never develop a recurrent herpetic disease and remain asymptomatic (ASYMP). In contrast, small proportions of individuals are symptomatic (SYMP) and develop frequent bouts of recurrent disease. The present study demonstrates that naturally protected ASYMP individuals have a higher frequency of effector memory CD8⁺ T cells (CD8⁺ T_EM cells) specific to three epitopes derived from the HSV-1 tegument protein VP13/14 (VP13/14_286-294,VP13/14_504-512, and VP13/14_544-552) than SYMP patients. Moreover, immunization of humanized HLA-A*02:01 transgenic mice with the three CD8⁺ T_EM-cell epitopes from ASYMP individuals induced robust and polyfunctional HSV-specific CD8⁺ T cells associated with strong protective immunity against ocular herpesvirus infection and disease. The findings support the emerging concept of the development of a safe and effective asymptomatic herpes simplex vaccine that is selectively based on CD8⁺ T-cell epitopes from ASYMP individuals.

Identification of Chlamydia trachomatis Antigens Recognized by T Cells From Highly Exposed Women Who Limit or Resist Genital Tract Infection

BACKGROUND

 Natural infection induces partial immunity to Chlamydia trachomatis Identification of chlamydial antigens that induce interferon γ (IFN-) secretion by T cells from immune women could advance vaccine development.

METHODS

 IFN-γ production by CD4⁺ and CD8⁺ peripheral blood T cells from 58 high-risk women was measured after coculture with antigen-presenting cells preincubated with recombinant Escherichia coli expressing a panel of 275 chlamydial antigens. Quantile median regression analysis was used to compare frequencies of IFN-γ responses in women with only cervical infection to those in women with endometrial infection and frequencies in women who remained uninfected for over 1 year to those in women who developed incident infection. Statistical methods were then used to identify proteins associated with protection.

RESULTS

 A higher median frequency of CD8⁺ T-cell responses was detected in women with lower genital tract chlamydial infection, compared with those with upper genital tract chlamydial infection (13.8% vs 9.5%; P =04), but the CD4⁺ T-cell response frequencies were not different. Women who remained uninfected displayed a greater frequency of positive CD4⁺ T-cell responses (29% vs 18%; P < .0001), compared with women who had incident infection, while the frequencies of CD8⁺ T-cell responses did not differ. A subset of proteins involved in central metabolism, type III secretion, and protein synthesis were associated with protection.

CONCLUSIONS

 Investigations in naturally exposed women reveal protective responses and identify chlamydial vaccine candidate antigens.

Immune responses elicited by the GEN-003 candidate HSV-2 therapeutic vaccine in a randomized controlled dose-ranging phase 1/2a trial

PURPOSE

GEN-003 is a candidate therapeutic HSV-2 vaccine containing a fragment of infected cell protein 4 (ICP4.2), a deletion mutant of glycoprotein D2 (gD2ΔTMR), and Matrix-M2 adjuvant. In a dose-ranging phase 1/2a clinical trial, immunization with GEN-003 reduced viral shedding and the percentage of reported herpetic lesion days. Here we examine the immune responses in the same trial, to characterize vaccine-related changes in antibody and cell-mediated immunity.

METHODS

Participants with genital HSV-2 infection were randomized to 1 of 3 doses of GEN-003, antigens without adjuvant, or placebo. Subjects received 3 intramuscular doses, three weeks apart, and were monitored for viral shedding, lesions and immunogenicity. Antibody titers were measured by ELISA and neutralization assay in serum samples collected at baseline and 3weeks post each dose. T cell responses were assessed pre-immunization and 1week post each dose by IFN-γ ELISpot and intracellular cytokine staining. Blood was also collected at 6 and 12months to monitor durability of immune responses.

RESULTS

Antibody and T cell responses increased with vaccination and were potentiated by adjuvant. Among the doses tested, the rank order of reduction in viral shedding follows the ranking of fold change from baseline in T cell responses. Some immune responses persisted up to 12months.

CONCLUSION

All measures of immunity are increased by vaccination with GEN-003; however, a correlate of protection is yet to be defined.

Status of vaccine research and development of vaccines for herpes simplex virus

Herpes simplex virus type-1 (HSV-1) and -2 (HSV-2) are highly prevalent global pathogens which commonly cause recurrent oral and genital ulcerations. Less common but more serious complications include meningitis, encephalitis, neonatal infection, and keratitis. HSV-2 infection is a significant driver of the HIV epidemic, increasing the risk of HIV acquisition 3 fold. As current control strategies for genital HSV-2 infection, including antiviral therapy and condom use, are only partially effective, vaccines will be required to reduce infection. Both preventive and therapeutic vaccines for HSV-2 are being pursued and are in various stages of development. We will provide an overview of efforts to develop HSV-2 vaccines, including a discussion of the clinical need for an HSV vaccine, and status of research and development with an emphasis on recent insights from trials of vaccine candidates in clinical testing. In addition, we will touch upon aspects of HSV vaccine development relevant to low and middle income countries.

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.

Extensive CD4 and CD8 T Cell Cross-Reactivity between Alphaherpesviruses

The Alphaherpesvirinae subfamily includes HSV types 1 and 2 and the sequence-divergent pathogen varicella zoster virus (VZV). T cells, controlled by TCR and HLA molecules that tolerate limited epitope amino acid variation, might cross-react between these microbes. We show that memory PBMC expansion with either HSV or VZV enriches for CD4 T cell lines that recognize the other agent at the whole-virus, protein, and peptide levels, consistent with bidirectional cross-reactivity. HSV-specific CD4 T cells recovered from HSV-seronegative persons can be explained, in part, by such VZV cross-reactivity. HSV-1-reactive CD8 T cells also cross-react with VZV-infected cells, full-length VZV proteins, and VZV peptides, as well as kill VZV-infected dermal fibroblasts. Mono- and cross-reactive CD8 T cells use distinct TCRB CDR3 sequences. Cross-reactivity to VZV is reconstituted by cloning and expressing TCRA/TCRB receptors from T cells that are initially isolated using HSV reagents. Overall, we define 13 novel CD4 and CD8 HSV-VZV cross-reactive epitopes and strongly imply additional cross-reactive peptide sets. Viral proteins can harbor both CD4 and CD8 HSV/VZV cross-reactive epitopes. Quantitative estimates of HSV/VZV cross-reactivity for both CD4 and CD8 T cells vary from 10 to 50%. Based on these findings, we hypothesize that host herpesvirus immune history may influence the pathogenesis and clinical outcome of subsequent infections or vaccinations for related pathogens and that cross-reactive epitopes and TCRs may be useful for multi-alphaherpesvirus vaccine design and adoptive cellular therapy.

Resolution of Chlamydia trachomatis Infection Is Associated with a Distinct T Cell Response Profile

Chlamydia trachomatis is the causative agent of the most frequently reported bacterial sexually transmitted infection, the total burden of which is underestimated due to the asymptomatic nature of the infection. Untreated C. trachomatis infections can cause significant morbidities, including pelvic inflammatory disease and tubal factor infertility (TFI). The human immune response against C. trachomatis, an obligate intracellular bacterium, is poorly characterized but is thought to rely on cell-mediated immunity, with CD4(+) and CD8(+) T cells implicated in protection. In this report, we present immune profiling data of subjects enrolled in a multicenter study of C. trachomatis genital infection. CD4(+) and CD8(+) T cells from subjects grouped into disease-specific cohorts were screened using a C. trachomatis proteomic library to identify the antigen specificities of recall T cell responses after natural exposure by measuring interferon gamma (IFN-γ) levels. We identified specific T cell responses associated with the resolution of infection, including unique antigens identified in subjects who spontaneously cleared infection and different antigens associated with C. trachomatis-related sequelae, such as TFI. These data suggest that novel and unique C. trachomatis T cell antigens identified in individuals with effective immune responses can be considered as targets for vaccine development, and by excluding antigens associated with deleterious sequelae, immune-mediated pathologies may be circumvented.

Large screen approaches to identify novel malaria vaccine candidates

Until recently, malaria vaccine development efforts have focused almost exclusively on a handful of well characterized Plasmodium falciparum antigens. Despite dedicated work by many researchers on different continents spanning more than half a century, a successful malaria vaccine remains elusive. Sequencing of the P. falciparum genome has revealed more than five thousand genes, providing the foundation for systematic approaches to discover candidate vaccine antigens. We are taking advantage of this wealth of information to discover new antigens that may be more effective vaccine targets. Herein, we describe different approaches to large-scale screening of the P. falciparum genome to identify targets of either antibody responses or T cell responses using human specimens collected in Controlled Human Malaria Infections (CHMI) or under conditions of natural exposure in the field. These genome, proteome and transcriptome based approaches offer enormous potential for the development of an efficacious malaria vaccine.

Malaria vaccines: identifying Plasmodium falciparum liver-stage targets

The development of a highly efficacious and durable vaccine for malaria remains a top priority for global health researchers. Despite the huge rise in recognition of malaria as a global health problem and the concurrent rise in funding over the past 10–15 years, malaria continues to remain a widespread burden. The evidence of increasing resistance to anti-malarial drugs and insecticides is a growing concern. Hence, an efficacious and durable preventative vaccine for malaria is urgently needed. Vaccines are one of the most cost-effective tools and have successfully been used in the prevention and control of many diseases, however, the development of a vaccine for the Plasmodium parasite has proved difficult. Given the early success of whole sporozoite mosquito-bite delivered vaccination strategies, we know that a vaccine for malaria is an achievable goal, with sub-unit vaccines holding great promise as they are simple and cheap to both manufacture and deploy. However a major difficulty in development of sub-unit vaccines lies within choosing the appropriate antigenic target from the 5000 or so genes expressed by the parasite. Given the liver-stage of malaria represents a bottle-neck in the parasite’s life cycle, there is widespread agreement that a multi-component sub-unit malaria vaccine should preferably contain a liver-stage target. In this article we review progress in identifying and screening Plasmodium falciparum liver-stage targets for use in a malaria vaccine.

Global Diversity within and between Human Herpesvirus 1 and 2 Glycoproteins

Human herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) are large-genome DNA viruses that establish a persistent infection in sensory neurons and commonly manifest with recurring oral or genital erosions that transmit virus. HSV encodes 12 predicted glycoproteins that serve various functions, including cellular attachment, entry, and egress. Glycoprotein G is currently the target of an antibody test to differentiate HSV-1 from HSV-2; however, this test has shown reduced capacity to differentiate HSV strains in East Africa. Until the recent availability of 26 full-length HSV-1 and 36 full-length HSV-2 sequences, minimal comparative information was available for these viruses. In this study, we use a variety of sequence analysis methods to compare all available sequence data for HSV-1 and HSV-2 glycoproteins, using viruses isolated in Europe, Asia, North America, the Republic of South Africa, and East Africa. We found numerous differences in diversity, nonsynonymous/synonymous substitution rates, and recombination rates between HSV-1 glycoproteins and their HSV-2 counterparts. Phylogenetic analysis revealed that while most global HSV-2 glycoprotein G sequences did not form clusters within or between continents, one clade (supported at 60.5%) contained 37% of the African sequences analyzed. Accordingly, sequences from this African subset contained unique amino acid signatures, not only in glycoprotein G, but also in glycoproteins I and E, which may account for the failure of sensitive antibody tests to distinguish HSV-1 from HSV-2 in some African individuals. Consensus sequences generated in the study can be used to improve diagnostic assays that differentiate HSV-1 from HSV-2 in global populations.

IMPORTANCE

Human herpes simplex viruses 1 and 2 (HSV-1 and HSV-2) are large DNA viruses associated with recurring oral or genital erosions that transmit virus. Up to 12 HSV-1 and HSV-2 glycoproteins are involved in HSV cell entry or are required for viral spread in animals, albeit some are dispensable for replication in vitro. The recent availability of comparable numbers of full-length HSV-1 and HSV-2 sequences enabled comparative analysis of gene diversity of glycoproteins within and between HSV types. Overall, we found less glycoprotein sequence diversity within HSV-2 than within the HSV-1 strains studied, while at the same time, several HSV-2 glycoproteins were evolving under less selective pressure. Because HSV glycoproteins are the focus of antibody tests to detect and differentiate between infections with the two strains and are constituents of vaccines in clinical-stage development, these findings will aid in refining the targets for diagnostic tests and vaccines.

Discordant humoral and cellular immune responses to Cytomegalovirus (CMV) in glioblastoma patients whose tumors are positive for CMV

Background. Glioblastoma (GBM) is the most common malignant brain tumor in adults and is nearly always fatal. Emerging evidence suggests that human Cytomegalovirus (HCMV) is present in 90-100% of GBMs and that add-on antiviral treatment for HCMV show promise to improve survival. Methods. In a randomized, placebo-controlled trial of valganciclovir in 42 GBM patients, blood samples were collected for analyses of HCMV DNA, RNA, reactivity against HCMV peptides, IgG, and IgM at baseline and at 3, 12, and 24 weeks of treatment. Results. All 42 tumors were positive for HCMV protein. All patients examined had at least one blood sample positive for HCMV DNA, 63% were HCMV RNA positive, and 21% were IgM positive. However, 29% of GBM patients were IgG negative for HCMV. Five of these samples were positive in an enzyme-linked immunosorbent assay (ELISA) that used antigens derived from a clinical isolate. Blood T cells from 11 of 13 (85%) HCMV IgG-negative GBM patients reacted against HCMV peptides. Valganciclovir did not affect IgG titers, DNA, or RNA levels of the HCMV immediate early (HCMV IE) gene in blood. Conclusion. In GBM patients, HCMV activity is higher than in healthy controls and serology is a poor test to define previous or active HCMV infection in these patients.

HLA-A02:01-restricted epitopes identified from the herpes simplex virus tegument protein VP11/12 preferentially recall polyfunctional effector memory CD8+ T cells from seropositive asymptomatic individuals and protect humanized HLA-A*02:01 transgenic mice against ocular herpes

The HSV type 1 tegument virion phosphoprotein (VP) 11/12 (VP11/12) is a major Ag targeted by CD8(+) T cells from HSV-seropositive individuals. However, whether and which VP11/12 epitope-specific CD8(+) T cells play a role in the "natural" protection seen in seropositive healthy asymptomatic (ASYMP) individuals (who have never had clinical herpes disease) remain to be determined. In this study, we used multiple prediction computer-assisted algorithms to identify 10 potential HLA-A*02:01-restricted CD8(+) T cell epitopes from the 718-aa sequence of VP11/12. Three of 10 epitopes exhibited high-to-moderate binding affinity to HLA-A*02:01 molecules. In 10 sequentially studied HLA-A*02:01-positive and HSV-1-seropositive ASYMP individuals, the most frequent, robust, and polyfunctional effector CD8(+) T cell responses, as assessed by a combination of tetramer frequency, granzyme B, granzyme K, perforin, CD107(a/b) cytotoxic degranulation, IFN-γ, and multiplex cytokines assays, were predominantly directed against three epitopes: VP11/1266-74, VP11/12220-228, and VP11/12702-710. Interestingly, ASYMP individuals had a significantly higher proportion of CD45RA(low)CCR7(low)CD44(high)CD62L(low)CD27(low)CD28(low)CD8(+) effector memory CD8(+) T cells (TEMs) specific to the three epitopes, compared with symptomatic individuals (with a history of numerous episodes of recurrent ocular herpetic disease). Moreover, immunization of HLA-A*02:01 transgenic mice with the three ASYMP CD8(+) TEM cell epitopes induced robust and polyfunctional epitope-specific CD8(+) TEM cells that were associated with a strong protective immunity against ocular herpes infection and disease. Our findings outline phenotypic and functional features of protective HSV-specific CD8(+) T cells that should guide the development of an effective T cell-based herpes vaccine.