Effector CD4+ T-cell involvement in clearance of infectious herpes simplex virus type 1 from sensory ganglia and spinal cords

Viral T-cell epitopes - Identification, characterization and clinical application

T-cell immunity, mediated by CD4⁺ and CD8⁺ T cells, represents a cornerstone in the control of viral infections. Virus-derived T-cell epitopes are represented by human leukocyte antigen (HLA)-presented viral peptides on the surface of virus-infected cells. They are the prerequisite for the recognition of infected cells by T cells. Knowledge of viral T-cell epitopes provides on the one hand a diagnostic tool to decipher protective T-cell immune responses in the human population and on the other hand various prophylactic and therapeutic options including vaccination approaches and the transfer of virus-specific T cells. Such approaches have already been proven to be effective against various viral infections, particularly in immunocompromised patients lacking sufficient humoral, antibody-based immune response. This review provides an overview on the state of the art as well as current studies regarding the identification and characterization of viral T-cell epitopes and approaches of clinical application. In the first chapter in silico prediction tools and direct, mass spectrometry-based identification of viral T-cell epitopes is compared. The second chapter provides an overview of commonly used assays for further characterization of T-cell responses and phenotypes. The final chapter presents an overview of clinical application of viral T-cell epitopes with a focus on human immunodeficiency virus (HIV), human cytomegalovirus (HCMV) and severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), being representatives of relevant viruses.

The Dilemma of HSV-1 Oncolytic Virus Delivery: The Method Choice and Hurdles

Oncolytic viruses (OVs) have emerged as effective gene therapy and immunotherapy drugs. As an important gene delivery platform, the integration of exogenous genes into OVs has become a novel path for the advancement of OV therapy, while the herpes simplex virus type 1 (HSV-1) is the most commonly used. However, the current mode of administration of HSV-1 oncolytic virus is mainly based on the tumor in situ injection, which limits the application of such OV drugs to a certain extent. Intravenous administration offers a solution to the systemic distribution of OV drugs but is ambiguous in terms of efficacy and safety. The main reason is the synergistic role of innate and adaptive immunity of the immune system in the response against the HSV-1 oncolytic virus, which is rapidly cleared by the body's immune system before it reaches the tumor, a process that is accompanied by side effects. This article reviews different administration methods of HSV-1 oncolytic virus in the process of tumor treatment, especially the research progress in intravenous administration. It also discusses immune constraints and solutions of intravenous administration with the intent to provide new insights into HSV-1 delivery for OV therapy.

Crosstalk Between Epithelial Cells, Neurons and Immune Mediators in HSV-1 Skin Infection

Herpes simplex virus type 1 (HSV-1) infection is highly prevalent in humans, with approximately two-thirds of the world population living with this virus. However, only a fraction of those carrying HSV-1, which elicits lifelong infections, are symptomatic. HSV-1 mainly causes lesions in the skin and mucosae but reaches the termini of sensory neurons innervating these tissues and travels in a retrograde manner to the neuron cell body where it establishes persistent infection and remains in a latent state until reactivated by different stimuli. When productive reactivations occur, the virus travels back along axons to the primary infection site, where new rounds of replication are initiated in the skin, in recurrent or secondary infections. During this process, new neuron infections occur. Noteworthy, the mechanisms underlying viral reactivations and the exit of latency are somewhat poorly understood and may be regulated by a crosstalk between the infected neurons and components of the immune system. Here, we review and discuss the immune responses that occur at the skin during primary and recurrent infections by HSV-1, as well as at the interphase of latently-infected neurons. Moreover, we discuss the implications of neuronal signals over the priming and migration of immune cells in the context of HSV-1 infection.

Detection of multiple viruses in oropharyngeal samples from Brazilian free-tailed bats (Tadarida brasiliensis) using viral metagenomics

In this study, we analyzed the viral population in oropharyngeal samples from T. brasiliensis using a viral metagenomic approach. Genomes corresponding to members of the families Circoviridae, Genomoviridae, Herpesviridae, Paramyxoviridae, Coronaviridae, and Astroviridae were detected. This study provides the first preliminary understanding of the oropharyngeal virome of T. brasiliensis, which may guide the discovery and isolation of novel viruses in the future and highlights the need for continuing investigations in this regard.

Utilization of Galectins by Pathogens for Infection

Galectins are glycan-binding proteins which are expressed by many different cell types and secreted extracellularly. These molecules are well-known regulators of immune responses and involved in a broad range of cellular and pathophysiological functions. During infections, host galectins can either avoid or facilitate infections by interacting with host cells- and/or pathogen-derived glycoconjugates and less commonly, with proteins. Some pathogens also express self-produced galectins to interfere with host immune responses. This review summarizes pathogens which take advantage of host- or pathogen-produced galectins to establish the infection.

Upregulation of Multiple CD8+ T Cell Exhaustion Pathways Is Associated with Recurrent Ocular Herpes Simplex Virus Type 1 Infection

A large proportion of the world's population harbors latent HSV type 1 (HSV-1). Cross-talk between antiviral CD8⁺ T cells and HSV-1 appear to control latency/reactivation cycles. We found that compared with healthy asymptomatic individuals, in symptomatic (SYMP) patients, the CD8⁺ T cells with the same HLA-A*0201-restricted HSV-1 epitope specificities expressed multiple genes and proteins associated to major T cell exhaustion pathways and were dysfunctional. Blockade of immune checkpoints with anti-LAG-3 and anti-PD-1 antagonist mAbs synergistically restored the frequency and function of antiviral CD8⁺ T cells, both 1) ex vivo, in SYMP individuals and SYMP HLA-A*0201 transgenic mice; and 2) in vivo in HSV-1-infected SYMP HLA-A*0201 transgenic mice. This was associated with a significant reduction in virus reactivation and recurrent ocular herpetic disease. These findings confirm antiviral CD8⁺ T cell exhaustion during SYMP herpes infection and pave the way to targeting immune checkpoints to combat recurrent ocular herpes.

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.

Intramuscular vaccination of mice with the human herpes simplex virus type-1(HSV-1) VC2 vaccine, but not its parental strain HSV-1(F) confers full protection against lethal ocular HSV-1 (McKrae) pathogenesis

Herpes simplex virus type-1 (HSV-1) can cause severe ocular infection and blindness. We have previously shown that the HSV-1 VC2 vaccine strain is protective in mice and guinea pigs against genital herpes infection following vaginal challenge with HSV-1 or HSV-2. In this study, we evaluated the efficacy of VC2 intramuscular vaccination in mice against herpetic keratitis following ocular challenge with lethal human clinical strain HSV-1(McKrae). VC2 vaccination in mice produced superior protection and morbidity control in comparison to its parental strain HSV-1(F). Specifically, after HSV-1(McKrae) ocular challenge, all VC2 vaccinated- mice survived, while 30% of the HSV-1(F)- vaccinated and 100% of the mock-vaccinated mice died post challenge. VC2-vaccinated mice did not exhibit any symptoms of ocular infection and completely recovered from initial conjunctivitis. In contrast, HSV-1(F)-vaccinated mice developed time-dependent progressive keratitis characterized by corneal opacification, while mock-vaccinated animals exhibited more severe stromal keratitis characterized by immune cell infiltration and neovascularization in corneal stroma with corneal opacification. Cornea in VC2-immunized mice exhibited significantly increased infiltration of CD3⁺ T lymphocytes and decreased infiltration of Iba1+ macrophages in comparison to mock- or HSV-1(F)-vaccinated groups. VC2 immunization produced higher virus neutralization titers than HSV-1(F) post challenge. Furthermore, VC-vaccination significantly increased the CD4 T central memory (TCM) subsets and CD8 T effector memory (TEM) subsets in the draining lymph nodes following ocular HSV-1 (McKrae) challenge, then mock- or HSV-1(F)-vaccination. These results indicate that VC2 vaccination produces a protective immune response at the site of challenge to protect against HSV-1-induced ocular pathogenesis.

Herpes Simplex Virus Type 1 and Host Antiviral Immune Responses: An Update

Herpes simplex virus type 1 (HSV-1) infection activates a rapid stimulation of host innate immune responses and a delicate interplay between virus and host immune elements regulates the whole events. Although host immune elements play well in limiting the HSV-1 infection by interfering viral replication, they are still unable to remove the virus completely, because HSV-1 proteins are efficient enough to bypass the host antiviral immune responses and virus succeed to reactivate again from latency at opportune time. Type 1 interferon signaling pathway is the central point of innate immunity along with some of the activated neutrophils, monocytes, macrophages, and dendritic cells, and some natural killer cells play role, while the CD8⁺ T cells are crucial in adaptive immunity. In this review, the current knowledge of host and HSV-1 interaction has been described that how the host antiviral immune responses occur and what are the mechanisms of viral evasion adapted by virus to counteract with both arms of immunity.

Generation of IL-3-Secreting CD4+ T Cells by Microbial Challenge at Skin and Mucosal Barriers

During Ag priming, naive CD4⁺ T cells differentiate into subsets with distinct patterns of cytokine expression that dictate to a major extent their functional roles in immune responses. We identified a subset of CD4⁺ T cells defined by secretion of IL-3 that was induced by Ag stimulation under conditions different from those associated with previously defined functional subsets. Using mouse models of bacterial and viral infections, we showed that IL-3–secreting CD4⁺ T cells were generated by infection at the skin and mucosa but not by infections introduced directly into the blood. Most IL-3–producing T cells coexpressed GM-CSF and other cytokines that define multifunctionality. Generation of IL-3–secreting T cells in vitro was dependent on IL-1 family cytokines and was inhibited by cytokines that induce canonical Th1 or Th2 cells. Our results identify IL-3–secreting CD4⁺ T cells as a potential functional subset that arises during priming of naive T cells in specific tissue locations.

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.

Fas activity mediates airway inflammation during mouse adenovirus type 1 respiratory infection

CD8 T cells play a key role in clearance of mouse adenovirus type 1 (MAV-1) from the lung and contribute to virus-induced airway inflammation. We tested the hypothesis that interactions between Fas ligand (FasL) and Fas mediate the antiviral and proinflammatory effects of CD8 T cells. FasL and Fas expression were increased in the lungs of C57BL/6 (B6) mice during MAV-1 respiratory infection. Viral replication and weight loss were similar in B6 and Fas-deficient (lpr) mice. Histological evidence of pulmonary inflammation was similar in B6 and lpr mice, but lung mRNA levels and airway proinflammatory cytokine concentrations were lower in MAV-1-infected lpr mice compared to infected B6 mice. Virus-induced apoptosis in lungs was not affected by Fas deficiency. Our results suggest that the proinflammatory effects of CD8 T cells during MAV-1 infection are mediated in part by Fas activation and are distinct from CD8 T cell antiviral functions.

Effects of spatiotemporal HSV-2 lesion dynamics and antiviral treatment on the risk of HIV-1 acquisition

Patients with Herpes Simplex Virus-2 (HSV-2) infection face a significantly higher risk of contracting HIV-1. This is thought to be due to herpetic lesions serving as entry points for HIV-1 and tissue-resident CD4+ T cell counts increasing during HSV-2 lesional events. We have created a stochastic and spatial mathematical model describing the dynamics of HSV-2 infection and immune response in the genital mucosa. Using our model, we first study the dynamics of a developing HSV-2 lesion. We then use our model to quantify the risk of infection with HIV-1 following sexual exposure in HSV-2 positive women. Untreated, we find that HSV-2 infected women are up to 8.6 times more likely to acquire HIV-1 than healthy patients. However, when including the effects of the HSV-2 antiviral drug, pritelivir, the risk of HIV-1 infection is predicted to decrease by up to 35%, depending on drug dosage. We estimate the relative importance of decreased tissue damage versus decreased CD4+ cell presence in determining the effectiveness of pritelivir in reducing HIV-1 infection. Our results suggest that clinical trials should be performed to evaluate the effectiveness of pritelivir or similar agents in preventing HIV-1 infection in HSV-2 positive women.

The risk of contracting HIV-1 is significantly higher in people who have genital HSV-2 infections. Here, we put forward a new mathematical model to describe HSV-2 infection and the process of HIV-1 infection in the genital mucosa surrounding HSV-2 lesions. We determine how the characteristics of HSV-2 infection affect the risk of HIV-1 infection, and determine whether reducing the severity of HSV-2 symptoms with antiviral drugs can be expected to decrease the risk of HIV-1 infection. We find that the risk of HIV-1 infection is dependent on three factors: the amount of HIV-1 the patient is exposed to, the severity of HSV-2 lesions, and the number of CD4+ T immune cells in the genital mucosa. Our model predicts that antiviral drugs targeting HSV-2 can cause a therapeutic decrease in lesion severity and CD4+ T cell count in the genital mucosa. This furthermore causes a significant decrease in the risk of HIV-1 infection but the dose of HSV-2 antiviral drug must be sufficiently high. Our results support further development and testing of new HSV-2 antiviral drugs to help decrease the world-wide burden of HIV-1.

Intramuscular vaccination of guinea pigs with the live-attenuated human herpes simplex vaccine VC2 stimulates a transcriptional profile of vaginal Th17 and regulatory Tr1 responses

Herpes simplex virus is a common causative agent of oral and genital diseases. Novel vaccines and therapeutics are needed to combat herpes infections especially after the failure of subunit vaccines in human clinical trials. We have shown that the live-attenuated HSV-1 VC2 vaccine strain is unable to establish latency in vaccinated animals and produces a robust immune response capable of completely protecting mice against lethal vaginal HSV-1 or HSV-2 infections. The guinea pig represents the best small animal model of genital HSV-2 disease. Reported here, twenty-one female Hartley guinea pigs received intramuscular injection with either the VC2 vaccine, or equal volume of conditioned tissue culture media. Animals received 2 booster vaccinations at 21 day intervals following the initial vaccination. After vaccination, animals were challenged with the highly virulent HSV-2 (G) strain. Histologically, VC2 vaccinated animals had little to no apparent inflammation/disease following challenge. Unvaccinated animals developed moderate to severe erosive and ulcerative vaginitis. Quantitative reverse-transcriptase PCR analysis in VC2 vaccinated and challenged animals identified transcriptional signatures of Th17 and regulatory Tr1 cells associated with the inflammatory response primed by VC2 vaccination. Treatment of cultured human vaginal epithelial cells (VK2 cells) with a combination of IL-17A and IL-22 resulted in the significant induction of beta-defensin 3 expression. Further, treatment of VK2 cells with IL-17A, IL-22, IL-36 or beta-defensin 3 resulted in diminished HSV-2 replication. Overall, these results suggest that intramuscular vaccination with the live-attenuated vaccine VC2 primes a mucosal immune response predisposing the adaptive expression of transcripts associated with a Th17 response to challenge and these responses contribute to antiviral immunity.

Immune response of T cells during herpes simplex virus type 1 (HSV-1) infection

Herpes simplex virus type 1 (HSV-1), a neurotropic member of the alphaherpes virus family, is among the most prevalent and successful human pathogens. HSV-1 can cause serious diseases at every stage of life including fatal disseminated disease in newborns, cold sores, eye disease, and fatal encephalitis in adults. HSV-1 infection can trigger rapid immune responses, and efficient inhibition and clearance of HSV-1 infection rely on both the innate and adaptive immune responses of the host. Multiple strategies have been used to restrict host innate immune responses by HSV-1 to facilitate its infection in host cells. The adaptive immunity of the host plays an important role in inhibiting HSV-1 infections. The activation and regulation of T cells are the important aspects of the adaptive immunity. They play a crucial role in host-mediated immunity and are important for clearing HSV-1. In this review, we examine the findings on T cell immune responses during HSV-1 infection, which hold promise in the design of new vaccine candidates for HSV-1.

Dendritic cells, macrophages, NK and CD8+ T lymphocytes play pivotal roles in controlling HSV-1 in the trigeminal ganglia by producing IL1-beta, iNOS and granzyme B

Background

Herpes simplex virus type 1 (HSV-1) cause not only mild symptoms but also blindness and encephalitis. It was previously shown that the immune response against HSV-1 occurs mainly in the trigeminal ganglia (TG) and that Toll-like receptors 2 and 9 (TLR2/9) are important in mediating this response. It was also demonstrated that iNOS (nitric oxide synthase) and interleukin 1 beta (IL-1β) play an essential role in the defense against HSV-1 infection. Importantly, the present work aimed to identify the primary cells responsible for iNOS and IL-1β production and search for other important molecules and cells that might or might not depend on TLR2/9 receptors to mediate the immune response against HSV-1.

Methods

C57BL/6 (wild type, WT) and TLR2/9^−/− mice were infected by the intranasal route with HSV-1 (1 × 10⁶ p.f.u.). Cells were obtained from the TG and spleen tissues and the profile of immune cells was determined by flow cytometry in infected and mock infected WT and knockout mice. The percentage of cells producing iNOS, IL-1β, granzyme B and perforin was also determined by flow cytometry. Chemokine monocyte chemoattractant protein-1 (MCP1) was measured by Cytometric Bead Array (CBA) in the TG, spleen and lung. Expression of type I interferons (IFNs), interleukins (IL) 5 and 10, IL-1β and granzyme B were quantified by real time PCR.

Results

The results indicate that dendritic cells (DCs) and monocytes/macrophages (Mo/Mϕ) were the main sources of IL-1β and iNOS, respectively, which, together with type I IFNs, were essential for the immune response against HSV-1. Additionally, we showed that granzyme B produced by CD8⁺ T and NK lymphocytes and MCP-1 were also important for this immune response. Moreover, our data indicate that the robust production of MCP-1 and granzyme B is either TLR-independent or down regulated by TLRs and occurs in the TG of TLR2/9^−/− infected mice.

Conclusion

Taken together, our data provide strong evidence that the responses mediated by DCs, Mo/Mϕ, NK and CD8⁺ T lymphocytes through IL-1β, iNOS and granzyme B production, respectively, together with the production of type I IFN early in the infection, are crucial to host defense against HSV-1.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-017-0692-x) contains supplementary material, which is available to authorized users.

Viral Spread to Enteric Neurons Links Genital HSV-1 Infection to Toxic Megacolon and Lethality

Herpes simplex virus 1 (HSV-1), a leading cause of genital herpes, infects oral or genital mucosal epithelial cells before infecting the peripheral sensory nervous system. The spread of HSV-1 beyond the sensory nervous system and the resulting broader spectrum of disease are not well understood. Using a mouse model of genital herpes, we found that HSV-1-infection-associated lethality correlated with severe fecal and urinary retention. No inflammation or infection of the brain was evident. Instead, HSV-1 spread via the dorsal root ganglia to the autonomic ganglia of the enteric nervous system (ENS) in the colon. ENS infection led to robust viral gene transcription, pathological inflammatory responses, and neutrophil-mediated destruction of enteric neurons, ultimately resulting in permanent loss of peristalsis and the development of toxic megacolon. Laxative treatment rescued mice from lethality following genital HSV-1 infection. These results reveal an unexpected pathogenesis of HSV associated with ENS infection.

Access of protective antiviral antibody to neuronal tissues requires CD4 T-cell help

Circulating antibodies can access most tissues to mediate surveillance and elimination of invading pathogens. Immunopriviledged tissues such as the brain and the peripheral nervous system, are shielded from plasma proteins, by the blood-brain barrier¹ and blood nerve barrier², respectively. Yet, circulating antibodies must somehow gain access to these tissues in order to mediate their antimicrobial functions. Here, we examine the mechanism by which antibodies gain access to neuronal tissues to control infection. Using mouse model of genital herpes infection, we demonstrate that both antibodies and CD4 T cells are required to protect the host following immunization at a distal site. We show that memory CD4 T cells migrate to the dorsal root ganglia (DRG) and spinal cord in response to HSV-2 infection. Once inside these neuronal tissues, CD4 T cells secrete interferon (IFN)-γ and mediate local increase in vascular permeability, enabling antibody access for viral control. A similar requirement for CD4 T cells for antibody access to the brain was observed following intranasal challenge with vesicular stomatitis virus. Our results reveal a previously unappreciated role of CD4 help in mobilizing antibodies to the peripheral sites of infection where they help to limit viral spread.

A lack of Fas/FasL signalling leads to disturbances in the antiviral response during ectromelia virus infection

Ectromelia virus (ECTV) is an orthopoxvirus (OPV) that causes mousepox, the murine equivalent of human smallpox. Fas receptor-Fas ligand (FasL) signaling is involved in apoptosis of immune cells and virus-specific cytotoxicity. The Fas/FasL pathway also plays an important role in controlling the local inflammatory response during ECTV infection. Here, the immune response to the ECTV Moscow strain was examined in Fas (-) (lpr), FasL (-) (gld) and C57BL6 wild-type mice. During ECTV-MOS infection, Fas- and FasL mice showed increased viral titers, decreased total numbers of NK cells, CD4(+) and CD8(+) T cells followed by decreased percentages of IFN-γ expressing NK cells, CD4(+) and CD8(+) T cells in spleens and lymph nodes. At day 7 of ECTV-MOS infection, Fas- and FasL-deficient mice had the highest regulatory T cell (Treg) counts in spleen and lymph nodes in contrast to wild-type mice. Furthermore, at days 7 and 10 of the infection, we observed significantly higher numbers of PD-L1-expressing dendritic cells in Fas (-) and FasL (-) mice in comparison to wild-type mice. Experiments in co-cultures of CD4(+) T cells and bone-marrow-derived dendritic cells showed that the lack of bilateral Fas-FasL signalling led to expansion of Tregs. In conclusion, our results demonstrate that during ECTV infection, Fas/FasL can regulate development of tolerogenic DCs and Tregs, leading to an ineffective immune response.

Dendritic Cell Autophagy Contributes to Herpes Simplex Virus-Driven Stromal Keratitis and Immunopathology

Herpetic stromal keratitis (HSK) is a blinding ocular disease that is initiated by HSV-1 and characterized by chronic inflammation in the cornea. Although HSK immunopathology of the cornea is well documented in animal models, events preceding this abnormal inflammatory cascade are poorly understood. In this study, we have examined the activation of pathological CD4⁺ T cells in the development of HSK. Dendritic cell autophagy (DC-autophagy) is an important pathway regulating major histocompatibility complex class II (MHCII)-dependent antigen presentation and proper CD4⁺ T cell activation during infectious diseases. Using DC-autophagy-deficient mice, we found that DC-autophagy significantly and specifically contributes to HSK disease without impacting early innate immune infiltration, viral clearance, or host survival. Instead, the observed phenotype was attributable to the abrogated activation of CD4⁺ T cells and reduced inflammation in HSK lesions. We conclude that DC-autophagy is an important contributor to primary HSK immunopathology upstream of CD4⁺ T cell activation.

Herpetic stromal keratitis (HSK) is the leading cause of infectious blindness in the United States and a rising cause worldwide. HSK is induced by herpes simplex virus 1 but is considered a disease of inappropriately sustained inflammation driven by CD4⁺ T cells. In this study, we investigated whether pathways preceding CD4⁺ T cell activation affect disease outcome. We found that autophagy in dendritic cells significantly contributed to the incidence of HSK. Dendritic cell autophagy did not alter immune control of the virus or neurological disease but specifically augmented CD4⁺ T cell activation and pathological corneal inflammation. This study broadens our understanding of the immunopathology that drives HSK and implicates the autophagy pathway as a new target for therapeutic intervention against this incurable form of infectious blindness.

Adverse effects of low-dose systemic cyclosporine therapy in high-risk penetrating keratoplasty

PURPOSE

The purpose of this study was to investigate the adverse effects of low-dose oral cyclosporine (CsA) therapy following high-risk corneal transplantation.

METHODS

The medical records from 88 subjects who had undergone high-risk penetrating keratoplasties and had been administered oral CsA were retrospectively analyzed. High risk was defined as a history of graft rejection, three or more quadrants of vascularization, or the presence or history of intraocular inflammation. An initial CsA dose of 3-5 mg/kg per day was given for 3-7 days, followed by 2.5-3.5 mg/kg per day for approximately 1 month. The concentration of CsA was maintained at the target trough level of 120-150 ng/ml for at least 6 months or until serious complications developed. The relationship between the cumulative dose and duration of CsA administration and the adverse systemic effects, including the frequency of herpes keratitis, was evaluated. The incidence of herpes keratitis in the study subjects was compared with the incidence in 185 patients who had not received CsA therapy following penetrating keratoplasty.

RESULTS

The mean survival time of the grafts was 33.6 months. Adverse effects occurred in 81.8 % of subjects. Hypertension, elevated liver enzyme levels, elevated serum creatinine level, and decreased absolute neutrophil count (ANC) were observed in 14.8, 6.8, 5.7, and 5.7 % of subjects, respectively. Simvastatin-induced rhabdomyolysis also developed in one case. Some patients exhibited minor complications, with gastrointestinal problems and hypertrichosis recorded in 5.7 and 3.4 % of subjects, respectively. Hypertension and hepatotoxicity most frequently occurred after 4 to 8 weeks of medication, while ANC decrease and nephrotoxicity generally developed after 24 weeks of treatment, with incidence related to the cumulative dose. Herpes keratitis occurred more frequently (31.8 %) in the CsA-treated subjects than in subjects that did not receive CsA therapy (p = 0.005). Most of the adverse effects were reversed after discontinuation of CsA therapy.

CONCLUSION

The results of this study suggest that low-dose oral CsA therapy may induce various adverse effects, the most common of which are herpes keratitis and hypertension.

Fas/FasL pathway participates in regulation of antiviral and inflammatory response during mousepox infection of lungs

Fas receptor-Fas ligand (FasL) signalling is involved in apoptosis of immune cells as well as of the virus infected target cells but increasing evidence accumulates on Fas as a mediator of apoptosis-independent processes such as induction of activating and proinflammatory signals. In this study, we examined the role of Fas/FasL pathway in inflammatory and antiviral response in lungs using a mousepox model applied to C57BL6/J, B6. MRL-Faslpr/J, and B6Smn.C3-Faslgld/J mice. Ectromelia virus (ECTV) infection of Fas- and FasL-deficient mice led to increased virus titers in lungs and decreased migration of IFN-γ expressing NK cells, CD4+ T cells, CD8+ T cells, and decreased IL-15 expression. The lungs of ECTV-infected Fas- and FasL-deficient mice showed significant inflammation during later phases of infection accompanied by decreased expression of anti-inflammatory IL-10 and TGF-β1 cytokines and disturbances in CXCL1 and CXCL9 expression. Experiments in vitro demonstrated that ECTV-infected cultures of epithelial cells, but not macrophages, upregulate Fas and FasL and are susceptible to Fas-induced apoptosis. Our study demonstrates that Fas/FasL pathway during ECTV infection of the lungs plays an important role in controlling local inflammatory response and mounting of antiviral response.

Virus-specific immune memory at peripheral sites of herpes simplex virus type 2 (HSV-2) infection in guinea pigs

Despite its importance in modulating HSV-2 pathogenesis, the nature of tissue-resident immune memory to HSV-2 is not completely understood. We used genital HSV-2 infection of guinea pigs to assess the type and location of HSV-specific memory cells at peripheral sites of HSV-2 infection. HSV-specific antibody-secreting cells were readily detected in the spleen, bone marrow, vagina/cervix, lumbosacral sensory ganglia, and spinal cord of previously-infected animals. Memory B cells were detected primarily in the spleen and to a lesser extent in bone marrow but not in the genital tract or neural tissues suggesting that the HSV-specific antibody-secreting cells present at peripheral sites of HSV-2 infection represented persisting populations of plasma cells. The antibody produced by these cells isolated from neural tissues of infected animals was functionally relevant and included antibodies specific for HSV-2 glycoproteins and HSV-2 neutralizing antibodies. A vigorous IFN-γ-secreting T cell response developed in the spleen as well as the sites of HSV-2 infection in the genital tract, lumbosacral ganglia and spinal cord following acute HSV-2 infection. Additionally, populations of HSV-specific tissue-resident memory T cells were maintained at these sites and were readily detected up to 150 days post HSV-2 infection. Unlike the persisting plasma cells, HSV-specific memory T cells were also detected in uterine tissue and cervicothoracic region of the spinal cord and at low levels in the cervicothoracic ganglia. Both HSV-specific CD4⁺ and CD8⁺ resident memory cell subsets were maintained long-term in the genital tract and sensory ganglia/spinal cord following HSV-2 infection. Together these data demonstrate the long-term maintenance of both humoral and cellular arms of the adaptive immune response at the sites of HSV-2 latency and virus shedding and highlight the utility of the guinea pig infection model to investigate tissue-resident memory in the setting of HSV-2 latency and spontaneous reactivation.

Immunological aspects of acute and recurrent herpes simplex keratitis

Herpes simplex keratitis (HSK) belongs to the major causes of visual morbidity worldwide and available methods of treatment remain unsatisfactory. Primary infection occurs usually early in life and is often asymptomatic. Chronic visual impairment and visual loss are caused by corneal scaring, thinning, and vascularization connected with recurrent HSV infections. The pathogenesis of herpetic keratitis is complex and is still not fully understood. According to the current knowledge, corneal scarring and vascularization are the result of chronic inflammatory reaction against HSV antigens. In this review we discuss the role of innate and adaptive immunities in acute and recurrent HSV ocular infection and present the potential future targets for novel therapeutical options based on immune interventions.

Current thinking on genital herpes

PURPOSE OF REVIEW

Genital herpes has a high global prevalence and burden of disease. This manuscript highlights recent advances in our understanding of genital herpes simplex virus (HSV) infections.

RECENT FINDINGS

Studies demonstrate a changing epidemiological landscape with an increasing proportion of genital herpes cases associated with HSV type 1. There is also growing evidence that the majority of infected individuals exhibit frequent, brief shedding episodes that are most often asymptomatic, which likely contribute to high HSV transmission rates. Given this finding as well as readily available serological assays, some have proposed that routine HSV screening be performed; however, this remains controversial and is not currently recommended. Host immune responses, particularly local CD4 and CD8 T cell activity, are crucial for HSV control and clearance following initial infection, during latency and after reactivation. Prior HSV immunity may also afford partial protection against HSV reinfection and disease. Although HSV vaccine trials have been disappointing to date and existing antiviral medications are limited, novel prophylactic and therapeutic modalities are currently in development.

SUMMARY

Although much remains unknown about genital herpes, improved knowledge of HSV epidemiology, pathogenesis and host immunity may help guide new strategies for disease prevention and control.

Cultivated vaginal microbiomes alter HIV-1 infection and antiretroviral efficacy in colonized epithelial multilayer cultures

There is a pressing need for modeling of the symbiotic and at times dysbiotic relationship established between bacterial microbiomes and human mucosal surfaces. In particular clinical studies have indicated that the complex vaginal microbiome (VMB) contributes to the protection against sexually-transmitted pathogens including the life-threatening human immunodeficiency virus (HIV-1). The human microbiome project has substantially increased our understanding of the complex bacterial communities in the vagina however, as is the case for most microbiomes, very few of the community member species have been successfully cultivated in the laboratory limiting the types of studies that can be completed. A genetically controlled ex vivo model system is critically needed to study the complex interactions and associated molecular dialog. We present the first vaginal mucosal culture model that supports colonization by both healthy and dysbiotic VMB from vaginal swabs collected from routine gynecological patients. The immortalized vaginal epithelial cells used in the model and VMB cryopreservation methods provide the opportunity to reproducibly create replicates for lab-based evaluations of this important mucosal/bacterial community interface. The culture system also contains HIV-1 susceptible cells allowing us to study the impact of representative microbiomes on replication. Our results show that our culture system supports stable and reproducible colonization by VMB representing distinct community state types and that the selected representatives have significantly different effects on the replication of HIV-1. Further, we show the utility of the system to predict unwanted alterations in efficacy or bacterial community profiles following topical application of a front line antiretroviral.

The expression of IL-2 and IL-4 in CD4(+) T cells from mouse lymph nodes and spleen during HSV-1-induced facial palsy

OBJECTIVE

Herpes simplex virus 1 (HSV-1) is regarded as an important underlying cause of Bell's palsy, but the immunologic mechanism remains unknown. Here, we employed a mouse facial paralysis model to investigate the expressions of CD4(+) T lymphocytes and interleukin (IL)-2 and -4 in the left draining cervical lymph nodes (LCLN) and spleen, as well as the inhibitory effects of glucocorticoids (GCs).

METHODS

HSV-1 was inoculated into the surface of the posterior auricle to generate the facial paralysis model. The paralyzed mice were divided into three groups; in one group without any treatment, mice were killed at different time points, and those in the other two groups were injected with methylprednisolone sodium succinate (MPSS) or with a combination of MPSS and GC receptor blocker (RU486). The expression levels of CD4(+) T lymphocytes and CD4(+)-IL-2(+) and CD4(+)-IL-4(+) cells in the LCLN and spleen were detected by fluorescence-activated cell sorting.

RESULTS

Expression levels of CD4(+), IL-2, and IL-4 first increased then decreased in LCLN and spleen and peaked 5 and 7 days, respectively, after the manifestation of facial paralysis. All the data at the peak points were significantly different compared with control (p < 0.05), and these effects were inhibited by MPSS.

CONCLUSION

Our results suggest that CD4(+), IL-2, and IL-4 participate in the HSV-1-induced facial paralysis immune response. MPSS can effectively attenuate HSV-1-mediated nervous system damage, which is associated with its inhibitory effect on expression of these inflammatory markers.

Induction of potent protection against acute and latent herpes simplex virus infection in mice vaccinated with dendritic cells

BACKGROUND AIMS

Dendritic cells (DCs) are the most potent antigen presenting cells of the immune system and have been under intense study with regard to their use in immunotherapy against cancer and infectious disease agents. In the present study, DCs were employed to assess their value in protection against live virus challenge in an experimental model using lethal and latent herpes simplex virus (HSV) infection in Balb/c mice.

METHODS

DCs obtained ex vivo in the presence of granulocyte-macrophage colony-stimulating factor and interleukin-4 were loaded with HSV-1 proteins (DC/HSV-1 vaccine). Groups of mice were vaccinated twice, 7 days apart, via subcutaneous, intraperitoneal or intramuscular routes with DC/HSV-1 and with mock (DC without virus protein) and positive (alum adjuvanted HSV-1 proteins [HSV-1/ALH]) control vaccines. After measuring anti-HSV-1 antibody levels in blood samples, mice were given live HSV-1 intraperitoneally or via ear pinna to assess the protection level of the vaccines with respect to lethal or latent infection challenge.

RESULTS

Intramuscular, but not subcutaneous or intraperitoneal, administration of DC/HSV-1 vaccine provided complete protection against lethal challenge and establishment of latent infection as assessed by death and virus recovery from the trigeminal ganglia. It was also shown that the immunity was not associated with antibody production because DC/HSV-1 vaccine, as opposed to HSV-1/ALH vaccine, produced very little, if any, HSV-1-specific antibody.

CONCLUSIONS

Overall, our results may have some impact on the design of vaccines against genital HSV as well as chronic viral infections such as hepatitis B virus, hepatitis C virus and human immunodeficiency virus.

Adoptive transfer of cytomegalovirus-specific effector CD4+ T cells provides antiviral protection from murine CMV infection

Cytomegalovirus (CMV) infects a majority of the human population and establishes a life-long persistence. CMV infection is usually asymptomatic but the virus carries pathogenic potential and causes severe disease in immunocompromised individuals. T-cell-mediated immunity plays an essential role in control of CMV infection and adoptive transfer of CMV-specific CD8(+) T cells restores viral immunity in immunosuppressed patients but a role for CD4(+) T cells remains elusive. Here, we analyzed in adoptive transfer studies the features and antiviral functions of virus-specific CD4(+) T cells during primary murine CMV (MCMV) infection. MCMV-specific CD4(+) T cells expanded upon MCMV infection and displayed an effector phenotype and function. Adoptive transfer of in vivo activated MCMV-specific CD4(+) T cells to immune-compromised mice was protective during pathogenic MCMV infection and IFN-γ was a crucial mediator of this protective capacity. Moreover, co-transfer of low doses of both MCMV-specific CD4(+) T cells and CD8(+) T cells synergized in control of lytic viral replication in immune-compromised mice. Our data reveal a pivotal antiviral role for virus-specific CD4(+) T cells in protection from pathogenic CMV infection and provide evidence for their antiviral therapeutic potential.

Protective effects of red ginseng extract against vaginal herpes simplex virus infection

Numerous studies have suggested that Korean red ginseng (KRG) extract has various immune modulatory activities both in vivo and in vitro. In this study, we used a mouse model to examine the effects of orally administered KRG extract on immunity against herpes simplex virus (HSV). Balb/c mice were administered with 100, 200, and 400 mg/kg oral doses of KRG extract for 10 d and then vaginally infected with HSV. We found that KRG extract rendered recipients more resistant against HSV vaginal infection and further systemic infection, including decreased clinical severity, increased survival rate, and accelerated viral clearance. Such results appeared to be mediated by increased vaginal IFN-γ secretion. Moreover, increased mRNA expression of IFN-γ, granzyme B, and Fas-ligand was identified in the iliac lymph node and vaginal tracts of KRG extract treated groups (200 and 400 mg/kg). These results suggest that the activities of local natural killer cells were promoted by KRG extract consumption and that KRG may be an attractive immune stimulator for helping hosts overcome HSV infection.

Herpesviruses placating the unwilling host: manipulation of the MHC class II antigen presentation pathway

Lifelong persistent infection by herpesviruses depends on the balance between host immune responses and viral immune evasion. CD4 T cells responding to antigens presented on major histocompatibility complex class II (MHC-II) molecules are known to play an important role in controlling herpesvirus infections. Here we review, with emphasis on human herpesvirus infections, the strategies evolved to evade CD4 T cell immunity. These viruses target multiple points on the MHC class II antigen presentation pathway. The mechanisms include: suppression of CIITA to inhibit the synthesis of MHC class II molecules, diversion or degradation of HLA-DR molecules during membrane transport, and direct targeting of the invariant chain chaperone of HLA-DR.

Glycoprotein G of herpes simplex virus 2 as a novel vaccine antigen for immunity to genital and neurological disease

The envelope glycoproteins of herpes simplex virus 1 (HSV-1) and HSV-2, with the exception of glycoprotein G, elicit cross-reactive B- and T-cell responses. Human vaccine trials, using the cross-reactive glycoproteins B and D, have shown no protection against genital HSV-2 infection or disease. In this study, the mature form of glycoprotein G (mgG-2) of HSV-2 was used for immunization of mice, either alone or in combination with adjuvant CpG, followed by an intravaginal challenge with a lethal dose of a fully virulent HSV-2 strain. Mice immunized with mgG-2 plus CpG showed low disease scores and a significantly higher survival rate (73%) than mice immunized with mgG-2 alone (20%) or controls (0%). Accordingly, limited numbers of infectious HSV-2 particles were detected in the spinal cord of mice immunized with mgG-2 plus CpG. The observed protection was associated with a gamma interferon (IFN-γ) response by splenic CD4(+) T cells upon antigen restimulation in vitro and in vaginal washes 1 day postinfection. The majority of sera collected from mice immunized with mgG-2 plus CpG showed macrophage-mediated antibody-dependent cellular cytotoxicity and antibody-dependent complement-mediated cytolysis, while no neutralization activity was observed. In conclusion, we have shown that immunization with the type-specific mgG-2 protein in combination with CpG could elicit protective immunity against an otherwise lethal vaginal HSV-2 challenge. The mgG-2 protein may therefore constitute a promising HSV-2 vaccine antigen to be considered for future human trials.

Increased protection from vaccinia virus infection in mice genetically prone to lymphoproliferative disorders

Mutations in the genes that encode Fas or Fas ligand (FasL) can result in poor restraints on lymphocyte activation and in increased susceptibility to autoimmune disorders. Because these mutations portend a continuously activated immune state, we hypothesized that they might in some cases confer resistance to infection. To examine this possibility, the immune response to, morbidity caused by, and clearance of vaccinia virus (VACV) Western Reserve was examined in 5- to 7-week-old Fas mutant (lpr) mice, before an overt lymphoproliferative disorder was observable. On day 6 after VACV infection, C57BL/6-lpr (B6-lpr) mice had decreased morbidity, decreased viral titers, and an increased percentage and number of CD4(+) and CD8(+) T cells. As early as day 2 after infection, B6-lpr mice had decreased liver and spleen viral titers and increased numbers of and increased gamma interferon (IFN-γ) production by several different effector cell populations. Depletion of individual effector cell subsets did not inhibit the resistance of B6-lpr mice. Uninfected B6-lpr mice also had increased numbers of NK cells, γδ(+) T cells, and CD44(+) CD4(+) and CD44(+) CD8(+) T cells compared to uninfected B6 mice. Antibody to IFN-γ resulted in increased virus load in both B6 and B6-lpr mice and eliminated the differences in viral titers between them. These results suggest that IFN-γ produced by multiple activated leukocyte populations in Fas-deficient hosts enhances resistance to some viral infections.

Expanding roles for CD4⁺ T cells in immunity to viruses

CD4⁺ T cells are orchestrators, regulators and direct effectors of antiviral immunity.

Neutralizing antibodies provide protection against many viral pathogens, and CD4⁺ T cells can help B cells to generate stronger and longer-lived antibody responses.

CD4⁺ T cells help antiviral CD8⁺ T cells in two main ways: they maximize CD8⁺ T cell population expansion during a primary immune response and also facilitate the generation of virus-specific memory CD8⁺ T cell populations.

In addition to their helper functions, CD4⁺ T cells contribute directly to viral clearance. They secrete cytokines with antiviral activities and, in some circumstances, can eliminate infected cells through cytotoxic killing.

Memory CD4⁺ T cells provide superior protection during re-infection with a virus. Compared with new effector CD4⁺ T cells, memory CD4⁺ T cells have enhanced helper and effector functions and can rapidly trigger innate immune defence mechanisms early in the infection.

Immunity to viruses is typically associated with the development of cytotoxic CD8⁺ T cells. However, CD4⁺ T cells are also important for protection during viral infection. Here, the authors describe the various ways in which different CD4⁺T cell subsets can contribute to the antiviral immune response.

Viral pathogens often induce strong effector CD4⁺ T cell responses that are best known for their ability to help B cell and CD8⁺ T cell responses. However, recent studies have uncovered additional roles for CD4⁺ T cells, some of which are independent of other lymphocytes, and have described previously unappreciated functions for memory CD4⁺ T cells in immunity to viruses. Here, we review the full range of antiviral functions of CD4⁺ T cells, discussing the activities of these cells in helping other lymphocytes and in inducing innate immune responses, as well as their direct antiviral roles. We suggest that all of these functions of CD4⁺ T cells are integrated to provide highly effective immune protection against viral pathogens.

Modulation of peripheral cytotoxic cells and ictogenesis in a model of seizures

PURPOSE

A link between seizure susceptibility, blood-brain barrier (BBB) failure, and the activation of peripheral white blood cells has been recently proposed. However, the molecular players involved in this cascade of events are unknown. We tested the hypothesis that immunosupression by splenectomy or lack of perforin, a downstream factor of natural killer (NK) and cytotoxic T cells, could reduce seizure onset.

METHODS

Pilocarpine was used to induce seizures in adult rats wild-type and perforin-deficient mice. Splenectomy was performed prior to pilocarpine injection. Seizure onset was evaluated by electroencephalography (EEG) and joint time-frequency analysis. Spleens from control and pilocarpine-treated groups were analyzed for anatomical changes and CD3+ cell content. BBB damage was assessed by measuring albumin parenchymal extravasation. Fluorescence-activated cell sorting (FACS) analysis was performed on spleen and brain tissue of wild-type and perforin-deficient mice treated, or not, with pilocarpine.

KEY FINDINGS

Splenectomy significantly reduced seizure-associated mortality. Histologic analysis of the spleens exposed to pilocarpine revealed altered white and red pulp anatomy and an increase in CD3+ T cells. Onset of status epilepticus (SE) and mortality were significantly decreased in perforin-deficient mice. Pilocarpine significantly increased spleen NK 1.1 and CD8+ cell percentage; in contrast, the brain inflammatory cell profile remained unchanged at the time of pilocarpine SE. BBB damage was reduced in the perforin-deficient pilocarpine-treated mice.

SIGNIFICANCE

Immunosuppressant maneuvers such as splenectomy or lack of perforin decrease the onset or the severity of pilocarpine SE. Our results suggest that cytotoxic lymphocytes, and specifically the cytolytic factor perforin, may be key molecular players involved in the axis between peripheral intravascular inflammation and seizures.

Immunization with a vaccine combining herpes simplex virus 2 (HSV-2) glycoprotein C (gC) and gD subunits improves the protection of dorsal root ganglia in mice and reduces the frequency of recurrent vaginal shedding of HSV-2 DNA in guinea pigs compared to immunization with gD alone

Attempts to develop a vaccine to prevent genital herpes simplex virus 2 (HSV-2) disease have been only marginally successful, suggesting that novel strategies are needed. Immunization with HSV-2 glycoprotein C (gC-2) and gD-2 was evaluated in mice and guinea pigs to determine whether adding gC-2 to a gD-2 subunit vaccine would improve protection by producing antibodies that block gC-2 immune evasion from complement. Antibodies produced by gC-2 immunization blocked the interaction between gC-2 and complement C3b, and passive transfer of gC-2 antibody protected complement-intact mice but not C3 knockout mice against HSV-2 challenge, indicating that gC-2 antibody is effective, at least in part, because it prevents HSV-2 evasion from complement. Immunization with gC-2 also produced neutralizing antibodies that were active in the absence of complement; however, the neutralizing titers were higher when complement was present, with the highest titers in animals immunized with both antigens. Animals immunized with the gC-2-plus-gD-2 combination had robust CD4+ T-cell responses to each immunogen. Multiple disease parameters were evaluated in mice and guinea pigs immunized with gC-2 alone, gD-2 alone, or both antigens. In general, gD-2 outperformed gC-2; however, the gC-2-plus-gD-2 combination outperformed gD-2 alone, particularly in protecting dorsal root ganglia in mice and reducing recurrent vaginal shedding of HSV-2 DNA in guinea pigs. Therefore, the gC-2 subunit antigen enhances a gD-2 subunit vaccine by stimulating a CD4+ T-cell response, by producing neutralizing antibodies that are effective in the absence and presence of complement, and by blocking immune evasion domains that inhibit complement activation.

Infection of peripheral blood mononuclear cells with neuropathogenic equine herpesvirus type-1 strain Ab4 reveals intact interferon-α induction and induces suppression of anti-inflammatory interleukin-10 responses in comparison to other viral strains

The recent increase in incidence, morbidity, and mortality of neurological disease induced by equine herpesvirus type 1 (EHV-1) has suggested a change of virulence of the virus. The exact mechanisms by which EHV-1 induces neurologic disease are not known. Environmental, viral, and host risk factors might contribute to neurological manifestation. Here, we investigated innate interferon-α (IFN-α), interleukin-10 (IL-10) and IL-4 responses after infection of equine peripheral blood mononuclear cells (PBMC) with EHV-1 using an available cytokine multiplex assay. Three viral strains representing an older isolate (RacL11), a recent abortigenic (NY03) and a neuropathogenic isolate (Ab4) were compared to identify differences in cytokine induction that might explain the increased pathogenicity of Ab4. Cytokine concentrations were also compared between foals, mares after birth, pregnant and non-pregnant mares to investigate whether immune responses to EHV-1 infection are influenced by age or pregnancy status. PBMC from all groups secreted high concentrations of anti-viral IFN-α in response to EHV-1. A reduced response was observed in foals compared to non-pregnant mares. EHV-1 infection induced moderate IL-10 and overall low IL-4 secretion. Ab4 infection resulted in a significant reduction of IL-10 responses in adult horses. IL-10 and IL-4 responses were lower in foals than in most mare groups. These data suggested that EHV-1 induces robust IFN-α secretion without major differences between viral strains. However, anti-inflammatory IL-10 production was significantly reduced after infection with neuropathogenic Ab4. The ability of this EHV-1 isolate to down-regulate IL-10 production might contribute to increased local inflammation and a higher risk for neurological manifestation of the disease after infection with Ab4.

The Role of Plasmacytoid Dendritic Cells in Innate and Adaptive Immune Responses against Alpha Herpes Virus Infections

In 1999, two independent groups identified plasmacytoid dendritic cells (PDC) as major type I interferon- (IFN-) producing cells in the blood. Since then, evidence is accumulating that PDC are a multifunctional cell population effectively coordinating innate and adaptive immune responses. This paper focuses on the role of different immune cells and their interactions in the surveillance of alpha herpes virus infections, summarizes current knowledge on PDC surface receptors and their role in direct cell-cell contacts, and develops a risk factor model for the clinical implications of herpes simplex and varicella zoster virus reactivation. Data from studies involving knockout mice and cell-depletion experiments as well as human studies converge into a "spider web", in which the direct and indirect crosstalk between many cell populations tightly controls acute, latent, and recurrent alpha herpes virus infections. Notably, cells involved in innate immune regulations appear to shape adaptive immune responses more extensively than previously thought.

Inflammation in neuroviral diseases

During any viral infection of the central nervous system (CNS), the extent and nature of neural cell alterations are dictated by the localization of virus replication and, possibly, persistence. However, one additional source of CNS damage comes from the immune response that develops following CNS viral infection. Indeed, despite of its major role in controlling virus spread in the infected CNS, the immune system is equipped with numerous molecular effectors shared with the nervous system that may greatly alter the homeostasis and function of neural cells. Proinflammatory cytokines and metalloproteases belong to this inflammatory cascade. Besides neurovirulence, the crosstalk engaged between neural and immune cells is a major factor determining the outcome of neuroviral infections.

Characterization of the host immune response in human Ganglia after herpes zoster

Varicella-zoster virus (VZV) causes varicella (chicken pox) and establishes latency in ganglia, from where it reactivates to cause herpes zoster (shingles), which is often followed by postherpetic neuralgia (PHN), causing severe neuropathic pain that can last for years after the rash. Despite the major impact of herpes zoster and PHN on quality of life, the nature and kinetics of the virus-immune cell interactions that result in ganglion damage have not been defined. We obtained rare material consisting of seven sensory ganglia from three donors who had suffered from herpes zoster between 1 and 4.5 months before death but who had not died from herpes zoster. We performed immunostaining to investigate the site of VZV infection and to phenotype immune cells in these ganglia. VZV antigen was localized almost exclusively to neurons, and in at least one case it persisted long after resolution of the rash. The large immune infiltrate consisted of noncytolytic CD8(+) T cells, with lesser numbers of CD4(+) T cells, B cells, NK cells, and macrophages and no dendritic cells. VZV antigen-positive neurons did not express detectable major histocompatibility complex (MHC) class I, nor did CD8(+) T cells surround infected neurons, suggesting that mechanisms of immune control may not be dependent on direct contact. This is the first report defining the nature of the immune response in ganglia following herpes zoster and provides evidence for persistence of non-latency-associated viral antigen and inflammation beyond rash resolution.

Immunization with a dominant-negative recombinant Herpes Simplex Virus (HSV) type 1 protects against HSV-2 genital disease in guinea pigs

Background

CJ9-gD is a novel dominant-negative recombinant herpes simplex virus type 1 (HSV-1) that is completely replication-defective, cannot establish detectable latent infection in vivo, and expresses high levels of the major HSV-1 antigen glycoprotein D immediately following infection. In the present study, CJ9-gD was evaluated as a vaccine against HSV-2 genital infection in guinea pigs.

Results

Animals immunized with CJ9-gD developed at least 700-fold higher titers of HSV-2-specific neutralization antibodies than mock-immunized controls. After challenge with wild-type HSV-2, all 10 control guinea pigs developed multiple genital lesions with an average of 21 lesions per animal. In contrast, only 2 minor lesions were found in 2 of 8 CJ9-gD-immunized animals, representing a 40-fold reduction on the incidence of primary genital lesions in immunized animals (p < 0.0001). Immunization significantly reduced the amount and duration of viral shedding and provided complete protection against neurological symptoms, while 90% of mock-immunized animals succumbed due to the severity of disease. Importantly, immunized animals showed no signs of recurrent disease or viral shedding during a 60-days observation period after recovery from primary infection, and carried 50-fold less latent viral DNA load in their dorsal root ganglia than the surviving mock-vaccinated controls (p < 0.0001).

Conclusions

Collectively, we demonstrate that vaccination with the HSV-1 recombinant CJ9-gD elicits strong and protective immune responses against primary and recurrent HSV-2 genital disease and significantly reduces the extent of latent infection.

HLA-DR: molecular insights and vaccine design

Vaccines are one of the most cost effective methods to control infectious diseases and at the same time one of the most complex products of the pharmaceutical industry. In contrast to other drugs, vaccines are used mainly in healthy individuals, often in children. For this reason, very high standards are set for their production. Subunit vaccines, especially peptide vaccines, can provide a safe and cost-effective alternative to vaccines produced from attenuated or inactivated pathogen preparations. Biochemical and structural studies of class II MHC-peptide complexes are beginning to provide a conceptual foundation for the rational design of subunit and peptide vaccines. In this review, we show how analysis of peptide-class II MHC complexes together with developing understanding of antigen processing pathways has opened the door to understanding the major rules that govern selection of T cell epitopes. We review progress towards computational prediction of such epitopes, and efforts to evaluate algorithms that incorporate various structural and/or biochemical aspects of the MHC-peptide interaction. Finally, using malaria as a model, we describe the development of a minimal subunit vaccine for the human malaria parasite Plasmodium falciparum.

Herpes simplex virus (HSV)-specific T cells activated in the absence of IFN-gamma express alternative effector functions but are not protective against genital HSV-2 infection

Interferon gamma (IFNgamma) is important for immune resistance to herpes simplex virus (HSV) infection. To examine the influence of IFNgamma on the development of HSV-specific immune responses and test for IFNgamma-independent adaptive immune mechanisms of protection, IFNgamma-deficient mice (IFNgamma(-/-)) were immunized with thymidine kinase-deficient HSV-2 (HSV-2 333tk(-)). HSV-specific cellular and humoral responses were elicited in immunized IFNgamma(-/-) mice resulting in increased resistance relative to non-immune C57BL/6J (B6) mice following challenge with fully virulent HSV-2. CD8(+) T cells from IFNgamma(-/-) mice displayed cytotoxic activity and secreted TNFalpha. HSV-specific CD4(+) T cells from immunized IFNgamma(-/-) mice secreted IL-4, TNFalpha, and IL-17, but unlike T cells from HSV-immune B6 mice, could not clear virus from genital tissue following adoptive transfer. HSV-immune IFNgamma(-/-) mice produced predominantly IgG(1) HSV-specific antibodies while immune B6 mice produced predominantly IgG(2c) antibodies. Transfer of equivalent amounts of HSV-specific antibodies from either strain to naïve mice imparted equivalent early resistance against infection of the genital epithelia. However, protection against neurological symptoms mediated by immune B6 antibodies was superior late in infection. Taken together, these results demonstrate that the limited resistance of HSV-immune IFNgamma(-/-) mice to HSV-2 infection resulted from the action of HSV-specific Ab rather than IFNgamma-independent effector functions of T cells. Further, protection against neurological manifestations of HSV-2 infection was superior in mice receiving Ab from immune B6 mice suggesting that Ab-mediated protective mechanisms involving IFNgamma-induced IgG subclasses were more effective once virus had spread to neural tissues.

Innate and adaptive immune responses to herpes simplex virus

Immune responses against HSV-1 and HSV-2 are complex and involve a delicate interplay between innate signaling pathways and adaptive immune responses. The innate response to HSV involves the induction of type I IFN, whose role in protection against disease is well characterized in vitro and in vivo. Cell types such as NK cells and pDCs contribute to innate anti-HSV responses in vivo. Finally, the adaptive response includes both humoral and cellular components that play important roles in antiviral control and latency. This review summarizes the innate and adaptive effectors that contribute to susceptibility, immune control and pathogenesis of HSV, and highlights the delicate interplay between these two important arms of immunity.

Race between retroviral spread and CD4+ T-cell response determines the outcome of acute Friend virus infection

Retroviruses can establish persistent infection despite induction of a multipartite antiviral immune response. Whether collective failure of all parts of the immune response or selective deficiency in one crucial part underlies the inability of the host to clear retroviral infections is currently uncertain. We examine here the contribution of virus-specific CD4(+) T cells in resistance against Friend virus (FV) infection in the murine host. We show that the magnitude and duration of the FV-specific CD4(+) T-cell response is directly proportional to resistance against acute FV infection and subsequent disease. Notably, significant protection against FV-induced disease is afforded by FV-specific CD4(+) T cells in the absence of a virus-specific CD8(+) T-cell or B-cell response. Enhanced spread of FV infection in hosts with increased genetic susceptibility or coinfection with Lactate dehydrogenase-elevating virus (LDV) causes a proportional increase in the number of FV-specific CD4(+) T cells required to control FV-induced disease. Furthermore, ultimate failure of FV/LDV coinfected hosts to control FV-induced disease is accompanied by accelerated contraction of the FV-specific CD4(+) T-cell response. Conversely, an increased frequency or continuous supply of FV-specific CD4(+) T cells is both necessary and sufficient to effectively contain acute infection and prevent disease, even in the presence of coinfection. Thus, these results suggest that FV-specific CD4(+) T cells provide significant direct protection against acute FV infection, the extent of which critically depends on the ratio of FV-infected cells to FV-specific CD4(+) T cells.

Immune control of mammalian gamma-herpesviruses: lessons from murid herpesvirus-4

Many acute viral infections can be controlled by vaccination; however, vaccinating against persistent infections remains problematic. Herpesviruses are a classic example. Here, we discuss their immune control, particularly that of gamma-herpesviruses, relating the animal model provided by murid herpesvirus-4 (MuHV-4) to human infections. The following points emerge: (i) CD8(+) T-cell evasion by herpesviruses confers a prominent role in host defence on CD4(+) T cells. CD4(+) T cells inhibit MuHV-4 lytic gene expression via gamma-interferon (IFN-gamma). By reducing the lytic secretion of immune evasion proteins, they may also help CD8(+) T cells to control virus-driven lymphoproliferation in mixed lytic/latent lesions. Similarly, CD4(+) T cells specific for Epstein-Barr virus lytic antigens could improve the impact of adoptively transferred, latent antigen-specific CD8(+) T cells. (ii) In general, viral immune evasion necessitates multiple host effectors for optimal control. Thus, subunit vaccines, which tend to prime single effectors, have proved less successful than attenuated virus mutants, which prime multiple effectors. Latency-deficient mutants could make safe and effective gamma-herpesvirus vaccines. (iii) The antibody response to MuHV-4 infection helps to prevent disease but is suboptimal for neutralization. Vaccinating virus carriers with virion fusion complex components improves their neutralization titres. Reducing the infectivity of herpesvirus carriers in this way could be a useful adjunct to vaccinating naive individuals with attenuated mutants.

New concepts in herpes simplex virus vaccine development: notes from the battlefield

The recent discovery that T cells recognize different sets of herpes simplex virus type 1 and type 2 epitopes from seropositive symptomatic and asymptomatic individuals might lead to a fundamental immunologic advance in vaccine development against herpes infection and diseases. The newly introduced needle-free mucosal (i.e., topical ocular and intravaginal) lipopeptide vaccines provide a novel strategy that might target ocular and genital herpes and possibly provide 'heterologous protection' from HIV-1. Indeed, mucosal self-adjuvanting lipopeptide vaccines are easy to manufacture, simple to characterize, extremely pure, cost-effective, highly immunogenic and safe. In this review, we bring together recent published and unpublished data that illuminates the status of epitope-based herpes vaccine development and present an overview of our recent approach to an 'asymptomatic epitope'-based lipopeptide vaccine.

Protective role of Fas-FasL signaling in lethal infection with herpes simplex virus type 2 in mice

Herpes simplex virus type 2 (HSV-2) induces acute local infection followed by latent infection in the nervous system and often leads to the development of lethal encephalitis in immunocompromised hosts. The mechanisms of immune protection against lethal HSV-2 infection, however, have not been clarified. In this study, we examined the roles of Fas-Fas ligand (FasL) signaling in lethal infection with HSV-2 by using mice with mutated Fas (lpr) or FasL (gld) in C57BL/6 background. Both lpr and gld mice exhibited higher mortality than wild-type (WT) C57BL/6 mice after infection with virulent HSV-2 strain 186 and showed significantly increased viral titers in the spinal cord compared with WT mice 9 days after infection, just before the mice started to die. There were no differences in the numbers of CD4+ and CD8+ T cells infiltrated in the spinal cord or in the levels of HSV-2-specific gamma interferon produced by those cells in a comparison of lpr and WT mice 9 days after infection. Adoptive transfer studies demonstrated that CD4+ T cells from WT mice protected gld mice from lethal infection by HSV-2. Furthermore, CD4+ T cells infiltrated in the spinal cord of HSV-2-infected WT mice expressed functional FasL that induced apoptosis of Fas-expressing target cells in vitro. These results suggest that FasL-mediated cytotoxic activity of CD4+ T cells plays an important role in host defense against lethal infection with HSV-2.