Evasion of the Cell-Mediated Immune Response by Alphaherpesviruses

Herpes simplex virus type 1 impairs mucosal-associated invariant T cells

Herpes simplex virus type 1 (HSV-1) is a highly successful pathogen that infects mucosal sites and adopts an arsenal of strategies to manipulate host immunity. Mucosal-associated invariant T (MAIT) cells are abundant innate-like T lymphocytes that recognize bacterial and fungal-derived vitamin B-related metabolites presented by major histocompatibility complex class I-related protein 1 (MR1). MAIT cells can also be activated in an MR1-independent manner via cytokine stimulation, predominantly by IL-12 and IL-18. MAIT cell alterations have been identified as being associated with a number of viral infections, but direct interactions between viruses and MAIT cells are poorly understood. It is unknown whether HSV-1 can infect MAIT cells and modulate their functions. Here, we show that HSV-1 can infect primary human MAIT cells, including CD4±/CD8± and CD56± MAIT cell subpopulations. Furthermore, HSV-1 infection profoundly inhibits the functional capacity of MAIT cells to respond to T cell receptor (TCR)-dependent stimulation by the MAIT cell activating ligand 5-(2-oxopropylideneamino)-6-D-ribitylaminouracil (5-OP-RU) and to cytokine stimulation by IL-12/IL-18. HSV-1-infected MAIT cells display reduced cytotoxic potential, diminished synthesis of effector cytokines, and decreased expression of key cytokine receptors including IL-18R. In addition, MAIT cells exposed to HSV-1-infected fibroblasts but which remained uninfected (viral GFP-negative) also exhibit a suppressed effector response to TCR-dependent stimulation. The functional suppression of HSV-1-exposed MAIT cells was not mediated by a soluble factor within the supernatant, suggesting direct contact of MAIT cells with HSV-1-infected fibroblasts is required. Overall, this study reveals that HSV-1 can infect MAIT cells and substantially impair MAIT cell effector functions.

IMPORTANCE

Mucosal-associated invariant T cells (MAIT cells) are "unconventional" immune cells that are becoming increasingly appreciated to play important roles in a variety of viral infections. Herpes simplex virus (HSV) causes significant human disease and is a master manipulator of multiple immune functions, but how this virus may control MAIT cells is poorly understood. We discovered that HSV can infect human MAIT cells and impair their functional capacity and also show that MAIT cells exposed to HSV, but which do not show evidence of infection, are similarly impaired. This study therefore identifies an additional immunomodulatory function of HSV.

Cell-mediated and humoral immune responses of cyprinids induced by a live attenuated vaccine against cyprinid herpesvirus 2 infection in comparison to the virus non-permissive high temperature water treatment

The live attenuated vaccine (P7-P8 strain) against cyprinid herpesvirus 2 (CyHV-2) infection of goldfish shows high protective efficacy. However, the underlying immune mechanism induced by P7-P8 vaccination remains unknown. It is known that the fish survived in the primary infection with CyHV-2 by the virus non-permissive high temperature (HT) water treatment elicit immunity against secondary virus challenge. In this study, the immunity induced by the P7-P8 vaccine was compared with that by HT treatment. To further explore the immunological responses of cyprinids, in addition to goldfish Carassius auratus, susceptible isogenic ginbuna C. auratus langsdorfii was included in this study. In the primary immune response, cyprinids were vaccinated with P7-P8, or treated with HT. In the secondary immune response, cyprinids were challenged with the virulent CyHV-2. The percentage dynamics of CD4-1 and CD8α positive lymphocytes were determined during the primary and secondary immune responses of the two cyprinids. Blood plasma was sampled to assess the anti-CyHV-2 IgM antibody titers. The vaccination with P7-P8 and HT-treatment induced high protection immunity in the cyprinids with relative percentage survival of over 88 % against virulent virus challenge. Our finding shows that the CD8α positive lymphocytes rather than CD4-1 positive lymphocytes play an important role in the secondary immune responses of cyprinids vaccinated with P7-P8. The CD4-1 positive lymphocytes rather than CD8α positive lymphocytes play an important role in the secondary immune responses of cyprinids treated with HT. The antibody titer of vaccinated cyprinids did not increase greatly even after virulent virus challenge. The results suggest the vaccine activates the CD8α cells and the secondary cell-mediated immunity. The differences in the induced immunity mechanisms in fish by the two measures might be based on the virus either being an avirulent virus form that cannot evade host responses or a virulent virus form that cannot propagate at non-permissive temperature.

Involvement of Human Cellular Proteins and Structures in Realization of the HIV Life Cycle: A Comprehensive Review, 2024

Human immunodeficiency virus (HIV) continues to be a global health challenge, with over 38 million people infected by the end of 2022. HIV-1, the predominant strain, primarily targets and depletes CD4+ T cells, leading to immunodeficiency and subsequent vulnerability to opportunistic infections. Despite the progress made in antiretroviral therapy (ART), drug resistance and treatment-related toxicity necessitate novel therapeutic strategies. This review delves into the intricate interplay between HIV-1 and host cellular proteins throughout the viral life cycle, highlighting key host factors that facilitate viral entry, replication, integration, and immune evasion. A focus is placed on actual findings regarding the preintegration complex, nuclear import, and the role of cellular cofactors such as FEZ1, BICD2, and NPC components in viral transport and genome integration. Additionally, the mechanisms of immune evasion via HIV-1 proteins Nef and Vpu, and their interaction with host MHC molecules and interferon signaling pathways, are explored. By examining these host-virus interactions, this review underscores the importance of host-targeted therapies in complementing ART, with a particular emphasis on the potential of genetic research and host protein stability in developing innovative treatments for HIV/AIDS.

Role of Neurotropic Viruses in Brain Metastasis of Breast Cancer: Mechanisms and Therapeutic Implications

Neurotropic viruses have been implicated in altering the central nervous system microenvironment and promoting brain metastasis of breast cancer through complex interactions involving viral entry mechanisms, modulation of the blood-brain barrier, immune evasion, and alteration of the tumour microenvironment. This narrative review explores the molecular mechanisms by which neurotropic viruses such as Herpes Simplex Virus, Human Immunodeficiency Virus, Japanese Encephalitis Virus, and Rabies Virus facilitate brain metastasis, focusing on their ability to disrupt blood-brain barrier integrity, modulate immune responses, and create a permissive environment for metastatic cell survival and growth within the central nervous system. Current therapeutic implications and challenges in targeting neurotropic viruses to prevent or treat brain metastasis are discussed, highlighting the need for innovative strategies and multidisciplinary approaches in virology, oncology, and immunology.

HIV vaccination: Navigating the path to a transformative breakthrough-A review of current evidence

Background and Aim

Human immunodeficiency virus (HIV) remains a significant global health challenge, with approximately 39 million people living with HIV worldwide as of 2022. Despite progress in antiretroviral therapy, achieving the UNAIDS "95-95-95" target to end the HIV epidemic by 2025 faces challenges, particularly in sub-Saharan Africa. The pursuit of an HIV vaccine is crucial, offering durable immunity and the potential to end the epidemic. Challenges in vaccine development include the lack of known immune correlates, suitable animal models, and HIV's high mutation rate. This study aims to explore the current state of HIV vaccine development, focusing on the challenges and innovative approaches being investigated.

Methods

In writing this review, we conducted a search of medical databases such as PubMed, ResearchGate, Web of Science, Google Scholar, and Scopus. The exploration of messenger ribonucleic acid vaccines, which have proven successful in the SARS-CoV-2 pandemic, presents a promising avenue for HIV vaccine development. Understanding HIV-1's ability to infiltrate various bodily compartments, establish reservoirs, and manipulate immune responses is critical. Robust cytotoxic T lymphocytes and broadly neutralizing antibodies are identified as key components, though their production faces challenges. Innovative approaches, including computational learning and advanced drug delivery systems, are being investigated to effectively activate the immune system.

Results and Conclusions

Discrepancies between animal models and human responses have hindered the progress of vaccine development. Despite these challenges, ongoing research is focused on overcoming these obstacles through advanced methodologies and technologies. Addressing the challenges in HIV vaccine development is paramount to realizing an effective HIV-1 vaccine and achieving the goal of ending the epidemic. The integration of innovative approaches and a deeper understanding of HIV-1's mechanisms are essential steps toward this transformative breakthrough.

The immunobiology of herpes simplex virus encephalitis and post-viral autoimmunity

Herpes simplex virus encephalitis (HSE) is the leading cause of non-epidemic encephalitis in the developed world and, despite antiviral therapy, mortality and morbidity is high. The emergence of post-HSE autoimmune encephalitis reveals a new immunological paradigm in autoantibody-mediated disease. A reductionist evaluation of the immunobiological mechanisms in HSE is crucial to dissect the origins of post-viral autoimmunity and supply rational approaches to the selection of immunotherapeutics. Herein, we review the latest evidence behind the phenotypic progression and underlying immunobiology of HSE including the cytokine/chemokine environment, the role of pathogen-recognition receptors, T- and B-cell immunity and relevant inborn errors of immunity. Second, we provide a contemporary review of published patients with post-HSE autoimmune encephalitis from a combined cohort of 110 patients. Third, we integrate novel mechanisms of autoimmunization in deep cervical lymph nodes to explore hypotheses around post-HSE autoimmune encephalitis and challenge these against mechanisms of molecular mimicry and others. Finally, we explore translational concepts where neuroglial surface autoantibodies have been observed with other neuroinfectious diseases and those that generate brain damage including traumatic brain injury, ischaemic stroke and neurodegenerative disease. Overall, the clinical and immunological landscape of HSE is an important and evolving field, from which precision immunotherapeutics could soon emerge.

The chemokine receptor CCR5: multi-faceted hook for HIV-1

Chemokines are cytokines whose primary role is cellular activation and stimulation of leukocyte migration. They perform their various functions by interacting with G protein-coupled cell surface receptors (GPCRs) and are involved in the regulation of many biological processes such as apoptosis, proliferation, angiogenesis, hematopoiesis or organogenesis. They contribute to the maintenance of the homeostasis of lymphocytes and coordinate the function of the immune system. However, chemokines and their receptors are sometimes hijacked by some pathogens to infect the host organism. For a given chemokine receptor, there is a wide structural, organizational and conformational diversity. In this review, we describe the evidence for structural variety reported for the chemokine receptor CCR5, how this variability can be exploited by HIV-1 to infect its target cells and what therapeutic solutions are currently being developed to overcome this problem.

Understanding the Neurotrophic Virus Mechanisms and Their Potential Effect on Systemic Lupus Erythematosus Development

Central nervous system (CNS) pathologies are a public health concern, with viral infections one of their principal causes. These viruses are known as neurotropic pathogens, characterized by their ability to infiltrate the CNS and thus interact with various cell populations, inducing several diseases. The immune response elicited by neurotropic viruses in the CNS is commanded mainly by microglia, which, together with other local cells, can secrete inflammatory cytokines to fight the infection. The most relevant neurotropic viruses are adenovirus (AdV), cytomegalovirus (CMV), enterovirus (EV), Epstein-Barr Virus (EBV), herpes simplex virus type 1 (HSV-1), and herpes simplex virus type 2 (HSV-2), lymphocytic choriomeningitis virus (LCMV), and the newly discovered SARS-CoV-2. Several studies have associated a viral infection with systemic lupus erythematosus (SLE) and neuropsychiatric lupus (NPSLE) manifestations. This article will review the knowledge about viral infections, CNS pathologies, and the immune response against them. Also, it allows us to understand the relevance of the different viral proteins in developing neuronal pathologies, SLE and NPSLE.

Oncolytic α-herpesvirus and myeloid-tropic cytomegalovirus cooperatively enhance systemic antitumor responses

Oncolytic virotherapy aims to activate host antitumor immunity. In responsive tumors, intratumorally injected herpes simplex viruses (HSVs) have been shown to lyse tumor cells, resulting in local inflammation, enhanced tumor antigen presentation, and boosting of antitumor cytotoxic lymphocytes. In contrast to HSV, cytomegalovirus (CMV) is nonlytic and reprograms infected myeloid cells, limiting their antigen-presenting functions and protecting them from recognition by natural killer (NK) cells. Here, we show that when co-injected into mouse tumors with an oncolytic HSV, mouse CMV (mCMV) preferentially targeted tumor-associated myeloid cells, promoted the local release of proinflammatory cytokines, and enhanced systemic antitumor immune responses, leading to superior control of both injected and distant contralateral tumors. Deletion of mCMV genes m06, which degrades major histocompatibility complex class I (MHC class I), or m144, a viral MHC class I homolog that inhibits NK activation, was shown to diminish the antitumor activity of the HSV/mCMV combination. However, an mCMV recombinant lacking the m04 gene, which escorts MHC class I to the cell surface, showed superior HSV adjuvanticity. CMV is a potentially promising agent with which to reshape and enhance antitumor immune responses following oncolytic HSV therapy.

HIV-Host Cell Interactions

The development of antiretroviral drugs (ARVs) was a great milestone in the management of HIV infection. ARVs suppress viral activity in the host cell, thus minimizing injury to the cells and prolonging life. However, an effective treatment has remained elusive for four decades due to the successful immune evasion mechanisms of the virus. A thorough understanding of the molecular interaction of HIV with the host cell is essential in the development of both preventive and curative therapies for HIV infection. This review highlights several inherent mechanisms of HIV that promote its survival and propagation, such as the targeting of CD4+ lymphocytes, the downregulation of MHC class I and II, antigenic variation and an envelope complex that minimizes antibody access, and how they collaboratively render the immune system unable to mount an effective response.

Strategies to induce natural killer cell tolerance in xenotransplantation

Eliminating major xenoantigens in pig cells has drastically reduced human antibody-mediated hyperacute xenograft rejection (HXR). Despite these advancements, acute xenograft rejection (AXR) remains one of the major obstacles to clinical xenotransplantation, mediated by innate immune cells, including macrophages, neutrophils, and natural killer (NK) cells. NK cells play an 'effector' role by releasing cytotoxicity granules against xenogeneic cells and an 'affecter' role on other immune cells through cytokine secretion. We highlight the key receptor-ligand interactions that determine the NK cell response to target cells, focusing on the regulation of NK cell activating receptor (NKG2D, DNAM1) and inhibitory receptor (KIR2DL1-4, NKG2A, and LIR-1) signaling pathways. Inhibition of NK cell activity may protect xenografts from cytotoxicity. Recent successful approaches to reducing NK cell-mediated HXR and AXR are reviewed, including genetic modifications of porcine xenografts aimed at improving pig-to-human compatibility. Future directions to promote xenograft acceptance are discussed, including NK cell tolerance in pregnancy and NK cell evasion in viral infection.

Pseudorabies Virus Tegument Protein UL13 Suppresses RLR-Mediated Antiviral Innate Immunity through Regulating Receptor Transcription

Pseudorabies virus (PRV) has evolved various strategies to escape host antiviral immune responses. However, it remains unclear whether and how PRV-encoded proteins modulate the RIG-I-like receptor (RLR)-mediated signals for immune evasion. Here, we show that the PRV tegument protein UL13 functions as an antagonist of RLR-mediated antiviral responses via suppression of the transcription of RIG-I and MDA5, but not LGP2. UL13 overexpression significantly inhibits both the mRNA and protein levels of RIG-I and MDA5, along with RIG-I- or MDA5-mediated antiviral immune responses, whereas overexpression of RIG-I or MDA5 counteracts such UL13-induced suppression. Mechanistically, UL13 suppresses the expression of RIG-I and MDA5 by inhibiting activation of the transcription factor NF-κB. Consequently, overexpression of p65 promotes the activation of RIG-I and MDA5 promoters. Moreover, deletion of the p65-binding sites in the promoters of RIG-I or MDA5 abolishes the suppression role of UL13. As a result, mutant PRV lacking UL13 elicits stronger host antiviral immune responses than PRV-WT. Hence, our results provide a novel functional role of UL13-induced suppression of host antiviral immunity through modulating receptors' transcription.

Evaluation of the Safety and Immunogenicity of Duck-Plague Virus gE Mutants

Duck plague (DP) is an acute infectious disease in the duck industry. The duck plague virus (DPV) is the pathogen, a subfamily of alphaherpesvirinae. gE is a type I membrane protein that contains three parts: an extracellular domain, a transmembrane domain, and a cytoplasmic domain. gE is the major virulence determinant of α-herpesvirus. However, the functions of the gE extracellular and cytoplasmic domains have not been reported in DPV. In this study, a gE extracellular domain deletion mutant and a gE cytoplasmic domain deletion mutant were constructed from DPV. Virus replication kinetics showed that the growth titers of both the gE ectodomain-deleted mutant virus and the gE cytoplasmic domain-deleted virus in DEFs were lower than that of the parental virus CHv-50. DPV CHv-gEΔET and DPV CHv-gEΔCT were continuously passed to the 20th passage in DEFs and the 10th in ducklings. The mutant virus DNA after passage was extracted for identification. The results showed that the gE ectodomain and gE cytoplasmic domain deletion mutant viruses have good genetic stability. The ducklings in each group (n=10) were inoculated with the same titers of DPV CHv-gEΔET, DPV CHv-gEΔCT, DPV CHv-ΔgE, and parental CHv-50, respectively. Clinical symptoms and serum antibody levels were detected after inoculation. The results showed that the virulence of DPV CHv-gEΔCT to ducklings was reduced compared with parental CHv-50, while the virulence of DPV CHv-gEΔET to ducklings was significantly reduced. 10⁵ TCID₅₀ DPV CHv-gEΔET or DPV CHv-ΔgE can induce ducklings to produce DPV-specific antibodies, protect the ducklings from virulent CHv challenge. Therefore, DPV CHv-gEΔET may serve as a promising vaccine candidate to prevent and control duck plague.

Fas/FasL Contributes to HSV-1 Brain Infection and Neuroinflammation

The Fas/FasL pathway plays a key role in immune homeostasis and immune surveillance. In the central nervous system (CNS) Fas/FasL is involved in axonal outgrowth and adult neurogenesis. However, little is known about the role of the Fas/FasL pathway in herpes encephalitis. In this study, we used a neuropathogenic clinical strain of herpes simplex virus type 1 (HSV-1) to explore infection-induced inflammation and immune responses in the mouse brain and the role of Fas/FasL in antiviral CNS immunity. HSV-1 CNS infection induced the infiltration of Fas- FasL-bearing monocytes and T cells in the brain and also to an up-regulation of Fas and FasL expression on resident astrocytes and microglia within infected sites. Upon infection, Fas- and FasL-deficient mice (lpr and gld) were partially protected from encephalitis with a decreased morbidity and mortality compared to WT mice. Fas/FasL deficiency promoted cell-mediated immunity within the CNS. Fas receptor stimulation abrogated HSV-1 induced activation and inflammatory reactions in microglia from WT mice, while lack of Fas or FasL led to a more pronounced activation of monocytes and microglia and also to an enhanced differentiation of these cells into a pro-inflammatory M1 phenotype. Furthermore, the specific immune system was more efficient in Fas- and FasL-deficient mice with significantly higher numbers of infiltrating HSV-1-specific cytotoxic T cells in the brain. Our data indicate that the Fas/FasL pathway leads to excessive neuroinflammation during HSV-1 infection, which is associated with a diminished anti-viral response and an excessive neuroinflammation.

Activation of Cytotoxic Lymphocytes and Presence of Regulatory T Cells in the Trachea of Non-Vaccinated and Vaccinated Chickens as a Recall to an Infectious Laryngotracheitis Virus (ILTV) Challenge

While the protective efficacy of the infectious laryngotracheitis virus (ILTV) vaccines is well established, little is known about which components of the immune response are associated with effective resistance and vaccine protection. Early studies have pointed to the importance of the T cell-mediated immune responses. This study aimed to evaluate the activation of cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells and to quantify the presence of regulatory T cells (Tregs) in the larynx-trachea of chickens vaccinated with chicken embryo origin (CEO), tissue culture origin (TCO) and recombinant Herpesvirus of Turkey-laryngotracheitis (rHVT-LT) vaccines after challenge. Our results indicated that CEO vaccine protection was characterized by early CTLs and activated CTLs enhanced responses. TCO and rHVT-LT protection were associated with a moderate increase in resting and activated CTLs followed by an enhanced NK cell response. Tregs increase was only detected in the non-vaccinated challenged group, probably to support healing of the severe trachea epithelial damage. Taken together, our results revealed main differences in the cellular immune responses elicited by CEO, TCO, and rHVT-LT vaccination in the upper respiratory tract after challenge, and that activated CTLs rather than NK cells play a main role in vaccine protection.

Virus-Host Interactions in Foot-and-Mouth Disease Virus Infection

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals, which has been regarded as a persistent challenge for the livestock industry in many countries. Foot-and-mouth disease virus (FMDV) is the etiological agent of FMD that can spread rapidly by direct and indirect transmission. FMDV is internalized into host cell by the interaction between FMDV capsid proteins and cellular receptors. When the virus invades into the cells, the host antiviral system is quickly activated to suppress the replication of the virus and remove the virus. To retain fitness and host adaptation, various viruses have evolved multiple elegant strategies to manipulate host machine and circumvent the host antiviral responses. Therefore, identification of virus-host interactions is critical for understanding the host defense against virus infections and the pathogenesis of the viral infectious diseases. This review elaborates on the virus-host interactions during FMDV infection to summarize the pathogenic mechanisms of FMD, and we hope it can provide insights for designing effective vaccines or drugs to prevent and control the spread of FMD and other diseases caused by picornaviruses.

Viral Infections and Systemic Lupus Erythematosus: New Players in an Old Story

A causal link between viral infections and autoimmunity has been studied for a long time and the role of some viruses in the induction or exacerbation of systemic lupus erythematosus (SLE) in genetically predisposed patients has been proved. The strength of the association between different viral agents and SLE is variable. Epstein-Barr virus (EBV), parvovirus B19 (B19V), and human endogenous retroviruses (HERVs) are involved in SLE pathogenesis, whereas other viruses such as Cytomegalovirus (CMV) probably play a less prominent role. However, the mechanisms of viral-host interactions and the impact of viruses on disease course have yet to be elucidated. In addition to classical mechanisms of viral-triggered autoimmunity, such as molecular mimicry and epitope spreading, there has been a growing appreciation of the role of direct activation of innate response by viral nucleic acids and epigenetic modulation of interferon-related immune response. The latter is especially important for HERVs, which may represent the molecular link between environmental triggers and critical immune genes. Virus-specific proteins modulating interaction with the host immune system have been characterized especially for Epstein-Barr virus and explain immune evasion, persistent infection and self-reactive B-cell "immortalization". Knowledge has also been expanding on key viral proteins of B19-V and CMV and their possible association with specific phenotypes such as antiphospholipid syndrome. This progress may pave the way to new therapeutic perspectives, including the use of known or new antiviral drugs, postviral immune response modulation and innate immunity inhibition. We herein describe the state-of-the-art knowledge on the role of viral infections in SLE, with a focus on their mechanisms of action and potential therapeutic targets.