Receptor modulation in viral replication: HIV, HSV, HHV-8 and HPV: same goal, different techniques to interfere with MHC-I antigen presentation

Molecular Mechanisms of Anti-Neoplastic and Immune Stimulatory Properties of Oncolytic Newcastle Disease Virus

Oncolytic viruses represent interesting anti-cancer agents with high tumor selectivity and immune stimulatory potential. The present review provides an update of the molecular mechanisms of the anti-neoplastic and immune stimulatory properties of the avian paramyxovirus, Newcastle Disease Virus (NDV). The anti-neoplastic activities of NDV include (i) the endocytic targeting of the GTPase Rac1 in Ras-transformed human tumorigenic cells; (ii) the switch from cellular protein to viral protein synthesis and the induction of autophagy mediated by viral nucleoprotein NP; (iii) the virus replication mediated by viral RNA polymerase (large protein (L), associated with phosphoprotein (P)); (iv) the facilitation of NDV spread in tumors via the membrane budding of the virus progeny with the help of matrix protein (M) and fusion protein (F); and (v) the oncolysis via apoptosis, necroptosis, pyroptosis, or ferroptosis associated with immunogenic cell death. A special property of this oncolytic virus consists of its potential for breaking therapy resistance in human cancer cells. Eight examples of this important property are presented and explained. In healthy human cells, NDV infection activates the RIG-MAVs immune signaling pathway and establishes an anti-viral state based on a strong and uninhibited interferon α,ß response. The review also describes the molecular determinants and mechanisms of the NDV-mediated immune stimulatory effects, in which the viral hemagglutinin-neuraminidase (HN) protein plays a prominent role. The six viral proteins provide oncolytic NDV with a special profile in the treatment of cancer.

Unconventional Peptide Presentation by Classical MHC Class I and Implications for T and NK Cell Activation

T cell-mediated immune recognition of peptides is initiated upon binding of the antigen receptor on T cells (TCR) to the peptide-MHC complex. TCRs are typically restricted by a particular MHC allele, while polymorphism within the MHC molecule can affect the spectrum of peptides that are bound and presented to the TCR. Classical MHC Class I molecules have a confined binding groove that restricts the length of the presented peptides to typically 8-11 amino acids. Both N- and C-termini of the peptide are bound within binding pockets, allowing the TCR to dock in a diagonal orientation above the MHC-peptide complex. Longer peptides have been observed to bind either in a bulged or zig-zag orientation within the binding groove. More recently, unconventional peptide presentation has been reported for different MHC I molecules. Here, either N- or C-terminal amino acid additions to conventionally presented peptides induced a structural change either within the MHC I molecule that opened the confined binding groove or within the peptide itself, allowing the peptide ends to protrude into the solvent. Since both TCRs on T cells and killer immunoglobulin receptors on Natural Killer (NK) cells contact the MHC I molecule above or at the periphery of the peptide binding groove, unconventionally presented peptides could modulate both T cell and NK cell responses. We will highlight recent advances in our understanding of the functional consequences of unconventional peptide presentation in cellular immunity.

Clearance of recalcitrant warts in a pediatric patient following administration of the nine-valent human papillomavirus vaccine

Verruca vulgaris is a common, benign infection of the skin and mucous membranes caused by human papillomavirus (HPV). Although many therapeutic options for warts exist, they have limited efficacy and there is no definitive cure for warts. We report the case of a 10-year-old girl with recalcitrant cutaneous warts persisting more than two years which resolved completely following vaccination with the nine-valent HPV vaccine.

From HPV Infection to Lesion Progression: The Role of HLA Alleles and Host Immunity

Persistent high-risk human papillomavirus (HPV) infection has been associated with increased risk for cervical precancerous lesions and cancer. The host's genetic variability is known to play a role in the development of cervical cancer. The human leukocyte antigen (HLA) genes are highly polymorphic and have shown to be important risk determinants of HPV infection persistence and disease progression. HLA class I and II cell surface molecules regulate the host's immune system by presenting HPV-derived peptides to T-cells. The activation of T-cell response may vary depending on the HLA allele polymorphism. The engagement of the T-cell receptor with the HPV peptide-HLA complex to create an active costimulatory signal is essential for the activation of the T-cell response. Functional peptide presentation by both HLA class I and II molecules is needed to activate efficient helper and effector T-cell responses in HPV infection recognition and clearance. Some of these HLA risk alleles could also be used as preventive tools in the detection of HPV-induced cervical lesions and cancer. These HLA alleles, together with HPV vaccines, could potentially offer possible solutions for reducing HPV-induced cervical cancer as well as other HPV-related cancers.

Chemokines encoded by herpesviruses

Viruses use diverse strategies to elude the immune system, including copying and repurposing host cytokine and cytokine receptor genes. For herpesviruses, the chemokine system of chemotactic cytokines and receptors is a common source of copied genes. Here, we review the current state of knowledge about herpesvirus-encoded chemokines and discuss their possible roles in viral pathogenesis, as well as their clinical potential as novel anti-inflammatory agents or targets for new antiviral strategies.

The role of dendritic cells in immunity against primary herpes simplex virus infections

Herpes simplex virus (HSV) is a DNA virus with tropism for infecting skin and mucosal epithelia during the lytic stages of its complex life cycle. The immune system has evolved a multitude of strategies to respond to primary HSV infections. These include rapid innate immune responses largely driven by pattern recognition systems and protective anti-viral immunity. Dendritic cells (DC) represent a versatile and heterogenic group of antigen presenting cells that are important for pathogen recognition at sites of infection and for priming of protective HSV-specific T cells. Here we will review the current knowledge on the role of DCs in the host immune response to primary HSV infection. We will discuss how DCs integrate viral cues into effective innate immune responses, will dissect how HSV infection of DCs interferes with their capacity to migrate from sites of infection to the draining lymph nodes and will outline how migratory DCs can make antigens available to lymph node resident DCs. The role of distinct DC subsets and their relevant contribution to antigen presentation on MHC class I and MHC class II molecules will be detailed in the context of T cell priming in the lymph node and the elicitation of effector function in infected tissues. An improved understanding of the fundamental mechanisms of how DCs recognize HSV, process and present its antigens to naïve and effector T cells will not only assist in the improvement of vaccine-based preventions of this important viral disease, but also serves as a paradigm to resolve basic immunological principles.

Transcriptional changes induced by bovine papillomavirus type 1 in equine fibroblasts

Bovine papillomavirus type 1 (BPV-1) and, less commonly, BPV-2 are associated with the pathogenesis of common equine skin tumors termed sarcoids. In an attempt to understand the mechanisms by which BPV-1 induces sarcoids, we used gene expression profiling as a screening tool to identify candidate genes implicated in disease pathogenesis. Gene expression profiles of equine fibroblasts transformed by BPV-1 experimentally or from explanted tumors were compared with those of control equine fibroblasts to identify genes associated with expression of BPV-1. Analysis of the microarray data identified 81 probe sets that were significantly (P < 0.01) differentially expressed between the BPV-1-transformed and control cell lines. Expression of several deregulated genes, including MMP-1, CXCL5, FRA-1, NKG7, TLR4, and the gene encoding the major histocompatibility complex class I (MHC-I) protein, was confirmed using other BPV-1-transformed cell lines. Furthermore, expression of these genes was examined using a panel of 10 sarcoids. Increased expression of MMP-1, CXCL5, FRA-1, and NKG7 was detected in a subset of tumors, and TLR4 and MHC I showed robust down-regulation in all tumors. Deregulated expression was confirmed at the protein level for MMP-1 and MHC-I. The present report identifies genes modulated by BPV-1 transformation and will help identify the molecular mechanisms involved in disease pathogenesis.

Differential immune responses and pulmonary pathophysiology are induced by two different strains of respiratory syncytial virus

In this study we performed comparisons of pulmonary responses between two different respiratory syncytial virus (RSV) antigenic subgroup A strains, A2 and Line 19. Line 19 strain induced significant dose-responsive airway hyperreactivity (AHR) in BALB/c mice at days 6 and 9 after infection, whereas the A2 strain induced no AHR at any dose. Histological examination indicated that A2 induced no goblet cell hyper/metaplasia, whereas the Line 19 induced goblet cell expansion and significant increases in gob5 and MUC5AC mRNA and protein levels in vivo. When examining cytokine responses, A2 strain induced significant interleukin (IL)-10 expression, whereas Line 19 strain induced significant IL-13 expression. When IL-13-/- mice were infected with Line 19 RSV, the AHR responses were abrogated along with gob5 gene expression. There was little difference in viral titer throughout the infection between the line 19- and A2-infected mice. However, the A2 strain grew to significantly higher titers than the Line 19 strain in HEp-2 cells in vitro. Thus, RSV Line 19-induced airway dysfunction does not correlate with viral load in vivo. These data demonstrate that different RSV strains of the same antigenic subgroup can elicit differential immune responses that impact the phenotypic expression of RSV-induced illness.

Down-regulation of MHC class I is a property common to papillomavirus E5 proteins

The E5 protein family of papillomaviruses comprises small hydrophobic proteins which are associated with the cell endomembrane compartments. The functions of the E5 proteins, particularly those of HPV, are still far from clear. We have reported that the E5 proteins of BPV-1, BPV-4, HPV-16 and HPV-6 down-regulate MHC class I, potentially helping the virus evade the host immune response. Others have described MHC class I down-regulation by HPV-2 E5. We report here that another E5 protein, HPV-83 E5, likewise down-regulates MHC class I and propose that interference with expression, assembly and/or transport of MHC class I is a common property of all E5 proteins evolved by the virus to circumvent host immunosurveillance and thus establish productive infection.

The E5 protein of BPV-4 interacts with the heavy chain of MHC class I and irreversibly retains the MHC complex in the Golgi apparatus

BPV-4 E5 inhibits transcription of the bovine MHC class I heavy chain (HC) gene, increases degradation of HC and downregulates surface expression of MHC class I by retaining the complex in the Golgi apparatus (GA). Here we report that transcription inhibition can be alleviated by interferon treatment and the degradation of HC can be reversed by treatment with inhibitors of proteasomes and lysosomes. However, the inhibition of transport of MHC class I to the cell surface is irreversible. We show that E5 is capable of physically interacting with HC. Together with the inhibition of the vacuolar ATPase (due to the interaction between E5 and 16k subunit c), the interaction between E5 and HC is likely to be responsible for retention of MHC class I in the GA. C-terminus deletion mutants of E5 are incapable of either downregulating surface MHC class I or interacting with HC, establishing that the C-terminus domain of E5 is important in the inhibition of MHC class I.

Human gammaherpesvirus cytokines and chemokine receptors

Most herpesviruses of the beta and gamma subfamilies encode homologues of cytokines and chemokine receptor- related G protein-coupled receptors (GPCRs). The roles of these proteins during normal virus replication in the infected host have not been defined in most cases, but the available data and extrapolation from what is known about the properties and functions of their cellular counterparts indicate that they play primary roles in immune evasion or in activating cellular signaling cascades that enhance virus productive replication. Cytokines and chemokine receptors specified by the two human gammaherpesviruses, human herpesvirus 8 (HHV-8) and Epstein-Barr virus (EBV), are the subject of this review. HHV-8 encodes three chemokines, a homologue of interleukin-6, and a CXCR2-related chemokine receptor, while EBV encodes a distinct GPCR and a homologue of interleukin-10. While these viral cytokines and chemokine receptors no doubt contribute to virus biology, their properties indicate that they may also be involved in virus-induced neoplasia. This review discusses the properties, functions, and likely roles of HHV-8 and EBV cytokines and chemokine receptors in relation to both virus biology and virus-associated disease.

Pleiotropic mechanisms of virus survival and persistence

Viruses are enormously efficient infectious agents that have been implicated in causing human disease for centuries. Transmission of these pathogens continues to be from one life form to another in the form of isolated cases, epidemics, and pandemics. Each infection requires entry into a susceptible host, replication, and evasion of the immune system. Viruses are successful pathogens because they target specific cells for their attack, exploit the cellular machinery, and are efficient in circumventing and/or inhibiting key cellular events required of survival. This article reviews some of the advances that have taken place in human virology in the past 50 years, emphasizing mechanisms that contribute to, and are involved with, virus survival and persistence.