Deciphering the role of Epstein-Barr virus in the pathogenesis of T and NK cell lymphoproliferations

Epstein-Barr virus (EBV) is a highly successful herpesvirus, colonizing more than 90% of the adult human population worldwide, although it is also associated with various malignant diseases. Primary infection is usually clinically silent, and subsequent establishment of latency in the memory B lymphocyte compartment allows persistence of the virus in the infected host for life. EBV is so markedly B-lymphotropic when exposed to human lymphocytes in vitro that the association of EBV with rare but distinct types of T and NK cell lymphoproliferations was quite unexpected. Whilst relatively rare, these EBV-associated T and NK lymphoproliferations can be therapeutically challenging and prognosis for the majority of patients is dismal. In this review, we summarize the current knowledge on the role of EBV in the pathogenesis of these tumours, and the implications for treatment. \ud \u

Weight fluctuation and the voice: A survey of effects from the singer\u27s perspective

Weight fluctuation and the voice: A survey of effects from the singer\u27s perspectiv

Biochemical and virologic analysis of the human cytomegalovirus encoded UL97

Human cytomegalovirus (HCMV) remains a significant cause of morbidity and mortality in immunocompromised patients. It is one of the most important opportunistic agents in the pathology of HFV, where it frequently causes sight-threatening retinitis. Currently approved antiviral drugs include ganciclovir, cidofovir and foscarnet. The HCMV UL97 gene encodes a phosphotransferase that has been shown to catalyse the initial phosphorylation of ganciclovir (GCV) to its monophosphate form, whereafter it is converted to the active triphosphate by cellular kinases. HCMV disease often necessitated long-term antiviral therapy, which in turn led to the emergence of ganciclovir resistant strains of HCMV. Mutations in the UL97 gene have been shown to impair GCV phosphorylation, thus conferring GCV resistance to HCMV and have been associated with disease progression. HCMV has been observed in almost every organ system in the body, but little information is available on the extent of UL97 mutations in the organs of chronically treated AIDS patients. A point mutation assay was employed to determine the prevalence of UL97 mutations in post mortem organs of patients who died with AIDS. The results showed that quantitative differences in resistant genotypes between organs of the same individual and between individuals occurs which has relevance to the management of patients on long term therapy for HCMV. In order to investigate functional effects of UL97 drug resistance mutations, wild type and mutant UL97 proteins were produced using a recombinant baculovirus expression system. Autophosphorylation properties of wild type and mutant UL97 were similar, while the mutations reduced ganciclovir phosphorylation to below 20% of the wild type UL97. The novel antiviral benzimidavir, inhibited autophosphorylation of wild type and mutant UL97 proteins. Enzyme kinetic analysis demonstrated benzimidavir acts by competitive inhibition of ATP binding to UL97. The mutation at codon 397, which confers resistance to benzimidavir, reduced autophosphorylation by 90%. These observations have implications for combination therapy with benzimidavir and ganciclovir

From pathobiology to targeted treatment in Epstein Barr virus related T cell and Natural Killer cell lymphoproliferative diseases

Epstein Barr virus (EBV), a gamma-1 herpesvirus, establishes a life-long latent infection in the majority of individuals worldwide. Whilst this seemingly innocuous virus is carried as an asymptomatic infection of memory B cells, EBV is paradoxically linked to two pre-malignant lymphoproliferative diseases (LPDs) and up to nine aetiologically distinct human tumours, accounting for up to 200,000 cancers per year. Although these malignancies primarily occur in B cells and epithelial cells, correlating with the natural tropism of the virus, on rare occasions EBV also infects T and NK cells leading to various pre-malignant LPDs, lymphomas and leukaemia. These conditions are often highly aggressive and are associated with hyperinflammation and organ dysfunction leading to substantial mortality. While, in recent years improvements in chemotherapy, especially asparaginase based regimens, have led to improved outcomes for some, these conditions are often intrinsically chemoresistant with allograft often providing the only curative option. In this review, we address the impact of genetic and epigenetic changes on the pathogenesis of the T/NK cell LPDs and bring together an analysis of recent clinical trials attempting to target these processes. We describe the main molecular characteristics across the range of EBV-associated T/NK cell diseases, from somatic mutations effecting epigenetic regulators seen across EBV related T/NK LPD subtypes to the marked dysregulation of the JAK-STAT-MYC axis observed in higher grade disease such as extranodal NK/T lymphoma (ENKTL). We then go on to analyse the novel therapeutic options available including immunomodulation and small molecule inhibitors. While these approaches show promise in early phase trials there is still much scope for improvement and a need to better understand the pathophysiology to design rational combination treatments

Deciphering the roles of myeloid derived suppressor cells in viral oncogenesis

Myeloid derived suppressor cells (MDSCs) are a heterogenous population of myeloid cells derived from monocyte and granulocyte precursors. They are pathologically expanded in conditions of ongoing inflammation where they function to suppress both innate and adaptive immunity. They are subdivided into three distinct subsets: monocytic (M-) MDSC, polymorphonuclear (or neutrophilic) (PMN-) MDSC and early-stage (e-) MDSC that may exhibit differential function in different pathological scenarios. However, in cancer they are associated with inhibition of the anti-tumour immune response and are universally associated with a poor prognosis. Seven human viruses classified as Group I carcinogenic agents are jointly responsible for nearly one fifth of all human cancers. These viruses represent a large diversity of species, including DNA, RNA and retroviridae. They include the human gammaherpesviruses (Epstein Barr virus (EBV) and Kaposi's Sarcoma-Associated Herpesvirus (KSHV), members of the high-risk human papillomaviruses (HPVs), hepatitis B and C (HBV, HCV), Human T cell leukaemia virus (HTLV-1) and Merkel cell polyomavirus (MCPyV). Each of these viruses encode an array of different oncogenes that perturb numerous cellular pathways that ultimately, over time, lead to cancer. A prerequisite for oncogenesis is therefore establishment of chronic infection whereby the virus persists in the host cells without being eradicated by the antiviral immune response. Although some of the viruses can directly modulate the immune response to enable persistence, a growing body of evidence suggests the immune microenvironment is modulated by expansions of MDSCs, driven by viral persistence and oncogenesis. It is likely these MDSCs play a role in loss of immune recognition and function and it is therefore essential to understand their phenotype and function, particularly given the increasing importance of immunotherapy in the modern arsenal of anti-cancer therapies. This review will discuss the role of MDSCs in viral oncogenesis. In particular we will focus upon the mechanisms thought to drive the MDSC expansions, the subsets expanded and their impact upon the immune microenvironment. Importantly we will explore how MDSCs may modulate current immunotherapies and their impact upon the success of future immune-based therapies.</p

The effects of maribavir on the autophosphorylation of ganciclovir resistant mutants of the cytomegalovirus UL97 protein

BACKGROUND: The UL97 protein kinase of human cytomegalovirus phosphorylates the antiviral drug ganciclovir and is the target of maribavir action. A detailed enzyme kinetic analysis of maribavir on the various enzymatic functions of wild type and ganciclovir resistant forms of UL97 is required. METHODS: Wild type and site directed mutant forms of the human cytomegalovirus UL97 gene product were expressed using recombinant baculoviruses and the purified products used to assess the effects of maribavir on the ganciclovir (GCV) kinase and protein kinase (PK) activities. RESULTS: Maribavir was a potent inhibitor of the autophosporylation of the wild type and all the major GCV resistant UL97 mutants analysed (M460I, H520Q, A594V and L595F) with a mean IC50 of 35 nM. The M460I mutation resulted in hypersensitivity to maribavir with an IC50 of 4.8 nM. A maribavir resistant mutant of UL97 (L397R) was functionally compromised as both a GCV kinase and a protein kinase (~ 10% of wild type levels). Enzyme kinetic experiments demonstrated that maribavir was a competitive inhibitor of ATP with a Ki of 10 nM. DISCUSSION: Maribavir is a potent competitive inhibitor of the UL97 protein kinase function and shows increased activity against the M460I GCV-resistant mutant which may impact on the management of GCV drug resistance in patients

Ocrelizumab B cell depletion has no effect on HERV RNA expression in PBMC in MS patients

Background: Epstein barr virus (EBV) infection of B cells is now understood to be one of the triggering events for the development of Multiple Sclerosis (MS), a progressive immune-mediated disease of the central nervous system. EBV infection is also linked to expression of human endogenous retroviruses (HERVs) of the HERV-W group, a further risk factor for the development of MS. Ocrelizumab is a high-potency disease-modifying treatment (DMT) for MS, which depletes B cells by targeting CD20. Objectives: We studied the effects of ocrelizumab on gene expression in peripheral blood mononuclear cells (PBMC) from paired samples from 20 patients taken prior to and 6 months after beginning ocrelizumab therapy. We hypothesised that EBV and HERV-W loads would be lower in post-treatment samples.Methods: Samples were collected in Paxgene tubes, subject to RNA extraction and Illumina paired end short read mRNA sequencing with mapping of sequence reads to the human genome using Salmon and differential gene expression compared with DeSeq2. Mapping was also performed separately to the HERV-D database of HERV sequences and the EBV reference sequence.Results: Patient samples were more strongly clustered by individual rather than disease type (relapsing/remitting or primary progressive), treatment (pre and post), age, or sex. Fourteen genes, all clearly linked to B cell function were significantly down regulated in the post treatment samples. Interestingly only one pre-treatment sample had detectable EBV RNA and there were no significant differences in HERV expression (of any group) between pre- and post-treatment samples.Conclusions: While EBV and HERV expression are clearly linked to triggering MS pathogenesis, it does not appear that high level expression of these viruses is a part of the ongoing disease process or that changes in virus load are associated with ocrelizumab treatment

Pathobiology and Treatment of Hepatitis Virus-Related Thrombocytopenia

Thrombocytopenia is a well recognized complication of infections, including those from hepatotropic viruses. Thrombocytopenia may actually be the only manifestation of vital hepatitis, which should therefore be considered in the differential diagnosis of primary immune thrombocytopenia (ITP). The mechanisms of thrombocytopenia associated with viral hepatitis vary widely depending on the specific infectious agent and the severity of liver disease. Most of the studies have described thrombocytopenia in association with chronic hepatitis C virus (HCV) infection, the most common cause of chronic infection worldwide. Studies have shown that treatment of HCV infection often results in substantial improvement or complete recovery of the thrombocytopenia. In patients with thrombocytopenia associated with HCV-related chronic liver disease, the use of eltrombopag, a thrombopoietin receptor agonist, normalizes platelet levels thereby permitting the initiation of antiviral therapy

Epstein-Barr virus-associated lymphomas

Epstein–Barr virus (EBV), originally discovered through its association with Burkitt lymphoma, is now aetiologically linked to a remarkably wide range of lymphoproliferative lesions and malignant lymphomas of B-, T- and NK-cell origin. Some occur as rare accidents of virus persistence in the B lymphoid system, while others arise as a result of viral entry into unnatural target cells. The early finding that EBV is a potent B-cell growth transforming agent hinted at a simple oncogenic mechanism by which this virus could promote lymphomagenesis. In reality, the pathogenesis of EBV-associated lymphomas involves a complex interplay between different patterns of viral gene expression and cellular genetic changes. Here we review recent developments in our understanding of EBV-associated lymphomagenesis in both the immunocompetent and immunocompromised host.This article is part of the themed issue ‘Human oncogenic viruses’.</jats:p

p53 loss promotes acute myeloid leukemia by enabling aberrant self-renewal

The p53 tumor suppressor limits proliferation in response to cellular stress through several mechanisms. Here, we test whether the recently described ability of p53 to limit stem cell self-renewal suppresses tumorigenesis in acute myeloid leukemia (AML), an aggressive cancer in which p53 mutations are associated with drug resistance and adverse outcome. Our approach combined mosaic mouse models, Cre-lox technology, and in vivo RNAi to disable p53 and simultaneously activate endogenous Kras(G12D)-a common AML lesion that promotes proliferation but not self-renewal. We show that p53 inactivation strongly cooperates with oncogenic Kras(G12D) to induce aggressive AML, while both lesions on their own induce T-cell malignancies with long latency. This synergy is based on a pivotal role of p53 in limiting aberrant self-renewal of myeloid progenitor cells, such that loss of p53 counters the deleterious effects of oncogenic Kras on these cells and enables them to self-renew indefinitely. Consequently, myeloid progenitor cells expressing oncogenic Kras and lacking p53 become leukemia-initiating cells, resembling cancer stem cells capable of maintaining AML in vivo. Our results establish an efficient new strategy for interrogating oncogene cooperation, and provide strong evidence that the ability of p53 to limit aberrant self-renewal contributes to its tumor suppressor activity