Epstein-Barr virus co-opts TFIIH component XPB to specifically activate essential viral lytic promoters

Repurposing Licensed Drugs with Activity Against Epstein-Barr Virus for Treatment of Multiple Sclerosis: A Systematic Approach

BACKGROUND

Epstein-Barr virus (EBV) is implicated as a necessary factor in the development of multiple sclerosis (MS) and may also be a driver of disease activity. Although it is not clear whether ongoing viral replication is the driver for MS pathology, MS researchers have considered the prospect of using drugs with potential efficacy against EBV in the treatment of MS. We have undertaken scientific and lived experience expert panel reviews to shortlist existing licensed therapies that could be used in later-stage clinical trials in MS.

METHODS

A list of therapies with anti-EBV effects was developed from existing reviews. A detailed review of pre-clinical and clinical data was undertaken to assess these candidates for potential usefulness and possible harm in MS. A 'drug-CV' and a plain language version focusing on tolerability aspects was created for each candidate. We used validated criteria to score each candidate with an international scientific panel and people living with MS.

RESULTS

A preliminary list of 11 drug candidates was generated. Following review by the scientific and lived experience expert panels, six yielded the same highest score. A further review by the expert panel shortlisted four drugs (famciclovir, tenofovir alafenamide, maribavir and spironolactone) deemed to have the best balance of efficacy, safety and tolerability for use in MS.

CONCLUSIONS

Scientific and lived experience expert panel review of anti-EBV therapies selected four candidates with evidence for efficacy against EBV and acceptable safety and tolerability for potential use in phase III clinical trials for MS.

Identifying the key regulators orchestrating Epstein-Barr virus reactivation

Epstein-Barr virus (EBV) infects more than 90% of the human population worldwide and establishes lifelong infection in hosts by switching between latent and lytic infection. EBV latency can be reactivated under appropriate conditions, leading to expression of the viral lytic genes and production of infectious progeny viruses. EBV reactivation involves crosstalk between various factors and signaling pathways, and the subsequent complicated virus-host interplays determine whether EBV continues to propagate. However, the detailed mechanisms underlying these processes remain unclear. In this review, we summarize the critical factors regulating EBV reactivation and the associated mechanisms. This encompasses the transcription and post-transcriptional regulation of immediate-early (IE) genes, the functions of viral factors on viral DNA replication and progeny virus production, the mechanisms through which viral proteins disrupt and inhibit the host's innate immune response, and the host factors that modulate EBV reactivation. Finally, we explore the potential applications of novel technologies in studying EBV reactivation, providing novel insights into the investigation of mechanisms governing EBV reactivation and the development of anti-EBV therapeutic strategies.

Curcumin derivative C210 induces Epstein-Barr virus lytic cycle and inhibits virion production by disrupting Hsp90 function

Lytic induction therapy was devised to selectively combat malignancies associated with Epstein-Barr virus (EBV) by triggering viral reactivation from latency. At present, the major challenges of lytic induction therapy are to maximize reactivating efficiencies and meanwhile minimize infectious virion production. C210, a novel curcumin derivative with potent Hsp90 inhibitory activity, was explored for EBV-reactivating and virion-producing effects in EBV-positive nasopharyngeal carcinoma (NPC) and gastric carcinoma (GC) cell lines. And the molecular mechanisms underlying these effects were determined. Follow C210 treatment, EBV lytic RNAs and proteins were upregulated, but infectious virions were not produced. Knockdown of heat shock protein 90 (Hsp90) induced expression of lytic RNAs and proteins, and diminished C210-driven EBV lytic induction. Pretreatment with an X box binding protein 1 (XBP1) inhibitor reduced C210-induced EBV lytic RNA. Furthermore, we demonstrated that C210 inhibited the binding of Hsp90 with its clients, signal transducer and activator of transcription 3 (STAT3) and xeroderma pigmentosum group B-complementing protein (XPB), which subsequently promoted their proteasomal degradation. Degradation of STAT3 by C210 enhanced the EBV-reactivating and anticancer capacity of suberoylanilide hydroxamic acid (SAHA). Depletion of XPB blocked SAHA-induced expression of late viral genes and production of infectious virions. These results elucidate a novel Hsp90 inhibitor targeting EBV lytic phase and extend the research on lytic induction strategy, which may offer reference value in the treatment of EBV-positive malignancies.

Identification of CD8 T-cell dysfunction associated with symptoms in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and Long COVID and treatment with a nebulized antioxidant/anti-pathogen agent in a retrospective case series

Background

Patients with post-acute sequelae of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection (PASC, i.e., Long COVID) have a symptom complex highly analogous to many features of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), suggesting they may share some aspects of pathogenesis in these similar disorders. ME/CFS is a complex disease affecting numerous organ systems and biological processes and is often preceded by an infection-like episode. It is postulated that the chronic manifestations of illness may result from an altered host response to infection or inability to resolve inflammation, as is being reported in Long COVID. The immunopathogenesis of both disorders is still poorly understood. Here, we show data that suggest Long COVID and ME/CFS may be due to an aberrant response to an immunological trigger-like infection, resulting in a dysregulated immune system with CD8 T-cell dysfunction reminiscent of some aspects of T-cell clonal exhaustion, a phenomenon associated with oxidative stress. As there is an urgent need for diagnostic tools and treatment strategies for these two related disabling disorders, here, in a retrospective case series, we have also identified a potential nebulized antioxidant/anti-pathogen treatment that has evidence of a good safety profile. This nebulized agent is comprised of five ingredients previously reported individually to relieve oxidative stress, attenuate NF-κB signaling, and/or to act directly to inhibit pathogens, including viruses. Administration of this treatment by nebulizer results in rapid access of small doses of well-studied antioxidants and agents with anti-pathogen potential to the lungs; components of this nebulized agent are also likely to be distributed systemically, with potential to enter the central nervous system.

Methods

and Findings: We conducted an analysis of CD8 T-cell function and severity of symptoms by self-report questionnaires in ME/CFS, Long COVID and healthy controls. We developed a CD8 T-cell functional assay, assessing CD8 T-cell dysfunction by intracellular cytokine staining (ICS) in a group of ME/CFS (n = 12) and Long COVID patients (n = 8), comparing to healthy controls (HC) with similar age and sex (n = 10). Magnet-enriched fresh CD8 T-cells in both patient groups had a significantly diminished capacity to produce both cytokines, IFNγ or TNFα, after PMA stimulation when compared to HC. The symptom severity questionnaire showed similar symptom profiles for the two disorders. Fortuitously, through a retrospective case series, we were able to examine the ICS and questionnaire data of 4 ME/CFS and 4 Long COVID patients in conjunction with their treatment (3-15 months). In parallel with the treatment pursued electively by participants in this retrospective case series, there was an increase in CD8 T-cell IFNγ and TNFα production and a decrease in overall self-reported symptom severity score by 54%. No serious treatment-associated side effects or laboratory anomalies were noted in these patients.

Conclusions

Here, in this small study, we present two observations that appear potentially fundamental to the pathogenesis and treatment of Long COVID and ME/CFS. The first is that both disorders appear to be characterized by dysfunctional CD8 T-cells with severe deficiencies in their abilities to produce IFNγ and TNFα. The second is that in a small retrospective Long COVID and ME/CFS case series, this immune dysfunction and patient health improved in parallel with treatment with an immunomodulatory, antioxidant pharmacological treatment with anticipated anti-pathogen activity. This work provides evidence of the potential utility of a biomarker, CD8 T-cell dysfunction, and suggests the potential for benefit from a new nebulized antioxidant/anti-pathogen treatment. These immune biomarker data may help build capacity for improved diagnosis and tracking of treatment outcomes during clinical trials for both Long COVID and ME/CFS while providing clues to new treatment avenues that suggest potential efficacy for both conditions.

Better late than never: A unique strategy for late gene transcription in the beta- and gammaherpesviruses

During lytic replication, herpesviruses express their genes in a temporal cascade culminating in expression of "late" genes. Two subfamilies of herpesviruses, the beta- and gammaherpesviruses (including human herpesviruses cytomegalovirus, Epstein-Barr virus, and Kaposi's sarcoma-associated herpesvirus), use a unique strategy to facilitate transcription of late genes. They encode six essential viral transcriptional activators (vTAs) that form a complex at a subset of late gene promoters. One of these vTAs is a viral mimic of host TATA-binding protein (vTBP) that recognizes a strikingly minimal cis-acting element consisting of a modified TATA box with a TATTWAA consensus sequence. vTBP is also responsible for recruitment of cellular RNA polymerase II (Pol II). Despite extensive work in the beta/gammaherpesviruses, the function of the other five vTAs remains largely unknown. The vTA complex and Pol II assemble on the promoter into a viral preinitiation complex (vPIC) to facilitate late gene transcription. Here, we review the properties of the vTAs and the promoters on which they act.

The viral packaging motor potentiates Kaposi's sarcoma-associated herpesvirus gene expression late in infection

β- and γ-herpesviruses transcribe their late genes in a manner distinct from host transcription. This process is directed by a complex of viral transcriptional activator proteins that hijack cellular RNA polymerase II and an unknown set of additional factors. We employed proximity labeling coupled with mass spectrometry, followed by CRISPR and siRNA screening to identify proteins functionally associated with the Kaposi's sarcoma-associated herpesvirus (KSHV) late gene transcriptional complex. These data revealed that the catalytic subunit of the viral DNA packaging motor, ORF29, is both dynamically associated with the viral transcriptional activator complex and potentiates gene expression late in infection. Through genetic mutation and deletion of ORF29, we establish that its catalytic activity potentiates viral transcription and is required for robust accumulation of essential late proteins during infection. Thus, we propose an expanded role for ORF29 that encompasses its established function in viral packaging and its newly discovered contributions to viral transcription and late gene expression in KSHV.

Epstein-Barr virus: Biology and clinical disease

Epstein-Barr virus (EBV) is a ubiquitous, oncogenic virus that is associated with a number of different human malignancies as well as autoimmune disorders. The expression of EBV viral proteins and non-coding RNAs contribute to EBV-mediated disease pathologies. The virus establishes life-long latency in the human host and is adept at evading host innate and adaptive immune responses. In this review, we discuss the life cycle of EBV, the various functions of EBV-encoded proteins and RNAs, the ability of the virus to activate and evade immune responses, as well as the neoplastic and autoimmune diseases that are associated with EBV infection in the human population.

[Tax, the puppet master of HTLV-1 transcription]

Retroviruses exploit the RNA polymerase II transcription machinery for the transcription of their genes. This is the case of Human T-lymphotropic virus type 1 (HTLV-1), the retrovirus responsible for adult T-cell leukemia and for various inflammatory diseases. HTLV-1 transcription is under the control of the viral protein Tax, which exhibits an original mode of action since it does not rely on direct promoter interaction but rather on the recruitment of various cellular factors and cofactors of transcription. The factors that Tax recruits are involved in the initial step of promoter activation but also in the subsequent steps of the transcription process itself. This review describes this particular mechanism of viral transcription, from the epigenetic release of the viral promoter to the elongation of the neosynthesized viral silencing transcripts.

Molecular Basis of Epstein-Barr Virus Latency Establishment and Lytic Reactivation

Epstein–Barr virus (EBV) is a causative agent of infectious mononucleosis and several types of cancer. Like other herpesviruses, it establishes an asymptomatic, life-long latent infection, with occasional reactivation and shedding of progeny viruses. During latency, EBV expresses a small number of viral genes, and exists as an episome in the host–cell nucleus. Expression patterns of latency genes are dependent on the cell type, time after infection, and milieu of the cell (e.g., germinal center or peripheral blood). Upon lytic induction, expression of the viral immediate-early genes, BZLF1 and BRLF1, are induced, followed by early gene expression, viral DNA replication, late gene expression, and maturation and egress of progeny virions. Furthermore, EBV reactivation involves more than just progeny production. The EBV life cycle is regulated by signal transduction, transcription factors, promoter sequences, epigenetics, and the 3D structure of the genome. In this article, the molecular basis of EBV latency establishment and reactivation is summarized.

Regulation of Promoter Proximal Pausing of RNA Polymerase II in Metazoans

Regulation of transcription is a tightly choreographed process. The establishment of RNA polymerase II promoter proximal pausing soon after transcription initiation and the release of Pol II into productive elongation are key regulatory processes that occur in early elongation. We describe the techniques and tools that have become available for the study of promoter proximal pausing and their utility for future experiments. We then provide an overview of the factors and interactions that govern a multipartite pausing process and address emerging questions surrounding the mechanism of RNA polymerase II's subsequent advancement into the gene body. Finally, we address remaining controversies and future areas of study.

Aberrant Splicing Events and Epigenetics in Viral Oncogenomics: Current Therapeutic Strategies

Global cancer incidence and mortality are on the rise. Although cancer is fundamentally a non-communicable disease, a large number of cancers are known to have a viral aetiology. A high burden of infectious agents (Human immunodeficiency virus (HIV), human papillomavirus (HPV), hepatitis B virus (HBV)) in certain Sub-Saharan African countries drives the rates of certain cancers. About one-third of all cancers in Africa are attributed to infection. Seven viruses have been identified with carcinogenic characteristics, namely the HPV, HBV, Hepatitis C virus (HCV), Epstein–Barr virus (EBV), Human T cell leukaemia virus 1 (HTLV-1), Kaposi’s Sarcoma Herpesvirus (KSHV), and HIV-1. The cellular splicing machinery is compromised upon infection, and the virus generates splicing variants that promote cell proliferation, suppress signalling pathways, inhibition of tumour suppressors, alter gene expression through epigenetic modification, and mechanisms to evade an immune response, promoting carcinogenesis. A number of these splice variants are specific to virally-induced cancers. Elucidating mechanisms underlying how the virus utilises these splice variants to maintain its latent and lytic phase will provide insights into novel targets for drug discovery. This review will focus on the splicing genomics, epigenetic modifications induced by and current therapeutic strategies against HPV, HBV, HCV, EBV, HTLV-1, KSHV and HIV-1.