A pyridinium­type fullerene derivative suppresses primary effusion lymphoma cell viability via the downregulation of the Wnt signaling pathway through the destabilization of ß­catenin.

Primary effusion lymphoma (PEL) is defined as a rare subtype of non­Hodgkin's B cell lymphoma, which is caused by Kaposi's sarcoma­associated herpesvirus (KSHV) in immunosuppressed patients. PEL is an aggressive type of lymphoma and is frequently resistant to conventional chemotherapeutics. Therefore, the discovery of novel drug candidates for the treatment of PEL is of utmost importance. In order to discover potential novel anti­tumor compounds against PEL, the authors previously developed a pyrrolidinium­type fullerene derivative, 1,1,1',1'­tetramethyl [60]fullerenodipyrrolidinium diiodide (derivative #1), which induced the apoptosis of PEL cells via caspase­9 activation. In the present study, the growth inhibitory effects of pyrrolidinium­type (derivatives #1 and #2), pyridinium­type (derivatives #3 and #5 to #9) and anilinium­type fullerene derivatives (derivative #4) against PEL cells were evaluated. This analysis revealed a pyridinium­type derivative (derivative #5; 3­â€‹5'­(etho xycarbonyl)­1',5'­dihydro­2'H­[5,6]fullereno­C60­Ih­[1,9­c]pyrrol­2'­yl]­1­methylpyridinium iodide), which exhibited antitumor activity against PEL cells via the downregulation of Wnt/ß­catenin signaling. Derivative #5 suppressed the viability of KSHV­infected PEL cells compared with KSHV­uninfected B­lymphoma cells. Furthermore, derivative #5 induced the destabilization of ß­catenin and suppressed ß­catenin­TCF4 transcriptional activity in PEL cells. It is known that the constitutive activation of Wnt/ß­catenin signaling is essential for the growth of KSHV­infected cells. The Wnt/ß­catenin activation in KSHV­infected cells is mediated by KSHV latency­associated nuclear antigen (LANA). The data demonstrated that derivative #5 increased ß­catenin phosphorylation, which resulted in ß­catenin polyubiquitination and subsequent degradation. Thus, derivative #5 overcame LANA­mediated ß­catenin stabilization. Furthermore, the administration of derivative #5 suppressed the development of PEL cells in the ascites of SCID mice with tumor xenografts derived from PEL cells. On the whole, these findings provide evidence that the pyridinium­type fullerene derivative #5 exhibits antitumor activity against PEL cells in vitro and in vivo. Thus, derivative #5 may be utilized as a novel therapeutic agent for the treatment of PEL.

25-Hydroxycholesterol Inhibits Kaposi's Sarcoma Herpesvirus and Epstein-Barr Virus Infections and Activates Inflammatory Cytokine Responses.

Oncogenic gammaherpesviruses express viral products during latent and lytic infection that block the innate immune response. Previously, we found that Kaposi's sarcoma herpesvirus (KSHV/human herpesvirus-8) viral microRNAs (miRNAs) downregulate cholesterol biogenesis, and we hypothesized that this prevents the production of 25-hydroxycholesterol (25HC), a cholesterol derivative. 25HC blocks KSHV de novo infection of primary endothelial cells at a postentry step and decreases viral gene expression of LANA (latency-associated nuclear antigen) and RTA. Herein we expanded on this observation by determining transcriptomic changes associated with 25HC treatment of primary endothelial cells using RNA sequencing (RNA-Seq). We found that 25HC treatment inhibited KSHV gene expression and induced interferon-stimulated genes (ISGs) and several inflammatory cytokines (interleukin 8 [IL-8], IL-1α). Some 25HC-induced genes were partially responsible for the broadly antiviral effect of 25HC against several viruses. Additionally, we found that 25HC inhibited infection of primary B cells by a related oncogenic virus, Epstein-Barr virus (EBV/human herpesvirus-4) by suppressing key viral genes such as LMP-1 and inducing apoptosis. RNA-Seq analysis revealed that IL-1 and IL-8 pathways were induced by 25HC in both primary endothelial cells and B cells. We also found that the gene encoding cholesterol 25-hydroxylase (CH25H), which converts cholesterol to 25HC, can be induced by type I interferon (IFN) in human B cell-enriched peripheral blood mononuclear cells (PBMCs). We propose a model wherein viral miRNAs target the cholesterol pathway to prevent 25HC production and subsequent induction of antiviral ISGs. Together, these results answer some important questions about a widely acting antiviral (25HC), with implications for multiple viral and bacterial infections. IMPORTANCE A cholesterol derivative, 25-hydroxycholesterol (25HC), has been demonstrated to inhibit infections from widely different bacteria and viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, its mechanism of activity is still not fully understood. In this work, we look at gene expression changes in the host and virus after 25HC treatment to find clues about its antiviral activity. We likewise demonstrate that 25HC is also antiviral against EBV, a common cancer-causing virus. We compared our results with previous data from antiviral screening assays and found the same pathways resulting in antiviral activity. Together, these results bring us closer to understanding how a modified form of cholesterol works against several viruses.

Hesperetin inhibits KSHV reactivation and is reversed by HIF1α overexpression.

Kaposi's sarcoma-associated herpesvirus (KSHV), an oncogenic virus, has two life cycle modes: the latent and lytic phases. KSHV lytic reactivation is important for both viral propagation and KSHV-induced tumorigenesis. The KSHV replication and transcription activator (RTA) protein is essential for lytic reactivation. Hesperetin, a citrus polyphenolic flavonoid, has antioxidant, anti-inflammatory, hypolipidemic, cardiovascular and anti-tumour effects. However, the effects of hesperetin on KSHV replication and KSHV-induced tumorigenesis have not yet been reported. Here, we report that hesperetin induces apoptotic cell death in BCBL-1 cells in a dose-dependent manner. Hesperetin inhibits KSHV reactivation and reduces the production of progeny virus from KSHV-harbouring cells. We also confirmed that HIF1α promotes the RTA transcriptional activities and lytic cycle-refractory state of KSHV-infected cells. Hesperetin suppresses HIF1α expression to inhibit KSHV lytic reactivation. These results suggest that hesperetin may represent a novel strategy for the treatment of KSHV infection and KSHV-associated lymphomas.

Recent Advances in Developing Treatments of Kaposi's Sarcoma Herpesvirus-Related Diseases.

Kaposi-sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV-8) is the causative agent of several malignancies, including Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD). Active KSHV replication has also been associated with a pathological condition called KSHV inflammatory cytokine syndrome (KICS), and KSHV may play a role in rare cases of post-transplant polyclonal lymphoproliferative disorders. Several commonly used herpesviral DNA polymerase inhibitors are active against KSHV in tissue culture. Unfortunately, they are not always efficacious against KSHV-induced diseases. To improve the outcome for the patients, new therapeutics need to be developed, including treatment strategies that target either viral proteins or cellular pathways involved in tumor growth and/or supporting the viral life cycle. In this review, we summarize the most commonly established treatments against KSHV-related diseases and review recent developments and promising new compounds that are currently under investigation or on the way to clinical use.

Nitric oxide is induced and required for efficient Kaposi's sarcoma-associated herpesvirus lytic replication.

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus associated with several human malignancies. KSHV lytic replication promotes the spread of infection and progression of KSHV-associated malignancies; however, the mechanism regulating KSHV lytic replication remains unclear. In this study, we investigated the role of nitric oxide (NO) in KSHV lytic replication. In the TREx BCBL1-RTA KSHV lytic replication cell system, induction of KSHV lytic replication increased intracellular and extracellular NO. Chemical inhibition of NO production resulted in a lower level of KSHV lytic replication as shown by a reduced level of infectious virions, and decreased levels of viral lytic transcripts and proteins. In a second KSHV lytic replication system of iSLK-RGB-BAC16 cells, we confirmed that KSHV lytic replication increased NO production. Chemical inhibition of NO production resulted in reduced numbers of cells expressing enhanced green fluorescent protein and blue fluorescent protein, two reporters that closely track the expression of KSHV early and late genes, respectively. Consistent with these results, inhibition of NO production resulted in reduced levels of infectious virions, and viral lytic transcripts and proteins. Importantly, exogenous addition of a NO donor was sufficient to enhance the full KSHV lytic replication program. These results demonstrate that NO is required for efficient KSHV lytic replication, and NO plays a crucial role in the KSHV life cycle and KSHV-induced malignancies.

SARS-CoV-2 proteins and anti-COVID-19 drugs induce lytic reactivation of an oncogenic virus.

An outbreak of the novel coronavirus SARS-CoV-2, the causative agent of Coronavirus Disease-2019 (COVID-19), a respiratory disease, has infected almost one hundred million people since the end of 2019, killed over two million, and caused worldwide social and economic disruption. Because the mechanisms of SARS-CoV-2 infection of host cells and its pathogenesis remain largely unclear, there are currently no antiviral drugs with proven efficacy. Besides severe respiratory and systematic symptoms, several comorbidities increase risk of fatal disease outcome. Therefore, it is required to investigate the impacts of COVID-19 on pre-existing diseases of patients, such as cancer and other infectious diseases. In the current study, we report that SARS-CoV-2 encoded proteins and some currently used anti-COVID-19 drugs are able to induce lytic reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV), one of major human oncogenic viruses, through manipulation of intracellular signaling pathways. Our data indicate that those KSHV + patients especially in endemic areas exposure to COVID-19 or undergoing the treatment may have increased risks to develop virus-associated cancers, even after they have fully recovered from COVID-19.

KSHV-specific antivirals targeting the protein-DNA interaction of the latency-associated nuclear antigen.

The Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic human herpesviruses that is responsible for cancer, especially in immunosuppressed people, such as patients with AIDS. So far, there are no KSHV-specifc antiviral agents available. In this review, we provide an overview on one particular target-centered approach toward novel anti-KSHV drugs focusing on interfering with the molecular functions of the latency-associated nuclear antigen (LANA). This review focuses on attempts to interfere with the LANA-DNA interaction mediated by the C-terminal domain. We describe the drug discovery approaches chosen for this endeavor as well as molecular structures that were identified in this innovative concept toward novel and KSHV-specific antiherpesviral agents.

The anti-malaria agent artesunate exhibits cytotoxic effects in primary effusion lymphoma.

Primary effusion lymphoma (PEL), caused by Kaposi's sarcoma-associated herpesvirus (KSHV), presents as a lymphomatous effusion in body cavities and has a poor prognosis. The anti-malaria drug, artesunate, possesses anti-neoplastic potential. Therefore, we aimed to investigate its effect on KSHV-infected PEL cell lines. Artesunate inhibited cell growth and viability of PEL cells, but its effect on peripheral blood mononuclear cells was less pronounced. Artesunate induced G1 phase arrest by downregulating cyclin D1/D2, CDK2/6 and c-Myc. Artesunate increased reactive oxygen species and DNA damage, but did not affect the expression of latent and lytic genes of KSHV. It exhibited cytotoxicity through caspase-dependent and -independent pathways and reduced Bcl-xL, survivin, XIAP and c-IAP1/2 levels. Furthermore, artesunate suppressed NF-κB and AP-1 by inhibiting IκB kinase and IκBα phosphorylation as well as JunB expression. Finally, artesunate treatment attenuated PEL development in mice. Our data support that artesunate is a potential drug for PEL treatment.

A novel mathematical model of AIDS-associated Kaposi's sarcoma: Analysis and optimal control.

Kaposi's sarcoma (KS) has been the most common HHV-8 virus-induced neoplasm associated with HIV-1 infection. Although the standard KS therapy has not changed in 20 years, not all cases of KS will respond to the same therapy. The goal of current AIDS-KS treatment modalities is to reconstitute the immune system and suppress HIV-1 replication, but newer treatment modalities are on horizon. There are very few mathematical models that have included HIV-1 viral load (VL) measures, despite VL being a key determinant of treatment outcome. Here we introduce a mathematical model that consolidates the effect of both HIV-1 and HHV-8 VL on KS tumor progression by incorporating low or high VLs into the proliferation terms of the immune cell populations. Regulation of HIV-1/HHV-8 VL and viral reservoir cells is crucial for restoring a patient to an asymptomatic stage. Therefore, an optimal control strategy given by a combined antiretroviral therapy (cART) is derived. The results indicate that the drug treatment strategies are capable of removing the viral reservoirs faster and consequently, the HIV-1 and KS tumor burden is reduced. The predictions of the mathematical model have the potential to offer more effective therapeutic interventions based on viral and virus-infected cell load and support new studies addressing the superiority of VL over CD4+ T-cell count in HIV-1 pathogenesis.

Cytokine-Targeted Therapeutics for KSHV-Associated Disease.

Kaposi's sarcoma-associated herpesvirus (KSHV) also known as human herpesvirus 8 (HHV-8), is linked to several human malignancies including Kaposi sarcoma (KS), primary effusion lymphoma (PEL), multicentric Castleman's disease (MCD) and recently KSHV inflammatory cytokine syndrome (KICS). As with other diseases that have a significant inflammatory component, current therapy for KSHV-associated disease is associated with significant off-target effects. However, recent advances in our understanding of the pathogenesis of KSHV have produced new insight into the use of cytokines as potential therapeutic targets. Better understanding of the role of cytokines during KSHV infection and tumorigenesis may lead to new preventive or therapeutic strategies to limit KSHV spread and improve clinical outcomes. The cytokines that appear to be promising candidates as KSHV antiviral therapies include interleukins 6, 10, and 12 as well as interferons and tumor necrosis factor-family cytokines. This review explores our current understanding of the roles that cytokines play in promoting KSHV infection and tumorigenesis, and summarizes the current use of cytokines as therapeutic targets in KSHV-associated diseases.

Hit-to-lead optimization of a latency-associated nuclear antigen inhibitor against Kaposi's sarcoma-associated herpesvirus infections.

The Latency-associated nuclear antigen (LANA) plays a central role for the latent persistence of the Kaposi's Sarcoma Herpesvirus (KSHV) in the human host and helps to establish lifelong infections. Herein, we report our efforts towards hit-to-lead generation starting from a previously discovered LANA-DNA inhibitor. By tethering the viral genome to the host nucleosomes, LANA ensures the segregation and persistence of the viral DNA during mitosis. LANA is also required for the replication of the latent viral episome during the S phase of the cell cycle. We aim to inhibit the interaction between LANA and the viral genome to prevent the latent persistence of KSHV in the host organism. Medicinal chemistry-driven optimization studies and structure-activity-relationship investigation led to the discovery of an improved LANA inhibitor. The functional activity of our compounds was evaluated using a fluorescence polarization (FP)-based interaction inhibition assay and electrophoretic mobility shift assay (EMSA). Even though a crystal structure of the ligand protein complex was not available, we successfully conducted hit optimization toward a low micromolar protein-nucleic acid-interaction inhibitor. Additionally, we applied STD-NMR studies to corroborate target binding and to gain insights into the binding orientation of our most potent inhibitor, providing opportunities for further rational design of more efficient LANA-targeting anti KSHV agents in future studies.

Pemetrexed inhibits Kaposi's sarcoma-associated herpesvirus replication through blocking dTMP synthesis.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman's disease. In immunocompromised patients, KSHV infection is capable of causing severe and fatal diseases. Current antiviral treatments for KSHV infections consist mostly of nucleoside analogs, all of which target viral polymerases and are associated with adverse effects and drug resistance. By screening an FDA-approved drug library, we identified pemetrexed as a potent anti-KSHV agent, with an IC50 of 90 nM. Characterization of the antiviral properties of pemetrexed revealed that it interferes with the lytic replication of viral DNA, resulting in the reduction of infectious virions. The antiviral effect of pemetrexed depends on the dTMP synthesis pathway that requires the folate-dependent enzymes. Besides, pemetrexed shows a broad spectrum of anti-herpes virus activity. Thus, our findings suggest that pemetrexed inhibits the lytic replication of KSHV DNA by blocking dTMP synthesis. Pemetrexed has the potential to be utilized as an anti-KSHV agent.

Overview of Castleman disease.

Castleman disease (CD) describes a group of at least 4 disorders that share a spectrum of characteristic histopathological features but have a wide range of etiologies, presentations, treatments, and outcomes. CD includes unicentric CD (UCD) and multicentric CD (MCD), the latter of which is divided into idiopathic MCD (iMCD), human herpes virus-8 (HHV8)-associated MCD (HHV8-MCD), and polyneuropathy, organomegaly, endocrinopathy, monoclonal plasma cell disorder, skin changes (POEMS)-associated MCD (POEMS-MCD). iMCD can be further subclassified into iMCD-thrombocytopenia, ascites, reticulin fibrosis, renal dysfunction, organomegaly (iMCD-TAFRO) or iMCD-not otherwise specified (iMCD-NOS). Advances in diagnosis, classification, pathogenesis, and therapy are substantial since the original description of UCD by Benjamin Castleman in 1954. The advent of effective retroviral therapy and use of rituximab in HHV8-MCD have improved outcomes in HHV8-MCD. Anti-interleukin-6-directed therapies are highly effective in many iMCD patients, but additional therapies are required for refractory cases. Much of the recent progress has been coordinated by the Castleman Disease Collaborative Network (CDCN), and further progress will be made by continued engagement of physicians, scientists, and patients. Progress can also be facilitated by encouraging patients to self-enroll in the CDCN's ACCELERATE natural history registry (#NCT02817997; www.CDCN.org/ACCELERATE).

Tumor Microenvironment Conditioning by Abortive Lytic Replication of Oncogenic γ-Herpesviruses.

Epstein Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) constitute the human γ-herpesviruses and two of the seven human tumor viruses. In addition to their viral oncogenes that primarily belong to the latent infection programs of these viruses, they encode proteins that condition the microenvironment. Many of these are early lytic gene products and are only expressed in a subset of infected cells of the tumor mass. In this chapter I will describe their function and the evidence that targeting them in addition to the latent oncogenes could be beneficial for the treatment of EBV- and KSHV-associated malignancies.

Discovery of Novel Latency-Associated Nuclear Antigen Inhibitors as Antiviral Agents Against Kaposi's Sarcoma-Associated Herpesvirus.

With the aim to develop novel antiviral agents against Kaposi's Sarcoma Herpesvirus (KSHV), we are targeting the latency-associated nuclear antigen (LANA). This protein plays an important role in viral genome maintenance during latent infection. LANA has the ability to tether the viral genome to the host nucleosomes and, thus, ensures latent persistence of the viral genome in the host cells. By inhibition of the LANA-DNA interaction, we seek to eliminate or reduce the load of the viral DNA in the host. To achieve this goal, we screened our in-house library using a dedicated fluorescence polarization (FP)-based competition assay, which allows for the quantification of LANA-DNA-interaction inhibition by small organic molecules. We successfully identified three different compound classes capable of disrupting this protein-nucleic acid interaction. We characterized these compounds by IC50 dose-response evaluation and confirmed the compound-LANA interaction using surface plasmon resonance (SPR) spectroscopy. Furthermore, two of the three hit scaffolds showed only marginal cytotoxicity in two human cell lines. Finally, we conducted STD-NMR competition experiments with our new hit compounds and a previously described fragment-sized inhibitor. Based on these results, future compound linking approaches could serve as a promising strategy for further optimization studies in order to generate highly potent KSHV inhibitors.

Targeting Kaposi's Sarcoma-Associated Herpesvirus ORF21 Tyrosine Kinase and Viral Lytic Reactivation by Tyrosine Kinase Inhibitors Approved for Clinical Use.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the cause of three human malignancies: Kaposi's sarcoma, primary effusion lymphoma, and the plasma cell variant of multicentric Castleman disease. Previous research has shown that several cellular tyrosine kinases play crucial roles during several steps in the virus replication cycle. Two KSHV proteins also have protein kinase function: open reading frame (ORF) 36 encodes a serine-threonine kinase, while ORF21 encodes a thymidine kinase (TK), which has recently been found to be an efficient tyrosine kinase. In this study, we explore the role of the ORF21 tyrosine kinase function in KSHV lytic replication. By generating a recombinant KSHV mutant with an enzymatically inactive ORF21 protein, we show that the tyrosine kinase function of ORF21/TK is not required for the progression of the lytic replication in tissue culture but that it is essential for the phosphorylation and activation to toxic moieties of the antiviral drugs zidovudine and brivudine. In addition, we identify several tyrosine kinase inhibitors, already in clinical use against human malignancies, which potently inhibit not only ORF21 TK kinase function but also viral lytic reactivation and the development of KSHV-infected endothelial tumors in mice. Since they target both cellular tyrosine kinases and a viral kinase, some of these compounds might find a use in the treatment of KSHV-associated malignancies.IMPORTANCE Our findings address the role of KSHV ORF21 as a tyrosine kinase during lytic replication and the activation of prodrugs in KSHV-infected cells. We also show the potential of selected clinically approved tyrosine kinase inhibitors to inhibit KSHV TK, KSHV lytic replication, infectious virion release, and the development of an endothelial tumor. Since they target both cellular tyrosine kinases supporting productive viral replication and a viral kinase, these drugs, which are already approved for clinical use, may be suitable for repurposing for the treatment of KSHV-related tumors in AIDS patients or transplant recipients.

Identification of new antiviral agents against Kaposi's sarcoma-associated herpesvirus (KSHV) by high-throughput drug screening reveals the role of histamine-related signaling in promoting viral lytic reactivation.

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several human cancers, such as Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). Current treatment options for KSHV infection and virus associated diseases are sometimes ineffective, therefore, more effectively antiviral agents are urgently needed. As a herpesvirus, lytic replication is critical for KSHV pathogenesis and oncogenesis. In this study, we have established a high-throughput screening assay by using an inducible KSHV+ cell-line, iSLK.219. After screening a compound library that consisted of 1280 Food and Drug Administration (FDA)-approved drugs, 15 hit compounds that effectively inhibited KSHV virion production were identified, most of which have never been reported with anti-KSHV activities. Interestingly, 3 of these drugs target histamine receptors or signaling. Our data further confirmed that antagonists targeting different histamine receptors (HxRs) displayed excellent inhibitory effects on KSHV lytic replication from induced iSLK.219 or BCBL-1 cells. In contrast, histamine and specific agonists of HxRs promoted viral lytic replication from induced iSLK.219 or KSHV-infected primary cells. Mechanistic studies indicated that downstream MAPK and PI3K/Akt signaling pathways were required for histamine/receptors mediated promotion of KSHV lytic replication. Direct knockdown of HxRs in iSLK.219 cells effectively blocked viral lytic gene expression during induction. Using samples from a cohort of HIV+ patients, we found that the KSHV+ group has much higher levels of histamine in their plasma and saliva than the KSHV- group. Taken together, our data have identified new anti-KSHV agents and provided novel insights into the molecular bases of host factors that contribute to lytic replication and reactivation of this oncogenic herpesvirus.

The treatment of Kaposi's sarcoma: present and future options, a review of the literature.

Kaposi's Sarcoma (KS) is an angiogenic tumor involving skin, mucosa and splanchnic organs. It is caused by Human Herpes Virus 8 (HHV8), when in the presence of other cofactors, such as an immune dysregulation. KS is particularly frequent in HIV-infected individuals. The major goals of treatment are to prevent disease progression, to reduce tumor and edema, to avoid organ compromise, and to relieve psychological stress. The importance and the high cancer risk offered by this co-infection, together with the spread of both these viruses, and the fact that angiogenesis is such an important characteristic of KS led to a lively interest in finding a definitive therapy. Most of the ongoing studies are focused on finding an application of old drugs in KS. Unfortunately, given the number of studies with different targets, it seems we are still far from completely understanding this disease and obtaining a "cure" which could be effective and safe for everyone. Further studies will hopefully offer new and definitive solutions.

Activation of NIX-mediated mitophagy by an interferon regulatory factor homologue of human herpesvirus.

Viral control of mitochondrial quality and content has emerged as an important mechanism for counteracting the host response to virus infection. Despite the knowledge of this crucial function of some viruses, little is known about how herpesviruses regulate mitochondrial homeostasis during infection. Human herpesvirus 8 (HHV-8) is an oncogenic virus causally related to AIDS-associated malignancies. Here, we show that HHV-8-encoded viral interferon regulatory factor 1 (vIRF-1) promotes mitochondrial clearance by activating mitophagy to support virus replication. Genetic interference with vIRF-1 expression or targeting to the mitochondria inhibits HHV-8 replication-induced mitophagy and leads to an accumulation of mitochondria. Moreover, vIRF-1 binds directly to a mitophagy receptor, NIX, on the mitochondria and activates NIX-mediated mitophagy to promote mitochondrial clearance. Genetic and pharmacological interruption of vIRF-1/NIX-activated mitophagy inhibits HHV-8 productive replication. Our findings uncover an essential role of vIRF-1 in mitophagy activation and promotion of HHV-8 lytic replication via this mechanism.

Remission of an HHV8-related extracavitary primary effusion lymphoma in an HIV-positive patient during antiretroviral treatment containing dolutegravir.

BACKGROUND: Human herpes virus 8 (HHV8) is the causative agent of Kaposi's sarcoma and has been associated with an increasing number of hematologic diseases such as primary effusion lymphoma (PEL) (both classic and extracavitary form), multicentric Castleman disease and the germinotropic lymphoproliferative disorder. PEL is a rare B cell non-Hodgkin lymphoma that primarily affects immunocompromised patients; aggressive chemotherapy and antiretroviral therapy (ART) with protease inhibitors have been used, with poor results. We present a case of extracavitary PEL in an HIV-infected patient, regressed after ART initiation. CASE PRESENTATION: A 42-year-old male was admitted to the emergency room because of several months of malaise, fever and progressive deterioration of the general conditions. On physical examination soft non-painful subcutaneous masses were palpable at retronuchal, retroauricolar and thoracic regions. HIV serology resulted positive: HIV plasma viremia was 782,270 copies/mL, CD4 103 cells/mL. The excision of one of the masses, metabolically active at a positron emission tomography (PET-CT) scan, revealed an HHV8-related extracavitary PEL. HHV8 plasma viremia was 44,826 copies/mL. ART with tenofovir alafenamide/emtricitabine/dolutegravir was started together with ganciclovir for cytomegalovirus chorioretinitis. The progressive disappearance of the masses was seen after 6 weeks of ART, and a PET-CT scan resulted completely negative at 3 months. After 19 months of ART the patient was in remission of PEL, HIV viremia was undetectable (< 20 copies/mL), CD4 count was 766 cells/mL and HHV8 viremia was undetectable. CONCLUSIONS: In this clinical case, the complete regression of PEL has been achieved after the immune recovery, as a consequence of ART introduction, without chemotherapy. It cannot be excluded that ganciclovir, used for the treatment of CMV chorioretinitis, may have contributed to the control of HHV8 replication. Whether to try or not a conservative approach in HIV-infected PEL patients must be carefully evaluated, considering the patient's characteristics and the prognostic factors.