Kaposi's Sarcoma-associated Herpesvirus Research Articles

Daratumumab induces cell-mediated cytotoxicity of primary effusion lymphoma and is active against refractory disease

ABSTRACT Primary effusion lymphoma (PEL), an aggressive non-Hodgkin lymphoma caused by Kaposi sarcoma-associated herpesvirus (KSHV), lacks standard therapy and has a median survival of 10–22 months with combination chemotherapy. PEL is a tumor of plasmablast-like B cells generally expressing CD38, the target of daratumumab (Dara). Initially, we assessed PEL cells from eight patients and established that each expressed high levels of CD38 by flow cytometry. PEL cell lines were also evaluated and most had high CD38 expression. We then assessed Dara’s effects on complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC) of PEL cell lines as well as its clinical benefits on two patients with PEL. Despite high CD38 expression, Dara did not induce CDC of PEL cell lines, due in part to high levels of the complement-inhibitory proteins, CD55 and CD59. However, Dara induced significant and dose-dependent increases in ADCC, particularly in those lines with high CD38 levels. Two FDA-approved drugs, all trans-retinoic acid (ATRA) and pomalidomide (Pom), significantly increased surface CD38 levels in low-CD38 expressing PEL cell lines, resulting in increased Dara-induced ADCC. Two patients with refractory PEL were treated with Dara alone or in combination with Pom. One patient with leptomeningeal PEL had a complete response to Dara and Pom combination treatment. Others had improvement in performance status and resolution of malignant ascites with Dara alone. Together, these data support the use of Dara monotherapy or in combination with ATRA or Pom as a potential therapeutic option for PEL.

Contribution of carbohydrate-related metabolism in Herpesvirus infections

Human herpesviruses are enveloped viruses with double-stranded linear DNA genomes highly prevalent in the human population. These viruses are subdivided into three subfamilies, namely alphaherpesvirinae (herpes simplex virus type 1, HSV-1; herpes simplex virus type 2, HSV-2; and varicella-zoster virus, VZV), betaherpesvirinae (human cytomegalovirus, HCMV; human herpesvirus 6, HHV-6; and human herpesvirus 7, HHV-7) and gammaherpesvirinae (Epstein-Barr virus, EBV; and Kaposi's sarcoma-associated herpesvirus, KSHV). Besides encoding numerous molecular determinants to evade the host antiviral responses, these viruses also modulate cellular metabolic processes to promote their replication. Here, we review and discuss existing studies describing an interplay between carbohydrate metabolism and the replication cycle of herpesviruses, altogether highlighting potentially new molecular targets based on these interactions that could be used to block herpesvirus infections.

Distinctive Kaposi Sarcoma-Associated Herpesvirus Serological Profile during Acute Plasmodium falciparum Malaria Episodes

Distinctive Kaposi Sarcoma-Associated Herpesvirus Serological Profile during Acute Plasmodium falciparum Malaria Episodes

Molecular Mechanisms of Flavonoids against Tumor Gamma-Herpesviruses and Their Correlated Cancers—A Focus on EBV and KSHV Life Cycles and Carcinogenesis

Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) are cancer-causing viruses that belong to human gamma-herpesviruses. They are DNA viruses known to establish lifelong infections in humans, with the ability to develop various types of cancer. Drug resistance remains the main barrier to achieving effective therapies for viral infections and cancer. Thus, new medications with dual antiviral and anticancer actions are highly needed. Flavonoids are secondary metabolites biosynthesized by plants with diverse therapeutic effects on human health. In this review, we feature the potential role of flavonoids (flavones, protoflavones, isoflavones, flavanones, flavonols, dihydroflavonols, catechins, chalcones, anthocyanins, and other flavonoid-type compounds) in controlling gamma-herpesvirus-associated cancers by blocking EBV and KSHV infections and inhibiting the formation and growth of the correlated tumors, such as nasopharyngeal carcinoma, Burkitt's lymphoma, gastric cancer, extranodal NK/T-cell lymphoma, squamous cell carcinoma, Kaposi sarcoma, and primary effusion lymphoma. The underlying mechanisms via targeting EBV and KSHV life cycles and carcinogenesis are highlighted. Moreover, the effective concentrations or doses are emphasized.

DNA processing by the Kaposi's sarcoma-associated herpesvirus alkaline exonuclease SOX contributes to viral gene expression and infectious virion production.

Alkaline exonucleases (AE) are present in several large DNA viruses including bacteriophage λ and herpesviruses, where they play roles in viral DNA processing during genome replication. Given the genetic conservation of AEs across viruses infecting different kingdoms of life, these enzymes likely assume central roles in the lifecycles of viruses where they have yet to be well characterized. Here, we applied a structure-guided functional analysis of the bifunctional AE in the oncogenic human gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV), called SOX. In addition to identifying a preferred DNA substrate preference for SOX, we define key residues important for DNA binding and DNA processing, and how SOX activity on DNA partially overlaps with its functionally separable cleavage of mRNA. By engineering these SOX mutants into KSHV, we reveal roles for its DNase activity in viral gene expression and infectious virion production. Our results provide mechanistic insight into gammaherpesviral AE activity as well as areas of functional conservation between this mammalian virus AE and its distant relative in phage λ.

Antibody epitope profiling of the KSHV LANA protein using VirScan.

The humoral antibody response against Kaposi sarcoma-associated herpesvirus (KSHV) in infected individuals has been characterized demonstrating the latency-associated nuclear antigen (LANA) as the most antigenic KSHV protein. Despite the antigenicity of the protein, specific LANA epitopes have not been systematically characterized. Here, we utilized a bacteriophage T7 library, which displays 56-amino acid KSHV LANA peptides with 28-amino acid overlap (VirScan), to define those epitopes in LANA targeted by antibodies from a cohort of 62 sub-Saharan African Kaposi sarcoma (KS) patients and 22 KSHV-infected asymptomatic controls. Intra- and inter-patient breadth and magnitude of the anti-LANA responses were quantified at the peptide and amino acid levels. From these data, we derived a detailed epitope annotation of the entire LANA protein, with a high-resolution focus on the N- and C-termini. Overall, the central repeat region was highly antigenic, but the responses to this region could not be confidently mapped due to its high variability. The highly conserved N-terminus was targeted with low breadth and magnitude. In a minority of individuals, antibodies specific to the nuclear localization sequence and a portion of the proline-rich regions of the N-terminus were evident. In contrast, the first half of the conserved C-terminal domain was consistently targeted with high magnitude. Unfortunately, this region was not included in LANA partial C-terminal crystal structures, however, it was predicted to adopt predominantly random-coil structure. Coupled with functional and secondary structure domain predictions, VirScan revealed fine resolution epitope mapping of the N- and C-terminal domains of LANA that is consistent with previous antigenicity studies and may prove useful to correlate KSHV humoral immunity with pathogenesis.

Kaposi's sarcoma-associated herpesvirus replication and transcription activator protein activates CD274/PD-L1 gene promoter.

Kaposi's sarcoma-associated herpesvirus (KSHV) is responsible for the pathogenesis of Kaposi's sarcoma, primary effusion lymphoma, and multicentric Castleman disease. The expression of immunosuppressive genes, such as IL-10 and CD274/PD-L1 is observed during KSHV-associated pathogenesis, and the modulation of the host immune system by KSHV contributes to establishing viral persistence in the host. Understanding the mechanism that allows the virus to evade host cell immunity would be helpful in order to develop therapeutic strategies for KSHV malignancy. In this study, we show that KSHV replication and transcriptional activator (K-RTA), an essential activator of the viral lytic cycle, transactivates the CD274/PD-L1 gene promoter. Mechanistically, we demonstrate that the binding of K-RTA to the cellular specificity protein 1 (SP1) is critical for K-RTA-mediated CD274/PD-L1 promoter activation. These findings suggest that K-RTA cooperates with intracellular SP1 to activate the expression of CD274/PD-L1, which helps the virus regulate immune checkpoints to escape and survive.

Cardiovirus leader proteins retarget RSK kinases toward alternative substrates to perturb nucleocytoplasmic traffic.

Proteins from some unrelated pathogens, including small RNA viruses of the family Picornaviridae, large DNA viruses such as Kaposi sarcoma-associated herpesvirus and even bacteria of the genus Yersinia can recruit cellular p90-ribosomal protein S6 kinases (RSKs) through a common linear motif and maintain the kinases in an active state. On the one hand, pathogens' proteins might hijack RSKs to promote their own phosphorylation (direct target model). On the other hand, some data suggested that pathogens' proteins might dock the hijacked RSKs toward a third interacting partner, thus redirecting the kinase toward a specific substrate. We explored the second hypothesis using the Cardiovirus leader protein (L) as a paradigm. The L protein is known to trigger nucleocytoplasmic trafficking perturbation, which correlates with hyperphosphorylation of phenylalanine-glycine (FG)-nucleoporins (FG-NUPs) such as NUP98. Using a biotin ligase fused to either RSK or L, we identified FG-NUPs as primary partners of the L-RSK complex in infected cells. An L protein mutated in the central RSK-interaction motif was readily targeted to the nuclear envelope whereas an L protein mutated in the C-terminal domain still interacted with RSK but failed to interact with the nuclear envelope. Thus, L uses distinct motifs to recruit RSK and to dock the L-RSK complex toward the FG-NUPs. Using an analog-sensitive RSK2 mutant kinase, we show that, in infected cells, L can trigger RSK to use NUP98 and NUP214 as direct substrates. Our data therefore illustrate a novel virulence mechanism where pathogens' proteins hijack and retarget cellular protein kinases toward specific substrates, to promote their replication or to escape immunity.

IL-21 signaling promotes the establishment of KSHV infection in human tonsil lymphocytes by increasing differentiation and targeting of plasma cells.

Factors influencing Kaposi's sarcoma-associated herpesvirus (KSHV) transmission and the early stages of KSHV infection in the human immune system remain poorly characterized. KSHV is known to extensively manipulate the host immune system and the cytokine milieu, and cytokines are known to influence the progression of KSHV-associated diseases. Our previous work identified the early targeting of plasma cells for KSHV infection. In this study, we examine whether IL-21, a cytokine known to profoundly influence plasma cell fate, influences the early stages of KSHV infection in B lymphocytes. Using our unique model of ex vivo KSHV infection in tonsil lymphocytes, we investigate the influence of IL-21 supplementation, IL-21 neutralization, the distribution of IL-21 receptor on B cell subsets and IL-21 secreting T cell subsets on the establishment of KSHV infection in human B cells. We show that IL-21 signaling promotes KSHV infection by promoting both total plasma cell numbers and increasing KSHV infection in plasma cells as early as 3 days post-infection. We further demonstrate that the synergistic effect of KSHV infection and IL-21 treatment on plasma cell frequencies is due to differentiation of new plasma cells from naïve B cell precursors. We examine T cells secreting IL-21 in our tonsil specimens and determine that IL-21 producing CD8+ central memory T cells are correlated with plasma cell frequencies and KSHV targeting of plasma cells. These results demonstrate the novel finding that differentiation of new plasma cells is involved in the early stages of KSHV infection in B cells, and that IL-21 signaling can potentiate this effect thereby increasing the overall magnitude of KSHV infection at early timepoints. These results suggest that IL-21 signaling represents a host-level susceptibility factor for the establishment of KSHV infection.

The PNUTS-PP1 complex acts as an intrinsic barrier to herpesvirus KSHV gene expression and replication

Control of RNA Polymerase II (pol II) elongation is a critical component of gene expression in mammalian cells. The PNUTS-PP1 complex controls elongation rates, slowing pol II after polyadenylation sites to promote termination. The Kaposi’s sarcoma-associated herpesvirus (KSHV) co-opts pol II to express its genes, but little is known about its regulation of pol II elongation. We identified PNUTS as a suppressor of a KSHV reporter gene in a genome-wide CRISPR screen. PNUTS depletion enhances global KSHV gene expression and overall viral replication. Mechanistically, PNUTS requires PP1 interaction, binds viral RNAs downstream of polyadenylation sites, and restricts transcription readthrough of viral genes. Surprisingly, PNUTS also represses productive elongation at the 5´ ends of the KSHV reporter and the KSHV T1.4 RNA. From these data, we conclude that PNUTS’ activity constitutes an intrinsic barrier to KSHV replication likely by suppressing pol II elongation at promoter-proximal regions.

Co-Infection of the Epstein-Barr Virus and the Kaposi Sarcoma-Associated Herpesvirus.

The two human tumor viruses, Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV), have been mostly studied in isolation. Recent studies suggest that co-infection with both viruses as observed in one of their associated malignancies, namely primary effusion lymphoma (PEL), might also be required for KSHV persistence. In this review, we discuss how EBV and KSHV might support each other for persistence and lymphomagenesis. Moreover, we summarize what is known about their innate and adaptive immune control which both seem to be required to ensure asymptomatic persistent co-infection with these two human tumor viruses. A better understanding of this immune control might allow us to prepare for vaccination against EBV and KSHV in the future.

Genomic changes in Kaposi Sarcoma-associated Herpesvirus and their clinical correlates.

Kaposi sarcoma (KS), a common HIV-associated malignancy, presents a range of clinicopathological features. Kaposi sarcoma-associated herpesvirus (KSHV) is its etiologic agent, but the contribution of viral genomic variation to KS development is poorly understood. To identify potentially influential viral polymorphisms, we characterized KSHV genetic variation in 67 tumors from 1-4 distinct sites from 29 adults with advanced KS in Kampala, Uganda. Whole KSHV genomes were sequenced from 20 tumors with the highest viral load, whereas only polymorphic genes were screened by PCR and sequenced from 47 other tumors. Nine individuals harbored ≥1 tumors with a median 6-fold over-coverage of a region centering on K5 and K6 genes. K8.1 gene was inactivated in 8 individuals, while 5 had mutations in the miR-K10 microRNA coding sequence. Recurring inter-host polymorphisms were detected in K4.2 and K11.2. The K5-K6 region rearrangement breakpoints and K8.1 mutations were all unique, indicating that they arise frequently de novo. Rearrangement breakpoints were associated with potential G-quadruplex and Z-DNA forming sequences. Exploratory evaluations of viral mutations with clinical and tumor traits were conducted by logistic regression without multiple test corrections. K5-K6 over-coverage and K8.1 inactivation were tentatively correlated (p<0.001 and p = 0.005, respectively) with nodular rather than macular tumors, and with individuals that had lesions in ≤4 anatomic areas (both p≤0.01). Additionally, a trend was noted for miR-K10 point mutations and lower survival rates (HR = 4.11, p = 0.053). Two instances were found of distinct tumors within an individual sharing the same viral mutation, suggesting metastases or transmission of the aberrant viruses within the host. To summarize, KSHV genomes in tumors frequently have over-representation of the K5-K6 region, as well as K8.1 and miR-K10 mutations, and each might be associated with clinical phenotypes. Studying their possible effects may be useful for understanding KS tumorigenesis and disease progression.

Glucose and mannose analogs inhibit KSHV replication by blocking N-glycosylation and inducing the unfolded protein response.

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent for Kaposi's sarcoma (KS), an HIV/AIDS-associated malignancy. Effective treatments against KS remain to be developed. The sugar analog 2-deoxy- d-glucose (2-DG) is an anticancer agent that is well-tolerated and safe in patients and was recently demonstrated to be a potent antiviral, including KSHV and severe acute respiratory syndrome coronavirus 2.Because 2-DG inhibits glycolysis and N-glycosylation, identifying its molecular targets is challenging. Here we compare the antiviral effect of 2-DG with2-fluoro-deoxy- d-glucose, a glycolysis inhibitor, and 2-deoxy-fluoro- d-mannose (2-DFM), a specific N-glycosylation inhibitor. At doses similar to those clinically achievable with 2-DG, the three drugs impair KSHV replication and virion production in iSLK.219 cells via downregulation of viral structural glycoprotein expression (K8.1 and gB), being 2-DFM the most potent KSHV inhibitor. Consistently with the higher potency of 2-DFM, we found that d-mannose rescues KSHV glycoprotein synthesis and virus production, indicating that inhibition of N-glycosylation is the main antiviral target using d-mannose competition experiments. Suppression of N-glycosylation by the sugar drugs triggers ER stress. It activates the host unfolded protein response (UPR), counteracting KSHV-induced inhibition of the protein kinase R-like endoplasmic reticulum kinasebranch, particularly activatingtranscription factor 4and C/EBP homologous protein expression. Finally, we demonstrate that sugar analogs induce autophagy (a prosurvival mechanism) and, thus, inhibit viral replication playing a protective role against KSHV-induced cell death, further supporting their direct antiviral effect and potential therapeutic use. Our work identifies inhibition of N-glycosylation leading to ER stress and UPR as an antienveloped virus target and sugar analogs such as 2-DG and the newly identified 2-DFM as antiviral drugs.

Mitochondrial protein, TBRG4, modulates KSHV and EBV reactivation from latency.

Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr (EBV) are gammaherpesviruses associated with multiple human malignancies. KSHV is the etiological agent of Kaposi's Sarcoma, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). EBV is associated with Burkitt's lymphoma (BL), Hodgkin's lymphoma (HL), nasopharyngeal carcinoma (NPC) and gastric carcinoma (GC). KSHV and EBV establish life-long latency in the human host with intermittent periods of lytic reactivation. Here, we identified a cellular factor named transforming growth factor-beta regulator 4 (TBRG4) that plays a role in the gammaherpesvirus lifecycle. We find that TBRG4, a protein that is localized to the mitochondria, can regulate lytic reactivation from latency of both KSHV and EBV. Knockdown of TBRG4 in cells latently infected with KSHV or EBV induced viral lytic gene transcription and replication. TBRG4 deficiency causes mitochondrial stress and increases reactive oxygen species (ROS) production. Treatment with a ROS scavenger decreased viral reactivation from latency in TBRG4-depleted cells. These data suggest that TBRG4 serves as a cellular repressor of KSHV and EBV reactivation through the regulation of ROS production.

Expression Ratios of the Antiapoptotic BCL2 Family Members Dictate the Selective Addiction of Kaposi's Sarcoma-Associated Herpesvirus-Transformed Primary Effusion Lymphoma Cell Lines to MCL1.

Kaposi's sarcoma-associated herpesvirus (KSHV) causes several malignancies in people living with HIV, including primary effusion lymphoma (PEL). PEL cell lines exhibit oncogene addictions to both viral and cellular genes. Using CRISPR screens, we previously identified cellular oncogene addictions in PEL cell lines, including MCL1. MCL1 is a member of the BCL2 family, which functions to prevent intrinsic apoptosis and has been implicated in several cancers. Despite the overlapping functions of the BCL2 family members, PEL cells are dependent only on MCL1, suggesting that MCL1 may have nonredundant functions. To investigate why PEL cells exhibit selective addiction to MCL1, we inactivated the intrinsic apoptosis pathway by engineering BAX/BAK1 double knockout cells. In this context, PEL cells become resistant to MCL1 knockdown or MCL1 inactivation by the MCL1 inhibitor S63845, indicating that the main function of MCL1 in PEL cells is to prevent BAX/BAK1-mediated apoptosis. The selective requirement to MCL1 is due to MCL1 being expressed in excess over the BCL2 family. Ectopic expression of several BCL2 family proteins, as well as the KSHV BCL2 homolog, significantly decreased basal caspase 3/7 activity and buffered against staurosporine-induced apoptosis. Finally, overexpressed BCL2 family members can functionally substitute for MCL1, when it is inhibited by S63845. Together, our data indicate that the expression levels of the BCL2 family likely explain why PEL tumor cells are highly addicted to MCL1. Importantly, our results suggest that caution should be taken when considering MCL1 inhibitors as a monotherapy regimen for PEL because resistance can develop easily. IMPORTANCE Primary effusion lymphoma (PEL) is caused by Kaposi's sarcoma-associated herpesvirus. We showed previously that PEL cell lines require the antiapoptotic protein MCL1 for survival but not the other BCL2 family proteins. This selective dependence on MCL1 is unexpected as the BCL2 family functions similarly in preventing intrinsic apoptosis. Recently, new roles for MCL1 not shared with the BCL2 family have emerged. Here, we show that noncanonical functions of MCL1 are unlikely essential. Instead, MCL1 functions mainly to prevent apoptosis. The specific requirement to MCL1 is due to MCL1 being expressed in excess over the BCL2 family. Consistent with this model, shifting these expression ratios changes the requirement away from MCL1 and toward the dominant BCL2 family gene. Together, our results indicate that although MCL1 is an attractive chemotherapeutic target to treat PEL, careful consideration must be taken, as resistance to MCL1-specific inhibitors easily develops through BCL2 family overexpression.

DNA virus oncoprotein HPV18 E7 selectively antagonizes cGAS-STING-triggered innate immune activation.

Cellular infections by DNA viruses trigger innate immune responses mediated by DNA sensors. The cyclic GMP-AMP synthase (cGAS)-stimulator of interferon gene (STING) signaling pathway has been identified as a DNA-sensing pathway that activates interferons in response to viral infection and, thus, mediates host defense against viruses. Previous studies have identified oncogenes E7 and E1A of the DNA tumor viruses, human papillomavirus 18 (HPV18) and adenovirus, respectively, as inhibitors of the cGAS-STING pathway. However, the function of STING in infected cells and the mechanism by which HPV18 E7 antagonizes STING-induced Interferon beta production remain unknown. We report that HPV18 E7 selectively antagonizes STING-triggered nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation but not IRF3 activation. HPV18 E7 binds to STING in a region critical for NF-κB activation and blocks the nuclear accumulation of p65. Moreover, E7 inhibition of STING-triggered NF-κB activation is related to HPV pathogenicity but not E7-Rb binding. HPV18 E7, severe acute respiratory syndrome coronavirus-2open reading frame 3a, human immunodeficiency virus-2 viral protein X, and Kaposi's sarcoma-associated herpesvirusKSHV viral interferon regulatory factor 1 selectively inhibited STING-triggered NF-κB or IRF3 activation, suggesting a convergent evolution among these viruses toward antagonizing host innate immunity. Collectively, selective suppression of the cGAS-STING pathway by viral proteins is likely to be a key pathogenic determinant, making it a promising target for treating oncogenic virus-induced tumor diseases.

Upregulation of ATF4-LAMP3 Axis by ORF45 Facilitates Lytic Replication of Kaposi's Sarcoma-Associated Herpesvirus.

Kaposi's sarcoma-associated herpesvirus (KSHV) is a γ-oncogenic herpesvirus, and both lytic and latent infections play important roles in its pathogenesis and tumorigenic properties. Multiple cellular pathways and diverse mediators are hijacked by viral proteins and are used to support KSHV lytic replication. In previous studies, we revealed that KSHV ORF45 promoted KSHV transcription and translation by inducing sustained p90 ribosomal S6 kinase (RSK) activation and the phosphorylation of its substrates c-Fos and eIF4B. However, the cellular mediators required for lytic replication remain largely unknown. Here, we reveal that ORF45 activates eIF2α phosphorylation and ATF4 translation and then upregulates the expression of lysosome-associated membrane protein 3 (LAMP3) in an ATF4-dependent manner during KSHV lytic replication. Consequently, LAMP3 promotes Akt and ERK activation and then facilitates lytic gene expression and virion production. Furthermore, ATF4 enhances lytic replication through LAMP3, and LAMP3 acts in an ATF4-independent manner. Our findings suggest that the ATF4-LAMP3 axis is upregulated by ORF45 through ER stress activation during the KSHV lytic life cycle and, in turn, facilitates optimal lytic replication. IMPORTANCE The lytic replication of Kaposi's sarcoma-associated herpesvirus (KSHV) reprograms cellular transcription and translation to generate viral proteins and virion particles. Here, we show that the mediator of ER stress ATF4 and the expression of the downstream gene LAMP3 are upregulated by ORF45 during lytic replication. Consequently, increased LAMP3 expression activates Akt and ERK and promotes lytic replication. Although several UPR transcription factors are able to promote KSHV lytic replication, the proviral effect of ATF4 on lytic replication is attenuated by LAMP3 silencing, whereas the effect of LAMP3 does not directly require ATF4 expression, indicating that LAMP3 primarily exerts effects on KSHV lytic replication downstream of ATF4 and ER stress. Taken together, our findings suggest that the ORF45-upregulated ATF4-LAMP3 axis plays an essential role in KSHV lytic replication.

Insights into Antiviral Properties and Molecular Mechanisms of Non-Flavonoid Polyphenols against Human Herpesviruses.

Herpesviruses are one of the most contagious DNA viruses that threaten human health, causing severe diseases, including, but not limited to, certain types of cancer and neurological complications. The overuse and misuse of anti-herpesvirus drugs are key factors leading to drug resistance. Therefore, targeting human herpesviruses with natural products is an attractive form of therapy, as it might improve treatment efficacy in therapy-resistant herpesviruses. Plant polyphenols are major players in the health arena as they possess diverse bioactivities. Hence, in this article, we comprehensively summarize the recent advances that have been attained in employing plant non-flavonoid polyphenols, such as phenolic acids, tannins and their derivatives, stilbenes and their derivatives, lignans, neolignans, xanthones, anthraquinones and their derivatives, curcuminoids, coumarins, furanocoumarins, and other polyphenols (phloroglucinol) as promising anti-herpesvirus drugs against various types of herpesvirus such as alpha-herpesviruses (herpes simplex virus type 1 and 2 and varicella-zoster virus), beta-herpesviruses (human cytomegalovirus), and gamma-herpesviruses (Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus). The molecular mechanisms of non-flavonoid polyphenols against the reviewed herpesviruses are also documented.

Epigenetic Reprogramming of Kaposi's Sarcoma-Associated Herpesvirus during Hypoxic Reactivation.

The biphasic life cycle (latent and lytic) of Kaposi's sarcoma-associated Herpesvirus (KSHV) is regulated by epigenetic modification of its genome and its associated histone proteins. The temporal events driving epigenetic reprogramming of the KSHV genome on initial infection to establish latency has been well studied, but the reversal of these epigenetic changes during lytic replication, especially under physiological conditions such as hypoxia, has not been explored. In this study, we investigated epigenetic reprogramming of the KSHV genome during hypoxic reactivation. Hypoxia induced extensive enrichment of both transcriptional activators and repressors on the KSHV genome through H3K4Me3, H3K9Me3, and H3K27Me3, as well as histone acetylation (H3Ac) modifications. In contrast to uniform quantitative enrichment with modified histones, a distinct pattern of RTA and LANA enrichment was observed on the KSHV genome. The enrichment of modified histone proteins was due to their overall higher expression levels, which was exclusively seen in KSHV-positive cells. Multiple KSHV-encoded factors such as LANA, RTA, and vGPCR are involved in the upregulation of these modified histones. Analysis of ChIP-sequencing for the initiator DNA polymerase (DNAPol1α) combined with single molecule analysis of replicated DNA (SMARD) demonstrated the involvement of specific KSHV genomic regions that initiate replication in hypoxia.

Investigation of berberine and its derivatives in Sars Cov-2 main protease structure by molecular docking, PROTOX-II and ADMET methods: in machine learning and in silico study

Bioactive compounds found in plants also have pharmacological antiviral effects. Berberine (BBR), an alkaloid found naturally in plants, is one of the phytochemicals with a wide range of biological activities, including antiviral, anticancer, anti-inflammatory and anti-inflammatory. In this study, we firstly aimed to predict pIC50 values for selcted compounds and then extract the binding patterns of berberine and its derivatives in the Sars Cov-2 Master Protease structure via employing molecular docking approache. Our results showed that berberine and its derivatives have good binding affinities towared Sars Cov2 main protease protein. Based on docking results the pharamaccokinetic studies for berberine, berberrubine, demethylen-berberine, jatrorrhizin, and thalifendine, were conducted and showed a good pharamacokinetic properties as an oral drugs. For deep inspection, we utiilized molecular dynmaics simulation to examine the Sars Cov2 main protease-ligand stabilities. The molecular dynamics simulation and PCA investigations revealed that thalifendine have a strong willing to act as good bindinder to SARS-CoV-2 protease. Further, the network based pharamacology showed that these drugs mediate different pathways such as human T-cell leukemia virus 1 infection, viral carcinogenesis, human immunodeficiency virus 1 infection, kaposi sarcoma-associated herpesvirus infection and epstein-Barr virus infection.The findings of this study have an important recomendation for thalifendine for more in vivo and in vitro studies to work. Communicated by Ramaswamy H. Sarma