Kaposi's Sarcoma-associated Herpesvirus Research Articles

IKKα-Mediated Noncanonical NF-κB Signaling Is Required To Support Murine Gammaherpesvirus 68 Latency In Vivo.

Noncanonical NF-κB signaling is activated in B cells via the tumor necrosis factor (TNF) receptor superfamily members CD40, lymphotoxin β receptor (LTβR), and B-cell-activating factor receptor (BAFF-R). The noncanonical pathway is required at multiple stages of B cell maturation and differentiation, including the germinal center reaction. However, the role of this pathway in gammaherpesvirus latency is not well understood. Murine gammaherpesvirus 68 (MHV68) is a genetically tractable system used to define pathogenic determinants. Mice lacking the BAFF-R exhibit defects in splenic follicle formation and are greatly reduced for MHV68 latency. We report a novel approach to disrupt noncanonical NF-κB signaling exclusively in cells infected with MHV68. We engineered a recombinant virus that expresses a dominant negative form of IκB kinase α (IKKα), named IKKα-SA, with S176A and S180A mutations that prevent phosphorylation by NF-κB-inducing kinase (NIK). We controlled for the transgene insertion by introducing two all-frame stop codons into the IKKα-SA gene. The IKKα-SA mutant but not the IKKα-SA.STOP control virus impaired LTβR-mediated activation of NF-κB p52 upon fibroblast infection. IKKα-SA expression did not impact replication in primary fibroblasts or in the lungs of mice following intranasal inoculation. However, the IKKα-SA mutant was severely defective in the colonization of the spleen and in the establishment of latency compared to the IKKα-SA.STOP control and wild-type (WT) MHV68 at 16 days postinfection (dpi). Reactivation was undetectable in splenocytes infected with the IKKα-SA mutant, but reactivation in peritoneal cells was not impacted by IKKα-SA. Taken together, the noncanonical NF-κB signaling pathway is essential for the establishment of latency in the secondary lymphoid organs of mice infected with the murine gammaherpesvirus pathogen MHV68. IMPORTANCE The latency programs of the human gammaherpesviruses Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV) are associated with B cell lymphomas. It is critical to understand the signaling pathways that are used by gammaherpesviruses to establish and maintain latency in primary B cells. We used a novel approach to block noncanonical NF-κB signaling only in the infected cells of mice. We generated a recombinant virus that expresses a dominant negative mutant of IKKα that is nonresponsive to upstream activation. Latency was reduced in a route- and cell type-dependent manner in mice infected with this recombinant virus. These findings identify a significant role for the noncanonical NF-κB signaling pathway that might provide a novel target to prevent latent infection of B cells with oncogenic gammaherpesviruses.

Thymus capitatus flavonoids inhibit infection of Kaposi's sarcoma-associated herpesvirus.

Kaposi's sarcoma‐associated herpesvirus (KSHV), also known as human herpes virus 8 (HHV‐8), causes primary effusion lymphoma, multicentric Castleman's disease, and Kaposi's sarcoma. Few antiviral drugs are available to efficiently control KSHV infection, and therefore, the development of novel, effective anti‐KSHV treatments is needed. The aim of this study was to determine the antiviral activity of ethanolic and aqueous extracts, essential oils, and certain flavonoids (hesperidin, eupafolin, and vicenin) derived from Thymus capitatus (commonly known as thyme). We assessed the toxicity of these different extracts and components in RPE‐1 cell cultures using the MTS test and evaluated their antiviral effect using the TCID50 method. The mechanism of action was determined through time‐of‐addition tests as well as viral entry, attachment, and virucidal assays. Additionally, western blot analysis was also used to assess their modes of action. Total treatment assay showed that the aqueous extract of T. capitatus has the highest inhibitory effect against KSHVLYT with an EC50 value of 0.2388 µg·mL−1. Both hesperidin and eupafolin showed the ability to inactivate viral infection in a dose–response manner (EC50 values of 0.2399 and 1.396 µm, respectively). Moreover, they were able to inactivate KSHVLyt postinfection by reducing viral protein expression. In summary, the effective antiviral property of the aqueous extract is likely a result of the inhibition of viral growth within the host cells by both hesperidin and eupafolin.

Oral Shedding of an Oncogenic Virus Alters the Oral Microbiome in HIV+ Patients.

Kaposi’s Sarcoma (KS) caused by Kaposi’s sarcoma-associated herpesvirus (KSHV) continues to be the most common AIDS-associated tumor. Involvement of the oral cavity represents one of the most common clinical manifestations of this tumor. Numerous types of cancer are associated with the alterations of in components of the microbiome. However, little is known about how KSHV coinfection affects the oral microbiome in HIV+ patients, especially in a “pre-cancer” niche. Using 16S rRNA pyrosequencing, we found that oral shedding of KSHV correlated with altered oral microbiome signatures in HIV+ patients, including a reduction in the microbiota diversity, changing the relative composition of specific phyla and species, and regulating microbial functions. Furthermore, we found that Streptococcus sp., one of the most increased species in the oral cavity of HIV+/KSHV+ patients, induced KSHV lytic reactivation in primary oral cells. Together, these data indicate that oral shedding of KSHV may manipulate the oral microbiome to promote viral pathogenesis and tumorigenesis especially in immunocompromised patients.

MiR-34a-5p inhibits the malignant progression of KSHV-infected SH-SY5Y cells by targeting c-fos.

BackgroundWe aimed to investigate the effects of miR-34a-5p on c-fos regulation mediating the malignant behaviors of SH-SY5Y cells infected with Kaposi’s sarcoma-associated herpesvirus (KSHV).MethodsThe KSHV-infected (SK-RG) and uninfected SH-SY5Y parent cells were compared for differentially expressed miRNAs using transcriptome sequencing. Then miR-34a-5p was upregulated in SK-RG cells by the miRNA mimics transfection. Cell proliferation ability was determined by MTT and plate clone assays. The cell cycle was assessed by flow cytometry analysis, and CDK4, CDK6, cyclin D1 levels were determined by Western blot analysis. The migration behavior was detected by wound healing and transwell assays. The protein levels of MMP2 and MMP9 were measured by Western blot analysis. The regulation of c-fos by miR-34a-5p was detected by the dual-luciferase reporter gene assay. Rescue assays were carried out by upregulating c-fos in miR-34a-5p-overexpressing SK-RG cells. KSHV DNA copy numbers and relative virus gene expressions were detected. Xenograft tumor experiments and immunohistochemistry assays were further used to detect the effects of miR-34a-5p.ResultsmiR-34a-5p was lower in SK-RG cells. Restoration of miR-34a-5p decreased cell proliferation and migration, leading to a G1 cell cycle arrest and down-regulation of CDK4/6, cyclin D1, MMP2, MMP9. KSHV copy number and expression of virus gene including latency-associated nuclear antigen (LANA), replication and transcription activator (RTA), open reading frame (K8.1), and KSHV G protein-coupled receptor (v-GPCR) were also reduced. Furthermore, c-fos is the target of miR-34a-5p, while enhanced c-fos weakened cellular behaviors of miR-34a-5p-overexpressing cells. Xenograft experiments and immunohistochemistry assays showed that miR-34a-5p inhibited tumor growth and virus gene expression.ConclusionUpregulated miR-34a-5p in KSHV-infected SH-SY5Y cells suppressed cell proliferation and migration through down-regulating c-fos. miR-34a-5p was a candidate molecular drug for KSHV-infected neuronal cells.

Epstein-Barr Virus, But Not Human Papillomavirus, Is Associated With Preinvasive and Invasive Ocular Surface Squamous Neoplasias in Zambian Patients.

BackgroundThe etiopathogenesis of ocular surface squamous neoplasia (OSSN) is not fully understood. We assessed the frequency of oncogenic viruses in OSSN by immunohistochemistry (IHC) and polymerase chain reaction (PCR) for human papillomavirus (HPV), Epstein–Barr virus (EBV), Merkel cell polyomavirus (MCPyV), Kaposi sarcoma virus, and adenovirus. Cases from Zambia were prospectively enrolled using a cross-sectional study design between November 2017 and March 2020.MethodsDemographic and clinical data [age, sex, HIV status, antiretroviral therapy (ART) history, CD4 count, plasma viral load] and tumor biopsies were collected from 243 consenting patients. Tumor samples were bisected, and half was used for DNA isolation, while the other half was formalin fixed and paraffin embedded (FFPE) for histopathology analysis. The expressions of latent EBV nuclear antigen 1 (EBNA1), CDKN2A/p16INK4A (p16), and MCPyV large T-antigen (LT) were tested by IHC. Multiplex PCR was used to detect 16 HPV genotypes and four other DNA tumor viruses [Kaposi’s sarcoma-associated herpesvirus (KSHV), EBV, MCPyV, and adenovirus]. Relationships between HIV status, viral DNA and protein expression, and tumor grades were determined by statistical analysis.ResultsOSSN tumors from patients were 29.6% preinvasive and 70.4% invasive. Patients presented with unilateral tumors that were 70.4% late stage (T3/T4). OSSN patients were HIV positive (72.8%). IHC on 243 FFPE biopsies resulted in the detection of EBNA1 (EBV), p16 high-risk HPV (HR-HPV), and MCPyV LT expression in 89.0%, 4.9%, and 0.0%, respectively. EBNA1 was expressed in all grades of preinvasive [cornea–conjunctiva intraepithelial neoplasia (CIN)1, 100%; CIN2, 85.7%; CIN3, 95.8%; and carcinoma in situ (CIS), 83.8%] and in invasive (89.2%) OSSN. PCR on 178 samples detected EBV, HR-HPV, and MCPyV in 80.3%, 9.0%, and 13.5% of tumors, respectively. EBV was detected in all grades of preinvasive and invasive OSSN. EBV detection was associated with high HIV viral loads (p = 0.022). HR-HPV was detected in 0.0% CIN1, 0.0% CIN2, 5.6% CIN3, 13.0% CIS, and 7.0% invasive OSSN.ConclusionsOur findings of EBV DNA and EBNA1 protein in all the grades of preinvasive and especially invasive OSSN are consistent with a potential causal role for EBV in OSSN. A role of HPV in OSSN was not clearly established in this study.

Molecular Mechanisms of Kaposi Sarcoma Development.

Simple SummaryThere are at least four forms of Kaposi’s sarcoma (KS) with the ‘HIV’-related form being the most aggressive and can involve mucosae or visceral organs. Kaposi’s sarcoma-associated herpes virus (KSHV) is the underlying cause of this disease. It can infect endothelial and/or mesenchymal cells and establish a latent phase in host cells in which latency proteins and various non-coding RNAs (ncRNAs) play a complex role in proliferation and angiogenesis. It also undergoes periods of sporadic lytic reactivation that are key for KS progression. Complex interactions with the microenvironment with production of inflammatory cytokines and paracrine signaling is a standout feature of KS development and maintenance. KSHV impairs the immune response by various mechanisms such as the degradation of a variety of proteins involved in immune response or binding to cellular chemokines. Treatment options include classical chemotherapy, but other novel therapies are being investigated.Kaposi’s sarcoma (KS) is a heterogeneous angioproliferative tumor that generally arises in the skin. At least four forms of this disease have been described, with the ‘HIV’-related form being the most aggressive and can involve mucosae or visceral organs. Three quarters of KS cases occur in sub-Saharan Africa (SSA) as geographic variation is explained by the disparate prevalence of KS-associated herpes virus (KSHV), which is the underlying cause of this disease. It can infect endothelial and/or mesenchymal cells that consequently transdifferentiate to an intermediate state. KSHV establishes a latent phase in host cells in which latency proteins and various non-coding RNAs (ncRNAs) play a complex role in proliferation and angiogenesis. It also undergoes periods of sporadic lytic reactivation triggered by various biological signals in which lytic stage proteins modulate host cell signaling pathways and are key in KS progression. Complex interactions with the microenvironment with production of inflammatory cytokines with paracrine signaling is a standout feature of KS development and maintenance. KSHV impairs the immune response by various mechanisms such as the degradation of a variety of proteins involved in immune response or binding to cellular chemokines. Treatment options include classical chemotherapy, but other novel therapies are being investigated.

Environmental determinants of Kaposi’s sarcoma-associated herpesvirus (KSHV) transmission in rural Uganda (ENDKU study): Contributions to research on KSHV infection and reactivation in African children; A longitudinal cohort study

BackgroundThe Environmental Determinants of KSHV transmission in rural Uganda (ENDKU) study began enrollment in February 2020 with the purpose of defining the relationship between malaria, primarily caused by Plasmodium falciparum in sub-Saharan Africa, and KSHV susceptibility and reactivation. Uganda is an ideal study site, because both malaria and KSHV are endemic and widespread, even among young children. MethodsENDKU is a longitudinal cohort study of infants enrolled at six months of age and followed until three years of age. The main study, and one smaller sub-study, is nested within the General Population Cohort (GPC), a long-standing population cohort in rural Uganda. The ENDKU study was created to test the hypothesis that P. falciparum malaria increases an infant’s susceptibility to KSHV infection. A sub-study to evaluate the effects of P. falciparum on KSHV reactivation involves an additional cohort of 5–10-year-old children with and without acute malaria who presented to the GPC study clinic. For each study, participants provided demographic and behavioral data through administered questionnaires and blood and saliva samples. ResultsDespite barriers presented by the COVID-19 pandemic, the study team was able to leverage the long-standing relationship of the UK Medical Research Council and the Uganda Virus Research Institute (MRC/UVRI) with the community, a strong commitment to research, and a multi-disciplinary team of experts to successfully implement the ENDKU study. ConclusionThe results of this multi-pronged approach will answer important questions about the etiology and transmission of KSHV in sub-Saharan Africa and the data and samples collected will be an important future resource for scientific research in the region.

Structural Insight into KsBcl-2 Mediated Apoptosis Inhibition by Kaposi Sarcoma Associated Herpes Virus.

Numerous large DNA viruses have evolved sophisticated countermeasures to hijack the premature programmed cell death of host cells post-infection, including the expression of proteins homologous in sequence, structure, or function to cellular Bcl-2 proteins. Kaposi sarcoma herpes virus (KSHV), a member of the gammaherpesvirinae, has been shown to encode for KsBcl-2, a potent inhibitor of Bcl-2 mediated apoptosis. KsBcl-2 acts by directly engaging host pro-apoptotic Bcl-2 proteins including Bak, Bax and Bok, the BH3-only proteins; Bim, Bid, Bik, Hrk, Noxa and Puma. Here we determined the crystal structures of KsBcl-2 bound to the BH3 motif of pro-apoptotic proteins Bid and Puma. The structures reveal that KsBcl-2 engages pro-apoptotic BH3 motif peptides using the canonical ligand binding groove. Thus, the presence of the readily identifiable conserved BH1 motif sequence “NWGR” of KsBcl-2, as well as highly conserved Arg residue (R86) forms an ionic interaction with the conserved Asp in the BH3 motif in a manner that mimics the canonical ionic interaction seen in host Bcl-2:BH3 motif complexes. These findings provide a structural basis for KSHV mediated inhibition of host cell apoptosis and reveal the flexibility of virus encoded Bcl-2 proteins to mimic key interactions from endogenous host signalling pathways.

A Case of Neglected Classıc Kaposı’s Sarcoma

Kaposi's sarcoma (KS) is a rare disease in the community. It was first described in 1872 as an idiopathic, multipigmented sarcoma of the skin [1]. It is a vascular or lymphatic-focused tumor type originating from the endothelium, caused by Human Herpes Virus 8 (HHV8), called KS-associated herpes virus (KSHV) [2]. There are 4 clinical subtypes of the disease. These are: Classical KS, African endemic KS, iatrogenic KS, and AIDS-related (epidemic) KS. It usually occurs with pink-red patch and blue-purple-black nodule, polyp or plaques. Most of the cases in classical KS are over 50 years old. Although the female/male ratio varies between studies, it is more common in males [3]. Here, a neglected case of Classic KS is presented.

Flavonoids Target Human Herpesviruses That Infect the Nervous System: Mechanisms of Action and Therapeutic Insights.

Human herpesviruses (HHVs) are large DNA viruses with highly infectious characteristics. HHVs can induce lytic and latent infections in their host, and most of these viruses are neurotropic, with the capacity to generate severe and chronic neurological diseases of the peripheral nervous system (PNS) and central nervous system (CNS). Treatment of HHV infections based on strategies that include natural products-derived drugs is one of the most rapidly developing fields of modern medicine. Therefore, in this paper, we lend insights into the recent advances that have been achieved during the past five years in utilizing flavonoids as promising natural drugs for the treatment of HHVs infections of the nervous system such as alpha-herpesviruses (herpes simplex virus type 1, type 2, and varicella-zoster virus), beta-herpesviruses (human cytomegalovirus), and gamma-herpesviruses (Epstein–Barr virus and Kaposi sarcoma-associated herpesvirus). The neurological complications associated with infections induced by the reviewed herpesviruses are emphasized. Additionally, this work covers all possible mechanisms and pathways by which flavonoids induce promising therapeutic actions against the above-mentioned herpesviruses.

Synthesis, anti‐proliferative activities, docking studies, and computational calculations of novel isonicotinic mixed complexes

AbstractIn this investigation, we studied the mixing of two ligands, isonicotinohydrazide (L1) and 3‐hydroxyisonicotinic acid (L2), with different metal ions to afford the corresponding stable metal complexes. Consequently, intensive physico‐chemical analysis including elemental analysis, UV–visible, Fourier transform infrared (FT‐IR), thermogravimetric analysis (TGA), mass, 1H nuclear magnetic resonance (NMR), X‐ray diffraction (XRD), magnetic, and molar conductance measurements has been performed. The thermal stability of all complexes was determined using TGA, and the kinetic parameters were obtained using the Coats–Redfern method. Both the degree of crystallinity and the unit cell of all complexes were determined utilizing XRD studies. Furthermore, these metal complexes exhibited excellent anti‐proliferative activity against human breast cancer (MCF‐7) and human liver cancer (HepG2) cell lines against the doxorubicin drug. The Co(II) complex outperformed all other metal complexes in terms of activity, which was confirmed by molecular docking stimulation via the binding energy with amino acids in a structural complex of Kaposi's sarcoma‐associated herpesvirus (KSHV) thymidylate synthase (PDBID:5H38) and the ternary complex of KRIT1 bound to both the Rap1 GTPase and the Heart of Glass (HEG1) cytoplasmic tail (PDBID:4hdq) and shortage. Moreover, these metal complexes were optimized via theoretical investigation through a density functional theory (DFT)/B3LYP/LANL2DZ basis set to confirm the stability of these metals theoretically and detect frontier molecular orbitals (FMO), electrostatic potential (ESP), energy gap, and physical computational calculations. Eventually, the electrochemical features were explored using cyclic voltammetry (CV) and electrochemical impedance spectra (EIS).

Classic KSHV/HHV-8-positive Primary Effusion Lymphoma (PEL): A Systematic Review and Meta-Analysis of Case Reports.

Primary effusion lymphoma (PEL) is a large B-cell lymphoma growing within body-cavities caused by the Kaposi sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8 (KSHV/HHV-8). It is mainly reported in HIV-infected patients. The uncommon occurrence in the elderly supports a form paralleling classic Kaposi sarcoma (KS), i.e. classic PEL, whose characteristics are relatively underexplored. To better understand the diagnostic modalities and clinical-epidemiological features of classic PEL, articles reporting cases of PEL were identified through MEDLINE/EMBASE databases (January 1998–July 2020) and screened according to PRISMA guidelines to extract individual-level data. A comparison was also performed between classic PEL and classic KS to evaluate similarities and differences. We identified 105 subjects (median age 77 years; 86% males), mainly from Mediterranean countries (52%, first Italy) and Eastern Europe (7%). Common comorbidities were heart failure (32%), cirrhosis (16%), and malignancy (20%) including lymphoid neoplasms. Pleural cavity was the commonest site (67%). PEL diagnosis was based on cytomorphology (89%), evidence of KSHV/HHV-8 infection (94%), EBV co-infection (28%) and clonality of IGH (59%), IGK (14%), TRG (9%) alone or in multiple combinations. Compared to KS, age (P<.001), gender-ratio (P=.08) and mortality (P<.001) were significantly higher in PEL, whereas the frequency of PEL as a second primary was similar (P=.44). This is the first systematic review of classic PEL case reports highlighting heterogeneity and lack of a uniform multidisciplinary approach at diagnosis, in the absence of specific guidelines as it happens for rare cancers. It is conceivable that classic PEL is still underdiagnosed in Mediterranean countries wherein KSHV/HHV-8 is endemic.

VFLIP-regulated competing endogenous RNA (ceRNA) networks targeting lytic induction for KSHV-associated malignancies.

Kaposi's sarcoma-associated herpesvirus (KSHV) causes life-long latent infection and malignancies, including KScommonly found in AIDS patients. Lytic replication can be induced to kill tumor cells harboring latent KSHV, through viral cytopathic effects and the subsequent antiviral immune responses. Viral FLICE-inhibitory protein (vFLIP), encoded by KSHV ORF K13, inhibits KSHV lytic reactivation, implying that the competing endogenous RNA (ceRNA) networks regulated by vFLIP can be modulated to induce the lytic reactivation of latent KSHV, a promising strategy for KSHV-associated malignancies. Here, we performed whole-transcriptome sequencing to reveal the global landscape of noncoding RNAs and messenger RNAs (mRNAs) in iSLK-RGB-BAC16 cells and iSLK-RGB-K13 mutant cells. It showed that vFLIP regulated 227 differentially expressed (DE) long non-coding RNAs (lncRNAs), 57 DEcircular RNAs(circRNAs), 20 DE microRNAs (miRNAs), and 1371 DE mRNAs. Enrichment analysis verified that riboflavin metabolism was simultaneously enriched in DE genes related to miRNAs, lncRNAs, and circRNAs. The upregulated hsa-miR-378i and hsa-miR-3654, and downregulated miR-4467, miR-3163, miR-4451, and miR-4257 were significantly enriched in the ceRNA complex network, which contained 9 upregulated and 7 downregulated circRNAs, 5 upregulated and 85 downregulated lncRNAs, 5 upregulated and 35 downregulated mRNAs. Finally, we constructed and validated two vFLIP-regulated ceRNA networks: circRNA hsa_circ_0070049/hsa-miR-378i/SPEG/FOXQ1 and lncRNA AL031123.1/hsa-miR-378i/SPEG/FOXQ1. Taken together, the two ceRNA networks may mediate KSHV reactivation. These novel findings refreshed the present understanding of ceRNA network in KSHV lytic induction and provided potential therapeutic targets for KSHV-associated malignancies.

The m6A reader YTHDC2 is essential for escape from KSHV SOX-induced RNA decay

The role of N6-methyladenosine (m6A) modifications has increasingly been associated with a diverse set of roles in modulating viruses and influencing the outcomes of viral infection. Here, we report that the landscape of m6A deposition is drastically shifted during Kaposi's sarcoma-associated herpesvirus (KSHV) lytic infection for both viral and host transcripts. In line with previous reports, we also saw an overall decrease in host methylation in favor of viral messenger RNA (mRNA), along with 5' hypomethylation and 3' hypermethylation. During KSHV lytic infection, a major shift in overall mRNA abundance is driven by the viral endoribonuclease SOX, which induces the decay of greater than 70% of transcripts. Here, we reveal that interlukin-6 (IL-6) mRNA, a well-characterized, SOX-resistant transcript, is m6A modified during lytic infection. Furthermore, we show that this modification falls within the IL-6 SOX resistance element, an RNA element in the IL-6 3' untranslated region (UTR) that was previously shown to be sufficient for protection from SOX cleavage. We show that the presence of this m6A modification is essential to confer SOX resistance to the IL-6 mRNA. We next show that this modification recruits the m6A reader YTHDC2 and found that YTHDC2 is necessary for the escape of the IL-6 transcript. These results shed light on how the host cell has evolved to use RNA modifications to circumvent viral manipulation of RNA fate during KSHV infection.

The effect of dimerization and ligand binding on the dynamics of Kaposi's sarcoma-associated herpesvirus protease.

The Kaposi's sarcoma‐associated herpesvirus protease is essential for virus maturation. This protease functions under allosteric regulation that establishes its enzymatic activity upon dimerization. It exists in equilibrium between an inactive monomeric state and an active, weakly associating, dimeric state that is stabilized upon ligand binding. The dynamics of the protease dimer and its monomer were studied using the Gaussian network model and the anisotropic network model , and its role in mediating the allosteric regulation is demonstrated. We show that the dimer is composed of five dynamical domains. The central domain is formed upon dimerization and composed of helix five of each monomer, in addition to proximal and distal domains of each monomer. Dimerization reduces the mobility of the central domains and increases the mobility of the distal domains, in particular the binding site within them. The three slowest ANM modes of the dimer assist the protease in ligand binding, motion of the conserved Arg142 and Arg143 toward the oxyanion, and reducing the activation barrier for the tetrahedral transition state by stretching the bond that is cleaved by the protease. In addition, we show that ligand binding reduces the motion of helices α1 and α5 at the interface and explain how ligand binding can stabilize the dimer.

Whole-genome sequencing of Kaposi sarcoma-associated herpesvirus (KSHV/HHV8) reveals evidence for two African lineages

Kaposi sarcoma (KS)-associated herpesvirus (KSHV/HHV-8) was first sequenced from the body cavity (BC) lymphoma cell line, BC-1, in 1996. Few other KSHV genomes have been reported. Our knowledge of sequence variation for this virus remains spotty. This study reports additional genomes from historical US patient samples and from African KS biopsies. It describes an assay that spans regions of the virus that cannot be covered by short read sequencing. These include the terminal repeats, the LANA repeats, and the origins of replication. A phylogenetic analysis, based on 107 genomes, identified three distinct clades; one containing isolates from USA/Europe/Japan collected in the 1990s and two of Sub-Saharan Africa isolates collected since 2010. This analysis indicates that the KSHV strains circulating today differ from the isolates collected at the height of the AIDS epidemic. This analysis helps experimental designs and potential vaccine studies.

Primary Effusion Lymphoma: A Clinicopathologic Perspective.

Simple SummaryPrimary effusion lymphoma (PEL) is a rare B-cell lymphoma with a particularly aggressive course. This disease usually affects the variably immunocompromised and maintains a predilection for body cavities, leading to the development of malignant effusions. Pathogenesis suggests an association with HHV8 and EBV, although this is unclear. There are no definitive guidelines for the treatment of PEL, but commonly used initial regimens include those similar to DA-EPOCH and CHOP. The prognosis remains poor, even with advanced treatment. Newer therapies incorporate the use of axicabtagene ciloleucel, CAR-T cell therapies, and augmented EPOCH regimens. Further investigation into oncogenesis and targeted molecular pathways could provide insights into treatment targets. In this review, the authors would like to compare this disease with other similarly aggressive B-cell lymphomas, as well as highlight the unique epidemiology, pathogenesis, and current treatment options for patients diagnosed with PEL.Primary effusion lymphoma (PEL) is a rare, aggressive B-cell lymphoma that usually localizes to serous body cavities to subsequently form effusions in the absence of a discrete mass. Although some tumors can develop in extracavitary locations, the areas most often affected include the peritoneum, pleural space, and the pericardium. PEL is associated with the presence of human herpesvirus 8 (HHV8), also called the Kaposi sarcoma-associated herpesvirus (KSHV), with some variability in transformation potential suggested by frequent coinfection with the Epstein-Barr virus (EBV) (~80%), although the nature of the oncogenesis is unclear. Most patients suffering with this disease are to some degree immunocompromised (e.g., Human immunodeficiency virus (HIV) infection or post-solid organ transplantation) and, even with aggressive treatment, prognosis remains poor. There is no definitive guideline for the treatment of PEL, although CHOP-like regimens (cyclophosphamide, doxorubicin, vincristine, and prednisone) are frequently prescribed and, given the rarity of this disease, therapeutic focus is being redirected to personalized and targeted approaches in the experimental realm. Current clinical trials include the combination of lenalidomide and rituximab into the EPOCH regimen and the treatment of individuals with relapsed/refractory EBV-associated disease with tabelecleucel.

A case of convergent evolution: Several viral and bacterial pathogens hijack RSK kinases through a common linear motif

Microbes have been coevolving with their host for millions of years, exploiting host resources to their own benefit. We show that viral and bacterial pathogens convergently evolved to hijack cellular mitogen-activated protein kinase (MAPK) p90-ribosomal S6-kinases (RSKs). Theiler's virus leader (L) protein binds RSKs and prevents their dephosphorylation, thus maintaining the kinases active. Recruitment of RSKs enables L-protein-mediated inhibition of eukaryotic translation initiation factor 2 alpha kinase 2 (EIF2AK2 or PKR) and stress granule formation. Strikingly, ORF45 protein of Kaposi's sarcoma-associated herpesvirus (KSHV) and YopM protein of Yersinia use the same peptide motif as L to recruit and activate RSKs. All three proteins interact with a conserved surface-located loop of RSKs, likely acting as an allosteric regulation site. Some unrelated viruses and bacteria thus evolved to harness RSKs in a common fashion, yet to target distinct aspects of innate immunity. As documented for Varicella zoster virus ORF11, additional pathogens likely evolved to hijack RSKs, using a similar short linear motif.

Environmental risk factors and genetic markers of Kaposi's sarcoma-associated herpesvirus infection among Uygur population in Xinjiang, China.

Kaposi sarcoma-associated herpesvirus (KSHV) is endemic in Xinjiang, China. Determinants of KSHV seropositivity among high-risk groups are not well understood. We seek to identify genetic and environmental predisposing factors for KSHV infection among Uygurs in this endemic region. A cross-sectional study was performed among the Uygur population in Xinjiang, China. KSHV-antibodies were detected using immunofluorescence assay (IFA) and human leukocyte antigen (HLA) alleles were genotyped. Univariate and multivariate logistic regression analyses were applied to explore the environmental and genetic risk factors of KSHV seropositivity. Finally, a total of 721 participants were included. The seroprevalence of KSHV was 24.1% among this population. Sweet-food preference (odds ratio [OR] 1.85, 95% confidence interval [CI] 1.03-3.34), and coronary heart disease (OR 1.91, 95%CI 1.24-2.94) were statistically correlated with KSHV infection. HLA-DQB1*06:09 were found to significantly increase the risk of KSHV infection under all 3 models (ORAllelic = 4.06; ORDominant = 3.27; and ORRecessive = 8.06). Six SNPs (SNP0260, SNP0361, SNP0797, SNP0852, SNP1159, and SNP1375) in the DQB1 and DRB1 region and haploid type GTCTAACTAATC in block 17 were statistically associated with KSHV infection. We demonstrated that genetic variations in HLA-DQB1/DRB1 and environmental risk factors were strongly associated with KSHV infection among this population.

MiRNA Sequence Analysis in Patients With Kaposi's Sarcoma-Associated Herpesvirus.

MicroRNAs (miRNAs) are the non-coding RNAs that can both attach to the untranslated and coding sections of target mRNAs, triggering destruction or post-transcriptional alteration. miRNAs regulate various cellular processes such as immune function, apoptosis, and tumorigenesis. About 35,000 miRNAs have been discovered in the human genome. The increasing evidence suggests that the dysregulation of human miRNAs may have a role in the etiology of some disorders including cancer. Only a small sub-set of human miRNAs has functionally been validated in the pathogenesis of oncogenic viruses such as Kaposi’s sarcoma-associated herpesvirus (KSHV). KSHV is the cause of various human malignancies including primary effusion lymphoma (PEL) and Kaposi’s sarcoma (KS), which are mainly seen in AIDS patients or other immunocompromised people. We aimed to identify the miRNAs in Kaposi’s sarcoma cases, with the comparison of KSHV seropositive and seronegative tumors with the controls and in each other in Turkish Kaposi’s sarcoma patients. We performed the miRNA-sequencing at genome level in the peripheral blood mononuclear cells of 16 Kaposi’s sarcoma patients, and in 8 healthy controls matched for age, gender, and ethnicity. A total of 642 miRNA molecules with different expression profiles were identified between the patients and the healthy controls. Currently, out of 642 miRNAs, 7 miRNAs (miR-92b-3p, miR-490-3p, miR-615-3p, miR-629-5p, miR-1908, miR-3180, miR-4433b-3p) which have not been described in the literature in the context of Kaposi’s sarcoma were addressed in the study for the first time and 9 novel miRNAs, not found previously in the database, have been detected in Kaposi’s sarcoma using the miRNA-sequencing technique. This study demonstrates the identification of differently expressed miRNAs which might be the new therapeutic targets for Kaposi’s sarcoma, that has limited treatment options and can be used in the etiology, diagnosis, and prognosis of this cancer.