Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.

Regional prevalence and transmission route of Kaposi＇s sarcoma-associated herpes virus in Zhejiang, China

Background The infection of Kaposi＇s sarcoma-associated herpes virus （KSHV） is most likely the cause of clinical Kaposi＇s sarcoma,primary effusion lymphoma,and multi-center Castleman＇s disease.KSHV infection has very limited epidemiological survey data in China,and its definite mode of transmission remains controversial.This study aimed to determine the infection status and the main transmission route of KSHV in Chinese population.Methods An enzyme-linked immunosorbent assay （ELISA） utilizing KSHV ORF65 recombinant protein was employed to analyze the antibody response to KSHV ORF65 in sera from 122 healthy physical examination people,107intravenous drug users,135 non-intravenous drug users,211 hepatitis B （HBV） patients infected via blood transmission,107 kidney transplant recipients,and 72 female sex workers in Zhejiang Province in Southeast China.Results KSHV infection occurred relatively common （13.1%） in healthy population in Zhejiang,China.Infection rate was 16.7% in female sex workers,but significantly elevated in intravenous drug addicts （58.9%）,blood-transmitted HBV patients （28.0%） and kidney transplant patients （41.1%）.Conclusion Blood borne transmission of KSHV is probably the main route of infection in Zhejiang Province.

Regulation of Wnt/β-catenin signaling by herpesviruses

The Wnt/β-catenin signaling pathway is instrumental in successful differentiation and proliferation of mammalian cells. It is therefore not surprising that the herpesvirus family has developed mechanisms to interact with and manipulate this pathway. Successful coexistence with the host requires that herpesviruses establish a lifelong infection that includes periods of latency and reactivation or persistence. Many herpesviruses establish latency in progenitor cells and viral reactivation is linked to host-cell proliferation and differentiation status. Importantly, Wnt/β-catenin is tightly connected to stem/progenitor cell maintenance and differentiation. Numerous studies have linked Wnt/β-catenin signaling to a variety of cancers, emphasizing the importance of Wnt/β-catenin pathways in development, tissue homeostasis and disease. This review details how the alpha-, beta-, and gammaherpesviruses interact and manipulate the Wnt/β-catenin pathway to promote a virus-centric agenda.

Preparation and application of polyclonal antibodies against KSHV v-cyclin

We prepared rabbit polyclonal antibodies against Kaposi＇s sarcoma-associated herpesvirus （KSHV）-encoded v- cyclin （ORF 72） and detected the natural viral protein using these polyclonal antibodies. Three antigenic polypep- tides of v-cyclin were designed and synthesized. A fragment of the v-cyclin gene was cloned into a eukaryotic expression vector pEF-MCS-Flag-IRES/Puro to construct a recombinant vector, pEF v-cyclin. Then, pEF v-cyclin was transfected into 293T and EA.hy926 cells to obtain v-cyclin-Flag fusion proteins. Six New Zealand white rabbits were immunized with KLH-conjugated peptides to generate polyclonal antibodies against v-cyclin. The polyclonal antibodies were then characterized by ELISA and Western blotting assays. Finally, the polyclonal anti- bodies against v-cyclin were used to detect natural viral protein expressed in BCBL-1, BC-3, and JSC-1 cells. The results showed that using the Flag antibody, v-cyclin-Flag fusion protein was detected in 293T and EA.hy926 cells transfected with pEF-v-cyclin. Furthermore, ELISA showed that the titer of the induced polyclonal rabbit anti-v- cyclin antibodies was higher than 1：8,000. In Western blotting assays, the antibodies reacted specifically with the v-cyclin-Flag fusion protein as well as the natural viral protein. The recombinant expression vector pEF-v-cyclin was constructed successfully, and the polyclonal antibodies prepared can be used for various biological tests in- cluding ELISA and Western blotting assays.

Lipids, lipid metabolism and Kaposi's sarcoma-associated herpesvirus pathogenesis

Lipids are essential for mammalian cells to maintain many physiological functions. Emerging evidence has shown that cancer cells can develop specific alterations in lipid biosynthesis and metabolism to facilitate their survival and various malignant behaviors. To date, the precise role of cellular lipids and lipid metabolism in viral oncogenesis is still largely unclear with only a handful of literature covering this topic to implicate lipid metabolism in oncogenic virus associated pathogenesis. In this review, we focus on the role of lipid biosynthesis and metabolism in the pathogenesis of the Kaposi's sarcoma-associated herpesvirus, a common causative factor for cancers arising in the immunocompromised settings.

Prevalence of Kaposi's sarcoma-associated herpesvirus among intravenous drug users： a systematic review and meta-analysis

Intravenous drug users(IDUs) have been demonstrated to be highly vulnerable to HIV/AIDS.Nevertheless, the prevalence of Kaposi's sarcoma associated herpesvirus(KSHV), an important co-infected agent with HIV, among this population remained obscure. We conducted a systematic review on the epidemiological features of KSHV among IDUs worldwide. Eligible studies were retrieved from 6 electronic databases(Pub Med, EMBASE, Web of Science, CBM, CNKI and Wanfang).We calculated the pooled prevalence and 95% confidence interval(CI) overall and among subgroups using either random-effects model or fixed-effects model depending on between-study heterogeneity. The potential publication bias was assessed by the Egger's test. A meta-regression analysis was performed to explore the sources of heterogeneity. Finally, twenty-two studies with a total sample of 7881 IDUs were included in the analysis. The pooled prevalence of KSHV was14.71%(95% CI 11.12%–19.46%) among IDUs. Specifically, KSHV prevalence was 10.86%(95% CI6.95%–16.96%) in HIV-negative IDUs, and 13.56%(95% CI 10.57%–17.38%) in HIV-positive IDUs.Moreover, prevalence among IDUs from the three continents involved in the current study was similar:16.10%(95%CI 7.73%–33.54%) in Asia; 14.22%(95%CI 8.96%–22.57%) in Europe and 14.06%(95%CI11.38%–17.37%) in America. Globally, IDUs are at higher risk of the KSHV infection when compared with the general population, regardless of geographical region or HIV-infection status.

The replication and transcription activator (RTA) of Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8

Kaposi’s sarcoma-associated herpesvirus(KSHV)is γ-2 herpesvirus with latency and lytic replication stages in its life-cycle.The viral replication and transcription activator(RTA)is the key protein for triggering KSHV lytic gene expression and replication from latency.In this review,we will discuss the gene expression program in KSHV lytic replication and latency,the regulation of the RTA expression,the RTA protein and the mechanisms that RTA utilizes to transactivate its target genes.We will focus on the RTA-mediated transactivation mechanisms,including DNA-binding,interacting with cellular co-factors and promoting repressor degradation.

Amino acids essential for the interaction between cellular heat shock protein 90 and a Kaposi's sarcoma-associated herpesvirus-encoded protein kinase ORF36

Dear Editor,Protein-protein interactions(PPIs)often play important roles in biological processes(Zhang et al.,2016).The split Renilla luciferase complementation assay(SRLCA)is one of the methods in studying PPIs.SRLCA is based on the complementation of the N-terminal domains of Renilla luciferase(LN)and C-terminal domains

The Role of Human Herpesvirus 8 Molecular Characterization in the Management of HIV Infected Patients Diagnosed with Malignancies Associated with Its Infection

Despite the progress has been reached with Human herpesvirus 8 (HHV-8) research, there are gaps in the knowledge of viral induced oncogenesis. The aim of the present study was to identify possible associations between HHV-8 subtypes, HHV-8 loads and clinical manifestations of HIV infected patients diagnosed with different malignancies associated with HHV-8 infection. Forty six HIV-1 infected individuals diagnosed with different HHV-8 associated diseases were studied [37 epidemic Kaposi’s sarcoma (KS), 3 pleural effusion lymphoma (PEL);5 peripheral lymphadenopathies (PL);1 Hodgkin’s lymphoma (HL);1 non Hodgkin’s lymphoma (NHL)]. HHV-8 loads were determined by quantitative real time PCR (qRT-PCR) whilst HHV-8 subtypes were determined by open-reading frame (ORF)-K1 gen genotyping. HHV-8 subtypes B, A, C, A5 and E were exhibited by 31.8%, 23.4%, 19.1%, 17% and 8.5% of the studied patients, respectively. The median HHV-8 viral load did not differ between subtypes (p > 0.05) but HHV-8 viral loads were significantly higher in PEL than in epidemic KS lesion or lymph nodes (p = 0.04). Subtype B was detected in 60% of patients with B cell lymphoma (NHL, PEL and HL) whereas subtype E was only detected in patients with epidemic KS diagnosis. Our data suggest that HHV-8 DNA quantification instead of subtype identification could be used as a surrogate marker for monitoring its infection, not only in epidemic KS patients but also in HIV infected individuals with lymphoproliferative disorders.

卡波济肉瘤相关疱疹病毒潜伏相关核抗原编码基因的克隆及表达

目的:分离卡波济肉瘤相关疱疹病毒(KSHV)潜伏相关核心抗原(LANA)羧基端基因(ORF73C),并在大肠杆菌中克隆和表达。方法:设计一对PCR引物,在引物的5′端分别引入BamH I和EcoR I酶切位点,提取稳定状态的BCBL-1细胞的总DNA作模板,通过PCR扩增KSHV ORF73C,PCR产物经双酶切后按正确的读码框克隆进原核表达质粒pGEX-6p-1中,并转化大肠杆菌感受态细胞BL21,以异丙基硫代-β-D-半乳糖苷(IPTG)诱导表达融合蛋白。结果:经核酸序列测定及分析,分离、克隆的ORF73C基因与基因数据库中登记的ORF73基因的羧基端的621bp的序列有99％同源性。经IPTG诱导的重组质粒转化菌体SDS-聚丙烯酰胺凝胶(PAGE)电泳显示有大小约为46ku的融合蛋白表达。结论:初步表明ORF73C基因在大肠杆菌中获得正确表达。

Manipulation of the host cell membrane by humanγ-herpesviruses EBV and KSHV for pathogenesis

The cell membrane regulates many physiological processes including cellular communication,homing and metabolism. It is therefore not surprising that the composition of the host cell membrane is manipulated by intracellular pathogens. Among these, the human oncogenic herpesviruses Epstein–Barr virus(EBV) and Kaposi's sarcoma-associated herpesvirus(KSHV)exploit the host cell membrane to avoid immune surveillance and promote viral replication.Accumulating evidence has shown that both EBV and KSHV directly encode several similar membrane-associated proteins, including receptors and receptor-specific ligands(cytokines and chemokines), to increase virus fitness in spite of host antiviral immune responses. These proteins are expressed individually at different phases of the EBV/KSHV life cycle and employ various mechanisms to manipulate the host cell membrane. In recent decades, much effort has been made to address how these membrane-based signals contribute to viral tumorigenesis. In this review, we summarize and highlight the recent understanding of how EBV and KSHV similarly manipulate host cell membrane signals, particularly how remodeling of the cell membrane allows EBV and KSHV to avoid host antiviral immune responses and favors their latent and lytic infection.

The regulatory role of protein phosphorylation in human gammaherpesvirus associated cancers

Activation of specific sets of protein kinases by intracellular signal molecules has become more and more apparent in the past decade. Phosphorylation, one of key posttranslational modification events, is activated by kinase or regulatory protein and is vital for controlling many physiological functions of eukaryotic cells such as cell proliferation, differentiation, malignant transformation,and signal transduction mediated by external stimuli. Moreovers, the reversible modification of phosphorylation and dephosphorylation can result in different features of the target substrate molecules including DNA binding, protein-protein interaction, subcellular location and enzymatic activity, and is often hijacked by viral infection. Epstein-Barr virus(EBV) and Kaposi's sarcomaassociated herpesvirus(KSHV), two human oncogenic gamma-herpesviruses, are shown to tightly associate with many malignancies. In this review, we summarize the recent progresses on understanding of molecular properties and regulatory modes of cellular and viral proteins phosphorylation influenced by these two tumor viruses, and highlight the potential therapeutic targets and strategies against their related cancers.