A role for a new herpes virus (KSHV) in different forms of Kaposi's sarcoma

Analyses of Kaposi Sarcoma trends among adults establishing initial outpatient HIV care in Nigeria: 2006-2017

Background

The incidence of Human Immunodeficiency Virus (HIV)-associated Kaposi Sarcoma (KS) in the pre-antiretroviral therapy (ART) population remains high in several countries in sub-Saharan Africa. We examined trends of KS prevalence in adults, establishing initial outpatient HIV care from 2006 to 2017 in Nigeria.

Methods

We analyzed data of 16,431 adults (age ≥ 18 years) enrolled for HIV care from January 1, 2006, to December 31, 2017, in a large clinic in Jos, Nigeria. KS at enrollment was defined as KS recorded in the electronic health record within 30 days of clinic enrollment. Time trends were compared among four periods: 2006–2008, 2009–2011, 2012–2014, and 2015–2017 using logistic regression models. Annual trends were analyzed using join point regression and restricted splines.

Results

The study population had a mean age 35.1 (standard deviation, SD 9.5) years, and were 65.7% female (n = 10,788). The mean CD4 cell count was 220 (95% CI 117–223). The overall KS prevalence at entry was 0.59% (95% CI 0.48–0.72). Compared to 2006–2008, KS prevalence was significantly higher in 2009–2011 (adjusted odds ratio 5.07 (95% CI 3.12–8.24), p < 0.001), but remained unchanged in subsequent periods. Male sex and low CD4 T-cell count independently increased odds for KS.

Conclusions

Despite ART expansion, KS at enrollment showed no significant decline. The low CD4 cell count, across all periods, indicates delay in enrollment for HIV care, which increases KS risk. Interventions aimed at early HIV diagnosis and linkage to ART is critical to KS risk reduction in this population.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13027-022-00424-4.

KSHV transactivator-derived small peptide traps coactivators to attenuate MYC and inhibits leukemia and lymphoma cell growth

In herpesvirus replicating cells, host cell gene transcription is frequently down-regulated because important transcriptional apparatuses are appropriated by viral transcription factors. Here, we show a small peptide derived from the Kaposi's sarcoma-associated herpesvirus transactivator (K-Rta) sequence, which attenuates cellular MYC expression, reduces cell proliferation, and selectively kills cancer cell lines in both tissue culture and a xenograft tumor mouse model. Mechanistically, the peptide functions as a decoy to block the recruitment of coactivator complexes consisting of Nuclear receptor coactivator 2 (NCOA2), p300, and SWI/SNF proteins to the MYC promoter in primary effusion lymphoma cells. Thiol(SH)-linked alkylation for the metabolic sequencing of RNA (SLAM seq) with target-transcriptional analyses further confirm that the viral peptide directly attenuates MYC and MYC-target gene expression. This study thus provides a unique tool to control MYC activation, which may be used as a therapeutic payload to treat MYC-dependent diseases such as cancers and autoimmune diseases.

The Kaposi's Sarcoma-Associated Herpesvirus ORF34 Protein Interacts and Stabilizes HIF-2α via Binding to the HIF-2α bHLH and PAS Domains

Hypoxia and hypoxia inducible factors (HIFs) play important roles in the Kaposi's sarcoma-associated herpesvirus (KSHV) life cycle. KSHV is the causative agent of Kaposi's sarcoma (KS) and other AIDS-related malignancies. Kaposi's sarcoma is a highly vascular tumor, which preferentially develops in the lower extremities of the body where blood vessels are often poorly oxygenated. The main cellular responses to hypoxia are mediated mainly by two isoforms of HIF, HIF-1α and HIF-2α. HIF-1α and HIF-2α have common as well as distinct functions, although they are similar in structure and function. Previously, we showed that the KSHV ORF34 protein binds HIF-1α and facilitates its degradation through the ubiquitin-proteasome pathway causing negative regulation of HIF-1α-dependent genes (Haque and Kousoulas, J Virol 87:2164-2173, 2013, https://www.doi.org/10.1128/JVI.02460-12). Herein, we show that the ORF34 gene is involved in the regulation of KSHV lytic gene expression, since deletion of ORF34 resulted in reduced immediate early and early lytic gene expression and blocked late gene expression. Coimmunoprecipitation experiments revealed that the ORF34 protein physically interacted with HIF-2α in transfected as well as in KSHV-infected cells. Utilization of ORF34 truncations revealed that three distinct domains bind HIF-2α and that both bHLH and PAS domains of HIF-2α interacted with ORF34. Unlike HIF-1α, dose-dependent coexpression of ORF34 stabilized the HIF-2α protein, ensuring HIF-2α-dependent transcriptional activity. The ORF34 protein enhanced HIF-2α ubiquitination at the bHLH and PAS domains. The results show that the KSHV ORF34 protein is involved in the KSHV life cycle by regulating the expression of HIF-1α and HIF-2α proteins.IMPORTANCE Hypoxia inducible factor 1α (HIF-1α) and HIF-2α are transcription factors which play important roles in the Kaposi's sarcoma-associated herpesvirus (KSHV) latent and lytic gene replication. Herein, we show that the ORF34 gene is involved in the regulation of KSHV lytic gene expression, since deletion of ORF34 resulted in reduced immediate early and early lytic gene expression and blocked late gene expression. In addition, we demonstrate that the KSHV ORF34 protein binds and stabilizes HIF-2α, in contrast to its role in binding HIF-1α and causing its degradation via the proteasome pathway. Thus, the KSHV ORF34 protein plays a regulatory role in the KSHV life cycle by regulating HIF-1α and HIF-2α expression.

Anaplastic Kaposi's Sarcoma of the Adrenal in an HIV-negative Patient With Literature Review

Kaposi's sarcoma (KS) is a peculiar tumor of viral etiology, with the HHV8 rhadinovirus playing a fundamental role in its development. Several epidemiological categories of KS have been identified, of which the sporadic, endemic, iatrogenic, and the epidemic are the main ones. Several histologic disease morphologies have been described, such as inflammatory, angiomatous, spindle cell, mixed, and the anaplastic (sarcomatous) subtypes. The skin of the limbs is most commonly affected, but any other organ or site may be involved. Microscopically KS may enter the differential diagnosis with several different entities, and for this purpose the immunohistochemical detection of the viral latent nuclear antigen-1 (LNA-1) may be crucial. Sporadic KS is usually benign, but rarely it may be aggressive. Anaplastic histology heralds an ominous course in any clinical context. We report a case of anaplastic retroperitoneal KS, occurring in an HIV-negative adult man. This patient presented with a huge left suprarenal mass, which was totally resected, and initially diagnosed as inflammatory leiomyosarcoma, because of the monomorphic spindle cell tumor morphology. After 12 years the tumor recurred locally as an unresectable mass, which was biopsied and examined. At the time of recurrence, the histologic slides of the primary tumor were reviewed, and the previous diagnosis was changed to that of atypical KS. Histologically the recurrent tumor showed both spindle cell and epithelioid appearances. Strongly diffuse HHV8/LAN-1 immunopositivity was documented in both tumors. The final diagnosis for the entire case was anaplastic KS. Then, the patient died in a few months.

Macaque homologs of Kaposi's sarcoma-associated herpesvirus (KSHV) infect germinal center lymphoid cells, epithelial cells in skin and gastrointestinal tract and gonadal germ cells in naturally infected macaques

We developed a set of rabbit antisera to characterize infections by the macaque RV2 rhadinovirus homologs of KSHV. We analyzed tissues from rhesus and pig-tailed macaques naturally infected with rhesus rhadinovirus (RRV) or Macaca nemestrina rhadinovirus 2 (MneRV2). Our study demonstrates that RV2 rhadinoviruses have a tropism for epithelial cells, lymphocytes and gonadal germ cells in vivo. We observed latent infections in both undifferentiated and differentiated epithelial cells with expression of the latency marker, LANA. Expression of the early (ORF59) and late (glycoprotein B) lytic markers were detected in highly differentiated cells in epithelial ducts in oral, renal, dermal and gastric mucosal tissue as well as differentiated germ cells in male and female gonads. Our data provides evidence that epithelial and germ cell differentiation in vivo induces rhadinovirus reactivation and suggests that infected epithelial and germ cells play a role in transmission and dissemination of RV2 rhadinovirus infections in vivo.

Profiling of cellular microRNA responses during the early stages of KSHV infection

Kaposi's sarcoma-associated herpesvirus (KSHV) causes a variety of cancers, including Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman disease (MCD). Host cellular microRNAs (miRNAs) play important post-transcriptional regulatory roles in gene expression and can greatly influence virus-host cell interactions. This study investigated cellular miRNA expression profiles operating in response to early stages of KSHV infection of human Burkitt lymphoma B cells (BJAB). We employed deep sequencing to analyze miRNA expression in KSHV-infected BJAB cells 15 min post infection (PI) and compared this to uninfected BJAB cells. A total of 32 known miRNAs and 28 novel miRNA candidates were differentially expressed in KSHV-infected compared to uninfected BJAB cells. Interestingly, miRNA expression profiles during the early stages of viral infection yielded comparable results when UV-inactivated KSHV was used. The deep sequencing results were further confirmed by performing real-time reverse transcription PCR. The target genes predicted to be regulated by both the known and novel miRNAs are mainly involved in assisting virus entry, inducing critical cell signaling, initiating transcription of immediate early genes, promoting latent infection, and modulating the host immune response. For the first time, we provide insight into the host cellular miRNA expression profiles in response to early stages of KSHV infection of human B cells. Furthermore, this study offers a valuable basis for further investigation on the roles of cellular miRNAs in the KSHV entry process.

The Itch ubiquitin ligase is required for KSHV RTA induced vFLIP degradation

Expression of Kaposi's sarcoma herpesvirus vFLIP, a potent activator of NFkB signaling, promotes latency. Inhibition of NFkB signaling promotes lytic reactivation. We previously reported that lytic inducer, RTA, inhibits vFLIP induced NFkB signaling by inducing the degradation of vFLIP via the proteasome. Here we report that the cellular ubiquitin ligase, Itch, is required for RTA induced degradation of vFLIP. Expression of either Itch targeting shRNA or a dominant negative mutant of the ubiquitin ligase both increased the stability of vFLIP in the presence of RTA. Itch potently ubiquitinated vFLIP in vivo and in vitro. We provide evidence for interaction between RTA, vFLIP and Itch and we identified an RTA resistant mutant of vFLIP that is unable to interact with Itch. These observations contribute to our understanding of how RTA counteracts the activities of vFLIP.

Conceptual Emergence of Human Herpesvirus 8 (Kaposi’s Sarcoma-associated Herpesvirus) as an Oral Herpesvirus

Recognition of the various clinico-epidemiologic forms of Kaposi’s sarcoma, a disease putatively caused by an infectious agent, did not provide ready clues as to how that agent might be transmitted, although fecal and sexual routes were implicated. Application of serologic and genome-detection assays, and cell-culture studies following the identification of human herpesvirus 8 as the causative agent now implicate that virus as one that is orally shed. While oral transmission of the virus might account for the viral endemicity in Africa and Mediterranean countries, why it is particularly prevalent among male homosexuals in the West remains more difficult to explain. Such explanation may be sought from behavioral studies into the role saliva plays in sexual interactions.

Brief Report: A Phase 1b/Pharmacokinetic Trial of PTC299, a Novel PostTranscriptional VEGF Inhibitor, for AIDS-Related Kaposi's Sarcoma: AIDS Malignancy Consortium Trial 059

Vascular endothelial growth factor (VEGF) plays an important role in Kaposi's sarcoma (KS). We administered PTC299, a post-transcriptional inhibitor of pathogenic VEGF, to persons with HIV-related KS. Seventeen participants received 3 different doses of PTC299. Adverse events typically observed with VEGF inhibition were absent. Three participants had partial tumor responses and 11 had stable disease. There were no differences in exposure to PTC299 by antiretroviral regimen. Serum VEGF, but not KS-associated herpesvirus DNA, decreased on treatment. Given redundancies in the VEGF feedback loop, future trials should consider combining PTC299 with agents that inhibit different pathways implicated in KS and KS-associated herpesvirus proliferation.

Analysis of the Prevalence of HTLV-1 Proviral DNA in Cervical Smears and Carcinomas from HIV Positive and Negative Kenyan Women

The oncogenic retrovirus human T-cell lymphotropic virus type 1 (HTLV-1) is endemic in some countries although its prevalence and relationship with other sexually transmitted infections in Sub-Saharan Africa is largely unknown. A novel endpoint PCR method was used to analyse the prevalence of HTLV-1 proviral DNA in genomic DNA extracted from liquid based cytology (LBC) cervical smears and invasive cervical carcinomas (ICCs) obtained from human immunodeficiency virus-positive (HIV+ve) and HIV-negative (HIV−ve) Kenyan women. Patient sociodemographic details were recorded by structured questionnaire and these data analysed with respect to HIV status, human papillomavirus (HPV) type (Papilocheck^®) and cytology. This showed 22/113 (19.5%) of LBC’s from HIV+ve patients were positive for HTLV-1 compared to 4/111 (3.6%) of those from HIV−ve women (p = 0.0002; odds ratio (OR) = 6.42 (2.07–26.56)). Only 1/37 (2.7%) of HIV+ve and none of the 44 HIV−ve ICC samples were positive for HTLV-1. There was also a significant correlation between HTLV-1 infection, numbers of sexual partners (p < 0.05) and smoking (p < 0.01). Using this unique method, these data suggest an unexpectedly high prevalence of HTLV-1 DNA in HIV+ve women in this geographical location. However, the low level of HTLV-1 detected in HIV+ve ICC samples was unexpected and the reasons for this are unclear.

Kaposi's Sarcoma-Associated Herpesvirus Subversion of the Anti-Inflammatory Response in Human Skin Cells Reveals Correlates of Latency and Disease Pathogenesis

KSHV is the etiologic agent for Kaposi's sarcoma (KS), a neoplasm that manifests most aggressively as multifocal lesions on parts of human skin with a propensity for inflammatory reactivity. However, mechanisms that control evolution of KS from a benign hyperplasia to the histologically complex cutaneous lesion remain unknown. In this study, we found that KSHV induces proteomic and morphological changes in melanocytes and melanoma-derived cell lines, accompanied by deregulation of the endogenous anti-inflammatory responses anchored by the MC1-R/α-MSH signaling axis. We also identified two skin-derived cell lines that displayed differences in ability to support long-term KSHV infection and mapped this dichotomy to differences in (a) NF-κB activation status, (b) processing and expression of KSHV latency-associated nuclear antigen isoforms putatively associated with the viral lytic cycle, and (c) susceptibility to virus-induced changes in expression of key anti-inflammatory response genes that antagonize NF-κB, including MC1-R, POMC, TRP-1, and xCT. Viral subversion of molecules that control the balance between latency and lytic replication represents a novel correlate of KSHV pathogenesis and tropism in skin and underscores the potential benefit of harnessing the endogenous anti-inflammatory processes as a therapeutic option for attenuating cutaneous KS and other proinflammatory outcomes of KSHV infection in high-risk individuals.

Phase II trial of imatinib in AIDS-associated Kaposi's sarcoma: AIDS Malignancy Consortium Protocol 042

PURPOSE

Kaposi's sarcoma (KS) is a disease of multifocal vascular proliferation that requires infection with KS herpes virus (KSHV/HHV-8). Activation of the c-kit and platelet-derived growth factor (PDGF) receptors by autocrine/paracrine mechanisms follows endothelial cell KSHV infection. In a pilot study, imatinib, a c-kit/PDGF-receptor inhibitor, induced partial regression of AIDS-associated KS (AIDS-KS) in five of 10 patients.

PATIENTS AND METHODS

This multicenter phase II study was designed to estimate the response rate to imatinib in AIDS-KS. Secondary objectives included investigation of predictors of response and imatinib pharmacokinetics in patients on antiretrovirals. Patients received imatinib 400 mg/day by mouth for up to 12 months with dose escalation up to 600 mg/day at 3 months if their disease was stable.

RESULTS

Thirty patients were treated at 12 AIDS Malignancy Consortium sites. Ten patients (33.3%) achieved partial response, six (20%) had stable disease, and seven (23.3%) exhibited KS progression. Nine patients completed 52 weeks of imatinib therapy. The median treatment duration was 22.5 weeks. Only five patients (16.7%) discontinued therapy owing to adverse events. Antiretroviral regimens did not significantly alter imatinib metabolism. Activating mutations in PDGF-R and c-kit were not found at baseline or at disease progression. We found no correlation with response with changes in any of the candidate cytokines.

CONCLUSION

Imatinib has activity in AIDS-KS. Pharmacokinetic interactions with antiretroviral drugs did not correlate with toxicity. Thirty percent of patients showed long-term clinical benefit and remained on imatinib for the entire year. These results suggest imatinib is well tolerated and may be an alternative therapy for some patients with AIDS-KS.

Pemphigus vulgaris-associated Kaposi's sarcoma: response to paclitaxel and review of the literature

Systemic corticosteroids have long been the mainstay of treatment for pemphigus patients. However, the necessity of their high-dose and long-term administration has brought about a number of complications, sometimes causing significant morbidities. Maintaining a balance between therapeutic and undesirable effects of medications is not always easily achievable. Therefore, additional treatment modalities are frequently needed to control side-effects. Kaposi's sarcoma (KS) is a rare, potentially life-threatening complication in this setting. Due to the rarity of data on pemphigus-associated KS treatment, the best therapeutic approach is still undecided. Here, we report two cases of pemphigus patients who had developed extensive KS as a result of severe immunosuppressive therapy and were successfully treated with paclitaxel. In addition, we performed a review of literature to assess the results of the previously employed treatment modalities in this setting.

Antiviral activity of (+)-rutamarin against Kaposi's sarcoma-associated herpesvirus by inhibition of the catalytic activity of human topoisomerase II

Kaposi's sarcoma-associated herpesvirus (KSHV) is an etiological agent of several AIDS-associated malignancies, including Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD). Its lytic replication cycle has been proven to be critical for the pathogenesis of KSHV-associated diseases. In KS lesions, lytic viral replication, production of virion particles, and reinfection of endothelial cells are essential to sustain the population of infected cells that otherwise would be quickly lost as spindle cells divide. Thus, antivirals that block KSHV replication could be a strategy in the treatment of KSHV-associated diseases. However, there is no effective anti-KSHV drug currently available. Our previous work showed that human topoisomerase II (Topo II) is indispensable for KSHV lytic replication and is suggested to be an effective target for antiviral drugs. Here, we report the discovery and characterization of a novel catalytic inhibitor of human Topo IIα, namely, (+)-rutamarin. The binding mode of (+)-rutamarin to the ATPase domain of human Topo IIα was established by docking and validated by molecular dynamics (MD) simulations. More importantly, (+)-rutamarin efficiently inhibits KSHV lytic DNA replication in BCBL-1 cells with a half-maximal inhibitory concentration (IC50) of 1.12 μM and blocks virion production with a half-maximal antiviral effective concentration (EC50) of 1.62 μM. It possesses low cytotoxicity, as indicated by the selectivity index (SI) of 84.14. This study demonstrated great potential for (+)-rutamarin to become an effective drug for treatment of human diseases associated with KSHV infection.

High prevalence of early childhood infection by Kaposi's sarcoma-associated herpesvirus in a minority population in China

In China, KSHV seroprevalence varies considerably among different regions and ethnicities. But in Xinjiang province, located in the northwestern China, there is a very high seroprevalence of KSHV in adults of Kazak and Ughur ethnicities. However, KSHV prevalence in children and the risk factors associated with the acquisition of infection are currently not known. The aim of this study was to investigate the prevalence of KSHV infection and identify associated socioeconomic or behavioural risk factors and the humoral immune response among children in this population. This is a cross-sectional study (N = 178) to screen children and their caregivers from Xinjiang for total KSHV antibodies, KSHV neutralizing antibodies and HIV infection. Structured questionnaires were utilized to investigate risk factors associated with KSHV prevalence. KSHV seroprevalence in children and caregivers in Xinjiang was 48.3% and 64.7%, respectively. Neutralizing antibody was detected in most seropositive caregivers (93.8%) but was detected in only 5.8% of the infected children. A significant association was observed between child KSHV seroprevalence and sharing of food among family members. These results suggest that similar to other endemic areas in Africa, KSHV infection in the minority populations of Xinjiang is likely to be occurring during early childhood, probably via horizontal transmission through saliva, and results in high seroprevalence in the adult population.

Construction and identification of recombinant lentiviral vector containing HIV-1 Tat gene and its expression in 293T cells

Objective

To construct a lentiviral vector expressing HIV-1 Tat and identify its expression in 293T cells.

Methods

The gene fragment of HIV-1 Tat₁₀₁ was subcloned to lentiviral transfer vector pHAGE-CMV-MCS-IZsGreen, which was named pHAGE-Tat. Then the constructed pHAGE-Tat was used to co-transfect the packing 293T cells, together with the packaging plasmids pMD2.G and psPAX2. The packaged viral particles designated LV-Tat were used to infect the 293T cells and the viral titer was calculated. The expression of HIV-1 Tat in 293T cells was confirmed using RT-PCR and western blot.

Results

The recombinant lentiviral vector was successfully constructed and could express HIV-1 Tat in 293T cells. The virus titer was 5.73×10⁶ ifu/ml.

Conclusion

The successfully constructed recombinant lentiviral vector makes a strong foundation for further exploring the possible role of HIV-1 Tat in the development of prostate cancer.

An update on viral association of human cancers

Up to now, seven viruses that infect humans have been identified as oncogenic and are closely associated with different human cancers. Most of them encode oncogenes whose products play important roles in the development of cancers in the context of environmental and genetic factors; others may act via indirect mechanisms. The transforming activities of the human oncogenic viruses have much in common with the well-studied tumorigenic processes elicited by the acutely transforming murine retroviruses. Many of these mechanisms have been elucidated for or are represented in the successive steps leading to the efficient in vitro immortalization by the lymphotropic herpesvirus Epstein-Barr virus, although the establishment of malignancy in vivo takes longer. The development of cancer is a complicated process involving multiple factors, from the host and the environment. Although any one of these etiologic factors may exert an effect on the carcinogenic process, vaccination against the viral pathogen in several cases has shown efficacy in preventing the spread of the virus and, in turn, the development of the associated cancers. Modern laboratory techniques can be expected to facilitate the identification of new emerging viruses whose association with malignancies is suggested by epidemiologic and clinical data.

The Kaposi's sarcoma-associated herpesvirus ORF34 protein binds to HIF-1α and causes its degradation via the proteasome pathway

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent for Kaposi's sarcoma (KS) and two other lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). Kaposi's sarcoma is a highly vascular tumor, and recently both hypoxia-inducible factor 1α (HIF-1α) and HIF-2α were detected in KS samples, indicating a role of HIFs in the KSHV life cycle. Previously, we showed that ORF34, a lytic gene of unassigned function, was activated by hypoxia and that ORF34 transcription was upregulated by both HIFs (M. Haque, D. A. Davis, V. Wang, I. Widmer, and R. Yarchoan, J Virol. 77:6761-6768, 2003). In the present study, we show that coexpression of ORF34 with HIF-1αm (degradation-resistant HIF-1α) caused substantial reduction in HIF-1α-dependent transcription, as evidenced by reporter assays. Two-way immunoprecipitation experiments revealed that ORF34 physically interacted with HIF-1αm in transient expression experiments. Deletion analysis revealed that three different ORF34 domains interacted with the amino-terminal domain of HIF-1α. Also, purified HIF-1α and ORF34 proteins interacted with each other. The observed transcriptional inhibition of HIF-1α-dependent promoters was attributed to degradation of HIF-1α after binding with ORF34, since the overall amount of wild-type HIF-1α but not the degradation-resistant one (HIF-1αm) was reduced in the presence of ORF34. Moreover, ORF34 caused degradation of HIF-1α in a dose-dependent manner. Inhibition of the ubiquitin-dependent pathway by the chemical proteasome inhibitor MG132 prevented HIF-1α degradation in the presence of ORF34. These results show that ORF34 binds to HIF-1α, leading to its degradation via the proteasome-dependent pathway.

Tegument Proteins of Kaposi's Sarcoma-Associated Herpesvirus and Related Gamma-Herpesviruses

A herpesvirus virion is composed of a viral genomic DNA-containing capsid surrounded by a viral envelope with glycoprotein spikes on its surface. Located between the capsid and the outer viral envelope is the virion tegument layer. Though the majority of the virion proteins are located in the tegument, this layer is less studied and was thought to be an amorphous structure. Over the last decade, a number of studies have indicated the presence of organized tegument structures across the spectrum of herpesviruses, implicating tegument components in critical steps governing the viral life cycle. In the case of Kaposi’s sarcoma-associated herpesvirus (KSHV), the etiological agent of Kaposi’s sarcoma, several functions exerted by tegument proteins at different stages of the viral life cycle, inclusive of primary de novo infection and virion assembly, have been identified over the last several years. In this review, KSHV tegument components are cataloged and the occurrence of organized tegument structures in KSHV, built through interactions amongst the different virion proteins, is discussed in depth. The significant functional roles of the KSHV tegument proteins at different stages of the viral life cycle are elaborated under separate headings. Definitive functional roles exerted by tegument proteins of related gamma-herpesviruses are also discussed. Since tegument proteins play key roles during viral assembly, viral entry, and represent an important interface for virus–host interactions, further research in this area should provide detailed insights into the functional capacity of the KSHV tegument, resulting in a better understanding of the viral life cycle.

Novel monoclonal antibodies for identification of multicentric Castleman's disease; Kaposi's sarcoma-associated herpesvirus-encoded vMIP-I and vMIP-II

Recent studies have indicated that vMIP-I and vMIP-II play important roles in the pathogenesis of Kaposi's sarcoma-associated herpesvirus (KSHV)-related diseases due to the effects of these proteins on vascularization. We developed monoclonal antibodies against KSHV-encoded viral macrophage inflammatory protein-I (vMIP-I) and vMIP-II to study these expression profiles and reveal the pathogenesis of KSHV-related diseases. The MAbs against vMIP-I and vMIP-II reacted to KSHV-infected cell lines after lytic induction. Both vMIP-I and the vMIP-II gene products were detected 24 h post-induction with 12-O-tetradecanoylphorbol-13-acetate until 60 h in the cytoplasm of primary effusion lymphoma cell lines. In clinical specimens, both vMIP-I and vMIP-II gene products were detected in the tissues of patients with multicentric Castleman's disease. On the other hand, only vMIP-II was detected in a subset of Kaposi's sarcoma. We concluded that these antibodies might be powerful tools to elucidate the pathogenesis of KSHV-related diseases.

Seroprevalence and risk factors of Kaposi's sarcoma-associated herpesvirus infection among the general Uygur population from south and north region of Xinjiang, China

Background

Kaposi sarcoma (KS) is a complex multifocal neoplasm and is the major cause of death for about 50% of acquired immunodeficiency syndrome (AIDS) patients. Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus with a causal role in the development of all types of KS. KS is prevalent among the Uygur people in Xinjiang, especially in south area. Here we carried out a cross-sectional study among 1534 general Uygur individuals from south and north region of Xinjiang to assess the seroprevalence of KSHV and to identify the potential correlation between KSHV seroprevalence and KS incidence.

Results

Seroprevalence of KSHV in South and North Xinjiang was 23.1% and 25.9%, respectively. Older age was independently associated with higher KSHV seroprevalence. In subjects from South Xinjiang, lower educational level and reported drinking were each independently associated with higher KSHV seroprevalence. Furthermore, the antibody titer was significantly lower in both south and north KSHV seropositive individuals compared with KS patients, as analyzed by gradient dilution (P < 0.001).

Conclusion

KSHV is highly prevalent in the general Uygur population in both South and North Xinjiang. Interestingly, the infection rate of KSHV in these two geographical areas did not correlate well with KS incidence. Perhaps unknown factors exist that promote the progression of KSHV infection to KS development in the local minority groups.

Phase II AIDS Malignancy Consortium trial of topical halofuginone in AIDS-related Kaposi sarcoma

Using a novel blinded intrapatient vehicle control design, we conducted a phase II study of topically administered halofuginone, an angiogenesis inhibitor that inhibits collagen type-I and matrix metalloproteinases (MMPs), in patients with AIDS-related Kaposi sarcoma. Serial Kaposi sarcoma biopsies assessed treatment effects on angiogenic factors and Kaposi sarcoma herpesvirus-latency associated nuclear antigen-1 (KSHV-LANA). We observed marked heterogeneity of KSHV-LANA expression. Although the small number of subjects whose response could be evaluated precluded definitive assessment of halofuginone's efficacy, we observed a significant decrease in type-I collagen only in halofuginone-treated lesions, but no effect on MMP-2. The trial design is applicable to future studies of topical agents.

Whole-exome sequencing-based discovery of STIM1 deficiency in a child with fatal classic Kaposi sarcoma

Whole-exome sequencing reveals a homozygous splice-site mutation in the gene encoding STIM1 in a child with classic Kaposi sarcoma.

Classic Kaposi sarcoma (KS) is exceedingly rare in children from the Mediterranean Basin, despite the high prevalence of human herpesvirus-8 (HHV-8) infection in this region. We hypothesized that rare single-gene inborn errors of immunity to HHV-8 may underlie classic KS in childhood. We investigated a child with no other unusually severe infectious or tumoral phenotype who died from disseminated KS at two years of age. Whole-exome sequencing in the patient revealed a homozygous splice-site mutation in STIM1, the gene encoding stromal interaction molecule 1, which regulates store-operated Ca²⁺ entry. STIM1 mRNA splicing, protein production, and Ca²⁺ influx were completely abolished in EBV-transformed B cell lines from the patient, but were rescued by the expression of wild-type STIM1. Based on the previous discovery of STIM1 deficiency in a single family with a severe T cell immunodeficiency and the much higher risk of KS in individuals with acquired T cell deficiencies, we conclude that STIM1 T cell deficiency precipitated the development of lethal KS in this child upon infection with HHV-8. Our report provides the first evidence that isolated classic KS in childhood may result from single-gene defects and provides proof-of-principle that whole-exome sequencing in single patients can decipher the genetic basis of rare inborn errors.

Bub1 and CENP-F can contribute to Kaposi's sarcoma-associated herpesvirus genome persistence by targeting LANA to kinetochores

The latency-associated nuclear antigen (LANA) encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) is critical for segregation of viral episomes to progeny nuclei and allows for maintenance of the viral genome in newly divided daughter cells. LANA binds to KSHV terminal repeat (TR) DNA and simultaneously associates with chromatin-bound cellular proteins. This process tethers the viral episomes to host chromosomes. However, the mechanism of tethering is complex and involves multiple protein-protein interactions. Our previous proteomics studies which showed the association of LANA with centromeric protein F (CENP-F) prompted us to further study whether LANA targets centromeric proteins for persistence of KSHV episomes during cell division. Here we show that LANA colocalized with CENP-F as speckles, some of which are paired at centromeric regions of a subset of chromosomes in KSHV-infected JSC-1 cells. We also confirm that both the amino and carboxy termini of LANA can bind to CENP-F. Moreover, LANA associated with another kinetochore protein, Bub1 (budding uninhibited by benzimidazole 1), which is known to form a complex with CENP-F. Importantly, we demonstrated the dynamic association of LANA and Bub1/CENP-F and the colocalization between Bub1, LANA, and the KSHV episome tethered to the host chromosome using fluorescence in situ hybridization (FISH). Knockdown of Bub1 expression by lentivirus-delivered short hairpin RNA (shRNA) dramatically reduced the number of KSHV genome copies, whereas no dramatic effect was seen with CENP-F knockdown. Therefore, the interaction between LANA and the kinetochore proteins CENP-F and Bub1 is important for KSHV genome tethering and its segregation to new daughter cells, with Bub1 potentially playing a more critical role in the long-term persistence of the viral genome in the infected cell.

Kaposi's sarcoma in a patient treated with imatinib mesylate for chronic myeloid leukemia

BACKGROUND

Chronic myeloid leukemia (CML) is a myeloproliferative disorder primarily characterized by the presence of the Philadelphia chromosome resulting from a reciprocal translocation between the long arms of chromosomes 9 and 22. This translocation determines a fusion gene, bcr-abl, which encodes a constitutively active protein, tyrosine kinase, resulting in decreased apoptosis, defective adhesion, and genomic instability in transformed cells. The tyrosine kinase activity and its effects represent a potential pharmacologic target of tyrosine kinase inhibitors, such as imatinib. Flare of Kaposi's sarcoma (KS) is well described in immunosuppressed patients treated with corticosteroids and rituximab, but has not yet been reported during treatment with imatinib.

OBJECTIVE

We report a case of cutaneous KS lesions in a patient affected by CML treated with imatinib.

CASE SUMMARY

A 61-year-old white male patient (weight, 90 kg) was diagnosed with CML in March 2006 at the Division of Hematology, University of Rome "Tor Vergata," Rome, Italy. He was treated with imatinib 400 mg/d, which improved his general condition with few adverse effects. After 12 months of treatment, molecular biology showed an important reduction in the peripheral blood of the fusion oncoprotein bcr-abl p210-b3a2. However, at the same time, multiple cutaneous violaceous papular-nodular lesions appeared on his left forearm. A punch biopsy showed the presence of KS, whereas a polymerase chain reaction assay documented the presence of human herpes virus type 8 (HHV8) DNA in the skin lesion. Serologic HIV was negative and HHV8 viremia was under the limit of quantitation of the assay. Total body computed tomography scan did not reveal any mucosal or visceral lesion.

CONCLUSIONS

We present a case of a patient with CML who developed KS 12 months after starting treatment with imatinib 400 mg/d. The mechanism behind the development of the cutaneous lesions is unclear, and could have either a casual clinical association or be related to the study drug. According to the Naranjo adverse drug reaction probability scale, the development of KS in this case was probably associated with the imatinib treatment (score, 5-8).

Multiple oncogenic viruses identified in Ocular surface squamous neoplasia in HIV-1 patients

BACKGROUND

Ocular surface squamous neoplasia (OSSN) is a rare cancer that has increased in incidence with the HIV pandemic in Africa. The underlying cause of this cancer in HIV-infected patients from Botswana is not well defined.

RESULTS

Tissues were obtained from 28 OSSN and 8 pterygia patients. The tissues analyzed from OSSN patients were 83% positive for EBV, 75% were HPV positive, 70% were KSHV positive, 75% were HSV-1/2 positive, and 61% were CMV positive by PCR. Tissues from pterygium patients were 88% positive for EBV, 75% were HPV positive, 50% were KSHV positive, and 60% were CMV positive. None of the patients were JC or BK positive. In situ hybridization and immunohistochemistry analyses further identified HPV, EBV, and KSHV in a subset of the tissue samples.

CONCLUSION

We identified the known oncogenic viruses HPV, KSHV, and EBV in OSSN and pterygia tissues. The presence of these tumor viruses in OSSN suggests that they may contribute to the development of this malignancy in the HIV population. Further studies are necessary to characterize the molecular mechanisms associated with viral antigens and their potential role in the development of OSSN.

Human herpesvirus-8 in northwestern China: epidemiology and characterization among blood donors

Background

Human herpes virus 8 (HHV-8) is the etiologic agent associated with development of classical, AIDS-related, iatrogenic, and endemic Kaposi's sarcoma (KS). Several studies provide strong evidence that HHV-8 can be transmitted by blood transfusion. We evaluated the seroprevalence and potential risk factors of HHV-8 infection in blood donors in one region. We surveyed HHV-8 infection among 4461 blood donors in Xinjiang, China, a unique endemic area for HHV-8 and KS.

Results

The HHV-8 seroprevalence was higher in local minority groups which comprise most KS cases in China, than in Han people. HHV-8 prevalence was 18.6% in the Han ethnic group, 25.9% in Uygur subjects, 29.2% in Kazak subjects, 36.8% in Mongolian subjects, and 21.9% in other ethnic groups. In several subgroups, the time of donation of whole blood seemed to be a risk factor. In HHV-8-seropositive subjects, a larger fraction of local minorities (23.9%) had high HHV-8 titers than that of Han subjects (9.2%). HHV-8 infection was associated with ethnicity and residence.

Conclusion

HHV-8 seroprevalence was significantly high among blood donors in Xinjiang, where the prevalence of KS correlates with HHV-8 prevalence and titers in Uygur and Kazak ethnic groups. Blood exposure represented by the frequency of blood donation indicated a possible blood-borne transmission route of HHV-8 in Xinjiang. Detecting anti-HHV-8 antibodies before donation in this region is therefore important.

Low-affinity Fcgamma receptors, autoimmunity and infection

Low-affinity Fcgamma receptors (FcgammaRs) mediate the effects of immunoglobulin G (IgG) antibodies on leukocytes, including recruitment to inflammatory lesions, phagocytosis, antibody-dependent cellular cytotoxicity, release of inflammatory mediators and regulation of B cell activation. These functions are an important part of the mammalian response to infection, but if deployed inappropriately can cause autoimmune disease. Although most FcgammaRs are activatory, there is also an inhibitory FcgammaR that, when bound to IgG immune complexes, is able to downregulate the effects of both the activatory FcgammaRs and the B cell receptor. This review discusses the role of the low-affinity FcgammaRs in a balanced immune response and how perturbations in FcgammaR function result in susceptibility to infection or autoimmunity.

Seroprevalence of Kaposi's sarcoma-associated herpesvirus and risk factors in Xinjiang, China

Xinjiang, China is an endemic area for Kaposi's sarcoma (KS) but the seroprevalence of Kaposi's sarcoma-associated herpesvirus (KSHV) and risk factors remain undefined. In this study, antibodies to one KSHV latent protein (ORF73) and two KSHV lytic proteins (ORF65 and ORF-K8.1) were examined in 2,228 subjects from the general population and 37 subjects infected with HIV-1 in Xinjiang, and 560 subjects from the general population in Hubei, a low KS incidence region. The serostatus of a serum sample was defined based on positive results in any one of the three serologic assays. The seroprevalence of KSHV in the general population was higher in Xinjiang than in Hubei (19.2% vs. 9.5%; odds ratios [OR], 2.28; 95% confidence interval [CI], 1.68-3.08; P < 0.001). Among the ethnic groups in Xinjiang, 68 (15.8%) Han, 182 (20.7%) Uygur, 140 (19.9%) Hazakh, 9 (33.3%) Xibo, and 29 (16.8%) Hui were KSHV-seropositive, respectively. Compared to the Han, the latter groups had an increase in the risk of KSHV of 62.2%, 63.8%, 180.1%, and 30.2% (P = 0.003, 0.004, 0.018, and 0.286, respectively). Subjects aged <20, 20-50, and >50 had a seroprevalence of KSHV of 11.8%, 17.9%, and 24.6%, respectively. Compared to subjects aged <20, the latter groups had an increase in the risk of KSHV of 63.3% and 144.5% (P = 0.009 and <0.001, respectively). Subjects infected with HIV-1 in Xinjiang had a seroprevalence of KSHV of 43.2%, and a 220% increase in the risk of KSHV compared to the general population (P < 0.001). Similar results were obtained when the seroprevalence of KSHV was analyzed with any single or two of the three serologic assays alone. Genotyping identified three unique sequences clustered in the A clade. This study indicates that Xinjiang has a high seroprevalence of KSHV. Geographic location, ethnicity, age and HIV-1 infection are risk factors. Serologic and genotyping results suggest the introduction of KSHV into Xinjiang by specific ethnic groups.

LANA-1, Bcl-2, Mcl-1 and HIF-1alpha protein expression in HIV-associated Kaposi sarcoma

Human herpesvirus 8 (HHV8) is necessary for Kaposi sarcoma (KS) to develop, but whether the tissue viral load is a marker of KS progression is still unclear. Little is known about the level of expression of apoptosis-regulating proteins and of hypoxia-inducible factors (HIFs) in KS tumour cells relative to HHV8 expression. We therefore investigated the expression of the latency-associated nuclear antigen (LANA-1) of HHV8, Bcl-2, Mcl-1, Bax, Bcl-xL, caspase 3 and HIF-1alphain KS tissue specimens at different stages of the disease. The expression of these proteins was evaluated immunohistochemically using tissue microarrays (TMAs) in tissue specimens from 245 HIV-positive patients at different stages of the disease. Both LANA-1 and HIF-1alpha were expressed in KS biopsies taken at different stages, but their level increased throughout tumour progression. Additionally, the levels of Bcl-2 and Mcl-1 were higher in visceral KS lesions compared to levels observed in cutaneous and mucosal KS. This study demonstrates that late tumour stages of KS in tissues from HIV-positive patients are associated with high levels of LANA-1, HIF-1alpha and of the anti-apoptotic proteins, Bcl-2 and Mcl-1. Finally, the expression of these proteins can be potentially used as a tissue biomarker in defining patients with a higher risk of disease progression.

AIDS and non AIDS-related malignant lymphoma in Tanzania

BACKGROUND

Malignant lymphoma (ML) in HIV patients, are second in frequency to Kaposi's sarcoma (AKS) as AIDS-defining tumors. In Africa the frequency of AIDS-related lymphoma (ARL) is rare and the findings are controversial. Kaposi's sarcoma (KS) lesions are now causally associated with KSHV/HHV-8 but whether African ARL shows this association is not clear.

METHOD

Cancer registry data was reviewed for retrospective cases. Both retrospective and prospective lymphoma cases were classified according to the revised European-American (REAL) classification. Immunephenotyping was performed on both frozen and fixed paraffin sections. Viral DNA was assessed by polymerase chain reaction (PCR) of formalin fixed or frozen biopsies. In situ hybridization (ISH) was used to determine the presence of EBV encoded RNA (EBER).

OBJECTIVES

To determine the frequency and type of AIDS and non-AIDS related malignant lymphoma in Tanzania and a possible co-association with KSHV/HHV-8 and EBV.

RESULTS

An overall increasing tendency for ML in Tanzania was observed during 1991-94 and a clear increase from 1993. The tumors were classified as Burkitt's (6), diffuse large cell (10), precursor-B lymphoblastic (1) and Hodgkin's disease (5) from HIV positive and negative patients. Ten (40%) high grade ML and three Hodgkin's lymphoma from HIV patients had HHV-8 DNA. These findings were not related to age, sex or type of lymphoma. There was no association of HHV-8 with the lymphoma cells. Epstein-Barr virus (EBV) was demonstrable in most (13/18; 72%) of the tested tumors and seven (31.8%) had both HHV-8 and EBV.

CONCLUSIONS

This study suggests an overall increased frequency of ML patients infected with HHV-8 in Tanzania particularly in HIV patients which may result from the well established high HHV-8 prevalence in the general population, but HHV-8 was not associated with ARL pathogenesis as reflected by lack of tumor cell infection. As opposed to EBV, measures targeting HHV-8 for control of ML may therefore not be appropriate.

The role of infectious agents in the etiology of ocular adnexal neoplasia

Given the fact that infectious agents contribute to around 18% of human cancers worldwide, it would seem prudent to explore their role in neoplasms of the ocular adnexa: primary malignancies of the conjunctiva, lacrimal glands, eyelids, and orbit. By elucidating the mechanisms by which infectious agents contribute to oncogenesis, the management, treatment, and prevention of these neoplasms may one day parallel what is already in place for cancers such as cervical cancer, hepatocellular carcinoma, gastric mucosa-associated lymphoid tissue lymphoma and gastric adenocarcinoma. Antibiotic treatment and vaccines against infectious agents may herald a future with a curtailed role for traditional therapies of surgery, radiation, and chemotherapy. Unlike other malignancies for which large epidemiological studies are available, analyzing ocular adnexal neoplasms is challenging as they are relatively rare. Additionally, putative infectious agents seemingly display an immense geographic variation that has led to much debate regarding the relative importance of one organism versus another. This review discusses the pathogenetic role of several microorganisms in different ocular adnexal malignancies, including human papilloma virus in conjunctival papilloma and squamous cell carcinoma, human immunodeficiency virus in conjunctival squamous carcinoma, Kaposi sarcoma-associated herpes virus or human herpes simplex virus-8 (KSHV/HHV-8) in conjunctival Kaposi sarcoma, Helicobacter pylori (H. pylori,), Chlamydia, and hepatitis C virus in ocular adnexal mucosa-associated lymphoid tissue lymphomas. Unlike cervical cancer where a single infectious agent, human papilloma virus, is found in greater than 99% of lesions, multiple organisms may play a role in the etiology of certain ocular adnexal neoplasms by acting through similar mechanisms of oncogenesis, including chronic antigenic stimulation and the action of infectious oncogenes. However, similar to other human malignancies, ultimately the role of infectious agents in ocular adnexal neoplasms is most likely as a cofactor to genetic and environmental risk factors.

Prevalence of Kaposi's sarcoma among adult HIV-seropositive patients seen in a designated HIV treatment and care center in Abuja, Nigeria

BACKGROUND

There is a dearth of information on the prevalence of AIDS-associated Kaposi's sarcoma (AAKS) in Nigeria despite the HIV National seroprevalence of 5% and the occurrence of the disease in people living with HIV/AIDS.

OBJECTIVE

To determine the prevalence of AAKS among HIV-seropositive adults seen in an HIV/AIDS treatment and care center in Abuja, Nigeria.

DESIGN

This was a retrospective study of all cases seen over a period of 42 months.

METHOD

Medical records of the 1591 patients comprising 857 males and 734 females were reviewed, and relevant data such as age, sex, CD4 count at diagnosis of AAKS were obtained and analyzed.

RESULTS

A prevalence of 0.8% was found, with a male:female ratio of 2:1. Females presented at earlier ages and relatively lower CD4 count than did males.

CONCLUSION

Easy access to antiretroviral medications and a well-targeted education and awareness campaign will help reduce the incidence and prevalence of the disease. The inability to perform histologic examinations on all suspected cases calls for a well-designed prospective study to determine the actual prevalence of Kaposi's sarcoma in HIV-seropositive patients in Nigeria.

HIV-1 Tat and AIDS-associated cancer: targeting the cellular anti-cancer barrier?

The acquired immunodeficiency syndrome (AIDS) is accompanied by a significant increase in the incidence of neoplasms. Several causative agents have been proposed for this phenomenon. These include immunodeficiency and oncogenic DNA viruses and the HIV-1 protein Tat. Cancer in general is closely linked to genomic instability and DNA repair mechanisms. The latter maintains genomic stability and serves as a cellular anti-cancer barrier. Defects in DNA repair pathway are associated with carcinogenesis.

This review focuses on newly discovered connections of the HIV-1 protein Tat, as well as cellular co-factors of Tat, to double-strand break DNA repair. We propose that the Tat-induced DNA repair deficiencies may play a significant role in the development of AIDS-associated cancer.

Identification of a contemporary human parechovirus type 1 by VIDISCA and characterisation of its full genome

Background

Enteritis is caused by a spectrum of viruses that is most likely not fully characterised. When testing stool samples by cell culture, virus isolates are sometimes obtained which cannot be typed by current methods. In this study we used VIDISCA, a virus identification method which has not yet been widely applied, on such an untyped virus isolate.

Results

We found a human parechovirus (HPeV) type 1 (strain designation: BNI-788st). Because genomes of contemporary HPeV1 were not available, we determined its complete genome sequence. We found that the novel strain was likely the result of recombination between structural protein genes of an ancestor of contemporary HPeV1 strains and nonstructural protein genes from an unknown ancestor, most closely related to HPeV3. In contrast to the non-structural protein genes of other HPeV prototype strains, the non-structural protein genes of BNI-788st and HPeV3 prototype strains did not co-segregate in bootscan analysis with that of other prototype strains.

Conclusion

HPeV3 nonstructural protein genes may form a distinct element in a pool of circulating HPeV non-structural protein genes. More research into the complex HPeV evolution is required to connect virus ecology with disease patterns in humans.

Cannabinoid modulation of Kaposi's sarcoma-associated herpesvirus infection and transformation

Kaposi's sarcoma-associated herpesvirus (KSHV; also named human herpesvirus 8) is necessary but not sufficient for the development of Kaposi's sarcoma. A variety of factors may contribute to the pathogenesis of Kaposi's sarcoma in addition to KSHV. Marijuana is a widely used recreational agent, and Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the major active component of marijuana, is prescribed for medicinal use. To evaluate how cannabinoids may affect the pathogenesis of Kaposi's sarcoma, we studied primary human dermal microvascular endothelial cells (HMVEC) exposed to KSHV. There was an increased efficiency of KSHV infection in the presence of low doses of Delta(9)-THC. We also found that Delta(9)-THC increased the viral load in KSHV-infected HMVEC through activation of the KSHV lytic switch gene, the open reading frame 50. Furthermore, we observed that Delta(9)-THC stimulated expression of the KSHV-encoded viral G protein-coupled receptor and Kaposi's sarcoma cell proliferation. Our results indicate that Delta(9)-THC can enhance KSHV infection and replication and foster KSHV-mediated endothelial transformation. Thus, use of cannabinoids may place individuals at greater risk for the development and progression of Kaposi's sarcoma.

Human herpesvirus 8: serovprevalence and correlates in tumor patients from Xinjiang, China

Human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, is etiologically associated with Kaposi's sarcoma and other lymphoproliferative diseases. Although HHV-8 prevalence exhibits considerable variation in different geographic regions and populations, the incidence of Kaposi's sarcoma appear to increase in areas with a high prevalence rate. In this study, an enzyme-linked immunosorbent assay based on mixed antigens of HHV-8 ORF(73), ORF(65), and K8.1 in the antigenic region was established and used to determine viral prevalence estimates and risk factors associated with HHV-8 infection. Of 482 tumor patients studied, the overall seropositivity of HHV-8 was 25.5%. Notably, Han people, who were immigrants or descendents of immigrants from inland of China, exhibited 26.4% seropositivity. This is similar to that observed in Uygur people, a local ethnic group with a high prevalence of HHV-8 infection and incidence of Kaposi's sarcoma. While there was no significant difference in patients with different tumors, HHV-8 seroprevalence was higher in individuals with malignant diseases. Logistic regression analysis suggests that the age is a risk factor associated with HHV-8 infection, with prevalence increasing from 12.5% under 20-27.5% above 50. These results suggest that unlike other parts of mainland of China, Xinjiang is an area with a high prevalence of HHV-8 infection.

KSHV/HHV-8 and HIV infection in Kaposi's sarcoma development

Kaposi's sarcoma (KS) is a highly and abnormally vascularized tumor-like lesion affecting the skin, lymphnodes and viscera, which develops from early inflammatory stages of patch/plaque to late, nodular tumors composed predominant of spindle cells (SC). These SC are infected with the Kaposi's sarcoma-associated herpesvirus or human herpesvirus-8 (KSHV/HHV-8). KS is promoted during HIV infection by various angiogenic and pro-inflammatory factors including HIV-Tat. The latency associated nuclear antigen type 1 (LANA-1) protein is well expressed in SC, highly immunogenic and considered important in the generation and maintenance of HHV-8 associated malignancies. Various studies favour an endothelial origin of the KS SC, expressing "mixed" lymphatic and vascular endothelial cell markers, possibly representing hybrid phenotypes of endothelial cells (EC). A significant number of SC during KS development are apparently not HHV8 infected, which heterogeneity in viral permissiveness may indicate that non-infected SC may continuously be recruited in to the lesion from progenitor cells and locally triggered to develop permissiveness to HHV8 infection. In the present study various aspects of KS pathogenesis are discussed, focusing on the histopathological as well as cytogenetic and molecular genetic changes in KS.

Molecular biology of KSHV in relation to AIDS-associated oncogenesis

KSHV has been established as the causative agent of KS, PEL, and MCD, malignancies occurring more frequently in AIDS patients. The aggressive nature of KSHV in the context of HIV infection suggests that interactions between the two viruses enhance pathogenesis. KSHV latent infection and lytic reactivation are characterized by distinct gene expression profiles, and both latency and lytic reactivation seem to be required for malignant progression. As a sophisticated oncogenic virus, KSHV has evolved to possess a formidable repertoire of potent mechanisms that enable it to target and manipulate host cell pathways, leading to increased cell proliferation, increased cell survival, dysregulated angiogenesis, evasion of immunity, and malignant progression in the immunocompromised host. Worldwide, approximately 40.3 million people are currently living with HIV infection. Of these, a significant number are coinfected with KSHV. The complex interplay between the two viruses dramatically elevates the risk for development of KSHV-induced malignancies, KS, PEL, and MCD. Although HAART significantly reduces HIV viral load, the entire T-cell repertoire and immune function may not be completely restored. In fact, clinically significant immune deficiency is not necessary for the induction of KSHV-related malignancy. Because of variables such as lack of access to therapy noncompliance with prescribed treatment, failure to respond to treatment and the development of drug-resistant strains of HIV, KSHV-induced malignancies will continue to present as major health concerns.

Structure and function of latency-associated nuclear antigen

Latency-associated nuclear antigen (LANA) encoded by open reading frame 73 (ORF73) is the major latent protein expressed in all forms of KSHV-associated malignancies. LANA is a large (222-234 kDa) nuclear protein that interacts with various cellular as well as viral proteins. LANA has been classified as an oncogenic protein as it dysregulates various cellular pathways including tumor suppressor pathways associated with pRb and p53 and can transform primary rat embryo fibroblasts in cooperation with the cellular oncogene Hras. It associates with GSK-3beta, an important modulator of Wnt signaling pathway leading to the accumulation of cytoplasmic beta-catenin, which upregulates Tcf/Lef regulated genes after entering into the nucleus. LANA also blocks the expression of RTA, the reactivation transcriptional activator, which is critical for the latency to lytic switch, and thus helps in maintaining viral latency. LANA tethers the viral episomal DNA to the host chromosomes by directly binding to its cognate binding sequence within the TR region of the genome through its C terminus and to the nucleosomes through the N terminus of the molecule. Tethering to the host chromosomes helps in efficient partitioning of the viral episomes in the dividing cells. Disruptions of LANA expression led to reduction in the episomal copies of the viral DNA, supporting its role in persistence of the viral DNA. The functions known so far suggest that LANA is a key player in KSHV-mediated pathogenesis.

CGH of microdissected Kaposi's sarcoma lesions reveals recurrent loss of chromosome Y in early and additional chromosomal changes in late tumour stages

BACKGROUND

It is still unclear if Kaposi's sarcoma (KS) is a monoclonal cell proliferation or a polyclonal, hyperplastic, reactive process. Reports on KS cytogenetics are few and restricted to late stage disease and cell lines.

METHOD

We analysed 27 KS, early and late, AIDS related (AKS) and endemic (EKS) by laser microdissection, global DNA amplification and comparative genomic hybridization (CGH).

RESULT

Loss of Y chromosome was detected in 20/23 male KS, which was the only recurrent chromosomal aberration in all nine male early (patch) KS. Only one patch EKS showed in addition to the Y loss a loss of Xq. Late (nodular) AKS and EKS showed recurrent copy number changes in chromosomes 16, 17, 21, X and Y, as well as other random changes. The loss of chromosome 16, 17 and Y was confirmed by interphase fluorescence in situ hybridization (FISH) on paraffin sections. EKS showed a higher number of chromosomal abnormalities than AKS, indicating that rapid growth of AKS is less dependent on genetic changes than is EKS, possibly because of the immunosuppressed host environment in AKS.

CONCLUSION

Clonal loss of chromosome Y was detected in all early male KS, while additional chromosomal aberrations appeared during development to late KS. This increase in chromosomal abnormalities during tumour growth indicates genetic instability and the selection of survival cell clones establishing late, aggressive sarcoma growth. Our data support the view that KS (in males) develops into a clonal tumour yet initially is a hyperplastic reactive cell proliferation.

Genetic organization and hypoxic activation of the Kaposi's sarcoma-associated herpesvirus ORF34-37 gene cluster

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent for Kaposi's sarcoma (KS) and primary effusion lymphoma (PEL). We previously reported that hypoxia activates KSHV lytic replication and that the promoter for open reading frame 34 (ORF34) contains a functional hypoxia-responsive element (HRE). ORF34 is part of a cluster of lytic genes (ORF34-37) that includes ORF36, a phosphotransferase, and ORF37, a shutoff exonuclease. Rapid amplification of cDNA ends analysis revealed that they share a common polyadenylation signal but have two start sites. Two transcripts were identified, one 3.4 kb encoding ORF35-37, and the other 4.2 kb encoding ORF34 and also having coding potential for ORF35-37. Exposure of PEL cell lines to hypoxia induced messages of lengths consistent with those of these transcripts. Reporter assays with Hep3B cells showed activation of both transcripts by hypoxia. The ORF34-37 promoter region has six consensus HREs. Sequential deletion, site-directed mutagenesis experiments, and Northern blot analysis of RNA produced by constructs indicated that the second HRE (HRE-2) plays a critical role in the hypoxic activation of both RNA transcripts. The ORF35-37 transcript was upregulated by cotransfected hypoxia-inducible factor (HIF). Electrophoretic mobility shift assays demonstrated that HRE-2 and ancillary sequences bind and compete for HIF with hypoxic Hep3B nuclear extract. The activation of this gene cluster by hypoxia may have implications for the pathogenesis of PEL and KS. Moreover, the activation of ORF36 by hypoxia might be exploited to develop targeted therapy for PEL, which arises in a hypoxic environment (pleural effusions).

Associations of Classic Kaposi Sarcoma with Common Variants in Genes that Modulate Host Immunity

Classic Kaposi sarcoma (CKS) is an inflammatory-mediated neoplasm primarily caused by Kaposi sarcoma-associated herpesvirus (KSHV). Kaposi sarcoma lesions are characterized, in part, by the presence of proinflammatory cytokines and growth factors thought to regulate KSHV replication and CKS pathogenesis. Using genomic DNA extracted from 133 CKS cases and 172 KSHV-latent nuclear antigen-positive, population-based controls in Italy without HIV infection, we examined the risk of CKS associated with 28 common genetic variants in 14 immune-modulating genes. Haplotypes were estimated for IL1A, IL1B, IL4, IL8, IL8RB, IL10, IL12A, IL13, and TNF. Compared with controls, CKS risk was decreased with 1235T/-1010G-containing diplotypes of IL8RB (odds ratio, 0.49; 95% confidence interval, 0.30-0.78; P = 0.003), whereas risk was increased with diplotypes of IL13 containing the promoter region variant 98A (rs20541, alias +130; odds ratio, 1.88; 95% confidence interval, 1.15-3.08; P = 0.01) when considered in multivariate analysis. Risk estimates did not substantially vary by age, sex, incident disease, or disease burden. Our data provide preliminary evidence for variants in immune-modulating genes that could influence the risk of CKS. Among KSHV-seropositive Italians, CKS risk was associated with diplotypes of IL8RB and IL13, supporting laboratory evidence of immune-mediated pathogenesis.

Establishment and maintenance of Kaposi's sarcoma-associated herpesvirus latency in B cells

Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) is the infectious cause of Kaposi's sarcoma and is also associated with two B-cell lymphoproliferative diseases, primary effusion lymphoma and the plasmablastic form of multicentric Castleman's disease. KSHV is also found in the B-cell fraction of peripheral blood mononucleocytes of some KS patients. Despite in vivo infection of B cells and the ability of KSHV to infect many cell types in culture, to date B cells in culture have been resistant to KSHV infection. However, as shown here, the lack of infection is not due to the inability of B cells to support latent KSHV infection. When KSHV DNA is introduced into B cells, the virus is maintained as an episome and can establish and maintain latency over the course of months. As in all primary effusion lymphoma cell lines, there is a low level of spontaneous lytic replication in latently infected BJAB cells. Importantly, viral gene expression is similar to that of primary effusion lymphoma cell lines. Furthermore, the virus can be reactivated to higher levels with specific stimuli and transmitted to other cells, indicating that this is a productive infection. Thus B cells in culture are capable of establishing, maintaining, and reactivating from latency. These studies provide a controlled system to analyze how KSHV alters B cells during KSHV latency and reactivation.

Lymphatic and vascular origin of Kaposi's sarcoma spindle cells during tumor development

The histogenesis of Kaposi's sarcoma (KS) tumor spindle cells (SC) remains controversial but several immunohistochemical studies favor a lymphatic origin. Twenty KS surgical biopsies were analyzed for the coexpression of LANA, CD34, LYVE-1, D2-40, VEGFR-2, VEGFR3 by using double or triple immunostaining. Most of the SC in both early and late KS expressed the lymphatic markers LYVE-1, D2-40 and VEGFR-3 and the blood vascular endothelial/endothelial precursor cell markers CD34 and endothelial stem cell marker VEGFR-2. All the LANA+ SC in early and late KS were LYVE-1+, but only 75% of these LANA+ cells were CD34(+). The CD34(+)/LANA+ cells increased from early- (68.8%) to late-stage KS (82.2%). However, approximately 18% of the LANA+ SC in early KS were CD34(-) but were LYVE-1+, suggesting that resident lymphatic endothelial cells (LEC) are targeted for primary infection by human herpesvirus-8. This LANA+/LYVE-1+/CD34(-) (resident LEC) cell population clearly decreased during the development of KS from early (18.7%) to late KS (2.9%). Thus, in late stages of KS, most SC were LANA+/CD34(+)/LYVE-1+. However, in both early- and late-stage KS, approximately 18% of the SC were CD34(+)/LANA-/LYVE-1 -- and could represent newly recruited endothelial precursor cells, which become infected in the lesion and eventually undergo a phenotype switch expressing LEC markers. Our study apparently indicates that KS represents a unique variant of tumor growth with continues recruitment of tumor precursor cells as well as proliferation and decreased apoptosis of SC.