Kaposi's-sarcoma-associated herpesvirus in HIV-negative Kaposi's sarcoma

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

The seroprevalence of Kaposi's sarcoma-associated herpesvirus (KSHV) is high in Xinjiang, China. But the seroprevalence of KSHV and risk factors are still unknown in Gansu which is adjacent to Xinjiang. Six hundred and seventy-eight serum samples of the general population and 87 serum samples of syphilis patients from Jiuquan, Gansu were tested for antibodies against KSHV, including one latent protein (ORF73) and two lytic proteins (ORF65 and K8.1) using the ELISA. The total KSHV-seropositive rate was 15.9% in 678 serum samples in the Jiuquan area, and the KSHV-seropositive rate of males was higher than females (18.0% vs. 14.6%, p > 0.05). The Uygur, Kazakh, Hui, Manchu, and Mongolian populations had a higher seroprevalence of KSHV than the Han population (43.8%, 40.0%, 34.5%, 30.3%, 35.0% vs. 11.0%, respectively) among the ethnic groups in Jiuquan. Compared to the Han, Uygur, Kazak, Hui, Manchu, and Mongolian people had an increase in the risk of KSHV of 528.9%, 439.1%, 325.6%, 251.6%, and 335.4% (p < 0.001, p < 0.001, p < 0.001, p = 0.002, p = 0.003, respectively). The serum prevalence of KSHV in subjects aged < 20 years, 20-50 years, and >50 years was 13.8%, 14.7%, and 20.1%, respectively. Compared to the subjects aged < 20 years, 20-50 years and >50 years had an increase in the risk of KSHV of 7.4% and 56.9% (p = 0.829 and p = 0.204, respectively). Compared to the positive rate of KSHV in the general population of Anhui, the positive rate of KSHV was significantly higher in the general population of the Jiuquan area (15.9% vs. 9%, p < 0.01). There was no significant difference in the positive rate of KSHV between the Han population of Jiuquan and the Han population of Anhui (p > 0.05). In the population of syphilis patients in the Jiuquan area, the positive rate of KSHV was 30.7%, which was higher than that of the general population in the Gansu area (p < 0.05). This study indicates that Gansu has a high seroprevalence of KSHV. Ethnicity and syphilis are risk factors for KSHV infection.

Lenalidomide and the expanding toolkit to manage Kaposi sarcoma

Lenalidomide recently was shown to have clinical activity in patients with human immunodeficiency virus-associated Kaposi sarcoma. Immunomodulatory imine drugs thus provide another tool in the treatment of this challenging neoplasm.

Prevalence and Risk Factors of Kaposi’s Sarcoma-Associated Herpesvirus Infection among Han and Uygur Populations in Xinjiang, China

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma (KS), which is endangering human health worldwide, especially in Africa, Europe, the United States, and parts of Asia. The aim of this study was to investigate the prevalence of KSHV in Xinjiang. Three KSHV recombinant proteins (ORF65, ORF73, and K8.1) were used to detect KSHV infection. The serum samples to be tested were detected by an indirect ELISA method. The overall infection rate of KSHV in Xinjiang was 25.60%, with a higher infection rate in the Uygur population of 29.79%. After adjusting for possible confounders, Uygur (OR = 3.95, 95% CI 2.64–6.12, P < 0.001), agriculture and livestock (OR = 1.60, 95% CI 1.20–2.17, P = 0.002), age ≤ 50 years (OR = 1.50, 95% CI 1.13–2.00, P = 0.006), and predominantly meat-based diet (OR = 1.72, 95% CI 1.11–2.78, P = 0.018) were significantly associated with the odds of KSHV seropositivity correlation. Three unique sequences of KSHV were obtained in this study; genotypic analysis showed that the three unique sequences were all subtype A2.

Arachidonic Acid Derived Lipid Mediators Influence Kaposi's Sarcoma-Associated Herpesvirus Infection and Pathogenesis

Kaposi’s sarcoma-associated herpesvirus (KSHV) infection, particularly latent infection is often associated with inflammation. The arachidonic acid pathway, the home of several inflammation and resolution associated lipid mediators, is widely altered upon viral infections. Several in vitro studies show that these lipid mediators help in the progression of viral pathogenesis. This review summarizes the findings related to human herpesvirus KSHV infection and arachidonic acid pathway metabolites. KSHV infection has been shown to promote inflammation by upregulating cyclooxygenase-2 (COX-2), 5 lipoxygenase (5LO), and their respective metabolites prostaglandin E₂ (PGE₂) and leukotriene B4 (LTB₄) to promote latency and an inflammatory microenvironment. Interestingly, the anti-inflammatory lipid mediator lipoxin is downregulated during KSHV infection to facilitate infected cell survival. These studies aid in understanding the role of arachidonic acid pathway metabolites in the progression of viral infection, the host inflammatory response, and pathogenesis. With limited therapeutic options to treat KSHV infection, use of inhibitors to these inflammatory metabolites and their synthetic pathways or supplementing anti-inflammatory lipid mediators could be an effective alternative therapeutic.

Autoimmune bullous diseases in non-HIV Kaposi's sarcoma: a retrospective study in a large cohort of patients

BACKGROUND

Kaposi's sarcoma (KS) is a rare endothelial neoplasm caused by the human herpesvirus 8 (HHV-8). Its risk is increased in immunocompromised patients, including those undergoing immunosuppressive therapy for autoimmune bullous diseases. Conversely, HHV-8 infection has been hypothesized to be a triggering factor of bullous diseases, especially pemphigus. Given the fact that both KS and autoimmune bullous diseases have a low incidence in the general population, it could be expected that the association between these disorders would be exceptional.

OBJECTIVES

To assess the frequency of bullous diseases in a large cohort of non-HIV KS patients and to describe our experience concerning the clinical features, natural history and treatment options in this setting.

METHODS

We performed a retrospective review of all patients with non-HIV KS in association with bullous disease followed at our department between 1990 and 2016. Medical records were reviewed for demographics, medical history, clinical characteristics and treatment.

RESULTS

Among 1362 patients with classic or iatrogenic KS, 14 (1.03%) also suffered from bullous disease. The mean age at diagnosis of both disorders was 85.8 years with a male/female ratio of 9 : 5. Among these 14 cases, nine (0.66%) were associated with bullous pemphigoid (BP), three (0.22%) with localized BP and two (0.15%) with pemphigus vulgaris. Seven had developed a bullous disease after being diagnosed with KS, while in the remaining seven cases, KS developed after the onset of bullous disease. As expected, KS worsened when corticosteroids were used.

CONCLUSION

Bullous diseases seem to be more frequent among patients with KS, supporting the hypothesis that HHV-8 may be involved in their pathogenesis. Therapeutic management of these cases should take into account KS-inducing potential of corticosteroids.

Epidemiology of Classic Kaposi's Sarcoma, with Special Reference to Mediterranean Population

An excess of classic Kaposi's sarcoma (KS) in individuals of southern European ancestry has long been suspected and recently quantified in terms of age-standardized rates. In Italy and most notably in southern Italy for the period 1976-84, prior to the AIDS epidemic, KS incidence rates were two-to-three-fold higher than in the United States and Sweden and many ten-fold higher than in England and Wales and Australia. A high frequency of classic KS has also been documented in Israel and, in low-risk countries, in individuals born in southern Europe and the Middle East. Many infections have been suspected to play a role in the etiology of KS, including cytomegalovirus, malaria and, most recently, a new virus of the herpes family, identified in AIDS-associated and classic KS. The present review deals with epidemiologic data concerning KS in the Mediterranean and stresses the opportunity to combine the study of KS in AIDS as well as non-AIDS patients in order to shed light on this no longer rare disease.

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.

Rapid Multiplexed Immunoassay for Detection of Antibodies to Kaposi's Sarcoma-Associated Herpesvirus

Diagnosis of KSHV-infected individuals remains a challenge. KSHV prevalence is high in several populations with high prevalence of HIV, leading to increased risk of development of Kaposi’s sarcoma (KS). While current assays are reliable for detecting antibodies to KSHV, none are routinely utilized to identify individuals with KSHV infection and thus at increased risk for KS due to assay complexity, lack of access to testing, and cost, particularly in resource-limited settings. Here we describe the addition of KSHV proteins LANA and K8.1 to a previously evaluated HIV/co-infection multiplexed fluorescence immunoassay system. This study demonstrates assay performance by measuring antibody reactivity for KSHV and HIV-1 in a collection of clinical specimens from patients with biopsy-proven KS and sourced negative controls. The KSHV assay correctly identified 155 of 164 plasma samples from patients with biopsy-proven KS and 85 of 93 KSHV antibody (Ab)-negative samples for a sensitivity of 95.1% and specificity of 91.4%. Assay performance for HIV-1 detection was also assessed with 100% agreement with independently verified HIV-1 Ab-positive and Ab-negative samples. These results demonstrate good sensitivity and specificity for detection of antibody to KSHV antigens, and demonstrate the potential for multiplexed co-infection testing in resource-limited settings to identify those at increased risk for HIV-1-related complications.

Beral et al's 1990 paper on Kaposi's sarcoma among persons with AIDS: demonstrating the power of descriptive epidemiology

Here we discuss the impact of Beral et al's 1990 paper "Kaposi's sarcoma among persons with AIDS: a sexually transmitted infection?" Not only did this paper galvanise research into the underlying infectious cause of Kaposi's sarcoma, it also demonstrated the power of observational epidemiology in pointing the way towards major discoveries.

Contribution of viral mimics of cellular genes to KSHV infection and disease

Kaposi’s sarcoma-associated herpesvirus (KSHV, also named Human herpesvirus 8 HHV-8) is the cause of Kaposi sarcoma (KS), the most common malignancy in HIV-infected individuals worldwide, primary effusion lymphoma (PEL) and multicentric Castleman disease (MCD). KSHV is a double-stranded DNA virus that encodes several homologues of cellular proteins. The structural similarity between viral and host proteins explains why some viral homologues function as their host counterparts, but sometimes at unusual anatomical sites and inappropriate times. In other cases, structural modification in the viral proteins can suppress or override the function of the host homologue, contributing to KSHV-related diseases. For example, viral IL-6 (vIL-6) is sufficiently different from human IL-6 to activate gp130 signaling independent of the α subunit. As a consequence, vIL-6 can activate many cell types that are unresponsive to cellular IL-6, contributing to MCD disease manifestations. Here, we discuss the molecular biology of KSHV homologues of cellular products as conduits of virus/host interaction with a focus on identifying new strategies for therapy of KS and other KSHV-related diseases.

Extracavitary primary effusion lymphoma presenting as a cutaneous tumor: a case report and literature review

Primary effusion lymphoma is an unusual form of aggressive B-cell lymphoma universally associated with human herpesvirus 8 (HHV8) that involves mostly human immunodeficiency virus (HIV)-infected patients. Characteristically, it presents as a malignant serous effusion involving body cavities, but without associated tumor mass. Exceptionally, HHV8-positive lymphomas with features identical to primary effusion lymphoma may present as mass lesions in the absence of cavity effusions along the course of the disease, and are regarded as extracavitary or solid variants of the disorder. These rare forms are extremely rare in the skin. We report a case of extracavitary primary effusion lymphoma arising in a HIV-infected male, who presented with two subcutaneous masses involving the skin of the abdominal and inguinal regions as the first manifestation of the process. Kaposi sarcoma was not present in the skin surface or mucous membranes. Extensive studies failed to demonstrate involvement of other organs and the case was considered as an example of extracavitary primary effusion lymphoma originating primarily in the skin. Herein, we review the few reported cases of solid primary effusion lymphoma involving the skin in order to delineate the clinicopathologic, immunohistochemical and molecular characteristics of this rare lymphoma in the skin.

Binding of the Kaposi's sarcoma-associated herpesvirus to the ephrin binding surface of the EphA2 receptor and its inhibition by a small molecule

The ephrin receptor tyrosine kinase A2 (EphA2) is an entry receptor for Kaposi's sarcoma-associated herpesvirus (KSHV) that is engaged by the virus through its gH/gL glycoprotein complex. We describe here that natural ephrin ligands inhibit the gH/gL-EphA2 interaction. The effects of point mutations within EphA2 demonstrated that KSHV gH/gL interacts with EphA2 through a restricted set of the same residues that mediate binding of A-type ephrins. Two previously described inhibitors of the EphA2 interaction with ephrin A5 also inhibited binding of KSHV gH/gL to EphA2. The more potent of the two compounds inhibited KSHV infection of blood vessel and lymphatic endothelial cells in the micromolar concentration range. Our results demonstrate that interaction of KSHV with EphA2 occurs in a fashion similar to that of the natural ephrin ligands. Our data further indicate a new avenue for drug development against KSHV.

IMPORTANCE

Our study reports two important findings. First, we show that KSHV engages its receptor, the receptor tyrosine kinase EphA2, at a site that overlaps the binding site of the natural ephrin ligands. Second, we demonstrate that KSHV infection of target cells can be blocked by a small-molecule inhibitor of the viral glycoprotein-EphA2 interaction. These findings represent a novel avenue for the development of strategies to treat KSHV-associated diseases.

The conundrum of causality in tumor virology: the cases of KSHV and MCV

Controversy has plagued tumor virology since the first tumor viruses were described over 100 years ago. Methods to establish cancer causation, such as Koch's postulates, work poorly or not at all for these viruses. Kaposi's sarcoma herpesvirus (KSHV/HHV8) and Merkel cell polyomavirus (MCV) were both found using nucleic acid identification methods but they represent opposite poles in the patterns for tumor virus epidemiology. KSHV is uncommon and has specific risk factors that contribute to infection and subsequent cancers. MCV and Merkel cell carcinoma (MCC), in contrast, is an example in which mutations to our normal viral flora contribute to cancer. Given the near-ubiquity of human MCV infection, establishing cancer causality relies on molecular evidence that does not fit comfortably within traditional infectious disease epidemiological models. These two viruses reveal some of the challenges and opportunities for inferring viral cancer causation in the age of molecular biology.

Kaposi's sarcoma-associated herpesvirus ORF45 mediates transcriptional activation of the HIV-1 long terminal repeat via RSK2

Robust activation of human immunodeficiency virus type 1 (HIV-1) gene expression occurs upon superinfection with Kaposi's sarcoma-associated herpesvirus (KSHV), a common AIDS-associated pathogen. Though the mechanisms underlying this phenotype remain unknown, several KSHV-encoded factors have been reported to stimulate HIV-1 long terminal repeat (LTR) activity. Here, we systematically evaluated the ability of KSHV tegument proteins to modulate the activation of an integrated HIV-1 LTR and revealed that the most potent individual activator is ORF45. ORF45 directs an increase in RNA polymerase II recruitment to the HIV-1 LTR, leading to enhanced transcriptional output. ORF45 is a robust activator of the p90 ribosomal S6 kinases (RSK), and we found that this activity is necessary but not sufficient to increase transcription from the LTR. Of the three widely expressed RSK isoforms, RSK2 appears to be selectively involved in LTR stimulation by both KSHV ORF45 and HIV-1 Tat. However, constitutively active RSK2 is unable to stimulate the LTR, suggesting that ORF45 may preferentially direct this kinase to a specific set of targets. Collectively, our findings reveal a novel transcriptional activation function for KSHV ORF45 and highlight the importance of RSK2 in shaping the transcriptional environment during infection.

IMPORTANCE

Kaposi's sarcoma-associated herpesvirus (KSHV) is a prominent AIDS-associated pathogen. Previous studies have shown that infection of cells containing human immunodeficiency virus type 1 (HIV-1) with KSHV leads to potent stimulation of HIV-1 gene expression by activating the HIV-1 promoter, termed the long terminal repeat (LTR). Here, we compared the abilities of various KSHV proteins to activate gene expression from the HIV-1 LTR and found that KSHV ORF45 is the most potent activator. ORF45 is known to induce cell signaling through ribosomal S6 kinase (RSK) and enhance protein translation. However, we revealed that the activation of a specific isoform of RSK by ORF45 also leads to increased mRNA synthesis from the LTR by the host RNA polymerase. Collectively, our findings provide new insight into the interviral interactions between KSHV and HIV that may ultimately impact disease.

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.

YGLF motif in the Kaposi sarcoma herpes virus G-protein-coupled receptor adjusts NF-κB activation and paracrine actions

Kaposi sarcoma (KS) and primary effusion lymphoma (PEL) are two pathologies associated with KS herpes virus (KSHV/HHV-8) infection. KSHV genome contains several oncogenes, among which, the viral G-protein-coupled receptor (vGPCR open reading frame 74) has emerged as a major factor in KS pathogenicity. Indeed, vGPCR is a constitutively active receptor, whose expression is sufficient to drive cell transformation in vitro and tumour development in mice. However, neither the role of vGPCR in KSHV-infected B-lymphocytes nor the molecular basis for its constitutive activation is well understood. Here, we show that vGPCR expression contributes to nuclear factor-κB (NF-κB)-dependent cellular survival in both PEL cells and primary B cells from HIV-negative KS patients. We further identified within vGPCR an AP2 consensus binding motif, Y326GLF, that directs its localization between the plasma membrane and clathrin-coated vesicles. The introduction of a mutation in this site (Y326A) increased NF-κB activity and proinflammatory cytokines production. This correlated with exacerbated morphological rearrangement, migration and proliferation of non-infected monocytes. Collectively, our work raises the possibility that KSHV-infected B-lymphocytes use vGPCR to impact ultimately the immune response and communication within the tumour microenvironment in KSHV-associated pathologies.

Castleman disease

Castleman and Towne described a disease presenting as a mediastinal mass resembling thymoma. It is also known as "giant lymph node hyperplasia", "lymph node hamartoma", "angiofollicular mediastinal lymph node hyperplasia", and "angiomatous lymphoid hyperplasia". The pathogenesis is unknown, but the bulk of evidence points toward faulty immune regulation, resulting in excessive B-lymphocyte and plasma-cell proliferation in lymphatic tissue. In addition to the mediastinal presentation, extrathoracic involvement in the neck, axilla, mesentery, pelvis, pancreas, adrenal gland, and retroperitoneum also have been described. There are 2 major pathologic variations of Castleman disease: (1) hyaline-vascular variant, the most frequent, characterized by small hyaline-vascular follicles and capillary proliferation; and (2) the plasma-cell variant, in which large lymphoid follicles are separated by sheets of plasma cells. The hyaline-vascular cases usually are largely asymptomatic, whereas the less common plasma-cell variant may present with fever, anemia, weight loss, and night sweats, along with polyclonal hypergamma-globulinemia. Castleman disease is a rare lymphoproliferative disorders. Few cases have been described world widely. In this article we reviewed the classification, pathogenesis, pathology, radiological features and up to date treatment with special emphasis on the role of viral stimulation, recent therapeutic modalities and the HIV-associated disease.

The latency-associated nuclear antigen, a multifunctional protein central to Kaposi's sarcoma-associated herpesvirus latency

Latency-associated nuclear antigen (LANA) is encoded by the Kaposi's sarcoma (KS)-associated herpesvirus (KSHV) open reading frame 73. LANA is expressed during latent KSHV infection of cells, including tumor cells, such as primary effusion lymphoma, KS and multicentric Castleman's disease. Latently infected cells have multiple extrachromosomal copies of covalently closed circular KSHV genomes (episomes) that are stably maintained in proliferating cells. LANA's best characterized function is that of mediating episome persistence. It does so by binding terminal repeat sequences to the chromosomal matrix, thus ensuring episome replication with each cell division and efficient DNA segregation to daughter nuclei after mitosis. To achieve these functions, LANA associates with different host cell proteins, including chromatin-associated proteins and proteins involved in DNA replication. In addition to episome maintenance, LANA has transcriptional regulatory effects and affects cell growth. LANA exerts these functions through interactions with different cell proteins.

The RBP-Jκ binding sites within the RTA promoter regulate KSHV latent infection and cell proliferation

Kaposi's sarcoma-associated herpesvirus (KSHV) is tightly linked to at least two lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). However, the development of KSHV-mediated lymphoproliferative disease is not fully understood. Here, we generated two recombinant KSHV viruses deleted for the first RBP-Jκ binding site (RTA_1st) and all three RBP-Jκ binding sites (RTA_all) within the RTA promoter. Our results showed that RTA_1st and RTA_all recombinant viruses possess increased viral latency and a decreased capability for lytic replication in HEK 293 cells, enhancing colony formation and proliferation of infected cells. Furthermore, recombinant RTA_1st and RTA_all viruses showed greater infectivity in human peripheral blood mononuclear cells (PBMCs) relative to wt KSHV. Interestingly, KSHV BAC36 wt, RTA_1st and RTA_all recombinant viruses infected both T and B cells and all three viruses efficiently infected T and B cells in a time-dependent manner early after infection. Also, the capability of both RTA_1st and RTA_all recombinant viruses to infect CD19+ B cells was significantly enhanced. Surprisingly, RTA_1st and RTA_all recombinant viruses showed greater infectivity for CD3+ T cells up to 7 days. Furthermore, studies in Telomerase-immortalized human umbilical vein endothelial (TIVE) cells infected with KSHV corroborated our data that RTA_1st and RTA_all recombinant viruses have enhanced ability to persist in latently infected cells with increased proliferation. These recombinant viruses now provide a model to explore early stages of primary infection in human PBMCs and development of KSHV-associated lymphoproliferative diseases.

Kaposi's sarcoma-associated herpesvirus (KSHV) is tightly linked to at least two lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). The life cycle of KSHV consists of latent and lytic phase. RTA is the master switch for viral lytic replication. In this study, we first show that recombinant viruses deleted for the RBP-Jκ sites within the RTA promoter have a decreased capability for lytic replication, and thus enhanced colony formation and proliferation of infected cells. Interestingly, the recombinant viruses show greater infectivity in human peripheral blood mononuclear cells (PBMCs). The recombinant viruses also infected CD19+ B cells and CD3+ T cells with increased efficiency in a time-dependent manner and now provide a model which can be used to explore the early stages of primary infection in human PBMCs, as well as the development of KSHV-associated lymphoproliferative diseases.

Update on KSHV epidemiology, Kaposi Sarcoma pathogenesis, and treatment of Kaposi Sarcoma

Much has been learned since the discovery of KSHV in 1994 about its epidemiology and pathology but much of what has been learned has yet to be translated into clinical practice. In this review, we survey the current state of knowledge on KSHV epidemiology and KS pathogenesis and highlight therapeutic opportunities in both the developed and developing world.

Infection of primary human tonsillar lymphoid cells by KSHV reveals frequent but abortive infection of T cells

The lymphotropic herpesvirus KSHV principally infects B cells in vivo and is linked to several human B cell lymphoproliferative syndromes. Here we examine the susceptibility of primary tonsillar lymphocytes to infection by a recombinant KSHV (rKSHV.219) that constitutively expresses GFP. At an MOI of ~1, ca. 5-10% of CD19+ B cells became GFP-positive. Surprisingly, in the same culture many more T cells became infected. However, in contrast to isolated B cells, isolated infected T cells did not support correct viral transcription and did not produce infectious virus, indicating the presence of one or more post-entry blocks to lytic KSHV replication in T cells. No immortalization or transformation has yet been observed in either B or T cells. These results affirm the feasibility of studying KSHV infection in primary lymphoid cells, and help to rationalize the detection of KSHV DNA in rare human T cell lymphomas in vivo.

KSHV and the pathogenesis of Kaposi sarcoma: listening to human biology and medicine

The linkage of Kaposi sarcoma (KS) to infection by a novel human herpesvirus (Kaposi sarcoma-associated herpesvirus [KSHV]) is one of the great successes of contemporary biomedical research and was achieved by using advanced genomic technologies in a manner informed by a nuanced understanding of epidemiology and clinical investigation. Ongoing efforts to understand the molecular mechanisms by which KSHV infection predisposes to KS continue to be powerfully influenced by insights emanating from the clinic. Here, recent developments in KS pathogenesis are reviewed, with particular emphasis on clinical, pathologic, and molecular observations that highlight the many differences between this process and tumorigenesis by other oncogenic viruses.

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.

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.

The viral interferon-regulatory factor-3 is required for the survival of KSHV-infected primary effusion lymphoma cells

Human herpesvirus-8 (HHV-8), also known as Kaposi sarcoma–associated herpesvirus (KSHV), is etiologically linked to primary effusion lymphoma (PEL). At least 10 KSHV-encoded proteins with potential roles in KSHV-associated neoplasia have been identified. However, with few exceptions, these putative oncogenes were analyzed in heterologous systems only using overexpression of single genes. Thus, the pathogenetic relevance of most of these putative oncogenes remains essentially unclear. We used RNA interference (RNAi) to knock down the expression of several KSHV genes in cultured PEL cells carrying the KSHV genome. The viral interferon-regulatory factor-3 (vIRF-3) was found to be required for proliferation and survival of cultured PEL cells. Knock-down of vIRF-3 expression by various RNAi approaches unequivocally resulted in reduced proliferation and increased activity of caspase-3 and/or caspase-7. Thus, vIRF-3 can be seen as a bona fide oncogene of KSHV-associated lymphoma. Surprisingly, although the related Epstein-Barr virus (EBV) is usually sufficient to immortalize human B lymphocytes, silencing of vIRF-3 reduced the viability of both EBV− and EBV+ PEL cells. This suggests that KSHV is the driving force in the pathogenesis of PEL.

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.

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.

Kaposi's sarcoma-associated herpesvirus-encoded latency-associated nuclear antigen modulates K1 expression through its cis-acting elements within the terminal repeats

K1 is the first open reading frame encoded by Kaposi's sarcoma-associated herpesvirus (KSHV) and lies positionally to the immediate right of the terminal repeats. K1 is a transmembrane glycoprotein having a functional immunoreceptor tyrosine-based activation motif (ITAM) capable of activating B-cell receptor signaling. K1 is expressed mostly during the lytic cycle of the virus and its promoter lies within the terminal repeat which contains the binding sites for latency-associated nuclear antigen (LANA). The K1 promoter (K1p) having LANA binding sites assayed by reporter assay demonstrated that LANA is capable of down-regulating K1 promoter transcriptional activity. However, the KSHV replication transcription activator RTA up-regulates K1p transcriptional activity. The promoter deleted of LANA binding sites showed loss in LANA-mediated down-regulation but was unaffected for RTA-mediated up-regulation. Increasing amounts of RTA rescued LANA-mediated repression of K1p transcriptional activity in cotransfection experiments. Reporter assay data suggest that LANA binding to its cognate sequence is critical for LANA-mediated repression of K1p as a LANA construct lacking the DNA binding domain was unable to repress K1p transcription. Additionally, KSHV primary infection experiments suggest that K1 is expressed during early infection but is repressed on the establishment of latency and so follows an expression profile similar to that of RTA during infection. Analysis of the promoter sequence revealed the presence of Oct-1 transcription factor binding sites within the -116 to +76 region. Mutational analysis of the Oct-1 sites abolished RTA-mediated transcriptional activation, suggesting that RTA up-regulates K1p transcription through binding to this transcription factor.

Chemical library screen for novel inhibitors of Kaposi's sarcoma-associated herpesvirus processive DNA synthesis

Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma and certain lymphoproliferative disorders. The role of KSHV lytic replication has been implicated in the tumor pathogenesis. A highly specific molecular complex formed by the KSHV DNA polymerase (POL8) and processivity factor (PF8) is indispensable for lytic viral DNA synthesis and may serve as an excellent molecular anti-KSHV target. The majority of conventional nucleoside-based anti-herpetic DNA synthesis inhibitors require intracellular phosphorylation/activation before they can exert inhibitory activity as competitive substrates for viral DNA polymerases. Novel and more potent inhibitors of KSHV DNA synthesis may be discovered through POL8/PF8-targeted high throughput screening (HTS) of small molecule chemical libraries. We developed a microplate-based KSHV POL8/PF8-mediated DNA synthesis inhibition assay suitable for HTS and screened the NCI Diversity Set that comprised 1992 synthetic compounds. Twenty-eight compounds exhibited greater than 50% inhibition. The inhibitory activity was confirmed for 25 of the 26 hit compounds available for further testing, with the 50% inhibitory concentrations ranging from 0.12+/-0.07 microM (mean+/-S.D.) to 10.83+/-4.19 microM. Eighteen of the confirmed active compounds efficiently blocked KSHV processive DNA synthesis in vitro. One of the hit compounds, NSC 373989, a pyrimidoquinoline analog, was shown to dose-dependently reduce the levels of KSHV virion production and KSHV DNA in lytically induced KSHV-infected BCBL-1 cells, suggesting that the compound blocked lytic KSHV DNA synthesis. HTS for KSHV POL8/PF8 inhibitors is feasible and may lead to discovery of novel non-nucleoside KSHV DNA synthesis inhibitors.

Absence of Kaposi's sarcoma-associated herpesvirus in patients with pulmonary arterial hypertension

RATIONALE

In addition to Kaposi's sarcoma, Kaposi's sarcoma-associated herpesvirus (KSHV or HHV-8) has been associated with two other diseases: primary effusion lymphoma and the plasma cell variant of multicentric Castleman's disease. Recently, evidence of KSHV infection was reported in plexiform lesions of idiopathic pulmonary arterial hypertension (IPAH) as well as in adjacent parenchyma and bronchial epithelial cells.

OBJECTIVES

To further investigate a possible association of KSHV and pulmonary arterial hypertension.

METHODS AND MEASUREMENTS

Twenty-six lungs explanted from German patients suffering from IPAH were tested for the presence of KSHV antigen and genomes by immunohistochemistry (IHC) and polymerase chain reaction (PCR).

MAIN RESULTS

When stained with a commercial monoclonal antibody directed against the latency-associated nuclear antigen of KSHV, LANA-1, a positive signal reminiscent of the "speckled" nuclear pattern typical of latently KSHV-infected cells was found in 16 (61.5%) cases. Alveolar and bronchial epithelial cells in areas of unremarkable lung tissue, but not cells within the plexiform lesions, were the predominantly stained cell types. Different KSHV-PCR assays (based on orf26, orfK6, and orf72) performed on samples that had tested positively in IHC, however, could not confirm KSHV infection, indicating that the IHC signal was not due to KSHV infection. One IHC-negative patient tested positive by PCR. A PCR based on consensus degenerate hybrid oligonucleotide primers (CODEHOP) to detect yet unknown gamma-herpesviruses did not reveal any specific sequences.

CONCLUSIONS

KSHV is unlikely to play a role in the pathogenesis of IPAH.

Epidemiological and clinical characteristics of classic Kaposi's sarcoma in Peru

BACKGROUND

Classic Kaposi sarcoma (KS) occurs predominantly among the elderly, with predominance among Jews, Italians, and Greeks. Classic KS has been seen relatively frequently in Peru.

OBJECTIVE

Our purpose was to outline the epidemiological and clinical profile of classic KS in Peru.

METHODS

Epidemiological and clinical features of all classic KS cases diagnosed between 1969 and 2003 at Hospital Nacional Cayetano Heredia (HNCH) and between 1946 and 2004 at Instituto Nacional de Enfermedades Neoplasicas (INEN) were reviewed and studied retrospectively.

RESULTS

An overall incidence of 2.54 per 10,000 attended patients was obtained at the INEN during the 48-year period (mean, 2.39; standard deviation: 1.99; 95% confidence interval, 2.92-1.86). Twenty-one cases were discovered at HNCH and 106 cases at INEN. A male/female ratio of 2.62:1 was found. Mean age at diagnosis was 68.5 years. Lower limbs were involved in 109 patients (85.8%); the trunk was involved in 11 patients (8.6%). Nodules were the most common type of lesion (85.8%); less commonly found were plaques (27.5%), macules (12.5%), papules (12.5%), and ulcers (8.6%). Sixty-two patients had no symptoms (48.8%). Pain was the most common symptom (26.7%), followed by edema (21.2%), bleeding (14.9%), and pruritus (3.9%). A second primary malignancy was found in 11 patients (8.6%).

LIMITATIONS

These results were obtained from patients with classic KS in Peru and may not be applicable to other populations.

CONCLUSION

Classic KS is quite common in Peru with sporadic cases found throughout the country and some clustering in the coastal region. Classic KS in Peru has a clinical presentation that is very similar, but not identical, to the classic KS described in the Mediterranean region, exhibiting some special clinical and epidemiological characteristics with a nodular, nonsymmetric presentation that usually affects the lower extremities.

Molecular epidemiology of Kaposi's sarcoma herpesvirus (KSHV) in Cuban and German patients with Kaposi's sarcoma (KS) and asymptomatic sexual contacts

Kaposi's sarcoma (KS) shows a distinct geographical and ethnic distribution. The variable K1 gene serves to differentiate the KSHV subtypes A-E, M, N, and Q. Phylogenetic characterization of 19 classical and epidemic German KS specimens revealed the Eurasian KSHV subtypes C (n = 13, including 6 classical KS) and A (n = 6), while 27 Cuban specimens showed a variety of different subtypes (A: n = 16, 4 being A5; C: n = 8; B: n = 2; and the new subtype E: n = 1). Three pairs of isolates from KS patients and peripheral blood mononuclear cells (PBMC) of their sexual partners without KS were studied for the first time and found identical, strongly arguing for sexual transmission of KSHV in this unique cohort. The unique ethnic background of the Cuban population may explain the variety of different KSHV strains.

Reversal of some viral IL-6 electrostatic properties compared to IL-6 contributes to a loss of alpha receptor component recruitment

Human interleukin-6 (hIL-6) is a pleiotropic mediator of activation and proliferation across a large number of different cell types. Human herpesvirus-8 (HHV-8) has been associated with classical and AIDS-related Kaposi's sarcoma (KS). HHV-8 encodes viral IL-6 (vIL-6), a functional homolog of human interleukin-6, that promotes the growth of KS and of some lymphoma cells. Signaling induced by human IL-6 requires recruitment of the glycoprotein gp130, which acts as the signal transducing chain, and of IL-6Ralpha, which is necessary for cognate recognition and high affinity receptor complex formation. In contrast, the formation of a functional complex between vIL-6 and gp130 does not require the presence of IL-6Ralpha. The physico-chemical properties of vIL-6 have been analyzed and compared to those of hIL-6 and of the receptor chains, gp130 and IL-6Ralpha. Interaction sites on vIL-6 involve more hydrophobic residues than those of hIL-6. The electrostatic fields induced by vIL-6 and IL-6Ralpha are repulsive and prevent interaction between vIL-6 and IL-6Ralpha, whereas the electrostatic field induced by hIL-6 steers the complex formation with IL-6Ralpha. Subsequently, electrostatic binding free energy in the vIL-6/IL-6Ralpha complex is destabilizing, whereas it is stabilizing in the complex comprising hIL-6. These properties result from charge reversals between viral and human IL-6, an unusual phenomenon of amino acid substitutions within a homologous protein family. This suggests a selection pressure for vIL-6 to by-pass the IL-6Ralpha control of host defense against virus infection. This selection pressure has yielded the reversal of electrostatic properties of vIL-6 when compared to hIL-6.

Human herpesvirus 6 activates lytic cycle replication of Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 (HHV-8) is a gamma-herpesvirus consistently identified in Kaposi's sarcoma (KS), primary effusion lymphoma, and multicentric Castleman's disease. KSHV infection appears to be necessary, but not be sufficient for development of KS without other co-factors. However, factors that facilitate KSHV to cause KS have not been well defined. Because patients with KS are often immunosuppressed and susceptible to many infectious agents including human herpesvirus 6 (HHV-6), we investigated the potential of HHV-6 to influence the replication of KSHV. By co-culturing HHV-6-infected T cells with KSHV-latent BCBL-1 cell line, infecting BCBL-1 cells with HHV-6 virions, and generating heterokaryons between HHV-6-infected T cells and BCBL-1 cells, we showed that HHV-6 played a critical role in induction of KSHV replication, as determined by production of lytic phase mRNA transcripts and viral proteins. We confirmed and extended the results by using a luciferase reporter assay in which KSHV ORF50 promoter, the first promoter activated during KSHV replication, drove the luciferase expression. Besides HHV-6, we also found that cytokines such as interferon-gamma partially contributed to induction of KSHV replication in the co-culture system. These findings suggest that HHV-6 may participate in KS pathogenesis by promoting KSHV replication and increasing KSHV viral load.

KSHV-Positive Solid Lymphomas Represent an Extra-Cavitary Variant of Primary Effusion Lymphoma

Primary effusion lymphoma (PEL) is a unique form of non-Hodgkin lymphoma (NHL) associated with Kaposi sarcoma-associated herpesvirus (KSHV; HHV-8) that displays a distinct constellation of clinical, morphologic, immunologic, and molecular characteristics. Rare KSHV-containing immunoblastic lymphomas occurring in solid tissues have been described. Whether they represent part of the spectrum of PEL has not been determined. The morphologic, immunophenotypic, and molecular features of KSHV-positive solid lymphomas occurring in 8 HIV+/AIDS patients were systematically investigated and compared with those of 29 similarly analyzed PELs. The 8 KSHV-positive solid lymphomas were virtually indistinguishable from the 29 PELs based on morphology (immunoblastic/anaplastic), immunophenotype (CD45 positive; T cell antigen negative; CD30, EMA, CD138 positive; CD10, CD15, BCL6 negative) and genotype (100% immunoglobulin genes rearranged; no identifiable abnormalities in C-MYC, BCL6, BCL1, BCL2; and uniformly EBV positive). The only identifiable phenotypic difference was that the KSHV-positive solid lymphomas appeared to express B cell-associated antigens (25%) and immunoglobulin (25%) slightly more often than the PELs (<5% and 15%, respectively; P = 0.11 and P = 0.08, respectively). The clinical presentation and course of the patients who develop KSHV-positive solid lymphomas were also similar, except for the lack of an effusion and somewhat better survival (median 11 months vs. 3 months). However, the 3 KSHV-positive solid lymphoma patients alive without disease 11, 25, and 44 months following initial presentation were recently diagnosed patients and, unlike the other patients with KSHV-positive solid lymphomas, received anti-retroviral therapy. These findings strongly suggest that these decidedly rare KSHV-positive solid lymphomas belong to the spectrum of PEL. Therefore, we propose that the KSHV-positive solid lymphomas be designated extra-cavitary PELs.

Staurosporine-induced G2/M arrest in primary effusion lymphoma BCBL-1 cells

Staurosporine, an inhibitor of protein kinase C, is a potential antitumor drug and its derivatives are used as anticancer drugs in clinical trials. Human herpesvirus 8 (HHV-8) is implicated in all forms of Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman's disease (MCD), indicating it to be a DNA tumor virus. It is difficult to culture cell lines derived from KS patients; we therefore used a cell line derived from PEL (BCBL-1) to investigate whether staurosporine affects the HHV-8-related tumors. Our results show that staurosporine treatment reduces the cell viability of BCBL-1 cells and causes cell cycle arrest in the G2/M phase. The G2/M arrest was associated with the decrease in the expression of Cdc2 and cyclin B. Furthermore, the induction of the HHV-8 lytic cycle was not observed under the staurosporine treatment.

Human herpesvirus 8 seroconversion in Kenyan women by enzyme-linked immunosorbent assay and immunofluorescence assay

BACKGROUND

Human herpesvirus 8 (HHV-8) antibody tests vary in reported sensitivity and specificity, depending on the population tested and the assay.

OBJECTIVE

The purpose of this study was to compare the ability to detect seroconversion to HHV-8 in a cohort of HHV-8 seronegative female commercial sex workers in Kenya using three tests: HHV-8 viral lysate-based enzyme-linked immunosorbent assay (ELISA), an immunofluorescence assay for HHV-8 lytic antigens (IFA-lytic) and IFA for latent nuclear antigens (IFA-LANA).

STUDY DESIGN

By ELISA, 16 women from a prospective cohort of commercial sex workers were identified as seroconverting to HHV-8. A total of 124 post-enrollment samples from these 16 women as well as the enrollment samples were tested for HHV-8 antibodies by all three assays to monitor seroconversion.

RESULTS

Of 16 women with apparent seroconversion by ELISA, 8 had a rise in IFA-lytic titers either concomitant with or prior to the first positive ELISA sample and no initial LANA by IFA. Five of the 16 women were IFA-LANA positive at entry, indicating prior infection with HHV-8. Three women had no evidence of seroconversion by either IFA-lytic or IFA-LANA and two of these three had increased ELISA reactivity concomitant with HIV-1 infection.

CONCLUSIONS

Conversion from a negative to a positive ELISA result for HHV-8 antibody indicated seroconversion in only half of the study cohort of 16 women when IFA-lytic and IFA-LANA results were considered. The IFA-lytic assay was more sensitive than ELISA for early antibody responses. The IFA-LANA was positive in some women who had neither IFA-lytic nor ELISA antibodies suggesting it may be a marker for latent infections. Presumptive identification of incident HHV-8 infection by ELISA screening followed by IFA-lytic testing to confirm the positive test and IFA-LANA to rule out prior infection provides the most accurate documentation of HHV-8 seroconversion.

The role of Kaposi's sarcoma-associated herpesvirus/human herpesvirus-8 regulator of transcription activation (RTA) in control of gene expression

The mechanisms that control the replication state, latency versus lytic, of human herpesviruses have been under intense investigations. Here we summarize some of the recent findings that help define such mechanisms for Kaposi's sarcoma-associated herpesvirus/human herpesvirus type 8 (KSHV/HHV-8). For HHV-8, the viral regulator of transcription activation (RTA) is a key mediator of the switch from latency to lytic gene expression in infected cells. RTA is necessary and sufficient to drive HHV-8 lytic replication and the production of viral progeny. The RTA is an immediate-early gene product, it is the initial activator of expression of a multitude of viral and cellular genes that have been implicated in the replication of HHV-8 and pathogenesis of KS. Interactions of RTA with a number of viral promoters, and with a number of transcription factors or transcriptional co-activators are highlighted. Modulation of transactivation, through alternate RTA-protein, or RTA-promoter interactions, is hypothesized to participate in the selective tissue tropism and differential pathogenesis observed in KS.

Factors associated with human herpesvirus type 8 infection in an injecting drug user cohort

BACKGROUND

Human herpesvirus type 8 (HHV-8) has been infrequently studied in injecting drug user (IDU) populations.

GOAL

To estimate the seroprevalence of HHV-8 and risk factors for infection in a cohort of 2,946 IDUs.

STUDY DESIGN

In this nested cross-sectional study of 390 IDUs, lytic HHV-8 indirect immunofluorescence assay (IFA) was utilized to estimate the HHV-8 seroprevalence. Multivariate logistic regression was used to assess risk factors for infection.

RESULTS

The HHV-8 seroprevalence among the IDUs examined in 1988 was 11.5% (95% confidence interval, 8.5-15.13). HHV-8 seroprevalence in this population was associated with being female (OR = 2.2; = 0.080), having a larger body mass index (OR = 3.0; = 0.053), and history of genital warts (OR = 4.0; = 0.023). Injection of any drug more than daily exhibited an inverse effect on HHV-8 seropositivity (OR = 0.5; = 0.085).

CONCLUSION

The seroprevalence of HHV-8 in this population is similar to that seen in the general population, with risk factors being more consistent with sexual behaviors than injection drug use.

Human herpesvirus 8 (HHV-8) and the etiopathogenesis of Kaposi's sarcoma

OBJECTIVE

To review the current literature on human herpesvirus 8 with particular attention to the aspects related to the etiopathogenesis of Kaposi's sarcoma.

MATERIALS AND METHODS

The authors searched original research and review articles on specific aspects of human herpesvirus 8 infection, including virology, epidemiology, transmission, diagnosis, natural history, therapy, and Kaposi's sarcoma etiopathogenesis. The relevant material was evaluated and reviewed.

RESULTS

Human herpesvirus 8 is a recently discovered DNA virus that is present throughout the world but with major geographic variation. In the Western world, the virus, transmitted mainly by means of sexual contact, is strongly associated with Kaposi's sarcoma and body cavity-based lymphoma and more controversially with multiple myeloma and other non-proliferative disorders. There is no specific effective treatment, but HIV protease inhibitors may play an indirect role in the clearance of human herpesvirus 8 DNA from peripheral blood mononuclear cells of HIV-infected patients. Human herpesvirus 8 DNA is present in saliva, but there are as yet no documented cases of nosocomial transmission to health care workers. The prevalence of human herpesvirus 8 among health care workers is probably similar to that in the general population.

CONCLUSION

Human herpesvirus 8 appears to be, at least in Western Europe and United States, restricted to a population at risk of developing Kaposi's sarcoma. Human herpesvirus 8 certainly has the means to overcome cellular control and immune responses and thus predispose carriers to malignancy, particularly Kaposi's sarcoma. The wide diffusion of Human herpesvirus 8 in classic Kaposi's sarcoma areas appears to represent an important factor in the high incidence of the disease. However, additional co-factors are likely to play a role in the development of Kaposi's sarcoma.

Detection and quantitation of Kaposi's sarcoma-associated herpesvirus (KSHV) by a single competitive-quantitative polymerase chain reaction

Kaposi's sarcoma-associated herpesvirus is a novel herpesvirus linked to AIDS-related neoplasms. Currently it is difficult to evaluate the number of virions in viral preparation or in samples obtained from patients with Kaposi's sarcoma (KS), since no protocol for determining the plaque forming units of KSHV exists. We constructed a fragment of a different size than the target viral DNA to carry out a competitive-quantitative PCR. Both fragment and viral DNA were added to a single PCR reaction to compete for the same set of primers. By knowing the amount of the competitor added to the reaction, we could determine the number of viral DNA molecules. We used this assay successfully to detect and quantify KSHV genomes from KS skin biopsies and pleural effusion lymphoma, and from different viral preparations. To date, this is the most convenient and economic method that allows an accurate and fast viral detection/quantitation with a single PCR.

Auto-activation of the transforming viral interferon regulatory factor encoded by Kaposi's sarcoma-associated herpesvirus (human herpesvirus-8)

Kaposi's sarcoma-associated herpesvirus (KSHV)/human herpesvirus-8-encoded viral interferon regulatory factor (vIRF) transforms NIH3T3 cells, represses interferon signal transduction and regulates the expression of other KSHV genes. Here, we have shown that vIRF is a transcriptional activator and auto-activates its own expression. Ectopic expression of vIRF activated the vIRF promoter in KSHV-negative 293, COS7, HeLa and BJAB cell lines in a dose-dependent fashion in a reporter assay and the expression of vIRF transcripts from endogenous viral genomes in BCBL-1 and BC-1 cells latently infected with KSHV. Deletion analysis identified two cis elements, named Vac1 and Vac2, in the vIRF promoter that were responsive to vIRF activation. vIRF auto-activation via Vac1 but not Vac2 was repressed by Tis, a transcriptional silencer in the vIRF promoter. Neither Vac1 nor Vac2 contain any interferon-stimulated response element (ISRE)-like sequences and are unresponsive to induction with interferon-beta and -gamma. These results indicate that KSHV uses the mechanism of auto-activation to regulate the expression of a viral transforming protein to efficiently evade host tumour suppressor pathways.

Laboratory diagnosis of human herpesvirus 8 infection in humans

Human herpesvirus 8 (HHV-8) is causally associated with Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease. Serological and molecular biology assays are used to investigate the biology of this virus in different populations and diseases. Serological assays are mainly used to study the prevalence of the viral infection and to predict the diagnosis of Kaposi's sarcoma and other HHV-8-associated cancers. The appearance of antibodies against lytic antigens precedes the appearance of antibodies against latent antigens, probably explaining the lower sensitivity of assays based on latent HHV-8 antigens. The lack of international reference serum panels is presently the major bottleneck for further progress in the field of HHV-8 serology. Molecular biological assays are an absolute requirement for both the diagnosis and the follow-up of HHV-8 infection. Qualitative methods have been particularly useful to elucidate the mode of transmission and the causal association between HHV-8 and HHV-8-associated diseases. Quantitative methods have become an essential tool to monitor the progression of the infection and the effects of antiviral therapies. This review analyzes the performance of the different serological and molecular biological assays available at present. The main conclusion is that more research is needed to define the most useful laboratory tests for the diagnosis of HHV-8 infection and to establish the clinical role of such tests.