Transmissible Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) in saliva of men with a history of Kaposi's sarcoma

Associations between salivary microbiota and Kaposi's sarcoma-associated herpesvirus infection in people with HIV

OBJECTIVE

Kaposi's sarcoma-associated herpesvirus (KSHV) infection, essential for Kaposi sarcoma development especially in people with HIV (PWH), has been proposed to be transmitted through saliva. The potential role of salivary microbiota played in the infection of KSHV is largely obscure. This study aimed to explore the association between salivary microbiota and KSHV infection among PWH.

DESIGN

Cross-sectional study.

METHODS

During May to December 2022, we conducted a cross-sectional study among PWH in Ili prefecture Xinjiang, China. Participants completed face-to-face questionnaires, plasma and saliva samples were collected to assay KSHV infection status and 16S rRNA sequencing. We distinguished demographic characteristics between groups with and without KSHV, and compared the α and β diversity of the salivary microbiota. LEfSe identified key bacterial genera for Random Forest and XGBoost models to recognize the important discriminatory features.

RESULTS

Among 876 PWH in Xinjiang, 38.7% were KSHV seropositive. Regression models indicated that moderate drinking, absence of dental treatment history, higher CD4 counts, and higher CD4/CD8 ratios were negatively associated with KSHV seropositivity. Linear discriminant analysis effect size (LEfSe) analysis demonstrated that 14 bacterial genera were significantly enriched at the genus level in the group with or without KSHV. Machine learning analyses gave an AUC of 0.66 for Random Forest and 0.85 for XGBoost in predicting KSHV infection status. The bacterial genera, including Alloprevotella , Fusobacterium , Prevotella_7 , Porphyromonas , Rothia , and Leptotrichia , were identified as important discriminatory features.

CONCLUSION

This study suggests the potential role of salivary microbiota in KSHV transmission among PWH. Identified microbial genera offer promising biomarkers for monitoring and managing KSHV in PWH.

Analysis of Metabolomic Reprogramming Induced by Infection with Kaposi's Sarcoma-Associated Herpesvirus Using Untargeted Metabolomic Profiling

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic double-stranded DNA virus. There are no vaccines or antiviral therapies for KSHV. Identifying the cellular metabolic pathways that KSHV manipulates can broaden the knowledge of how these pathways contribute to sustaining lytic infection, which can be targeted in future therapies to prevent viral spread. In this study, we performed an untargeted metabolomic analysis of KSHV infected telomerase-immortalized gingival keratinocytes (TIGK) cells at 4 h post-infection compared to mock-infected cells. We found that the metabolomic landscape of KSHV-infected TIGK differed from that of the mock. Specifically, a total of 804 differential metabolic features were detected in the two groups, with 741 metabolites that were significantly upregulated, and 63 that were significantly downregulated in KSHV-infected TIGK cells. The differential metabolites included ornithine, arginine, putrescine, dimethylarginine, orotate, glutamate, and glutamine, and were associated with pathways, such as the urea cycle, polyamine synthesis, dimethylarginine synthesis, and de novo pyrimidine synthesis. Overall, our untargeted metabolomics analysis revealed that KSHV infection results in marked rapid alterations in the metabolic profile of the oral epithelial cells. We envision that a subset of these rapid metabolic changes might result in altered cellular functions that can promote viral lytic replication and transmission in the oral cavity.

Association between human herpesviruses and head and neck squamous cell carcinoma: a molecular perspective

BACKGROUND

Head and neck cancer (HNC) is the seventh most common malignant tumor. Herpesviruses are a significant risk factor in the multifactorial pathogenesis of HNC.

OBJECTIVES

This study aimed to investigate the association between herpesviruses and the development of head and neck squamous cell carcinoma (HN-SCC).

DESIGN

Experimental study.

SETTING

A university hospital in Turkey.

PATIENTS AND METHODS

Pathological archive tissue samples of 500 patients were included in the study. These samples were categorized into two groups: those diagnosed with HN-SCC (n=300, malignant group [MG]) and those diagnosed with benign head and neck lesions (n=200, benign group [BG]). The presence of herpesvirus in samples was detected using polymerase chain reaction.

MAIN OUTCOME MEASURES

Association of herpesviruses in the development of head and neck cancer.

SAMPLE SIZE

500 patients.

RESULTS

HHV-1, -2, -7, and -8 were not detected in any samples. In the malignant group (MG), EBV-DNA was detected in 1 patient (0.3%) and HHV-6 DNA in 2 patients (0.6%), while in the benign group (BG), VZV-DNA was detected in 1 patient (0.5%), EBV-DNA in 3 patients (1.5%), CMV-DNA in 5 patients (2.5%), and HHV-6 DNA in 3 patients (1.5%). While no significant difference was found between the groups for VZV, EBV, and HHV-6, a statistically significant difference was found in favor of the benign group for CMV.

CONCLUSION

Although herpesvirus seroprevalence is relatively high in the population, the lack of viral genome in tissue samples indicates that other factors might be prominent in developing HN-SCC.

LIMITATION

The storage conditions of the sample used (paraffinized sample) may have negatively affected the detection frequency of HHVs.

Revealing the viral culprits: the hidden role of the oral virome in head and neck cancers

The oral viral microbiome (or virome), encompassing a diverse community of viruses within the oral cavity, has emerged as a significant yet underexplored factor in head and neck cancers (HNCs). This review synthesizes recent evidence linking the oral virome to head and neck carcinogenesis, particularly oropharyngeal and nasopharyngeal carcinomas-the most common virus-associated subtypes of HNCs. Beyond pathogenesis, the diagnostic and therapeutic implications of the oral virome are explored, including non-invasive salivary detection of viral biomarkers for early cancer diagnosis, the development of targeted antiviral therapies, and preventive vaccination strategies-exemplified by the success of HPV vaccines in reducing the incidence of oropharyngeal cancers. Despite these advancements, challenges persist, including technical limitations, the need for longitudinal studies, and the integration of multi-omics approaches. A comprehensive understanding of the oral virome could revolutionize cancer diagnostics, therapeutics, and prevention. Moving forward, collaborative interdisciplinary efforts will be essential to fully leverage virome research for improving HNC outcomes.

Viral Load Measurements for Kaposi Sarcoma Herpesvirus (KSHV/HHV8): Review and an Updated Assay

"When you can measure what you are speaking about, and express it in numbers, you know something about it." is a famous quote attributed to Lord Kelvin. This sentiment puts viral load measurements at the center of virology. Viral load, or more precisely, DNA copy number measurements, are also used to follow infections with human herpesviruses, such as Kaposi sarcoma herpesvirus (KSHV) and Epstein-Barr Virus (EBV). EBV and KSHV are associated with human cancers, and determining their DNA copy numbers in the context of cancer prediction and progression on therapy is of fundamental scientific and translational interest. Yet, there is no generally accepted assay for KSHV DNA quantitation, and KSHV viral load is not used in clinical decision-making. Here, we review the history of KSHV DNA detection assays, explore factors that affect sensitivity and specificity, and describe an automated, high-throughput, real-time quantitative polymerase chain reaction (PCR) assay for KSHV and EBV. In conjunction with a digital PCR assay using the same primer/probe combination, we describe how to determine the absolute KSHV genome copy numbers in plasma, peripheral blood mononuclear cells, saliva, and other easily accessible body fluids.

Nelfinavir inhibition of Kaposi's sarcoma-associated herpesvirus protein expression and capsid assembly

BACKGROUND

Antiviral therapies that target herpesviruses are clinically important. Nelfinavir is a protease inhibitor that targets the human immunodeficiency virus (HIV) aspartyl protease. Previous studies demonstrated that this drug could also inhibit Kaposi's sarcoma-associated herpesvirus (KSHV) production. Our laboratory demonstrated nelfinavir can effectively inhibit herpes simplex virus type 1 (HSV-1) replication. For HSV-1 we were able to determine that virus capsids were assembled and exited the nucleus but did not mature in the cytoplasm indicating the drug inhibited secondary envelopment of virions.

METHODS

For KSHV, we recently derived a tractable cell culture system that allowed us to analyze the virus replication cycle in greater detail. We used this system to further define the stage at which nelfinavir inhibits KSHV replication.

RESULTS

We discovered that nelfinavir inhibits KSHV extracellular virus production. This was seen when the drug was incubated with the cells for 3 days and when we pulsed the cells with the drug for 1-5 min. When KSHV infected cells exposed to the drug were examined using ultrastructural methods there was an absence of mature capsids in the nucleus indicating a defect in capsid assembly. Because nelfinavir influences the integrated stress response (ISR), we examined the expression of viral proteins in the presence of the drug. We observed that the expression of many were significantly changed in the presence of drug. The accumulation of the capsid triplex protein, ORF26, was markedly reduced. This is an essential protein required for herpesvirus capsid assembly.

CONCLUSIONS

Our studies confirm that nelfinavir inhibits KSHV virion production by disrupting virus assembly and maturation. This is likely because of the effect of nelfinavir on the ISR and thus protein synthesis and accumulation of the essential triplex capsid protein, ORF26. Of interest is that inhibition requires only a short exposure to drug. The source of infectious virus in saliva has not been defined in detail but may well be lymphocytes or other cells in the oral mucosa. Thus, it might be that a "swish and spit" exposure rather than systemic administration would prevent virion production.

Detection of Felis catus Gammaherpesvirus 1 in Domestic Cat Saliva: Prevalence, Risk Factors, and Attempted Virus Isolation

Felis catus gammaherpesvirus 1 (FcaGHV1) infects domestic cats worldwide, yet it has not been successfully propagated in cell culture, and little is known about how it is shed and transmitted. To investigate the salivary shedding of FcaGHV1, we quantified FcaGHV1 DNA in feline saliva by qPCR. For FcaGHV1-positive saliva, we sequenced a portion of the viral glycoprotein B (gB) gene and attempted to isolate the infectious virus by passage in several felid and non-felid cell lines. We detected FcaGHV1 DNA in 45/227 (19.8%) saliva samples with variable viral DNA loads from less than 100 to greater than 3 million copies/mL (median 4884 copies/mL). Multiple saliva samples collected from an infected cat over a two-month period were consistently positive, indicating that chronic shedding can occur for at least two months. Cat age, sex, and health status were not associated with shedding prevalence or viral DNA load in saliva. Feral status was also not associated with shedding prevalence. However, feral cats had significantly higher FcaGHV1 DNA load than non-feral cats. Sequencing of FcaGHV1 gB showed low sequence diversity and >99.5% nucleotide identity to the worldwide consensus FcaGHV1 gB sequence. We did not detect virus replication during the passage of FcaGHV1-positive saliva in cell culture, as indicated by consistently negative qPCR on cell lysate and supernatant. To our knowledge, these data show for the first time that cats in Canada are infected with FcaGHV1. The data further suggest that shedding of FcaGHV1 in saliva is common, can occur chronically over an extended period of time, and may occur at higher levels in feral compared to non-feral cats.

Nelfinavir Inhibition of Kaposi's sarcoma-associated herpesvirus protein expression and capsid assembly

Background

Antiviral therapies that target herpesviruses are clinically important. Nelfinavir is a protease inhibitor that targets the human immunodeficiency virus (HIV) infections aspartyl protease. Previous studies demonstrated that this drug could also inhibit Kaposi's sarcoma-associated herpesvirus (KSHV) production. Our laboratory demonstrated nelfinavir can effectively inhibit herpes simplex virus type 1 (HSV-1) replication. For HSV-1 we were able to determine that virus capsids were assembled and exited the nucleus but did not mature in the cytoplasm indicating the drug inhibited secondary envelopment of virions.

Methods

For KSHV, we recently derived a tractable cell culture system that allowed us to analyze the virus replication cycle in detail. We used this system to further define the stage at which nelfinavir inhibits KSHV replication.

Results

We discovered that nelfinavir inhibits KSHV extracellular virus production. This was seen when the drug was incubated with the cells for 3 days and when we pulsed the cells with the drug for 1-5 minutes. When KSHV infected cells exposed to the drug were examined using ultrastructural methods there was an absence of mature capsids in the nucleus indicating a defect in capsid assembly. Because nelfinavir influences the integrated stress response (ISR), we examined the expression of viral proteins in the presence of the drug. We observed that the expression of many were significantly changed in the presence of drug. The accumulation of the capsid triplex protein ORF26 was markedly reduced. This is an essential protein required for herpesvirus capsid assembly.

Conclusions

Our studies confirm that nelfinavir inhibits KSHV virion production by disrupting virus assembly and maturation. Of interest is that inhibition requires only a short exposure to drug. The source of infectious virus in saliva has not been defined in detail but may well be lymphocytes or other cells in the oral mucosa. Thus, it might be that a "swish and spit" exposure rather than systemic administration would prevent virion production.

Macrophages drive KSHV B cell latency

Kaposi's sarcoma herpesvirus (KSHV) establishes lifelong infection and persists in latently infected B cells. Paradoxically, in vitro B cell infection is inefficient, and cells rapidly die, suggesting the absence of necessary factor(s). KSHV epidemiology unexpectedly mirrors that of malaria and certain helminthic infections, while other herpesviruses are ubiquitous. Elevated circulating monocytes are common in these parasitic infections. Here, we show that KSHV infection of monocytes or M-CSF-differentiated (M2) macrophages is highly efficient. Proteomic analyses demonstrate that infection induces macrophage production of B cell chemoattractants and activating factor. We find that KSHV acts with monocytes or M2 macrophages to stimulate B cell survival, proliferation, and plasmablast differentiation. Further, macrophages drive infected plasma cell differentiation and long-term viral latency. In Kenya, where KSHV is endemic, we find elevated monocyte levels in children with malaria. These findings demonstrate a role for mononuclear phagocytes in KSHV B cell latency and suggest that mononuclear phagocyte abundance may underlie KSHV's geographic disparity.

Kaposi's Sarcoma-Associated Herpesvirus Immediate Early Proteins Trigger FOXQ1 Expression in Oral Epithelial Cells, Engaging in a Novel Lytic Cycle-Sustaining Positive Feedback Loop

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic gammaherpesvirus that can replicate in oral epithelial cells to promote viral transmission via saliva. To identify novel regulators of KSHV oral infection, we performed a transcriptome analysis of KSHV-infected primary human gingival epithelial (HGEP) cells, which identified the gene coding for the host transcription factor FOXQ1 as the top induced host gene. FOXQ1 is nearly undetectable in uninfected HGEP and telomerase-immortalized gingival keratinocytes (TIGK) cells but is highly expressed within hours of KSHV infection. We found that while the FOXQ1 promoter lacks activating histone acetylation marks in uninfected oral epithelial cells, these marks accumulate in the FOXQ1 promoter in infected cells, revealing a rapid epigenetic reprogramming event. To evaluate FOXQ1 function, we depleted FOXQ1 in KSHV-infected TIGK cells, which resulted in reduced accumulation of KSHV lytic proteins and viral DNA over the course of 4 days of infection, uncovering a novel lytic cycle-sustaining role of FOXQ1. A screen of KSHV lytic proteins demonstrated that the immediate early proteins ORF45 and replication and transcription activator (RTA) were both sufficient for FOXQ1 induction in oral epithelial cells, indicating active involvement of incoming and rapidly expressed factors in altering host gene expression. ORF45 is known to sustain extracellular signal-regulated kinase (ERK) p90 ribosomal s6 kinase (RSK) pathway activity to promote lytic infection. We found that an ORF45 mutant lacking RSK activation function failed to induce FOXQ1 in TIGK cells, revealing that ORF45 uses a shared mechanism to rapidly induce both host and viral genes to sustain lytic infection in oral epithelial cells. IMPORTANCE The oral cavity is a primary site of initial contact and entry for many viruses. Viral replication in the oral epithelium promotes viral shedding in saliva, allowing interpersonal transmission, as well as spread to other cell types, where chronic infection can be established. Understanding the regulation of KSHV infection in the oral epithelium would allow for the design of universal strategies to target the first stage of viral infection, thereby halting systemic viral pathogenesis. Overall, we uncover a novel positive feedback loop in which immediate early KSHV factors drive rapid host reprogramming of oral epithelial cells to sustain the lytic cycle in the oral cavity.

Clinical Manifestations and Epigenetic Regulation of Oral Herpesvirus Infections

The oral cavity is often the first site where viruses interact with the human body. The oral epithelium is a major site of viral entry, replication and spread to other cell types, where chronic infection can be established. In addition, saliva has been shown as a primary route of person-to-person transmission for many viruses. From a clinical perspective, viral infection can lead to several oral manifestations, ranging from common intraoral lesions to tumors. Despite the clinical and biological relevance of initial oral infection, little is known about the mechanism of regulation of the viral life cycle in the oral cavity. Several viruses utilize host epigenetic machinery to promote their own life cycle. Importantly, viral hijacking of host chromatin-modifying enzymes can also lead to the dysregulation of host factors and in the case of oncogenic viruses may ultimately play a role in promoting tumorigenesis. Given the known roles of epigenetic regulation of viral infection, epigenetic-targeted antiviral therapy has been recently explored as a therapeutic option for chronic viral infection. In this review, we highlight three herpesviruses with known roles in oral infection, including herpes simplex virus type 1, Epstein–Barr virus and Kaposi’s sarcoma-associated herpesvirus. We focus on the respective oral clinical manifestations of these viruses and their epigenetic regulation, with a specific emphasis on the viral life cycle in the oral epithelium.

Novel modulators of p53-signaling encoded by unknown genes of emerging viruses

The p53 transcription factor plays a key role both in cancer and in the cell-intrinsic response to infections. The ORFEOME project hypothesized that novel p53-virus interactions reside in hitherto uncharacterized, unknown, or hypothetical open reading frames (orfs) of human viruses. Hence, 172 orfs of unknown function from the emerging viruses SARS-Coronavirus, MERS-Coronavirus, influenza, Ebola, Zika (ZIKV), Chikungunya and Kaposi Sarcoma-associated herpesvirus (KSHV) were de novo synthesized, validated and tested in a functional screen of p53 signaling. This screen revealed novel mechanisms of p53 virus interactions and two viral proteins KSHV orf10 and ZIKV NS2A binding to p53. Originally identified as the target of small DNA tumor viruses, these experiments reinforce the notion that all viruses, including RNA viruses, interfere with p53 functions. These results validate this resource for analogous systems biology approaches to identify functional properties of uncharacterized viral proteins, long non-coding RNAs and micro RNAs.

New viruses are constantly emerging. The ORFEOME project was based on the hypothesis that every virus, regardless of its molecular makeup and biology should encode functions that intersect the p53 signaling network, since p53 guards the cell from genomic insults, of which depositing a foreign, viral nucleic acid is one. The result of the ORFEOME screen of proteins without any known function, of predicted open reading frames and of suspected non-coding RNAs is the identification of two viral proteins that interact with p53. The first one, orf10, is encoded by Kaposi Sarcoma-associated herpesvirus and the second one, NS2A, is encoded by the Zika virus.

Analysis of KSHV B lymphocyte lineage tropism in human tonsil reveals efficient infection of CD138+ plasma cells

Despite 25 years of research, the basic virology of Kaposi Sarcoma Herpesviruses (KSHV) in B lymphocytes remains poorly understood. This study seeks to fill critical gaps in our understanding by characterizing the B lymphocyte lineage-specific tropism of KSHV. Here, we use lymphocytes derived from 40 human tonsil specimens to determine the B lymphocyte lineages targeted by KSHV early during de novo infection in our ex vivo model system. We characterize the immunological diversity of our tonsil specimens and determine that overall susceptibility of tonsil lymphocytes to KSHV infection varies substantially between donors. We demonstrate that a variety of B lymphocyte subtypes are susceptible to KSHV infection and identify CD138+ plasma cells as a highly targeted cell type for de novo KSHV infection. We determine that infection of tonsil B cell lineages is primarily latent with few lineages contributing to lytic replication. We explore the use of CD138 and heparin sulfate proteoglycans as attachment factors for the infection of B lymphocytes and conclude that they do not play a substantial role. Finally, we determine that the host T cell microenvironment influences the course of de novo infection in B lymphocytes. These results improve our understanding of KSHV transmission and the biology of early KSHV infection in a naïve human host, and lay a foundation for further characterization of KSHV molecular virology in B lymphocyte lineages.

KSHV infection is associated with cancer in B cells and endothelial cells, particularly in the context of immune suppression. Very little is known about how KSHV is transmitted and how it initially establishes infection in a new host. Saliva is thought to be the primary route of person-to-person transmission for KSHV, making the tonsil a likely first site for KSHV replication in a new human host. Our study examines KSHV infection in B cells extracted from the tonsils of 40 human donors in order to determine what types of B cells are initially targeted for infection and examine how the presence (or absence) of other immune cells influence the initial stages of KSHV infection. We found that a variety of B cell subtypes derived from tonsils can be infected with KSHV. Interestingly, plasma cells (mature antibody-secreting B cells) were a highly targeted cell type. These results lay the foundation for further studies into the specific biology of KSHV in different types of B cells, an effort that may help us ultimately discover how to prevent the establishment of infection in these cells or reveal new ways to halt the progression of B cell cancers associated with KSHV infection.

Herpesviruses in Head and Neck Cancers

Head and neck cancers arise in the mucosa lining the oral cavity, oropharynx, hypopharynx, larynx, sinonasal tract, and nasopharynx. The etiology of head and neck cancers is complex and involves many factors, including the presence of oncogenic viruses. These types of cancers are among the most common cancers in the world. Thorough knowledge of the pathogenesis of viral infections is needed to fully understand their impact on cancer development.

Gammaherpesvirus entry and fusion: A tale how two human pathogenic viruses enter their host cells

The prototypical human γ-herpesviruses Epstein-Barr virus (EBV) and Kaposi Sarcoma-associated herpesvirus (KSHV) are involved in the development of malignancies. Like all herpesviruses, they share the establishment of latency, the typical architecture, and the conserved fusion machinery to initiate infection. The fusion machinery reflects virus-specific adaptations due to the requirements of the respective herpesvirus. For example, EBV evolved a tropism switch involving either the B- or epithelial cell-tropism complexes to activate fusion driven by gB. Most of the EBV entry proteins and their cellular receptors have been crystallized providing molecular details of the initial steps of infection. For KSHV, a variety of entry and binding receptors has also been reported but the mechanism how receptor binding activates gB-driven fusion is not as well understood as that for EBV. However, the downstream signaling pathways that promote the early steps of KSHV entry are well described. This review summarizes the current knowledge of the key players involved in EBV and KSHV entry and the cell-type specific mechanisms that allow infection of a wide variety of cell types.

Glycoprotein K8.1A of Kaposi's Sarcoma-Associated Herpesvirus Is a Critical B Cell Tropism Determinant Independent of Its Heparan Sulfate Binding Activity

B lymphocytes are the major cellular reservoir in individuals infected with Kaposi's sarcoma-associated herpesvirus (KSHV), and the virus is etiologically linked to two B cell lymphoproliferative disorders. We previously described the MC116 human B cell line as a KSHV-susceptible model to overcome the paradoxical refractoriness of B cell lines to experimental KSHV infection. Here, using monoclonal antibody inhibition and a deletion mutant virus, we demonstrate that the KSHV virion glycoprotein K8.1A is critical for infection of MC116, as well as tonsillar B cells; in contrast, we confirm previous reports on the dispensability of the glycoprotein for infection of primary endothelial cells and other commonly studied non-B cell targets. Surprisingly, we found that the role of K8.1A in B cell infection is independent of its only known biochemical activity of binding to surface heparan sulfate, suggesting the possible involvement of an additional molecular interaction(s). Our finding that K8.1A is a critical determinant for KSHV B cell tropism parallels the importance of proteins encoded by positionally homologous genes for the cell tropism of other gammaherpesviruses.IMPORTANCE Elucidating the molecular mechanisms by which KSHV infects B lymphocytes is critical for understanding how the virus establishes lifelong persistence in infected people, in whom it can cause life-threatening B cell lymphoproliferative disease. Here, we show that K8.1A, a KSHV-encoded glycoprotein on the surfaces of the virus particles, is critical for infection of B cells. This finding stands in marked contrast to previous studies with non-B lymphoid cell types, for which K8.1A is known to be dispensable. We also show that the required function of K8.1A in B cell infection does not involve its binding to cell surface heparan sulfate, the only known biochemical activity of the glycoprotein. The discovery of this critical role of K8.1A in KSHV B cell tropism opens promising new avenues to unravel the complex mechanisms underlying infection and disease caused by this viral human pathogen.

Cell Type-Specific Interferon-γ-mediated Antagonism of KSHV Lytic Replication

Kaposi’s sarcoma-associated herpesvirus (KSHV) is causally associated with several malignant tumors: Kaposi’s sarcoma (KS), multicentric Castleman’s disease (MCD), and primary effusion lymphoma (PEL). KS remains the most common AIDS-related malignancy since the AIDS epidemic and thus has been extensively studied. KS is characterized as an angioproliferative disease with massive immune cell infiltration at the early stage. High levels of proinflammatory cytokines and growth factors are found in KS lesions, and their involvement in the survival and growth of tumor cells has been well characterized. However, little is known about the role of the inflammatory microenvironment in the regulation of KSHV gene expression and/or viral replication. In the present study, we demonstrated that IFN-γ and TNF-α profoundly inhibited KSHV progeny production in primary human lymphatic endothelial cells (LECs) as well as induced KSHV-producer cells (iSLK.219) with doxycycline. Of note, IFN-γ inhibited overall KSHV gene expression, while the effects of TNF-α were confined to a selected set of genes, which were also downregulated by IFN-γ. The addition of IFN-γ up to 36 hr after induction of viral lytic replication was effective in terms of the inhibition of infectious virion production, suggesting that its inhibitory effect is exerted at the early stages of KSHV life cycle. We believe these data have potentially important implications for rationalizing a therapeutic agent to treat KSHV-induced tumors in which lytic replication plays a critical role in their pathogenesis: KS and MCD.

Kaposi's Sarcoma-Associated Herpesvirus (KSHV)-Associated Disease in the AIDS Patient: An Update

In this book chapter, we review the current knowledge of the biology and pathogenesis of Kaposi's sarcomaassociated herpesvirus (KSHV). We describe the lifecycle of KSHV, the cancers associated with this virus, as well as current treatment modalities.

Oral shedding of herpesviruses in HIV-infected patients with varying degrees of immune status

OBJECTIVE

Herpesvirus shedding in the oral cavity was analyzed to determine if presence in the oral compartment correlates with systemic changes in HIV-associated immune deficiency as measured by CD4 cell counts, plasma HIV viral load and presence of AIDS-defining events.

DESIGN

A5254 is a multicenter, cross-sectional, single-visit study to evaluate oral complications of HIV/AIDS and determine the association between clinical appearance, herpesvirus shedding, and immune status as ascertained by CD4 cell count and HIV viral load. In total, 307 HIV-infected individuals were evaluated and throat wash collected.

METHODS

Fisher's exact test and Kruskal-Wallis test were used to assess the association between presence of herpesviruses and the state of immunodeficiency as stratified by a combination of CD4 cell count and HIV viral load. Relationship between pathogens and HIV viral load in plasma was modeled by logistic regression.

RESULTS

The presence of cytomegalovirus (CMV) and herpes simplex virus-1 in throat wash was associated with decreased CD4 cell counts. By contrast, Kaposi sarcoma-associated herpesvirus and Epstein-Barr virus were similarly detectable across all levels of CD4 cell counts. One unit increase in log10 (HIV viral load) was associated with 1.31 times higher odds of detecting CMV in throat wash when controlling for oral candidiasis, CD4 cell count, and sites (95% confidence interval 1.04-1.65, P = 0.02).

CONCLUSION

Oral CMV shedding was significantly higher in highly immunocompromised HIV participants. Our finding supports the recommendations to start antiretroviral therapy independent of CD4 cell count as this may have the added benefit to lower the risk of herpesvirus transmission among persons infected with HIV and their partners.

Primary lymphocyte infection models for KSHV and its putative tumorigenesis mechanisms in B cell lymphomas

Kaposi's sarcoma-associated herpesvirus (KSHV) is the latest addition to the human herpesvirus family. Unlike alpha- and beta-herpesvirus subfamily members, gamma-herpesviruses, including Epstein-Barr virus (EBV) and KSHV, cause various tumors in humans. KSHV primarily infects endothelial and B cells in vivo, and is associated with at least three malignancies: Kaposi's sarcoma and two B cell lymphomas, respectively. Although KSHV readily infects endothelial cells in vitro and thus its pathogenic mechanisms have been extensively studied, B cells had been refractory to KSHV infection. As such, functions of KSHV genes have mostly been elucidated in endothelial cells in the context of viral infection but not in B cells. Whether KSHV oncogenes, defined in endothelial cells, play the same roles in the tumorigenesis of B cells remains an open question. Only recently, through a few ground-breaking studies, B cell infection models have been established. In this review, those models will be compared and contrasted and putative mechanisms of KSHV-induced B cell transformation will be discussed.

Viral Diseases Transmissible by Kissing

Viral infections can be transmitted by various routes. At one extreme, airborne or droplet viral infections (e.g., varicella zoster, ebola) are highly contagious. Most viruses can be spread by touching surfaces contaminated by the virus and then touching the mouth or eyes. Mass gatherings, clinical, and chronic care facilities may be hotspots for virus spread when transmission is via aerosols, droplets, or fomites (contaminated surfaces). Environmental factors which are often important for virus survival may include the ambient humidity, temperature, and pH of the environment they are in, so many viruses survive only a few hours in the environment and are often readily inactivated by common hygiene techniques, such as using soap and water, and some detergents, disinfectants, and antiseptics. Sexually transmitted viral infections, such as herpes simplex, are often transmitted by close mucosal contacts.

Prevalence of Human Herpesvirus-8 Salivary Shedding in HIV Increases with CD4 Count

Human herpesvirus-8 (HHV-8) is the etiologic agent of Kaposi’s sarcoma (KS), which occurs in epidemic form in human immunodeficiency virus(HIV)-infected individuals. Saliva is the only mucosal fluid in which infectious HHV-8 has been identified, although factors associated with HHV-8 salivary shedding remain unclear. Our study performed PCR analysis for HHV-8 DNA in saliva (and other body fluids) in 66 HIV- and HHV-8-co-infected women without KS so that we could examine predictors for HHV-8 DNA detection. CD4 count was the most significant predictor of HHV-8 salivary shedding, with increased prevalence of HHV-8 salivary DNA at higher CD4 counts. The odds of salivary HHV8 shedding at CD4 counts > = 350 cells/μL was 63 times the odds of shedding at CD4 < 350 (95%CI, 1.3–3078), with an increase in effect size when the analysis was restricted to those with a CD4 nadir > 200. Analysis of these data suggests an increased potential for HHV-8 transmission early in HIV infection, with implications for HHV-8 prevention.

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.

Oral EBV and KSHV Infection in HIV

The gamma herpesviruses, Kaposi’s-sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are tightly associated with the development of AIDS-associated oral disease and malignancy during immune suppression. The objective of this investigation was to characterize oral infection and pathogenesis in healthy and immune-suppressed individuals. To characterize oral EBV and KSHV infection, we examined throat washings and oral epithelial cells from HIV-positive and HIV-negative individuals. Quantitative/real-time polymerase-chain-reaction (PCR) assays, transmission electronmicroscopy, immunostaining, and sequence analysis were used to identify viral infection. Virus was isolated from throat-wash samples and was used to infect epithelial and lymphoid cell lines. We detected EBV and KSHV in the oral cavity in healthy and immune-suppressed individuals. Viral strain analysis of KSHV K1 in multiple clones from the oral cavities of healthy persons and immunosuppressed patients detected several strains previously detected in KS lesions, with minor strain variation within individuals. Immunoelectron microscopy for multiple viral antigens detected consistent expression of viral proteins and oral epithelial specimens. In oral epithelial cells infected with wild-type KSHV in vitro, the K8.1 glycoprotein associated with lytic KSHV infection was detected in both primary and telomerase immortalized oral epithelial cultures by 24 hours post-infection. Virions were detected, subsequent to infection, by scanning electron microscopy. Oral epithelial cells were also infected in vitro with wild-type EBV originating from throat washes. Analysis of these data suggests that, like EBV, KSHV infection is present in the oropharynx of healthy individuals, is transmissible in vitro, and may be transmitted by saliva.

OX40 and 4-1BB downregulate Kaposi’s sarcoma-associated herpesvirus replication in lymphatic endothelial cells, but 4-1BB and not OX40 inhibits viral replication in B-cells

Kaposi’s sarcoma-associated herpesvirus (KSHV) belongs to the human gammaherpesvirus subfamily and is associated with malignancies of endothelial origin (Kaposi’s sarcoma, KS) and B-cell origin [primary effusion lymphoma (PEL) and multicentric Castleman’s disease (MCD)]. Viral lytic replication is known to be required for KS and MCD. As KSHV-related tumours mostly develop in human subjects when the immune system is compromised by immunosuppressive regimen, human immunodeficiency virus infection or some genetic deficiencies, KSHV-specific immune responses are believed to be important in the control of KSHV replication. However, analysis of the roles of immune cells in viral pathogenesis has been difficult due to the lack of an adequate animal model. Recently, congenital OX40 deficiency, as determined by genome-wide exome sequencing, was shown to be associated with aggressive childhood KS in a patient, suggesting that disrupted OX40–OX40L interactions might be implicated in disease development. Here, we report that interaction of recombinant OX40 protein with OX40L expressed on endothelial cells severely impaired KSHV lytic replication. Furthermore, 4-1BB–4-1BBL interactions were also capable of efficiently inhibiting viral replication in B-cells and endothelial cells. To the best of our knowledge, this is the first direct evidence that ligation of tumour necrosis factor superfamily members and their cognate receptors is important for the control of viral lytic replication. These data are likely to pave the way for the development of KSHV-specific therapies for KS and MCD, in which viral lytic replication is a disease-determining factor.

Efficient lytic induction of Kaposi's sarcoma-associated herpesvirus (KSHV) by the anthracyclines

Lytic induction of latent Kaposi's sarcoma-associated herpesvirus (KSHV) has been considered as a therapeutic option for efficient treatment of several KSHV-associated malignancies. Here, we developed a robust high-throughput screening system that allows an easy and quantitative measurement of lytic induction of latent KSHV and discovered three anthracyclines as potent inducers from screen of FDA-approved drugs. Lytic induction of latent KSHV by three compounds was verified by the significant induction of lytic genes and subsequent production of infectious KSHV. Importantly, lytic induction by three compounds was much more efficient than that by sodium butyrate, a well-characterized inducer of KSHV lytic cycle. Mechanistically, the anthracyclines caused lytic induction of KSHV through apoptosis induced by their DNA intercalation rather than topoisomerase II inhibition. Consequently, our results clearly demonstrated a role of anthracyclines as effective lytic inducers of KSHV and also provided a molecular basis of their use for efficient treatment of diseases associated with KSHV infection.

Interaction of human tumor viruses with host cell surface receptors and cell entry

Currently, seven viruses, namely Epstein-Barr virus (EBV), Kaposi's sarcoma-associated herpes virus (KSHV), high-risk human papillomaviruses (HPVs), Merkel cell polyomavirus (MCPyV), hepatitis B virus (HBV), hepatitis C virus (HCV) and human T cell lymphotropic virus type 1 (HTLV-1), have been described to be consistently associated with different types of human cancer. These oncogenic viruses belong to distinct viral families, display diverse cell tropism and cause different malignancies. A key to their pathogenicity is attachment to the host cell and entry in order to replicate and complete their life cycle. Interaction with the host cell during viral entry is characterized by a sequence of events, involving viral envelope and/or capsid molecules as well as cellular entry factors that are critical in target cell recognition, thereby determining cell tropism. Most oncogenic viruses initially attach to cell surface heparan sulfate proteoglycans, followed by conformational change and transfer of the viral particle to secondary high-affinity cell- and virus-specific receptors. This review summarizes the current knowledge of the host cell surface factors and molecular mechanisms underlying oncogenic virus binding and uptake by their cognate host cell(s) with the aim to provide a concise overview of potential target molecules for prevention and/or treatment of oncogenic virus infection.

Celecoxib Inhibits the Lytic Activation of Kaposi's Sarcoma-Associated Herpesvirus through Down-Regulation of RTA Expression by Inhibiting the Activation of p38 MAPK

Kaposi’s sarcoma associated herpesvirus (KSHV) is the etiologic agent of Kaposi’s sarcoma (KS), primary effusion lymphoma (PEL), and multicentric Castleman’s disease (MCD). KSHV’s lytic replication cycle is critical for the pathogenesis of KSHV-associated diseases. Despite recent progress in the development of treatments for KSHV associated malignancies, these therapies are not completely efficacious and cause side effects. Therefore, more effective therapies with antiviral agents against KSHV are urgently needed. In this study, we identified celecoxib as an antiviral agent against KSHV. Our data suggest that celecoxib inhibits the lytic activation of KSHV through the down-regulation of the expression of the lytic switch protein, replication and transcription activator (RTA), by inhibiting the activation of p38 MAPK. Therefore, celecoxib may provide a candidate inhibitor for the therapeutic research of KSHV-related malignancies.

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

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

KSHV LANA--the master regulator of KSHV latency

Kaposi's sarcoma associated herpesvirus (KSHV), like other human herpes viruses, establishes a biphasic life cycle referred to as dormant or latent, and productive or lytic phases. The latent phase is characterized by the persistence of viral episomes in a highly ordered chromatin structure and with the expression of a limited number of viral genes. Latency Associated Nuclear Antigen (LANA) is among the most abundantly expressed proteins during latency and is required for various nuclear functions including the recruitment of cellular machineries for viral DNA replication and segregation of the replicated genomes to daughter cells. LANA achieves these functions by recruiting cellular proteins including replication factors, chromatin modifying enzymes and cellular mitotic apparatus assembly. LANA directly binds to the terminal repeat region of the viral genome and associates with nucleosomal proteins to tether to the host chromosome. Binding of LANA to TR recruits the replication machinery, thereby initiating DNA replication within the TR. However, other regions of the viral genome can also initiate replication as determined by Single Molecule Analysis of the Replicated DNA (SMARD) approach. Recent, next generation sequence analysis of the viral transcriptome shows the expression of additional genes during latent phase. Here, we discuss the newly annotated latent genes and the role of major latent proteins in KSHV biology.

Seroprevalence and determinants of Kaposi sarcoma-associated human herpesvirus 8 in Indian HIV-infected males

In India Kaposi's sarcoma is rarely seen in AIDS patients. Hence the current belief is that the incidence of human herpesvirus-8 (HHV-8) is very low in this subcontinent, most probably due to the heterosexual route of HIV transmission. However, there is a scarcity of data on the prevalence of HHV-8 in India. In India the primary mode of HIV transmission is the heterosexual route. Therefore we aimed to determine the prevalence of antibodies against HHV-8 in North Indian HIV-infected men naive of antiretroviral therapy (ART). In a prospective study, 165 Indian adult males were recruited from an ART clinic. Blood samples were collected before administering any antiretroviral drug. The sera were tested for antibodies against HHV-8 using a commercial enzyme-linked immunosorbent assay (ELISA) kit, which detects IgG antibodies to lytic antigens of HHV-8. All positive samples were confirmed for the presence of anti-HHV-8 antibodies using an indirect immunofluorescence assay (IFA). The IFA kit is intended to detect primary, latent, persistent, or reactivated infection of HHV-8. Of the 165 males, 43 (26.06%) were positive by ELISA while 26 (15.8%) were also positive by IFA. Seroprevalence decreased with increasing age (p<0.05). Factors independently associated with HHV-8 infection were younger age group and alcohol consumption. These findings suggest that even in a heterosexual population, HHV-8 can be transmitted frequently.

Dendritic cells: key players in human herpesvirus 8 infection and pathogenesis

Human herpesvirus 8 (HHV-8; Kaposi's sarcoma-associated herpesvirus) is an oncogenic gammaherpesvirus that primarily infects cells of the immune and vascular systems. HHV-8 interacts with and targets professional antigen presenting cells and influences their function. Infection alters the maturation, antigen presentation, and immune activation capabilities of certain dendritic cells (DC) despite non-robust lytic replication in these cells. DC sustains a low level of antiviral functionality during HHV-8 infection in vitro. This may explain the ability of healthy individuals to effectively control this virus without disease. Following an immune compromising event, such as organ transplantation or human immunodeficiency virus type 1 infection, a reduced cellular antiviral response against HHV-8 compounded with skewed DC cytokine production and antigen presentation likely contributes to the development of HHV-8 associated diseases, i.e., Kaposi's sarcoma and certain B cell lymphomas. In this review we focus on the role of DC in the establishment of HHV-8 primary and latent infection, the functional state of DC during HHV-8 infection, and the current understanding of the factors influencing virus-DC interactions in the context of HHV-8-associated disease.

Kaposi's sarcoma-associated herpesvirus ORF18 and ORF30 are essential for late gene expression during lytic replication

Kaposi's sarcoma-associated herpesvirus (KSHV) is associated with several human malignances. As saliva is likely the major vehicle for KSHV transmission, we studied in vitro KSHV infection of oral epithelial cells. Through infection of two types of oral epithelial cells, normal human oral keratinocytes (NHOKs) and papilloma-immortalized human oral keratinocyte (HOK16B) cells, we found that KSHV can undergo robust lytic replication in oral epithelial cells. By employing de novo lytic infection of HOK16B cells, we studied the functions of two previously uncharacterized genes, ORF18 and ORF30, during the KSHV lytic cycle. For this purpose, an ORF18-deficient virus and an ORF30-deficient virus were generated using a mutagenesis strategy based on bacterial artificial chromosome (BAC) technology. We found that neither ORF18 nor ORF30 is required for immediately early or early gene expression or viral DNA replication, but each is essential for late gene expression during both de novo lytic replication and reactivation. This critical role of ORF18 and ORF30 in late gene expression was also observed during KSHV reactivation. In addition, global analysis of viral transcripts by RNA sequencing indicated that ORF18 and ORF30 control the same set of viral genes. Therefore, we suggest that these two viral ORFs are involved in the same mechanism or pathway that coregulates the viral late genes as a group.

IMPORTANCE

While KSHV can infect multiple cell types in vitro, only a few can support a full lytic replication cycle with progeny virions produced. Consequently, KSHV lytic replication is mostly studied through reactivation, which requires chemicals to induce the lytic cycle or overexpression of the viral transcriptional activator, RTA. In this study, we present a robust de novo lytic infection system based on oral epithelial cells. Using this system, we demonstrate the role of two viral ORFs, ORF18 and ORF30, in regulating viral gene expression during KSHV lytic replication. As the major route of KSHV transmission is thought to be via saliva, this new KSHV lytic replication system will have important utility in the field.

Efficient infection of a human B cell line with cell-free Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is causatively linked to two B cell lymphoproliferative disorders, multicentric Castleman's disease and primary effusion lymphoma. Latently infected B cells are a major KSHV reservoir, and virus activation from tonsillar B cells can result in salivary shedding and virus transmission. Paradoxically, human B cells (primary and continuous) are notoriously refractory to infection, thus posing a major obstacle to the study of KSHV in this cell type. By performing a strategic search of human B cell lymphoma lines, we found that MC116 cells were efficiently infected by cell-free KSHV. Upon exposure to recombinant KSHV.219, enhanced green fluorescent protein reporter expression was detected in 17 to 20% of MC116 cells. Latent-phase transcription and protein synthesis were detected by reverse transcription-PCR and detection of latency-associated nuclear antigen expression, respectively, in cell lysates and individual cells. Selection based on the puromycin resistance gene in KSHV.219 yielded cultures with all cells infected. After repeated passaging of the selected KSHV-infected cells without puromycin, latent KSHV was maintained in a small fraction of cells. Infected MC116 cells could be induced into lytic phase with histone deacetylase inhibitors, as is known for latently infected non-B cell lines, and also selectively by the B cell-specific pathway involving B cell receptor cross-linking. Lytic-phase transition was documented by red fluorescent protein reporter expression, late structural glycoprotein (K8.1A, gH) detection, and infectious KSHV production. MC116 cells were CD27(-)/CD10(+), characteristic of transitional B cells. These findings represent an important step in the establishment of an efficient continuous B cell line model to study the biologically relevant steps of KSHV infection. Kaposi's sarcoma-associated herpesvirus (KSHV) causes two serious pathologies of B cells, the antibody-producing cells of the immune system. B cells are a major reservoir for KSHV persistence in the body. Paradoxically, in the laboratory, B cells are extremely difficult to infect with KSHV; this problem greatly hinders scientific analysis of B cell infection. We describe our search for and successful identification of a stable human B cell line that can be efficiently infected by KSHV. Upon infection of these cells, the virus goes into a quiet latent phase, a characteristic feature of many herpesvirus infections. The virus can be triggered to enter an active lytic phase by treatments known to stimulate normal B cell functions. These findings suggest that the new B cell line will be a valuable model in which to study KSHV infection of this major target cell type.

Fifty percent tissue culture infective dose assay for determining the titer of infectious human herpesvirus 8

We have developed a human herpesvirus 8 (HHV-8) 50% tissue culture infective dose (TCID50) assay using the T1H6-DC-SIGN cell line. Infection of T1H6-DC-SIGN cells with HHV-8 induces expression of β-galactosidase, which was used to determine TCID50 levels. Validation of TCID50 values was performed by immunofluorescence assay of HHV-8 infection of immature dendritic cells at various TCID50 doses.

Molecular biology of lactoferrin and its role in modulating immunity and viral pathogenesis

Lactoferrin (Lf), also known as lactotransferrin, is a globular glycoprotein belonging to the transferrin family that is widely expressed in several fluids such as milk, tears, gastric fluid and saliva. Apart from its ability to bind and regulate iron levels in body secretions, Lf possesses antimicrobial activity and is specifically a component of the innate immune system. The antibacterial activity of Lf occurs by depriving the environment of iron essential for bacterial growth. In the case of antiviral activity, Lf may act as a competitor for the cell membrane receptors commonly used by viruses to enter cells. This review summarizes the roles of Lf under normal physiology, with a special emphasis on viruses. The authors also discuss in great detail the interactions between Lf and Kaposi’s sarcoma-associated herpesvirus, as well as possible future directions of research that may progress toward designing modern-day therapeutics to counter viral infections.

Human herpesviruses 6, 7 and 8 in solid organ transplant recipients

Human herpesviruses (HHV) 6 and 7 are ubiquitous infections that reactivate commonly in transplant recipients. However, clinical diseases due to these viruses are reported only in 1% of solid organ transplant recipients. Fever, rash and bone marrow suppression are the most common manifestations, but symptoms of tissue invasive disease may be observed. Treatment of HHV-6 and HHV-7 disease includes antiviral therapy and cautious reduction in immunosuppression. HHV-8 is an oncogenic gamma-herpesvirus that causes Kaposi's sarcoma, Castleman's disease and primary effusion lymphomas in transplant recipients. Nonmalignant diseases such as bone marrow suppression and multiorgan failure have also been associated with HHV-8. Reduction in immunosuppression is the first line treatment of HHV-8 infection. Other alternatives for treatment, especially for HHV-8 diseases not responsive to immuno-minimization strategies, are surgery and chemotherapy. Sirolimus has been shown to be a beneficial component for the treatment of Kaposi's sarcoma and the role of antivirals for HHV-8 infection is being investigated.

AKTivation of PI3K/AKT/mTOR signaling pathway by KSHV

As an obligate intracellular parasite, Kaposi sarcoma-associated herpesvirus (KSHV) relies on the host cell machinery to meet its needs for survival, viral replication, production, and dissemination of progeny virions. KSHV is a gammaherpesvirus that is associated with three different malignancies: Kaposi sarcoma (KS), and two B cell lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman’s disease. KSHV viral proteins modulate the cellular phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway, which is a ubiquitous pathway that also controls B lymphocyte proliferation and development. We review the mechanisms by which KSHV manipulates the PI3K/AKT/mTOR pathway, with a specific focus on B cells.

[Seroprevalence and risk factors of human herpes virus 8 infection in Central-East Tunisia]

OBJECTIVE

Epidemiology of human herpesvirus 8 (HHV8) is still unknown in Tunisia. We aimed to assess the prevalence of HHV8 infection in adults and children from Central-East Tunisia and in patients with high risk of parenteral or sexual infection.

METHODS

We enrolled 553 subjects: 116 blood donors, 100 pregnant women, 100 children, 50 subjects with sexually transmitted infections with positive HIV serology and 50 other without HIV infection, 107 multitransfused patients and 30 kidney transplant patients. Antibodies against HHV8 were tested using a sensitive indirect immunofluorescence assay.

RESULTS

The seroprevalence of HHV8 was found to be 13.8% in blood donors, 13% in pregnant women and 12% in children. In healthy adult population, no association was found between HHV8 seropositivity and sex, sociodemographic characteristics, parenteral risk factors or serological markers of hepatitis B. Rates of HHV8 infection were significantly higher in patients having high-risk sexual behavior with or without HIV infection (P<10(-4)), in polytransfused patients (P<10(-4)) and in patients with kidney transplantation (P=0.001).

CONCLUSION

Our findings suggest that HHV8 infection is widespread in Central-East Tunisia such as in the Mediterranean area. HHV8 infection appears to be acquired early in life, probably through saliva. HHV8 transmission by blood transfusion, subject of controversy in literature, is well established in our study. Early screening of this infection should be considered in populations with high risk of Kaposi's sarcoma in our areas.

Viral interleukin-6: role in Kaposi's sarcoma-associated herpesvirus: associated malignancies

Viral interleukin-6 (vIL-6) is a product of Kaposi's sarcoma-associated herpesvirus (KSHV) expressed in latently infected cells and to a higher degree during viral replication. A distinctive feature of vIL-6 is the ability to directly bind and activate gp130 signaling in the absence of other receptor subunits. Secretion of vIL-6 is generally poor, but vIL-6 can activate gp130 from inside the cell. Due to the wide cell distribution of gp130, vIL-6 has the potential to induce a wide range of biological effects. Expression of vIL-6 is variable in KSHV-associated Kaposi's sarcoma (KS), primary effusion lymphoma (PEL), multicentric Castleman's disease (MCD), and in a newly described MCD-like systemic inflammatory syndrome observed in human immunodeficiency virus-positive patients. PEL effusions usually contain vIL-6 at high concentrations; since vIL-6 induces vascular endothelial growth factor, vIL-6 likely contributes to vascular permeability and formation of PEL effusions. Lymph nodes affected with MCD contain vIL-6-positive cells, and vIL-6 levels rise in conjunction with flares of the disease and likely contribute to symptoms of inflammation. The development of vIL-6 inhibitors is a potentially important advance in the treatment of KSHV-associated malignancies where vIL-6 is expressed.

KSHV infects a subset of human tonsillar B cells, driving proliferation and plasmablast differentiation

Kaposi sarcoma-associated herpesvirus (KSHV; also known as HHV8) is the causative agent of two B cell tumors, multicentric Castleman disease (MCD) and primary effusion lymphoma (PEL). However, little is known about the nature of the specific B cell subtype(s) most susceptible to infection. Identifying these cells would provide direct insight into KSHV transmission and virus-induced transformation. To identify this subset and to determine whether infection alters its cellular phenotype, we exposed human tonsillar cells to KSHV and characterized infected cells using high-throughput multispectral imaging flow cytometry (MIFC). Stable expression of the virally encoded latency-associated nuclear antigen (LANA), a marker of latent KSHV infection, was observed predominantly in cells expressing the l light chain of the B cell receptor. These LANA+ B cells proliferated and exhibited similarities to the cells characteristic of MCD (IgMl-expressing plasmablasts), including blasting morphology with elevated expression of Ki67, variable expression of CD27, and high levels of IgM and IL-6 receptor. Furthermore, the proportion of infected cells showing a blasting phenotype increased upon addition of exogenous IL-6. Our data lead us to propose that oral transmission of KSHV involves the latent infection of a subset of tonsillar IgMl-expressing B cells, which then proliferate as they acquire the plasmablast phenotype characteristic of MCD.

Intrafamiliar transmission of Kaposi's sarcoma-associated herpesvirus and seronegative infection in family members of classic Kaposi's sarcoma patients

The link between Kaposi's sarcoma-associated herpesvirus (KSHV or human herpesvirus 8) and Kaposi's sarcoma has been proven, but the transmission routes, especially in the heterosexual population, are not yet completely understood. To assess the intrafamilial patterns of transmission among first-degree relatives of Italian classic Kaposi's sarcoma (cKS) patients, KSHV seroprevalence and the presence of viral DNA in blood and saliva were evaluated in 18 families (32 cKS patients and 35 family members), comparing the results with those obtained in 200 elderly healthy controls without known exposure to KSHV. The KSHV genotype of variable region VR1 of the hypervariable ORF K1 gene was subsequently analysed in all KSHV-positive samples. The results showed that KSHV infection was significantly higher in relatives of cKS patients (11/35 cases) than in healthy controls (17/200 cases; P=0.001). The 11 infected relatives included spouses (n=3), siblings (n=2) and offspring (n=6) of the cKS patients; the same KSHV genotype was shared within the same family in the majority of cases (85%), indicating the presence of person-to-person transmission within families. Viral DNA was mostly observed in the saliva of infected relatives (45.4%); detection of DNA in blood was less frequent (27.3%). Notably, KSHV DNA was present in saliva and/or blood of three KSHV-infected relatives with indeterminate or negative serostatus. Thus, the risk of KSHV infection is greatly enhanced within families of cKS patients, where close contacts (horizontal and/or sexual) can contribute to the spread of KSHV.

The lytic activation of KSHV during keratinocyte differentiation is dependent upon a suprabasal position, the loss of integrin engagement, and calcium, but not the interaction of cadherins

We previously found that KSHV (HHV-8) lytic activation occurs during differentiation of oral keratinocytes in organotypic raft cultures. To further investigate the spatial and temporal aspects of KSHV lytic activation and the roles of integrins, cadherins, and calcium, we used rKSHV.219-infected primary oral keratinocytes in submerged, suspension, and direct suprabasal plating, models of differentiation. We found that early keratinocyte differentiation did not activate lytic KSHV in cells attached to a substratum, with activation only occurring in suprabasal cells. Temporally, KSHV lytic expression occurred between the expression of early and late differentiation markers. Keratinocytes differentiated in suspension culture, which mimics substratum loss that occurs with stratification, activated lytic KSHV. This lytic activation was inhibited by integrin engagement, showing that integrins are a control point for KSHV reactivation. A role for cadherins was not found. Elevated extracellular calcium was necessary, but not sufficient, for lytic activation.

NFAT and CREB regulate Kaposi's sarcoma-associated herpesvirus-induced cyclooxygenase 2 (COX-2)

COX-2 has been implicated in Kaposi's sarcoma-associated herpesvirus (KSHV) latency and pathogenesis (A. George Paul, N. Sharma-Walia, N. Kerur, C. White, and B. Chandran, Cancer Res. 70:3697-3708, 2010; P. P. Naranatt, H. H. Krishnan, S. R. Svojanovsky, C. Bloomer, S. Mathur, and B. Chandran, Cancer Res. 64:72-84, 2004; N. Sharma-Walia, A. G. Paul, V. Bottero, S. Sadagopan, M. V. Veettil, N. Kerur, and B. Chandran, PLoS Pathog. 6:e1000777, 2010; N. Sharma-Walia, H. Raghu, S. Sadagopan, R. Sivakumar, M. V. Veettil, P. P. Naranatt, M. M. Smith, and B. Chandran, J. Virol. 80:6534-6552, 2006). However, the precise regulatory mechanisms involved in COX-2 induction during KSHV infection have never been explored. Here, we identified cis-acting elements involved in the transcriptional regulation of COX-2 upon KSHV de novo infection. Promoter analysis using human COX-2 promoter deletion and mutation reporter constructs revealed that nuclear factor of activated T cells (NFAT) and the cyclic AMP (cAMP) response element (CRE) modulate KSHV-mediated transcriptional regulation of COX-2. Along with multiple KSHV-induced signaling pathways, infection-induced prostaglandin E(2) (PGE(2)) also augmented COX-2 transcription. Infection of endothelial cells markedly induced COX-2 expression via a cyclosporine A-sensitive, calcineurin/NFAT-dependent pathway. KSHV infection increased intracellular cAMP levels and activated protein kinase A (PKA), which phosphorylated the CRE-binding protein (CREB) at serine 133, which probably led to interaction with CRE in the COX-2 promoter, thereby enhancing COX-2 transcription. PKA selective inhibitor H-89 pretreatment strongly inhibited CREB serine 133, indicating the involvement of a cAMP-PKA-CREB-CRE loop in COX-2 transcriptional regulation. In contrast to phosphatidylinositol 3-kinase and protein kinase C, inhibition of FAK and Src effectively reduced KSHV infection-induced COX-2 transcription and protein levels. Collectively, our study indicates that mediation of COX-2 transcription upon KSHV infection is a paradigm of a complex regulatory milieu involving the interplay of multiple signal cascades and transcription factors. Intervention at each step of COX-2/PGE(2) induction can be used as a potential therapeutic target to treat KSHV-associated neoplasm and control inflammatory sequels of KSHV infection.

Viral latency and its regulation: lessons from the gamma-herpesviruses

Latency is a state of cryptic viral infection associated with genomic persistence and highly restricted gene expression. Its hallmark is reversibility: under appropriate circumstances, expression of the entire viral genome can be induced, resulting in the production of infectious progeny. Among the small number of virus families capable of authentic latency, the herpesviruses stand out for their ability to produce such infections in every infected individual and for being completely dependent upon latency as a mode of persistence. Here, we review the molecular basis of latency, with special attention to the gamma-herpesviruses, in which the understanding of this process is most advanced.

Low prevalence of varicella zoster virus and herpes simplex virus type 2 in saliva from human immunodeficiency virus-infected persons in the era of highly active antiretroviral therapy

OBJECTIVES

Human herpesviruses, e.g., herpes simplex virus (HSV) type 1, Epstein-Barr virus, and cytomegalovirus, appear in saliva at greater frequency in persons infected with human immunodeficiency virus (HIV) than in healthy individuals. However, it is not known if varicella zoster virus (VZV) and HSV-2 appear simultaneously during HIV infection at greater frequency in saliva in this era of highly active antiretroviral therapy (HAART). The aim of this study was to investigate the prevalence and amounts of VZV and HSV-2 in the saliva of HIV-infected orally asymptomatic patients.

STUDY DESIGN

Quantitative polymerase chain reaction was used to investigate the prevalence, quantity, risk, and correlations of salivary VZV and HSV-2 from 59 HIV-seropositive individuals and 53 healthy control subjects in a case-control cross-sectional study. Seventy-eight percent of the HIV-seropositive patients (46 out of 59) were taking HAART.

RESULTS

VZV DNA was detected in the saliva of 5.1% (3 out of 59) of the HIV-positive group and in only 1 healthy control 1.9% (1 out of 53; P = .62). The amount of VZV DNA in the expressors was low, generally <1,100 copies/mL, with no observed difference between the HIV-positive group and the control subjects (P = 1.0). HSV-2 DNA was not detected in either group. In the HIV-infected group, VZV shedding occurred in those on HAART, but was not associated with oral lesions, specific CD4(+) or CD8(+) T-cell levels, or demographic factors.

CONCLUSIONS

Varicella zoster virus was detected at low prevalence in the saliva of HIV-infected persons, whereas HSV-2 was not detected in the saliva of this cohort. HAART does not appear to diminish the risk for asymptomatic VZV shedding.

The ORF59 DNA polymerase processivity factor homologs of Old World primate RV2 rhadinoviruses are highly conserved nuclear antigens expressed in differentiated epithelium in infected macaques

Background

ORF59 DNA polymerase processivity factor of the human rhadinovirus, Kaposi's sarcoma-associated herpesvirus (KSHV), is required for efficient copying of the genome during virus replication. KSHV ORF59 is antigenic in the infected host and is used as a marker for virus activation and replication.

Results

We cloned, sequenced and expressed the genes encoding related ORF59 proteins from the RV1 rhadinovirus homologs of KSHV from chimpanzee (PtrRV1) and three species of macaques (RFHVMm, RFHVMn and RFHVMf), and have compared them with ORF59 proteins obtained from members of the more distantly-related RV2 rhadinovirus lineage infecting the same non-human primate species (PtrRV2, RRV, MneRV2, and MfaRV2, respectively). We found that ORF59 homologs of the RV1 and RV2 Old World primate rhadinoviruses are highly conserved with distinct phylogenetic clustering of the two rhadinovirus lineages. RV1 and RV2 ORF59 C-terminal domains exhibit a strong lineage-specific conservation. Rabbit antiserum was developed against a C-terminal polypeptide that is highly conserved between the macaque RV2 ORF59 sequences. This anti-serum showed strong reactivity towards ORF59 encoded by the macaque RV2 rhadinoviruses, RRV (rhesus) and MneRV2 (pig-tail), with no cross reaction to human or macaque RV1 ORF59 proteins. Using this antiserum and RT-qPCR, we determined that RRV ORF59 is expressed early after permissive infection of both rhesus primary fetal fibroblasts and African green monkey kidney epithelial cells (Vero) in vitro. RRV- and MneRV2-infected foci showed strong nuclear expression of ORF59 that correlated with production of infectious progeny virus. Immunohistochemical studies of an MneRV2-infected macaque revealed strong nuclear expression of ORF59 in infected cells within the differentiating layer of epidermis corroborating previous observations that differentiated epithelial cells are permissive for replication of KSHV-like rhadinoviruses.

Conclusion

The ORF59 DNA polymerase processivity factor homologs of the Old World primate RV1 and RV2 rhadinovirus lineages are phylogenetically distinct yet demonstrate similar expression and localization characteristics that correlate with their use as lineage-specific markers for permissive infection and virus replication. These studies will aid in the characterization of virus activation from latency to the replicative state, an important step for understanding the biology and transmission of rhadinoviruses, such as KSHV.