Gammaherpesvirus Research Articles

Models of Virus-Induced Carcinogenesis and Oncolytic Viruses.

Avariety of infectious agents have been linked to cancer. Viruses, bacteria, and parasites have been linked to tumors in animals and humans. Viruses associated with cancer formation cause alteration of physiologic control of cell growth and proliferation or may increase the susceptibility of the host to other cancer risk factors such as environmental toxins. The study of virus–cell interactions has provided fundamental knowledge of cell biology and cell transformation. Viruses associated with cancer and model systems to study these mechanisms have established basic paradigms for virus–cell interactions and contributed greatly to the understanding of diseases associated with biomedically important viruses. More recently, some viruses, the so-called oncolytic viruses, have been used as agents against cancer. This background was the motivation and rationale for dedicating an entire issue of the ILAR Journal to models of virus-induced carcinogenesis and oncolytic viruses. The discovery of feline immunodeficiency virus (FIV) as a naturally occurring retrovirus, first in domestic cats and later in nondomestic feline species, allowed the comparative study of this lentivirus as a model of HIV-1 infection and disease. The ability to study the natural infection in feline species, which exhibit immune regulation similar to humans, has established this animal model as an important system to test hypotheses related to lentivirus disruption of immune control and subsequent pathologic outcomes. Sharing similar rates of neoplasia associated with both FIV and HIV infections, the comparative study of these viruses allow parallel studies to understand underlying factors that account for how lentivirusesmaypromote cancer formation. The review by Kaye and colleagues (2016) provides insights into current evidence on how FIV may promote the development of lymphoma in infected cats and the role of co-infections by other natural pathogens in tumor induction. Among these co-infections, the authors explore the role of feline gamma-herpes virus as a contributing factor to disease in infected cats and in retrovirus latency. The authors detail in their article the need for further evaluation of unique genetic elements of these viral pathogens and the influence of co-infections in disease outcomes. In addition, the authors discuss unique opportunities to use naturally infected animal populations from geographically disperse regions to test hypotheses around lentivirus-associated carcinogenesis. One of the earliest viruses associated with cancer was mouse mammary tumor virus (MMTV), which has served as a model of retroviral transmission and in investigations seeking to understand how the antiviral immune response influences the incidence of cancer. The review in this issue by Dudley and colleagues (2016) outlines some of the lessons learned from MMTV. It includes recent studies that have determined the interplay between key target cells and the immune system that characterizes the infection and pathogenic outcomes. Unique mechanisms of immune evasion are used by MMTV to allow for viral transmission and ultimately cellular oncogene expression. This model system has provided fundamental knowledge of how oncogenes disrupt cellular growth and continues to shed light on how retroviruses evade immune elimination. Also, in this issue, rodentmodels to evaluate oncolytic viruses as therapeutic agents are reviewed by Speranza and colleagues (2016). The use of viruses as anticancer agents has been evaluated in clinical trials in humans for more than 20 years and oncolytic viruses have emerged as viable therapeutic agents over the past decade. This review compares the range of viruses used as therapeutic agents and the evidence for those that are most promising. The review illustrates rodentmodels used to evaluate the preclinical efficacy of oncolytic viruses in context to the intrinsic ways these agents target cancer cells and achieve antitumor effects. The recent documentation of a successful phase III

The Differentiation and Protective Function of Cytolytic CD4 T Cells in Influenza Infection.

CD4 T cells that recognize peptide antigen in the context of class II MHC can differentiate into various subsets that are characterized by their helper functions. However, increasing evidence indicates that CD4 cells with direct cytolytic activity (CD4 CTL) play a role in chronic as well as acute infections, such as influenza A virus (IAV) infection. In the last couple of decades, techniques to measure the frequency and activity of these cytolytic cells has demonstrated their abundance in infections, such as human immunodeficiency virus, mouse pox, murine gamma herpes virus, cytomegalovirus, Epstein–Barr virus, and influenza among others. We now appreciate a greater role for CD4 CTL as direct effectors in viral infections and antitumor immunity through their ability to acquire perforin-mediated cytolytic activity and contribution to lysis of virally infected targets or tumors. As early as the 1980s, CD4 T cell clones with cytolytic potential were identified after influenza virus infection, yet much of this early work was dependent on in vitro culture and little was known about the physiological relevance of CD4 CTL. Here, we discuss the direct role CD4 CTL play in protection against lethal IAV infection and the factors that drive the generation of perforin-mediated lytic activity in CD4 cells in vivo during IAV infection. While focusing on CD4 CTL generated during IAV infection, we pull comparisons from the literature in other antiviral and antitumor systems. Further, we highlight what is currently known about CD4 CTL secondary and memory responses, as well as vaccination strategies to induce these potent killer cells that provide an extra layer of cell-mediated immune protection against heterosubtypic IAV infection.

An EBV recombinant deleted for residues 130-159 in EBNA3C can deregulate p53/Mdm2 and Cyclin D1/CDK6 which results in apoptosis and reduced cell proliferation.

Epstein-Barr virus (EBV), a gamma herpes virus is associated with B-cell malignancies. EBNA-3C is critical for in vitro primary B-cell transformation. Interestingly, the N terminal domain of EBNA3C which contains residues 130–159, interacts with various cellular proteins, such as p53, Mdm2, CyclinD1/Cdk6 complex, and E2F1. In the current reverse genetics study, we deleted the residues 130-159 aa within EBNA3C open reading frame (ORF) by BACmid recombinant engineering methodology. Our experiments demonstrated that deletion of the 130-159 aa showed a reduction in cell proliferation. Also, this recombinant virus showed with higher infectivity of human peripheral blood mononuclear cells (PBMCs) compared to wild type EBV. PBMCs- infected with recombinant EBV deleted for 130-159 residues have differential expression patterns for the p53/Mdm2, CyclinD1/Cdk6 and pRb/E2F1 pathways compared to wild type EBV-infected PBMCs. PBMCs infected with recombinant virus showed increased apoptotic cell death which further resulted in activation of polymerase 1 (PARP1), an important contributor to apoptotic signaling. Interestingly, cells infected with this recombinant virus showed a dramatic decrease in chromosomal instability, indicated by the presence of increased multinucleation and micronucleation. In addition infection with recombinant virus have increased cells in G0/G1 phase and decreased cells in S-G2M phase when compared to wild type infected cells. Thus, these differences in signaling activities due to 29 amino acid residues of EBNA3C is of particular significance in deregulation of cell proliferation in EBV-infected cells.

Abstract B095: Targeting Epstein-Barr virus transformed B lymphoblastoid cells using antibodies with T cell receptor-like specificities

Abstract Introduction: Epstein-Barr virus (EBV) is a gamma herpesvirus that is found in the majority of the human population. Though commonly established as a life-long, asymptomatic infection, EBV has also been implicated in a number of human malignancies including Hodgkin's and Burkitt's lymphomas, nasopharyngeal carcinoma as well as post-transplant lymphoproliferative disease in immunosuppressed patients. While EBV displays restricted gene expression during different latency programs, the viral gene products that are frequently detected in EBV-associated tumors include Epstein-Barr virus Nuclear Antigen 1 (EBNA1), Latent Membrane Protein 1 (LMP1) and Latent Membrane Protein 2A (LMP2A). Our lab has previously described the generation and characterization of monoclonal antibodies with T cell receptor-like specificities (TCR-like mAbs) targeting EBV latent epitopes in association with HLA-A0201. These antibodies have been shown to bind to their targets with high specificities and affinities, and were capable of recognizing antigens displayed on human nasopharyngeal carcinoma biopsies, highlighting their immunotherapeutic potential for targeting EBV-associated tumors. Methods: EBV is particularly capable of transforming resting B cells into latently infected, actively proliferating B lymphoblastoid cell lines (BLCL) in vitro. As a proof-of-concept, we first generated EBV BLCLs from HLA-A0201+ human peripheral blood mononuclear cells (PBMCs) and compared the ability of our TCR-like mAbs to detect their endogenous targets before and after establishment of the cell lines. The xenograft model involving the inoculation of EBV BLCL into immunodeficient mice resembles B cell lymphoma that develops in post-transplant, immunosuppressed patients. Hence to test the ability of our TCR-like mAbs to target the BLCLs in vivo, we next inoculated PBMC-derived BLCLs into immunodeficient NSG mice and administered weekly dosage of TCR-like mAbs. Mice were assessed for changes in weight, survival as well as end-point organs analysis. Results: Here, we showed that endogenous EBV latent epitopes could be detected by our TCR-like mAbs on PBMC-derived BLCLs after EBV establishment of the cell line. Despite the inherent heterogeneities between different donors PBMC-derived BLCLs, several of the HLA-A0201+ BLCLs tested displayed similar binding activities with these TCR-like mAbs. In addition, BLCL-injected NSG mice that received weekly treatment of TCR-like mAbs displayed reduced tumor burden, splenomegaly and liver tumor spots in comparison to mice that received isotype antibody or PBS control. Importantly, BLCL-injected NSG mice that received the TCR-like mAb targeting the EBNA1 latent epitope exhibited delayed weight loss and survival advantage. Conclusion: We have utilized TCR-like mAbs with specificities against EBV latent epitopes expressed on HLA-A0201 and showed that these antibodies could recognize endogenous targets on EBV transformed, PBMC-derived BLCLs. Furthermore, weekly administration of TCR-like mAbs into BLCL xenograft NSG mice resulted in an overall reduction of tumor load and improved survival in one of the three described antibodies. Taken together, our data provide preliminary evidence for the therapeutic usage of antibodies with TCR-like specificities for the targeting EBV transformed BLCL in vivo. Citation Format: Junyun Lai, Wei Jian Tan, Chien Tei Too, Nalini Srinivasan, Lan Hiong Wong, Fatimah Mustafa, Soh Ha Chan, Jianzhu Chen, Paul Anthony MacAry. Targeting Epstein-Barr virus transformed B lymphoblastoid cells using antibodies with T cell receptor-like specificities. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B095.

Cross-Reactivity of Neutralizing Antibodies among Malignant Catarrhal Fever Viruses

Some members of the gamma herpesvirus genus Macavirus are maintained in nature as subclinical infections in well-adapted ungulate hosts. Transmission of these viruses to poorly adapted hosts, such as American bison and cattle, can result in the frequently fatal disease malignant catarrhal fever (MCF). Based on phylogenetic analysis, the MCF viruses (MCFV) cluster into two subgroups corresponding to the reservoir hosts’ subfamilies: Alcelaphinae/Hippotraginae and Caprinae. Antibody cross-reactivity among MCFVs has been demonstrated using techniques such as enzyme linked immunosorbent and immunofluorescence assays. However, minimal information is available as to whether virus neutralizing antibodies generated against one MCFV cross react with other members of the genus. This study tested the neutralizing activity of serum and plasma from select MCFV-infected reservoir hosts against alcelaphine herpesvirus 1 (AlHV-1) and ovine herpesvirus 2 (OvHV-2). Neutralizing antibody activity against AlHV-1 was detected in samples from infected hosts in the Alcelaphinae and Hippotraginae subfamilies, but not from hosts in the Caprinae subfamily. OvHV-2 neutralizing activity was demonstrated in samples from goats (Caprinae) but not from wildebeest (Alcelaphinae). These results show that neutralizing antibody cross reactivity is present to MCFVs within a virus subgroup but not between subgroups. This information is important for diagnosing infection with MCFVs and in the development of vaccines against MCF.

Viruses in Idiopathic Pulmonary Fibrosis. Etiology and Exacerbation.

Viral infections are important contributors to exacerbation of asthma and chronic obstructive pulmonary disease; however, the role of viruses in the pathogenesis of idiopathic pulmonary fibrosis (IPF) is less clear. This likely reflects that fact that IPF acute exacerbations are defined clinically as "noninfectious," and little attention has been paid to the outcomes of patients with IPF with diagnosed infections. However, accumulating evidence suggests that infections (both bacterial and viral) may influence disease outcomes either as exacerbating agents or initiators of disease. Support for a viral role in disease initiation comes from studies demonstrating the presence of herpesviral DNA and epithelial cell stress in the lungs of asymptomatic relatives at risk for developing familial IPF. In addition, the number of studies that can associate viral (especially herpesviral) signatures in the lung with the development of IPF is steadily growing, and activated leukocyte signatures in patients with IPF provide further support for infectious processes driving IPF progression. Animal modeling has been used to better understand how a gamma herpesvirus infection can modulate the pathogenesis of lung fibrosis and has demonstrated that preceding infections appear to reprogram lung epithelial cells during latency to produce profibrotic factors, making the lung more susceptible to subsequent fibrotic insult, whereas exacerbations of existing fibrosis, or infections in susceptible hosts, involve active viral replication and are influenced by antiviral therapy. In addition, there is new evidence that bacterial burden in the lungs of patients with IPF may predict a poor prognosis.

A Conserved Gammaherpesvirus Cyclin Specifically Bypasses Host p18(INK4c) To Promote Reactivation from Latency.

Gammaherpesviruses (GHVs) carry homologs of cellular genes, including those encoding a viral cyclin that promotes reactivation from latent infection. The viral cyclin has reduced sensitivity to host cyclin-dependent kinase inhibitors in vitro; however, the in vivo significance of this is unclear. Here, we tested the genetic requirement for the viral cyclin in mice that lack the host inhibitors p27(Kip1) and p18(INK4c), two cyclin-dependent kinase inhibitors known to be important in regulating B cell proliferation and differentiation. While the viral cyclin was essential for reactivation in wild-type mice, strikingly, it was dispensable for reactivation in mice lacking p27(Kip1) and p18(INK4c). Further analysis revealed that genetic ablation of only p18(INK4c) alleviated the requirement for the viral cyclin for reactivation from latency. p18(INK4c) regulated reactivation in a dose-dependent manner so that the viral cyclin was dispensable in p18(INK4c) heterozygous mice. Finally, treatment of wild-type cells with the cytokine BAFF, a known attenuator of p18(INK4c) function in B lymphocytes, was also able to bypass the requirement for the viral cyclin in reactivation. These data show that the gammaherpesvirus viral cyclin functions specifically to bypass the cyclin-dependent kinase inhibitor p18(INK4c), revealing an unanticipated specificity between a GHV cyclin and a single cyclin-dependent kinase inhibitor. The gammaherpesviruses (GHVs) cause lifelong infection and can cause chronic inflammatory diseases and cancer, especially in immunosuppressed individuals. Many GHVs encode a conserved viral cyclin that is required for infection and disease. While a common property of the viral cyclins is that they resist inhibition by normal cellular mechanisms, it remains unclear how important it is that the GHVs resist this inhibition. We used a mouse GHV that either contained or lacked a viral cyclin to test whether the viral cyclin lost importance when these inhibitory pathways were removed. These studies revealed that the viral cyclin was required for optimal function in normal mice but that it was no longer required following removal or reduced function of a single cellular inhibitor. These data define a very specific role for the viral cyclin in bypassing one cellular inhibitor and point to new methods to intervene with viral cyclins.

Dissecting the contribution of EBNA3C domains important for EBV-induced B-cell growth and proliferation.

Epstein-Barr virus (EBV) is an oncogenic gammaherpes virus which is linked to pathogenesis of several human lymphatic malignancies. The EBV essential latent antigen EBNA3C is critical for efficient conversion of primary human B-lymphocytes to lymphoblastic cell lines and for continued LCL growth. EBNA3C, an EBV latent antigen with oncogenic potential can bind and regulate the functions of a wide range of cellular transcription factors. In our current reverse genetics study, we deleted the full length EBNA3C, and independently the RBP-Jκ and Nm23-H1 binding sites within EBNA3C using BACmid recombinant engineering methodology. Our experiments demonstrated that deletion of the EBV EBNA3C open reading frame (ORF) and more specifically the residues 621-675 which binds Nm23H1 and SUMO-1 showed a significant reduction in the ability of the cells to proliferate. Furthermore, they exhibited lower infectivity of human peripheral blood mononuclear cells (PBMCs). We also showed that recombinant EBV with deletions of the EBNA3C ORF, as well as a recombinant with residues 621-675 within EBNA3C ORF deleted had diminished abilities to activate CD40. Our study also revealed that the full length (1-992) and 621-675 aa deletions of EBNA3C when compared to wild type EBV infected PBMCs had differential expression patterns for the phosphorylation of MAP kinases specifically p38, JNK and ERK. Regulation of β-catenin also differed among wild type and EBNA3C deleted mutants. These temporal differences in signaling activities of these recombinant viruses in PBMCs is likely important in defining their functional importance in EBV-mediated B-cell transformation.

Identification of Novel Gammaherpesviruses in Ocelots (Leopardus pardalis) and Bobcats (Lynx rufus) in Panama and Colorado, USA.

Gammaherpesviruses (GHVs) have been identified in many species and are often associated with disease. Recently, we characterized three novel felid GHVs in domestic cats (Felis catus), bobcats (Lynx rufus), and pumas (Puma concolor). We investigated whether free-ranging ocelots (Leopardus pardalis) and bobcats are infected with additional GHVs. We screened DNA samples from ocelots on Barro Colorado Island, Panama, and bobcats in western Colorado, US, by using a degenerate nested PCR that targets the GHV glycoprotein B gene. We identified a novel GHV glycoprotein B sequence in two ocelots and a second novel sequence in a bobcat, which is distinct from the previously characterized bobcat GHV (Lynx rufus GHV 1). Utilizing additional degenerate and virus-specific PCRs, we extended these sequences to include 3.4 kilobases of the GHV glycoprotein B and DNA polymerase genes. These sequences identify the first GHV detected in ocelots and the second GHV in bobcats. These viruses were provisionally named L. pardalis GHV 1 and Lynx rufus GHV 2, respectively. The viruses are most closely related to recently identified GHVs of the Percavirus genus found in domestic cats (F. catus GHV 1) and bobcats (L. rufus GHV 1), suggesting that a cluster of felid GHVs exists within the Percavirus genus.

Recombinant Murine Gamma Herpesvirus 68 Carrying KSHV G Protein-Coupled Receptor Induces Angiogenic Lesions in Mice

Human gamma herpesviruses, including Kaposi’s sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV), are capable of inducing tumors, particularly in in immune-compromised individuals. Due to the stringent host tropism, rodents are resistant to infection by human gamma herpesviruses, creating a significant barrier for the in vivo study of viral genes that contribute to tumorigenesis. The closely-related murine gamma herpesvirus 68 (γHV68) efficiently infects laboratory mouse strains and establishes robust persistent infection without causing apparent disease. Here, we report that a recombinant γHV68 carrying the KSHV G protein-coupled receptor (kGPCR) in place of its murine counterpart induces angiogenic tumors in infected mice. Although viral GPCRs are conserved in all gamma herpesviruses, kGPCR potently activated downstream signaling and induced tumor formation in nude mouse, whereas γHV68 GPCR failed to do so. Recombinant γHV68 carrying kGPCR demonstrated more robust lytic replication ex vivo than wild-type γHV68, although both viruses underwent similar acute and latent infection in vivo. Infection of immunosuppressed mice with γHV68 carrying kGPCR, but not wild-type γHV68, induced tumors in mice that exhibited angiogenic and inflammatory features shared with human Kaposi’s sarcoma. Immunohistochemistry staining identified abundant latently-infected cells and a small number of cells supporting lytic replication in tumor tissue. Thus, mouse infection with a recombinant γHV68 carrying kGPCR provides a useful small animal model for tumorigenesis induced by a human gamma herpesvirus gene in the setting of a natural course of infection.

Viral load of equine herpesviruses 2 and 5 in nasal swabs of actively racing Standardbred trotters: Temporal relationship of shedding to clinical findings and poor performance

The equine gamma herpesviruses 2 and 5 (EHV-2 and -5) have frequently been observed in the equine population and until recently presumed low to nonpathogenic. However, recent reports linking presence of equine gamma herpesviruses with clinical signs of mild to severe lung disease, suggest that the role of these viruses in respiratory disease and poor performance syndrome is still unclear. Moreover, baseline data regarding the temporal pattern of shedding of EHV-2 and EHV-5 within stables and within individual actively racing horses have been lacking. In a prospective longitudinal study, we followed elite racing Standardbred trotters at monthly intervals for 13 months, to investigate whether the amount of EHV-2 and EHV-5 shedded in nasal secretions varied over time within and between individual horses. Sixty-six elite horses were investigated by analyzing nasal swabs and serum samples, a health check and evaluation of athletic performance monthly during the study period. Nasal swabs were analyzed with two newly developed qPCR assays for EHV-2 and EHV-5, respectively. Of 663 samples, 197 (30%) were positive for EHV-2 and 492 (74%) positive for EHV-5. Furthermore, 176 (27%) of the samples were positive for both EHV-2 and EHV-5 simultaneously. There was considerable variation in the amount and frequency of shedding of EHV-2 and EHV-5 within and between individual horses. Viral load varied seasonally, but neither EHV-2 nor EHV-5 viral peaks were associated with clinical respiratory disease and/or poor performance in racing Standardbred trotters.

B-cell-independent lymphoid tissue infection by a B-cell-tropic rhadinovirus.

Lymphocytes provide gammaherpesviruses with a self-renewing substrate for persistent infection and with transport to mucosal sites for host exit. Their role in the initial colonization of new hosts is less clear. Murid herpesvirus 4 (MuHV-4), an experimentally accessible, B-cell-tropic rhadinovirus (gamma-2 herpesvirus), persistently infects both immunocompetent and B-cell-deficient mice. A lack of B-cells did not compromise MuHV-4 entry into lymphoid tissue, which involved myeloid cell infection. However, it impaired infection amplification and MuHV-4 exit from lymphoid tissue, which involved myeloid to B-cell transfer.

Characterization of major histocompatibility complex class I genes and alleles of the California sea lion (Zalophus californianus) in relation to development of sea lion urogenital carcinoma (VET2P.1130)

Abstract Decades of global environmental change have impacted the overall health of many wildlife species, and emerging infectious diseases, biotoxicoses, and cancers are being increasingly recognized. California sea lions have an unusually high incidence of an aggressive, widely metastatic urogenital carcinoma that has affected 26% of the adult animals that died following stranding on the central California coast in the past decade. A gamma herpesvirus, environmental pollutants, major histocompatibility complex (MHC) class II alleles, and a variant of a heparanase gene have all been implicated in the multifactorial cause. The locus most commonly associated with immunogenetic susceptibility to neoplastic transformation and viral infections, MHC class I, has not been studied, however. Genomic DNA was extracted from skin samples of 20 cancer-positive and 40 cancer-negative sea lions. Using these samples, the MHC I gene sequence will be published, the MHC class I polymorphism will be assessed, and the association of specific MHC class I alleles with cancer-positive and cancer-negative sea lions will be determined. We hypothesize that particular MHC class I alleles that successfully present immunodominant peptides of the otarine herpesvirus-1 will be present in cancer-negative animals but not cancer-positive animals and that there will be increased homozygosity of MHC alleles in sea lions with carcinomas as compared to those without.

EAE symptoms are enhanced by gammaherpesvirus latenlty infetected memory B cells (VIR1P.1143)

Abstract While the description of the genetic and environmental factors responsible for the onset of Multiple Sclerosis has remained elusive, it is believed that previous infection with Epstein Barr Virus (EBV) plays an important role in the development of MS. Our lab has hypothesized that latent EBV infection alters the immune system’s response in genetically predisposed individuals, thereby exacerbating autoimmunity. The study of this relationship is difficult, however, since EBV only infects humans. To address this question we previously developed a murine model where latent infection with gamma herpesvirus 68 (γHV-68), the murine homolog to EBV, enhances the symptoms of experimental autoimmune encephalomyelitis (EAE), which closely resembles human MS pathogenesis. These enhanced symptoms are driven by the upregulati/on of CD40 on dendritic cells in latently infected mice, which drives the priming of a strong Th1 response as well as a decrease in Treg frequencies. Latency of γHV-68 mainly occurs in memory B cells. Here, we demonstrate that latently infected memory B cells are capable of enhancing EAE symptoms when transferred from mice latently infected with γHV-68 into uninfected mice. To understand the impact of γHV-68 on B cells, we propose a mechanism where type 1 interferons play an important role in skewing a Th1 response in latently infected mice. This is a novel mechanism that describes how EBV latency can spur the onset of MS and potentially other autoimmune diseases.

Epstein-Barr virus transcription factor Zta acts through distal regulatory elements to directly control cellular gene expression.

Lytic replication of the human gamma herpes virus Epstein-Barr virus (EBV) is an essential prerequisite for the spread of the virus. Differential regulation of a limited number of cellular genes has been reported in B-cells during the viral lytic replication cycle. We asked whether a viral bZIP transcription factor, Zta (BZLF1, ZEBRA, EB1), drives some of these changes. Using genome-wide chromatin immunoprecipitation coupled to next-generation DNA sequencing (ChIP-seq) we established a map of Zta interactions across the human genome. Using sensitive transcriptome analyses we identified 2263 cellular genes whose expression is significantly changed during the EBV lytic replication cycle. Zta binds 278 of the regulated genes and the distribution of binding sites shows that Zta binds mostly to sites that are distal to transcription start sites. This differs from the prevailing view that Zta activates viral genes by binding exclusively at promoter elements. We show that a synthetic Zta binding element confers Zta regulation at a distance and that distal Zta binding sites from cellular genes can confer Zta-mediated regulation on a heterologous promoter. This leads us to propose that Zta directly reprograms the expression of cellular genes through distal elements.

Association between malaria exposure and Kaposi's sarcoma-associated herpes virus seropositivity in Uganda.

ObjectiveUnlike other herpes viruses, Kaposi's sarcoma-associated herpes virus (KSHV) is not ubiquitous worldwide and is most prevalent in sub-Saharan Africa. The reasons for this are unclear. As part of a wider investigation of factors that facilitate transmission in Uganda, a high prevalence country, we examined the association between antimalaria antibodies and seropositivity against KSHV.MethodsAntibodies against P. falciparum merozoite surface protein (PfMSP)-1, P. falciparum apical membrane antigen (PfAMA)-1 and KSHV antigens (ORF73 and K8.1) were measured in samples from 1164 mothers and 1227 children.ResultsKaposi's sarcoma-associated herpes virus seroprevalence was 69% among mothers and 15% children. Among mothers, KSHV seroprevalence increased with malaria antibody titres: from 60% to 82% and from 54% to 77%, comparing those with the lowest and highest titres for PfMSP-1 and PfAMA-1, respectively (P < 0.0001). Among children, only antibodies to PfAMA-1 were significantly associated with KSHV seropositivity, (P < 0.0001). In both mothers and children, anti-ORF73 antibodies were more strongly associated with malaria antibodies than anti-K8.1 antibodies.ConclusionThe association between malaria exposure and KSHV seropositivity suggests that malaria is a cofactor for KSHV infection or reactivation.

Chromatinization of the KSHV Genome During the KSHV Life Cycle.

Kaposi’s sarcoma-associated herpesvirus (KSHV) belongs to the gamma herpesvirus family and is the causative agent of various lymphoproliferative diseases in humans. KSHV, like other herpesviruses, establishes life-long latent infection with the expression of a limited number of viral genes. Expression of these genes is tightly regulated by both the viral and cellular factors. Recent advancements in identifying the expression profiles of viral transcripts, using tilling arrays and next generation sequencing have identified additional coding and non-coding transcripts in the KSHV genome. Determining the functions of these transcripts will provide a better understanding of the mechanisms utilized by KSHV in altering cellular pathways involved in promoting cell growth and tumorigenesis. Replication of the viral genome is critical in maintaining the existing copies of the viral episomes during both latent and lytic phases of the viral life cycle. The replication of the viral episome is facilitated by viral components responsible for recruiting chromatin modifying enzymes and replication factors for altering the chromatin complexity and replication initiation functions, respectively. Importantly, chromatin modification of the viral genome plays a crucial role in determining whether the viral genome will persist as latent episome or undergo lytic reactivation. Additionally, chromatinization of the incoming virion DNA, which lacks chromatin structure, in the target cells during primary infection, helps in establishing latent infection. Here, we discuss the recent advancements on our understating of KSHV genome chromatinization and the consequences of chromatin modifications on viral life cycle.

Interference with the Autophagic Process as a Viral Strategy to Escape from the Immune Control: Lesson from Gamma Herpesviruses.

We summarized the most recent findings on the role of autophagy in antiviral immune response. We described how viruses have developed strategies to subvert the autophagic process. A particular attention has been given to Epstein-Barr and Kaposi's sarcoma associated Herpesvirus, viruses studied for many years in our laboratory. These two viruses belong to γ-Herpesvirus subfamily and are associated with several human cancers. Besides the effects on the immune response, we have described how autophagy subversion by viruses may also concur to the enhancement of their replication and to viral tumorigenesis.

Immune evasion strategies of molluscum contagiosum virus.

Molluscum contagiosum virus (MCV) is the causative agent of molluscum contagiosum (MC), the third most common viral skin infection in children, and one of the five most prevalent skin diseases worldwide. No FDA-approved treatments, vaccines, or commercially available rapid diagnostics for MCV are available. This review discusses several aspects of this medically important virus including: physical properties of MCV, MCV pathogenesis, MCV replication, and immune responses to MCV infection. Sequencing of the MCV genome revealed novel immune evasion molecules which are highlighted here. Special attention is given to the MCV MC159 and MC160 proteins. These proteins are FLIPs with homologs in gamma herpesviruses and in the cell. They are of great interest because each protein regulates apoptosis, NF-κB, and IRF3. However, the mechanism that each protein uses to impart its effects is different. It is important to elucidate how MCV inhibits immune responses; this knowledge contributes to our understanding of viral pathogenesis and also provides new insights into how the immune system neutralizes virus infections.

Determination of Optimal Target Antigen and Immune Modulatory Approaches to Improve and Standardize Epstein-Barr Virus-Specific Adoptive T Cell Therapy

Epstein-Barr Virus (EBV) is a ubiquitous gamma herpesvirus that infects lymphocytes and epithelial cells, establishing lifelong latency. Immunosuppression is associated with a transition from a quiescent, latent EBV infection to either a lytic or active latent life cycle, which involves transformation of memory B cells to rapidly growing lymphoblastoid cell lines (LCLs). Due to the immunogenicity of EBV viral proteins, cells expressing most latent or lytic peptides are eradicated through immune surveillance mechanisms. EBV-associated lymphoproliferative disorders (LPDs) arise in immunocompromised individuals and are facilitated by the expression of the same viral proteins that are expressed in the immune tolerant environment. Furthermore, EBV-LPDs acquire various mechanisms to suppress immune function, such as expression of the programmed death ligand (PD-L1), CTLA-4, amino acid depletion, and propagation of suppressive immune cell subsets, including tumor-associated macrophages (TAMs) that attenuate T cell receptor signaling and cytokine production. These immunosuppressive mechanisms increase the risk of acquiring EBV viremia and can facilitate the development of LPDs. In other work reported by our group (Patton et al, ASH abstract 2014), a TAM-like population has recently been discovered to spontaneously expand in peripheral blood mononuclear cell (PBMC)/LCL co-cultures. These TAM-like macrophages are capable of potent cytotoxicity against EBV-specific T cells, thus novel strategies to counteract this negative regulatory network are needed.One effective strategy developed to reestablish EBV-specific immunity is adoptive T cell therapy. However, the optimal combination of target antigens required to protect against EBV-LPD is not well characterized. It remains plausible that expansion of cytotoxic and/or helper T cell populations specific for multiple EBV antigens will improve the efficiency of the T cell response. The suppression of negative immune regulators may further enhance the effectiveness of the adoptive therapies to provide optimal control of viremia and effectively treat EBV-driven malignancies.Here, we generated EBV-specific T cell preparations by culturing PBMCs supplemented with interleukins 4 and 7 (IL4, IL7) in the presence of latent (EBNA1, EBNA3, LMP1, LMP2) or lytic (BZLF1, BRLF, BMLF1, BMRF1) PepMixes (complete protein-spanning pools of overlapping peptides). Cells were separated into two groups, a test and expansion group, to determine optimal ex vivo expansion. Activity of T cells was measured by direct flow-based cytotoxicity against LCL targets and interferon gamma (IFNγ) production via Enzyme-Linked Immuno Spot (ELISpot).Preliminary ELISpot assays from two donors in the test group showed that BZLF1-specific T cells produced as much as 34-fold more IFNγ in comparison to other EBV antigens (standardized to a negative control). T cells produced in culture with a peptivator PepMix, a collection of 13 latent and lytic peptide pools, on average exhibited the second highest levels of IFNγ release, expressing as much as 1.4-fold more IFNγ than the next highest antigen-specific response, depending on the donor. Additionally, LMP1 produced as much as 24-fold higher levels of IFNγ. Therefore, given the heterogeneous EBV viral gene expression profiles and variation of immune dominance across human leukocyte antigen (HLA) types, use of polyclonal immunogen-specific T cells may be more effective in improving survival and long-term protection from EBV-driven complications via improved memory T cell surveillance. Additional ex vivo work is currently underway examining combinations of lytic and latent antigens based on immunodominance analysis across HLA types. Finally, use of immune modulatory mechanisms to address newly discovered TAM-like populations contributing to reduced immune effector function against EBV-LPD are currently being evaluated. We are testing strategies to promote PD-L1 and CTLA-4 blockade, inhibition of amino acid depletion, and down regulation of regulatory T cells, to allow for enhanced expansion of antigen-specific T cell populations. Confirmation of these hypotheses will be directed toward developing streamlined methods for efficient, rapid, and personalized T cell preparation that can be standardized for translation into clinical trials. DisclosuresNo relevant conflicts of interest to declare.