Keynote & Symposium Speakers

Opening Symposium: Gene and Oncolytic Therapy
Saturday, 29 July, 17:10-17:35

Joseph Glorioso Symposium Speaker
Joseph Glorioso
University of Pittsburgh, United States
HSV Gene Vectors and the Treatment of Chronic Pain
Pain is an adaptive warning for impending tissue damage however chronic pain is a pathological condition that is no longer adaptive and can have severe negative affects on the quality of life. In this US alone, it has been estimated that more 60 million people will experience long lasting painful conditions during their lifetime that limits the ability to work, travel and participate in leisure activities. Chronic pain most often arises as a secondary response to inflammation and nerve damage and is a commonly associated with diseases such cancer, arthritis, radiculopathy, infections and diabetes. For most painful conditions, there is no long-term treatment and the standard of care using pharmacological approaches are ameliorative at best. Moreover, drug therapy is systemically administered and can have highly undesirable side affects. Oxycodone for example has become a dangerous addictive drug. Gene therapy holds promise as a treatment alternative for chronic pain conditions. Viral vectors such as HSV can be used to introduce products that can relieve pain long term. I will describe progress in the engineering of safe, long-term HSV expression vectors for modifying the activity of sensory neurons and strategies to treat chronic pain using natural cellular products and engineered ligand gated ion channels that can be regulated by systemically administered drugs.

Opening Symposium: Gene and Oncolytic Therapy
Saturday, 29 July, 17:35-18:00

Balveen Kaur Symposium Speaker
Balveen Kaur
University of Texas Health Science Center at Houston, United States
Oncolytic HSV-1 Therapy for Cancer
Oncolytic viruses are viruses that are designed to replicate in and lyse tumor cells. While FDA recently approved an oncolytic HSV-1 derived virus for metastatic melanoma, numerous other viruses are being investigated as novel anti-cancer agents. In this presentation, we will discuss recent progress and challenges faced by oncolytic viruses in their battle against tumor eradication.

Opening Symposium: Gene and Oncolytic Therapy
Saturday, 29 July, 18:00-18:25

Christopher Snyder Symposium Speaker
Christopher Snyder
Thomas Jefferson University, United States
Intratumoral infection with cytomegalovirus promotes immune control of melanoma lesions
Cytomegalovirus (CMV) has been explored as a vaccine vector to promote strong CD8+ T cell responses. CMV-driven T cells accumulate over time after infection and migrate into most tissues of the body where they can establish tissue residency. Moreover, tumor-specific T cells stimulated by CMV-based vaccines can be driven into solid tumors. However, CMV-driven T cells are still subject to the intense immune suppression of the tumor microenvironment. Our experiments with murine CMV (MCMV) and the aggressive B16 melanoma model showed that melanoma-specific T cells were markedly dysfunctional in the tumor environment. Surprisingly however, direct intratumoral (IT) infections by MCMV dramatically delayed B16 tumor growth. Therapeutic efficacy was dependent on CD8+ T cells and IT-MCMV infection was associated with improved CD8+ T cell function in the tumor. Moreover, the combination of IT-MCMV and blockade of the inhibitory PD-1 pathway led to tumor clearance in ~60% of animals and resistance to secondary tumor challenge, implying the development of immune memory. Remarkably however, a vaccine strain of MCMV that promoted robust expansion of melanoma-specific T cells was no more effective at delaying tumor growth or synergizing with PD-L1 blockade than the backbone vector, demonstrating that vaccine-driven T cells were not responsible for the therapeutic effect. Although MCMV could infect B16 cells directly, the primary target of MCMV infection in the tumor appeared to be macrophages. MCMV infection of immune-suppressive macrophages skewed them towards a pro-inflammatory phenotype and IT infection by MCMV was associated with a marked increase in the presence of inflammatory macrophages in the tumor. Thus, we propose a model in which MCMV infection shifts the balance of pro- and anti-inflammatory macrophages, thereby enabling improved tumor-specific T cell responses and synergy with immune therapies that enhance T cell function in the tumor.

Keynote: Virus-Cell Interactions: Entry, Assembly and Egress
Sunday, 30 July, 8:30-9:10

William (Bill) Britt Keynote Speaker
William (Bill) Britt
University of Alabama at Birmingham, United States
Cellular Membrane Reorganization and HCMV Assembly
Human cytomegalovirus (HCMV) virion assembly is associated with a characteristic reorganization of membranes in the infected cell including the nuclear membrane and membranes in the secretory and endocytic pathways. Reorganization of cytoplasmic membranes results in the formation of an intracellular compartment that has been termed the (virion) assembly compartment (VAC). The VAC represents a morphologically distinct membranous structure that functions in the assembly of infectious virions. This compartment has been shown to be an intracellular site of virion structural protein accumulation and the membranous site of final virion envelopment. Formation of this membranous compartment initially requires ordered disassembly of existing membrane structures followed by formation of the VAC, a process that parallels membrane disassembly that occurs during mitosis. Similarly, functions of both the secretory and endocytic pathways are regulated during formation of the VAC by HCMV miRNAs that target key cellular components of this pathway, particularly those cellular proteins that function in endosome recycling. By limiting recycling of endocytosed cargo, host membranes and virion proteins can accumulate in the endocytic recycling compartment (ERC), a compartment that overlaps spatially with the VAC. Finally, dynein dependent minus-end microtubule transport is also required for correct positioning of intracellular membranes in the VAC and for trafficking of virion structural proteins to the VAC. Thus, step wise re-programing of cellular membrane structure, location, and function during HCMV infection contribute to VAC formation and efficient infectious virion assembly.

Symposium Session I: Virus-Cell Interactions: Entry, Assembly, and Egress
Sunday, 30 July, 9:10-9:35

Richard Longnecker Symposium Speaker
Richard Longnecker
Northwestern University, United States
Epstein-Barr Virus Entry
Epstein-Barr Virus (EBV) is a causative agent in endemic Burkitt's lymphoma and undifferentiated nasopharyngeal carcinoma (NPC). EBV is also recognized as an important pathogen in immunosuppressed individuals causing a variety of proliferative disorders. These pathologies suggest a fairly wide tissue tropism for EBV in vivo. In vitro and in vivo, cells of epithelial and B cell origin are the cell types that are most susceptible to EBV infection and as a result are the best studied in regard to EBV entry. EBV enters cell by fusion of the virion membrane with the cell membrane either at the cell surface or following endocytosis. B cell fusion requires a complex of viral proteins that includes gB, gH, gL, and gp42. gp42 has been specifically found to bind to human leukocyte antigen (HLA) class II and this interaction is required for EBV entry into B lymphocytes. For epithelial cells, fusion occurs at the cell surface and only gH/gL and gB are required with gH binding to the epithelial receptor. To date, little is known about the overall mechanism that EBV uses to bind and penetrate B cells and in particular how the multiple viral proteins essential in membrane fusion function in EBV entry into B cells and epithelial. Recent studies in the Longnecker, Jardetzky, and Zhou laboratories will presented as well as an entry model of EBV into the target cells.

Symposium Session I: Virus-Cell Interactions: Entry, Assembly, and Egress
Sunday, 30 July, 9:35-10:00

David Johnson Symposium Speaker
David Johnson
Oregon Health & Sciences University, United States
Entry of HCMV into diverse cell types
HCMV entry shares some common features with HSV and EBV entry, although there are also some major differences. HCMV gB is apparently triggered for entry fusion by one of three forms of gH/gL: the pentamer gH/gL/UL128-131, the trimer gH/gL/gO or the dimer gH/gL. The pentamer is not required for entry into human fibroblasts but is required for entry into most other important cel types: epithelial and endothelial cells and macrophages. However, the trimer is required for entry into all cells tested to date. The role of the dimer is not well understood, although we reported that gH/gL can be coprecipitated with gB from extracts of virions and have evidence that gB and gH/gL are disulfide linked. These observations fit with all the models for HSV and EBV entry that propose that gH/gL proteins trigger gB for entry fusion. But for HSV and EBV there has not been good evidence for direct interactions. In collaboration with Ted Jardetsky's laboratory, we are testing the binding of dimer, trimer and pentamer to cells, inhibition of entry into cells and cell-cell fusion with soluble forms of gH/gL proteins. Soluble pentamer can block entry into epithelial cells and expression of full-length pentamer interferes with this entry, supporting the notion that pentamer binds saturable receptors. We identified a cellular molecule CD147 that increases HCMV entry into cells but only when viruses express pentamers. As such CD147 is the only pentamer-specific HCMV entry mediator described to date.

Symposium Session I: Virus-Cell Interactions: Entry, Assembly, and Egress
Sunday, 30 July, 10:00-10:25

Colin Crump Symposium Speaker
Colin Crump
Cambridge University, United Kingdom
Mechanisms Controlling the Egress of Herpes Simplex Virus
Upon final envelopment, newly assembled herpes simplex virus particles are contained within large cytoplasmic transport vesicles. These virion-containing vesicles are then transported to the plasma membrane where they fuse to secrete virus particles into the extracellular environment. Once secreted, the majority of HSV-1 particles remain cell associated, potentially aiding the spread of infection to neighbouring cells. We have been investigating the mechanisms of HSV-1 egress and cell-to-cell spread, in particular the viral and cellular factors important for controlling virus secretion. Recently, we identified that loss of function of the envelope glycoprotein complex gE-gI, through deletion of either protein or a single amino acid mutation in the extracellular domain of gI, substantially increases HSV-1 release into the culture media. Furthermore, we have also demonstrated that a complex of two conserved tegument proteins, pUL7 and pUL51, localize to focal adhesion complexes and stabilise the attachment of infected cells to their surroundings. Our data suggest the combined action of these two HSV-1 protein complexes, gE-gI and pUL7-pUL51, facilitates the rapid and efficient spread of infection to neighbouring cells by controlling the sites of virus secretion and maintaining cell contact points.

Keynote: Virus-Cell Interactions: Gene Expression and Replication
Sunday, 30 July, 13:30-14:10

Fanxiu Zhu Keynote Speaker
Fanxiu Zhu
Florida State University, United States
Gammaherpesvirus-specific tegument proteins of Kaposi's sarcoma-associated herpesvirus
About a third of herpesvirus-encoded proteins are detectable in the extracellular virions. Among them, the most diverse group of proteins reside between capsid and envelope of virions and are known as tegument proteins. Tegument proteins can be brought into cells during infection and exert their functions at the early stages of the infection process. The unique temporal and spatial expressions of tegument proteins put them in the forefront of coping with the host cellular environment. Therefore, the actions of the tegument proteins may determine the fate and outcome of infection, namely latent versus lytic or productive versus abortive infections. While a few tegument proteins are conserved among all herpesviruses, the most abundant tegument proteins appear to be unique for each subfamily. These subfamily-specific tegument proteins have evolved to have ancillary but important functions in viral-host interactions. Largely because of the lack of robust lytic replication of EBV and KSHV, our knowledge of gammaherpesvirus tegument proteins has lagged behind those of alpha- and beta-herpesviruses. This talk will highlight our recent discoveries and current understanding of the gammaherpesvirus-specific tegument proteins ORF45 and ORF52 of KSHV.

Symposium Session II: Virus-Cell Interactions: Gene Expression and Replication
Sunday, 30 July, 14:10-14:35

Ayman El Guindy Symposium Speaker
Ayman El Guindy
Yale University, United States
The Epstein-Barr Virus Immunoevasins BCRF1 and BPLF1 Are Expressed by a Mechanism Independent of the Canonical Late Pre-initiation Complex
Subversion of host immune surveillance is a crucial step in viral pathogenesis. Epstein-Barr virus (EBV) encodes two immune evasion gene products, BCRF1 (viral IL-10) and BPLF1 (deubiquitinase/deneddylase); both proteins suppress antiviral immune responses during primary infection. The BCRF1 and BPLF1 genes are expressed during the late phase of the lytic cycle, an essential but poorly understood phase of viral gene expression. Several late gene regulators recently identified in beta and gamma herpesviruses form a viral pre-initiation complex for transcription. Whether each of these late gene regulators is necessary for transcription of all late genes is not known. Here, studying viral gene expression in the absence and presence of siRNAs to individual components of the viral pre-initiation complex, we identified two distinct groups of late genes. One group includes late genes encoding the two immunoevasins, BCRF1 and BPLF1, and is transcribed independently of the viral pre-initiation complex. The second group primarily encodes viral structural proteins and is dependent on the viral pre-initiation complex. The protein kinase BGLF4 is the only known late gene regulator necessary for expression of both groups of late genes. ChIP-seq analysis showed that the transcription activator Rta associates with the promoters of eight late genes including genes encoding the viral immunoevasins. Our results demonstrate that late genes encoding immunomodulatory proteins are transcribed by a mechanism distinct from late genes encoding viral structural proteins. Understanding the mechanisms that specifically regulate expression of the late immunomodulatory proteins could aid the development of antiviral drugs that impair immune evasion by the oncogenic EB virus.

Symposium Session II: Virus-Cell Interactions: Gene Expression and Replication
Sunday, 30 July, 14:35-15:00

Oren Kobiler Symposium Speaker
Oren Kobiler
Tel Aviv University, Israel
It’s all about the cell: single cell studies of HSV-1 infection
Diversity among genetically identical cells lead to significant heterogeneity in the outcome of viral infection. We used single cell studies to identify sources of variability among cells in their susceptibility to HSV-1 infection. A unique set of genetically barcoded viral genomes was constructed and used to demonstrate that viral gene expression is tightly linked to the number of viral genomes replicating per cell. We found that high cellular gene expression was an indicator for a lower viral gene expression in a given cell. Our results suggest that alterations in the levels of host proteins involved in intrinsic antiviral defense may result in differences in the number of viral genomes replicating per cell. Further investigation revealed that the host cell state prior to infection is an important determinant for the probability of a cell to be infected with HSV-1. Taken together, the results suggest that the levels of host factors have an important role in determining the probability of an entering HSV-1 genome to complete a successful infection.

Keynote: Virus-Host Interactions: Pathogenesis
Monday, 31 July, 8:30-9:10

Blossom Damania Keynote Speaker
Blossom Damania
UNC-Chapel Hill, United States
Oncogenic Rewiring of Cell Signaling Networks by KSHV
Kaposi sarcoma - associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma, and two lymphoproliferative diseases, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). Moreover, KSHV is the causative agent of KS-immune reconstitution syndrome (KS-IRIS) and KSHV - inflammatory cytokine syndrome (KICS). KSHV encodes multiple viral proteins as well as viral microRNAs and long non-coding RNAs. KSHV promotes tumorigenesis by modulating cell signaling networks, enhancing angiogenesis, and evading immune sensing pathways. Understanding the mechanisms by which KSHV manipulates cellular pathways will allow us to identify targets for future therapeutics again KSHV-associated viral cancers.

Symposium Session III: Virus-Host Interactions: Pathogenesis
Monday, 31 July, 9:10-9:35

Maria Nagel Symposium Speaker
Maria Nagel
University of Colorado, United States
VZV VASCULOPATHY: Past, Present and Future
Primary infection of humans with varicella zoster virus (VZV) causes varicella (chickenpox), after which virus becomes latent in cranial nerve ganglia, dorsal root ganglia, sympathetic and parasympathetic ganglia, enteric ganglia and adrenal glands along the entire neuraxis. As VZV-specific cell-mediated immunity declines in elderly and immunocompromised individuals, VZV reactivates from one or more ganglia and typically travels peripherally to skin producing herpes zoster (shingles). However, VZV can also spread centrally, with or without rash, to produce intra- and extracranial vascular disease (VZV vasculopathy) including transient ischemic attacks, stroke, aneurysm, hemorrhage, giant cell arteritis, arterial dissection, ischemic cranial neuropathies, cerebral venous sinus thrombosis, spinal cord infarction, granulomatous aortitis, and peripheral thrombotic disease. Herein, the history of VZV vasculopathy will be reviewed beginning from initial clinical observations of stroke following varicella or zoster, demonstration of virus within diseased arteries, epidemiological studies that establish zoster as a stroke and myocardial infarction risk factor, studies demonstrating that the host immune response plays a significant role in vascular wall damage, and the role of vaccine in VZV vasculopathy. Lastly, the impact of VZV vasculopathy on the U.S. aging population, which is estimated to reach ~83 million by 2050 of which 95% harbor latent virus and 50% will reactivate by 85 years of age, will be discussed.

Symposium Session III: Virus-Host Interactions: Pathogenesis
Monday, 31 July, 9:35-10:00

Sallie Permar Symposium Speaker
Sallie Permar
Duke University, United States
Potent maternal antibody protects against congenital CMV transmission
The development of an effective vaccine that can protect against congenital CMV transmission has been impeded by a lack of understanding of the immune responses that will protect against placental CMV transmission. We have recently developed a non-human primate model of congenital CMV transmission that can be used to tease apart which immune responses are necessary and sufficient for protection against placental transmission. In this model, we established that polyclonal antibody isolated from seropositive rhesus monkey donors and passively infused in seronegative rhesus monkey dams can protect against both placental CMV transmission and fetal loss in the absence of T cell responses. This finding implicates that congenital CMV vaccines can focus on elicitation of potent maternal antibody responses to preventing congenital CMV transmission and disease.

Symposium Session III: Virus-Host Interactions: Pathogenesis
Monday, 31 July, 10:00-10:25

Bo Zhao Symposium Speaker
Bo Zhao
Brigham and Women's Hospital, United States
Epstein-Barr virus super-enhancer eRNAs are essential for MYC oncogene expression and lymphoblast proliferation
Super-enhancers are clusters of strong enhancers, critically important for development, differentiation and oncogenesis. Epstein-Barr Virus (EBV) super-enhancers (ESEs) are enhancers co-occupied by all essential EBV oncogenes and EBV activated NF-kB subunits. ESEs have extraordinary high signals for H3K27ac, indicative of high transcription activities. RNA Pol II links these ESEs to genes essential for EBV transformed lymphoblast growth and survival, including MYC, BCL2, MCL1, and IRF4. CRISPR deletions of MYC ESEs greatly reduced MYC expression and stopped lymphoblast growth. To further understand the molecular composition of ESEs, we reanalyzed published lymphoblast global run-on followed by deep-sequencing and found abundant enhancer RNA (eRNAs) expression at the ESEs. Inactivation of EBV oncogene or BRD4 inhibitor JQ1 treatment greatly reduced MYC ESE eRNAs expression. shRNA knock down of MYC ESE eRNAs greatly reduced MYC expression, LCL growth, ESE H3K27ac signals, and MYC ESEs looping to MYC TSS. These data indicate that ESE eRNAs are critically important for ESE functions.

Priscilla Schaffer Memorial Lecture
Monday, 31 July, 10:45-11:20

Moriah Szpara Keynote Speaker
Moriah Szpara
Pennsylvania State University, United States
How comparative genomics of alphaherpesviruses yields insights on attenuation and virulence
Herpesviruses are pervasive pathogens of the human and animal world. We often discuss their acquisition, prevalence, and impact at a species level. For instance, human herpes simplex virus 1 (HSV-1) affects over 65% of the population, often infecting via the oral niche, but more recently presenting in the form of primary genital infections. We have demonstrated that isolates of HSV-1 from around the globe can differ by up to 3-4% genome-wide. This is akin to the level of genetic difference between humans and chimpanzees. The total impacts of this sequence divergence are unknown. We are addressing this knowledge gap by studying alpha-herpesviruses in diverse field, clinical, and culture environments, from the perspective of both human and veterinary alpha-herpesviruses. These studies have revealed insights about the genetic and phenotypic differences that exist between viral isolates, as well as the more subtle variations that exist within a population of any single strain. We are currently investigating how this diversity relates to the viral population found in an infected individual. We have also examined the genetic changes that occur during sequential passage of alpha-herpesviruses in culture, as has been done in the past to attenuate viruses for vaccine applications, but also occurs to a lesser degree when any virus is passaged in culture. We now have a diverse array of insights from molecular, cellular, and genomic studies, which we are applying to the more complex question of understanding how viral genetic diversity impacts the outcome of infection.

VZV Foundation Lecture
Monday, 31 July, 11:20-12:00

Catherine Sadzot Keynote Speaker
Catherine Sadzot
University of Liège, Belgium
ORF9p: a key figure for primary and secondary Varicella Zoster Virus envelopment.
Herpesviruses assembly and envelopment are highly complex processes requiring numerous interactions between viral and cellular components. The tegument proteins are known to play a critical role in these critical steps. VZV ORF9p (VP22 homolog) is one of the tegument proteins that is highly expressed during the productive cycle. We have recently shown that at the nuclear level, ORF9p, interacts with the Nuclear Egress Complex (NEC) while in the cytoplasm, it interacts with the Adaptor Protein 1 complex (AP-1), responsible for the clathrin-mediated transport between the TGN and the endosomes. Some ORF9p mutants lacking either the acidic region or the ORF47p dependent phosphorylation consensus sequence are impaired for their infectivity and show aberrant phenotypes at the nuclear and/or cytoplasmic level. All these data support the hypothesis that ORF9p is a key figure in both the primary and secondary envelopment. This hypothesis will be discussed in view of the knowledge concerning other herpesviruses.

Keynote: Virus-Host Interactions: Innate Immunity
Tuesday, 1 August, 8:30-9:10

Sören Paludan Keynote Speaker
Sören Paludan
Aarhus University, Denmark
Activation and regulation of the cGAS-STING pathway by HSV-1
Innate immunological sensing of herpesviruses is important for proper control of the infections, and the IFN system is known to be essential for the early defense mechanisms. Viral DNA is an important trigger of IFN expression, and this is mediated mainly through the cGAS-STING pathway. In this talk I will present, recent data on the role of the cGAS-STING pathway in control of HSV-1 infections. In addition, I will discuss how HSV-1 and other herpesviruses seek to evade the cGAS-STING pathway to promote establishment and maintenance of infection.

Symposium Session IV: Virus-Host Interactions: Innate Immunity
Tuesday, 1 August, 9:10-9:35

Stipan Jonjic Symposium Speaker
Stipan Jonjic
University of Rijeka, Croatia
NK cells mediate microglia polarization during congenital CMV infection
Congenital human cytomegalovirus (HCMV) infection is the most common viral cause of long-term neurodevelopmental sequelae, including mental retardation, microcephaly and sensorineural hearing loss. As HCMV does not cross species barrier, we employed a mouse model in which newborn mice are infected with mouse cytomegalovirus (MCMV). NK cells were shown to play an important role in fighting cytomegalovirus (CMV) infection and adaptive features of NK cells in response to CMV infection are recently being increasingly recognized. However, the extent to which congenital CMV infection affects and shapes NK-cell mediated immunity is largely unknown. To address this issue, we used MCMV infected newborn mice and followed the impact of infection on the maturation and functional properties of NK cells. We demonstrated that MCMV infection leads to persistent alteration of transcriptional activity and strongly affects the maturation and function of NK cells. NK cell expression of T-box transcription factor Eomes, critical for NK cell development, was dramatically impaired. The downregulation of Eomes correlated with major changes in NK cell phenotype, indicating most notably NK cell exhaustion, as well as an impaired NK cell response to different stimuli. This population of NK cells persisted for several months in infected mice indicating that congenital CMV infection shapes NK cell response over long-term period. Despite of this strong effect of MCMV on NK cell maturation, NK cells appear to be essential in polarization of microglia toward proinflammatory phenotype in mice infected as newborns. We have previously shown that in infected newborn mice the virus replicates in the brain parenchyma and induces delay in cerebellar growth. In addition, infection induces dramatic upregulation of MHC II molecules on microglia which can be abolished by depletion of NK cells or neutralization of IFNγ. Notably, IFNγ neutralization also normalized altered cerebellar development. In my talk I will focus on various immunoregulatory and developmental aspects of NK cell functions during perinatal CMV infection.

Symposium Session IV: Virus-Host Interactions: Innate Immunity
Tuesday, 1 August, 9:35-10:00

Philip Stevenson Symposium Speaker
Philip Stevenson
University of Queensland, Australia
Host colonization by Murine Cytomegalovirus
Murine cytomegalovirus (MCMV) enters new hosts via olfactory neurons, then spreads systemically via lymph nodes. MCMV injected into footpads also reaches lymph nodes. It is captured by subcapsular sinus macrophages, which recruit innate immune defences. Olfactory MCMV bypasses subcapsular sinus macrophages by travelling in dendritic cells. Normally dendritic cells migrate from the subcapsular sinus to meet naive lymphocytes near high endothelial venules. MCMV-infected dendritic cells migrate further, and leave lymph nodes via high endothelial venules to enter the blood. This requires the viral M33, a constitutively active chemokine receptor. Without M33, infected dendritic cells accumulate in lymph nodes and infection spreads poorly. Close functional homology between M33 and the Human CMV chemokine receptors encoded by UL33 and US28 suggests that HCMV follows a similar scheme, and so that at least some circulating, HCMV-infected dendritic cells come from peripheral sites rather than infected stem cells.

Symposium Session IV: Virus-Host Interactions: Innate Immunity
Tuesday, 1 August, 10:00-10:25

Alain Vanderplasschen Symposium Speaker
Alain Vanderplasschen
University of Liège, Belgium
Conserved fever pathways across vertebrates: a herpesvirus delays fish behavioral fever through expression of a decoy Tnf-alpha receptor
When infected by pathogens, endotherms and ectotherms can both increase their body temperature to limit the infection. Ectotherms do so by moving to warmer places, hence the term "behavioral fever". We studied the expression of behavioral fever by common carp infected by cyprinid herpesvirus 3. We showed that carp maintained at 24°C all died from the infection, whereas those housed in multi-chamber tanks encompassing a 24°C-32°C gradient all survived as a consequence of their transient migration to the warmest compartment. As the expression of behavioral fever occurred only at an advanced stage of the disease, we hypothesized that the virus might delay this phenomenon in order to promote its replication. The data support this hypothesis, and the delay mechanism was found to rely on the expression of a soluble viral decoy receptor for Tnf-alpha. This study is the first to report the control of behavioral fever by a pathogen. It has been recently published in Cell Host & Microbe 21, 244-253 (2017).

Keynote: Virus-Host Interactions: Adaptive Immunity
Tuesday, 1 August, 13:30-14:10

Rajiv Khanna Keynote Speaker
Rajiv Khanna
QIMR Berghofer Medical Research Institute, Australia
EBV Immune Regulation in Health and Disease: Clinical Translation of Novel Immunotherapies
The biology and immunology of Epstein-Barr virus (EBV) has continued to fascinate researchers because the lessons learnt provide a platform for understanding the interplay between the biology of this ubiquitous infection, the immune system seeking to restrict its spread and the emergence of a variety of malignancies. As with other gamma herpes viruses, EBV encodes a large set of lytic cycle genes together with a number of latent genes which are associated with expansion of the latent EBV pool in B-lymphocytes. Current evidence suggests that the virus gains entry into the body by infection of B-lymphocytes in the oral cavity via an interaction between the major viral glycoprotein gp340 and the complement receptor CR2 which is expressed on B-cells, although a role for CR2-expressing or non-expressing epithelial and/or T-cells cannot be totally discounted. In either case, evidence suggests that the earliest detectable event following primary infection is the expression of lytic cycle proteins resulting in the release of infectious virus into the oral cavity followed by a generalized seeding of latently infected B-lymphocytes throughout the body. This primary infection results in symptoms of acute infectious mononucleosis (IM) in about 50% of adolescents and is coincident with a marked lymphocytosis (dominated by EBV-specific cytotoxic T-cells) and the appearance of an lgM response to a variety of EBV proteins, most notably the viral capsid antigen, VCA. Current evidence suggests that this cytotoxic T-cell (CTL) response, which includes both CD4+ and CD8+ cells restricts expansion of these latently infected B-cells and results in a long-term carrier state in which there is an equilibrium between the level of secretion of the virus and the number of latently infected B-cells. Over the two decades, this knowledge has provided an important platform for developing novel immunotherapeutic strategies for the treatment of EBV-associated diseases.

Symposium Session V: Virus-Host Interactions: Adaptive Immunity
Tuesday, 1 August, 14:10-14:35

Jennifer Lund Symposium Speaker
Jennifer Lund
Fred Hutchinson Cancer Research Center, United States
Regulation of mucosal immune responses to genital HSV-2 infection
Infections such as genital HSV-2 and HIV, that infect and replicate in mucosal tissues, are significant global health burdens that continue despite large-scale efforts to develop protective vaccines. A barrier to development of efficacious vaccines and novel treatment strategies is the lack of a clear understanding of how immune responses are developed, maintained, and regulated in mucosal tissues, as these processes appear to differ in distinct mucosal tissue compartments as compared to the more thoroughly studied lymphoid tissues and blood. Our goal is to elucidate the mechanisms of induction, maintenance, and regulation of protective mucosal immune responses to HSV-2 infection using mouse models and human tissues.

Symposium Session V: Virus-Host Interactions: Adaptive Immunity
Tuesday, 1 August, 14:35-15:00

Luka Cicin-Sain Symposium Speaker
Luka Cicin-Sain
Helmholtz Centre for Infection Research, Germany
Ongoing proliferation of MCMV-specific effector T-cells
Cytomegalovirus induces the strongest known immune response in human medicine, with effector memory T cells (TEM) specific for certain epitopes accumulating over time in a process called memory inflation. TEM are generally assumed to be short-lived cells that poorly proliferate upon in vitro antigenic restimulation and thus require a steady stream of proliferating central-memory T-cells (TCM) to maintain their high numbers in memory inflation. Our new data challenges that model and we propose that inflationary cells are maintained by robust in vivo cycling within the TEM subset. We measured the proliferation of antigen-specific T-cells at 7 or 120 days post infection with MCMV or VACV by measuring Ki67 expression in flow-cytometry. A small Ki67hiBcl2- TEM population was consistently retained in MCMV infected mice, but absent in VACV infection, arguing for antigen-driven TEM proliferation during latency. To corroborate the role of TEM-intrinsic proliferation in the maintenance of their pool, we performed metabolic labeling of cycling cells with D2O. TEM cells acquired D2O more rapidly than TCM, and its half-life was shorter in these cells, arguing for robust TEM proliferation. We validated these results by targeted depletion of memory and proliferating subsets. Upon antibody mediated depletion, TEM were replenished more rapidly than TCM, implying that they cycle faster than the TCM. Finally, we validated our model by selectively depleting the proliferating T cell subset. This resulted in a selective loss of Ki67hiBcl2- T cells, an increase in the death of TEM and MCMV-specific inflationary cells, and an overall reduction of this compartment. We observed no effects on the TCM subset. In conclusion, our data strongly argue that memory inflation is maintained by antigen-driven proliferation of antigen-specific TEM T cells, rather than a continued expansion and differentiation of central-memory T-cells.

Keynote: Virus-Host Interactions: Latency and Reactivation
Wednesday, 2 August, 8:30-9:10

Felicia Goodrum Keynote Speaker
Felicia Goodrum
University of Arizona, United States
Control of host trafficking and signaling by human cytomegalovirus
Herpesviruses persist indefinitely in their host through complex and poorly defined interactions that mediate a life-long infection. The virus-host interactions important to latency of human cytomegalovirus (HCMV), as well as the very nature of the latent infection, is a centerpiece of our research. HCMV coordinates the expression of four viral genes from a genetic locus that plays an important role in dictating patterns of infection in cell types including CD34+ hematopoietic progenitor cells and endothelial cells. Two viral genes encoded within this locus, UL135 and UL138, have opposing roles in regulating viral replication. UL135 promotes reactivation from latency and virus replication in hematopoietic progenitor cells, in part, by overcoming replication-suppressive effects of UL138. UL135 and UL138 oppose one another by targeting the host factor, epidermal growth factor receptor (EGFR), but with opposite effects. pUL135 promotes internalization and turnover of EGFR from the cell surface, whereas pUL138 preserves surface expression and activation of EGFR. EGFR is sequestered in an activated form within the infection-induced, juxtanuclear viral assembly compartment and is unresponsive to stress. Sequestration of EGFR and other signaling proteins is the result of dramatic HCMV-induced alterations of vesicular trafficking pathways in infection. Host cargo internalized from the cell surface that would be either recycled or degraded are retained in enlarged sorting endosomes. These findings have important implications for how this virus may modify the ability of the infected cell to sense and respond to extracellular stimuli or present antigen. We propose a model whereby HCMV fine tunes the trafficking and signaling of homeostatic regulators to control states of latency and replication in HCMV infection.

Symposium Session VI: Virus-Host Interactions: Latency and Reactivation
Wednesday, 2 August, 9:10-9:35

Anna Cliffe Symposium Speaker
Anna Cliffe
University of Virginia, United States
Stress-Induced Changes to HSV-1 Chromatin During Reactivation
During a latent infection of peripheral neurons, the HSV lytic gene promoters are assembled into silent heterochromatin. To permit reactivation, this heterochromatin-based repression needs to be overcome. Various stimuli are known to trigger reactivation, including axotomy, heat shock, estrogen receptor signaling and loss of neurotrophic support. Using both in vitro and in vivo models of HSV latency, we are investigating how these stimuli result in up-regulation of viral lytic gene expression from silenced promoters. We have found that activation of c-Jun N-terminal kinase (JNK) following neuronal stress is required for the earliest up-regulation of lytic gene expression during reactivation. This early step in reactivation, known as Phase I, utilizes mechanisms of gene expression that are distinct from de novo lytic replication. Unlike lytic replication and full (Phase II) reactivation, Phase I gene expression occurs even in the absence of histone demethylase activity. Specifically, the activities of histone H3K9 (LSD1) and H3K27me3 (JMJD3 and UTX) demethylases are not required for Phase I reactivation, despite being required for the progression to full reactivation. Instead, the serine residue neighboring the methylated lysine residue becomes phosphorylated, resulting in a histone phospho/methyl switch. This process is thought to permit gene expression through eviction of repressive proteins (e.g. HP1, PRC2 complex) that are present on the HSV-1 genome during latency. JNK itself is capable of phosphorylating recombinant histone H3 in vitro and is present on viral lytic gene promoters during reactivation, therefore providing a direct link between the neuronal cell stress response and changes to the viral chromatin during reactivation.

Symposium Session VI: Virus-Host Interactions: Latency and Reactivation
Wednesday, 2 August, 9:35-10:00

Tiffany Reese Symposium Speaker
Tiffany Reese
University of Texas, United States
Understanding the effects of co-infection on herpesvirus latency and vice versa
Humans are infected with 8-12 chronic viruses, and over 90% of the population is infected with a gammaherpesvirus. Herpesviruses represent an important component of our virome, and are influencing our immune systems in positive and negative ways. Moreover, immune responses to other pathogens can alter the state of chronic infection, leading to herpesvirus reactivation. Using murine gammaherpesvirus-68, we are examining on the whole animal and on the molecular level the effects of parasite infection on herpesvirus reactivation. Through the alteration of host cytokines and viral promoter sensing of cytokine signaling, co-infection can modulate gammaherpesvirus latency and reactivation. Our work also suggests that herpesviruses change the immune systems ability to mount immune responses to challenges with other pathogens and vaccines.

Symposium Session VI: Virus-Host Interactions: Latency and Reactivation
Wednesday, 2 August, 10:00-10:25

Benedikt Kaufer Symposium Speaker
Benedikt Kaufer
University of Berlin, Germany
Latency - Beyond the Circular Episome.
The establishment of latency allows herpesviruses to persist in the host for life. The dogma has been that all herpesviruses maintain their genome as a circular episome. However, several herpesviruses have recently been shown to integrate their genome into telomeres of latently infected cells. Among these are human herpesvirus 6A (HHV-6A) and 6B (HHV-6B) that maintain their integrated virus genome in the absence of episomal DNA. Integration of HHV-6 also occurs in germ cells, resulting in individuals that harbor the integrated virus genome in every single cell of their body and transmit it to their offspring. This condition has been termed inherited chromosomally integrated HHV-6 (iciHHV-6). About 1% of the human population have this condition, while the biological and medical consequences for these individuals remain poorly understood. Intriguingly, the genome of HHV-6A/B and 15 other herpesviruses harbor telomeric repeats (TMRs) at their ends, which are identical to host telomere sequences (TTAGGG). We recently demonstrated that the viral TMRs facilitate integration of the virus genome into host telomeres. In addition, viral and cellular factors have been proposed to mediate integration of HHV-6 and other herpesviruses into host telomeres. The presentation will highlight the recent advances in the understanding of this integration mechanism.

Keynote: Virus Control: Prevention and Treatment
Wednesday, 2 August, 13:30-14:10

Ravit Arav-Boger Keynote Speaker
Ravit Arav-Boger
Johns Hopkins University School of Medicine, United States
CMV Drug Development
The last few years has seen progress in drug development for CMV. Both directly acting antivirals and host-dependent agents have been identified. Repurposing of drugs for CMV therapy remains an area of interest although specific considerations for CMV such as pharmacokinetics and pharmacodynamics will be important. Understanding mechanisms of action of host-directed anti-CMV agents, as well as their efficacy when combined with approved anti-CMV agents may provide new strategies for CMV therapy. Anticipating directly-acting anti-CMV agents will select for resistant viruses may support combination regimens as already exist for other chronic viral infection. I will discuss our studies of the antimalarial agents, artemisinins, the old drug emetine and preliminary data from a large high throughput screen.

Symposium Session VII: Virus Control: Prevention and Treatment
Wednesday, 2 August, 14:10-14:35

Jeff Cohen Symposium Speaker
Jeff Cohen
NIH/NIAID, Maryland
Development of a vaccine for Epstein-Barr virus
Epstein-Barr virus (EBV) is the major cause of infectious mononucleosis and is associated with many cancers including Hodgkin and Burkitt lymphoma and nasopharyngeal and gastric carcinoma. A phase 2 trial of a soluble EBV gp350 showed that it reduced infectious mononucleosis by 78%, but did not prevent infection. In an effort to improve upon the soluble gp350 vaccine, we have developed a nanoparticle-based EBV gp350 vaccine that induces 100-fold higher B cell neutralizing antibody titers than soluble gp350 in mice. We also constructed a nanoparticle-based gH/gL/gp42 vaccine that induces 15-fold higher epithelial cell neutralizing titers than the soluble glycoproteins in mice. Either vaccine results in 100-fold higher neutralizing titers than those found in EBV seropositive humans. We have collaborated with another group at NIH to solve the crystal structure of gp350 bound to its receptor CD21 which should facilitate the design of vaccines and therapeutics to block EBV infection through its receptor.

Symposium Session VII: Virus Control: Prevention and Treatment
Wednesday, 2 August, 14:35-15:00

Mark Schleiss Symposium Speaker
Mark Schleiss
CIDMTR, University of Minnesota, United States
CMV Vaccines 2017: Where do we Stand? What do we Need to Learn?
Congenital human cytomegalovirus (HCMV) infection can result in in severe and permanent neurological injury in newborns, and vaccine development is accordingly a major public health priority. HCMV can also cause severe disease in solid organ (SOT) and hematopoietic stem cell transplant (HSCT) recipients, and a vaccine would be valuable in prevention of viremia and end-organ disease in these populations. Currently there is no licensed HCMV vaccine, but progress toward this goal has been made in recent clinical trials. An adjuvanted recombinant HCMV glycoprotein B (gB) vaccine has been shown to have some efficacy in prevention of infection in young women and adolescents, and provided benefit to HCMV-seronegative SOT recipients. Similarly, DNA vaccines based on gB and the immunodominant T-cell target, pp65 (ppUL83), have been shown to reduce viremia in HSCT patients. Promising approaches currently in clinical trials include VLP vaccines, live-attenuated HCMV chimeras, LCMV-vectored vaccines, RNA and DNA-based vaccines, and DISC vaccines. This talk will provide an overview of HCMV vaccine candidates in various stages of development, as well as an update on the current status of ongoing clinical trials. Insights from relevant animal models, including the murine, rhesus macaque, and guinea pig models of infection will be reviewed. Approaches aimed at overcoming virally-encoded immune modulation gene products in design of attenuated live vaccines, tested in animal models, will be discussed, as will novel adjuvant strategies aimed at optimizing immunogenicity. Recognizing that the optimum requirements of HCMV vaccination may vary depending upon the population being immunized, an emphasis will be placed on those efforts aimed at defining protective correlates of immunity for the maternal-placental-fetal compartment. This information will be essential for licensure of a vaccine against congenital HCMV infection, a major unmet medical need.

Closing Keynote & Handover
Wednesday, 2 August, 15:30-16:15

David Knipe Keynote Speaker
David Knipe
Harvard Medical School, Massachusetts
Epigenetic Regulation of Herpes Simplex Virus Lytic and Latent Gene Expression
Eukaryotic cells use epigenetic mechanisms to load heterochromatin on foreign DNA, such as transfected and viral DNAs, to restrict their transcription. The herpesviral DNA genomes have no associated histones in the virion, but upon their entry into the nucleus, host cell mechanisms rapidly load heterochromatin on the viral DNAs. Viral gene products counter this host cell response to allow lytic gene expression or to further modify the silencing during latent infection. In this talk I will describe three series of studies in our laboratory on host and viral mechanisms of epigenetic regulation of herpes simplex virus lytic and latent gene expression. First, in human foreskin fibroblasts (HFFs), HSV DNA is loaded with heterochromatin within 1-2 hours, but the host cell factors involved have not been identified. We have used quantitative image analysis to identify the host proteins co-localizing with input viral DNA within 15-30 minutes post-infection. Studies are underway to identify their role in early chromatin structure. Second, combinatorial studies of the role of IFI16 and ND10 proteins in HSV ICP0-null mutant virus replication have been conducted, and the effects are additive. To our surprise, PML exerts a positive effect on ICP0-null mutant virus replication in HFFs. Third, we have defined three HSV functions that promote a latent infection that is silenced but capable of reactivation, a state that we have called a "poised latent infection." The three functions, the latency-associated transcript, ICP0, and the CTRL2 CTCF binding site, all promote the H3K27me3 facultative heterochromatin modification on lytic gene promoters and promote reactivation. We propose that one of the mechanisms by which HSV ensures its ability to go latent and reactivate is the use of viral gene products and cis-acting sequences to establish a "poised latent infection."