Human cytomegalovirus immediate early proteins promote degradation of connexin 43 and disrupt gap junction communication: implications for a role in gliomagenesis

Human coronavirus OC43 infection remodels connexin 43-mediated gap junction intercellular communication in vitro

β-coronaviruses cause acute infection in the upper respiratory tract, resulting in various symptoms and clinical manifestations. OC43 is a human β-coronavirus that induces mild clinical symptoms and can be safely studied in the BSL2 laboratory. Due to its low risk, OC43 can be a valuable and accessible model for understanding β-coronavirus pathogenesis. One potential target for limiting virus infectivity could be gap junction-mediated communication. This study aims to unveil the status of cell-to-cell communications through gap junctions in human β-coronavirus infection. Infection with OC43 leads to reduced expression of Cx43 in A549, a lung epithelial carcinoma cell line. Infection with this virus also shows a significant ER and oxidative stress increase. Internal localization of Cx43 is observed post-OC43 infection in the endoplasmic reticulum-Golgi intermediate compartment (ERGIC) region, which impairs the gap junction communication between two adjacent cells, confirmed by Lucifer yellow dye transfer assay. It also affects hemichannel formation, as depicted by the EtBr uptake assay. Impairment of Cx43 trafficking and the ability to form hemichannels and functional GJIC are hampered by virus-induced Golgi apparatus disruption. Altogether, these results suggest that several physiological changes accompany OC43 infection in A549 cells and can be considered an appropriate model system for understanding the differences in gap junction communication post-viral infections. This model system can provide valuable insights for developing therapies against human β-coronavirus infections.IMPORTANCEThe enduring impact of the recent SARS-CoV-2 pandemic underscores the importance of studying human β-coronaviruses, advancing our preparedness for future coronavirus infections. As SARS-CoV-2 is highly infectious, another human β-coronavirus OC43 can be considered an experimental model. One of the crucial pathways that can be considered is gap junction communication, as it is vital for cellular homeostasis. Our study seeks to understand the changes in Cx43-mediated cell-to-cell communication during human β-coronavirus OC43 infection. In vitro studies showed downregulation of the gap junction protein Cx43 and upregulation of the endoplasmic reticulum and oxidative stress markers post-OC43 infection. Furthermore, HCoV-OC43 infection causes reduced Cx43 trafficking, causing impairment of functional hemichannel and GJIC formation by virus-mediated Golgi apparatus disruption. Overall, this study infers that OC43 infection reshapes intercellular communication, suggesting that this pathway may be a promising target for designing highly effective therapeutics against human coronaviruses by regulating Cx43 expression.

Diversity of Intercellular Communication Modes: A Cancer Biology Perspective

From the moment a cell is on the path to malignant transformation, its interaction with other cells from the microenvironment becomes altered. The flow of molecular information is at the heart of the cellular and systemic fate in tumors, and various processes participate in conveying key molecular information from or to certain cancer cells. For instance, the loss of tight junction molecules is part of the signal sent to cancer cells so that they are no longer bound to the primary tumors and are thus free to travel and metastasize. Upon the targeting of a single cell by a therapeutic drug, gap junctions are able to communicate death information to by-standing cells. The discovery of the importance of novel modes of cell-cell communication such as different types of extracellular vesicles or tunneling nanotubes is changing the way scientists look at these processes. However, are they all actively involved in different contexts at the same time or are they recruited to fulfill specific tasks? What does the multiplicity of modes mean for the overall progression of the disease? Here, we extend an open invitation to think about the overall significance of these questions, rather than engage in an elusive attempt at a systematic repertory of the mechanisms at play.

Connexin 43 trafficking and regulation of gap junctional intercellular communication alters ovarian cancer cell migration and tumorigenesis

Ovarian cancer persists to be the most lethal gynecological malignancy, demanding rigorous treatments involving radio-chemotherapy that trigger toxicity and consequently mortality among patients. An improved understanding of the disease progression may pioneer curative therapies. Mouse epithelial ovarian cancer cell lines, ID8 and ID8-VEGF (overexpressing VEGF) were intraperitoneally injected in C57BL/6 female mice to develop a Syngeneic Ovarian cancer mouse model. It was observed that ID8-VEGF cells were able to induce aggressive tumor growth in mice compared to ID8 cells. Furthermore, results of the current in vitro study comparing ID8 and ID8-VEGF demonstrated that highly tumorigenic ID8-VEGF had reduced gap junctional intercellular communication (GJIC) due to intracellular Connexin 43 (Cx43) expression. Additionally, ID8 cells with reduced tumorigenic capability expressed significant GJIC. Furthermore, loss of GJIC in ID8-VEGF cells induced shorter tunneling nanotube formations, while ID8 cells develops longer tunneling nanotube to maintain cellular crosstalk. The administration of a pharmacological drug 4-phenylbutyrate (4PBA) ensured the restoration of GJIC in both the ovarian cancer cell lines. Additionally, 4PBA treatment significantly inhibited the migration of ovarian cancer cell lines and tumor formation in ovarian cancer mice models. In summary, the 4PBA-mediated restoration of GJIC suppressed migration (in vitro) and tumorigenesis (in vivo) of ovarian cancer cells. The present study suggests that Cx43 assembled GJIC and its supportive signaling pathways are a prospective target for restricting ovarian cancer progression.

Downregulation of neurodevelopmental gene expression in iPSC-derived cerebral organoids upon infection by human cytomegalovirus

Human cytomegalovirus (HCMV) is a betaherpesvirus that can cause severe birth defects including vision and hearing loss, microcephaly, and seizures. Currently, no approved treatment options exist for in utero infections. Here, we aimed to determine the impact of HCMV infection on the transcriptome of developing neurons in an organoid model system. Cell populations isolated from organoids based on a marker for infection and transcriptomes were defined. We uncovered downregulation in key cortical, neurodevelopmental, and functional gene pathways which occurred regardless of the degree of infection. To test the contributions of specific HCMV immediate early proteins known to disrupt neural differentiation, we infected NPCs using a recombinant virus harboring a destabilization domain. Despite suppressing their expression, HCMV-mediated transcriptional downregulation still occurred. Together, our studies have revealed that HCMV infection causes a profound downregulation of neurodevelopmental genes and suggest a role for other viral factors in this process.

Hearing Loss Caused by HCMV Infection through Regulating the Wnt and Notch Signaling Pathways

Hearing loss is one of the most prevalent sensory disabilities worldwide with huge social and economic burdens. The leading cause of sensorineural hearing loss (SNHL) in children is congenital cytomegalovirus (CMV) infection. Though the implementation of universal screening and early intervention such as antiviral or anti-inflammatory ameliorate the severity of CMV-associated diseases, direct and targeted therapeutics is still seriously lacking. The major hurdle for it is that the mechanism of CMV induced SNHL has not yet been well understood. In this review, we focus on the impact of CMV infection on the key players in inner ear development including the Wnt and Notch signaling pathways. Investigations on these interactions may gain new insights into viral pathogenesis and reveal novel targets for therapy.

Functional regulation of the structure-specific endonuclease FEN1 by the human cytomegalovirus protein IE1 suggests a role for the re-initiation of stalled viral replication forks

Flap endonuclease 1 (FEN1) is a member of the family of structure-specific endonucleases implicated in regulation of DNA damage response and DNA replication. So far, knowledge on the role of FEN1 during viral infections is limited. Previous publications indicated that poxviruses encode a conserved protein that acts in a manner similar to FEN1 to stimulate homologous recombination, double-strand break (DSB) repair and full-size genome formation. Only recently, cellular FEN1 has been identified as a key component for hepatitis B virus cccDNA formation. Here, we report on a novel functional interaction between Flap endonuclease 1 (FEN1) and the human cytomegalovirus (HCMV) immediate early protein 1 (IE1). Our results provide evidence that IE1 manipulates FEN1 in an unprecedented manner: we observed that direct IE1 binding does not only enhance FEN1 protein stability but also phosphorylation at serine 187. This correlates with nucleolar exclusion of FEN1 stimulating its DSB-generating gap endonuclease activity. Depletion of FEN1 and inhibition of its enzymatic activity during HCMV infection significantly reduced nascent viral DNA synthesis demonstrating a supportive role for efficient HCMV DNA replication. Furthermore, our results indicate that FEN1 is required for the formation of DSBs during HCMV infection suggesting that IE1 acts as viral activator of FEN1 in order to re-initiate stalled replication forks. In summary, we propose a novel mechanism of viral FEN1 activation to overcome replication fork barriers at difficult-to-replicate sites in viral genomes.

A novel role of SIRT2 in regulating gap junction communications via connexin-43 in bovine cumulus-oocyte complexes

SIRT2, the predominantly cytosolic sirtuin, plays important role in multiple biological processes, including metabolism, stress response, and aging. However, the function of SIRT2 in gap junction intercellular communications (GJICs) of cumulus-oocyte complexes (COCs) is not yet known. The purpose of the present study was to evaluate the effect and underlining mechanism of SIRT2 on GJICs in COCs. Here, we found that treatment with SIRT2 inhibitors (SirReal2 or TM) inhibited bovine oocyte nuclear maturation. Further analysis revealed that SIRT2 inactivation disturbed the GJICs of COCs during in vitro maturation. Correspondingly, both the Cx43 phosphorylation levels and MEK/MER signaling pathways were induced by SIRT2 inhibition. Importantly, SIRT2-mediated Cx43 phosphorylation was completely abolished by treatment with MEK1/2 inhibitor (Trametinib). Furthermore, treatment with SIRT2 inhibitors resulted in the high levels of MEK1/2 acetylation. Functionally, downregulating the MER/ERK pathways with inhibitors (Trametinib or SCH772984) could attenuate the closure of GJICs caused by SIRT2 inactivation in partly. In addition, inhibition of SIRT2 activity significantly decreased the membrane and zona pellucida localization of Cx43 by upregulating the levels of Cx43 acetylation. Taken together, these results demonstrated a novel role that SIRT2 regulates GJICs via modulating the phosphorylation and deacetylation of Cx43 in COCs.

Bright and Early: Inhibiting Human Cytomegalovirus by Targeting Major Immediate-Early Gene Expression or Protein Function

The human cytomegalovirus (HCMV), one of eight human herpesviruses, establishes lifelong latent infections in most people worldwide. Primary or reactivated HCMV infections cause severe disease in immunosuppressed patients and congenital defects in children. There is no vaccine for HCMV, and the currently approved antivirals come with major limitations. Most approved HCMV antivirals target late molecular processes in the viral replication cycle including DNA replication and packaging. “Bright and early” events in HCMV infection have not been exploited for systemic prevention or treatment of disease. Initiation of HCMV replication depends on transcription from the viral major immediate-early (IE) gene. Alternative transcripts produced from this gene give rise to the IE1 and IE2 families of viral proteins, which localize to the host cell nucleus. The IE1 and IE2 proteins are believed to control all subsequent early and late events in HCMV replication, including reactivation from latency, in part by antagonizing intrinsic and innate immune responses. Here we provide an update on the regulation of major IE gene expression and the functions of IE1 and IE2 proteins. We will relate this insight to experimental approaches that target IE gene expression or protein function via molecular gene silencing and editing or small chemical inhibitors.

Targeting different domains of gap junction protein to control malignant glioma

A rational treatment strategy for glioma, the most common primary central nervous system tumor, should focus on early invasive growth and resistance to current therapeutics. Connexin 43 (Cx43), a gap junction protein, plays important roles not only in the development of the central nervous system and but also in the progression of glioma. The different structural domains of Cx43, including extracellular loops, transmembrane domains, and an intracellular carboxyl terminal, have distinct functions in the invasion and proliferation of gliomas. Targeting these domains of Cx43, which is expressed in distinct patterns in the heterogeneous glioma cell population, can inhibit tumor cell invasion and new tumor formation. Thus, this review summarizes the structural characteristics of Cx43, the effects of regulating different Cx43 domains on the biological characteristics of glioma cells, intervention strategies targeting different domains of Cx43, and future research directions.

Connexins in cancer: bridging the gap to the clinic

Gap junctions comprise arrays of intercellular channels formed by connexin proteins and provide for the direct communication between adjacent cells. This type of intercellular communication permits the coordination of cellular activities and plays key roles in the control of cell growth and differentiation and in the maintenance of tissue homoeostasis. After more than 50 years, deciphering the links among connexins, gap junctions and cancer, researchers are now beginning to translate this knowledge to the clinic. The emergence of new strategies for connexin targeting, combined with an improved understanding of the molecular bases underlying the dysregulation of connexins during cancer development, offers novel opportunities for clinical applications. However, different connexin isoforms have diverse channel-dependent and -independent functions that are tissue and stage specific. This can elicit both pro- and anti-tumorigenic effects that engender significant challenges in the path towards personalised medicine. Here, we review the current understanding of the role of connexins and gap junctions in cancer, with particular focus on the recent progress made in determining their prognostic and therapeutic potential.

In vitro inhibited effect of gap junction composed of Cx43 in the invasion and metastasis of testicular cancer resistanced to cisplatin

The effect of gap junction intercellular communication composed of connexin on cancer invasion/metastasis has been thoroughly explored; however, its effect on testicular cancer resistanced to chemotherapy is still unclear. In this study, we found that the capability of invasion and migration of I-10/DDP (cisplatin (DDP)-resistance) cells were elevated. Furthermore, the expression of Cx43 and the function of gap junction (GJ) in I-10/DDP cells were decreased compared with parental I-10 cells. Pharmacological inhibition of GJs by oleamide (Olea) enhanced invasion and migration. However, enhancement of GJs by retinoic acid (RA) decreased invasion and migration of I-10/DDP cells. To further clarify the invasion/migration inhibited effect of GJ in the testicular cancer resistanced to DDP, GJ function was modulated by overexpression and knockdown of Cx43 expression. Overexpression of Cx43 reduced invasion and migration of I-10/DDP cells. Conversely, knockdown of Cx43 expression increased invasion and migration of I-10/DDP cells. In summary, GJ composed of Cx43 inhibits I-10/DDP cells invasion and migration, and it may become the potential therapeutic target for testicular cancer chemotherapy.

Essential role of HCMV deubiquitinase in promoting oncogenesis by targeting anti-viral innate immune signaling pathways

Cancer is a multifactorial disease and virus-mediated carcinogenesis is one of the crucial factors, which is poorly understood. Human cytomegalovirus (HCMV) is a herpesvirus and its components have been evidenced to be associated with cancer of different tissue origin. However, its role in cancer remains unknown. Here, we identified a conserved herpesviral tegument protein known as pUL48 of HCMV, encoding deubiquitinase enzyme, as having a key role in carcinogenesis. We show using deubiquitinase sufficient- and deficient-HCMV that HCMV deubiquitinase is a key in inducing enhanced cellular metabolic activity through upregulation of several anti-apoptotic genes and downregulation of several pro-apoptotic genes expression. Furthermore, HCMV deubiquitinase acquires pro-tumor functions by inhibiting PRR-mediated type I interferon via deubiquitination of TRAF6, TRAF3, IRAK1, IRF7 and STING. Taken together, our results suggest that HCMV infection may promote oncogenesis by inhibiting innate immunity of the host.

HIV-Associated Cardiovascular Disease: Role of Connexin 43

Chronic HIV infection due to effective antiretroviral treatment has resulted in a broad range of clinical complications, including accelerated heart disease. Individuals with HIV infection have a 1.5 to 2 times higher incidence of cardiovascular diseases than their uninfected counterparts; however, the underlying mechanisms are poorly understood. To explore the link between HIV infection and cardiovascular diseases, we used postmortem human heart tissues obtained from HIV-infected and control uninfected individuals to examine connexin 43 (Cx43) expression and distribution and HIV-associated inflammation. Here, we demonstrate that Cx43 is dysregulated in the hearts of HIV-infected individuals. In all HIV heart samples analyzed, there were areas where Cx43 was overexpressed and found along the lateral membrane of the cardiomyocyte and in the intercalated disks. Areas of HIV tissue with anomalous Cx43 expression and localization also showed calcium overload, sarcofilamental atrophy, and accumulation of collagen. All these changes were independent of viral replication, CD4 counts, inflammation, and type of antiretroviral treatment. Overall, we propose that HIV infection increases Cx43 expression in heart, resulting in tissue damage that likely contributes to the high rates of cardiovascular disease in HIV-infected individuals.

Human cytomegalovirus microRNAs are carried by virions and dense bodies and are delivered to target cells

Human cytomegalovirus (HCMV) infection results in the production of virions, dense bodies (DBs) and non-infectious enveloped particles, all of which incorporate proteins and RNAs that can be transferred to host cells. Here, we investigated whether virions and DBs also carry microRNAs (miRNAs) and assessed their delivery and functionality in cells. Human lung fibroblasts (MRC-5) were infected with the HCMV strain AD169, and conditioned cell culture medium was collected and centrifuged. The pellets were treated with RNase-ONE, and the virions and DBs were purified with a potassium tartrate–glycerol gradient and dialysed. The virions and DBs were incubated with micrococcal nuclease, DNA and RNA were extracted and then analysed with TaqMan PCR assays, while the proteins were examined with Western blots. To assess the delivery of miRNAs to cells and their functionality, virions and DBs were irradiated with UV light. The purity of the virions and DBs was confirmed by typical morphology, the presence of the structural protein pp65 and the HCMV genome, the ability to infect MRC-5 cells and the absence of the host genome. RNA analysis revealed the presence of 14 HCMV-encoded miRNAs (UL22A-5p, US25-1-5p, UL22A-3p, US5-2-3p, UL112-3p, US25-2-3p, US25-2-5p, US33-3p, US5-1, UL36-5p, US4-5p, UL36-3p, UL70-5p and US25-1-3p), HCMV immediate-early mRNA and long non-coding RNA2.7, moreover, two host-encoded miRNAs (hsa-miR-218-5p and hsa-miR-21-5p) and beta-2-microglobulin RNA. UV-irradiated virions and DBs delivered viral miRNAs (US25-1-5p and UL112-3p) to the host cells, and miR-US25-1-5p was functional in a luciferase reporter assay. We conclude that virions and DBs carry miRNAs that are biologically functional and can be delivered to cells, which may affect cellular processes.

High prevalence of cytomegalovirus infection in surgical intestinal specimens from infants with necrotizing enterocolitis and spontaneous intestinal perforation: A retrospective observational study

BACKGROUND

Necrotizing enterocolitis (NEC) is a severe, often fatal gastrointestinal emergency that predominantly affects preterm infants, and there is evidence that neonatal cytomegalovirus (CMV) infection may in some cases contribute to its pathogenesis.

OBJECTIVES

This study aimed to evaluate the prevalence of CMV in infants with NEC.

STUDY DESIGN

Seventy intestinal specimens from 61 infants with NEC, spontaneous intestinal perforation (SIP), or related surgical complications were collected at Karolinska University Hospital and Uppsala University Hospital, Sweden. Ten specimens from autopsied infants without bowel disease served as controls. Samples were analyzed for CMV immediate-early antigen (IEA), CMV late antigen (LA), 5-lipoxigenase (5LO) and CMV-DNA by immunohistochemistry (IHC) and in situ hybridization (ISH), respectively. In 10 index samples, CMV DNA was analyzed with Taqman PCR after laser capture microdissection (LCM) of cells positive for CMV IEA by IHC.

RESULTS

CMV IEA was detected by IHC in 57 (81%) and CMV LA in 45 (64%) of 70 intestinal specimens from index cases; 2 (20%) of 10 control specimens were positive for both antigens. 5LO was detected in intestinal tissue section obtained from all examined index and controls. CMV DNA was detected in 4 of 10 samples (40%) after LCM. By ISH, all 13 IHC-IEA-positive samples were positive for CMV DNA; however, 3 of 5 IHC-IEA-negative samples (60%) were also positive.

CONCLUSIONS

CMV-specific antigens and CMV DNA were highly prevalent in intestinal specimens from infants with NEC, SIP, and related surgical complications. Our findings provide further evidence that neonatal CMV infection contributes to the pathogenesis of these diseases and may affect patient outcome.

The Major Immediate-Early Protein IE2 of Human Cytomegalovirus Is Sufficient to Induce Proteasomal Degradation of CD83 on Mature Dendritic Cells

Human cytomegalovirus (HCMV) is the prototypic beta-herpesvirus and widespread throughout the human population. While infection is asymptomatic in healthy individuals, it can lead to high morbidity and mortality in immunocompromised persons. Importantly, HCMV evolved multiple strategies to interfere with immune cell function in order to establish latency in infected individuals. As mature DCs (mDCs) are antigen-presenting cells able to activate naïve T cells they play a crucial role during induction of effective antiviral immune responses. Interestingly, earlier studies demonstrated that the functionally important mDC surface molecule CD83 is down-regulated upon HCMV infection resulting in a reduced T cell stimulatory capacity of the infected cells. However, the viral effector protein and the precise mechanism of HCMV-mediated CD83 reduction remain to be discovered. Using flow cytometric analyses, we observed significant down-modulation of CD83 surface expression becoming significant already 12 h after HCMV infection. Moreover, Western bot analyses revealed that, in sharp contrast to previous studies, loss of CD83 is not restricted to the membrane-bound molecule, but also occurs intracellularly. Furthermore, inhibition of the proteasome almost completely restored CD83 surface expression during HCMV infection. Results of infection kinetics and cycloheximide-actinomycin D-chase experiments, strongly suggested that an HCMV immediate early gene product is responsible for the induction of CD83 down-modulation. Consequently, we were able to identify the major immediate early protein IE2 as the viral effector protein that induces proteasomal CD83 degradation.

Connexin and pannexin channels in cancer

Communication among cells via direct cell-cell contact by connexin gap junctions, or between cell and extracellular environment via pannexin channels or connexin hemichannels, is a key factor in cell function and tissue homeostasis. Upon malignant transformation in different cancer types, the dysregulation of these connexin and pannexin channels and their effect in cellular communication, can either enhance or suppress tumorigenesis and metastasis. In this review, we will highlight the latest reports on the role of the well characterized connexin family and its ability to form gap junctions and hemichannels in cancer. We will also introduce the more recently discovered family of pannexin channels and our current knowledge about their involvement in cancer progression.

All-trans retinoic acid arrests cell cycle in leukemic bone marrow stromal cells by increasing intercellular communication through connexin 43-mediated gap junction

Background

Gap junctional intercellular communication (GJIC) is typically decreased in malignant tumors. Gap junction is not presented between hematopoietic cells but occurred in bone marrow stromal cells (BMSCs). Connexin 43 (Cx43) is the major gap junction (GJ) protein; our previous study revealed that Cx43 expression and GJIC were decreased in acute leukemic BMSCs. All-trans retinoic acid (ATRA) increases GJIC in a variety of cancer cells and has been used to treat acute promyelocytic leukemia, but the effects of ATRA on leukemic BMSCs is unknown. In this study, we evaluated the potential effects of ATRA on cell cycle, proliferation, and apoptosis of leukemic BMSCs. Effects of ATRA on Cx43 expression and GJIC were also examined.

Methods

Human BMSCs obtained from 25 patients with primary acute leukemia, and 10 normal healthy donors were cultured. Effects of ATRA on cell cycle, cell proliferation, and apoptosis were examined with or without co-treatment with amphotericin-B. Cx43 expression was examined at both the mRNA and protein expression levels. GJIC was examined by using a dye transfer assay and measuring the rate of fluorescence recovery after photobleaching (FRAP).

Results

ATRA arrested the cell cycle progression, inhibited cell growth, and increased apoptosis in leukemic BMSCs. Both Cx43 expression and GJIC function were increased by ATRA treatment. Most of the observed effects mediated by ATRA were abolished by amphotericin-B pretreatment.

Conclusions

ATRA arrests cell cycle progression in leukemic BMSCs, likely due to upregulating Cx43 expression and enhancing GJIC function.

Electronic supplementary material

The online version of this article (doi:10.1186/s13045-015-0212-7) contains supplementary material, which is available to authorized users.

Epigenetic regulation of human cytomegalovirus latency: an update

Human cytomegalovirus (HCMV) is a ubiquitous virus which infects 50-90% of the population worldwide. In immunocompetent hosts, HCMV either remains unnoticed or causes mild symptoms. Upon primary infection it establishes latent infection in a few cells. However, in certain situations where immunity is either immature or compromised, HCMV may reactivate and cause mortality and morbidity. Therefore, it is utmost important to understand how HCMV establishes latent infection and associated mechanisms responsible for its reactivation. Several mechanisms are involved in the regulation of latency including chromatin remodeling by an array of enzymes and microRNAs. Here we will describe the epigenetic regulation of HCMV latency. Further we will discuss the unique HCMV latency signature and patho-physiological relevance of latent HCMV infection.

Quantitative temporal viromics: an approach to investigate host-pathogen interaction

A systematic quantitative analysis of temporal changes in host and viral proteins throughout the course of a productive infection could provide dynamic insights into virus-host interaction. We developed a proteomic technique called “quantitative temporal viromics” (QTV), which employs multiplexed tandem-mass-tag-based mass spectrometry. Human cytomegalovirus (HCMV) is not only an important pathogen but a paradigm of viral immune evasion. QTV detailed how HCMV orchestrates the expression of >8,000 cellular proteins, including 1,200 cell-surface proteins to manipulate signaling pathways and counterintrinsic, innate, and adaptive immune defenses. QTV predicted natural killer and T cell ligands, as well as 29 viral proteins present at the cell surface, potential therapeutic targets. Temporal profiles of >80% of HCMV canonical genes and 14 noncanonical HCMV open reading frames were defined. QTV is a powerful method that can yield important insights into viral infection and is applicable to any virus with a robust in vitro model.

PaperClip

•

>8,000 proteins quantified over eight time points, including 1,200 cell-surface proteins

•

Temporal profiles of 139/171 canonical HCMV proteins and 14 noncanonical HCMV ORFs

•

Multiple families of cell-surface receptors selectively modulated by HCMV

•

Multiple signaling pathways modulated during HCMV infection

Identification and HLA-tetramer-validation of human CD4+ and CD8+ T cell responses against HCMV proteins IE1 and IE2

Human cytomegalovirus (HCMV) is an important human pathogen. It is a leading cause of congenital infection and a leading infectious threat to recipients of solid organ transplants as well as of allogeneic hematopoietic cell transplants. Moreover, it has recently been suggested that HCMV may promote tumor development. Both CD4+ and CD8+ T cell responses are important for long-term control of the virus, and adoptive transfer of HCMV-specific T cells has led to protection from reactivation and HCMV disease. Identification of HCMV-specific T cell epitopes has primarily focused on CD8+ T cell responses against the pp65 phosphoprotein. In this study, we have focused on CD4+ and CD8+ T cell responses against the immediate early 1 and 2 proteins (IE1 and IE2). Using overlapping peptides spanning the entire IE1 and IE2 sequences, peripheral blood mononuclear cells from 16 healthy, HLA-typed, donors were screened by ex vivo IFN-γ ELISpot and in vitro intracellular cytokine secretion assays. The specificities of CD4+ and CD8+ T cell responses were identified and validated by HLA class II and I tetramers, respectively. Eighty-one CD4+ and 44 CD8+ T cell responses were identified representing at least seven different CD4 epitopes and 14 CD8 epitopes restricted by seven and 11 different HLA class II and I molecules, respectively, in total covering 91 and 98% of the Caucasian population, respectively. Presented in the context of several different HLA class II molecules, two epitope areas in IE1 and IE2 were recognized in about half of the analyzed donors. These data may be used to design a versatile anti-HCMV vaccine and/or immunotherapy strategy.

Role of connexin/pannexin containing channels in infectious diseases

In recent years it has become evident that gap junctions and hemichannels, in concert with extracellular ATP and purinergic receptors, play key roles in several physiological processes and pathological conditions. However, only recently has their importance in infectious diseases been explored, likely because early reports indicated that connexin containing channels were completely inactivated under inflammatory conditions, and therefore no further research was performed. However, recent evidence indicates that several infectious agents take advantage of these communication systems to enhance inflammation and apoptosis, as well as to participate in the infectious cycle of several pathogens. In the current review, we will discuss the role of these channels/receptors in the pathogenesis of several infectious diseases and the possibilities of generating novel therapeutic approaches to reduce or prevent these diseases.

Murine cytomegalovirus protein pM92 is a conserved regulator of viral late gene expression

In this study, we report that murine cytomegalovirus (MCMV) protein pM92 regulates viral late gene expression during virus infection. Previously, we have shown that MCMV protein pM79 and its human cytomegalovirus (HCMV) homologue pUL79 are required for late viral gene transcription. Identification of additional factors involved is critical to dissecting the mechanism of this regulation. We show here that pM92 accumulated abundantly at late times of infection in a DNA synthesis-dependent manner and localized to nuclear viral replication compartments. To investigate the role of pM92, we constructed a recombinant virus SMin92, in which pM92 expression was disrupted by an insertional/frameshift mutation. During infection, SMin92 accumulated representative viral immediate-early gene products, early gene products, and viral DNA sufficiently but had severe reduction in the accumulation of late gene products and was thus unable to produce infectious progeny. Coimmunoprecipitation and mass spectrometry analysis revealed an interaction between pM92 and pM79, as well as between their HCMV homologues pUL92 and pUL79. Importantly, we showed that the growth defect of pUL92-deficient HCMV could be rescued in trans by pM92. This study indicates that pM92 is an additional viral regulator of late gene expression, that these regulators (represented by pM92 and pM79) may need to complex with each other for their activity, and that pM92 and pUL92 share a conserved function in CMV infection. pM92 represents a potential new target for therapeutic intervention in CMV disease, and a gateway into studying a largely uncharted viral process that is critical to the viral life cycle.