The expression of interleukin-32 is activated by human cytomegalovirus infection and down regulated by hcmv-miR-UL112-1

A mechanism of human cytomegalovirus for establishing latency through inhibition of HCMV UL16 expression by hcmv-miR-US33-5p

Human cytomegalovirus (HCMV) is the only beta herpesvirus that can encode microRNA (miRNA). As one of the 26 HCMV miRNAs, hcmv-miR-US33-5p has been reported to inhibit viral DNA synthesis and DNA replication via downregulation of the host gene syntaxin 3. Here, we tested the luciferase activity of 8 other putative target mRNAs of hcmv-miR-US33-5p, which were identified via hybrid PCR, 7 of which decreased following the over expression of hcmv-miRNA-US33-5p. A viral gene, HCMV UL16, was confirmed to be a direct target of hcmv-miR-US33-5p since both luciferase activity and protein levels were decreased by hcmv-miR-US33-5p overexpression. Moreover, by using a reconstituted virus with UL16 deletion, we found that UL16 is not an essential gene for the ability of hcmv-miR-US33-5p to downregulate DNA replication. UL16 plays a critical role in NK cell evasion by sequestering NKG2D ligands in the endoplasmic reticulum (ER) and reducing their cell surface expression. We demonstrated that over expression of hcmv-miR-US33-5p induced some NKG2D ligands independent of other HCMV genes and decreased the interaction between MICB and UL16. These stimulating NKG2D ligands can be recognized by NKG2D and subsequently activate NK cells. Our results provide insight into the mechanisms by which HCMV promotes latency through the inhibition of UL16 and the stimulation of NKG2D ligand expression by hcmv-miR-US33-5p.

Human cytomegalovirus microRNAs: strategies for immune evasion and viral latency

Viruses use various strategies and mechanisms to deal with cells and proteins of the immune system that form a barrier against infection. One of these mechanisms is the encoding and production of viral microRNAs (miRNAs), whose function is to regulate the gene expression of the host cell and the virus, thus creating a suitable environment for survival and spreading viral infection. miRNAs are short, single-stranded, non-coding RNA molecules that can regulate the expression of host and viral proteins, and due to their non-immunogenic nature, they are not eliminated by the cells of the immune system. More than half of the viral miRNAs are encoded and produced by Orthoherpesviridae family members. Human cytomegalovirus (HCMV) produces miRNAs that mediate various processes in infected cells to contribute to HCMV pathogenicity, including immune escape, viral latency, and cell apoptosis. Here, we discuss which cellular and viral proteins or cellular pathways and processes these mysterious molecules target to evade immunity and support viral latency in infected cells. We also discuss current evidence that their function of bypassing the host's innate and adaptive immune system is essential for the survival and multiplication of the virus and the spread of HCMV infection.

MicroRNAs in infectious diseases: potential diagnostic biomarkers and therapeutic targets

MicroRNAs (miRNAs) are conserved, short, non-coding RNAs that play a crucial role in the post-transcriptional regulation of gene expression. They have been implicated in the pathogenesis of cancer and neurological, cardiovascular, and autoimmune diseases. Several recent studies have suggested that miRNAs are key players in regulating the differentiation, maturation, and activation of immune cells, thereby influencing the host immune response to infection. The resultant upregulation or downregulation of miRNAs from infection influences the protein expression of genes responsible for the immune response and can determine the risk of disease progression. Recently, miRNAs have been explored as diagnostic biomarkers and therapeutic targets in various infectious diseases. This review summarizes our current understanding of the role of miRNAs during viral, fungal, bacterial, and parasitic infections from a clinical perspective, including critical functional mechanisms and implications for their potential use as biomarkers and therapeutic targets.

Current Knowledge on the Interaction of Human Cytomegalovirus Infection, Encoded miRNAs, and Acute Aortic Syndrome

Aortic dissection is a clinicopathological entity caused by rupture of the intima, leading to a high mortality if not treated. Over time, diagnostic and investigative methods, antihypertensive therapy, and early referrals have resulted in improved outcomes according to registry data. Some data have also emerged from recent studies suggesting a link between Human Cytomegalovirus (HCMV) infection and aortic dissection. Furthermore, the use of microRNAs has also become increasingly widespread in the literature. These have been noted to play a role in aortic dissections with elevated levels noted in studies as early as 2017. This review aims to provide a broad and holistic overview of the role of miRNAs, while studying the role of HCMV infection in the context of aortic dissections. The roles of long non-coding RNAs, circular RNAs, and microRNAs are explored to identify changes in expression during aortic dissections. The use of such biomarkers may one day be translated into clinical practice to allow early detection and prognostication of outcomes and drive preventative and therapeutic options in the future.

Viral miRNA regulation of host gene expression

Viruses have evolved a multitude of mechanisms to combat barriers to productive infection in the host cell. Virally-encoded miRNAs are one such means to regulate host gene expression in ways that benefit the virus lifecycle. miRNAs are small non-coding RNAs that regulate protein expression but do not trigger the adaptive immune response, making them powerful tools encoded by viruses to regulate cellular processes. Diverse viruses encode for miRNAs but little sequence homology exists between miRNAs of different viral species. Despite this, common cellular pathways are targeted for regulation, including apoptosis, immune evasion, cell growth and differentiation. Herein we will highlight the viruses that encode miRNAs and provide mechanistic insight into how viral miRNAs aid in lytic and latent infection by targeting common cellular processes. We also highlight how viral miRNAs can mimic host cell miRNAs as well as how viral miRNAs have evolved to regulate host miRNA expression. These studies dispel the myth that viral miRNAs are subtle regulators of gene expression, and highlight the critical importance of viral miRNAs to the virus lifecycle.

Hcmv-miR-UL148D regulates the staurosporine-induced apoptosis by targeting the Endoplasmic Reticulum to Nucleus signaling 1(ERN1)

The propensity of viruses to co-opt host cellular machinery by reprogramming the host's RNA-interference machinery has been a major focus of research, however, regulation of host defense mechanisms by virus-encoded miRNA, is an additional regulatory realm gaining momentum in the arena of host-viral interactions. The Human Cytomegalovirus (HCMV) miRNAs, regulate many cellular pathways alone or in concordance with HCMV proteins, thereby paving a conducive environment for successful infection in the human host. We show that HCMV miRNA, hcmv-miR-UL148D inhibits staurosporine-induced apoptosis in HEK293T cells. We establish that ERN1 mRNA is a bonafide target of hcmv-miR-UL148D and its encoded protein IRE1α is translationally repressed by the overexpression of hcmv-miR-UL148D resulting in the attenuation of apoptosis. Unlike the host microRNA seed sequence (6-8 nucleotides), hcmv-miR-UL148D has long complementarity to 3' UTR of ERN1 mRNA resulting in mRNA degradation. The repression of IRE1α by the hcmv-miR-UL148D further downregulates Xbp1 splicing and c-Jun N-terminal kinase phosphorylation thus regulating ER-stress and ER-stress induced apoptotic pathways. Strikingly, depletion of ERN1 attenuates staurosporine-induced apoptosis which further suggests that hcmv-miR-UL148D functions through regulation of its target ERN1. These results uncover a role for hcmv-miR-UL148D and its target ERN1 in regulating ER stress-induced apoptosis.

Human Cytomegalovirus Induced Aberrant Expression of Non-coding RNAs

Human cytomegalovirus (HCMV) is a β-herpesvirus whose genome consists of double stranded linear DNA. HCMV genome can generate non-coding RNAs (ncRNAs) through transcription in its host cells. Besides that, HCMV infection also changes the ncRNAs expression profile of the host cells. ncRNAs play a key role in maintaining the normal physiological activity of cells, and the disorder of ncRNAs expression has numerous adverse effects on cells. However, until now, the relationship between ncRNAs and HCMV-induced adverse effects are not summarized in detail. This review aims to give a systematic summary of the role of HCMV infection in ncRNAs expression while providing insights into the molecular mechanism of unnormal cellular events caused by ncRNAs disorder. ncRNAs disorder induced by HCMV infection is highly associated with cell proliferation, apoptosis, tumorigenesis, and immune regulation, as well as the development of cardiovascular diseases, and the potential role of biomarker. We summarize the studies on HCMV associated ncRNAs disorder and suggest innovative strategies for eliminating the adverse effects caused by HCMV infection.

The complex biology of human cytomegalovirus latency

While many viral infections are limited and eventually resolved by the host immune response or by death of the host, other viruses establish long-term relationships with the host by way of a persistent infection, that range from chronic viruses that may be eventually cleared to those that establish life-long persistent or latent infection. Viruses infecting hosts from bacteria to humans establish quiescent infections that must be reactivated to produce progeny. For mammalian viruses, most notably herpesviruses, this quiescent maintenance of viral genomes in the absence of virus replication is referred to as latency. The latent strategy allows the virus to persist quiescently within a single host until conditions indicate a need to reactivate to reach a new host or, to re-seed a reservoir within the host. Here, I review common themes in viral strategies to regulate the latent cycle and reactivate from it ranging from bacteriophage to herpesviruses with a focus on human cytomegalovirus (HCMV). Themes central to herpesvirus latency include, epigenetic repression of viral gene expression and mechanisms to regulate host signaling and survival. Critical to the success of a latent program are mechanisms by which the virus can "sense" fluctuations in host biology (within the host) or environment (outside the host) and make appropriate "decisions" to maintain latency or re-initiate the replicative program. The signals or environments that indicate the establishment of a latent state, the very nature of the latent state, as well as the signals driving reactivation have been topics of intense study from bacteriophage to human viruses, as these questions encompass the height of complexity in virus-host interactions-where the host and the virus coexist.

microRNA, a Subtle Indicator of Human Cytomegalovirus against Host Immune Cells

Human cytomegalovirus (HCMV) is a double-stranded DNA virus that belongs to the β-herpesvirus family and infects 40–90% of the adult population worldwide. HCMV infection is usually asymptomatic in healthy individuals but causes serious problems in immunocompromised people. We restricted this narrative review (PubMed, January 2022) to demonstrate the interaction and molecular mechanisms between the virus and host immune cells with a focus on HCMV-encoded miRNAs. We found a series of HCMV-encoded miRNAs (e.g., miR-UL112 and miR-UL148D) are explicitly involved in the regulation of viral DNA replication, immune evasion, as well as host cell fate. MiRNA-targeted therapies have been explored for the treatment of atherosclerosis, cardiovascular disease, cancer, diabetes, and hepatitis C virus infection. It is feasible to develop an alternative vaccine to restart peripheral immunity or to inhibit HCMV activity, which may contribute to the antiviral intervention for serious HCMV-related diseases.

Fetal Central Nervous System Derived Extracellular Vesicles: Potential for Non-invasive Tracking of Viral Mediated Fetal Brain Injury

Introduction

Extracellular vesicles derived from the fetal central nervous system (FCNSEs) can be purified from maternal serum or plasma using the protein Contactin-2/TAG1that is expressed almost exclusively by developing neurons in the hippocampus, cerebral cortex and cerebellum. We hypothesized that fetal CNSEs could be used to non-invasively detect and quantify viral mediated in-utero brain injury in the first trimester.

Materials and Methods

First trimester maternal samples were collected from a human clinical population infected with primary cytomegalovirus (CMV) and a non-human primate model of Zika (ZIKV) infection. In the CMV cohort, a nested case control study was performed comparing pregnancies with and without fetal infection. Cases of fetal infection were further subdivided into those with and without adverse neurologic outcome. ZIKV samples were collected serially following maternal inoculation or saline. All ZIKV cases had histopathologic findings on necropsy. Serum was precipitated with ExoQuick solution and FCEs were isolated with biotinylated anti-Contactin-2/TAG1 antibody-streptavidin matrix immunoabsorption. FCE Synaptopodin (SYNPO) and Neurogranin (NG) protein levels were measured using standard ELISA kits and normalized to the exosome marker CD81.

Results

Fetal CNSE SYNPO and NG were significantly reduced in cases of first trimester fetal CMV infection compared to those with infection limited to the mother but could not discriminate between fetal infection with and without adverse neurologic outcome. Following ZIKV inoculation, fetal CNSE SYNPO was reduced by 48 h and significantly reduced by day 4.

Discussion

These data are the first to suggest that first trimester non-invasive diagnosis of fetal viral infection is possible. Fetal CNSEs have the potential to augment clinical and pre-clinical studies of perinatal viral infection. Serial sampling may be needed to discriminate between fetuses that are responding to treatment and/or recovering due to innate defenses and those that have ongoing neuronal injury. If confirmed, this technology may advance the paradigm of first trimester prenatal diagnosis and change the calculus for the cost benefit of CMV surveillance programs in pregnancy.

Human Cytomegalovirus miR-US25-1 Targets the GTPase RhoA To Inhibit CD34+ Hematopoietic Progenitor Cell Proliferation To Maintain the Latent Viral Genome

Human cytomegalovirus (HCMV) microRNAs play essential roles in latency and reactivation in CD34+ hematopoietic progenitor cells (HPCs) via regulation of viral and cellular gene expression. In the present study, we show that HCMV miR-US25-1 targets RhoA, a small GTPase required for CD34+ HPC self-renewal, proliferation, and hematopoiesis. Expression of miR-US25-1 impairs signaling through the nonmuscle myosin II light chain, which leads to a block in cytokinesis and an inhibition of proliferation. Moreover, infection with an HCMV mutant lacking miR-US25-1 resulted in increased proliferation of CD34+ HPCs and a decrease in the proportion of genome-containing cells at the end of latency culture. These observations provide a mechanism by which HCMV limits proliferation to maintain latent viral genomes in CD34+ HPCs.IMPORTANCE Each herpesvirus family establishes latency in a unique cell type. Since herpesvirus genomes are maintained as episomes, the virus needs to devise mechanisms to retain the latent genome during cell division. Alphaherpesviruses overcome this obstacle by infecting nondividing neurons, while gammaherpesviruses tether their genome to the host chromosome in dividing B cells. The betaherpesvirus human cytomegalovirus (HCMV) establishes latency in CD34+ hematopoietic progenitor cells (HPCs), but the mechanism used to maintain the viral genome is unknown. In this report, we demonstrate that HCMV miR-US25-1 downregulates expression of RhoA, a key cell cycle regulator, which results in inhibition of CD34+ HPC proliferation by blocking mitosis. Mutation of miR-US25-1 during viral infection results in enhanced cellular proliferation and a decreased frequency of genome-containing CD34+ HPCs. These results reveal a novel mechanism through which HCMV is able to regulate cell division to prevent viral genome loss during proliferation.

Paracoccidioidesbrasiliensis induces IL-32 and is controlled by IL-15/IL-32/vitamin D pathway in vitro

Paracoccidioidomycosis (PCM) is a systemic fungal disease caused by Paracoccidioides spp., whose clinical outcome depends on immune response. Interleukin 32 (IL-32) is a cytokine present in inflammatory and infectious diseases, including bacterial, virus and protozoan infections. Its role in fungal disease remains unclear. The axis IL-15, IL-32 and vitamin D leads to microbicidal capacity against intracellular pathogens. Thus, the aims of this study were to investigate the production of IL-32 during Paracoccidioides spp. infection and whether this cytokine and IL-15 can increase P. brasiliensis control in a vitamin D dependent manner. IL-32 was highly detected in oral lesions from patients with PCM. In addition, high production of this cytokine was intracellularly detected in peripheral blood mononuclear cells (PBMCs) from healthy donors after exposure to particulated P. brasiliensis antigens (PbAg). The IL-32γ isoform was predominantly expressed, but there was mRNA alternative splicing for IL-32α isoform. The induction of IL-32 was dependent on Dectin-1 receptor. Infection of PBMCs with P. brasiliensis yeasts did not significantly induce IL-32 production even after activation with exogenous IFN-γ or IL-15 treatments. Although IL-15 was a potent inducer of IL-32 production, treatment with this cytokine did not increase the fungal control unless vitamin D was present in high levels. In this case, both IL-15 and IL-32 increased fungicidal activity of PBMCs. Together, data showed that IL-32 is present in lesions of PCM, PbAg induces IL-32, and the axis of IL-15/IL-32/vitamin D can contribute to control fungal infection. The data suggest that exposure to molecules from P. brasiliensis, as β-glucans, is needed to induce IL-32 production since only heat-killed and sonicated P. brasiliensis yeasts were able to increase IL-32, which was blocked by anti-Dectin-1 antibodies. This is the first description about IL-15/IL-32/vitamin D pathway role in P. brasiliensis infection.

miR-3 Encoded by Hepatitis B Virus Downregulates PTEN Protein Expression and Promotes Cell Proliferation

Purpose

Chronic hepatitis B virus (HBV) infection is a key determinant of hepatocellular carcinoma (HCC). However, the mechanism by which HBV contributes to the development of HCC remains to be further explored. HBV-encoded miR-3 (HBV-miR-3) is a newly discovered microRNA that can affect the replication of HBV, but its influence on host genes is unclear. The tumor suppressor phosphatase and tensin homolog (PTEN) is expressed at low levels in most cancer cells. How HBV-miR-3 acts on PTEN to induce tumorigenesis has not been clarified.

Materials and Methods

PTEN protein expression was evaluated in HBV-miR-3-transfected cells and HBV-related liver cancer and paracancerous tissues. A luciferase reporter assay was employed to identify the HBV-miR-3 binding site on the 3ʹ-untranslated region (3ʹ-UTR) of PTEN. Cell apoptosis was assessed by flow cytometry. Cell proliferation was evaluated by colony formation assays. Transwell assays were used to detect cancer cell invasion.

Results

HBV-miR-3 was identified only in HBV-replicating HCC cells and HBV-infected patients. HBV-miR-3 expression in liver cancer tissues was higher than that in paracancerous tissues, and the corresponding PTEN expression was significantly decreased. Wild-type HBV-miR-3 bound to the 3ʹ-UTR of PTEN and downregulated its protein expression in a dose-dependent manner. Moreover, the inhibition of HBV-miR-3 rescued PTEN protein expression. Furthermore, HBV-miR-3 reduced liver cancer cell apoptosis, enhanced cell invasion, and promoted cell proliferation.

Conclusion

HBV-miR-3 binds to the 3ʹ-UTR of PTEN mRNA and downregulates PTEN protein expression, thereby reducing cell apoptosis and enhancing cell invasion and proliferation. These results indicate that HBV-miR-3 contributes to the development of HBV-related HCC and may be a therapeutic target for this cancer.

Molecular interactions and functions of IL-32

IL-32 is a multifaceted cytokine associated with several diseases and inflammatory conditions. Its expression is induced in response to cellular stress such as hypoxia, infections, and pro-inflammatory cytokines. IL-32 can be secreted from cells and can induce the production of pro-inflammatory cytokines from several cell types but are also described to have anti-inflammatory functions. The intracellular form of IL-32 is shown to play an important role in various cellular processes, including the defense against intracellular bacteria and viruses and in modulation of cell metabolism. In this review, we discuss current literature on molecular interactions of IL-32 with other proteins. We also review data on the role of intracellular IL-32 as a metabolic regulator and its role in antimicrobial host defense.

The Interplay Between Viral-Derived miRNAs and Host Immunity During Infection

MicroRNAs are short non-coding RNAs that play a crucial role in the regulation of gene expression during cellular processes. The host-encoded miRNAs are known to modulate the antiviral defense during viral infection. In the last decade, multiple DNA and RNA viruses have been shown to produce miRNAs known as viral miRNAs (v-miRNAs) so as to evade the host immune response. In this review, we highlight the origin and biogenesis of viral miRNAs during the viral lifecycle. We also explore the role of viral miRNAs in immune evasion and hence in maintaining chronic infection and disease. Finally, we offer insights into the underexplored role of viral miRNAs as potential targets for developing therapeutics for treating complex viral diseases.

Immunomodulatory roles of human herpesvirus-encoded microRNA in host-virus interaction

Human herpesviruses (HHV) are large, double stranded, DNA viruses with high seroprevalence across the globe. Clinical manifestation of primary HHV infection resolve shortly, however, this period is prolonged in immunocompromised patients or individuals with suppressed immunity. Examining molecular mechanisms of HHV-encoded virulence factors can provide finer details of HHV-host interaction. A unique genetic feature of most members of HHV is that they encode multiple microRNAs (miR). In this review, I will provide mechanistic insights into the immunomodulatory functions of herpesvirus-encoded viral miR (v-miR) that favor viral persistence and spread by ingenious immune evasion schemes. Similar to host miR, v-miR can simultaneously regulate expression of multiple transcripts including host- and virus-derived. V-miRs, by virtue of their direct interaction with various transcripts, can regulate expression of critical components of host innate and adaptive immune system. V-miRs are also exported through exosomal route and gain entry into various cells even at distant sites, thereby allowing HHV to manipulate cellular and tissue immunity. Targeting v-miR may serve as a novel and promising therapeutic candidate to mitigate HHV-mediated clinical manifestations.

HCMV miRNA Targets Reveal Important Cellular Pathways for Viral Replication, Latency, and Reactivation

It is now well appreciated that microRNAs (miRNAs) play a critical role in the lifecycles of many herpes viruses. The human cytomegalovirus (HCMV) replication cycle varies significantly depending on the cell type infected, with lytic replication occurring in fully-differentiated cells such as fibroblasts, endothelial cells, or macrophages, and latent infection occurring in less-differentiated CD14+ monocytes and CD34+ hematopoietic progenitor cells where viral gene expression is severely diminished and progeny virus is not produced. Given their non-immunogenic nature and their capacity to target numerous cellular and viral transcripts, miRNAs represent a particularly advantageous means for HCMV to manipulate viral gene expression and cellular signaling pathways during lytic and latent infection. This review will focus on our current knowledge of HCMV miRNA viral and cellular targets, and discuss their importance in lytic and latent infection, highlight the challenges of studying HCMV miRNAs, and describe how viral miRNAs can help us to better understand the cellular processes involved in HCMV latency.

The Biology and Role of Interleukin-32 in Tuberculosis

Tuberculosis, caused by Mycobacterium tuberculosis, remains a leading cause of morbidity and mortality globally, with nearly 10.4 million new cases of incidence and over 1.7 million deaths annually. Drug-resistant M. tuberculosis strains, especially multidrug-resistant or extensively drug-resistant strains, have further intensified the problem associated with tuberculosis control. Host-directed therapy is a promising alternative for tuberculosis control. IL-32 is increasingly recognized as an important host molecule against tuberculosis. In this review, we highlight the proinflammatory properties of IL-32 and the mode of action of IL-32 in mycobacterial infections to inspire the development of novel immunity-based countermeasures and host-directed therapies against tuberculosis.

Human cytomegalovirus-encoded miR-UL112 contributes to HCMV-mediated vascular diseases by inducing vascular endothelial cell dysfunction

Human cytomegalovirus (HCMV) infection has been linked to the pathogenesis of vasculopathy by inducing dysfunction of vascular cells such as endothelial cells. Hcmv-miR-UL112 is the most well-characterized HCMV-encoded microRNA occurring in the plasma of patients with cardiovascular diseases such as hypertension, while the specific underlying pathophysiological mechanisms are yet to be defined. The current study investigated the effect of hcmv-miR-UL112 on the growth and proliferation of human umbilical vascular endothelial cells (HUVECs); it might also be associated with signaling pathways. An adenovirus vector was designed and synthesized to stably express hcmv-miR-UL112 in HUVECs. Cell Counting Kit-8 results showed that ectopically expressed hcmv-miR-UL112 can significantly increase the proliferation of HUVECs (p < 0.05). Flow cytometry revealed that the S-phase fraction in the cell cycle analysis was raised significantly after overexpression of hcmv-miR-UL112 (p < 0.05). Gene expression profile analysis, using the microarray technology, revealed 303 up-regulated and 62 down-regulated genes in HUVECs by comparing the AD-hcmv-miR-UL112-infected and control groups (p < 0.05 and > 2 fold change). Kyoto Encyclopedia of Genes and Genomes and Reactome Pathway, chosen as the functional annotation categories, were affected by hcmv-miR-UL112 adenovirus vector. The significantly altered pathways mainly include the mitogen-activated protein kinase signaling pathway, cell adhesion molecules, chemokine signaling pathway, cytokine-cytokine receptor interaction, circadian rhythm-mammal, mineral absorption, protein processing in the endoplasmic reticulum, proximal tubule bicarbonate reclamation, vasopressin-regulated water reabsorption, and arachidonic acid metabolism. In conclusion, hcmv-miR-UL112 could serve as a potential biomarker, and the miRNA-mediated regulation of signaling pathways might play significant roles in the physiological effects of hcmv-associated diseases.

Modulation of the NFκb Signalling Pathway by Human Cytomegalovirus

Many viruses trigger innate and adaptive immune responses and must circumvent the negative consequences to successfully establish infection in their hosts. Human Cytomegalovirus (HCMV) is no exception, and devotes a significant portion of its coding capacity to genes involved in immune evasion. Activation of the NFκB signalling pathway by viral binding and entry results in induction of antiviral and pro-inflammatory genes that have significant negative effects on HCMV infection. However, NFκB signalling stimulates transcription from the Major Immediate Early Promoter (MIEP) and pro-inflammatory signalling is crucial for cellular differentiation and viral reactivation from latency. Accordingly, HCMV encodes proteins that act to both stimulate and inhibit the NFκB signalling pathway. In this Review we will highlight the complex interactions between HCMV and NFκB, discussing the known agonists and antagonists encoded by the virus and suggest why manipulation of the pathway may be critical for both lytic and latent infections.

Human cytomegalovirus miR-US4-5p promotes apoptosis via downregulation of p21-activated kinase 2 in cultured cells

The human cytomegalovirus (HCMV) encodes ≥26 microRNAs (miRNAs). These miRNAs are utilized by HCMV to regulate its own genes in addition to the genes of the host cell, during infection. The present study first identified p21‑activated kinase 2 (PAK2) as a target of hcmv‑miR‑US4‑5p, via hybrid polymerase chain reaction, which was further verified using a luciferase reporter assay. The protein expression level of PAK2, detected via western blotting, was demonstrated to be directly downregulated by overexpression of hcmv‑miR‑US4‑5p in HEK293, HELF and THP‑1 cells. Furthermore, it was demonstrated that the PAK2 protein level in naturally infected HELF cells was gradually decreased at 24, 48 and 72 h post infection with increased hcmv‑miR‑US4‑5p expression. The use of PAK2‑specific small interfering RNA and an inhibitor for hcmv‑miR‑US4‑5p, demonstrated that the promotion of apoptosis by hcmv‑miR‑US4‑5p in these cells was specifically mediated via inhibition of PAK2 expression. These results indicated that hcmv‑miR‑US4‑5p may exhibit this activity during natural HCMV infection, in order to establish a balance between the host cell and virus.

How does cytomegalovirus factor into diseases of aging and vaccine responses, and by what mechanisms?

Cytomegalovirus (CMV) is an important pathogen for both clinical and population settings. There is a growing body of research implicating CMV in multiple health outcomes across the life course. At the same time, there is mounting evidence that individuals living in poverty are more likely to be exposed to CMV and more likely to experience many of the chronic conditions for which CMV has been implicated. Further research on the causal role of CMV for health and well-being is needed. However, the strong evidence implicating CMV in type 2 diabetes, autoimmunity, cancer, cardiovascular disease, vaccination, and age-related alterations in immune function warrants clinical and public health action. This imperative is even higher among individuals living in socioeconomically disadvantaged settings and those exposed to high levels of chronic psychosocial stress.

Herpesvirus microRNAs for use in gene therapy immune-evasion strategies

Transplantation of allogeneic cells as well as of genetically corrected autologous cells are potent approaches to restore cellular functions in patients suffering from genetic diseases. The recipient's immune responses against non-self-antigens may compromise the survival of the grafted cells. Recipients of the graft may therefore require lifelong treatment with immunosuppressive drugs. An alternative approach to reduce graft rejection could involve the use of immune-evasion molecules. Expression of such molecules in cells of the graft may subvert recognition by the host's immune system. Viruses in particular are masters of exploitation and modulation of their hosts immune response. The Herpesviridae family provides a proof of concept for this as these viruses are capable to establish latency and a lifelong persistence in the infected hosts. While several viral proteins involved in immune evasion have been characterized, the Herpesviridae also encode a multitude of viral microRNA (miRNAs). Several of these miRNAs have been demonstrated to reduce the sensitivity of the infected cells to the destructive action of the host's immune cells. In this review, the miRNAs of some common herpesviruses that are associated with immune modulation will be discussed with a focus on their potential use in strategies aiming at generating non-immunogenic cells for transplantation.

The Role of HCMV and HIV-1 MicroRNAs: Processing, and Mechanisms of Action during Viral Infection

Viruses infect host cells releasing their genome (DNA or RNA) containing all information needed to replicate themselves. The viral genome takes control of the cells and helps the virus to evade the host immune system. Some viruses alter the functions of infected cells without killing them. In some cases infected cells lose control over normal cell proliferation and becomes cancerous. Viruses, such as HCMV and HIV-1, may leave their viral genome in the host cells for a certain period (latency) and begin to replicate when the cells are stressed causing diseases. HCMV and HIV-1 have developed multiple strategies to avoid recognition and elimination by the host’s immune system. These strategies rely on viral products that mimic specific components of the host cells to prevent immune recognition of virally infected cells. In addition to viral proteins, viruses encode short non-coding RNAs (vmiRNAs) that regulate both viral and host cellular transcripts to favor viral infection and actively curtail the host’s antiviral immune response. In this review, we will give an overview of the general functions of microRNAs generated by HCMV and HIV-1, their processing and interaction with the host’s immune system.

Human Cytomegalovirus MicroRNAs miR-US5-1 and miR-UL112-3p Block Proinflammatory Cytokine Production in Response to NF-κB-Activating Factors through Direct Downregulation of IKKα and IKKβ

Emerging evidence indicates that human cytomegalovirus (HCMV) manipulates host cell signaling pathways using both proteins and noncoding RNAs. Several studies have shown that HCMV induces NF-κB signaling early in infection, resulting in the induction of antiviral proinflammatory cytokines with a subsequent reduction of these cytokines late in infection. The mechanism for late cytokine reduction is unknown. In this study, we show that HCMV microRNAs (miRNAs) miR-US5-1 and miR-UL112-3p target the IκB kinase (IKK) complex components IKKα and IKKβ to limit production of proinflammatory cytokines in response to interleukin 1β (IL-1β) and tumor necrosis factor alpha (TNF-α). Transfection of miR-UL112-3p and miR-US5-1 mimics reduced endogenous IKKα and IKKβ protein levels, and site-directed mutagenesis of the 3' untranslated regions (UTRs) identified the binding sites for each miRNA. Infection with mutant viruses lacking these miRNAs resulted in increased levels of IKKα and IKKβ proteins, an impaired ability to control NF-κB signaling at late times of lytic infection, and increased production of proinflammatory cytokines compared to wild-type virus in cell types relevant to HCMV infection in vivo These phenotypes were rescued by preexpression of miR-US5-1 and miR-UL112-3p in infected cells or by a miR-US5-1/miR-UL112-3p double mutant virus that expresses short hairpin RNAs (shRNAs) targeting IKKα and IKKβ, demonstrating the gene specificity of the miRNAs. These observations describe a mechanism through which HCMV miRNAs expressed late in the infectious cycle downregulate proinflammatory cytokine production to create a cellular proviral environment.IMPORTANCE Human cytomegalovirus (HCMV) is a significant cause of morbidity and mortality in transplant recipients and causes hearing loss and mental retardation when acquired congenitally. Initial events during HCMV infection result in the activation of NF-κB signaling, which culminates in the production of IL-6, CCL5, and TNF-α. Several viruses have developed mechanisms to block the antiviral effects of these cytokines. We show here that two HCMV miRNAs, miR-US5-1 and miR-UL112-3p, specifically downregulate IKKα and IKKβ signaling factors necessary to propagate NF-κB signaling and subsequent IL-6, CCL5, and TNF-α production. Regulation of these proinflammatory cytokines during lytic infection and during latency is critical to viral survival in the host.

The role of microRNAs in respiratory viral infection: friend or foe?

MicroRNAs (miRNAs) have emerged as a class of regulatory RNAs in host-pathogen interactions. Aberrant miRNA expression seems to play a central role in the pathology of several respiratory viruses, promoting development and progression of infection. miRNAs may thus serve as therapeutic and prognostic factors for respiratory viral infectious disease caused by a variety of agents. We present a comprehensive review of recent findings related to the role of miRNAs in different respiratory viral infections and discuss possible therapeutic opportunities aiming to attenuate the burden of viral infections. Our review supports the emerging concept that cellular and viral-encoded miRNAs might be broadly implicated in human respiratory viral infections, with either positive or negative effects on virus life cycle. Copyright © 2016 John Wiley & Sons, Ltd.

Human cytomegalovirus miR-UL112-1 promotes the down-regulation of viral immediate early-gene expression during latency to prevent T-cell recognition of latently infected cells

Human cytomegalovirus, a member of the herpesvirus family, can cause significant morbidity and mortality in immune compromised patients resulting from either primary lytic infection or reactivation from latency. Latent infection is associated with a restricted viral transcription programme compared to lytic infection which consists of defined protein coding RNAs but also includes a number of virally encoded microRNAs (miRNAs). One of these, miR-UL112-1, is known to target the major lytic IE72 transcript but, to date, a functional role for miR-UL112-1 during latent infection has not been shown. To address this, we have analysed latent infection in myeloid cells using a virus in which the target site for miR-UL112-1 in the 3' UTR of IE72 was removed such that any IE72 RNA present during latent infection would no longer be subject to regulation by miR-UL112-1 through the RNAi pathway. Our data show that removal of the miR-UL112-1 target site in IE72 results in increased levels of IE72 RNA in experimentally latent primary monocytes. Furthermore, this resulted in induction of immediate early (IE) gene expression that is detectable by IE-specific cytotoxic T-cells (CTLs); no such CTL recognition of monocytes latently infected with wild-type virus was observed. We also recapitulated these findings in the more tractable THP-1 cell line model of latency. These observations argue that an important role for miR-UL112-1 during latency is to ensure tight control of lytic viral immediate early (IE) gene expression thereby preventing recognition of latently infected cells by the host's potent pre-existing anti-viral CTL response.

Virus-derived small RNAs in the penaeid shrimp Fenneropenaeus chinensis during acute infection of the DNA virus WSSV

Small interfering RNAs (siRNAs) and microRNAs (miRNAs) are two classes of small RNAs (sRNAs) that are critical for virus-host interplay via the RNA interference (RNAi) pathway. One virus-derived siRNA and numerous miRNAs has been reported for the double-stranded DNA virus white spot syndrome virus (WSSV), however, the expression profiles of these different types of sRNAs have not been assessed. Here, by sequencing the sRNAs and mRNAs of WSSV-infected Chinese shrimp (Fenneropenaeus chinensis), we found that the viral transcripts were universally targeted by WSSV-derived siRNAs, supporting a pivotal role for RNAi in the anti-viral immunity of shrimp. The genesis of WSSV-derived siRNAs was associated with long RNA structures. Moreover, by separating miRNAs from siRNAs, 12 WSSV miRNAs were identified. Investigation of conserved viral miRNA targets in different host species indicated the involvement of viral miRNAs in host immune responses. Collectively, our data provide new insights into the role of the RNAi pathway in the interplay between DNA viruses and crustaceans.

The Role of microRNAs in the Pathogenesis of Herpesvirus Infection

MicroRNAs (miRNAs) are small non-coding RNAs important in gene regulation. They are able to regulate mRNA translation through base-pair complementarity. Cellular miRNAs have been involved in the regulation of nearly all cellular pathways, and their deregulation has been associated with several diseases such as cancer. Given the importance of microRNAs to cell homeostasis, it is no surprise that viruses have evolved to take advantage of this cellular pathway. Viruses have been reported to be able to encode and express functional viral microRNAs that target both viral and cellular transcripts. Moreover, viral inhibition of key proteins from the microRNA pathway and important changes in cellular microRNA pool have been reported upon viral infection. In addition, viruses have developed multiple mechanisms to avoid being targeted by cellular microRNAs. This complex interaction between host and viruses to control the microRNA pathway usually favors viral infection and persistence by either reducing immune detection, avoiding apoptosis, promoting cell growth, or promoting lytic or latent infection. One of the best examples of this virus-host-microRNA interplay emanates from members of the Herperviridae family, namely the herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2), human cytomegalovirus (HCMV), human herpesvirus 8 (HHV-8), and the Epstein–Barr virus (EBV). In this review, we will focus on the general functions of microRNAs and the interactions between herpesviruses, human hosts, and microRNAs and will delve into the related mechanisms that contribute to infection and pathogenesis.

Pathogens Use and Abuse MicroRNAs to Deceive the Immune System

Emerging evidence has demonstrated that microRNAs (miRs) play a role in the survival and amplification of viruses, bacteria and other pathogens. There are various ways in which pathogens can benefit from miR-directed alterations in protein translation and signal transduction. Members of the herpesviridae family have previously been shown to encode multiple miRs, while the production of miRs by viruses like HIV-1 remained controversial. Recently, novel techniques have facilitated the elucidation of true miR targets by establishing miR-argonaute association and the subsequent interactions with their cognate cellular mRNAs. This, in combination with miR reporter assays, has generated physiologically relevant evidence that miRs from the herpesviridae family have the potential to downregulate multiple cellular targets, which are involved in immune activation, cytokine signaling and apoptosis. In addition, viruses and bacteria have also been linked to the induction of host cellular miRs, which have the capacity to mitigate immune activation, cytokine signaling and apoptosis. Interfering with miR expression may be clinically relevant. In the case of hepatitis C infection, the cellular miR-122 is already targeted therapeutically. This not only exemplifies how important miRs can be for the survival of specific viruses, but it also delineates the potential to use miRs as drug targets. In this paper we will review the latest reports on viruses and bacteria that abuse miR regulation for their benefit, which may be of interest in the development of miR-directed therapies.

Human cytomegalovirus encoded microRNAs: hitting targets

Human cytomegalovirus (HCMV) infection is of particular concern in immunodeficient individuals notably transplant recipients, leading to increased morbidity and mortality. HCMV is predicted to encode multiple microRNAs (miRNAs) and several have been characterized in vitro. Furthermore, these miRNAs have been shown to target human and viral mRNAs. Pathways involved in human cellular targets have key roles in vesicle trafficking, immune evasion and cell cycle control. This demonstration of viral miRNA targets provides novel insights into viral pathogenesis. This review details the evidence for the existence of HCMV-encoded miRNA and their targets. HCMV miRNA in blood and other tissues is a potential diagnostic tool and blocking the effects of specific HCMV-encoded miRNA with sequence specific antagomirs is a potential new therapy.

Small RNAs growing tall: miRNAs as drug targets in herpesvirus infections

Herpesviruses establish life-long latent infections. They can cause severe morbidity and significant mortality particularly in immunocompromised hosts. Several are associated with cancers. Most express large amounts of microRNAs during latent or lytic infection. There is increasing evidence that these small RNA molecules play important roles in many aspects of pathogenesis, including lytic and latent infections, immune evasion and tumorigenesis. Therapies targeting microRNAs have already successfully made it into clinics, for example, to treat hepatitis C virus (HCV) infection. In this review, we will focus on regulatory functions of herpesvirus miRNAs that may be suitable for antiviral intervention.

Human cytomegalovirus miR-UL36-5p inhibits apoptosis via downregulation of adenine nucleotide translocator 3 in cultured cells

Human cytomegalovirus (HCMV) encodes at least 26 microRNAs (miRNA). These miRNAs are utilized by HCMV to regulate its own genes as well as the genes of the host cell during infection. It has been reported that a cellular gene, solute carrier family 25, member 6 (SLC25A6), which is also designated adenine nucleotide translocator 3 (ANT3), was identified as a candidate target of hcmv-miR-UL36-5p by hybrid PCR. In this study, ANT3 was further demonstrated to be a direct target of hcmv-miR-UL36-5p by luciferase reporter assays. The expression level of ANT3 protein was confirmed, by western blotting, to be directly downregulated by overexpression of hcmv-miR-UL36-5p in HEK293 cells, U373 cells and HELF cells. Moreover, HCMV-infected cells showed a decrease in the ANT3 protein level. Using ANT3-specific small interfering RNA (siRNA) and an inhibitor for hcmv-miR-UL36-5p, it was shown that inhibition of apoptosis by hcmv-miR-UL36-5p in these cells specifically occurred via inhibition of ANT3 expression. These results imply that hcmv-miR-UL36-5 may play the same role during actual HCMV infection in order to establish a balance between the host cell and the virus.

Human cytomegalovirus microRNA miR-US25-1-5p inhibits viral replication by targeting multiple cellular genes during infection

MicroRNAs (miRNAs) play important roles in regulating various cellular processes in plants, animals, and viruses. This mechanism is also utilized by human cytomegalovirus (HCMV) in the process of infection and pathogenesis. The HCMV-encoded miRNA, hcmv-miR-US25-1-5p, was highly expressed during lytic and latent infections, and was found to inhibit viral replication. Identification of functional target genes of this microRNA is important in that it will enable a better understanding of the function of hcmv-miR-US25-1-5p during HCMV infection. In the present study, 35 putative cellular transcript targets of hcmv-miR-US25-1-5p were identified. Down-regulation of the targets YWHAE, UBB, NPM1, and HSP90AA1 by hcmv-miR-US25-1-5p was validated by luciferase reporter assay and Western blot analysis. In addition, we showed that hcmv-miR-US25-1-5p could inhibit viral replication by interacting with these targets, the existence of which may impact virus replication directly or indirectly.

The human cytomegalovirus non-coding Beta2.7 RNA as a novel therapeutic for Parkinson's disease--Translational research with no translation

Human cytomegalovirus (HCMV) encodes abundant numbers of microRNAs (miRNAs) and other non-coding RNAs (ncRNAs) whose functions are presently under intense investigation. In this chapter, we discuss the function of one of the more well characterised virus-encoded ncRNAs, derived from the viral major early gene (Beta2.7). This RNA plays an anti-apoptotic role during infection by directly interacting with mitochondrial complex I to help maintain high levels of ATP production and by preventing the stress induced re-localisation of retinoid/interferon-induced mortality-19 protein, GRIM-19. We then go on to describe how an 800 nucleotide sub-domain of the Beta2.7 transcript, p137, has been exploited in the development of a novel therapeutic for the treatment of Parkinson's disease.

Human cytomegalovirus miR-US33-5p inhibits viral DNA synthesis and viral replication by down-regulating expression of the host Syntaxin3

During infection with human cytomegalovirus (HCMV), overexpression of hcmv-miR-US33 can inhibit the lytic viral replication and down-regulate US29 mRNA. However, it remains unknown whether inhibition of viral replication by miR-US33 is mediated by down-regulation of expression of US29 or another host gene. Here, we identified the host gene Syntaxin3 (STX3) to be a direct target of hcmv-miR-US33-5p using Hybrid-PCR and luciferase-reporter assays. It was further demonstrated that the levels of STX3 protein were down-regulated in hcmv-miR-US33-5p-overexpressing cells. Experiments with STX3-specific siRNA, or with an inhibitor of hcmv-miR-US33-5p confirmed that hcmv-miR-US33-5p-mediated inhibition of HCMV DNA synthesis and of viral replication are specifically mediated by down-regulation of STX3 expression.

Detection of circulating hcmv-miR-UL112-3p in patients with glioblastoma, rheumatoid arthritis, diabetes mellitus and healthy controls

Background

microRNAs (miRNA) are 18–22 nucleotides long non-coding RNAs that regulate gene expression at a post-transcriptional level. Human cytomegalovirus (HCMV) encodes at least 26 known mature miRNAs. hcmv-miR-UL112-3p (miR-UL112-3p) is the most well characterized HCMV miRNA, which is suggested to play role in establishment and maintenance of viral latency. Elevated miR-UL112-3p levels have been reported to be present in plasma of patients with hypertension.

Objectives

In this study, we aimed to quantify miR-UL112-3p levels in the plasma/serum of patients with Diabetes Mellitus (DM; from the DIGAMI-2 cohort), Glioblastoma multiforme (GBM), Rheumatoid Arthritis (RA) and Healthy Controls (HC).

Study Design

Total RNA was isolated from plasma/serum samples of 87 patients and controls, a TaqMan miRNA assay was performed to detect miR-UL112-3p and the copy numbers were normalized to 10 ng of total RNA. HCMV IgG and IgM were analysed using ELISA.

Results

HCMV miR-UL112-3p was detected in 14/27 (52%) of DM, 5/20 (25%) of GBM, 1/20 (5%) of RA patients and in 2/20 (10%) of HC, respectively. Anti-HCMV IgG was detected in 85%, 65%, 75% of patients and 70% of HC, respectively. Anti-HCMV IgM was found only in one GBM patient of 87 examined patients and controls.

Conclusions

A higher prevalence of miR-UL112-3p was detected in DM and GBM patients than in RA patients and HC. Elevated levels of miR-UL112-3p and higher prevalence of HCMV IgG were observed in DM patients. Whether the presence of circulating miR-UL112-3p denotes a biomarker of HCMV latency or active replication in patients warrants further investigation.

The use of microRNA by human viruses: lessons from NK cells and HCMV infection

Depending on ethnicity and on social conditions, between 40 and 90 % of the population is infected with human cytomegalovirus (HCMV). In immunocompetent patients, the virus may cause an acute disease and then revert to a state of latency, which enables its coexistence with the human host. However, in cases of immunosuppression or in neonatal infections, HCMV can cause serious long-lasting illnesses. HCMV has developed multiple mechanisms in order to escape its elimination by the immune system, specifically by two killer cell types of the adaptive and the innate immune systems; cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, respectively. Another fascinating aspect of HCMV is that like other highly developed herpesviruses, it expresses its own unique set of microRNAs. Here, we initially describe how the activity of NK cells is regulated under normal conditions and during infection. Then, we discuss what is currently known about HCMV microRNA-mediated interactions, with special emphasis on immune modulation and NK cell evasion. We further illustrate the significant modulation of cellular microRNAs during HCMV infection. Although, the full target spectrum of HCMV microRNAs is far from being completely elucidated, it can already be concluded that HCMV uses its "multitasking" microRNAs to globally affect its own life cycle, as well as important cellular and immune-related pathways.

Codon usage bias in human cytomegalovirus and its biological implication

Human cytomegalovirus (HCMV) infection, a worldwide contagion, causes a serious disorder in infected individuals. Analysis of codon usage can reveal much molecular information about this virus. The effective number of codon (ENC) values, relative synonymous codon usage (RSCU) values, codon adaptation index (CAI), and nucleotide contents was investigated in approximately 160 coding sequences (CDS) among 17 human cytomegalovirus genomes using the software CodonW. Linear regression analysis and logistic regression were performed to explore the preliminary data. The results showed that, overall, HCMV genomes had low codon usage bias (mean ENC=47.619). However, the ENC of individual CDS varied widely and was distributed unevenly between host-related genes and viral-self-function genes (P=0.002, odds ratio (OR)=3.194), as did the GC content (P=0.016, OR=2.178). The ENC values correlated with CAI, GC content, and the nucleotide composing at the 3rd codon position (GC3s) (P<0.001). There was a significant variation in the codon preference that depended on the RSCU data. The predicted ENC curve suggested that mutational pressure, rather than natural selection, was one of the main factors that determined the codon usage bias in HCMV. Among 123 genes with known function, the genes related to viral self-replication and viral-host interaction showed different ENC and CAI values, and GC and GC3s contents. In conclusion, the detailed codon usage bias theoretically revealed information concerning HCMV evolution and could be a valuable additional parameter for HCMV gene function research.

Interleukin-32 isoforms: expression, interaction with interferon-regulated genes and clinical significance in chronically HIV-1-infected patients

Given the growing evidence for a role of interleukin-32 (IL-32) in the immune response to HIV-1 infection and its interplay with type I and III interferons (IFNs), we studied the gene expression of IL-32 isoforms (α and nonα) in untreated chronically HIV-1-infected patients and in gender- and age-matched healthy individuals. To further characterize both the anti-HIV properties of IL-32 and the cytokine's relationship with host antiviral innate immune responses, we evaluated whether IL-32 can induce ex vivo the expression of antiviral IFN-induced genes (ISGs), namely myxovirus resistance A (MxA), and apolipoprotein B mRNA-editing enzyme catalytic (APOBEC)3G and APOBEC3F. We also investigated whether in vivo IL-32 (α and nonα) mRNA levels were correlated with those of MxA and APOBEC3G/3F. Results indicated that IL-32 (α and nonα) mRNA levels were significantly higher in HIV-1-infected patients than in healthy individuals. Furthermore, IL-32 (α and nonα) mRNA levels correlated negatively with HIV RNA levels, but not with the CD4(+) T-cell count. Our ex vivo studies disclosed that ISGs mRNA levels were increased after IL-32γ treatment of peripheral blood mononuclear cells. Interestingly, significant positive correlations were found between transcript levels of both IL-32α and IL-32nonα and those of MxA and APOBEC3G/3F in untreated chronically HIV-1-infected patients. Overall, our results demonstrated that IL-32 isoforms are highly expressed during chronic HIV-1 infection and that IL-32 could have a central role in the antiviral immune response against HIV-1.