RSV P-protein impairs extrinsic apoptosis pathway in a macrophage-like cell line persistently infected with respiratory syncytial virus

Alveolar macrophages and airway hyperresponsiveness associated with respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is a ubiquitous pathogen of viral bronchiolitis and pneumonia in children younger than 2 years of age, which is closely associated with recurrent wheezing and airway hyperresponsiveness (AHR). Alveolar macrophages (AMs) located on the surface of the alveoli cavity are the important innate immune barrier in the respiratory tract. AMs are recognized as recruited airspace macrophages (RecAMs) and resident airspace macrophages (RAMs) based on their origins and roaming traits. AMs are polarized in the case of RSV infection, forming two macrophage phenotypes termed as M1-like and M2-like macrophages. Both M1 macrophages and M2 macrophages are involved in the modulation of inflammatory responses, among which M1 macrophages are capable of pro-inflammatory responses and M2 macrophages are capable of anti-proinflammatory responses and repair damaged tissues in the acute and convalescent phases of RSV infection. Polarized AMs affect disease progression through the alteration of immune cell surface phenotypes as well as participate in the regulation of T lymphocyte differentiation and the type of inflammatory response, which are closely associated with long-term AHR. In recent years, some progress have been made in the regulatory mechanism of AM polarization caused by RSV infection, which participates in acute respiratory inflammatory response and mediating AHR in infants. Here we summarized the role of RSV-infection-mediated AM polarization associated with AHR in infants.

Identification and host response interaction study of SARS-CoV-2 encoded miRNA-like sequences: an in silico approach

COVID-19, a global pandemic caused by an RNA virus named SARS-CoV-2 has brought the world to a standstill in terms of infectivity, casualty, and commercial plummet. RNA viruses can encode microRNAs (miRNAs) capable of modulating host gene expression, and with that notion, we aimed to predict viral miRNA like sequences of MERS-CoV, SARS-CoV and SARS-CoV-2, analyze sequence reciprocity and investigate SARS-CoV-2 encoded potential miRNA-human genes interaction using bioinformatics tools. In this study, we retrieved 206 SARS-CoV-2 genomes, executed phylogenetic analysis, and the selected reference genome (MT434792.1) exhibited about 99% similarities among the retrieved genomes. We predicted 402, 137, and 85 putative miRNAs of MERS-CoV (NC_019843.3), SARS-CoV (NC_004718.3), and SARS-CoV-2 (MT434792.1) genome, respectively. Sequence similarity was analyzed among 624 miRNAs which revealed that the predicted miRNAs of SARS-CoV-2 share a cluster with the clad of miRNAs from MERS-CoV and SARS-CoV. Only SARS-CoV-2 derived 85 miRNAs were encountered for target prediction and 29 viral miRNAs seemed to target 119 human genes. Moreover, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analysis suggested the involvement of respective genes in various pathways and biological processes. Finally, we focused on eight putative miRNAs influencing 14 genes that are involved in the adaptive hypoxic response, neuroinvasion and hormonal regulation, and tumorigenic progression in patients with COVID-19. SARS-CoV-2 encoded miRNAs may cause misexpression of some critical regulators and facilitate viral neuroinvasion, altered hormonal axis, and tumorigenic events in the human host. However, these propositions need validation from future studies.

Impact of Respiratory Syncytial Virus Infection on Host Functions: Implications for Antiviral Strategies

Respiratory syncytial virus (RSV) is one of the leading causes of viral respiratory tract infection in infants, the elderly, and the immunocompromised worldwide, causing more deaths each year than influenza. Years of research into RSV since its discovery over 60 yr ago have elucidated detailed mechanisms of the host-pathogen interface. RSV infection elicits widespread transcriptomic and proteomic changes, which both mediate the host innate and adaptive immune responses to infection, and reflect RSV's ability to circumvent the host stress responses, including stress granule formation, endoplasmic reticulum stress, oxidative stress, and programmed cell death. The combination of these events can severely impact on human lungs, resulting in airway remodeling and pathophysiology. The RSV membrane envelope glycoproteins (fusion F and attachment G), matrix (M) and nonstructural (NS) 1 and 2 proteins play key roles in modulating host cell functions to promote the infectious cycle. This review presents a comprehensive overview of how RSV impacts the host response to infection and how detailed knowledge of the mechanisms thereof can inform the development of new approaches to develop RSV vaccines and therapeutics.

Monocytes and Macrophages as Viral Targets and Reservoirs

Viruses manipulate cell biology to utilize monocytes/macrophages as vessels for dissemination, long-term persistence within tissues and virus replication. Viruses enter cells through endocytosis, phagocytosis, macropinocytosis or membrane fusion. These processes play important roles in the mechanisms contributing to the pathogenesis of these agents and in establishing viral genome persistence and latency. Upon viral infection, monocytes respond with an elevated expression of proinflammatory signalling molecules and antiviral responses, as is shown in the case of the influenza, Chikungunya, human herpes and Zika viruses. Human immunodeficiency virus initiates acute inflammation on site during the early stages of infection but there is a shift of M1 to M2 at the later stages of infection. Cytomegalovirus creates a balance between pro- and anti-inflammatory processes by inducing a specific phenotype within the M1/M2 continuum. Despite facilitating inflammation, infected macrophages generally display abolished apoptosis and restricted cytopathic effect, which sustains the virus production. The majority of viruses discussed in this review employ monocytes/macrophages as a repository but certain viruses use these cells for productive replication. This review focuses on viral adaptations to enter monocytes/macrophages, immune escape, reprogramming of infected cells and the response of the host cells.

MicroRNA 146-5p, miR-let-7c-5p, miR-221 and miR-345-5p are differentially expressed in Respiratory Syncytial Virus (RSV) persistently infected HEp-2 cells

Many viruses can establish non-cytolytic, chronic infections in host cells. Beyond the intrinsically interesting questions of how this long-term parasitism is achieved, persistently infected cells can be useful to study virus-host interactions. MicroRNAs (miRNAs) are a class of noncoding RNAs transcribed from the genomes of all multicellular organisms and some viruses. Individual miRNAs may regulate several hundred genes. In this research we have studied the expression of a selective group of host-cell encoded miRNAs, as expressed in a Respiratory Syncytial Virus (RSV) persistently infected HEp-2 cell line (HEp-2 + RSV-GFP). The RSV is a virus that does not encode miRNAs in its genome. Our study shows that Dicer is down regulated, miRNA's 146a-5p is strongly up-regulated and miRNAs 345-5p, let-7c-5p and miRNA's-221 are down-regulated in HEp-2 + RSV-GFP cells. Correspondingly, changes in the miRNA 146a-5p and he sequences of the reference genes are miRNA 345-5p respective miRNAs target proteins: HSP-70 and p21, were observed. Thus, RSV persistent viral infection induces unique patterns of miRNA's expression with relevance to how the virus regulates the host cell response to infection.

The innate immune response to RSV: Advances in our understanding of critical viral and host factors

Respiratory syncytial virus (RSV) causes mild to severe respiratory illness in humans and is a major cause of hospitalizations of infants and the elderly. Both the innate and the adaptive immune responses contribute to the control of RSV infection, but despite successful viral clearance, protective immunity against RSV re-infection is usually suboptimal and infections recur. Poor understanding of the mechanisms limiting the induction of long-lasting immunity has delayed the development of an effective vaccine. The innate immune response plays a critical role in driving the development of adaptive immunity and is thus a crucial determinant of the infection outcome. Advances in recent years have improved our understanding of cellular and viral factors that influence the onset and quality of the innate immune response to RSV. These advances include the identification of a complex system of cellular sensors that mediate RSV detection and stimulate transcriptome changes that lead to virus control and the discovery that cell stress and apoptosis participate in the control of RSV infection. In addition, it was recently demonstrated that defective viral genomes (DVGs) generated during RSV replication are the primary inducers of the innate immune response. Newly discovered host pathways involved in the innate response to RSV, together with the potential generation of DVG-derived oligonucleotides, present various novel opportunities for the design of vaccine adjuvants able to induce a protective response against RSV and similar viruses.

Human Coronaviruses: A Review of Virus-Host Interactions

Human coronaviruses (HCoVs) are known respiratory pathogens associated with a range of respiratory outcomes. In the past 14 years, the onset of severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV) have thrust HCoVs into spotlight of the research community due to their high pathogenicity in humans. The study of HCoV-host interactions has contributed extensively to our understanding of HCoV pathogenesis. In this review, we discuss some of the recent findings of host cell factors that might be exploited by HCoVs to facilitate their own replication cycle. We also discuss various cellular processes, such as apoptosis, innate immunity, ER stress response, mitogen-activated protein kinase (MAPK) pathway and nuclear factor kappa B (NF-κB) pathway that may be modulated by HCoVs.