Implications For Viral Infections Research Articles

RNA structure: implications in viral infections and neurodegenerative diseases

AbstractRNA is an intermediary between DNA and protein, a catalyzer of biochemical reactions, and a regulator of genes and transcripts. RNA structures are essential for complicated functions. Recent years have witnessed rapid advancements in RNA secondary structure probing techniques. These technological strides provided comprehensive insights into RNA structures, which significantly contributed to our understanding of diverse cellular regulatory processes, including gene regulation, epigenetic regulation, and post-transactional regulation. Meanwhile, they have facilitated the creation of therapeutic tools for tackling human diseases. Despite their therapeutic applications, RNA structure probing methods also offer a promising avenue for exploring the mechanisms of human diseases, potentially providing the key to overcoming existing research constraints and obtaining the in-depth information necessary for a deeper understanding of disease mechanisms.

Neutrophil Functional Heterogeneity and Implications for Viral Infections and Treatments.

Evidence suggests that neutrophils exert specialized effector functions during infection and inflammation, and that these cells can affect the duration, severity, and outcome of the infection. These functions are related to variations in phenotypes that have implications in immunoregulation during viral infections. Although the complexity of the heterogeneity of neutrophils is still in the process of being uncovered, evidence indicates that they display phenotypes and functions that can assist in viral clearance or augment and amplify the immunopathology of viruses. Therefore, deciphering and understanding neutrophil subsets and their polarization in viral infections is of importance. In this review, the different phenotypes of neutrophils and the roles they play in viral infections are discussed. We also examine the possible ways to target neutrophil subsets during viral infections as potential anti-viral treatments.

Impact of the COVID-19 pandemic on staging at presentation of patients with invasive melanoma.

e21579 Background: The COVID-19 pandemic has impacted cancer care beyond the direct implications of viral infection. Delays in presentation and diagnosis may lead to more advanced disease and worse patient outcomes. We evaluated the impact of the pandemic on patients (pts) with melanoma (mel). Methods: A single-institution, retrospective comparison of pts with newly diagnosed invasive mel or metastatic recurrence prior to (pre-cohort, n = 246) and after (post-cohort, n = 246) declaration of the COVID-19 pandemic on March 11, 2020. 492 pts were evaluated between March 1, 2019 and January 12, 2021. Key variables collected included demographics, pathology, stage at diagnosis, surgical management, receipt of adjuvant or systemic therapy, and follow up. Categorical variables were compared using the two-sided Fisher’s exact test, continuous variables were compared using the two-sided Wilcoxon rank sum test, and survival endpoints were evaluated with the Kaplan-Meier method. This study was exempt from review by the IRB. Results: 200 (81.3%) pts presented with early-stage disease and 46 (18.7%) pts presented with metastatic disease in the post-cohort, compared to 209 (85%) and 37 (15%) pts in the pre-cohort, respectively. In the post-cohort there was a significant decrease in stage I pts (28.5% vs 40.7%, p = 0.006), a significant increase in stage III pts (30.5% vs 21.1%, p = 0.023), and a significant increase in pts with metastatic recurrence (7.7% vs 3.3%, p = 0.046) compared to the pre-cohort. There was also a significant increase in pts with brain metastases (BM) in the post-cohort (6.5% vs 1.6%, p = 0.010). For pts with early-stage disease, there was a significant increase in median Breslow depth (2.0 vs 1.4 mm, p = 0.047) and mitotic rate > 1 (78.1% vs 66%, p = 0.008) in the post-cohort. There were trends toward increased ulceration, lymphovascular/perineural invasion, and microsatellite presence. Pts receiving adjuvant therapy in the post-cohort were significantly more likely to receive oral targeted therapy (37.6% vs 27.5%) compared to IV immunotherapy (62.4% vs 72.5%), p = 0.034, perhaps reflecting an attempt to minimize in-person visits. There was not a significant difference between the 2 groups in the type of systemic therapy administered in the metastatic setting. Median progression-free and overall survival were not reached due to a limited number of events in each arm. Conclusions: There was a significant decrease in pts with stage I mel along with a significant increase in pts with stage III mel, metastatic recurrence, and BMs presenting to our institution during the pandemic. Findings are likely related to delays from both the patient (to avoid interaction with the healthcare system - including primary care, dermatology, and oncology) and from the system itself, with some clinics potentially evaluating pts in a limited capacity. These data reaffirm the importance of early detection and evaluation of melanoma.

Interleukin-17A Facilitates Chikungunya Virus Infection by Inhibiting IFN-α2 Expression.

Interferons (IFNs) are the key components of innate immunity and are crucial for host defense against viral infections. Here, we report a novel role of interleukin-17A (IL-17A) in inhibiting IFN-α2 expression thus promoting chikungunya virus (CHIKV) infection. CHIKV infected IL-17A deficient (Il17a−/−) mice expressed a higher level of IFN-α2 and developed diminished viremia and milder footpad swelling in comparison to wild-type (WT) control mice, which was also recapitulated in IL-17A receptor-deficient (Il17ra−/−) mice. Interestingly, IL-17A selectively blocked IFN-α2 production during CHIKV, but not West Nile virus (WNV) or Zika virus (ZIKV), infections. Recombinant IL-17A treatment inhibited CHIKV-induced IFN-α2 expression and enhanced CHIKV replication in both human and mouse cells. We further found that IL-17A inhibited IFN-α2 production by modulating the expression of Interferon Regulatory Factor-5 (IRF-5), IRF-7, IFN-stimulated gene 49 (ISG-49), and Mx1 expression during CHIKV infection. Neutralization of IL-17A in vitro leads to the increase of the expression of these antiviral molecules and decrease of CHIKV replication. Collectively, these results suggest a novel function of IL-17A in inhibiting IFN-α2–mediated antiviral responses during CHIKV infection, which may have broad implications in viral infections and other inflammatory diseases.

TAM receptors: A phosphatidylserine receptor family and its implications in viral infections.

Phosphatidylserine (PS) is an anionic phospholipid that is usually localized in the inner leaflets of the plasma membrane. However, the enzyme scramblase catalyzes the externalization of PS on the outer leaflet of the plasma membrane during apoptosis or cellular stress. This event prompts the recognition of PS displaying cells by phagocytes leading to "apoptotic clearance." Multiple PS receptors (PSRs) mediate this process including members from the TAM (Tyro3, Axl, Mertk) receptor Tyrosine kinases (RTKs) by interacting with PS via bridging proteins like Gas6 and ProS1. Ironically, this network (PS/TAM) that evolved for boosting cellular health through clearance of apoptotic and necrotic cells, has been manoeuvred by pathogens and tumor cells using "apoptotic mimicry." Enveloped viruses, responsible for most of the lethal epidemics and pandemics including the current SARS-CoV2 outbreak, have employed apoptotic mimicry to their advantage. In the current chapter, we summarize the existing knowledge regarding the involvement of PS/Gas6, ProS1/TAM in facilitating infectivity in a diverse set of cell lines, animals as well as organoids. This network executes a largely proviral role in facilitating infection as seen with Zika, Ebola, Influenza and Dengue viruses. However, this response varies with strains and the cells infected, and in some cases, this same signaling displays an antiviral function. We also report multiple studies that have used neutralizing antibodies and small molecule inhibitors in successfully reducing viral replication and ameliorating pathogenicity. Knowledge about this unique signaling pathway and measures that can be taken to inhibit it is most valuable now given how enveloped viruses lead to plagues on the entire globe.

Promotion of Tumorigenesis and Clinical Implications of Viral Infection in Breast Cancer

The prevalence of breast cancer is rising worldwide. The main cause of death from breast cancer is distant metastasis, which occurs within 3 years after diagnosis in 10–15% of patients. The initiation and progression of breast cancer have been related to both external and internal factors, including viral infection. Human cytomegalovirus infection (HCMV) is common in breast cancer and metastases, and high tumor levels of HCMV appear to worsen outcomes. HCMV can increase the malignant behavior of tumor cells by modulating multiple cellular regulatory and signaling pathways and enhance the proliferation, survival, invasion, motility, and adhesion of tumor cells. Although HCMV seems to have an oncomodulatory role in breast cancer, definitive evidence for a causal role is lacking, and further studies are needed. The current review will discuss evidence that links viral infections to breast cancer.

Paramyxovirus fusion and entry: multiple paths to a common end.

The paramyxovirus family contains many common human pathogenic viruses, including measles, mumps, the parainfluenza viruses, respiratory syncytial virus, human metapneumovirus, and the zoonotic henipaviruses, Hendra and Nipah. While the expression of a type 1 fusion protein and a type 2 attachment protein is common to all paramyxoviruses, there is considerable variation in viral attachment, the activation and triggering of the fusion protein, and the process of viral entry. In this review, we discuss recent advances in the understanding of paramyxovirus F protein-mediated membrane fusion, an essential process in viral infectivity. We also review the role of the other surface glycoproteins in receptor binding and viral entry, and the implications for viral infection. Throughout, we concentrate on the commonalities and differences in fusion triggering and viral entry among the members of the family. Finally, we highlight key unanswered questions and how further studies can identify novel targets for the development of therapeutic treatments against these human pathogens.

Dendritic cells: Nearly 40 years later…

The immune system is probably one of the most complex cellular organizations in the body. Its complexity is not superfluous, but rather it is required to fulfill the complicated purpose of the immune system, namely: the recognition of the diverse repertoire of microorganisms and pathogens; the detection of neoplastic lesions originating from a range of tissues; and, while executing these tasks, the maintenance of peripheral tolerance by suppressing detrimental responses against healthy tissues. Since they were discovered by R. Steinman et al. nearly 40 years ago, dendritic cells (DCs) have emerged to be critical players in conducting the immune response to fulfill these roles. Here, we provide a general view on some aspects of DC immunology, highlighting the crucial role that R. Steinman's research in the DC field has played during all those years. This review will also give an outline on DC research in the particular aspects that represent the focus of research groups in Spain (recently organized as the DC.esp working group within SEI). Firstly, some of the subtypes of DC will be described, particularly thymic DC and their role on tolerance; then the DC role in tolerance will be examined, followed by their implications in viral infections. Finally, antigen targeting DCs will be reviewed taking into account the crucial contributions made by R. Steinman et al. This chapter will end by reviewing some DCs based therapies in viral infections.

The association of viral proteins with host cell dynein components during virus infection

After fusion with the cellular plasma membrane or endosomal membranes, viral particles are generally too large to diffuse freely within the crowded cytoplasm environment. Thus, they will never reach the cell nucleus or the perinuclear areas where replication or reverse transcription usually takes place. It has been proposed that many unrelated viruses are transported along microtubules in a retrograde manner using the cellular dynein machinery or, at least, some dynein components. A putative employment of the dynein motor in a dynein‐mediated transport has been suggested from experiments in which viral capsid proteins were used as bait in yeast two‐hybrid screens using libraries composed of cellular proteins and dynein‐associated chains were retrieved as virus‐interacting proteins. In most cases DYNLL1, DYNLT1 or DYNLRB1 were identified as the dynein chains that interact with viral proteins. The importance of these dynein–virus interactions has been supported, in principle, by the observation that in some cases the dynein‐interacting motifs of viral proteins altered by site‐directed mutagenesis result in non‐infective virions. Furthermore, overexpression of p50 dynamitin, which blocks the dynein–dynactin interaction, or incubation of infected cells with peptides that compete with viral polypeptides for dynein binding have been shown to alter the viral retrograde transport. Still, it remains to be proved that dynein light chains can bind simultaneously to incoming virions and to the dynein motor for retrograde transport to take place. In this review, we will analyse the association of viral proteins with dynein polypeptides and its implications for viral infection.

Magnetic nanoparticle-based isolation of endocytic vesicles reveals a role of the heat shock protein GRP75 in macromolecular delivery

An increased understanding of cellular uptake mechanisms of macromolecules remains an important challenge in cell biology with implications for viral infection and macromolecular drug delivery. Here, we report a strategy based on antibody-conjugated magnetic nanoparticles for the isolation of endocytic vesicles induced by heparan sulfate proteoglycans (HSPGs), key cell-surface receptors of macromolecular delivery. We provide evidence for a role of the glucose-regulated protein (GRP)75/PBP74/mtHSP70/mortalin (hereafter termed "GRP75") in HSPG-mediated endocytosis of macromolecules. GRP75 was found to be a functional constituent of intracellular vesicles of a nonclathrin-, noncaveolin-dependent pathway that was sensitive to membrane cholesterol depletion and that showed colocalization with the membrane raft marker cholera toxin subunit B. We further demonstrate a functional role of the RhoA GTPase family member CDC42 in this transport pathway; however, the small GTPase dynamin appeared not to be involved. Interestingly, we provide evidence of a functional role of GRP75 using RNAi-mediated down-regulation of GRP75 and GRP75-blocking antibodies, both of which inhibited macromolecular endocytosis. We conclude that GRP75, a chaperone protein classically found in the endoplasmic reticulum and mitochondria, is a functional constituent of noncaveolar, membrane raft-associated endocytic vesicles. Our data provide proof of principle of a strategy that should be generally applicable in the molecular characterization of selected endocytic pathways involved in macromolecular uptake by mammalian cells.

Spontaneous remission of spasms in West syndrome – implications of viral infection

On a database of the Japanese medical literature between 1970 and 2000, there were 29 patients with West syndrome showing spontaneous remission. In 25/29 (86%) of the patients, spontaneous remission was preceded by viral infections, among which exanthema subitum predominated. In 16/29 (55%), the spasms recurred a median of 2 months later. However, some of the remaining infants attained lasting remission of the spasms. This link between viral infections and spontaneous remission suggests immuno-inflammatory processes underlie West syndrome in certain patients. Better understanding of such mechanisms may lead to a new therapeutic approach to West syndrome.

Membrane fusion by an RGD‐containing sequence from the core protein VP3 of hepatitis A virus and the RGA‐analogue: Implications for viral infection

Membrane fusion by an RGD‐containing sequence from the core protein VP3 of hepatitis A virus and the RGA‐analogue: Implications for viral infection

Membrane fusion by an RGD-containing sequence from the core protein VP3 of hepatitis A virus and the RGA-analogue: implications for viral infection.

The interaction of an RGD-containing epitope from the hepatitis A virus VP3 capsid protein and its RGA-analogue with lipid membranes was studied by biophysical methods. Two types of model membrane were used: vesicles and monolayers spread at the air/water interface, with a composition that closely resembles the lipid moiety of hepatocyte membranes: PC/SM/PE/PC (40:33:12:15; PC: 1-palmitoyl-2-oleoylglycero-sn-3-phosphocholine; SM: sphingomyelin from chicken egg yolk; PE, 1,2-dipalmitoyl-phosphatidylethanolamine; PS: L-alpha-phosphatidyl-L-serine from bovine brain). In addition, zwitterionic PC/SM/PE (47:39:14) and cationic PC/SM/PE/DOTAP (40:33:12:15; DOTAP: 1,2-dioleoyl-3-trimethylammonium-propane) membranes were also prepared in order to dissect the electrostatic and hydrophobic components in the interaction. Changes in tryptophan fluorescence, acrylamide quenching, and resonance energy transfer experiments in the presence of vesicles, as well as the kinetics of insertion in monolayers, indicate that both peptides bind to the three types of membrane at neutral and acidic pH; however, binding is irreversible only at low pH. Membrane-destabilizing and fusogenic activities are triggered by acidification at pH 4-6, characteristic of the endosome. Fluorescence experiments show that VP3-RGD and VP3-RGA induce mixing of lipids and leakage or mixing of aqueous contents in anionic and cationic vesicles at pH 4-6, indicating leaky fusion. Interaction with zwitterionic vesicles (PC/SM/PE) results in leakage without lipid mixing, indicating pore formation. Replacement of aspartic acid in the RGD motif by alanine maintains the membrane-destabilizing properties of the peptide at low pH, but not its antigenicity. Since the RGD tripeptide is related to receptor-mediated cell adhesion and antigenicity, results suggest that receptor binding is not a molecular requirement for fusion. The possible involvement of peptide-induced membrane destabilization in the mechanism of hepatitis A virus infection of hepatocytes by the endosomal route is discussed.

Apoptosis in non-proliferating cells: implications for viral infection and tumourigenesis.

To date much attention has been focused on regulation of apoptosis in proliferating cells. However, recent evidence shows that regulation of apoptosis in quiescent tissue plays an important role in homeostasis of the organism. This review examines the implications of apoptosis of quiescent cells for both tumourigenesis and viral infection such as HIV. In this article we propose a dual role for cellular activation in the homeostasis regulation. In this model cellular mitogens not only activate quiescent cells into the active cell cycle, but under certain conditions, loss of quiescence may result in apoptosis. The loss of quiescence-associated apoptosis may play a significant role in tumourigenesis and viral infections.