Receptor-mediated Virus Research Articles

Host Sex Steroids Interact With Virus Infection: New Insights Into Sex Disparity in Infectious Diseases.

Sex hormones are steroid hormones synthesized from the gonads of animals and tissues such as the placenta and adrenocortical reticular zone. The physiological functions of sex hormones are complex. Sex hormones are not only pathologically correlated with many diseases of the reproductive system, but are etiological factors in some viral infectious diseases, including disease caused by infections of coronaviruses, herpesviruses, hepatitis viruses, and other kinds of human viruses, which either exhibit a male propensity in clinical practice, or crosstalk with androgen receptor (AR)-related pathways in viral pathogenesis. Due to the global pandemic of coronavirus disease 2019 (COVID-19), the role of androgen/AR in viral infectious disease is highlighted again, majorly representing by the recent advances of AR-responsive gene of transmembrane protease/serine subfamily member 2 (TMPRSS2), which proteolytically activates the receptor-mediated virus entry by many coronaviruses and influenza virus, along with the role of androgen-mediated signaling for the transcription of hepatitis B virus (HBV), and the role of sex hormone responsive genes during Zika virus (ZIKV) pathogenesis, et al. Collectively, we propose to provide a comprehensive overview of the role of male sex hormones during multiple phases in the life cycle of different human viruses, which may be partly responsible for the sex-specific prevalence, severity and mortality of some diseases, therefore, may provide clues to develop more efficient prevention and treatment strategies for high-risk populations.

Dysregulation of lipid metabolism and pathological inflammation in patients with COVID-19

In recent months, Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread throughout the world. COVID-19 patients show mild, moderate or severe symptoms with the latter ones requiring access to specialized intensive care. SARS-CoV-2 infections, pathogenesis and progression have not been clearly elucidated yet, thus forcing the development of many complementary approaches to identify candidate cellular pathways involved in disease progression. Host lipids play a critical role in the virus life, being the double-membrane vesicles a key factor in coronavirus replication. Moreover, lipid biogenesis pathways affect receptor-mediated virus entry at the endosomal cell surface and modulate virus propagation. In this study, targeted lipidomic analysis coupled with proinflammatory cytokines and alarmins measurement were carried out in serum of COVID-19 patients characterized by different severity degree. Serum IL-26, a cytokine involved in IL-17 pathway, TSLP and adiponectin were measured and correlated to lipid COVID-19 patient profiles. These results could be important for the classification of the COVID-19 disease and the identification of therapeutic targets.

Phosphatidylethanolamine and Phosphatidylserine Synergize To Enhance GAS6/AXL-Mediated Virus Infection and Efferocytosis.

Phosphatidylserine (PS) receptors mediate clearance of apoptotic cells-efferocytosis-by recognizing the PS exposed on those cells. They also mediate the entry of enveloped viruses by binding PS in the virion membrane. Here, we show that phosphatidylethanolamine (PE) synergizes with PS to enhance PS receptor-mediated efferocytosis and virus entry. The presence of PE on the same surface as PS dramatically enhances recognition of PS by PS-binding proteins such as GAS6, PROS, and TIM1. Liposomes containing both PE and PS bound to GAS6 and were engulfed by AXL-expressing cells much more efficiently than those containing PS alone. Further, infection of AXL-expressing cells by infectious Zika virus or Ebola, Chikungunya, or eastern equine encephalitis pseudoviruses was inhibited with greater efficiency by the liposomes containing both PS and PE compared to a mixture of liposomes separately composed of PS and PE. These data demonstrate that simultaneous recognition of PE and PS maximizes PS receptor-mediated virus entry and efferocytosis and underscore the important contribution of PE in these major biological processes.IMPORTANCE Phosphatidylserine (PS) and phosphatidylethanolamine (PE) are usually sequestered to the inner leaflet of the plasma membrane of the healthy eukaryotic cells. During apoptosis, these phospholipids move to the cell's outer leaflet where they are recognized by so-called PS receptors on surveilling phagocytes. Several pathogenic families of enveloped viruses hijack these PS receptors to gain entry into their target cells. Here, we show that efficiency of these processes is enhanced, namely, PE synergizes with PS to promote PS receptor-mediated virus infection and clearance of apoptotic cells. These findings deepen our understanding of how these fundamental biological processes are executed.

Unified feature association networks through integration of transcriptomic and proteomic data.

High-throughput multi-omics studies and corresponding network analyses of multi-omic data have rapidly expanded their impact over the last 10 years. As biological features of different types (e.g. transcripts, proteins, metabolites) interact within cellular systems, the greatest amount of knowledge can be gained from networks that incorporate multiple types of -omic data. However, biological and technical sources of variation diminish the ability to detect cross-type associations, yielding networks dominated by communities comprised of nodes of the same type. We describe here network building methods that can maximize edges between nodes of different data types leading to integrated networks, networks that have a large number of edges that link nodes of different–omic types (transcripts, proteins, lipids etc). We systematically rank several network inference methods and demonstrate that, in many cases, using a random forest method, GENIE3, produces the most integrated networks. This increase in integration does not come at the cost of accuracy as GENIE3 produces networks of approximately the same quality as the other network inference methods tested here. Using GENIE3, we also infer networks representing antibody-mediated Dengue virus cell invasion and receptor-mediated Dengue virus invasion. A number of functional pathways showed centrality differences between the two networks including genes responding to both GM-CSF and IL-4, which had a higher centrality value in an antibody-mediated vs. receptor-mediated Dengue network. Because a biological system involves the interplay of many different types of molecules, incorporating multiple data types into networks will improve their use as models of biological systems. The methods explored here are some of the first to specifically highlight and address the challenges associated with how such multi-omic networks can be assembled and how the greatest number of interactions can be inferred from different data types. The resulting networks can lead to the discovery of new host response patterns and interactions during viral infection, generate new hypotheses of pathogenic mechanisms and confirm mechanisms of disease.

Host-Virus Interaction of ZIKA Virus in Modulating Disease Pathogenesis

The Zika virus (ZIKV) is a newly emerging pathogen that has resulted in a worldwide epidemic. It primarily spreads either through infected Aedes aegypti or Aedes albopictus mosquitos leading to severe neurological disorders such as microcephaly and Guillain-Barré syndrome in susceptible individuals. The mode of ZIKV entry into specific cell types such as: epidermal keratinocytes, fibroblasts, immature dendritic cells (iDCs), and stem-cell-derived human neural progenitors has been determined through its major surface envelope glycoprotein. It has been known that oligosaccharides that are covalently linked to viral envelope proteins are crucial in defining host-virus interactions. However, the role of sugars/glycans in exploiting host-immune mechanisms and aiding receptor-mediated virus entry is not well defined. Therefore, this review focuses on host-pathogen interactions to better understand ZIKV pathogenesis.

The V domain of dog PVRL4 (nectin-4) mediates canine distemper virus entry and virus cell-to-cell spread

The entry of canine distemper virus (CDV) is a multistep process that involves the attachment of CDV hemagglutinin (H) to its cellular receptor, followed by fusion between virus and cell membranes. Our laboratory recently identified PVRL4 (nectin-4) to be the epithelial receptor for measles and canine distemper viruses. In this study, we demonstrate that the V domain of PVRL4 is critical for CDV entry and virus cell-to-cell spread. Furthermore, four key amino acid residues within the V domain of dog PVRL4 and two within the CDV hemagglutinin were shown to be essential for receptor-mediated virus entry.

The cell biology of receptor-mediated virus entry

The cell imposes multiple barriers to virus entry. However, viruses exploit fundamental cellular processes to gain entry to cells and deliver their genetic cargo. Virus entry pathways are largely defined by the interactions between virus particles and their receptors at the cell surface. These interactions determine the mechanisms of virus attachment, uptake, intracellular trafficking, and, ultimately, penetration to the cytosol. Elucidating the complex interplay between viruses and their receptors is necessary for a full understanding of how these remarkable agents invade their cellular hosts.

The Oligomeric State of the Active BM2 Ion Channel Protein of Influenza B Virus

Influenza A virus and influenza B virus particles both contain small integral membrane proteins (A/M2 and BM2, respectively) that function as a pH-sensitive proton channel and are essential for virus replication. The mechanism of action of the M2 channels is a subject of scientific interest particularly as A/M2 channel was shown to be a target for the action of the antiviral drug amantadine. Unfortunately, an inhibitor of the BM2 channel activity is not known. Thus, knowledge of the structural and functional properties of the BM2 channel is essential for the development of potent antiviral drugs. The characterization of the oligomeric state of the BM2 channel is an essential first step in the understanding of channel function. Here we describe determination of the stoichiometry of the BM2 proton channel by utilizing three different approaches. 1) We demonstrated that BM2 monomers can be chemically cross-linked to yield species consistent with dimers, trimers, and tetramers. 2) We studied electrophysiological and biochemical properties of mixed oligomers consisting of wild-type and mutated BM2 subunits and related these data to predicted binomial distribution models. 3) We used fluorescence resonance energy transfer (FRET) in combination with biochemical measurements to estimate the relationships between BM2 channel subunits expressed in the plasma membrane. Our experimental data are consistent with a tetrameric structure of the BM2 channel. Finally, we demonstrated that BM2 transmembrane domain is responsible for the channel oligomerization.

Structural analysis of human rhinovirus complexed with ICAM-1 reveals the dynamics of receptor-mediated virus uncoating.

Intercellular adhesion molecule 1 (ICAM-1) functions as the cellular receptor for the major group of human rhinoviruses, being not only the target of viral attachment but also the mediator of viral uncoating. The configurations of HRV3-ICAM-1 complexes prepared both at 4 degrees C and physiological temperature (37 degrees C) were analyzed by cryoelectron microscopy and image reconstruction. The particle diameters of two complexes (with and without RNA) representing uncoating intermediates generated at 37 degrees C were each 4% larger than that of those prepared at 4 degrees C. The larger virus particle arose by an expansive movement of the capsid pentamers along the fivefold axis, which loosens interprotomer contacts, particularly at the canyon region where the ICAM-1 receptor bound. Particle expansion required receptor binding and preceded the egress of the viral RNA. These observations suggest that receptor-mediated uncoating could be a consequence of restrained capsid motion, where the bound receptors maintain the viral capsid in an expanded open state for subsequent genome release.

The African Swine Fever Virus Proteins p54 and p30 Are Involved in Two Distinct Steps of Virus Attachment and Both Contribute to the Antibody-Mediated Protective Immune Response

The nature of the initial interactions of African swine fever (ASF) virus with target cells is only partially known, and to date only the ASF virus protein p12 has been identified as a viral attachment protein. More recently, antibodies to viral proteins p54 and p30 have been shown to neutralize the virus, inhibiting virus binding and internalization, respectively. Therefore, we investigated the role of these proteins in the receptor-mediated ASF virus endocytosis in swine macrophages, the natural host cells. Proteins p54 and p30, released from ASF virus particles after treatment of virions with a nonionic detergent, bound to virus-sensitive alveolar pig macrophages. Binding of these proteins was found to be specifically inhibited by neutralizing antibodies obtained from a convalescent pig or from pigs immunized with recombinant p54 or p30 proteins. The baculovirus-expressed proteins p54 and p30 retained the same biological properties as the viral proteins, since they also bound specifically to these cells, and their binding was equally inhibited by neutralizing antibodies. Binding of35S-labeled recombinant p54 and p30 proteins to macrophages was specifically competed by an excess of unlabeled p54 and p30, respectively. However, cross-binding inhibition was not observed, suggesting the existence of two different saturable binding sites for these proteins in the susceptible cells. In addition, protein p54 blocked the specific binding of virus particles to the macrophage, while protein p30 blocked virus internalization. Both proteins independently prevented virus infection and in a dose-dependent manner, suggesting that binding interactions mediated by both proteins are necessary to give rise to a productive infection. The relevance of blockade of virus–cell interactions mediated by p54 and p30 in the protective immune response against ASF virus was then investigated. Immunization of pigs with either recombinant p54 or p30 proteins induced neutralizing antibodies which, as expected, inhibited virus attachment or internalization, respectively. However, immunized pigs were not protected against lethal infection and the disease course was not modified in these animals. In contrast, immunization with a combination of p54 and p30 proteins simultaneously stimulated both virus neutralizing mechanisms and modified drastically the disease course, rendering a variable degree of protection ranging from a delay in the onset of the disease to complete protection against virus infection. In conclusion, the above results strongly suggest that proteins p54 and p30 mediate specific interactions between ASF virus and cellular receptors and that simultaneous interference with these two interactions has a complementary effect in antibody-mediated protection.

Murine retroviruses use at least six different receptors for entry into Mus dunni cells.

Murine retroviruses have been divided into six interference groups that use different receptors for cell entry: the ecotropic, xenotropic, polytropic, amphotropic, 10A1, and Mus dunni endogenous virus groups. Some interference is observed between xenotropic and polytropic viruses and between amphotropic and 10A1 viruses, indicating some overlap in receptor specificity between these groups, but otherwise these interference groups appear completely independent. In contrast, one study found interference among many of these groups when Mus dunni wild mouse cells were examined with an immunofluorescence assay to detect infection by the challenge virus. Here we have used a more direct assay for cell entry by using pseudotyped retroviral vectors to measure interference in M. dunni cells, and we find no evidence for extensive interference between members of different murine retrovirus groups. Indeed, our results in M. dunni cells are consistent with interference results observed in other cell types and indicate that the anomalous interference results previously observed in M. dunni cells with the immunofluorescence assay were most likely due to factors other than those that affect receptor-mediated virus entry. In summary, our results show that murine retroviruses use at least six different receptors for entry into M. dunni cells.

Analysis of the murine ecotropic leukemia virus receptor reveals a common biochemical determinant on diverse cell surface receptors that is essential to retrovirus entry.

Two residues, tyrosine 235 and glutamic acid 237, of the ecotropic murine leukemia virus receptor (ATRC1) have been shown to be essential for receptor-mediated virus envelope binding and entry. We performed genetic analyses to examine the biochemical contribution of these residues in a productive virus-receptor interaction. Altered ATRC1 receptors bearing either a phenylalanine, a tryptophan, a histidine, or a methionine at position 235 mediated ecotropic virus entry comparable to that mediated by ATRC1. In contrast, altered ATRC1 receptors bearing alanine, threonine, serine, or proline at position 235 exhibited a 300- to 10,000-fold decrease in receptor capability. Furthermore, substitution of tyrosine or phenylalanine into the corresponding position (242) of the homologous human protein that lacks ecotropic virus receptor capability resulted in acquisition of ecotropic virus receptor function comparable to that of ATRC1. Substitution of a tryptophan or a histidine at that position of the human protein, however, resulted in a much-reduced receptor capability, suggesting a preference for a benzene ring in the hydrophobic side chain. A similar analysis of proteins substituted at position 237 revealed that aspartic acid, but not arginine or lysine, can functionally substitute for glutamic acid 237 in ATRC1 or at the corresponding position in the human protein. These results suggest a requirement for an acidic and a nearby hydrophobic amino acid for efficient ecotropic virus entry. Similar motifs have been identified in the virus binding sites of other retrovirus receptors, suggesting that the initial step of retrovirus entry may be governed by a common mechanism.

Stabilization of "A" particles of coxsackievirus B3 by a HeLa cell plasma membrane extract.

Previous studies in our laboratory showed that HeLa cell plasma membranes were recovered from sucrose gradients in two major bands and that the heavier band possessed a putative inhibitor of uncoating of coxsackievirus B3. It has now been found that the mechanism of inhibition is the stabilization of "A" particles against inactivation at 37 degrees C. [3H]uridine-labeled virions converted to A particles by band 4, the heavier band, were four times more stable at 37 degrees C than those produced by band 3. Partially purified A particles from both bands were equally unstable. It was found that the stabilizing factor was extractable by saline from band 4 and remained soluble after centrifugation (109,000 X g for 2 h). Addition to A particles of this soluble factor isolated from either band 4 or band 3 stabilized the A particles. The stabilizing factor could not be replaced by an extract from band 3 or by bovine serum albumin. Thus, the finding that the membrane factor inhibits virus uncoating by stabilizing A particles against spontaneous disruption at 37 degrees C focuses attention on an inherent problem associated with defining receptor-mediated virus uncoating.