RESUMO
Poxviruses have evolved a wide array of mechanisms to evade the immune response, and we provide an overview of the different immunomodulatory strategies. Poxviruses prevent the recognition of viral DNA that triggers the immune responses and inhibit signaling pathways within the infected cell. A unique feature of poxviruses is the production of secreted proteins that mimic cytokines and cytokine receptors, acting as decoy receptors to neutralize the activity of cytokines and chemokines. The capacity of these proteins to evade cellular immune responses by inhibiting cytokine activation is complemented by poxviruses' strategies to block natural killer cells and cytotoxic T cells, often through interfering with antigen presentation pathways. Mechanisms that target complement activation are also encoded by poxviruses. Virus-encoded proteins that target immune molecules and pathways play a major role in immune modulation, and their contribution to viral pathogenesis, facilitating virus replication or preventing immunopathology, is discussed.
Assuntos
Evasão da Resposta Imune , Infecções por Poxviridae , Poxviridae , Humanos , Poxviridae/imunologia , Poxviridae/fisiologia , Animais , Infecções por Poxviridae/imunologia , Citocinas/metabolismo , Transdução de Sinais , Proteínas Virais/metabolismo , Proteínas Virais/imunologia , Apresentação de Antígeno/imunologia , Interações Hospedeiro-Patógeno/imunologiaRESUMO
Vertebrate immune systems suppress viral infection using both innate restriction factors and adaptive immunity. Viruses mutate to escape these defenses, driving hosts to counterevolve to regain fitness. This cycle recurs repeatedly, resulting in an evolutionary arms race whose outcome depends on the pace and likelihood of adaptation by host and viral genes. Although viruses evolve faster than their vertebrate hosts, their proteins are subject to numerous functional constraints that impact the probability of adaptation. These constraints are globally defined by evolutionary landscapes, which describe the fitness and adaptive potential of all possible mutations. We review deep mutational scanning experiments mapping the evolutionary landscapes of both host and viral proteins engaged in arms races. For restriction factors and some broadly neutralizing antibodies, landscapes favor the host, which may help to level the evolutionary playing field against rapidly evolving viruses. We discuss the biophysical underpinnings of these landscapes and their therapeutic implications.
Assuntos
Viroses , Vírus , Animais , Evolução Biológica , Humanos , Mutação , Proteínas Virais , Viroses/genética , Vírus/genéticaRESUMO
Development of improved approaches for HIV-1 prevention will likely be required for a durable end to the global AIDS pandemic. Recent advances in preclinical studies and early phase clinical trials offer renewed promise for immunologic strategies for blocking acquisition of HIV-1 infection. Clinical trials are currently underway to evaluate the efficacy of two vaccine candidates and a broadly neutralizing antibody (bNAb) to prevent HIV-1 infection in humans. However, the vast diversity of HIV-1 is a major challenge for both active and passive immunization. Here we review current immunologic strategies for HIV-1 prevention, with a focus on current and next-generation vaccines and bNAbs.
Assuntos
Vacinas contra a AIDS/imunologia , Anticorpos Neutralizantes/imunologia , Anticorpos Anti-HIV/imunologia , Infecções por HIV/imunologia , Infecções por HIV/prevenção & controle , HIV-1/imunologia , Interações Hospedeiro-Patógeno/imunologia , Vacinas contra a AIDS/administração & dosagem , Animais , Ensaios Clínicos como Assunto , Gerenciamento Clínico , Variação Genética , Infecções por HIV/virologia , HIV-1/genética , Humanos , Imunização Passiva , RNA Viral , Relação Estrutura-Atividade , Linfócitos T/imunologia , Linfócitos T/metabolismo , Proteínas Virais/química , Proteínas Virais/genéticaRESUMO
Positive-strand RNA viruses encompass a variety of established and emerging eukaryotic pathogens. Their genome replication is confined to specialized cytoplasmic membrane compartments known as replication organelles (ROs). These ROs derive from host membranes, transformed into distinct structures such as invaginated spherules or intricate membrane networks including single- and/or double-membrane vesicles. ROs play a vital role in orchestrating viral RNA synthesis and evading detection by innate immune sensors of the host. In recent years, groundbreaking cryo-electron microscopy studies conducted with several prototypic viruses have significantly advanced our understanding of RO structure and function. Notably, these studies unveiled the presence of crown-shaped multimeric viral protein complexes that seem to actively participate in viral RNA synthesis and regulate the release of newly synthesized RNA into the cytosol for translation and packaging. These findings have shed light on novel viral functions and fascinating macromolecular complexes that delineate promising new avenues for future research.
Assuntos
Microscopia Crioeletrônica , RNA Viral , Replicação Viral , Microscopia Crioeletrônica/métodos , RNA Viral/metabolismo , RNA Viral/genética , RNA Viral/química , Humanos , Vírus de RNA de Cadeia Positiva/metabolismo , Vírus de RNA de Cadeia Positiva/genética , Vírus de RNA de Cadeia Positiva/química , Vírus de RNA de Cadeia Positiva/ultraestrutura , Organelas/ultraestrutura , Organelas/virologia , Organelas/metabolismo , Proteínas Virais/metabolismo , Proteínas Virais/química , Proteínas Virais/genética , Proteínas Virais/ultraestrutura , Animais , Compartimentos de Replicação Viral/metabolismo , Compartimentos de Replicação Viral/ultraestruturaRESUMO
Over the past few years, numerous anti-phage defense systems have been discovered in bacteria. Although the mechanism of defense for some of these systems is understood, a major unanswered question is how these systems sense phage infection. To systematically address this question, we isolated 177 phage mutants that escape 15 different defense systems. In many cases, these escaper phages were mutated in the gene sensed by the defense system, enabling us to map the phage determinants that confer sensitivity to bacterial immunity. Our data identify specificity determinants of diverse retron systems and reveal phage-encoded triggers for multiple abortive infection systems. We find general themes in phage sensing and demonstrate that mechanistically diverse systems have converged to sense either the core replication machinery of the phage, phage structural components, or host takeover mechanisms. Combining our data with previous findings, we formulate key principles on how bacterial immune systems sense phage invaders.
Assuntos
Bactérias , Bacteriófagos , Bactérias/genética , Bactérias/virologia , Bacteriófagos/genética , Sistemas CRISPR-Cas , Proteínas Virais/metabolismo , Mutação , Fenômenos Fisiológicos BacterianosRESUMO
Epstein-Barr virus (EBV) is a ubiquitous, oncogenic virus that is associated with a number of different human malignancies as well as autoimmune disorders. The expression of EBV viral proteins and non-coding RNAs contribute to EBV-mediated disease pathologies. The virus establishes life-long latency in the human host and is adept at evading host innate and adaptive immune responses. In this review, we discuss the life cycle of EBV, the various functions of EBV-encoded proteins and RNAs, the ability of the virus to activate and evade immune responses, as well as the neoplastic and autoimmune diseases that are associated with EBV infection in the human population.
Assuntos
Infecções por Vírus Epstein-Barr , Herpesvirus Humano 4 , Biologia , Herpesvirus Humano 4/genética , Herpesvirus Humano 4/metabolismo , Humanos , RNA/metabolismo , Proteínas Virais/metabolismo , Latência ViralRESUMO
Influenza virus RNA-dependent RNA polymerase (FluPol) transcribes the viral RNA genome in the infected cell nucleus. In the 1970s, researchers showed that viral transcription depends on host RNA polymerase II (RNAP II) activity and subsequently that FluPol snatches capped oligomers from nascent RNAP II transcripts to prime its own transcription. Exactly how this occurs remains elusive. Here, we review recent advances in the mechanistic understanding of FluPol transcription and early events in RNAP II transcription that are relevant to cap-snatching. We describe the known direct interactions between FluPol and the RNAP II C-terminal domain and summarize the transcription-related host factors that have been found to interact with FluPol. We also discuss open questions regarding how FluPol may be targeted to actively transcribing RNAP II and the exact context and timing of cap-snatching, which is presumed to occur after cap completion but before the cap is sequestered by the nuclear cap-binding complex.
Assuntos
Interações Hospedeiro-Patógeno/fisiologia , Orthomyxoviridae/enzimologia , RNA Polimerase Dependente de RNA/metabolismo , Transcrição Gênica , Proteínas Virais/metabolismo , Humanos , Orthomyxoviridae/patogenicidade , Proteínas de Ligação ao Cap de RNA/genética , Proteínas de Ligação ao Cap de RNA/metabolismo , RNA Polimerase II/química , RNA Polimerase II/metabolismo , RNA Polimerase Dependente de RNA/genética , Proteínas Virais/genéticaRESUMO
Located at the inner leaflet of the plasma membrane (PM), phosphatidyl-inositol 4,5-bisphosphate [PI(4,5)P2] composes only 1-2 mol% of total PM lipids. With its synthesis and turnover both spatially and temporally regulated, PI(4,5)P2 recruits and interacts with hundreds of cellular proteins to support a broad spectrum of cellular functions. Several factors contribute to the versatile and dynamic distribution of PI(4,5)P2 in membranes. Physiological multivalent cations such as Ca2+ and Mg2+ can bridge between PI(4,5)P2 headgroups, forming nanoscopic PI(4,5)P2-cation clusters. The distinct lipid environment surrounding PI(4,5)P2 affects the degree of PI(4,5)P2 clustering. In addition, diverse cellular proteins interacting with PI(4,5)P2 can further regulate PI(4,5)P2 lateral distribution and accessibility. This review summarizes the current understanding of PI(4,5)P2 behavior in both cells and model membranes, with emphasis on both multivalent cation- and protein-induced PI(4,5)P2 clustering. Understanding the nature of spatially separated pools of PI(4,5)P2 is fundamental to cell biology.
Assuntos
Interações Hospedeiro-Patógeno/fisiologia , Fosfatidilinositol 4,5-Difosfato/metabolismo , Replicação Viral/fisiologia , Animais , Membrana Celular/metabolismo , Humanos , Micelas , Fosfatidilinositol 4,5-Difosfato/química , Proteínas Virais/metabolismoRESUMO
Alphaviruses are emerging, mosquito-transmitted pathogens that cause musculoskeletal and neurological disease in humans. Although neutralizing antibodies that inhibit individual alphaviruses have been described, broadly reactive antibodies that protect against both arthritogenic and encephalitic alphaviruses have not been reported. Here, we identify DC2.112 and DC2.315, two pan-protective yet poorly neutralizing human monoclonal antibodies (mAbs) that avidly bind to viral antigen on the surface of cells infected with arthritogenic and encephalitic alphaviruses. These mAbs engage a conserved epitope in domain II of the E1 protein proximal to and within the fusion peptide. Treatment with DC2.112 or DC2.315 protects mice against infection by both arthritogenic (chikungunya and Mayaro) and encephalitic (Venezuelan, Eastern, and Western equine encephalitis) alphaviruses through multiple mechanisms, including inhibition of viral egress and monocyte-dependent Fc effector functions. These findings define a conserved epitope recognized by weakly neutralizing yet protective antibodies that could be targeted for pan-alphavirus immunotherapy and vaccine design.
Assuntos
Alphavirus/imunologia , Anticorpos Antivirais/imunologia , Sequência Conservada/imunologia , Epitopos/imunologia , Proteínas Virais/imunologia , Infecções por Alphavirus/imunologia , Infecções por Alphavirus/virologia , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/imunologia , Febre de Chikungunya/imunologia , Febre de Chikungunya/virologia , Vírus Chikungunya/imunologia , Chlorocebus aethiops , Mapeamento de Epitopos , Epitopos/química , Humanos , Masculino , Camundongos Endogâmicos C57BL , Modelos Biológicos , Monócitos/metabolismo , Células Vero , Proteínas Virais/química , Liberação de VírusRESUMO
To control viral infection, vertebrates rely on both inducible interferon responses and less well-characterized cell-intrinsic responses composed of "at the ready" antiviral effector proteins. Here, we show that E3 ubiquitin ligase TRIM7 is a cell-intrinsic antiviral effector that restricts multiple human enteroviruses by targeting viral 2BC, a membrane remodeling protein, for ubiquitination and proteasome-dependent degradation. Selective pressure exerted by TRIM7 results in emergence of a TRIM7-resistant coxsackievirus with a single point mutation in the viral 2C ATPase/helicase. In cultured cells, the mutation helps the virus evade TRIM7 but impairs optimal viral replication, and this correlates with a hyperactive and structurally plastic 2C ATPase. Unexpectedly, the TRIM7-resistant virus has a replication advantage in mice and causes lethal pancreatitis. These findings reveal a unique mechanism for targeting enterovirus replication and provide molecular insight into the benefits and trade-offs of viral evolution imposed by a host restriction factor.
Assuntos
Enterovirus/fisiologia , Enterovirus/patogenicidade , Proteínas com Motivo Tripartido/metabolismo , Ubiquitina-Proteína Ligases/metabolismo , Replicação Viral/fisiologia , Adenosina Trifosfatases/metabolismo , Animais , Linhagem Celular , Feminino , Humanos , Inflamação/patologia , Camundongos Endogâmicos C57BL , Mutação/genética , Complexo de Endopeptidases do Proteassoma/metabolismo , Ligação Proteica , Proteólise , RNA Viral/metabolismo , Ubiquitina/metabolismo , Proteínas Virais/genéticaRESUMO
Crimean-Congo hemorrhagic fever virus (CCHFV) is a World Health Organization priority pathogen. CCHFV infections cause a highly lethal hemorrhagic fever for which specific treatments and vaccines are urgently needed. Here, we characterize the human immune response to natural CCHFV infection to identify potent neutralizing monoclonal antibodies (nAbs) targeting the viral glycoprotein. Competition experiments showed that these nAbs bind six distinct antigenic sites in the Gc subunit. These sites were further delineated through mutagenesis and mapped onto a prefusion model of Gc. Pairwise screening identified combinations of non-competing nAbs that afford synergistic neutralization. Further enhancements in neutralization breadth and potency were attained by physically linking variable domains of synergistic nAb pairs through bispecific antibody (bsAb) engineering. Although multiple nAbs protected mice from lethal CCHFV challenge in pre- or post-exposure prophylactic settings, only a single bsAb, DVD-121-801, afforded therapeutic protection. DVD-121-801 is a promising candidate suitable for clinical development as a CCHFV therapeutic.
Assuntos
Anticorpos Neutralizantes/imunologia , Febre Hemorrágica da Crimeia/imunologia , Sobreviventes , Sequência de Aminoácidos , Animais , Anticorpos Monoclonais/imunologia , Antígenos Virais/metabolismo , Fenômenos Biofísicos , Chlorocebus aethiops , Mapeamento de Epitopos , Epitopos/metabolismo , Feminino , Vírus da Febre Hemorrágica da Crimeia-Congo/imunologia , Febre Hemorrágica da Crimeia/prevenção & controle , Humanos , Imunoglobulina G/metabolismo , Masculino , Camundongos , Testes de Neutralização , Ligação Proteica , Engenharia de Proteínas , Proteínas Recombinantes/imunologia , Células Vero , Proteínas Virais/químicaRESUMO
Alphaviruses cause severe arthritogenic or encephalitic disease. The E1 structural glycoprotein is highly conserved in these viruses and mediates viral fusion with host cells. However, the role of antibody responses to the E1 protein in immunity is poorly understood. We isolated E1-specific human monoclonal antibodies (mAbs) with diverse patterns of recognition for alphaviruses (ranging from Eastern equine encephalitis virus [EEEV]-specific to alphavirus cross-reactive) from survivors of natural EEEV infection. Antibody binding patterns and epitope mapping experiments identified differences in E1 reactivity based on exposure of epitopes on the glycoprotein through pH-dependent mechanisms or presentation on the cell surface prior to virus egress. Therapeutic efficacy in vivo of these mAbs corresponded with potency of virus egress inhibition in vitro and did not require Fc-mediated effector functions for treatment against subcutaneous EEEV challenge. These studies reveal the molecular basis for broad and protective antibody responses to alphavirus E1 proteins.
Assuntos
Alphavirus/imunologia , Anticorpos Antivirais/imunologia , Reações Cruzadas/imunologia , Proteínas Virais/imunologia , Liberação de Vírus/fisiologia , Animais , Anticorpos Monoclonais/imunologia , Anticorpos Monoclonais/isolamento & purificação , Anticorpos Neutralizantes/imunologia , Antígenos Virais/imunologia , Linhagem Celular , Vírus Chikungunya/imunologia , Vírus da Encefalite Equina do Leste/imunologia , Encefalomielite Equina/imunologia , Encefalomielite Equina/virologia , Mapeamento de Epitopos , Feminino , Cavalos , Humanos , Concentração de Íons de Hidrogênio , Articulações/patologia , Masculino , Camundongos Endogâmicos C57BL , Modelos Biológicos , Ligação Proteica , RNA Viral/metabolismo , Receptores Fc/metabolismo , Temperatura , Vírion/metabolismo , Internalização do VírusRESUMO
My coworkers and I have used animal viruses and their interaction with host cells to investigate cellular processes difficult to study by other means. This approach has allowed us to branch out in many directions, including membrane protein characterization, endocytosis, secretion, protein folding, quality control, and glycobiology. At the same time, our aim has been to employ cell biological approaches to expand the fundamental understanding of animal viruses and their pathogenic lifestyles. We have studied mechanisms of host cell entry and the uncoating of incoming viruses as well as the synthesis, folding, maturation, and intracellular movement of viral proteins and molecular assemblies. I have had the privilege to work in institutions in four different countries. The early years in Finland (the University of Helsinki) were followed by 6 years in Germany (European Molecular Biology Laboratory), 16 years in the United States (Yale School of Medicine), and 16 years in Switzerland (ETH Zurich).
Assuntos
Calnexina/genética , Calreticulina/genética , Interações Hospedeiro-Patógeno/genética , Vírus da Influenza A/genética , Picornaviridae/genética , Proteínas Virais/genética , Virologia/história , Animais , Calnexina/química , Calnexina/metabolismo , Calreticulina/química , Calreticulina/metabolismo , Linhagem Celular , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/virologia , Endossomos/metabolismo , Endossomos/virologia , Regulação da Expressão Gênica , História do Século XX , História do Século XXI , Humanos , Vírus da Influenza A/metabolismo , Picornaviridae/metabolismo , Dobramento de Proteína , Vírus da Floresta de Semliki/genética , Vírus da Floresta de Semliki/metabolismo , Vesiculovirus/genética , Vesiculovirus/metabolismo , Proteínas Virais/química , Proteínas Virais/metabolismo , Internalização do VírusRESUMO
Clustered regularly interspaced short palindromic repeats (CRISPR) together with their accompanying cas (CRISPR-associated) genes are found frequently in bacteria and archaea, serving to defend against invading foreign DNA, such as viral genomes. CRISPR-Cas systems provide a uniquely powerful defense because they can adapt to newly encountered genomes. The adaptive ability of these systems has been exploited, leading to their development as highly effective tools for genome editing. The widespread use of CRISPR-Cas systems has driven a need for methods to control their activity. This review focuses on anti-CRISPRs (Acrs), proteins produced by viruses and other mobile genetic elements that can potently inhibit CRISPR-Cas systems. Discovered in 2013, there are now 54 distinct families of these proteins described, and the functional mechanisms of more than a dozen have been characterized in molecular detail. The investigation of Acrs is leading to a variety of practical applications and is providing exciting new insight into the biology of CRISPR-Cas systems.
Assuntos
Sistemas CRISPR-Cas/efeitos dos fármacos , Edição de Genes/métodos , Bibliotecas de Moléculas Pequenas/farmacologia , Proteínas Virais/genética , Vírus/genética , Archaea/genética , Archaea/imunologia , Archaea/virologia , Bactérias/genética , Bactérias/imunologia , Bactérias/virologia , Proteínas de Bactérias/antagonistas & inibidores , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Coevolução Biológica , Proteínas Associadas a CRISPR/antagonistas & inibidores , Proteínas Associadas a CRISPR/genética , Proteínas Associadas a CRISPR/metabolismo , DNA/antagonistas & inibidores , DNA/química , DNA/genética , DNA/metabolismo , Clivagem do DNA/efeitos dos fármacos , Endodesoxirribonucleases/antagonistas & inibidores , Endodesoxirribonucleases/genética , Endodesoxirribonucleases/metabolismo , Humanos , Modelos Moleculares , Família Multigênica , Ligação Proteica , Multimerização Proteica/efeitos dos fármacos , RNA Guia de Cinetoplastídeos/genética , RNA Guia de Cinetoplastídeos/metabolismo , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/metabolismo , Proteínas Virais/química , Proteínas Virais/metabolismo , Proteínas Virais/farmacologia , Vírus/metabolismo , Vírus/patogenicidadeRESUMO
Viral genomes encode transcriptional regulators that alter the expression of viral and host genes. Despite an emerging role in human diseases, a thorough annotation of human viral transcriptional regulators (vTRs) is currently lacking, limiting our understanding of their molecular features and functions. Here, we provide a comprehensive catalog of 419 vTRs belonging to 20 different virus families. Using this catalog, we characterize shared and unique cellular genes, proteins, and pathways targeted by particular vTRs and discuss the role of vTRs in human disease pathogenesis. Our study provides a unique and valuable resource for the fields of virology, genomics, and human disease genetics.
Assuntos
Transcrição Gênica , Proteínas Virais/metabolismo , Epigênese Genética , Humanos , Modelos Biológicos , Mapas de Interação de Proteínas , Proteínas Virais/química , Proteínas Virais/genéticaRESUMO
Some negative-sense RNA viruses prime mRNA transcription using host 5' cap sequences, usurping host translational machinery and evading antiviral surveillance. In this issue of Cell, Ho et al. identify an additional consequence of this viral strategy: the acquisition of upstream start codons from host-derived sequences and subsequent translation of novel viral products.
Assuntos
Capuzes de RNA , Proteínas Virais , Humanos , RNA Mensageiro , RNA Viral/genética , Proteínas Recombinantes de Fusão , Proteínas Virais/genéticaRESUMO
SARS-CoV-2 is an enveloped virus responsible for the COVID-19 pandemic. Despite recent advances in the structural elucidation of SARS-CoV-2 proteins, the detailed architecture of the intact virus remains to be unveiled. Here we report the molecular assembly of the authentic SARS-CoV-2 virus using cryoelectron tomography (cryo-ET) and subtomogram averaging (STA). Native structures of the S proteins in pre- and postfusion conformations were determined to average resolutions of 8.7-11 Å. Compositions of the N-linked glycans from the native spikes were analyzed by mass spectrometry, which revealed overall processing states of the native glycans highly similar to that of the recombinant glycoprotein glycans. The native conformation of the ribonucleoproteins (RNPs) and their higher-order assemblies were revealed. Overall, these characterizations revealed the architecture of the SARS-CoV-2 virus in exceptional detail and shed light on how the virus packs its â¼30-kb-long single-segmented RNA in the â¼80-nm-diameter lumen.
Assuntos
Betacoronavirus/fisiologia , Betacoronavirus/ultraestrutura , Montagem de Vírus , Animais , Chlorocebus aethiops , Microscopia Crioeletrônica , Humanos , Espectrometria de Massas , Modelos Moleculares , Conformação Proteica , SARS-CoV-2 , Células Vero , Proteínas Virais/química , Proteínas Virais/ultraestrutura , Cultura de VírusRESUMO
Understanding adaptive immunity to SARS-CoV-2 is important for vaccine development, interpreting coronavirus disease 2019 (COVID-19) pathogenesis, and calibration of pandemic control measures. Using HLA class I and II predicted peptide "megapools," circulating SARS-CoV-2-specific CD8+ and CD4+ T cells were identified in â¼70% and 100% of COVID-19 convalescent patients, respectively. CD4+ T cell responses to spike, the main target of most vaccine efforts, were robust and correlated with the magnitude of the anti-SARS-CoV-2 IgG and IgA titers. The M, spike, and N proteins each accounted for 11%-27% of the total CD4+ response, with additional responses commonly targeting nsp3, nsp4, ORF3a, and ORF8, among others. For CD8+ T cells, spike and M were recognized, with at least eight SARS-CoV-2 ORFs targeted. Importantly, we detected SARS-CoV-2-reactive CD4+ T cells in â¼40%-60% of unexposed individuals, suggesting cross-reactive T cell recognition between circulating "common cold" coronaviruses and SARS-CoV-2.
Assuntos
Betacoronavirus/fisiologia , Infecções por Coronavirus/imunologia , Epitopos de Linfócito T , Pneumonia Viral/imunologia , Betacoronavirus/genética , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/imunologia , COVID-19 , Vacinas contra COVID-19 , Convalescença , Infecções por Coronavirus/sangue , Infecções por Coronavirus/metabolismo , Infecções por Coronavirus/prevenção & controle , Infecções por Coronavirus/virologia , Reações Cruzadas , Humanos , Leucócitos Mononucleares/imunologia , Pandemias , Pneumonia Viral/sangue , Pneumonia Viral/metabolismo , Pneumonia Viral/virologia , SARS-CoV-2 , Glicoproteína da Espícula de Coronavírus/metabolismo , Proteínas Virais/metabolismo , Vacinas Virais/imunologiaRESUMO
RNA viruses are a major human health threat. The life cycles of many highly pathogenic RNA viruses like influenza A virus (IAV) and Lassa virus depends on host mRNA, because viral polymerases cleave 5'-m7G-capped host transcripts to prime viral mRNA synthesis ("cap-snatching"). We hypothesized that start codons within cap-snatched host transcripts could generate chimeric human-viral mRNAs with coding potential. We report the existence of this mechanism of gene origination, which we named "start-snatching." Depending on the reading frame, start-snatching allows the translation of host and viral "untranslated regions" (UTRs) to create N-terminally extended viral proteins or entirely novel polypeptides by genetic overprinting. We show that both types of chimeric proteins are made in IAV-infected cells, generate T cell responses, and contribute to virulence. Our results indicate that during infection with IAV, and likely a multitude of other human, animal and plant viruses, a host-dependent mechanism allows the genesis of hybrid genes.
Assuntos
Capuzes de RNA/genética , Infecções por Vírus de RNA/genética , Proteínas Recombinantes de Fusão/genética , Regiões 5' não Traduzidas/genética , Animais , Bovinos , Linhagem Celular , Cricetinae , Cães , Humanos , Vírus da Influenza A/metabolismo , Camundongos , Proteínas Mutantes Quiméricas/genética , Proteínas Mutantes Quiméricas/metabolismo , Fases de Leitura Aberta/genética , Capuzes de RNA/metabolismo , Infecções por Vírus de RNA/metabolismo , Vírus de RNA/genética , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , RNA Viral/metabolismo , RNA Polimerase Dependente de RNA/genética , RNA Polimerase Dependente de RNA/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Transcrição Gênica/genética , Proteínas Virais/metabolismo , Replicação Viral/genéticaRESUMO
At steady state, the NOD-like receptor (NLR)-containing pyrin domain (PYD) (NLRP)1 inflammasome is maintained in an auto-inhibitory complex by dipeptidyl peptidases 8 and 9 (DPP8 and DPP9) and is activated by pathogen-encoded proteases after infection. Here, we showed that the open reading frame (ORF)45 protein of the Kaposi's sarcoma-associated herpesvirus activated the human NLRP1 (hNLRP1) inflammasome in a non-protease-dependent manner, and we additionally showed that the Linker1 region of hNLRP1, situated between the PYD and NACHT domains, was required for the auto-inhibition and non-protease-dependent activation of hNLRP1. At steady state, the interaction between Linker1 and the UPA subdomain silenced the activation of hNLRP1 in auto-inhibitory complexes either containing DPP9 or not in a manner independent of DPP9. ORF45 binding to Linker1 displaced UPA from the Linker1-UPA complex and induced the release of the C-terminal domain of hNLRP1 for inflammasome assembly. The ORF45-dependent activation of the NLRP1 inflammasome was conserved in primates but was not observed for murine NLRP1b inflammasomes.