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1.
Nat Commun ; 13(1): 4054, 2022 Jul 13.
Article in English | MEDLINE | ID: covidwho-1931408

ABSTRACT

Establishment of zoonotic viruses, causing pandemics like the Spanish flu and Covid-19, requires adaptation to human receptors. Pandemic influenza A viruses (IAV) that crossed the avian-human species barrier switched from binding avian-type α2-3-linked sialic acid (2-3Sia) to human-type 2-6Sia receptors. Here, we show that this specificity switch is however less dichotomous as generally assumed. Binding and entry specificity were compared using mixed synthetic glycan gradients of 2-3Sia and 2-6Sia and by employing a genetically remodeled Sia repertoire on the surface of a Sia-free cell line and on a sialoglycoprotein secreted from these cells. Expression of a range of (mixed) 2-3Sia and 2-6Sia densities shows that non-binding human-type receptors efficiently enhanced avian IAV binding and entry provided the presence of a low density of high affinity avian-type receptors, and vice versa. Considering the heterogeneity of sialoglycan receptors encountered in vivo, hetero-multivalent binding is physiologically relevant and will impact evolutionary pathways leading to host adaptation.


Subject(s)
COVID-19 , Influenza A virus , Influenza Pandemic, 1918-1919 , Influenza, Human , Animals , Hemagglutinin Glycoproteins, Influenza Virus/metabolism , Humans , Influenza A virus/metabolism , N-Acetylneuraminic Acid/metabolism , Receptors, Cell Surface/genetics , Receptors, Cell Surface/metabolism , Receptors, Virus/metabolism
2.
Commun Biol ; 4(1): 631, 2021 05 27.
Article in English | MEDLINE | ID: covidwho-1283664

ABSTRACT

IL22 is an important cytokine involved in the intestinal defense mechanisms against microbiome. By using ileum-derived organoids, we show that the expression of anti-microbial peptides (AMPs) and anti-viral peptides (AVPs) can be induced by IL22. In addition, we identified a bacterial and a viral route, both leading to IL22 production by T cells, but via different pathways. Bacterial products, such as LPS, induce enterocyte-secreted SAA1, which triggers the secretion of IL6 in fibroblasts, and subsequently IL22 in T cells. This IL22 induction can then be enhanced by macrophage-derived TNFα in two ways: by enhancing the responsiveness of T cells to IL6 and by increasing the expression of IL6 by fibroblasts. Viral infections of intestinal cells induce IFNß1 and subsequently IL7. IFNß1 can induce the expression of IL6 in fibroblasts and the combined activity of IL6 and IL7 can then induce IL22 expression in T cells. We also show that IL22 reduces the expression of viral entry receptors (e.g. ACE2, TMPRSS2, DPP4, CD46 and TNFRSF14), increases the expression of anti-viral proteins (e.g. RSAD2, AOS, ISG20 and Mx1) and, consequently, reduces the viral infection of neighboring cells. Overall, our data indicates that IL22 contributes to the innate responses against both bacteria and viruses.


Subject(s)
Interleukins/biosynthesis , Interleukins/metabolism , Animals , Anti-Bacterial Agents/metabolism , Antiviral Agents/metabolism , Cell Culture Techniques , Cytokines/immunology , Cytokines/metabolism , Disease Models, Animal , Enterocytes/immunology , Enterocytes/metabolism , Female , Fibroblasts/immunology , Fibroblasts/metabolism , Interleukins/immunology , Intestinal Mucosa/metabolism , Intestines/physiology , Mice , Mice, Inbred C57BL , Myeloid Cells/immunology , Myeloid Cells/metabolism , Organoids/metabolism , Pore Forming Cytotoxic Proteins/genetics , Pore Forming Cytotoxic Proteins/metabolism
3.
Trends Microbiol ; 29(11): 983-992, 2021 11.
Article in English | MEDLINE | ID: covidwho-1187873

ABSTRACT

Efficient penetration of the mucus layer is needed for respiratory viruses to avoid mucociliary clearance prior to infection. Many respiratory viruses bind to glycans on the heavily glycosylated mucins that give mucus its gel-like characteristics. Influenza viruses, some paramyxoviruses, and coronaviruses avoid becoming trapped in the mucus by releasing themselves by means of their envelope-embedded enzymes that destroy glycan receptors. For efficient infection, receptor binding and destruction need to be in balance with the host receptor repertoire. Establishment in a novel host species requires resetting of the balance to adapt to the different glycan repertoire encountered. Growing understanding of species-specific mucosal glycosylation patterns and the dynamic interaction with respiratory viruses identifies the mucus layer as a major host-range determinant and barrier for zoonotic transfer.


Subject(s)
Host Specificity , Viruses , Glycosylation , Mucins/metabolism , Mucus/metabolism , Polysaccharides/metabolism , Viruses/metabolism
4.
Cell ; 183(6): 1520-1535.e14, 2020 12 10.
Article in English | MEDLINE | ID: covidwho-915356

ABSTRACT

ß-Coronaviruses are a family of positive-strand enveloped RNA viruses that includes the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Much is known regarding their cellular entry and replication pathways, but their mode of egress remains uncertain. Using imaging methodologies and virus-specific reporters, we demonstrate that ß-coronaviruses utilize lysosomal trafficking for egress rather than the biosynthetic secretory pathway more commonly used by other enveloped viruses. This unconventional egress is regulated by the Arf-like small GTPase Arl8b and can be blocked by the Rab7 GTPase competitive inhibitor CID1067700. Such non-lytic release of ß-coronaviruses results in lysosome deacidification, inactivation of lysosomal degradation enzymes, and disruption of antigen presentation pathways. ß-Coronavirus-induced exploitation of lysosomal organelles for egress provides insights into the cellular and immunological abnormalities observed in patients and suggests new therapeutic modalities.


Subject(s)
COVID-19/metabolism , SARS-CoV-2/metabolism , Secretory Pathway , Virus Release , ADP-Ribosylation Factors/metabolism , Animals , COVID-19/drug therapy , COVID-19/pathology , Female , HeLa Cells , Heterocyclic Compounds, 2-Ring/pharmacology , Humans , Lysosomes , Mice , Thiourea/analogs & derivatives , Thiourea/pharmacology , rab GTP-Binding Proteins/antagonists & inhibitors , rab GTP-Binding Proteins/metabolism
5.
J Virol ; 94(4)2020 01 31.
Article in English | MEDLINE | ID: covidwho-2317

ABSTRACT

Coronavirus (CoV) nucleocapsid (N) proteins are key for incorporating genomic RNA into progeny viral particles. In infected cells, N proteins are present at the replication-transcription complexes (RTCs), the sites of CoV RNA synthesis. It has been shown that N proteins are important for viral replication and that the one of mouse hepatitis virus (MHV), a commonly used model CoV, interacts with nonstructural protein 3 (nsp3), a component of the RTCs. These two aspects of the CoV life cycle, however, have not been linked. We found that the MHV N protein binds exclusively to nsp3 and not other RTC components by using a systematic yeast two-hybrid approach, and we identified two distinct regions in the N protein that redundantly mediate this interaction. A selective N protein variant carrying point mutations in these two regions fails to bind nsp3 in vitro, resulting in inhibition of its recruitment to RTCs in vivo Furthermore, in contrast to the wild-type N protein, this N protein variant impairs the stimulation of genomic RNA and viral mRNA transcription in vivo and in vitro, which in turn leads to impairment of MHV replication and progeny production. Altogether, our results show that N protein recruitment to RTCs, via binding to nsp3, is an essential step in the CoV life cycle because it is critical for optimal viral RNA synthesis.IMPORTANCE CoVs have long been regarded as relatively harmless pathogens for humans. Severe respiratory tract infection outbreaks caused by severe acute respiratory syndrome CoV and Middle East respiratory syndrome CoV, however, have caused high pathogenicity and mortality rates in humans. These outbreaks highlighted the relevance of being able to control CoV infections. We used a model CoV, MHV, to investigate the importance of the recruitment of N protein, a central component of CoV virions, to intracellular platforms where CoVs replicate, transcribe, and translate their genomes. By identifying the principal binding partner at these intracellular platforms and generating a specific mutant, we found that N protein recruitment to these locations is crucial for promoting viral RNA synthesis. Moreover, blocking this recruitment strongly inhibits viral infection. Thus, our results explain an important aspect of the CoV life cycle and reveal an interaction of viral proteins that could be targeted in antiviral therapies.


Subject(s)
Murine hepatitis virus/physiology , Nucleocapsid Proteins/metabolism , RNA, Viral/biosynthesis , Transcription, Genetic/physiology , Viral Nonstructural Proteins/metabolism , Virus Replication/physiology , Animals , Cell Line , Humans , Mice , Nucleocapsid Proteins/genetics , RNA, Viral/genetics , Viral Nonstructural Proteins/genetics
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