scholarly journals N-linked glycan sites on the influenza NA head domain are required for efficient IAV incorporation and replication

2020 ◽  
Author(s):  
Henrik Östbye ◽  
Jin Gao ◽  
Mira Rakic Martinez ◽  
Hao Wang ◽  
Jan-Willem de Gier ◽  
...  
Keyword(s):  
Influenza A ◽  
Surface Antigens ◽  
Secretory Protein ◽  
Human Origin ◽  
Time Analysis ◽  
Enveloped Viruses ◽  
Virion Incorporation ◽  
Head Domain ◽  
Glycosylation Sites ◽  
Over Time

ABSTRACTN-linked glycans commonly contribute to secretory protein folding, sorting and signaling. For enveloped viruses such as the influenza A virus (IAV), the addition of large N-linked glycans can also prevent access to epitopes on the surface antigens hemagglutinin (HA or H) and neuraminidase (NA or N). Sequence analysis showed that in the NA head domain of H1N1 IAVs three N-linked glycosylation sites are conserved and that a fourth site is conserved in H3N2 IAVs. Variable sites are almost exclusive to H1N1 IAVs of human origin, where the number of head glycosylation sites first increased and then decreased over time. In contrast, variable sites exist in H3N2 IAVs of human and swine origin, where the number of head glycosylation sites has mainly increased over time. Analysis of IAVs carrying N1 and N2 mutants demonstrated that the N-linked glycosylation sites on the NA head domain are required for efficient virion incorporation and replication in cells or eggs. It also revealed that N1 stability is more affected by the head domain glycans, suggesting N2 is more amenable to glycan additions. Together, these results indicate that in addition to antigenicity, N-linked glycosylation sites can alter NA enzymatic stability and the NA amount in virions.

scholarly journals N-Linked Glycan Sites on the Influenza A Virus Neuraminidase Head Domain Are Required for Efficient Viral Incorporation and Replication

2020 ◽  
Vol 94 (19) ◽  
Author(s):  
Henrik Östbye ◽  
Jin Gao ◽  
Mira Rakic Martinez ◽  
Hao Wang ◽  
Jan-Willem de Gier ◽  
...  
Keyword(s):  
Influenza A Virus ◽  
Surface Antigen ◽  
Influenza A ◽  
Surface Antigens ◽  
Secretory Protein ◽  
Enveloped Viruses ◽  
Virion Incorporation ◽  
Head Domain ◽  
Glycosylation Sites ◽  
Over Time

ABSTRACT N-linked glycans commonly contribute to secretory protein folding, sorting, and signaling. For enveloped viruses, such as the influenza A virus (IAV), large N-linked glycans can also be added to prevent access to epitopes on the surface antigens hemagglutinin (HA or H) and neuraminidase (NA or N). Sequence analysis showed that in the NA head domain of H1N1 IAVs, three N-linked glycosylation sites are conserved and that a fourth site is conserved in H3N2 IAVs. Variable sites are almost exclusive to H1N1 IAVs of human origin, where the number of head glycosylation sites first increased over time and then decreased with and after the introduction of the 2009 pandemic H1N1 IAV of Eurasian swine origin. In contrast, variable sites exist in H3N2 IAVs of human and swine origin, where the number of head glycosylation sites has mainly increased over time. Analysis of IAVs carrying N1 and N2 mutants demonstrated that the N-linked glycosylation sites on the NA head domain are required for efficient virion incorporation and replication in cells and eggs. It also revealed that N1 stability is more affected by the head domain glycans, suggesting N2 is more amenable to glycan additions. Together, these results indicate that in addition to antigenicity, N-linked glycosylation sites can alter NA enzymatic stability and the NA amount in virions. IMPORTANCE N-linked glycans are transferred to secretory proteins upon entry into the endoplasmic reticulum lumen. In addition to promoting secretory protein maturation, enveloped viruses also utilize these large oligosaccharide structures to prevent access to surface antigen epitopes. Sequence analyses of the influenza A virus (IAV) surface antigen neuraminidase (NA or N) showed that the conservation of N-linked glycosylation sites on the NA enzymatic head domain differs by IAV subtype (H1N1 versus H3N2) and species of origin, with human-derived IAVs possessing the most variability. Experimental analyses verified that the N-linked glycosylation sites on the NA head domain contribute to virion incorporation and replication. It also revealed that the head domain glycans affect N1 stability more than N2, suggesting N2 is more accommodating to glycan additions. These results demonstrate that in addition to antigenicity, changes in N-linked glycosylation sites can alter other properties of viral surface antigens and virions.

scholarly journals Evolutionary Dynamics of Indels in SARS-CoV-2 Spike Glycoprotein

2021 ◽  
Vol 17 ◽  
pp. 117693432110646
Author(s):  
R Shyama Prasad Rao ◽  
Nagib Ahsan ◽  
Chunhui Xu ◽  
Lingtao Su ◽  
Jacob Verburgt ◽  
...  
Keyword(s):  
High Frequency ◽  
Selection Pressure ◽  
Evolutionary Dynamics ◽  
Point Mutations ◽  
Selective Advantage ◽  
Fine Tuning ◽  
Spike Glycoprotein ◽  
Enveloped Viruses ◽  
Glycosylation Sites ◽  
Over Time

SARS-CoV-2, responsible for the current COVID-19 pandemic that claimed over 5.0 million lives, belongs to a class of enveloped viruses that undergo quick evolutionary adjustments under selection pressure. Numerous variants have emerged in SARS-CoV-2, posing a serious challenge to the global vaccination effort and COVID-19 management. The evolutionary dynamics of this virus are only beginning to be explored. In this work, we have analysed 1.79 million spike glycoprotein sequences of SARS-CoV-2 and found that the virus is fine-tuning the spike with numerous amino acid insertions and deletions (indels). Indels seem to have a selective advantage as the proportions of sequences with indels steadily increased over time, currently at over 89%, with similar trends across countries/variants. There were as many as 420 unique indel positions and 447 unique combinations of indels. Despite their high frequency, indels resulted in only minimal alteration of N-glycosylation sites, including both gain and loss. As indels and point mutations are positively correlated and sequences with indels have significantly more point mutations, they have implications in the evolutionary dynamics of the SARS-CoV-2 spike glycoprotein.

scholarly journals Evolutionary dynamics of indels in SARS-CoV-2 spike glycoprotein

2021 ◽  
Author(s):  
R. Shyama Prasad Rao ◽  
Nagib Ahsan ◽  
Chunhui Xu ◽  
Lingtao Su ◽  
Jacob Verburgt ◽  
...  
Keyword(s):  
High Frequency ◽  
Selection Pressure ◽  
Evolutionary Dynamics ◽  
Point Mutations ◽  
Selective Advantage ◽  
Fine Tuning ◽  
Spike Glycoprotein ◽  
Enveloped Viruses ◽  
Glycosylation Sites ◽  
Over Time

SARS-CoV-2, responsible for the current COVID-19 pandemic that claimed over 4.2 million lives, belongs to a class of enveloped viruses that undergo quick evolutionary adjustments under selection pressure. Numerous variants have emerged in SARS-CoV-2 that are currently posing a serious challenge to the global vaccination effort and COVID-19 management. The evolutionary dynamics of this virus are only beginning to be explored. In this work, we have analysed 1.79 million spike glycoprotein sequences of SARS-CoV-2 and found that the virus is fine-tuning the spike with numerous amino acid insertions and deletions (indels). Indels seem to have a selective advantage as the proportions of sequences with indels were steadily increasing over time, currently at over 89%, with similar trends across countries/variants. There were as many as 420 unique indel positions and 447 unique combinations of indels. Despite their high frequency, indels resulted in only minimal alteration, including both gain and loss, of N-glycosylation sites. As indels and point mutations are positively correlated and sequences with indels have significantly more point mutations, they have implications in the context of evolutionary dynamics of the SARS-CoV-2 spike glycoprotein.

scholarly journals Effects of Basic Amino Acids and Their Derivatives on SARS-CoV-2 and Influenza-A Virus Infection

Viruses ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1301
Author(s):  
Ivonne Melano ◽  
Li-Lan Kuo ◽  
Yan-Chung Lo ◽  
Po-Wei Sung ◽  
Ni Tien ◽  
...  
Keyword(s):  
Amino Acids ◽  
Virus Infection ◽  
Influenza A Virus ◽  
Influenza A ◽  
Enveloped Viruses ◽  
Virus Attachment ◽  
Basic Amino Acids ◽  
Ester Derivative ◽  
Endosomal Acidification

Amino acids have been implicated with virus infection and replication. Here, we demonstrate the effects of two basic amino acids, arginine and lysine, and their ester derivatives on infection of two enveloped viruses, SARS-CoV-2, and influenza A virus. We found that lysine and its ester derivative can efficiently block infection of both viruses in vitro. Furthermore, the arginine ester derivative caused a significant boost in virus infection. Studies on their mechanism of action revealed that the compounds potentially disturb virus uncoating rather than virus attachment and endosomal acidification. Our findings suggest that lysine supplementation and the reduction of arginine-rich food intake can be considered as prophylactic and therapeutic regimens against these viruses while also providing a paradigm for the development of broad-spectrum antivirals.

scholarly journals Capturing Enveloped Viruses on Affinity Grids for Downstream Cryo-Electron Microscopy Applications

2013 ◽  
Vol 20 (1) ◽  
pp. 164-174 ◽  
Author(s):  
Gabriella Kiss ◽  
Xuemin Chen ◽  
Melinda A. Brindley ◽  
Patricia Campbell ◽  
Claudio L. Afonso ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Measles Virus ◽  
Influenza A ◽  
Electron Tomography ◽  
Three Dimensional ◽  
Nitrilotriacetic Acid ◽  
Dimensional Structure ◽  
Enveloped Viruses ◽  
Cryo Electron Microscopy ◽  
Human Immunodeficiency Virus Virus

AbstractElectron microscopy (EM), cryo-electron microscopy (cryo-EM), and cryo-electron tomography (cryo-ET) are essential techniques used for characterizing basic virus morphology and determining the three-dimensional structure of viruses. Enveloped viruses, which contain an outer lipoprotein coat, constitute the largest group of pathogenic viruses to humans. The purification of enveloped viruses from cell culture presents certain challenges. Specifically, the inclusion of host-membrane-derived vesicles, the complete destruction of the viruses, and the disruption of the internal architecture of individual virus particles. Here, we present a strategy for capturing enveloped viruses on affinity grids (AG) for use in both conventional EM and cryo-EM/ET applications. We examined the utility of AG for the selective capture of human immunodeficiency virus virus-like particles, influenza A, and measles virus. We applied nickel-nitrilotriacetic acid lipid layers in combination with molecular adaptors to selectively adhere the viruses to the AG surface. This further development of the AG method may prove essential for the gentle and selective purification of enveloped viruses directly onto EM grids for ultrastructural analyses.

scholarly journals The importance of antineuraminidase antibodies in resistance to influenza A and immunologic memory for their synthesis

1983 ◽  
Vol 91 (1) ◽  
pp. 131-138 ◽  
Author(s):  
A. N. Naikhin ◽  
I. M. Tsaritsina ◽  
E. V. Oleinikova ◽  
L. G. Syrodoeva ◽  
N. L. Korchanova ◽  
...  
Keyword(s):  
Protective Effect ◽  
Influenza A ◽  
Natural Infection ◽  
Haemagglutination Inhibition ◽  
Surface Antigens ◽  
Antigenic Structure ◽  
Immunologic Memory ◽  
Antibody Synthesis ◽  
Influenza A H1n1 ◽  
Simplified Method

SUMMARYEight hundred and seventy-seven sera from 360 adults aged 18–50 who were under permanent observation from October 1980 to March 1981 have been studied by haemagglutination-inhibition (HI) and erythrocyte elution-inhibition (EI) tests – a simplified method of antineuraminidase antibody titration. It was demonstrated in some subjects infected with influenza A H1N1 and H3N2 viruses that the antibody rise was to one of the surface antigens only – haemagglutinin or neuraminidase. These subjects made up 5·2–25·8% of all examinees. The protective effect of antibodies to neuraminidase was similar to that of antihaemagglutinins. Interaction of both types of antibodies was observed in protection against the disease. Data have been obtained on the influence of antineuraminidase antibodies in decreasing the severity of natural infection with influenza A.A study of heterologous immunologic responses to haemagglutinin and neuraminidase among persons immunized with live influenza A H1N1 and H3N2 vaccines and among children naturally infected with influenza A H3N2 demonstrated the presence of immunologic memory for antineuraminidase antibody synthesis. Thus, the suggestion of a common antigenic structure for neuraminidase Nl and N2 is made.

Inequality, Exclusion, and Tolerance for Political Dissent in Latin America

2021 ◽  
pp. 001041402199716
Author(s):  
Jana Morgan ◽  
Nathan J. Kelly
Keyword(s):  
Latin America ◽  
Public Opinion ◽  
Social Inclusion ◽  
Political Tolerance ◽  
Time Analysis ◽  
Political Dissent ◽  
Structural Context ◽  
Democratic Rights ◽  
Over Time ◽  
Cross National

Although many countries meet electoral standards of democracy, often these regimes fail to promote social inclusion or meaningful representation. We argue that systems of exclusion have deleterious consequences for how people think about democracy, undermining tolerance for political dissent. Using cross-national public opinion data together with contextual measures of economic and political marginalization along ethnoracial lines, we evaluate the relationships between exclusion and political tolerance across Latin America. Over-time analysis in Bolivia further probes the mechanisms linking exclusion to intolerance. We find that tolerance of dissent is depressed where ethnoracial hierarchies are pronounced. We advance understanding of oft-unexplained society-level differences in political tolerance and emphasize the importance of the macro-structural context in shaping citizens’ commitments to basic democratic rights.

scholarly journals Hierarchy among Viral RNA (vRNA) Segments in Their Role in vRNA Incorporation into Influenza A Virions

2006 ◽  
Vol 80 (5) ◽  
pp. 2318-2325 ◽  
Author(s):  
Yukiko Muramoto ◽  
Ayato Takada ◽  
Ken Fujii ◽  
Takeshi Noda ◽  
Kiyoko Iwatsuki-Horimoto ◽  
...  
Keyword(s):  
Influenza A ◽  
Fluorescent Protein ◽  
Virus Assembly ◽  
Viral Rna ◽  
Green Fluorescent Protein Gene ◽  
Influenza A Viruses ◽  
Coding Regions ◽  
Virion Incorporation ◽  
Green Fluorescent ◽  
Efficient Viral Replication

ABSTRACT The genome of influenza A viruses comprises eight negative-strand RNA segments. Although all eight segments must be present in cells for efficient viral replication, the mechanism(s) by which these viral RNA (vRNA) segments are incorporated into virions is not fully understood. We recently found that sequences at both ends of the coding regions of the HA, NA, and NS vRNA segments of A/WSN/33 play important roles in the incorporation of these vRNAs into virions. In order to similarly identify the regions of the PB2, PB1, and PA vRNAs of this strain that are critical for their incorporation, we generated a series of mutant vRNAs that possessed the green fluorescent protein gene flanked by portions of the coding and noncoding regions of the respective segments. For all three polymerase segments, deletions at the ends of their coding regions decreased their virion incorporation efficiencies. More importantly, these regions not only affected the incorporation of the segment in which they reside, but were also important for the incorporation of other segments. This effect was most prominent with the PB2 vRNA. These findings suggest a hierarchy among vRNA segments for virion incorporation and may imply intersegment association of vRNAs during virus assembly.

scholarly journals Differential Induction of Type I and Type III Interferons by Swine and Human Origin H1N1 Influenza A Viruses in Porcine Airway Epithelial Cells

PLoS ONE ◽  
2015 ◽  
Vol 10 (9) ◽  
pp. e0138704 ◽  
Author(s):  
Venkatramana D. Krishna ◽  
Erin Roach ◽  
Nathan A. Zaidman ◽  
Angela Panoskaltsis-Mortari ◽  
Jessica H. Rotschafer ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Influenza A ◽  
H1n1 Influenza ◽  
Airway Epithelial Cells ◽  
Type I ◽  
Airway Epithelial ◽  
Human Origin ◽  
Influenza A Viruses ◽  
Type Iii ◽  
Differential Induction

scholarly journals Prolonged Evolution of Virus-Specific Memory T Cell Immunity after Severe Avian Influenza A (H7N9) Virus Infection

2018 ◽  
Vol 92 (17) ◽  
Author(s):  
Min Zhao ◽  
Junbo Chen ◽  
Shuguang Tan ◽  
Tao Dong ◽  
Hui Jiang ◽  
...  
Keyword(s):  
T Cells ◽  
T Cell ◽  
Avian Influenza ◽  
Influenza A ◽  
T Cell Immunity ◽  
H7n9 Virus ◽  
Specific Memory ◽  
Cell Immunity ◽  
H7n9 Infection ◽  
Over Time

ABSTRACT Since 2013, influenza A H7N9 virus has emerged as the most common avian influenza virus subtype causing human infection, and it is associated with a high fatality risk. However, the characteristics of immune memory in patients who have recovered from H7N9 infection are not well understood. We assembled a cohort of 45 H7N9 survivors followed for up to 15 months after infection. Humoral and cellular immune responses were analyzed in sequential samples obtained at 1.5 to 4 months, 6 to 8 months, and 12 to 15 months postinfection. H7N9-specific antibody concentrations declined over time, and protective antibodies persisted longer in severely ill patients admitted to the intensive care unit (ICU) and patients presenting with acute respiratory distress syndrome (ARDS) than in patients with mild disease. Frequencies of virus-specific gamma interferon (IFN-γ)-secreting T cells were lower in critically ill patients requiring ventilation than in patients without ventilation within 4 months after infection. The percentages of H7N9-specific IFN-γ-secreting T cells tended to increase over time in patients ≥60 years or in critically ill patients requiring ventilation. Elevated levels of antigen-specific CD8+ T cells expressing the lung-homing marker CD49a were observed at 6 to 8 months after H7N9 infection compared to those in samples obtained at 1.5 to 4 months. Our findings indicate the prolonged reconstruction and evolution of virus-specific T cell immunity in older or critically ill patients and have implications for T cell-directed immunization strategies. IMPORTANCE Avian influenza A H7N9 virus remains a major threat to public health. However, no previous studies have determined the characteristics and dynamics of virus-specific T cell immune memory in patients who have recovered from H7N9 infection. Our findings showed that establishment of H7N9-specific T cell memory after H7N9 infection was prolonged in older and severely affected patients. Severely ill patients mounted lower T cell responses in the first 4 months after infection, while T cell responses tended to increase over time in older and severely ill patients. Higher levels of antigen-specific CD8+ T cells expressing the lung-homing marker CD49a were detected at 6 to 8 months after infection. Our results indicated a long-term impact of H7N9 infection on virus-specific memory T cells. These findings advance our understanding of the dynamics of virus-specific memory T cell immunity after H7N9 infection, which is relevant to the development of T cell-based universal influenza vaccines.

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