The cap-binding site of influenza virus protein PB2 as a drug target

2016 ◽  
Vol 72 (2) ◽  
pp. 245-253 ◽  
Author(s):  
Chelsea Severin ◽  
Tales Rocha de Moura ◽  
Yong Liu ◽  
Keqin Li ◽  
Xiaofeng Zheng ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Binding Site ◽  
Structural Changes ◽  
Hydrophobic Interactions ◽  
Influenza Viruses ◽  
Virus Protein ◽  
Mrna Transcription ◽  
Viral Mrnas ◽  
Multiple Strains ◽  
Virus Strains

The RNA polymerase of influenza virus consists of three subunits: PA, PB1 and PB2. It uses a unique `cap-snatching' mechanism for the transcription of viral mRNAs. The cap-binding domain of the PB2 subunit (PB2cap) in the viral polymerase binds the cap of a host pre-mRNA molecule, while the endonuclease of the PA subunit cleaves the RNA 10–13 nucleotides downstream from the cap. The capped RNA fragment is then used as the primer for viral mRNA transcription. The structure of PB2cap from influenza virus H1N1 A/California/07/2009 and of its complex with the cap analog m7GTP were solved at high resolution. Structural changes are observed in the cap-binding site of this new pandemic influenza virus strain, especially the hydrophobic interactions between the ligand and the target protein. m7GTP binds deeper in the pocket than some other virus strains, much deeper than the host cap-binding proteins. Analysis of the new H1N1 structures and comparisons with other structures provide new insights into the design of small-molecule inhibitors that will be effective against multiple strains of both type A and type B influenza viruses.

Inhibition of ciliary activity in organ cultures of ferret trachea in reference to genetic and biological characters of influenza virus strains

1982 ◽  
Vol 28 (7) ◽  
pp. 809-814 ◽  
Author(s):  
P. Diaz-Rodriguez ◽  
A. Boudreault
Keyword(s):  
Influenza Virus ◽  
Influenza Viruses ◽  
Influenza Vaccines ◽  
Ciliary Activity ◽  
Organ Cultures ◽  
Preliminary Screening ◽  
Cold Adapted ◽  
Activity Inhibition ◽  
Biological Characters ◽  
Virus Strains

As reported previously, attenuated stable inhibitor-resistant influenza viruses can be screened by a 50% ciliary activity inhibition test in ferret tracheal organ cultures. This test was further applied to 5 attenuated cold-adapted influenza strains and to 11 strains with known a percentage of RNA–RNA hybridization with the parental A/PR/8/34 (H0N1) virus strain. Again, with one exception, attenuated strains could be clearly differentiated from virulent ones. It was concluded that virulence of influenza strains for man can be detected using this test regardless of the techniques used to prepare attenuated variants. A preliminary screening of attenuated candidates for live influenza vaccines can be achieved with confidence on ferret tracheal organ cultures.

scholarly journals Structural basis of influenza virus fusion inhibition by the antiviral drug Arbidol

2016 ◽  
Vol 114 (2) ◽  
pp. 206-214 ◽  
Author(s):  
Rameshwar U. Kadam ◽  
Ian A. Wilson
Keyword(s):  
Influenza Virus ◽  
Broad Spectrum ◽  
Hydrophobic Interactions ◽  
Antiviral Drug ◽  
Binding Mode ◽  
Influenza Viruses ◽  
Structural Basis ◽  
Salt Bridges ◽  
Fusion Inhibition ◽  
Conformational Rearrangements

The broad-spectrum antiviral drug Arbidol shows efficacy against influenza viruses by targeting the hemagglutinin (HA) fusion machinery. However, the structural basis of the mechanism underlying fusion inhibition by Arbidol has remained obscure, thereby hindering its further development as a specific and optimized influenza therapeutic. We determined crystal structures of Arbidol in complex with influenza virus HA from pandemic 1968 H3N2 and recent 2013 H7N9 viruses. Arbidol binds in a hydrophobic cavity in the HA trimer stem at the interface between two protomers. This cavity is distal to the conserved epitope targeted by broadly neutralizing stem antibodies and is ∼16 Å from the fusion peptide. Arbidol primarily makes hydrophobic interactions with the binding site but also induces some conformational rearrangements to form a network of inter- and intraprotomer salt bridges. By functioning as molecular glue, Arbidol stabilizes the prefusion conformation of HA that inhibits the large conformational rearrangements associated with membrane fusion in the low pH of the endosome. This unique binding mode compared with the small-molecule inhibitors of other class I fusion proteins enhances our understanding of how small molecules can function as fusion inhibitors and guides the development of broad-spectrum therapeutics against influenza virus.

scholarly journals Immunomic Analysis of the Repertoire of T-Cell Specificities for Influenza A Virus in Humans

2008 ◽  
Vol 82 (24) ◽  
pp. 12241-12251 ◽  
Author(s):  
Erika Assarsson ◽  
Huynh-Hoa Bui ◽  
John Sidney ◽  
Qing Zhang ◽  
Jean Glenn ◽  
...  
Keyword(s):  
Influenza Virus ◽  
T Cell ◽  
Influenza A Virus ◽  
Influenza A ◽  
T Cell Responses ◽  
Class Ii ◽  
Influenza Viruses ◽  
Class I ◽  
Cell Responses ◽  
Virus Strains

ABSTRACT Continuing antigenic drift allows influenza viruses to escape antibody-mediated recognition, and as a consequence, the vaccine currently in use needs to be altered annually. Highly conserved epitopes recognized by effector T cells may represent an alternative approach for the generation of a more universal influenza virus vaccine. Relatively few highly conserved epitopes are currently known in humans, and relatively few epitopes have been identified from proteins other than hemagglutinin and nucleoprotein. This prompted us to perform a study aimed at identifying a set of human T-cell epitopes that would provide broad coverage against different virus strains and subtypes. To provide coverage across different ethnicities, seven different HLA supertypes were considered. More than 4,000 peptides were selected from a panel of 23 influenza A virus strains based on predicted high-affinity binding to HLA class I or class II and high conservancy levels. Peripheral blood mononuclear cells from 44 healthy human blood donors were tested for reactivity against HLA-matched peptides by using gamma interferon enzyme-linked immunospot assays. Interestingly, we found that PB1 was the major target for both CD4+ and CD8+ T-cell responses. The 54 nonredundant epitopes (38 class I and 16 class II) identified herein provided high coverage among different ethnicities, were conserved in the majority of the strains analyzed, and were consistently recognized in multiple individuals. These results enable further functional studies of T-cell responses during influenza virus infection and provide a potential base for the development of a universal influenza vaccine.

scholarly journals The analysis of the monoclonal immune response to influenza virus. II. The antigenicity of the viral hemagglutinin.

1976 ◽  
Vol 144 (4) ◽  
pp. 985-995 ◽  
Author(s):  
W Gerhard
Keyword(s):  
Immune Response ◽  
Influenza Virus ◽  
Monoclonal Antibodies ◽  
Influenza Viruses ◽  
Antigenic Determinants ◽  
Humoral Immune ◽  
Viral Hemagglutinin ◽  
Or Groups ◽  
Virus Strains

The antigenicity of the hemagglutinins (HA) of five influenza viruses of the A0 and A1 subtypes has been analyzed by means of monoclonal antibodies of murine origin produced in vitro. Secondary monoclonal anti-HA(PR8) antibodies were able to differentiate 14 antigenic determinants (or groups of determinants) on the HA of five influenza virus strains of the A0 and A1 subtypes. Taking into account that certain pairs of determinants delineated on heterologous HA may reflect the heterogeneity of the humoral immune response to a single homologous determinant, the presence of at least eight determinants (host cell-derived determinants not included) on the homologous HA of PR8 and probably on the HA of influenza viruses in general is postulated. Three types of HA-determinants of A0 and A1 influenza virus strains could be distinguished: strain-specific, partially shared, and determinant(s) common to all five virus strains tested. Roughly 40, 55, and 5%, respectively, of the secondary anti-PR8 antibodies of BALB/c mice were directed against determinants belonging to either of the three types.

scholarly journals Drug repositioning of Clopidogrel or Triamterene to inhibit influenza virus replication in vitro

PLoS ONE ◽  
2021 ◽  
Vol 16 (10) ◽  
pp. e0259129
Author(s):  
Nichole Orr-Burks ◽  
Jackelyn Murray ◽  
Kyle V. Todd ◽  
Abhijeet Bakre ◽  
Ralph A. Tripp
Keyword(s):  
Influenza Virus ◽  
Virus Replication ◽  
Drug Repositioning ◽  
Antiviral Drug ◽  
Influenza Viruses ◽  
Influenza Virus Replication ◽  
Approved Drugs ◽  
Multiple Strains ◽  
Tract Infections

Influenza viruses cause respiratory tract infections and substantial health concerns. Infection may result in mild to severe respiratory disease associated with morbidity and some mortality. Several anti-influenza drugs are available, but these agents target viral components and are susceptible to drug resistance. There is a need for new antiviral drug strategies that include repurposing of clinically approved drugs. Drugs that target cellular machinery necessary for influenza virus replication can provide a means for inhibiting influenza virus replication. We used RNA interference screening to identify key host cell genes required for influenza replication, and then FDA-approved drugs that could be repurposed for targeting host genes. We examined the effects of Clopidogrel and Triamterene to inhibit A/WSN/33 (EC50 5.84 uM and 31.48 uM, respectively), A/CA/04/09 (EC50 6.432 uM and 3.32 uM, respectively), and B/Yamagata/16/1988 (EC50 0.28 uM and 0.11 uM, respectively) replication. Clopidogrel and Triamterene provide a druggable approach to influenza treatment across multiple strains and subtypes.

scholarly journals Development of a Pan-H1 Influenza Vaccine

2018 ◽  
Vol 92 (22) ◽  
Author(s):  
Nicole Darricarrère ◽  
Svetlana Pougatcheva ◽  
Xiaochu Duan ◽  
Rebecca S. Rudicell ◽  
Te-Hui Chou ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Immune Responses ◽  
Influenza Vaccine ◽  
Seasonal Influenza ◽  
Influenza Viruses ◽  
Influenza Vaccines ◽  
The Past ◽  
Individual Strain ◽  
Humoral Responses ◽  
Virus Strains

ABSTRACT The efficacy of current seasonal influenza vaccines varies greatly, depending on the match to circulating viruses. Although most vaccines elicit strain-specific responses, some present cross-reactive epitopes that elicit antibodies against diverse viruses and remain unchanged and effective for several years. To determine whether combinations of specific H1 hemagglutinin (HA) antigens stimulate immune responses that protect against diverse H1 influenza viruses, we evaluated the antibody responses elicited by HA-ferritin nanoparticles derived from six evolutionarily divergent H1 sequences and two computationally optimized broadly reactive antigen (COBRA) HA antigens. Humoral responses were assessed against a panel of 16 representative influenza virus strains from the past 80 years. HAs from the strains A/NewCaledonia/20/1999 (NC99), A/California/04/2009 (CA09), A/HongKong/117/1977 (HK77), COBRA X6, or P1 elicited neutralization against diverse strains, and a combination of three wild-type HA or two COBRA HA nanoparticles conferred significant additional breadth beyond that observed with any individual strain. Therefore, combinations of H1 HAs may constitute a pan-H1 influenza vaccine. IMPORTANCE Seasonal influenza vaccines elicit strain-specific immune responses designed to protect against circulating viruses. Because these vaccines often show limited efficacy, the search for a broadly protective seasonal vaccine remains a priority. Among different influenza virus subtypes, H1N1 has long been circulating in humans and has caused pandemic outbreaks. In order to assess the potential of a multivalent HA combination vaccine to improve the breadth of protection against divergent H1N1 viruses, HA-ferritin nanoparticles were made and evaluated in mice against a panel of historical and contemporary influenza virus strains. Trivalent combinations of H1 nanoparticles improved the breadth of immunity against divergent H1 influenza viruses.

scholarly journals N-Linked Glycans and K147 Residue on Hemagglutinin Synergize To Elicit Broadly Reactive H1N1 Influenza Virus Antibodies

2019 ◽  
Vol 94 (6) ◽  
Author(s):  
Ying Huang ◽  
Simon O. Owino ◽  
Corey J. Crevar ◽  
Donald M. Carter ◽  
Ted M. Ross
Keyword(s):  
Amino Acids ◽  
Influenza Virus ◽  
Binding Site ◽  
Receptor Binding ◽  
Hemagglutination Inhibition ◽  
Vaccine Development ◽  
H1n1 Influenza ◽  
Influenza Viruses ◽  
Wild Type ◽  
Receptor Binding Site

ABSTRACT Vaccination is the most effective way to prevent influenza virus infections. However, the diversity of antigenically distinct isolates is a challenge for vaccine development. In order to overcome the antigenic variability and improve the protective efficacy of influenza vaccines, our research group has pioneered the development of computationally optimized broadly reactive antigens (COBRA) for hemagglutinin (HA). Two candidate COBRA HA vaccines, P1 and X6, elicited antibodies with differential patterns of hemagglutination inhibition (HAI) activity against a panel of H1N1 influenza viruses. In order to better understand how these HA antigens elicit broadly reactive immune responses, epitopes in the Cb, Sa, or Sb antigenic sites of seasonal-like and pandemic-like wild-type or COBRA HA antigens were exchanged with homologous regions in the COBRA HA proteins to determine which regions and residues were responsible for the elicited antibody profile. Mice were vaccinated with virus-like particles (VLPs) expressing one of the 12 modified HA antigens (designated V1 to V12), COBRA HA antigens, or wild-type HA antigens. The elicited antisera was assessed for hemagglutination inhibition activity against a panel of historical seasonal-like and pandemic-like H1N1 influenza viruses. Primarily, the pattern of glycosylation sites and residues in the Sa antigenic region, around the receptor binding site (RBS), served as signatures for the elicitation of broadly reactive antibodies by these HA immunogens. Mice were vaccinated with VLPs expressing HA antigens that lacked a glycosylation site at residue 144 and a deleted lysine at position 147 residue were more effective at protecting against morbidity and mortality following infection with pandemic-like and seasonal-like H1N1 influenza viruses. IMPORTANCE There is a great need to develop broadly reactive or universal vaccines against influenza viruses. Advanced, next-generation hemagglutinin (HA) head-based vaccines that elicit protective antibodies against H1N1 influenza viruses have been developed. This study focused on understanding the specific amino acids around the receptor binding site (RBS) that were important in elicitation of these broadly reactive antibodies. Specific glycan sites and amino acids located at the tip of the HA molecule enhanced the elicitation of these broadly reactive antibodies. A better understanding of the HA structures around the RBS will lead to more effective HA immunogens.

scholarly journals Influenza Virus Infection Induces a Narrow Antibody Response in Children but a Broad Recall Response in Adults

mBio ◽  
2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Philip Meade ◽  
Guillermina Kuan ◽  
Shirin Strohmeier ◽  
Hannah E. Maier ◽  
Fatima Amanat ◽  
...  
Keyword(s):  
Immune Response ◽  
Influenza Virus ◽  
Immune Responses ◽  
Protein Microarray ◽  
Natural Infection ◽  
Influenza Virus Infection ◽  
Virus Protein ◽  
Recall Response ◽  
Virus Strains ◽  
Group 1

ABSTRACT In contrast to influenza virus vaccination, natural infection induces long-lived and relatively broad immune responses. However, many aspects of the antibody response to natural infection are not well understood. Here, we assessed the immune response after H1N1 influenza virus infection in children and adults in a Nicaraguan household transmission study using an influenza virus protein microarray (IVPM). This technology allows us to simultaneously measure IgG and IgA antibody responses to hemagglutinins of many different virus strains and subtypes quantitatively with a high throughput. We found that children under 6 years of age responded to natural infection with a relatively narrow response that targeted mostly the hemagglutinin of the strain that caused the infection. Adults, however, have a much broader response, including a boost in antibodies to many group 1 subtype hemagglutinins. Also, a strong recall response against historic H1 hemagglutinins that share the K133 epitope with the pandemic H1N1 virus was observed. Of note, some children, while responding narrowly within H1 and group 1 hemagglutinins, induced a boost to H3 and other group 2 hemagglutinins when infected with H1N1 when they had experienced an H3N2 infection earlier in life. This is an interesting phenomenon providing evidence for immune imprinting and a significant new insight which might be leveraged in future universal influenza virus vaccine strategies. Finally, preexisting immunity to pandemic H1 hemagglutinins was significantly associated with protection from infection in both children and adults. In adults, preexisting immunity to non-H1 group 1 hemagglutinins was also significantly associated with protection from infection. IMPORTANCE It is known since Thomas Francis, Jr. published his first paper on original antigenic sin in 1960 that the first infection(s) with influenza virus leaves a special immunological imprint which shapes immune responses to future infections with antigenically related influenza virus strains. Imprinting has been implicated in both protective effects as well as blunting of the immune response to vaccines. Despite the fact that this phenomenon was already described almost 60 years ago, we have very little detailed knowledge of the characteristics and breadth of the immune response to the first exposure(s) to influenza virus in life and how this compares to later exposure as adults. Here, we investigate these immune responses in detail using an influenza virus protein microarray. While our findings are mostly descriptive in nature and based on a small sample size, they provide a strong basis for future large-scale studies to better understand imprinting effects.

scholarly journals New aspects of influenza viruses.

1992 ◽  
Vol 5 (1) ◽  
pp. 74-92 ◽  
Author(s):  
M W Shaw ◽  
N H Arden ◽  
H F Maassab
Keyword(s):  
Influenza Virus ◽  
Antigenic Variation ◽  
Antiviral Agents ◽  
Molecular Techniques ◽  
Influenza Viruses ◽  
Virus Infections ◽  
Promising Alternative ◽  
Live Attenuated Influenza Virus ◽  
Virus Strains ◽  
Substantial Morbidity

Influenza virus infections continue to cause substantial morbidity and mortality with a worldwide social and economic impact. The past five years have seen dramatic advances in our understanding of viral replication, evolution, and antigenic variation. Genetic analyses have clarified relationships between human and animal influenza virus strains, demonstrating the potential for the appearance of new pandemic reassortants as hemagglutinin and neuraminidase genes are exchanged in an intermediate host. Clinical trials of candidate live attenuated influenza virus vaccines have shown the cold-adapted reassortants to be a promising alternative to the currently available inactivated virus preparations. Modern molecular techniques have allowed serious consideration of new approaches to the development of antiviral agents and vaccines as the functions of the viral genes and proteins are further elucidated. The development of techniques whereby the genes of influenza viruses can be specifically altered to investigate those functions will undoubtedly accelerate the pace at which our knowledge expands.

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