#Influenza viruses that require 10 #genomic segments as #antiviral #therapeutics (PLOS Pathog., abstract)

[Source: PLOS Pathogens, full page: (LINK). Abstract, edited.]


Influenza viruses that require 10 genomic segments as antiviral therapeutics

Alfred T. Harding , Griffin D. Haas , Benjamin S. Chambers, Nicholas S. Heaton


Published: November 15, 2019 / DOI: https://doi.org/10.1371/journal.ppat.1008098 / This is an uncorrected proof.



Influenza A viruses (IAVs) encode their genome across eight, negative sense RNA segments. During viral assembly, the failure to package all eight segments, or packaging a mutated segment, renders the resulting virion incompletely infectious. It is known that the accumulation of these defective particles can limit viral disease by interfering with the spread of fully infectious particles. In order to harness this phenomenon therapeutically, we defined which viral packaging signals were amenable to duplication and developed a viral genetic platform which produced replication competent IAVs that require up to two additional artificial genome segments for full infectivity. The modified and artificial genome segments propagated by this approach are capable of acting as “decoy” segments that, when packaged by coinfecting wild-type viruses, lead to the production of non-infectious viral particles. Although IAVs which require 10 genomic segments for full infectivity are able to replicate themselves and spread in vivo, their genomic modifications render them avirulent in mice. Administration of these viruses, both prophylactically and therapeutically, was able to rescue animals from a lethal influenza virus challenge. Together, our results show that replicating IAVs designed to propagate and spread defective genomic segments represent a potent anti-influenza biological therapy that can target the conserved process of particle assembly to limit viral disease.


Author summary

Influenza infections are best prevented via prophylactic vaccination. Vaccination, however, is incompletely efficacious, necessitating the use of anti-influenza therapeutics. To date, several different classes of anti-influenza therapeutics have been developed and used in order to combat these infections. Unfortunately, the incidence of influenza resistance to many of these therapeutics has begun to rise, necessitating the development of new strategies. One such strategy is to mimic the activity of naturally occurring viral particles that harbor defective genomes. These defective interfering particles have the ability to interfere with productive viral assembly, preventing the spread of influenza viruses across the respiratory tract. Furthermore, given the manner in which they target influenza segment packaging, a conserved feature of all influenza A viruses, resistance to this therapeutic strategy is unlikely. Here, we report the development of a genetic platform that allows the production of replicating influenza viruses which require 10 genomic segments to be fully infectious. These viruses are capable of amplifying themselves in isolation, but coinfection with a wild-type virus leads to segment exchange and compromises the spread of both viruses. This interference, while mechanistically distinct from naturally occurring defective particles, was able to target the same viral process and rescue animals exposed to an otherwise lethal viral infection. This viral-based approach may represent a cost effective and scalable method to generate effective anti-influenza therapeutics when vaccines or antiviral drugs become ineffective due to the acquisition of viral resistance mutations.


Citation: Harding AT, Haas GD, Chambers BS, Heaton NS (2019) Influenza viruses that require 10 genomic segments as antiviral therapeutics. PLoS Pathog 15(11): e1008098. https://doi.org/10.1371/journal.ppat.1008098

Editor: Carolina B. Lopez, University of Pennsylvania, UNITED STATES

Received: February 7, 2019; Accepted: September 20, 2019; Published: November 15, 2019

Copyright: © 2019 Harding et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: N.S.H. is partially supported by federal funds from the National Institute of Allergy and Infectious Diseases, National Institutes of Health, Department of Health and Human Services, under CEIRS Contract No. HHSN272201400005C. A.T.H and B.S.C. were supported by NIH training grant T32-CA009111. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Keywords: Influenza A.


#Hemagglutinin head-specific responses dominate over stem-specific responses following prime boost with mismatched #vaccines (JCI Insight, abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

JCI Insight. 2019 Nov 14;4(22). pii: 129035. doi: 10.1172/jci.insight.129035.

Hemagglutinin head-specific responses dominate over stem-specific responses following prime boost with mismatched vaccines.

Jegaskanda S1,2, Andrews SF3, Wheatley AK2,3, Yewdell JW4, McDermott AB3, Subbarao K1.

Author information: 1 Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA. 2 Department of Microbiology and Immunology, University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia. 3 Vaccine Research Center and. 4 Laboratory of Viral Diseases, National Institute of Allergy and Infectious Disease, NIH, Bethesda, Maryland, USA.



Broadly neutralizing Abs targeting the HA stem can provide broad protection against different influenza subtypes, raising the question of how best to elicit such Abs. We have previously demonstrated that vaccination with pandemic live-attenuated influenza vaccine (pLAIV) establishes immune memory for HA head-specific Abs. Here, we determine the extent to which matched versus mismatched LAIV-inactivated subunit vaccine (IIV) prime-boost vaccination elicits stem-specific memory B cells and Abs. We vaccinated African green monkeys with H5N1 pLAIV-pIIV or H5N1 pLAIV followed by seasonal IIV (sIIV) or with H5N1 pLAIV alone and measured Abs and HA-specific B cell responses. While we observed an increase in stem-specific memory B cells, head-specific memory B cell responses were substantially higher than stem-specific responses and were dominant even following boost with mismatched IIV. Neutralizing Abs against heterologous influenza viruses were undetectable. Head-specific B cells from draining lymph nodes exhibited germinal center markers, while stem-specific B cells found in the spleen and peripheral blood did not. Thus, although mismatched prime-boost generated a pool of stem-specific memory B cells, head-specific B cells and serum Abs substantially dominated the immune response. These findings have implications for including full-length native HA in prime-boost strategies intended to induce stem-specific Abs for universal influenza vaccination.

KEYWORDS: Infectious disease; Influenza; Vaccines

PMID: 31723058 DOI: 10.1172/jci.insight.129035

Keywords: Influenza A; H5N1; Vaccines.


#Key #aminoacid residues of #neuraminidase involved in #influenza A virus #entry (Pathog Dis., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Pathog Dis. 2019 Nov 8. pii: ftz063. doi: 10.1093/femspd/ftz063. [Epub ahead of print]

Key amino acid residues of neuraminidase involved in influenza A virus entry.

Chen F1, Liu T1, Xu J1, Huang Y1, Liu S1, Yang J1.

Author information: 1 Guangdong Provincial Key Laboratory of New Drug Screening, Guangzhou Key laboratory of Drug Research for Emerging Virus Prevention and Treatment, School of Pharmaceutical Sciences, Southern Medical University, Guangzhou, China.



Generally, influenza virus neuraminidase (NA) plays a critical role in the release stage of influenza virus. Recently, it has been found that NA may promote influenza virus to access the target cells. However, the mechanism remain unclear. Here, we reported that peramivir indeed possessed anti-influenza A virus (IAV) activity in the stage of viral entry. Importantly, we verified the critical residues of influenza NA involved in the viral entry. As a result, peramivir as an efficient NA inhibitor could suppress the initiation of IAV infection. Furthermore, mutational analysis showed NA might be associated with viral entry via amino acids residues R118, E119, D151, R152, W178, I222, E227, E276, R292 and R371. Our results demonstrated neuraminidase must contain the key amino acid residues can involve in IAV entry.

© FEMS 2019.

KEYWORDS: Influenza A virus; neuraminidase; neuraminidase active site; peramivir; viral entry

PMID: 31702775 DOI: 10.1093/femspd/ftz063

Keywords: Influenza A; Peramivir; Antivirals; Viral pathogenesis.


Mechanistic #Modelling of Multiple #Waves in an #Influenza #Epidemic or #Pandemic (J Theor Biol., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

J Theor Biol. 2019 Nov 4:110070. doi: 10.1016/j.jtbi.2019.110070. [Epub ahead of print]

Mechanistic Modelling of Multiple Waves in an Influenza Epidemic or Pandemic.

Xu B1, Cai J2, He D3, Chowell G4, Xu B5.

Author information: 1 Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China; Joint Center for Global Change Studies, Beijing 100875, China. Electronic address: xu-b15@mails.tsinghua.edu.cn. 2 Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China; Joint Center for Global Change Studies, Beijing 100875, China. Electronic address: cai-j12@mails.tsinghua.edu.cn. 3 Department of Applied Mathematics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (SAR), China. Electronic address: daihai.he@polyu.edu.hk. 4 Department of Population Health Sciences, School of Public Health, Georgia State University, Atlanta, Georgia 30303, United States; Division of Inwternational Epidemiology and Population Studies, Fogarty International Center, National Institute of Health, Bethesda, Maryland 20892, United States. Electronic address: gchowell@gsu.edu. 5 Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing 100084, China; Joint Center for Global Change Studies, Beijing 100875, China. Electronic address: bingxu@tsinghua.edu.cn.



Multiple-wave outbreaks have been documented for influenza pandemics particularly in the temperate zone, and occasionally for seasonal influenza epidemics in the tropical zone. The mechanisms shaping multiple-wave influenza outbreaks are diverse but are yet to be summarized in a systematic fashion. For this purpose, we described 12 distinct mechanistic models, among which five models were proposed for the first time, that support two waves of infection in a single influenza season, and classified them into five categories according to heterogeneities in host, pathogen, space, time and their combinations, respectively. To quantify the number of infection waves, we proposed three metrics that provide robust and intuitive results for real epidemics. Further, we performed sensitivity analyses on key parameters in each model and found that reducing the basic reproduction number or the transmission rate, limiting the addition of susceptible people who are to get the primary infection to infected areas, and limiting the probability of replenishment of people who are to be reinfected in the short term, could decrease the number of infection waves and clinical attack rate. Finally, we introduced a modelling framework to infer the mechanisms driving two-wave outbreaks. A better understanding of two-wave mechanisms could guide public health authorities to develop and implement preparedness plans and deploy control strategies.

Copyright © 2019. Published by Elsevier Ltd.

KEYWORDS: Influenza outbreak; Mechanistic model; Modelling framework; Multiple waves; Number of infection waves

PMID: 31697940 DOI: 10.1016/j.jtbi.2019.110070

Keywords: Influenza A; Pandemic influenza; Mathematical models.


#HA #stability regulates #H1N1 #influenza virus #replication and #pathogenicity in mice by modulating type I #interferon responses in dendritic cells (J Virol., abstract)

[Source: Journal of Virology, full page: (LINK). Abstract, edited.]

HA stability regulates H1N1 influenza virus replication and pathogenicity in mice by modulating type I interferon responses in dendritic cells

Marion Russier, Guohua Yang, Benoit Briard, Victoria Meliopoulos, Sean Cherry, Thirumala-Devi Kanneganti, Stacey Schultz-Cherry, Peter Vogel, Charles J. Russell

DOI: 10.1128/JVI.01423-19



Hemagglutinin (HA) stability, or the pH at which HA is activated to cause membrane fusion, has been associated with the replication, pathogenicity, transmissibility, and interspecies adaptation of influenza A viruses. Here, we investigated mechanisms by which a destabilizing HA mutation, Y17H (activation pH 6.0), attenuates virus replication and pathogenicity in DBA/2 mice, compared to wild-type (WT; activation pH 5.5). Extracellular lung pH was measured to be near neutral (pH 6.9–7.5). WT and Y17H viruses had similar environmental stability at pH 7.0; thus, extracellular inactivation was unlikely to attenuate Y17H virus. The Y17H virus had accelerated replication kinetics in MDCK, A549, and Raw264.7 cells when inoculated at an MOI of 3 PFU/cell. The destabilizing mutation also increased early infectivity and type I interferon (IFN) responses in mouse bone marrow–derived dendritic cells (DCs). In contrast, the HA-Y17H mutation reduced replication in murine airway mNEC and mTEC cultures and attenuated virus replication, virus spread, severity of infection, and cellular infiltration in the lungs of mice. Normalizing virus infection and weight loss in mice by inoculating them with Y17H virus at a dose 500-fold higher than that of WT virus revealed that the destabilized mutant virus triggered the upregulation of more host genes and increased type I IFN responses and cytokine expression in DBA/2 mouse lungs. Overall, HA destabilization decreased virulence in mice by boosting early infection in DCs, resulting in greater activation of antiviral responses, including type I IFN. These studies reveal HA stability may regulate pathogenicity by modulating IFN responses.



Diverse influenza A viruses circulate in wild aquatic birds, occasionally infecting farm animals. Rarely, an avian- or swine-origin influenza virus adapts to humans and starts a pandemic. Seasonal and many universal influenza vaccines target the HA surface protein, which is a key component of pandemic influenza. Understanding HA properties needed for replication and pathogenicity in mammals may guide response efforts to control influenza. Some antiviral drugs and broadly reactive influenza vaccines that target the HA protein have suffered resistance due to destabilizing HA mutations that do not compromise replicative fitness in cell culture. Here, we show that despite not compromising fitness in standard cell cultures, a destabilizing H1N1 HA stalk mutation greatly diminishes viral replication and pathogenicity in vivo by modulating type I IFN responses. This encourages targeting the HA stalk with antiviral drugs and vaccines as well as reevaluating previous candidates that were susceptible to destabilizing resistance mutations.

Copyright © 2019 American Society for Microbiology. All Rights Reserved.

Keywords: Influenza A; H1N1; Viral pathogenesis; Interferons.


Locally Acquired #Human #Infection with #Swine-Origin #Influenza A(#H3N2) Variant Virus, #Australia, 2018 (Emerg Infect Dis., abstract)

[Source: US Centers for Disease Control and Prevention (CDC), Emerging Infectious Diseases Journal, full page: (LINK). Abstract, edited.]

Volume 26, Number 1—January 2020 / Dispatch

Locally Acquired Human Infection with Swine-Origin Influenza A(H3N2) Variant Virus, Australia, 2018

Yi-Mo Deng  , Frank Y.K. Wong, Natalie Spirason, Matthew Kaye, Rebecca Beazley, Miguel Grau, Songhua Shan, Vittoria Stevens, Kanta Subbarao, Sheena Sullivan, Ian G. Barr, and Vijaykrishna Dhanasekaran

Author affiliations: World Health Organization Collaborating Centre for Reference and Research on Influenza, Melbourne, Victoria, Australia (Y.M. Deng, N. Spirason, M. Kaye, K. Subbarao, S. Sullivan, I.G. Barr, V. Dhanasekaran); CSIRO Australian Animal Health Laboratory, Geelong, Victoria, Australia (F.Y.K. Wong, S. Shan, V. Stevens); South Australian Department of Health and Wellbeing, Adelaide, South Australia, Australia (R. Beazley); Monash University, Melbourne (M. Grau, V. Dhanasekaran); University of Melbourne, Melbourne (S. Sullivan, I.G. Barr)



In 2018, a 15-year-old female adolescent in Australia was infected with swine influenza A(H3N2) variant virus. The virus contained hemagglutinin and neuraminidase genes derived from 1990s-like human seasonal viruses and internal protein genes from influenza A(H1N1)pdm09 virus, highlighting the potential risk that swine influenza A virus poses to human health in Australia.

Keywords: Swine Influenza; Influenza A; Seasonal Influenza; Reassortant strain; H3N2; H1N1pdm09; Human; Australia.


Recommended #hospital #preparations for future cases and #outbreaks of novel #influenza viruses (Expert Rev Respir Med., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Expert Rev Respir Med. 2019 Oct 25. doi: 10.1080/17476348.2020.1683448. [Epub ahead of print]

Recommended hospital preparations for future cases and outbreaks of novel influenza viruses.

Hui DS1,2, Ng SS1.

Author information: 1 Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Prince of Wales Hospital , Shatin , New Territories , Hong Kong. 2 Stanley Ho Center for Emerging Infectious Diseases, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin , New Territories , Hong Kong.




Seasonal influenza epidemics and periodic pandemics are important causes of morbidity and mortality. Influenza transmits predominantly by respiratory droplets and fomites but opportunistic airborne transmission may occur in the hospital setting due to overcrowding, poor compliance with infection control measures, and performance of aerosol generating procedures.

Areas covered:

This article reviews the risk factors of nosocomial influenza outbreaks and discusses clinical, diagnostic, and treatment aspects of seasonal and avian influenza to facilitate hospital preparations for future influenza outbreaks. Literature search was conducted through PubMed of relevant peer-reviewed full papers in English journals with inclusion of relevant publications by the WHO and US CDC.

Expert opinion:

Accurate and rapid identification of an influenza outbreak is important to facilitate patient care and prevent nosocomial transmission. Timely treatment with a neuraminidase inhibitor (NAI) for adults hospitalized with severe influenza is associated with lower mortality and better clinical outcomes. Baloxavir, a polymerase endonuclease inhibitor, offers a new treatment alternative and its role in combination with NAI for treatment of severe influenza is being investigated. High-dose systemic corticosteroids are associated with worse outcomes in patients with severe influenza. It is important to develop more effective antiviral and immuno-modulating therapies for treatment of influenza infections.

KEYWORDS: avian influenza; nosocomial transmission; seasonal; treatment

PMID: 31648548 DOI: 10.1080/17476348.2020.1683448

Keywords: Influenza A; Pandemic Preparedness.