Matrix Protein 2 Extracellular Domain-Specific Monoclonal Antibodies Are an Effective and Potentially Universal Treatment for Influenza A

Influenza virus infection causes significant morbidity and mortality worldwide. Humans fail to make a universally protective memory immune response to influenza A. Hemagglutinin and Neuraminidase undergo antigenic drift and shift, resulting in new influenza A strains to which humans are naive. Seasonal vaccines are often ineffective and escape mutants have been reported to all treatments for influenza A. In the absence of a universal influenza A vaccine or treatment, influenza A will remain a significant threat to human health. The extracellular domain of the M2-ion channel (M2e) is an ideal antigenic target for a universal therapeutic agent, as it is highly conserved across influenza A serotypes, has a low mutation rate, and is essential for viral entry and replication. Previous M2e-specific monoclonal antibodies (M2e-MAbs) show protective potential against influenza A, however, they are either strain specific or have limited efficacy. We generated seven murine M2e-MAbs and utilized in vitro and in vivo assays to validate the specificity of our novel M2e-MAbs and to explore the universality of their protective potential. Our data shows our M2e-MAbs bind to M2e peptide, HEK cells expressing the M2 channel, as well as, influenza virions and MDCK-ATL cells infected with influenza viruses of multiple serotypes. Our antibodies significantly protect highly influenza A virus susceptible BALB/c mice from lethal challenge with H1N1 A/PR/8/34, pH1N1 A/CA/07/2009, H5N1 A/Vietnam/1203/2004, and H7N9 A/Anhui/1/2013 by improving survival rates and weight loss. Based on these results, at least four of our seven M2e-MAbs show strong potential as universal influenza A treatments. IMPORTANCE Despite a seasonal vaccine and multiple therapeutic treatments, Influenza A remains a significant threat to human health. The biggest obstacle is producing a vaccine or treatment for influenza A is their universality or efficacy against not only seasonal variances in the influenza virus, but also against all human, avian, and swine serotypes and, therefore, potential pandemic strains. M2e has huge potential as a target for a vaccine or treatment against influenza A. It is the most conserved external protein on the virus. Antibodies against M2e have made it to clinical trials, but not succeeded. Here, we describe novel M2e antibodies produced in mice that are not only protective at low doses, but that we extensively test to determine their universality and found to be cross protective against all strains tested. Additionally, our work begins to elucidate the critical role of isotype for an influenza A monoclonal antibody therapeutic.

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Divergent Human-Origin Influenza Viruses Detected in Australian Swine Populations

Journal of Virology ◽

10.1128/jvi.00316-18 ◽

2018 ◽

Vol 92 (16) ◽

Cited By ~ 6

Author(s):

Frank Y. K. Wong ◽

Celeste Donato ◽

Yi-Mo Deng ◽

Don Teng ◽

Naomi Komadina ◽

...

Keyword(s):

Influenza Virus ◽

Influenza A ◽

Swine Influenza ◽

Influenza Viruses ◽

Antigenic Drift ◽

Human Origin ◽

Human Influenza ◽

Influenza A Viruses ◽

Data Set ◽

Antigenic Properties

ABSTRACTGlobal swine populations infected with influenza A viruses pose a persistent pandemic risk. With the exception of a few countries, our understanding of the genetic diversity of swine influenza viruses is limited, hampering control measures and pandemic risk assessment. Here we report the genomic characteristics and evolutionary history of influenza A viruses isolated in Australia from 2012 to 2016 from two geographically isolated swine populations in the states of Queensland and Western Australia. Phylogenetic analysis with an expansive human and swine influenza virus data set comprising >40,000 sequences sampled globally revealed evidence of the pervasive introduction and long-term establishment of gene segments derived from several human influenza viruses of past seasons, including the H1N1/1977, H1N1/1995, H3N2/1968, and H3N2/2003, and the H1N1 2009 pandemic (H1N1pdm09) influenza A viruses, and a genotype that contained gene segments derived from the past three pandemics (1968, reemerged 1977, and 2009). Of the six human-derived gene lineages, only one, comprising two viruses isolated in Queensland during 2012, was closely related to swine viruses detected from other regions, indicating a previously undetected circulation of Australian swine lineages for approximately 3 to 44 years. Although the date of introduction of these lineages into Australian swine populations could not be accurately ascertained, we found evidence of sustained transmission of two lineages in swine from 2012 to 2016. The continued detection of human-origin influenza virus lineages in swine over several decades with little or unpredictable antigenic drift indicates that isolated swine populations can act as antigenic archives of human influenza viruses, raising the risk of reemergence in humans when sufficient susceptible populations arise.IMPORTANCEWe describe the evolutionary origins and antigenic properties of influenza A viruses isolated from two separate Australian swine populations from 2012 to 2016, showing that these viruses are distinct from each other and from those isolated from swine globally. Whole-genome sequencing of virus isolates revealed a high genotypic diversity that had been generated exclusively through the introduction and establishment of human influenza viruses that circulated in past seasons. We detected six reassortants with gene segments derived from human H1N1/H1N1pdm09 and various human H3N2 viruses that circulated during various periods since 1968. We also found that these swine viruses were not related to swine viruses collected elsewhere, indicating independent circulation. The detection of unique lineages and genotypes in Australia suggests that isolated swine populations that are sufficiently large can sustain influenza virus for extensive periods; we show direct evidence of a sustained transmission for at least 4 years between 2012 and 2016.

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RNA-Sequencing-Based Transcriptomic Analysis Reveals a Role for Annexin-A1 in Classical and Influenza A Virus-Induced Autophagy

Cells ◽

10.3390/cells9061399 ◽

2020 ◽

Vol 9 (6) ◽

pp. 1399 ◽

Cited By ~ 1

Author(s):

Jianzhou Cui ◽

Dhakshayini Morgan ◽

Dao Han Cheng ◽

Sok Lin Foo ◽

Gracemary L. R. Yap ◽

...

Keyword(s):

Influenza Virus ◽

Influenza A Virus ◽

Influenza A ◽

Influenza Infection ◽

Critical Role ◽

Mtor Inhibitors ◽

Influenza Viruses ◽

Annexin A1 ◽

Underlying Mechanisms

Influenza viruses have been shown to use autophagy for their survival. However, the proteins and mechanisms involved in the autophagic process triggered by the influenza virus are unclear. Annexin-A1 (ANXA1) is an immunomodulatory protein involved in the regulation of the immune response and Influenza A virus (IAV) replication. In this study, using clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 (CRISPR associated protein 9) deletion of ANXA1, combined with the next-generation sequencing, we systematically analyzed the critical role of ANXA1 in IAV infection as well as the detailed processes governing IAV infection, such as macroautophagy. A number of differentially expressed genes were uniquely expressed in influenza A virus-infected A549 parental cells and A549 ∆ANXA1 cells, which were enriched in the immune system and infection-related pathways. Gene ontology and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway revealed the role of ANXA1 in autophagy. To validate this, the effect of mechanistic target of rapamycin (mTOR) inhibitors, starvation and influenza infection on autophagy was determined, and our results demonstrate that ANXA1 enhances autophagy induced by conventional autophagy inducers and influenza virus. These results will help us to understand the underlying mechanisms of IAV infection and provide a potential therapeutic target for restricting influenza viral replication and infection.

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Enhanced Influenza Virus-Like Particle Vaccines Containing the Extracellular Domain of Matrix Protein 2 and a Toll-Like Receptor Ligand

Clinical and Vaccine Immunology ◽

10.1128/cvi.00153-12 ◽

2012 ◽

Vol 19 (8) ◽

pp. 1119-1125 ◽

Cited By ~ 37

Author(s):

Bao-Zhong Wang ◽

Harvinder S. Gill ◽

Sang-Moo Kang ◽

Li Wang ◽

Ying-Chun Wang ◽

...

Keyword(s):

Influenza Virus ◽

Fusion Protein ◽

Influenza A ◽

Matrix Protein ◽

Protective Efficacy ◽

Extracellular Domain ◽

Toll Like Receptor ◽

Influenza A Viruses ◽

Live Virus ◽

Content Type

ABSTRACTThe extracellular domain of matrix protein 2 (M2e) is conserved among influenza A viruses. The goal of this project is to develop enhanced influenza vaccines with broad protective efficacy using the M2e antigen. We designed a membrane-anchored fusion protein by replacing the hyperimmunogenic region ofSalmonella entericaserovar Typhimurium flagellin (FliC) with four repeats of M2e (4.M2e-tFliC) and fusing it to a membrane anchor from influenza virus hemagglutinin (HA). The fusion protein was incorporated into influenza virus M1-based virus-like particles (VLPs). These VLPs retained Toll-like receptor 5 (TLR5) agonist activity comparable to that of soluble FliC. Mice immunized with the VLPs by either intramuscular or intranasal immunization showed high levels of systemic M2-specific antibody responses compared to the responses to soluble 4.M2e protein. High mucosal antibody titers were also induced in intranasally immunized mice. All intranasally immunized mice survived lethal challenges with live virus, while intramuscularly immunized mice showed only partial protection, revealing better protection by the intranasal route. These results indicate that a combination of M2e antigens and TLR ligand adjuvants in VLPs has potential for development of a broadly protective influenza A virus vaccine.

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Broadly Neutralizing Anti-Influenza Virus Antibodies: Enhancement of Neutralizing Potency in Polyclonal Mixtures and IgA Backbones

Journal of Virology ◽

10.1128/jvi.03099-14 ◽

2015 ◽

Vol 89 (7) ◽

pp. 3610-3618 ◽

Cited By ~ 50

Author(s):

Wenqian He ◽

Caitlin E. Mullarkey ◽

J. Andrew Duty ◽

Thomas M. Moran ◽

Peter Palese ◽

...

Keyword(s):

Influenza Virus ◽

Monoclonal Antibodies ◽

Virus Vaccine ◽

Neutralizing Antibodies ◽

Influenza A ◽

Human Peripheral Blood ◽

Influenza Virus Vaccine ◽

Influenza Viruses ◽

Broadly Neutralizing Antibodies ◽

Variable Regions

ABSTRACTCurrent influenza virus vaccines rely upon the accurate prediction of circulating virus strains months in advance of the actual influenza season in order to allow time for vaccine manufacture. Unfortunately, mismatches occur frequently, and even when perfect matches are achieved, suboptimal vaccine efficacy leaves several high-risk populations vulnerable to infection. However, the recent discovery of broadly neutralizing antibodies that target the hemagglutinin (HA) stalk domain has renewed hope that the development of “universal” influenza virus vaccines may be within reach. Here, we examine the functions of influenza A virus hemagglutinin stalk-binding antibodies in an endogenous setting, i.e., as polyclonal preparations isolated from human sera. Relative to monoclonal antibodies that bind to the HA head domain, the neutralization potency of monoclonal stalk-binding antibodies was vastly inferiorin vitrobut was enhanced by several orders of magnitude in the polyclonal context. Furthermore, we demonstrated a surprising enhancement in IgA-mediated HA stalk neutralization relative to that achieved by antibodies of IgG isotypes. Mechanistically, this could be explained in two ways. Identical variable regions consistently neutralized virus more potently when in an IgA backbone compared to an IgG backbone. In addition, HA-specific memory B cells isolated from human peripheral blood were more likely to be stalk specific when secreting antibodies of IgA isotypes compared to those secreting IgG. Taken together, our data provide strong evidence that HA stalk-binding antibodies perform optimally when in a polyclonal context and that the targeted elicitation of HA stalk-specific IgA should be an important consideration during “universal” influenza virus vaccine design.IMPORTANCEInfluenza viruses remain one of the most worrisome global public health threats due to their capacity to cause pandemics. While seasonal vaccines fail to protect against the emergence of pandemic strains, a new class of broadly neutralizing antibodies has been recently discovered and may be the key to developing a “universal” influenza virus vaccine. While much has been learned about the biology of these antibodies, most studies have focused only on monoclonal antibodies of IgG subtypes. However, the study of monoclonal antibodies often fails to capture the complexity of antibody functions that occur during natural polyclonal responses. Here, we provide the first detailed analyses of the biological activity of these antibodies in polyclonal contexts, comparing both IgG and IgA isotypes isolated from human donors. The striking differences observed in the functional properties of broadly neutralizing antibodies in polyclonal contexts will be essential for guiding design of “universal” influenza virus vaccines and therapeutics.

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Influenza A Virus Vaccination: Immunity, Protection, and Recent Advances Toward A Universal Vaccine

Vaccines ◽

10.3390/vaccines8030434 ◽

2020 ◽

Vol 8 (3) ◽

pp. 434 ◽

Cited By ~ 2

Author(s):

Christopher E. Lopez ◽

Kevin L. Legge

Keyword(s):

Immune Response ◽

Influenza Virus ◽

Virus Infection ◽

Influenza A ◽

Influenza Virus Infection ◽

Influenza Viruses ◽

Antigenic Drift ◽

Influenza Vaccines ◽

Virus Infections ◽

Universal Vaccine

Influenza virus infections represent a serious public health threat and account for significant morbidity and mortality worldwide due to seasonal epidemics and periodic pandemics. Despite being an important countermeasure to combat influenza virus and being highly efficacious when matched to circulating influenza viruses, current preventative strategies of vaccination against influenza virus often provide incomplete protection due the continuous antigenic drift/shift of circulating strains of influenza virus. Prevention and control of influenza virus infection with vaccines is dependent on the host immune response induced by vaccination and the various vaccine platforms induce different components of the local and systemic immune response. This review focuses on the immune basis of current (inactivated influenza vaccines (IIV) and live attenuated influenza vaccines (LAIV)) as well as novel vaccine platforms against influenza virus. Particular emphasis will be placed on how each platform induces cross-protection against heterologous influenza viruses, as well as how this immunity compares to and contrasts from the “gold standard” of immunity generated by natural influenza virus infection.

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Novel Ranking System for Identifying Efficacious Anti-Influenza Virus PB2 Inhibitors

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00781-15 ◽

2015 ◽

Vol 59 (10) ◽

pp. 6007-6016 ◽

Cited By ~ 8

Author(s):

Alice W. Tsai ◽

Colleen F. McNeil ◽

Joshua R. Leeman ◽

Hamilton B. Bennett ◽

Kwame Nti-Addae ◽

...

Keyword(s):

Influenza Virus ◽

Influenza A Virus ◽

Influenza A ◽

Therapeutic Agents ◽

Influenza Viruses ◽

Antigenic Drift ◽

Whole Body ◽

Infection Model ◽

Virus Infections

ABSTRACTThrough antigenic drift and shifts, influenza virus infections continue to be an annual cause of morbidity in healthy populations and of death among elderly and at-risk patients. The emergence of highly pathogenic avian influenza viruses such as H5N1 and H7N9 and the rapid spread of the swine-origin H1N1 influenza virus in 2009 demonstrate the continued need for effective therapeutic agents for influenza. While several neuraminidase inhibitors have been developed for the treatment of influenza virus infections, these have shown a limited window for treatment initiation, and resistant variants have been noted in the population. In addition, an older class of antiviral drugs for influenza, the adamantanes, are no longer recommended for treatment due to widespread resistance. There remains a need for new influenza therapeutic agents with improved efficacy as well as an expanded window for the initiation of treatment. Azaindole compounds targeting the influenza A virus PB2 protein and demonstrating excellentin vitroandin vivoproperties have been identified. To evaluate thein vivoefficacy of these PB2 inhibitors, we utilized a mouse influenza A virus infection model. In addition to traditional endpoints, i.e., death, morbidity, and body weight loss, we measured lung function using whole-body plethysmography, and we used these data to develop a composite efficacy score that takes compound exposure into account. This model allowed the rapid identification and ranking of molecules relative to each other and to oseltamivir. The ability to identify compounds with enhanced preclinical properties provides an opportunity to develop more-effective treatments for influenza in patients.

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Increased Protein Degradation Improves Influenza Virus Nucleoprotein-Specific CD8+T Cell ActivationIn Vitrobut Not in C57BL/6 Mice

Journal of Virology ◽

10.1128/jvi.01633-16 ◽

2016 ◽

Vol 90 (22) ◽

pp. 10209-10219 ◽

Cited By ~ 5

Author(s):

Arwen F. Altenburg ◽

Carolien E. van de Sandt ◽

Stella E. van Trierum ◽

Heidi L. M. De Gruyter ◽

Peter R. W. A. van Run ◽

...

Keyword(s):

T Cells ◽

Influenza Virus ◽

T Cell ◽

Influenza A ◽

T Cell Responses ◽

Influenza Viruses ◽

Antigenic Drift ◽

Influenza Vaccines ◽

Cell Responses ◽

Modified Vaccinia Virus Ankara

ABSTRACTDue to antigenic drift of influenza viruses, seasonal influenza vaccines need to be updated annually. These vaccines are based on predictions of strains likely to circulate in the next season. However, vaccine efficacy is greatly reduced in the case of a mismatch between circulating and vaccine strains. Furthermore, novel antigenically distinct influenza viruses are introduced into the human population from animal reservoirs occasionally and may cause pandemic outbreaks. To dampen the impact of seasonal and pandemic influenza, vaccines that induce broadly protective and long-lasting immunity are preferred. Because influenza virus-specific CD8+T cells are directed mainly against relatively conserved internal proteins, like nucleoprotein (NP), they are highly cross-reactive and afford protection against infection with antigenically distinct influenza virus strains, so-called heterosubtypic immunity. Here, we used modified vaccinia virus Ankara (MVA) as a vaccine vector for the induction of influenza virus NP-specific CD8+T cells. To optimize the induction of CD8+T cell responses, we made several modifications to NP, aiming at retaining the protein in the cytosol or targeting it to the proteasome. We hypothesized that these strategies would increase antigen processing and presentation and thus improve the induction of CD8+T cell responses. We showed that NP with increased degradation rates improved CD8+T cell activationin vitroif the amount of antigen was limited or if CD8+T cells were of low functional avidity. However, after immunization of C57BL/6 mice, no differences were detected between modified NP and wild-type NP (NPwt), since NPwt already induced optimal CD8+T cell responses.IMPORTANCEDue to the continuous antigenic drift of seasonal influenza viruses and the threat of a novel pandemic, there is a great need for the development of novel influenza vaccines that offer broadly protective immunity against multiple subtypes. CD8+T cells can provide immunity against multiple subtypes of influenza viruses by the recognition of relatively conserved internal antigens. In this study, we aimed at optimizing the CD8+T cell response to influenza A virus by making modifications to influenza A virus nucleoprotein (NP) expressed from the modified vaccinia virus Ankara (MVA) vaccine vector. These modifications resulted in increased antigen degradation, thereby producing elevated levels of peptides that can be presented on major histocompatibility complex (MHC) class I molecules to CD8+T cells. Although we were unable to increase the NP-specific immune response in the mouse strain used, this approach may have benefits for vaccine development using less-immunogenic proteins.

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Preparing intensive care for the next pandemic influenza

Critical Care ◽

10.1186/s13054-019-2616-1 ◽

2019 ◽

Vol 23 (1) ◽

Cited By ~ 33

Author(s):

Taylor Kain ◽

Robert Fowler

Keyword(s):

Resource Allocation ◽

Influenza Virus ◽

Intensive Care ◽

Pandemic Influenza ◽

Influenza A ◽

Large Scale ◽

Influenza Pandemic ◽

Influenza Viruses ◽

Antigenic Drift ◽

Timely Initiation

Abstract Few viruses have shaped the course of human history more than influenza viruses. A century since the 1918–1919 Spanish influenza pandemic—the largest and deadliest influenza pandemic in recorded history—we have learned much about pandemic influenza and the origins of antigenic drift among influenza A viruses. Despite this knowledge, we remain largely underprepared for when the next major pandemic occurs. While emergency departments are likely to care for the first cases of pandemic influenza, intensive care units (ICUs) will certainly see the sickest and will likely have the most complex issues regarding resource allocation. Intensivists must therefore be prepared for the next pandemic influenza virus. Preparation requires multiple steps, including careful surveillance for new pandemics, a scalable response system to respond to surge capacity, vaccine production mechanisms, coordinated communication strategies, and stream-lined research plans for timely initiation during a pandemic. Conservative models of a large-scale influenza pandemic predict more than 170% utilization of ICU-level resources. When faced with pandemic influenza, ICUs must have a strategy for resource allocation as strain increases on the system. There are several current threats, including avian influenza A(H5N1) and A(H7N9) viruses. As humans continue to live in closer proximity to each other, travel more extensively, and interact with greater numbers of birds and livestock, the risk of emergence of the next pandemic influenza virus mounts. Now is the time to prepare and coordinate local, national, and global efforts.

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Protective porcine influenza virus-specific monoclonal antibodies recognize similar haemagglutinin epitopes as humans

PLoS Pathogens ◽

10.1371/journal.ppat.1009330 ◽

2021 ◽

Vol 17 (3) ◽

pp. e1009330

Author(s):

Barbara Holzer ◽

Pramila Rijal ◽

Adam McNee ◽

Basudev Paudyal ◽

Veronica Martini ◽

...

Keyword(s):

Monoclonal Antibodies ◽

Influenza A ◽

Virus Evolution ◽

Influenza Viruses ◽

Antigenic Drift ◽

Lung Pathology ◽

Influenza A Viruses ◽

Vaccine Recommendations ◽

Natural Hosts ◽

Zoonotic Strains

Pigs are natural hosts for the same subtypes of influenza A viruses as humans and integrally involved in virus evolution with frequent interspecies transmissions in both directions. The emergence of the 2009 pandemic H1N1 virus illustrates the importance of pigs in evolution of zoonotic strains. Here we generated pig influenza-specific monoclonal antibodies (mAbs) from H1N1pdm09 infected pigs. The mAbs recognized the same two major immunodominant haemagglutinin (HA) epitopes targeted by humans, one of which is not recognized by post-infection ferret antisera that are commonly used to monitor virus evolution. Neutralizing activity of the pig mAbs was comparable to that of potent human anti-HA mAbs. Further, prophylactic administration of a selected porcine mAb to pigs abolished lung viral load and greatly reduced lung pathology but did not eliminate nasal shedding of virus after H1N1pdm09 challenge. Hence mAbs from pigs, which target HA can significantly reduce disease severity. These results, together with the comparable sizes of pigs and humans, indicate that the pig is a valuable model for understanding how best to apply mAbs as therapy in humans and for monitoring antigenic drift of influenza viruses in humans, thereby providing information highly relevant to making influenza vaccine recommendations.

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Salinomycin Inhibits Influenza Virus Infection by Disrupting Endosomal Acidification and Viral Matrix Protein 2 Function

Journal of Virology ◽

10.1128/jvi.01441-18 ◽

2018 ◽

Vol 92 (24) ◽

Cited By ~ 12

Author(s):

Yejin Jang ◽

Jin Soo Shin ◽

Yi-Seul Yoon ◽

Yun Young Go ◽

Hye Won Lee ◽

...

Keyword(s):

Influenza Virus ◽

Influenza A ◽

Matrix Protein ◽

Influenza Virus Infection ◽

Influenza Viruses ◽

Proton Channel ◽

Therapeutic Effects ◽

Monovalent Ions ◽

Endosomal Acidification ◽

Oseltamivir Phosphate

ABSTRACT Screening of chemical libraries with 2,000 synthetic compounds identified salinomycin as a hit against influenza A and B viruses, with 50% effective concentrations ranging from 0.4 to 4.3 μM in cells. This compound is a carboxylic polyether ionophore that exchanges monovalent ions for protons across lipid bilayer membranes. Monitoring the time course of viral infection showed that salinomycin blocked nuclear migration of viral nuclear protein (NP), the most abundant component of the viral ribonucleoprotein (vRNP) complex. It caused cytoplasmic accumulation of NP, particularly within perinuclear endosomes, during virus entry. This was primarily associated with failure to acidify the endosomal-lysosomal compartments. Similar to the case with amantadine (AMT), proton channel activity of viral matrix protein 2 (M2) was blocked by salinomycin. Using purified retroviral Gag-based virus-like particles (VLPs) with M2, it was proved that salinomycin directly affects the kinetics of a proton influx into the particles but in a manner different from that of AMT. Notably, oral administration of salinomycin together with the neuraminidase inhibitor oseltamivir phosphate (OSV-P) led to enhanced antiviral effect over that with either compound used alone in influenza A virus-infected mouse models. These results provide a new paradigm for developing antivirals and their combination therapy that control both host and viral factors.IMPORTANCE Influenza virus is a main cause of viral respiratory infection in humans as well as animals, occasionally with high mortality. Circulation of influenza viruses resistant to the matrix protein 2 (M2) inhibitor, amantadine, is highly prevalent. Moreover, the frequency of detection of viruses resistant to the neuraminidase inhibitors, including oseltamivir phosphate (OSV-P) or zanamivir, is also increasing. These issues highlight the need for discovery of new antiviral agents with different mechanisms. Salinomycin as the monovalent cation-proton antiporter exhibited consistent inhibitory effects against influenza A and B viruses. It plays multifunctional roles by blocking endosomal acidification and by inactivating the proton transport function of M2, the key steps for influenza virus uncoating. Notably, salinomycin resulted in marked therapeutic effects in influenza virus-infected mice when combined with OSV-P, suggesting that its chemical derivatives could be developed as an adjuvant antiviral therapy to treat influenza infections resistant or less sensitive to existing drugs.

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