Mechanisms of the action of povidone-iodine against human and avian influenza A viruses: its effects on hemagglutination and sialidase activities

<p>Abstract</p> <p>Background</p> <p>Influenza virus infection causes significant morbidity and mortality and has marked social and economic impacts throughout the world. The influenza surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA), act cooperatively to support efficient influenza A virus replication and provide the most important targets for anti-influenza chemotherapy. In this study, povidone-iodine (PVP-I), which has a broad-spectrum microbicidal property, was examined for its inhibitory effects against influenza virus infection in MDCK cells and the mechanisms of PVP-I action on HA and NA were revealed.</p> <p>Results</p> <p>Results obtained using a novel fluorescence- and chromogenic-based plaque inhibition assay showed that 1.56 mg/ml PVP-I inhibited infections in MDCK cells of human (8 strains) and avian (5 strains) influenza A viruses, including H1N1, H3N2, H5N3 and H9N2, from 23.0–97.5%. A sialidase inhibition assay revealed that PVP-I inhibited N1, N2 and N3 neuraminidases with IC₅₀values of 9.5–212.1 μg/ml by a mixed-type inhibition mechanism. Receptor binding inhibition and hemagglutinin inhibition assays indicated that PVP-I affected viral hemagglutinin rather than host-specific sialic acid receptors.</p> <p>Conclusion</p> <p>Mechanisms of reduction of viral growth in MDCK cells by PVP-I involve blockade of viral attachment to cellular receptors and inhibition of viral release and spread from infected cells. Therefore, PVP-I is useful to prevent infection and limit spread of human and avian influenza viruses.</p

Host Receptors of Influenza Viruses and Coronaviruses—Molecular Mechanisms of Recognition

Among the four genera of influenza viruses (IVs) and the four genera of coronaviruses (CoVs), zoonotic &alpha;IV and &beta;CoV have occasionally caused airborne epidemic outbreaks in humans, who are immunologically na&iuml;ve, and the outbreaks have resulted in high fatality rates as well as social and economic disruption and losses. The most devasting influenza A virus (IAV) in &alpha;IV, pandemic H1N1 in 1918, which caused at least 40 million deaths from about 500 million cases of infection, was the first recorded emergence of IAVs in humans. Usually, a novel human-adapted virus replaces the preexisting human-adapted virus. Interestingly, two IAV subtypes, A/H3N2/1968 and A/H1N1/2009 variants, and two lineages of influenza B viruses (IBV) in &beta;IV, B/Yamagata and B/Victoria lineage-like viruses, remain seasonally detectable in humans. Both influenza C viruses (ICVs) in &gamma;IV and four human CoVs, HCoV-229E and HCoV-NL63 in &alpha;CoV and HCoV-OC43 and HCoV-HKU1 in &beta;CoV, usually cause mild respiratory infections. Much attention has been given to CoVs since the global epidemic outbreaks of &beta;SARS-CoV in 2002&ndash;2004 and &beta;MERS-CoV from 2012 to present. &beta;SARS-CoV-2, which is causing the ongoing COVID-19 pandemic that has resulted in 890,392 deaths from about 27 million cases of infection as of 8 September 2020, has provoked worldwide investigations of CoVs. With the aim of developing efficient strategies for controlling virus outbreaks and recurrences of seasonal virus variants, here we overview the structures, diversities, host ranges and host receptors of all IVs and CoVs and critically review current knowledge of receptor binding specificity of spike glycoproteins, which mediates infection, of IVs and of zoonotic, pandemic and seasonal CoVs

Simple and Inexpensive Fluorescence-Based Technique for High-Throughput Antimalarial Drug Screening

Radioisotopic assays involve expense, multistep protocols, equipment, and radioactivity safety requirements which are problematic in high-throughput drug testing. This study reports an alternative, simple, robust, inexpensive, one-step fluorescence assay for use in antimalarial drug screening. Parasite growth is determined by using SYBR Green I, a dye with marked fluorescence enhancement upon contact with Plasmodium DNA. A side-by-side comparison of this fluorescence assay and a standard radioisotopic method was performed by testing known antimalarial agents against Plasmodium falciparum strain D6. Both assay methods were used to determine the effective concentration of drug that resulted in a 50% reduction in the observed counts (EC(50)) after 48 h of parasite growth in the presence of each drug. The EC(50)s of chloroquine, quinine, mefloquine, artemisinin, and 3,6-bis-ɛ-(N,N-diethylamino)-amyloxyxanthone were similar or identical by both techniques. The results obtained with this new fluorescence assay suggest that it may be an ideal method for high-throughput antimalarial drug screening

N-glycans from porcine trachea and lung: predominant NeuAcα2-6Gal could be a selective pressure for influenza variants in favor of human-type receptor.

It is known that pigs acted as "mixing vessels" for genesis of a new reassortant influenza strain responsible for pandemic H1N1 2009. However, the host factors driving the evolution of a reassorted virus in pigs to 'jump species' resulting in a human outbreak remain unclear. N-glycans derived from the porcine respiratory tract were enzymatically released, fluorescent labeled with 2-aminopyridine, separated according to charge, size and hydrophobicity, and structurally identified by a two-dimensional (size and hydrophobicity) HPLC mapping technique and MALDI-TOF mass spectrometry before and after exo-glycosidase digestion. We found a 3-, 5-, and 13-fold increases in NeuAcα2-6, a preferable human influenza receptor, over NeuAcα2-3, an avian influenza receptor, from upper and lower parts of the porcine trachea towards the porcine lung, a major target organ for swine virus replication. The large proportion of NeuAcα2-6 may exert selective pressure for selection of influenza variants with altered receptor preference for this human-type α2-6 receptor, a crucial first step for generating a human pandemic

Structures and relative quantities of neutral, mono- and di-sialyl PA-oligosaccharides derived from the porcine upper trachea, lower trachea and lungs of a pig.

<p>a, mol % was calculated from the peak area in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016302#pone-0016302-g003" target="_blank">Figure 3</a> by comparison with total <i>N</i>-glycan content in each porcine tissue. b, Structures of PA-oligosaccharides are represented by symbols as follows: red diamond, NeuAcα2-6; purple diamond, NeuAcα2-3; green diamond, NeuGcα2-6; light blue diamond, NeuGcα2-3; yellow circle with α, α-galactose(Gal); yellow circle, galactose; blue square, N-acetylglucosamine (GlcNAc); green circle, mannose (Man), red triangle, fucose (Fuc). c, Units of glucose (GU) were calculated from the elution times of the peaks obtained from the ODS column in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0016302#pone-0016302-g003" target="_blank">Figure 3</a>.</p

Anion exchange DEAE elution profiles of PA-glycans derived from the porcine trachea (upper and lower) and lungs.

<p>The PA-glycans were fractionated according to their sialic acid content as neutral, mono-, and di-sialyl oligosaccharide fractions as indicated.</p

A predominant quantity of Siaα2-6Gal receptor on <i>N</i>-glycans in the trachea (upper and lower) and lungs of a pig.

<p>A predominant quantity of Siaα2-6Gal receptor on <i>N</i>-glycans in the trachea (upper and lower) and lungs of a pig.</p