Cluster of Oseltamivir-Resistant and Hemagglutinin Antigenically Drifted Influenza A(H1N1)pdm09 Viruses, Texas, USA, January 2020

Anti-Influenza Virus Activity of Citrullus lanatus var. citroides as a Functional Food: A Review

Influenza is an acute respiratory illness caused by the influenza virus, in response to which vaccines and antiviral drugs are administered. In recent years, the antiviral effects of plants and foods have garnered attention. This review is the first to summarize the therapeutic properties of wild watermelon (Citrullus lanatus var. citroides) against influenza from a phytochemical viewpoint. Wild watermelon is a wild plant with significant potential as a therapeutic candidate in antiviral strategies, when focused on its multiple anti-influenza functionalities. Wild watermelon juice inhibits viral growth, entry, and replication. Hence, we highlight the possibility of utilizing wild watermelon for the prevention and treatment of influenza with stronger antiviral activity. Phytochemicals and phytoestrogen (polyphenol, flavonoids, and prenylated compounds) in wild watermelon juice contribute to this activity and inhibit various stages of viral replication, depending on the molecular structure. Wild plants and foods closely related to the original species contain many natural compounds such as phytochemicals, and exhibit various viral growth inhibitory effects. These natural products provide useful information for future antiviral strategies.

2019-2020 H1N1 clade A5a.1 viruses have better in vitro fitness compared with the co-circulating A5a.2 clade

Surveillance for emerging human influenza virus clades is important for identifying changes in viral fitness and assessing antigenic similarity to vaccine strains. While fitness and antigenic structure are both important aspects of virus success, they are distinct characteristics and do not always change in a complementary manner. The 2019-2020 Northern Hemisphere influenza season saw the emergence of two H1N1 clades: A5a.1 and A5a.2. While several studies indicated that A5a.2 showed similar or even increased antigenic drift compared with A5a.1, the A5a.1 clade was still the predominant circulating clade that season. Clinical isolates of representative viruses from these clades were collected in Baltimore, Maryland during the 2019-2020 season and multiple assays were performed to compare both antigenic drift and viral fitness between clades. Neutralization assays performed on serum from healthcare workers pre- and post-vaccination during the 2019-2020 season show a comparable drop in neutralizing titers against both A5a.1 and A5a.2 viruses compared with the vaccine strain, indicating that A5a.1 did not have antigenic advantages over A5a.2 that would explain its predominance in this population. Plaque assays were performed to investigate fitness differences, and the A5a.2 virus produced significantly smaller plaques compared with viruses from A5a.1 or the parental A5a clade. To assess viral replication, low MOI growth curves were performed on both MDCK-SIAT and primary differentiated human nasal epithelial cell cultures. In both cell cultures, A5a.2 yielded significantly reduced viral titers at multiple timepoints post-infection compared with A5a.1 or A5a. Receptor binding was then investigated through glycan array experiments which showed a reduction in receptor binding diversity for A5a.2, with fewer glycans bound and a higher percentage of total binding attributable to the top three highest bound glycans. Together these data indicate that the A5a.2 clade had a reduction in viral fitness, including reductions in receptor binding, that may have contributed to the limited prevalence observed after emergence.

2019-20 H1N1 clade A5a.1 viruses have better in vitro replication compared with the co-circulating A5a.2 clade

Surveillance for emerging human influenza virus clades is important for identifying changes in viral fitness and assessing antigenic similarity to vaccine strains. While fitness and antigenic structure are both important aspects of virus success, they are distinct characteristics and do not always change in a complementary manner. The 2019-20 Northern Hemisphere influenza season saw the emergence of two H1N1 clades: A5a.1 and A5a.2. While several studies indicated that A5a.2 showed similar or even increased antigenic drift compared with A5a.1, the A5a.1 clade was still the predominant circulating clade that season. Clinical isolates of representative viruses from these clades were collected in Baltimore, Maryland during the 2019-20 season and multiple assays were performed to compare both antigenic drift and viral fitness between clades. Neutralization assays performed on serum from healthcare workers pre- and post-vaccination during the 2019-20 season show a comparable drop in neutralizing titers against both A5a.1 and A5a.2 viruses compared with the vaccine strain, indicating that A5a.1 did not have antigenic advantages over A5a.2 that would explain its predominance in this population. Plaque assays were performed to investigate fitness differences, and the A5a.2 virus produced significantly smaller plaques compared with viruses from A5a.1 or the parental A5a clade. To assess viral replication, low MOI growth curves were performed on both MDCK-SIAT and primary differentiated human nasal epithelial cell cultures. In both cell cultures, A5a.2 yielded significantly reduced viral titers at multiple timepoints post-infection compared with A5a.1 or A5a. Receptor binding was then investigated through glycan array experiments which showed a reduction in receptor binding diversity for A5a.2, with fewer glycans bound and a higher percentage of total binding attributable to the top three highest bound glycans. Together these data indicate that the A5a.2 clade had a reduction in viral fitness, including reductions in receptor binding, that may have contributed to the limited prevalence observed after emergence.

An optimized cell-based assay to assess influenza virus replication by measuring neuraminidase activity and its applications for virological surveillance

Year-round virological characterization of circulating epidemic influenza viruses is conducted worldwide to detect the emergence of viruses that may escape pre-existing immunity or acquire resistance to antivirals. High throughput phenotypic assays are needed to complement the sequence-based analysis of circulating viruses and improve pandemic preparedness. The recent entry of a polymerase inhibitor, baloxavir, into the global market further highlighted this need. Here, we optimized a cell-based assay that considerably streamlines antiviral and antigenic testing by replacing lengthy immunostaining and imaging procedures used in current assay with measuring the enzymatic activity of nascent neuraminidase (NA) molecules expressed on the surface of virus-infected cells. For convenience, this new assay was named IRINA (Influenza Replication Inhibition Neuraminidase-based Assay). IRINA was successfully validated to assess inhibitory activity of baloxavir on virus replication by testing a large set (>150) of influenza A and B viruses, including drug resistant strains and viruses collected during 2017-2022. To test its versatility, IRINA was utilized to evaluate neutralization activity of a broadly reactive human anti-HA monoclonal antibody, FI6, and post-infection ferret antisera, as well as the inhibition of NA enzyme activity by NA inhibitors. Performance of IRINA was tested in parallel using respective conventional assays. IRINA offers an attractive alternative to current phenotypic assays, while maintaining reproducibility and high throughput capacity. Additionally, the improved turnaround time may prove to be advantageous when conducting time sensitive studies, such as investigating a new virus outbreak. This assay can meet the needs of surveillance laboratories by providing a streamlined and cost-effective approach for virus characterization.

In Vitro Anti-Influenza A Virus H1N1 Effect of Sesquiterpene-Rich Extracts of Carpesium abrotanoides

Due to a high content of sesquiterpenes, Carpesium abrotanoides has been investigated to fully explore its health-promoting properties. Therefore, this work aimed to assess, for the first time, the anti-influenza A virus H1N1 potential of sesquiterpene-targeted fractions of the herb derived from C. abrotanoides. Five compounds, including four sesquiterpenes and one aldehyde, were isolated and identified from the sesquiterpene-rich extracts of C. abrotanoides (SECA), and the contents of three main sesquiterpenes in the SECA were determined. Furthermore, SECA showed a significant protective effect in the MDCK cells infected with influenza A virus (H1N1) in three different conditions: premixed administration, prophylactic administration, and therapeutic administration. SECA can significantly decrease the mRNA expressions of TLR4, MyD88, NF-κB, TNF-α, and IL-6, as well as the protein expressions of TLR4, MyD88, and NF-κB. This result suggests that SECA can resist the influenza A virus H1N1 through the TLR4/MyD88/NF-κB signal pathway.

Assessing the fitness of a dual-antiviral drug resistant human influenza virus in the ferret model

Influenza antivirals are important tools in our fight against annual influenza epidemics and future influenza pandemics. Combinations of antivirals may reduce the likelihood of drug resistance and improve clinical outcomes. Previously, two hospitalised immunocompromised influenza patients, who received a combination of a neuraminidase inhibitor and baloxavir marboxil, shed influenza viruses resistant to both drugs. Here-in, the replicative fitness of one of these A(H1N1)pdm09 virus isolates with dual resistance mutations (NA-H275Y and PA-I38T) was similar to wild type virus (WT) in vitro, but reduced in the upper respiratory tracts of challenged ferrets. The dual-mutant virus transmitted well between ferrets in an airborne transmission model, but was outcompeted by the WT when the two viruses were co-administered. These results indicate the dual-mutant virus had a moderate loss of viral fitness compared to the WT virus, suggesting that while person-to-person transmission of the dual-resistant virus may be possible, widespread community transmission is unlikely.

Qingfei Jiedu Granules fight influenza by regulating inflammation, immunity, metabolism, and gut microbiota

Background and aim

Qingfei Jiedu Granules (QFJD) are a new Traditional Chinese Medicine (TCM) which has been clinically used against coronavirus pneumonia in China. In this study, the therapeutic effect and the underlying mechanisms of QFJD against influenza were investigated.

Experimental procedure

Pneumonia mice were induced by influenza A virus. Survival rate, weight loss, lung index and lung pathology were measured to evaluate the therapeutic effect of QFJD. The expression of inflammatory factors and lymphocytes was used to assess anti-inflammatory and immunomodulatory effect of QFJD. Gut microbiome analysis was performed to decipher the potential effect of QFJD on intestinal microbiota. Metabolomics approach was conducted to explore the overall metabolic regulation of QFJD.

Result and conclusion

QFJD shows a significant therapeutic effect on the treatment of influenza and the expression of many pro-inflammatory cytokines were obviously inhibited. QFJD also markedly modulates the level of T and B lymphocytes. The high-dose QFJD has shown similar therapeutic efficiency compared to positive drugs. QFJD profoundly enriched Verrucomicrobia and maintained the balance between Bacteroides and Firmicutes. QFJD associated with 12 signaling pathways in metabolomics study, 9 of which were the same as the model group and were closely related to citrate cycle and amino acid metabolism.To sum up, QFJD is a novel and promising drug against influenza. It can regulate inflammation, immunity, metabolism, and gut microbiota to fight influenza. Verrucomicrobia shows great potential to improve influenza infection and may be an important target.

Assessment of influenza A (H1N1, H3N2) oseltamivir resistance during 2017-2019 in Iran

Background and Objectives

Neuraminidase inhibitors (NAIs) as an imperative antiviral for influenza prophylaxis and treatment are being consumed worldwide. Increasing use of these antivirals might be associated with drug resistance. Regarding the significance of these variations, this study aimed to investigate the mutations occurring in the NA gene of influenza A viruses leading to oseltamivir resistance during 2017-2019 in Iran.

Materials and Methods

In this cross-sectional study, 40 influenza A (H1N1, H3N2) strains, isolated in National Influenza Center (NIC) from patients with Severe Acute Respiratory Infection (SARI) during 2017-2019 were subjected to RT-PCR and sequencing of NA complete gene. The frequency of oseltamivir resistance and variation of NA amino acids in these strains were investigated.

Results

No significant mutation conferring oseltamivir resistance was detected. However, NA antigenic sites in these strains depicted minor changes compared to the vaccine strains. Among H3N2 isolates, mutations at 329, 344, 346 and 385 and among H1N1 isolates mutations at 143 and 188 residues occurred in NA antigenic regions.

Conclusion

Evaluation of NA gene sequences, showed no resistant viruses to oseltamivir. Given that the viruses in the present study were the last viruses circulating in Iran before COVID-19 pandemic, the results will be beneficial to have a worthy comparison with the strains circulating after the pandemic. Constant monitoring for the emergence of drug-resistant variants and antigenic changes are crucial for all countries.

Global update on the susceptibilities of human influenza viruses to neuraminidase inhibitors and the cap-dependent endonuclease inhibitor baloxavir, 2018–2020

Global analysis of the susceptibility of influenza viruses to neuraminidase (NA) inhibitors (NAIs) and the polymerase acidic (PA) inhibitor (PAI) baloxavir was conducted by five World Health Organization Collaborating Centres for Reference and Research on Influenza during two periods (May 2018–May 2019 and May 2019–May 2020). Combined phenotypic and NA sequence-based analysis revealed that the global frequency of viruses displaying reduced or highly reduced inhibition (RI or HRI) or potential to show RI/HRI by NAIs remained low, 0.5% (165/35045) and 0.6% (159/26010) for the 2018–2019 and 2019–2020 periods, respectively. The most common amino acid substitution was NA-H275Y (N1 numbering) conferring HRI by oseltamivir and peramivir in A(H1N1)pdm09 viruses. Combined phenotypic and PA sequence-based analysis showed that the global frequency of viruses showing reduced susceptibility to baloxavir or carrying substitutions associated with reduced susceptibility was low, 0.5% (72/15906) and 0.1% (18/15692) for the 2018–2019 and 2019–2020 periods, respectively. Most (n = 61) of these viruses had I38→T/F/M/S/L/V PA amino acid substitutions. In Japan, where baloxavir use was highest, the rate was 4.5% (41/919) in the 2018–2019 period and most of the viruses (n = 32) had PA-I38T. Zoonotic viruses isolated from humans (n = 32) in different countries did not contain substitutions in NA associated with NAI RI/HRI phenotypes. One A(H5N6) virus had a dual substitution PA-I38V + PA-E199G, which may reduce susceptibility to baloxavir. Therefore, NAIs and baloxavir remain appropriate choices for the treatment of influenza virus infections, but close monitoring of antiviral susceptibility is warranted.