The effects of neuraminidase inhibitors on the release of oseltamivir-sensitive and oseltamivir-resistant influenza viruses from primary cultures of human tracheal epithelium

Anti-inflammatory effects of medications used for viral infection-induced respiratory diseases

Respiratory viruses like rhinovirus, influenza virus, respiratory syncytial virus, and coronavirus cause several respiratory diseases, such as bronchitis, pneumonia, pulmonary fibrosis, and coronavirus disease 2019, and exacerbate bronchial asthma, chronic obstructive pulmonary disease, bronchiectasis, and diffuse panbronchiolitis. The production of inflammatory mediators and mucin and the accumulation of inflammatory cells have been reported in patients with viral infection-induced respiratory diseases. Interleukin (IL)-1β, IL-6, IL-8, tumor necrosis factor-α, granulocyte-macrophage colony-stimulating factor, and regulated on activation normal T-cell expressed and secreted are produced in the cells, including human airway and alveolar epithelial cells, partly through the activation of toll-like receptors, nuclear factor kappa B and p44/42 mitogen-activated protein kinase. These mediators are associated with the development of viral infection-induced respiratory diseases through the induction of inflammation and injury in the airway and lung, airway remodeling and hyperresponsiveness, and mucus secretion. Medications used to treat respiratory diseases, including corticosteroids, long-acting β₂-agonists, long-acting muscarinic antagonists, mucolytic agents, antiviral drugs for severe acute respiratory syndrome coronavirus 2 and influenza virus, macrolides, and Kampo medicines, reduce the production of viral infection-induced mediators, including cytokines and mucin, as determined in clinical, in vivo, or in vitro studies. These results suggest that the anti-inflammatory effects of these medications on viral infection-induced respiratory diseases may be associated with clinical benefits, such as improvements in symptoms, quality of life, and mortality rate, and can prevent hospitalization and the exacerbation of chronic obstructive pulmonary disease, bronchial asthma, bronchiectasis, and diffuse panbronchiolitis.

Effects of high temperature on pandemic and seasonal human influenza viral replication and infection-induced damage in primary human tracheal epithelial cell cultures

High temperature reduces influenza viral replication; however, the treatment of fevers is thought to be necessary to improve patients' conditions. We examined the effects of high temperature on viral replication and infection-induced damage to human tracheal epithelial cells. Cell viability and dome formation were reduced, the number of detached cells was increased and lactate dehydrogenase (LDH) levels tended to be increased from 72 h to 120 h in uninfected cells cultured at 40 °C. Long-term (72 h and/or 120 h) exposure to high temperatures (39 °C and/or 40 °C) decreased RNA levels and/or viral titers of eight influenza virus strains. Cell viability and dome formation were reduced, and the number of detached cells and LDH levels were increased to a similar extent after infection with the A/H1N1 pdm 2009 virus at 37 °C and 40 °C. High temperature increased the endosomal pH, where the viral RNA enters the cytoplasm, in uninfected cells. High temperature reduced the production of IL-6, which mediate viral replication processes, and IL-1β and IL-8 in uninfected and infected cells. Based on these findings, high temperature may cause similar levels of airway cell damage after infection to cells exposed normal temperatures, although high temperature reduces viral replication by affecting the function of acidic endosomes and inhibiting IL-6-mediated processes.

MiR674 inhibits the neuraminidase-stimulated immune response on dendritic cells via down-regulated Mbnl3

Neuraminidase (NA), a structural protein of the H9N2 avian influenza virus (H9N2 AIV), can facilitate viral invasion of the upper airway by cleaving the sialic acid moieties on mucin. Dendritic cells (DCs) are major antigen-presenting cells whose immune functions, such as presenting antigens and activating lymphocytes, can be regulated by microRNAs. Here, we studied the molecular mechanism of miRNA-induced repression of immune responses in mouse DCs. First, we screened for and verified the miRNAs induced by NA. Then, we showed that, consistent with the H9N2 virus treatment, the viral NA up-regulated the expression of miR-155, miR-674, and miR-499 in DCs; however, unlike H9N2 virus treatment, the presence of NA was associated with reduced expression of miR-181b1. Our results suggest that NA significantly increased DC surface markers CD80 and MHCII and enhanced the ability of activating lymphocytes and secreting cytokines compared with HA, NP and M2. Meanwhile, we found that miR-674 and miR-155 over-expression increased all surface markers of DC. Nevertheless, by inhibiting the expression of miR-674 and miR-155, NA lost the ability to promote DC maturation. Furthermore, we predicted and demonstrated that Pgm2l1, Aldh18a1, Camk1d, and Mbnl3 were the target genes of miR-674. Among them, Mbnl3 interference strongly blocked the mature DCs. Collectively, our data shed new light on the roles of and mechanisms involved in the repression of DCs by miRNAs, which may contribute to efforts to develop a prophylaxis for the influenza virus.