Dose- and Time-Dependent Apoptosis Induced by Avian H9N2 Influenza Virus in Human Cells

Abstract

To understand human response to avian H9N2 influenza, we investigated the effects of the viral infection on A549, HepG2, and HeLa cells at low and high MOIs. To identify virus-host interplay, expression of Mx and NP genes was measured in the cells supernatants. Cell viability and apoptosis were evaluated by MTT assay, DNA fragmentation, and florescent staining. The virus titration and NP gene transcript levels indicate lower susceptibility of HeLa cell to H9N2 replication than other cells. Although H9N2 did produce a faster CPE in HepG2, high dose of the virus induced apoptosis within early stage of A549 infection. The DNA laddering was enhanced in the cell correlated with increase in virus transcripts. The undetectable to different regulation levels of Mx gene were observed in response to H9N2 infection suggesting that an insufficient antiviral defense in the noncompetent-IFN HepG2 cell promotes efficient viral replication. These results showed that the permissivity of HepG2 for H9N2 is comparable with A549; however, liver cells are not target tissue respond to the infection. These data revealed that the H9N2 virus induced apoptosis signaling via mitochondrial pathway in human alveolar epithelial cells, indicating that the induction may be associated with a dose-dependent manner.

The Novel H7N9 Influenza A Virus NS1 Induces p53-Mediated Apoptosis of A549 Cells

“…The host utilizes apoptosis to eliminate influenza A virus by removing virus-infected cells, while viruses can modulate apoptosis for their effective replication and survival [26][27][28][29]. Previous studies have shown that the H9N2 virus induces apoptosis mainly via the mitochondrial pathway in human alveolar epithelial cells [20], and NS1 from H9N2 virus can induce death receptor-mediated apoptosis in chicken macrophages [19]. This prompted us to investigate if the NS1 protein of the novel avian H7N9 influenza A virus can also induce apoptosis in human cells, like its closely-related H9N2 virus, or the NS1 protein of H9N2 in chicken cells.…”

“…It has been previously reported that NS1 derived from low pathogenicity H9N2 virus can induce apoptosis in chicken macrophages via the Fas/(FasL)-mediated pathway [19], while in human alveolar epithelial cells, H9N2 virus-induced apoptosis proceeds via the death receptor and mitochondrial pathways in parallel [20]. Although the NS1 gene of the novel H7N9 influenza A virus is derived from the closely-related avian H9N2 virus, several amino acids in NS1 protein of this novel H7N9 influenza A virus has changed (Fig.…”

Caspase Cleavage Motifs of Influenza Subtypes Proteins: Alternations May Switch Viral Pathogenicity

“…The highly virulent H5N1 virus induced apoptosis in mammalian alveolar epithelial cells and chicken cells resulted in the deregulation of adaptive immune responses (20,21). The low pathogenic H9N2 virus can induce apoptosis in chicken macrophages by the Fas/(FasL)-mediated extrinsic pathway (18,19) and human alveolar epithelial cells in a time and dose-dependent manner (11). The widespread prevalence of H9N2 subtype in the Middle East region (6,31) and isolation of high lethally H9N2 for mice (8) …”

“…Several studies on interaction between influenza viruses and hosts revealed that the infection causes apoptosis or programmed cell death in natural hosts. A variety of host and viral factors are involved in induction of apoptosis that may depend on the cell type (8)(9)(10)(11)(12). The regulation of some host apoptotic factors like cysteinyl-aspartatekinases (caspases) activation interacts with influenza virus replication and pathogenicity (13,14).…”

Proteomic Analysis of Differential Expression of Cellular Proteins in Response to Avian H9N2 Virus Infection of A549 Cells

“…The A549 cell line, which originated from human airway epithelial cells, was found susceptible to a strain of H9N2 influenza viruses that we screened (unpublished data). In addition to this, A549 cell line has been used for H9N2 in vitro studies (Lee et al, 2010; Shahsavandi et al, 2013; Hamidreza et al, 2016). Therefore, the A549 cell line was selected for the present proteomic study.…”