H5N1 Avian Influenza Virus Induces Apoptotic Cell Death in Mammalian Airway Epithelial Cells

Abstract

In recent years, the highly pathogenic avian influenza virus H5N1 has raised serious worldwide concern about an influenza pandemic; however, the biology of H5N1 pathogenesis is largely unknown. To elucidate the mechanism of H5N1 pathogenesis, we prepared primary airway epithelial cells from alveolar tissues from 1-year-old pigs and measured the growth kinetics of three avian H5 influenza viruses ( These results suggest that only H5N1 induces apoptosis in pAEpC. H5N1 cytopathicity was inhibited by adding the caspase inhibitor z-VAD-FMK; however, there were no significant differences in viral growth or release of progeny viruses. Further investigations using reverse genetics demonstrated that H5N1 hemagglutinin protein plays a critical role in inducing caspase-dependent apoptosis in infected pAEpC. H5N1-specific cytopathicity was also observed in human primary airway epithelial cells. Taken together, these data suggest that avian H5N1 influenza virus leads to substantial cell death in mammalian airway epithelial cells due to the induction of apoptosis.

Avian Influenza Virus Infection of Immortalized Human Respiratory Epithelial Cells Depends upon a Delicate Balance between Hemagglutinin Acid Stability and Endosomal pH

“…A similar phenomenon is observed in bovine mastitis, in which bacterial infection damages the blood-milk barrier resulting in increased pH values in milk (50). We previously reported that H5N1 viruses induce apoptosis in duck embryonic fibroblasts and mammalian airway epithelial cells (10,51), supporting the hypothesis that luminal pH changes occur in the intestine of H5N1-infected birds.…”

“…Viruses and Cells-Influenza virus strains A/crow/Kyoto/ 53/04 (H5N1) (Cw/Ky (H5N1)) and A/chicken/Egypt/CL6/07 (H5N1) (Ck/Eg (H5N1)) were isolated from embryonated chicken eggs inoculated with tracheal or lung homogenates from dead crows (10) or dead chickens (11), respectively. A/Beijing/262/95 (H1N1) (Beijing (H1N1)), A/Duck/Hong Kong/ 273/78 (H2N2) (Dk/Hk (H2N2)), A/Panama/2007/99 (H3N2) (Panama (H3N2)), A/Duck/Hong Kong/668/79 (H4N5) (Dk/ Hk (H4N5)), A/Duck/Hong Kong/820/80 (H5N3) (Dk/Hk (H5N3)), A/Turkey/Ontario/7732/66 (H5N9) (Tk/Ont (H5N9)), A/Duck/Hong Kong/960/80 (H6N2) (Dk/Hk (H6N2)), A/wigeon/ Osaka/1/01 (H7N7) (Wg/Os (H7N7)), A/Turkey/Ontario/6118/67 (H8N4) (Tk/Ont (H8N4)), and A/Duck/Hong Kong/448/78 (H9N2) (Dk/Hk (H9N2)) were kind gifts from Yoshinobu Okuno (Kanonji Institute, the Research Foundation for Microbial Diseases of Osaka University, Kagawa, Japan).…”

“…The full-length sequences of both A/duck/Egypt/D1Br/2007 (H5N1) (Dk/Eg (H5N1)) (clade 2.2.1) (PB2, PB1, PA, HA, NP, NA, M, and NS) (11) and Dk/Hk (H5N3) (PB2, PB1, PA, HA, NP, NA, M, and NS) were constructed by PCR. The virulent HA sequence of Dk/Hk (H5N3) was constructed by changing single basic amino acids within the HA cleavage site to multiple basic amino acids (NЈ-TR-CЈ to NЈ-RRKKR-CЈ), as described previously (10). The HA genomes of H5N1 (Cw/Ky (H5N1), Ck/Eg (H5N1), Thailand (H5N1), Indonesia (H5N1), or Shanghai (H5N1)) and the eight-segment sequence of Dk/Eg (H5N1) and Dk/HK (H5N3), including the virulent HA sequence, were cloned into the transcription plasmid, pPOLI (14).…”

Osteopontin Exacerbates Pulmonary Damage in Influenza-Induced Lung Injury

“…In influenza virus pneumonia, alveolar epithelial cell apoptosis is induced by macrophages through the release of tumor necrosis factor-related apoptosis-inducing ligand (6). Avian influenza A virus H5N1 induces apoptosis in alveolar epithelial cells via the caspase-dependent pathway (9). PolyI:C, an analog of dsRNA, can induce a marked inflammatory response in the lungs and lead to impairment of pulmonary function.…”

“…Respiratory epithelial cells are the major target of viral replication (8). In vitro, the H5N1 subtype of the influenza virus causes substantial death of mammalian airway epithelial cells due to the induction of apoptosis (9). The apoptosis or death of the alveolar epithelium, especially, ATII cells, is an underlying mechanism of alveolar damage in murine and human influenza virus infections (10).…”