Critical Role of HAX-1 in Promoting Avian Influenza Virus Replication in Lung Epithelial Cells

Figure 1

PB1-F2 was critical to influenza virus replication and sensitized human lung epithelial cells for apoptosis. (a) Generation of a PB1-F2-deficient H9N2 virus mutant, H9N2 (ΔPB1-F2). A premature stop codon (TAA) was introduced to replace a serine (TCA) in wild-type virus, H9N2 (wt), without altering a valine in the PB1 and N40 coding sequences. (b) Reduced size of viral plaques in the absence of PB1-F2. MDCK cells were inoculated with the H9N2 (wt) or H9N2 (ΔPB1-F2) viruses (on the right), and a standard plaque assay was performed. (c) Decreased viral titers of H9N2 (ΔPB1-F2) replicating in human lung epithelial cells A549. The titration of viral titers was duplicated, and mean ± SD values were shown (Student’s t-test, ). (d) Early apoptosis induced by PB1-F2. A549 cells were infected with H9N2 (wt) or H9N2 (ΔPB1-F2) and trypsinized at 6, 12, and 24 hrs post infection to obtain single-cell suspensions, which were subsequently stained with FITC-annexin V and propidium iodide (PI) before being analyzed with flow cytometry.

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