Objective To study the apoptotic effects of influenza A virus on the Raji cell line. Methods Cultured Raji cells were infected with influenza A virus at a multiplicity of infection (m.o.i) of 20 and the effects of apoptosis were detected at different time points post infection using the following methods: electron microscope, DNA agarose gel electrophoresis, PI stained flow cytometry (FCM) and Annexin-V FITC/PI stained FCM.Results Raji cells infected with influenza A virus showed changes of morphology apoptotis, DNA agarose electrophoresis also demonstrated a ladder-like pattern of DNA fragments in a time-dependent manner. PI stained FCM showed 'apoptosis peak' and FITC/PI stained FCM showed apoptotic cells. Quantitative analysis indicated that the percentage of apoptotic Raji cells increased after infection, and cycloheximide (CHX), an eukaryotic transcription inhibitor, could effectively inhibit the apoptotic effects of influenza A virus in vitro.Conclusions Influenza A virus can induce apoptosis in Raji cell line suggesting that it may lead to a potential method for tumor therapy.
In order to explore the feasibility and protective efficiency of influenza DNA vaccine, we constructed eukaryotic expressing plasmids encoding HA and HA1 of influenza A virus （A/PR/8/34） and studied their expression in HEK293 cells. HA and HA1 genes were amplified by RT-PCR and cloned into pcDNA3.1（+） to generate pcDNA3.1（+）/HA and pcDNA3.1（+）/HA1, respectively. After verification of the cloning fidelity by restriction endonuclease digestion, PCR, and sequencing, pcDNA3.1（+）/HA and pcDNA3.1（+）/HA1 were transfected into HEK293 cells using PolyFect Transfection Reagent. Immunofluorescence assay was used to detect the transient expressing cells. Fluorescence microscopy revealed strong expression of target gene in HEK293 cells transiently transfected with either pcDNA3.1（+）/HA or pcDNA3.1（+）/HA1. Therefore, the results confirm the successful construction of eukaryotic expressing plasmids capable of driving the eukaryotic expression of influenza virus antigen HA and HA1, which is likely to provide a basis for both further investigation of the mechanism of influenza viral infection and the development of influenza DNA vaccine.
