Establishment of mammalian cell lines for constitutive expression of influenza virus matrix protein 2 / 病毒学报

To establish a mammalian cell line for stable expression of the matrix protein 2 (M2) of influenza virus type A. M2 gene was amplified by PCR from the influenza virus strain A/PR/8/34. The PCR product was cloned into eukaryotic expression vector pcDNA5/FRT. After identification with restriction enzyme digestion, the plasmid was co-transfected with plasmid pOG44 which expressed Flp in Flp-In-CHO cells. The target gene was integrated into chromosome of CHO cells by homologous recombination in vivo. Recombinant CHO-M2 cell lines were selected for hygromycin B resistance. A total of 15 recombinant cell strains with high expression of M2 protein were screened by hygromycin, and the expression of M2 protein was determined by IFA and Western blot. After subculturing for 10 passages, the presence of M2 gene in the CHO-M2 cells was confirmed by PCR, and the expression of M2 protein were proved by IFA and Western blot. We successfully constructed a mammalian cell line which stably expressed M2 protein of influenza virus type A. The cell line will be useful for studies on function of M2 protein and provide tools for novel influenza virus vaccine development.

Household and community transmission of the Asian influenza A (H2N2) and influenza B viruses in 1957 and 1961.

This study analyzed the distribution of the number of cases in households of various sizes, reconsidering previous survey data from the Asian influenza A (H2N2) pandemic in 1957 and the influenza B epidemic in 1961. The final size distributions for the number of household cases were extracted from four different data sources (n = 547, 671, 92 and 263 households), and a probability model was applied to estimate the community probability of infection (CPI) and household secondary attack rate (SAR). For the 1957 Asian influenza pandemic, the CPI and household SAR were estimated to be 0.42 [95% confidence intervals (CI): 0.37, 0.47] and 7.06% (95% CI: 4.73, 9.44), respectively, using data from Tokyo. The figures for the same pandemic using data from Osaka were 0.21 (95% CI: 0.19, 0.22) and 9.07% (95% CI: 6.73, 11.53), respectively. Similarly, the CPI and household SAR for two different datasets of influenza B epidemics in Osaka in 1961 were estimated as 0.37 (95% CI: 0.30, 0.44) and 18.41% (95% CI: 11.37, 25.95) and 0.20 (95% CI: 0.13, 0.28) and 10.51% (95% CI: 8.01, 13.15), respectively. Community transmission was more frequent than household transmission, both for the Asian influenza pandemic and the influenza B epidemic, implying that community-based countermeasures (eg, area quarantine and social distancing) may play key roles in influenza interventions.