Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: A single-amino-acid substitution in the HA protein changes the replication and pathogenicity of the 2009 pandemic A (H1N1) influenza viruses in vitro and in vivo | Xu et al. Virology Journal 2010 7 325 http content 7 1 325 VIROLOGY JOURNAL RESEARCH Open Access A single-amino-acid substitution in the HA protein changes the replication and pathogenicity of the 2009 pandemic A H1N1 influenza viruses in vitro and in vivo Lili Xu Linlin Bao Qi Lv Wei Deng Yila Ma Fengdi Li Lingjun Zhan Hua Zhu Chunmei Ma Chuan Qin Abstract Background The novel pandemic A H1N1 virus was first identified in Mexico in April 2009 and since then it spread world wide over a short period of time. Although the virus infection is generally associated with mild disease and a relatively low mortality it is projected that mutations in specific regions of the viral genome especially within the receptor binding domain of the hemagglutinin HA protein could result in more virulent virus stains leading to a more severe pandemic. Results Here we found that a single amino acid substitution of Asp-to-Gly at position 222 in the HA protein of the A H1N1 virus occurred after two passage propagation in the allantoic cavities of chicken embryonated eggs and this single residue variation dramatically increased the viral replication ability in MDCK cells and pathogenicity in BALB c mice. Conclusions A substitution of Asp-to-Gly at position 222 in the HA protein was prone to occur under positive selection pressures and this single amino acid mutation could dramatically increase the virus replication ability in vitro and pathogenicity in vivo. Our finding offers a better understanding of the transmission and evolution of the 2009 pandemic A H1N1 virus and brings attention to further potentially severe influenza pandemic that may result from cross-host evolution of the influenza viruses. Background On June 11 2009 the World Health Organization raised the global pandemic alert level to phase 6 the pandemic phase in response to the emergence and global spread of a novel A H1N1 influenza virus which emerged in Mexico in early 2009 1 . The onset of the pandemic A
