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Objective To analyze the genetic stability of master virus seed lots of live attenuated influenza vaccineA/17/California/2009/38(H1N1)andA/17/Perth/09/87(H3N2)strains.Methods The master virus seed lots were inoculated into chicken eggs for subculture.The complete genome of the 2nd, 3rd, 5th and 10th generations of viruses were amplified and sequenced.The genes encoding hemagglu-tinin ( HA) and neuraminidase ( NA) were compared with those of the WHO recommended circulating wild-type virus strains used for vaccine production in northern hemisphere during 2011-2012 influenza season.Six internal genes (PB2, PB1, PA, NP, M and NS) of each virus generation were compared with their master donor virus strain (A/Leningrad/134/17/57) for the evaluation of the genetic stability.Results The muta-tion rates of H1N1 and H3N2 strains after 10 passages were 0.035%and 0.022%, respectively.No muta-tions were found at the critical sites for controling thecold adapted ( ca) , temperature sensitive ( ts) and at-tenuated ( att) phenotypes.Conclusion The live attenuated influenza vaccine strains possessed high genet-ic stability as their tenth generations still shared 99% of homology with the original seed lots.All of the working virus seed lots met the requirements of Pharmacopoeia of the People′s Republic of China ( 2010 edition) .
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Coxsackievirns A16(CVA16),together with enterovirus type 71(EV71),is responsible for most cases of hand,foot and mouth disease(HFMD) worldwide.Recent findings suggest that the recombination between CVA16 and EV71,and the co-circulation of these two viruses may have contributed to the increase of HFMD cases in China over the past few years.It is therefore important to further understand the virology,epidemlology,virus-host interactions and host pathogeuesis of CVA16.In this study,we describe the viral kinetics of CVAI6 in human rhabdomyosarcoma(RD) cells by analyzing the cytopathic effect(CPE),viral RNA replication,viral protein expression,viral RNA package and viral particle secretion in RD cells.We show that CVA16 appears to first attach,uncoat and enter into the host cell after adsorption for 1 h.Later on,CVA16 undergoes rapid replication from 3 to 6 h at MOI 1 and until 9 h at MOI 0.1.At MOI 0.1,CVA16 initiates a secondary infection as the virions were secreted before 9 h p.i.CPE was observed after 12 h p.i.,and viral antigen was first detected at 6 h p.i.at MOI 1 and at 9 h p.i.at MOI 0.1.Thus,our study provides important information for further investigation of CVA16 in order to better understand and ultimately control infections with this virus.