浙江省1 998年H3N2流感流行的溯源研究

目的 对1998年浙江省的H3N2流感流行进行溯源研究.方法 采用RT-PCR扩增浙江省1998年3株H3N2流感流行代表株的全基因组序列,并与GenBank上1995-1998年世界其他地区H3N2流感流行株进行比较;同时,采用交叉血凝抑制实验,计算各毒株间的抗原比.结果 HA基因进化树表明,1998年浙江省H3N2优势流行株A/Zhejiang/11/98、A/Zhejiang/18/98与1995-1996年世界各地以及1997年我国大陆的H3N2流行株间存在显著差异,在进化树上虽与A/Sydney/5/97同属一簇,但和美国纽约以及中国香港1997年后期流行株更为接近.在HA1、NA和MP基因上,A/Zhejiang/18/98与香港1997年后期流行株同源性最高,而在PA、HA和NS基因上,与纽约流行株的遗传距离也小于A/Sydney/5/97.A/Zhejiang/18/98与香港或纽约株在HA1区仅存在1～3个位点的氨基酸残基不同,而与A/Sydney/5/97存在7个位点的氨基酸残基差异,其中3个位点于抗原决定簇区.各毒株间的交叉血凝抑制实验表明A/Zhejiang/18/98与A/Sydney/5/97的抗原比已达2.0,提示二者在抗原性上存在一定差异.此外,1997-1998年H3N2各地流感流行的起始时间序列,也显示了该次流感传播的可能途径.结论 浙江省1998年H3N2流感的流行很可能是由1997年底H3N2新型流感变异株经纽约和香港输入中国大陆所导致.

Traceability of the A/H3N2 virus borne influenza pandemic in Zhejiang province, 1998

Objective To trace back to the influenza pandemic caused by A/H3N2 virus happened in Zhejiang province,1998.Methods The whole genome of three isolates related to Zhejiang influenza virus was amplified through RT-PCR,and the identified sequences were aligned with the sequences downloaded from GenBank of the H3N2 strains which were circulating in other regions during 1995 to 1998.The crossing HAI titers of the reference strains were measured by HAI test and antigenic ratios were calculated.Results The Phylogenetic tree,constructed based on HA sequence showed that the dominant strains A/Zhejiang/11/98 and A/Zhejiang/18/98 were significant different from the isolates circulated in other regions during 1995 to 1996 and the strains isolated in the mainland of China,in 1997.Although the A/Zhejiang/11/98 and A/Zhejiang/18/98 strains were distributed in the same cluster with A/Sydney/5/97,the two strains were closer to the epidemic strains isolated in Hong Kong and New York in the later part of 1997.Based on HAI,NA and MP genes,A/Zhejiang/18/98 seemed to be the closest one to the Hong Kong epidemic strains,and the genetic distances between A/Zhejiang/18/98 and New York strains were shorter than that with A/Sydney/5/97 based on PA,HA and NS genes.There were only 1-3 amino acid differences between A/Zhejiang/18/98 and Hong Kong or New York strains,whereas 7 amino acid differences with A/Sydney/5/97,in which three were located in the antigenic determinant regions.Data from the crossing HAI test showed that the antigenic ratio between A/Zhejiang/18/98 and A/Sydney/5/97 had reached 2.0,indicating the antigenic difference to a certain extent.Additionally,the onset of the influenza epidemic during 1997 to 1998 also suggested the possible route of transmission related to this H3N2 virus.Conclusion The influenza pandemic occurred in Zhejiang province in 1998 was possibly caused by the importation of a newly identified H3N2 influenza variant via Hong Kong and New York in late 1997.