血凝素蛋白145位潜在糖基化位点对H9N2禽流感病毒生物学特性的影响

Effect of the Potential Glycosylation Site at HA145 on the Biological Characteristics of H9N2 Avian Infl uenza Virus

从某肉鸡场分离的A/Chicken/Jiangxi/106/2012(H9N2)(JX106)毒株,其HA蛋白在145位氨基酸由S突变为N,使得在该处增加了一个潜在的糖基化位点NGT。本研究以JX106为研究对象,通过反向遗传操作获得重组病毒rgJX106-HA145N和rgJX106-HA145S。利用不同方法探究了HA蛋白145位糖基化位点对病毒的毒力、复制、受体亲和力和致病性等方面的影响。研究发现,rgJX106-HA145N和rgJX106-HA145S在A549细胞上的复制、对鸡胚的感染力无明显差异,而HA蛋白145位无糖基化位点的rgJX106-HA145S与α2,6-唾液酸受体的亲和力更强,在小鼠肺脏中复制更快、致病力更强且能产生更高的交叉HI效价,这一结果提示流感病毒血凝素的糖基化对病毒诱导的体液免疫具有重要影响。

Previous studies have reported that the Avian influenza virus A/Chicken/Jiangxi/106/2012(H9N2,JX106)isolated from a broiler farm has a S to N mutation at amino acid position 145 of HA protein,which may produce a new potential glycosylation site in HA.In this study,reassort viruses rgJX106-HA145N and rgJX106-HA145S were rescued by reverse genetic system and used to investigate the effect of S145N substitution on viral growth kinetic,receptor affinity and pathogenicity in mice.We found that S145N mutation had no effect on the growth of the virus in both chicken embryos and A549 cells.The reassort virus rgJX106-HA145S had no glycosylation site at position 145 of HA protein but preferred to bind withα2,6-sialic acid receptors.In addition,mice inoculated with rgJX106-HA145S showed higher viral titers in the lungs than the rgJX106-HA145N at day 3 post infection.Moreover,the rgJX106-HA145S caused more significant weight loss in mice and induced higher cross-reactive antibodies.All results indicated that the glycosylation in HA had an important impact on humoral immunity.