1株对小鼠呈高致病性H5N1亚型禽流感病毒的遴选

Selection of H5N1 subtype avian influenza virus demonstrating high pathogenicity for mice

目的观察从死禽体内分离的禽流感H5N1病毒株对小鼠的致病情况,筛选一株可用于小鼠攻毒实验的H5N1毒株。方法将17株禽源H5N1病毒分别滴鼻感染6～8周龄Balb/c小鼠,观察其对小鼠的致病和致死情况。通过测定其中毒力较强一株的EID_(50)、TCID_(50)、小鼠LD_(50)及濒死小鼠不同组织中病毒载量,判定其致病力;采用遗传进化分析绘制HA基因进化树,了解其进化特征。结果动物实验表明,17株高致病性禽源H5N1毒株中,仅有一株对小鼠为高致病性。该毒株TCID_(50)/100μl=7.2,EID_(50)/100μl=8.325,小鼠1 LD_(50)/100μl=6.318≈10~2EID_(50)。鼻粘膜感染4～6 d小鼠发病,表现为精神萎靡、食欲减退、竖毛、弓背等临床症状,体重明显减轻。小鼠死亡集中在发病后的2～5 d,耐过死亡者12 d完全恢复正常。从濒死感染小鼠脾、肺、鼻及脑组织中皆可检出流感病毒NS片段,病毒数载量以脑组织中最多,达3.56×10^(10)拷贝/5μl。结论筛选到一株对小鼠呈强致病性H5N1亚型禽流感毒株,可以用于禽流感疫苗交叉保护效果评价的小鼠攻击实验,也可以作为感染模型用于H5N1禽流感病毒致病机制的研究。

As H5N1 avian influenza virus can infect mammalian, research of vaccine against H5N1 virus became urgent. Our study aimed to examine the infectious status of recent H5N1 viruses against Balb/c mice and select a highly pathogenic H5N1 virus. We inoculated mice were intranasally with 17 strains H5N1 viruses isolated from poultry in southern China. The virulence and lethality were observed, while TCID50 EID50, mice LD50 and virus loading were measured; the phylogenetic tree was drawn through HA sequence analysis. Among the 17 H5N1 strains, 1 was highly lethal to mice （TCID50/100μl = 7.2, EID50/100 μl=8.325, LD50/100 μl= 6.318≈ 10^2EID50）. Avian influenza virus NS segments were detected from lung, spleen, nose, and brain tissues of infected mice. The viral load in brain tissue was the highest, which was up to 3.56x10^10 copies/5 μl. These results indicate that most of H5N1 viruses from poultry are nonpathogenic for mice; this mouse model can be used to evaluate the cross-protection of avian influenza vaccine and also to investigate the prophylaxis and treatment of H5N1 avian influenza viruses.