AA-PR8冷适应流感病毒疫苗株在小鼠中的保护作用

Protective effect of cold-adapted influenza virus vaccine strain AA-PR8 in mice

目的将AA-PR8冷适应流感病毒疫苗株免疫小鼠,检测小鼠IgG和IgA抗体产生情况,并对免疫后小鼠进行PR8流感病毒攻击,评价其保护效果。方法用AA-PR8冷适应流感病毒疫苗株滴鼻免疫小鼠2次,免疫间隔21 d,分别于第1次免疫后0、7、14、21、28、35和42 d采集小鼠血清和肺泡灌洗液,间接ELISA法检测IgG和IgA抗体效价。对采用1次免疫或0、14 d 2次免疫程序的小鼠进行5倍半数致死剂量的PR8流感病毒攻击,观察攻击后小鼠死亡情况及体重变化,攻击后第3天取小鼠肺脏,检测病毒载量。结果小鼠第1次免疫后7、14和21 d,血清IgG抗体GMT分别为152、230和264,肺泡灌洗液IgA抗体GMT分别为23、211和92;第2次免疫后7、14和21 d,血清IgG抗体GMT分别为348、919和1056,肺泡灌洗液IgA抗体GMT分别为53、368和160。免疫1次后14 d进行攻击,小鼠保护率为83.33%(5/6),体重降低幅度减少,肺脏病毒载量显著降低;0、14 d免疫2次后14 d进行攻击,小鼠保护率为100%(6/6),体重基本不降低,肺脏未检测到病毒。结论AA-PR8冷适应流感病毒疫苗株在小鼠中具有良好的免疫原性,显著降低小鼠AA-PR8流感病毒攻击后的肺脏病毒载量,提高了生存率。

Objective To determine IgG and IgA antibodies in mice immunized with cold-adapted influenza virus vaccine strain AA-PR8,and challenge the immunized mice with PR8 influenza virus to evaluate the protective effect.Methods Mice were intranasally immunized with cold-adapted influenza virus vaccine strain AA-PR8 twice at an interval of 21 d,of which the serum and alveolar lavage fluid samples were collected 0,7,14,21,28,35 and 42 d after the first dose and determined for IgG and IgA antibody titers by indirect ELISA.Mice immunized with a single dose or two doses at an interval of 14 d were challenged with 5 times of the median lethal dose of PR8 influenza virus,and observed for death and bodyweight change,of which the viral load in lung were determined on day 3 after challenge.Results The GMTs of serum IgG antibody 7,14 and 21 d after the first dose were 152,230 and 264,while those of IgA in alveolar lavage fluid were 23,211 and 92,respectively.However,the GMTs of serum IgG antibody 7,14 and 21 d after the second dose were 348,919 and 1056,while those of IgA antibody in alveolar lavage fluid were 53,368 and 160,respectively.The protective rate of mice challenged 14 d after immunization with a single dose was 83.33%(5/6),while the weight loss decreased,and the lung viral load decreased significantly.However,the protective rate of mice immunized with two doses and challenged 14 d after the second dose was 100%(6/6),while few bodyweight loss was observed,and no virus was detected in lung.Conclusion Cold-adapted influenza virus vaccine strain AA-PR8 showed good immunogenicity in mice,which significantly decreased the viral load in lung and increased the survival rate of mice challenged with PR8 influenza virus.