以BALB/c小鼠为模型, 探讨H7N9流感病毒灭活疫苗免疫小鼠后所诱导的长效体液免疫应答的动态变化。不同剂量的流感H7N9全病毒灭活疫苗单独或辅以MF59佐剂肌肉注射免疫小鼠一次。连续采集免疫后小鼠15个月的血清, 用ELISA方法检测特异性IgG抗体水平, 血凝抑制(hemagglutination inhibition, HI)试验和微量中和(microneutralization, MN)试验检测第15个月时的HI抗体和中和抗体效价。实验结果发现, 小鼠血清中的特异性IgG抗体水平随时间变化持续缓慢上升, 第5个月时达到顶峰, 随后略有下降但一直持续平稳状态; IgG抗体滴度与疫苗剂量成正相关, 且添加佐剂能提高抗体滴度。HI及MN抗体检测表明, 免疫后第15个月产生的抗体能有效中和病毒, 且抗体跟疫苗剂量成正比。以上研究表明, H7N9流感病毒灭活疫苗免疫小鼠一次诱导产生的特异性抗体能在较长期内保持比较平稳的抗体滴度, 为小鼠提供免疫保护; 增加抗原剂量和添加MF59佐剂能增加疫苗特异性抗体水平。该研究为H7N9流感疫苗产生的长期保护效应提供了一定的数据积累和参考。

Specific antibody responses induced by inactivated H7N9 influenza vaccine were determined in BALB/c mice within a long period of time after immunization. BALB/c mice were intramuscularly injected once with the vaccine alone or plus MF59 adjuvant. Sera samples were consecutively collected from tail vein within 15 months following vaccination. Vaccine-specific IgG antibody titers were detected by ELISA. HI and neutralization antibody levels were also measured in samples of the last month. It was found that specific antibody levels increased slowly along with time and peaked during 5 months, then declined a little. However, they were relatively stable since then. The antibody levels were positively correlated with the vaccine dosage and were improved by addition of MF59. HI and MN tests showed that antibodies produced after 15 months of immunization could effectively neutralize virus and the neutralizing antibody titers were proportional to the amount of antigen. The experiments demonstrated that immunization once with H7N9 inactivated vaccine could induce relatively stable levels of specific antibodies and provide long-term protection for mice. Increase of vaccine dosage and addition of MF59 adjuvant could raise the humoral immune responses.