肺炎支原体P1蛋白预防动物支原体肺炎的研究

Prevention of pneumonia in hamsters with Mycoplasma pneumoniae P1 protein

目的 探索肺炎支原体 (MP)P1蛋白对肺炎支原体感染动物的预防效果。方法 从大量培养的肺炎支原体FH株提取获得P1蛋白 ,将 30只金黄地鼠随机分为P1组、未免疫组。用P1蛋白对P1组鼠进行 2次免疫后 ,两组均用支原体菌液进行感染 ,隔期处死 ,观察支气管肺泡灌洗液肺炎支原体培养结果及分泌型免疫球蛋白A(sIgA)的变化 ,血清IgM、IgG、IgA的改变以及肺组织的病理情况。结果 P1组支气管肺泡灌洗液肺炎支原体培养均为阴性 ,未免疫组阳性率为 73% ;P1组支气管肺泡灌洗液sIgA明显高于未免疫组。血清IgG两组从第 2周均开始增高 ,但P1组峰值出现早于未免疫组 ;血清IgMP1组和未免疫组变化趋势相似 ,均在第 2～ 4周增高 ;血清IgA两组均无明显变化。肺组织病理改变显示 :未免疫组 15只鼠均出现肺炎改变 ,且病变较重 ,而P1组只有 3只出现较轻病变。

Objective P1 protein is one of the important antigens and a protein with special biological activity situated on the thorny bottom of Mycoplasma pneumoniae (Mp) with a molecular weight of 17000. The 821 871 amino acids of P1 protein have the epitopes binding to T and B lymphocytes which can activate cellular and humoral immune function. The aim of this study was to investigate effect of P1 protein in prevention of MP pneumonia in hamsters. Methods P1 protein was extracted by using two step solubilization and size exclusion chromatography from quantitively cultured MP. Thirty hamsters were divided into 2 groups at random: P1 unimmunized groups and P1 protein immunized group (P1 group). Hamsters in P1 group were immunized with P1 protein twice. Then both groups were infected with Mp strain FH. Three hamsters from each group were sacrificed every 2 weeks and bronchoalveolar lavage (BAL) was cultured for Mp. Secretary IgA (sIgA) in BAL and serum IgM, IgG, IgA were detected, and histopathological examination was performed on lung tissue specimens. Results The Mp culture of BAL in P1 group was negative from 2 to 10 weeks; while in unimmunized group, the culture for Mp was positive in 3/3,3/3,2/3,2/3 and 1/3 hamsters at weeks 2,4,6,8,and 10 weeks,respectively. The total rate of Mp infection was 11/15 (73 %). BAL sIgA of P1 group elevated in initial 2 weeks postinfection with MP,apparently higher than that of unimmunized group,and reached its peak value at week 6,and maintained at relatively high level. BAL sIgA of unimmunized group was lower than that of normal control group,then gradully elevated at weeks 4 and 6,and reached its peak at week 8 and returned to normal level at week 10. There was significant difference between P1 group and unimmunized group during the same period. Serum IgG in P1 group and unimmunized group initially increased at week 2; however, the value of P1 group reached its peak earlier than that of unimmunized group. Serum IgM of the two groups had a similar fluctuating pattern, elevated at weeks 2 and 4. Serum IgA had no significant change. Lung histopathological changes showed that 15 hamsters of unimmunized group suffered from pneumonia and had relatively severe condition. However, only 3 of 15 hamsters in P1 group had mild changes. Conclusion Mp P1 protein showed a preventive effect against pneumonia in hamsters infected with Mp.