大沙鼠感染鼠疫耶尔森菌后F1抗体变化情况

Dynamics of F1 antibody responses to Yersinia pestis infection in Rhombomys opimus

目的 观察大沙鼠感染鼠疫耶尔森菌（鼠疫菌）后F1抗体反应及动态变化情况.方法 大沙鼠捕获于2011年新疆维吾尔自治区准噶尔盆地鼠疫自然疫源地南缘,共211只,其中未感染鼠疫菌的大沙鼠为167只,感染鼠疫菌的为44只.实验菌株采用2504号鼠疫菌,该株鼠疫菌硝酸盐还原实验阴性,为强毒菌.采用随机数字法选取35只未感染鼠疫菌大沙鼠并平均分为7组（6个实验组和1个对照组）,用按10倍梯度稀释成的1×10^6-1×10^11 CFU/ml浓度梯度菌液对1-6实验组大沙鼠进行第1次感染,对照组皮下鼠蹊部注射生理盐水,感染量均为1 ml;选取已感染过鼠疫菌且首次检测F1抗体滴度在1：256-1：4096之间的大沙鼠共17只,按照抗体滴度进行分为1：4096组（4只）、1：2048组（4只）、1：1024组（3只）、1：512组（3只）、1：256组（3只）,并于每30天尾部无菌采血1次进行F1抗体检测,共检测5次;从剩余感染过鼠疫菌的大沙鼠中选取经2次检测F1抗体阴性的大沙鼠共9只,采用浓度为1×10^6 CFU/ml菌液进行第2次感染,感染量为1 ml.第1次和第2次感染后的大沙鼠,均于感染后的第3、5、7、15、30、60、90和120天尾部采血检测鼠疫F1抗体.采用一元线性回归方程建立大沙鼠抗体衰减回归模型.结果 第1次感染鼠疫菌的大沙鼠中,1×10^6-1×10^8 CFU/ml组分别在第30、15和15天时检出抗体,抗体阳性率分别为1/4、3/4、4/5,1×10^7和1×10^8 CFU/ml组均在第120天时达到最高抗体滴度,均为1：256;1×10^9、1×10^10和1×10^11 CFU/ml组,在第5天至第7天时可检出抗体,且在第7天至第15天时大沙鼠全部抗体阳转,1×10^11 CFU/ml组在第120天时达到最高抗体滴度,为1：4096.第2次感染鼠疫菌的大沙鼠中,第3天即可检出抗体阳性,阳性率为2/9,至第90天达到最高抗体滴度,为1：2048.大沙鼠F1抗体衰减的一元线性回归方程为y=0.045x-0.321（F=115.40,P〈0.001）,从F1抗体滴度1：4096衰减至0的最短时间为140 d,最长为200 d.结论 感染高浓度鼠疫菌菌液的大沙鼠F1抗体产生的时间较短,其抗体阳性率也较高,抗体滴度最高时可达1：4096;F1抗体衰减时间长,约在140-200 d之间.

Objective To observe the dynamics of antibody response in great gerbils infected with Yersinia pestis in experiment. Method A total of 211 great gerbils were captured in the southern margin of plague natural focus of Junggar Basin of the Xinjiang Uygur Autonomous Region in 2011. Among them, there were 167 great gerbils without infection of Y. pestis and 44 great gerbils infected by Y.pestis. Y.pestis No. 2504 was employed for this experimental strain, which was strong toxic strain with negativity in the reduction experiment of nitrate. 35 great gerbils without the infection of Y. pestis were divided randomly and averagely into 7 groups including 6 experimental groups and 1 control group. Great gerbils in the 1st to 6th experimental groups were exposed first with 1 × 10^6-1 × 10^11 CFU/ml of bacterial fluid with 10 times of gradient dilution; groin areas of great gerbils in the control group were injected subcutaneously with physiological saline;and the amount of infection was all 1 ml. 17 great gerbils infected with Y. pestis and the first detection of F1-antibody titer in 1：256-1：4096 were grouped according to F1-antibody titer： group 1：4096 （n=4）, group 1：2048 （n=4）, group 1：1024 （n=3）, group 1：512 （n=3） and group 1：256 （n=3）;and blood in caudal regions was collected in asepsis for the detection of F1-antibody, with a total of 5 times.9 great gerbils which were selected from the remaining great gerbils infected with Y. pestis and detected F1-antibody negative 2 times were exposed 1×10^6 CFU/ml of bacterial fluid for the second infection, with the amount of infection being 1 ml. Blood in caudal regions of great gerbils after the first and second infection were collected for the detection of plague F1-antibody on the 3rd, 5th, 7th, 15th, 30th, 60th, 90th and 120th day after infection. Declined regression models for great gerbils＆#39; antibodies were established with unary linear regression equation;declined change diagrams for the antibodies were drawn to observe the declined F1-antibody after great gerbils were exposed to Y. pestis. Results In great gerbils with the first infection of Y. pestis, antibodies were detected in the 1 × 10^6-1 × 10^8 CFU/ml of group on the 30th, 15th and 15th day, respectively; the positive rates of antibody were 1/4, 3/4 and 4/5, respectively; the group 1 × 10^7 and 1 × 10^8 CFU/ml reached to the highest antibody titer with 1：256 on the 120th day;antibodies were revealed in the group 1×10^9, 1×10^10 and 1×10^11 CFU/ml from the 5th to 7th day when the seroconversion of all antibodies was observed;group 1×10^11 CFU/ml reached to the highest antibody titer on the 120th day with 1：4096. In the great gerbils with the second exposure to Y.pestis, positive antibodies were detected on the 3rd day with the positive rate being 2/9; and the highest antibody titer with 1：2048 was noted on the 90th day. Unary linear regression equation of declined F1 antibody of great gerbils was y=0.045x-0.321（F=115.40,P〈0.001）, and the shortest duration for F1-antibody titer declining from 1：4096 to 0 was 140 d and the longest duration 200 d. Conclusion Great gerbils infected with the high concentration of Y. pestis fluid show shorter duration in producing F1-antibody, the antibody positive rate is also higher, and the highest antibody titer can reach 1：4096. The great gerbils could hold the plague F1 antibodies for a long time which was about 140 to 200 days from the highest titer.