检测两种猪源链球菌抗体间接ELISA方法的筛选与应用

Application of indirect ELISA for the detection of antibodies against two strains of streptococci

目的建立检测马链球菌兽疫亚种(Streptococcus equisubsp zooepidemius,Sez)与猪链球菌2型(Streptococcus suistype 2,Ss2)抗体的间接ELISA方法。方法选用Sez与Ss2的全菌(WAC)、超声波抗原(UA)、英膜多糖(capsular polysaccha-ride,CPS)作为抗原,筛选最优的检测两种抗体间接ELISA方法。结果3种抗原检测60份免疫后的血清表明,Sez与Ss2的CPS抗体阳性率分别为98.3%、96.7%,WAC为91.7%、85%,UA均为88.3%,前者与后两者差异显著(P<0.05)。检测免疫前50份血清、免疫后156份血清、60份临床采集血样表明,10%猪免疫前呈现Sez与Ss2的CPS抗体阳性;免疫后CPS抗体阳性率均在90%以上,此结果与免疫保护率相一致;苏州与常州两个猪场的血清各30份,CPS抗体阳性率均在6.7%左右。结论CPS-ELISA方法具有较好的稳定性、特异性、灵敏性,此方法在诊断和流行病学调查方面有价值。

To establish a method to detect the antibodies against Streptococcus equi subsp zooepidemius （Sez） and Streptococcus suis, type 2 （Ss2）, the whol cells antigen, the ultrasonic antigens and the capsular polysaccharides （CPS）antigen of these two strain of streptococci were extracted and used as antigens in an indirect ELISA assay. The results of assay by using these three different types of antigens in the detection of antibodies against two strains of streptococci of 60 post-immunized sera indicated that the positive rates of antibodies against CPS antigen of Sez and Ss2 were 98.3 % and 96.7 % respectively, in which those by using the whole cell antigen and ultrasonic antigen were 91.7 % and 88.3 % respectively with significant difference among them. The results of detecting 50 sera before immunization, 156 sera after immunization and 60 sera of blood taken from clinics demonstrated that 10 % of pigs before immunization showed the presence of CPS antibodies against Sez and Ss2, but the positive rates of CPS antibodies rose up to more than 90 % with a significant consistence with the results obtained from the immune protection rate. Both the 30 sera specimens taken from Suzhou and Changzhou districts showed a positive rate of CPS antibodies around 6.7 % It is thus proved that the CPS-ELISA assay has advantage of higher sensitivity, specificity and stability and can be used for the diagnosis and surveillance of streptococcal infections in pigs.