Generation rules of anti-main structural protein antibodies induced by inactivated PRRSV antigen

We aimed to detect generation rules of PRRSV main structural proteins specific antibodies induced by inactivated PRRSV antigen.PRRSV strain Hn-3/06 was purified by differential centrifugation,inactivated with formaldehyde,and emulsified with equal amount of Freund's adjuvant.Total of 20 mice(7~8 weeks old) were randomly assigned to two groups(10 mice each group),and each mouse received 110 μg PRRSV antigen in Freund's adjuvant every time immunization.The group 1 was vaccinated once,while the group 2 was vaccinated twice,in 7 days interval.We collected serum weekly after vaccination,and detected PRRSV,GP5,M and N specific serum antibody titers by indirect ELISA.The results show that inactivated PRRSV antigen could induce PRRSV,GP5,M and N specific antibody in both experimental groups.Anti-PRRSV and N protein antibodies emergenced at 14 days post the primo vaccination,and the titers reached 1:1280 at 21 days,reached the highest level at 35 days post the primo immunization;anti-M protein antibodies appeared at 42 days post the primo vaccination,and the titers reached the highest level of 1∶160 at 49 days post the primo immunization;anti-GP5 protein antibodies appeared at 49 days post the primo vaccination and the antibody level was upgrading continuosly till 56 days,then the antibody titers reached 1∶80.Specific serum antibody titers of group 2 were totally slightly higher than those of group 2.Iindirect immunofluorescence focus inhibition test indicated that virus-neutralizing antibodies appeared in low amounts around 42 days post vaccination in group 1,while appeared between 35~49 days post the primo vaccination in group 2 and the antibody titers reached the highest level of 1∶2 at 42 days.In conclusion,the immunogenicity of PRRSV is weak and inactivated PRRSV antigen can not induce effective protection.