| According to the American scientists,the Fc receptor(FcRn)of the newborn has a vital role in providing protective maternal source antibodies to the fetus and the newborn,and has the function of promoting local protective immunity.FcRn can also transfer the specific IgG and the antigen antibody complexes with the antigen to the lamina propria of the mucous membrane.After the uptake of the antigen presenting cell,then deliver to the T cell,causing the adaptive immune response of the body.In order to explore the immune effect of IgG FcRn mediated transfer of specific antigen,it is important for IgG to play an important role in the mucosal immunity of dairy cows.The molecular biological techniques were used to construct the recombinant plasmid pET-22-Fc-Sip of bovine IgG Fc and Streptococci agalactiae(S.agalactiae),an important surface antigen of Sip.The subunit vaccine Fc-Sip were prepared by prokaryotic expression and comply with adjuvants.On the basis of the study of Staphylococcus aureus in this laboratory,the Fc-FnBPB-ClfA subunit vaccine was prepared.Immunological tests were carried out on the patients who were about to get dry milk with the Streptococcus agalactiae Fc-Sip subunit vaccine,the Staphylococcus aureus Fc-FnBPB-ClfA subunit vaccine,the Fc-Sip and the Fc-FnBPB-ClfA bipartite subunit vaccine.The immunological characteristics of the three subunit vaccines were evaluated by the isolation of the milk samples'bacteria,the number of samples'somatic cell and the indirect ELISA method before and after immunization.The results showed that the isolation rate of milk samples'bacteria in the immune group of 0 d was 83.3%,of which the detection rate of Streptococcus lactis was 20%,the detection rate of Staphylococcus aureus was 23.3%;the isolation rate of milk samples'bacteria decreased to 26.6%after 90 d in the immune group,the detection rate of Streptococcus lactis decreased to 3.3%,and the detection rate of Staphylococcus aureus decreased to 6.6%.The results of the bacterial sorting before and after the immunization showed that the Fc-Sip subunit vaccine and the Fc-FnBPB-ClfA subunit vaccine not only have therapeutic effect on Streptococcus lactis type mastitis and Staphylococcus aureus type mastitis,but also inhibit other dairy cow mastitis pathogenic bacteria invade the mammary glands.On the 90th day after immunization,the number of milk somatic cell in all the measured dairy cows was detected by DeLaval milk somatic cell detector.The number of milk samples'somatic cell in the immune group was less than 3.3 x 10~5/mL,while the number of milk samples'somatic cell in the control group was more than 4 x 10~5/mL.The serum antibody titers of 0 day,7th day,14th day,28th day,60th day of immunization group and test group were monitored.The serum antibody titer of the control group remained the level of antibody at 1:256 and 1:512.7 days after the first immunization,80%cows of the serum antibody titers in the immune group reached 1:1024,and the serum antibody titer increased obviously after 40 days,and the antibody level of 90%dairy cows in the immune group reached 1:2048;after 28 days,the serum antibody of 80%cows in the immune group reached 1:4096 and 1:8192,and the antibody titer increased by3 to 4 compared with the control group.After 60 days,the serum antibody titers in each group showed a decreasing trend.The results of somatic cell count in milk and the results of antibody monitored showed that the subunit vaccine had the effect of reducing the number of somatic cells in milk.It also proved that the subunit vaccine promoted the occurrence of cow immune response.The A group in the immune group used the two subunit vaccine,which was tested on the cow was prepared by Fc-Sip and Fc-FnBPB-ClfA,and the overall immune effect was the best in all immune groups. |
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