马红球菌重组ABC转运蛋白的表达及其免疫效果评价OA

Rhodococcus equi(R.equi)is an intracellular parasitic bacterium that causes septic bronchopneumonia in foals,resulting in significant economic losses to the equine industry.Virulence-associated protein A(VapA)is a key virulence factor for R.equi,although studies have demonstrated that immunisation of animals with VapA has a pro-tective effect against R.equi infections,a commercial vaccine against R.equi has not yet been investigated.Bioinfor-matics analyses showed that the ABC transporter protein of R.equi could be a potential protective antigen against R.equi infection.In this study,recombinant ABC transporter protein(rABC)was prepared by prokaryotic expression,and BALB/c mice were immunised with rABC,recombinant VapA(rVapA,positive control)and PBS(negative con-trol)emulsified with Freund's adjuvant,respectively,to test their immunisation effects.The results showed that rABC with the expected molecular weight(62 kDa)and purified was obtained;specific antibodies began to be pro-duced 14 d after immunisation with rABC and rVapA;serum IgG antibody P/N values were≥15.0 at 42 d post-immunisation,IgG1 and IgG2a antibody potencies were 1∶409 600 and 1∶102 400,respectively,and the proportion of TNF-α-positive CD4+and CD8+T-cell in the spleen were significantly higher than those of the negative control group(P<0.05);7 d after infecting the bacteria,TNF-α and IL-6 secretion of splenocytes were significantly higher in rABC immunised group compared with those of the negative control group(P<0.05),and the histopathological changes in the lungs were attenuated.The results of this study suggest that ABC transporter proteins induce strong humoral and cellu-lar immune responses and attenuate lung pathological damage in mice,and are potential candidate antigens for R.equi subunit vaccine development.