Sanz M G, Villarino N, Ferreira-Oliveira A, Horohov D W
Maxwell H. Gluck Equine Research Center, Department of Veterinary Science, Kentucky,Lexington, KY 40546-009, United States.
Washington State University, College of Veterinary Medicine, Pullman, WA 99164-6610, United States.
Vet Immunol Immunopathol. 2015 Mar 15;164(1-2):10-5. doi: 10.1016/j.vetimm.2015.01.004. Epub 2015 Jan 18.
Rhodococcus equi is a common cause of pneumonia in young foals worldwide and has considerable economic effects on the global equine industry. Despite ongoing efforts, no vaccine is currently available to prevent rhodococaal pneumonia. This is due, in part, to an incomplete understanding of the protective immune response to this bacterium. While antibodies to VapA, a lipoprotein produced by virulent R. equi, are useful in differentiating antibody production in response to pathogenic versus non-pathogenic strains, the significance of the humoral response of foals to this lipoprotein remains poorly defined. The objectives of this study were to evaluate changes in VapA-specific IgG and IgG subclasses after exposure and infection of neonatal foals. Experimental foals included those challenged with R. equi at 1 (n=18), 2 (n=4) and 3 (n=6) weeks of age. Confirmed naturally infected (n=7) and not infected (n=3) foals were also included. All foals were bled 24h after birth and weekly thereafter for a period of 8 weeks. Antibody changes over time were evaluated. Following birth, VapA-specific IgGs significantly (p<0.05) decreased over time in all foals as a result of normal decay of passively transferred antibodies. Both VapA-specific IgGa and IgG(T) significantly increased (p<0.05) after experimental challenge, however, the rise in IgG(T) occurred earlier. Only a significant (p<0.05) increase in VapA-specific IgG(T) over time was seen after natural infection. Whether VapA-specific IgG(T) can be used to differentiate rhodococcal from other pneumonias requires further investigation under field conditions.
马红球菌是全球幼驹肺炎的常见病因，对全球养马业有相当大的经济影响。尽管一直在努力，但目前尚无预防马红球菌肺炎的疫苗。部分原因是对这种细菌的保护性免疫反应了解不全面。虽然针对由强毒马红球菌产生的一种脂蛋白VapA的抗体，有助于区分对致病菌株与非致病菌株的抗体产生情况，但幼驹对这种脂蛋白的体液反应的意义仍不清楚。本研究的目的是评估新生幼驹暴露和感染后VapA特异性IgG和IgG亚类的变化。实验幼驹包括在1周龄（n = 18）、2周龄（n = 4）和3周龄（n = 6）时用马红球菌攻击的幼驹。还包括确诊自然感染（n = 7）和未感染（n = 3）的幼驹。所有幼驹在出生后24小时采血，此后每周采血一次，持续8周。评估抗体随时间的变化。出生后，由于被动转移抗体的正常衰减，所有幼驹中VapA特异性IgG随时间显著（p<0.05）下降。实验攻击后，VapA特异性IgGa和IgG(T)均显著（p<0.05）增加，然而，IgG(T)的升高出现得更早。自然感染后，仅观察到VapA特异性IgG(T)随时间显著（p<0.05）增加。VapA特异性IgG(T)是否可用于区分马红球菌肺炎与其他肺炎，需要在野外条件下进一步研究。
