Confer Anthony W, Ayalew Sahlu
Department of Veterinary Pathobiology,Center for Veterinary Health Sciences, Oklahoma State University,McFarland & Farm Road, Stillwater, Oklahoma 74078-2007,USA.
Anim Health Res Rev. 2018 Dec;19(2):79-99. doi: 10.1017/S1466252318000142.
Mannheimia haemolytica is the major cause of severe pneumonia in bovine respiratory disease (BRD). Early M. haemolytica bacterins were either ineffective or even enhanced disease in vaccinated cattle, which led to studies of the bacterium's virulence factors and potential immunogens to determine ways to improve vaccines. Studies have focused on the capsule, lipopolysaccharide, various adhesins, extracellular enzymes, outer membrane proteins, and leukotoxin (LKT) resulting in a strong database for understanding immune responses to the bacterium and production of more efficacious vaccines. The importance of immunity to LKT and to surface antigens in stimulating immunity led to studies of individual native or recombinant antigens, bacterial extracts, live-attenuated or mutant organisms, culture supernatants, combined bacterin-toxoids, outer membrane vesicles, and bacterial ghosts. Efficacy of several of these potential vaccines can be shown following experimental M. haemolytica challenge; however, efficacy in field trials is harder to determine due to the complexity of factors and etiologic agents involved in naturally occurring BRD. Studies of potential vaccines have led current commercial vaccines, which are composed primarily of culture supernatant, bacterin-toxoid, or live mutant bacteria. Several of those can be augmented experimentally by addition of recombinant LKT or outer membrane proteins.
溶血曼氏杆菌是牛呼吸道疾病（BRD）中严重肺炎的主要病因。早期的溶血曼氏杆菌菌苗对接种牛要么无效，甚至还会加重病情，这促使人们对该细菌的毒力因子和潜在免疫原进行研究，以确定改进疫苗的方法。研究重点集中在荚膜、脂多糖、各种黏附素、胞外酶、外膜蛋白和白细胞毒素（LKT）上，从而形成了一个强大的数据库，有助于理解对该细菌的免疫反应并生产更有效的疫苗。对LKT和表面抗原免疫在刺激免疫方面的重要性引发了对单个天然或重组抗原、细菌提取物、减毒活疫苗或突变生物体、培养上清液、联合菌苗-类毒素、外膜囊泡和细菌幽灵的研究。在实验性溶血曼氏杆菌攻击后，可以证明其中几种潜在疫苗的有效性；然而，由于自然发生的BRD所涉及的因素和病原体的复杂性，在田间试验中的有效性更难确定。对潜在疫苗的研究催生了目前的商业疫苗，这些疫苗主要由培养上清液、菌苗-类毒素或活的突变细菌组成。其中几种疫苗可以通过添加重组LKT或外膜蛋白在实验中得到增强。
