Falghoush Azeza, Ku Pei-Shin, Brayton Kelly A
Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA 99164, USA.
College of Sciences, Sirte University, Sirte P.O. Box 674, Libya.
Vaccines (Basel). 2023 Sep 29;11(10):1544. doi: 10.3390/vaccines11101544.
Bovine anaplasmosis, caused by , is the most prevalent tick-transmitted pathogen of livestock globally. In many parts of the world, , a related organism, is used as a live blood-borne vaccine as it causes either no or only a mild clinical disease. does not prevent infection with but does prevent acute disease. is prohibited from being used in the U.S. due to the risk of transmitting emerging pathogens. Both of these organisms encode proteins known as major surface protein 2 (Msp2), which is the most immunodominant protein for the organism. Both organisms persist in their host by evading clearance, i.e., the adaptive immune response, by recombining the hypervariable region (HVR) of with pseudogene alleles. The study goal was to test whether the Msp2 HVRs encoded by are a sufficient source of immune stimulation to provide the clinical protection exhibited by the blood-borne vaccine. Calves were inoculated with recombinantly expressed HVRs. Control groups were inoculated with saponin or infected with the live vaccine and compared with the test group. A Western blot analysis demonstrated that the HVR immunizations and live vaccine stimulated an immune response. All animals in the study became infected upon challenge with -infected ticks. The saponin-immunized control group had a high PPE (5.4%) and larger drops in PCVs (14.6%). As expected, the -immunized animals were protected from acute disease with lower (0.6%) parasitemia and lower drops in PCV (8.6%). The HVR-immunized group had intermediate results that were not statistically significantly different from either the negative or positive controls. This suggests that the HVR immunogen does not fully recapitulate the protective capacity of the live vaccine.
牛无形体病由[病原体名称未给出]引起，是全球最普遍的蜱传播家畜病原体。在世界许多地区，[相关病原体名称未给出]，一种相关生物体，被用作活的血源疫苗，因为它要么不引起临床疾病，要么只引起轻微临床疾病。[相关病原体名称未给出]不能预防[主要病原体名称未给出]感染，但能预防急性疾病。由于存在传播新出现病原体的风险，[相关病原体名称未给出]在美国被禁止使用。这两种生物体都编码一种称为主要表面蛋白2（Msp2）的蛋白质，它是该生物体最具免疫优势的蛋白质。这两种生物体都通过将[主要病原体名称未给出]的高变区（HVR）与假基因等位基因重组来逃避清除，即适应性免疫反应，从而在宿主体内持续存在。该研究的目标是测试[主要病原体名称未给出]编码的Msp2 HVRs是否是足够的免疫刺激源，以提供血源疫苗所表现出的临床保护。给小牛接种重组表达的[主要病原体名称未给出]HVRs。对照组接种皂苷或感染[相关病原体名称未给出]活疫苗，并与试验组进行比较。蛋白质免疫印迹分析表明，HVR免疫和[相关病原体名称未给出]活疫苗刺激了免疫反应。研究中的所有动物在用感染[主要病原体名称未给出]的蜱进行攻击后均被感染。皂苷免疫对照组的保护效果评估值（PPE）较高（5.4%），血细胞比容（PCV）下降幅度较大（14.6%）。正如预期的那样，[相关病原体名称未给出]免疫的动物免受急性疾病的侵害，寄生虫血症较低（0.6%），PCV下降幅度较低（8.6%）。HVR免疫组的结果处于中间水平，与阴性或阳性对照组相比无统计学显著差异。这表明HVR免疫原不能完全重现活疫苗的保护能力。
