Immunology and Vaccines Laboratory. Facultad de Ciencias Naturales, Universidad Autónoma de Querétaro, Querétaro, Qro, Mexico.
U. S. Department of Agriculture, Animal Disease Research Unit, Agricultural Research Service, Pullman, WA, 99164, USA.
Parasitology. 2019 Nov;146(13):1646-1654. doi: 10.1017/S0031182019001161. Epub 2019 Sep 13.
Bovine babesiosis is the most important protozoan disease transmitted by ticks. In Plasmodium falciparum, another Apicomplexa protozoan, the interaction of rhoptry neck protein 2 (RON2) with apical membrane antigen-1 (AMA-1) has been described to have a key role in the invasion process. To date, RON2 has not been described in Babesia bigemina, the causal agent of bovine babesiosis in the Americas. In this work, we found a ron2 gene in the B. bigemina genome. RON2 encodes a protein that is 1351 amino acids long, has an identity of 64% (98% coverage) with RON2 of B. bovis and contains the CLAG domain, a conserved domain in Apicomplexa. B. bigemina ron2 is a single copy gene and it is transcribed and expressed in blood stages as determined by RT-PCR, Western blot, and confocal microscopy. Serum samples from B. bigemina-infected bovines were screened for the presence of RON2-specific antibodies, showing the recognition of conserved B-cell epitopes. Importantly, in vitro neutralization assays showed an inhibitory effect of RON2-specific antibodies on the red blood cell invasion by B. bigemina. Therefore, RON2 is a novel antigen in B. bigemina and contains conserved B-cell epitopes, which induce antibodies that inhibit merozoite invasion.
牛巴贝斯虫病是由蜱传播的最重要的原生动物病。在疟原虫（Plasmodium falciparum）中，另一种顶复门原生动物，已描述了罗氏蛋白颈 2（RON2）与顶膜抗原 1（AMA-1）的相互作用在入侵过程中起关键作用。迄今为止，在美洲引起牛巴贝斯虫病的巴贝斯虫（Babesia bigemina）中尚未描述 RON2。在这项工作中，我们在 B. bigemina 基因组中发现了一个 ron2 基因。RON2 编码一种 1351 个氨基酸长的蛋白质，与 B. bovis 的 RON2 具有 64%的同一性（98%的覆盖率），并包含 CLAG 结构域，这是顶复门的一个保守结构域。B. bigemina ron2 是一个单拷贝基因，如 RT-PCR、Western blot 和共聚焦显微镜所示，它在血液阶段转录和表达。从感染 B. bigemina 的牛的血清样本中筛选出 RON2 特异性抗体的存在，显示出对保守 B 细胞表位的识别。重要的是，体外中和试验表明 RON2 特异性抗体对 B. bigemina 入侵红细胞具有抑制作用。因此，RON2 是 B. bigemina 的一种新抗原，含有保守的 B 细胞表位，诱导的抗体可抑制裂殖体入侵。
