Brown W C, McElwain T F, Ruef B J, Suarez C E, Shkap V, Chitko-McKown C G, Tuo W, Rice-Ficht A C, Palmer G H
Department of Veterinary Pathiobiology, Texas A & M University, College Station 77843, USA.
Infect Immun. 1996 Aug;64(8):3341-50. doi: 10.1128/iai.64.8.3341-3350.1996.
The ability of rhoptry-associated protein 1 (RAP-1) of Babesia bovis and Babesia bigemina to confer partial protective immunity in cattle has stimulated interest in characterizing both B-cell and T-cell epitopes of these proteins. It was previously shown that B. bovis RAP-1 associates with the merozoite surface as well as rhoptries and expresses B-cell epitopes conserved among otherwise antigenically different B. bovis strains. An amino-terminal 307-amino-acid domain of the molecule that is highly conserved in the B. bigemina RAP-1 homolog did not contain cross-reactive B-cell epitopes. The studies reported here demonstrate that B. bovis RAP-1 is strongly immunogenic for T helper (Th) cells from B. bovis-immune cattle and that like B-cell epitopes, Th-cell epitopes are conserved in different B. bovis strains but not in B. bigemina RAP-1. Lymphocytes from cattle immune to challenge with the Mexico strain of B. bovis proliferated against recombinant B. bovis RAP-1 protein derived from the Mexico strain. T-cell lines established by stimulating lymphocytes with recombinant RAP-1 protein responded against B. bovis, but not B. bigemina, merozoites. T-cell lines established by repeated stimulation of lymphocytes with B. bovis membrane antigen proliferated strongly against RAP-1, demonstrating the immunodominant nature of this protein. RAP-1-specific CD4+ T cell clones recognized Mexico, Texas, Australia, and Israel strains of B. bovis but neither B. bigemina merozoites nor recombinant B. bigemina RAP- 1. Analysis of cytokine mRNA in RAP-1-specific Th cell clones revealed strong expression of gamma interferon but little or no expression of interleukin-2 (IL-2), IL-4, or IL-10. Gamma interferon production was confirmed by enzyme-linked imunosorbent assay. These results indicate the potential to use selected B. bovis RAP-1 peptides as immunogens to prime for strong, anamnestic, strain-cross-reactive type 1 immune responses upon exposure to B. bovis.
牛巴贝斯虫和双芽巴贝斯虫的棒状体相关蛋白1（RAP-1）在牛体内具有部分保护性免疫的能力，这激发了人们对鉴定这些蛋白的B细胞和T细胞表位的兴趣。先前研究表明，牛巴贝斯虫RAP-1与裂殖子表面以及棒状体相关，并且表达在抗原性不同的牛巴贝斯虫菌株中保守的B细胞表位。该分子的氨基末端307个氨基酸结构域在双芽巴贝斯虫RAP-1同源物中高度保守，但不包含交叉反应性B细胞表位。本文报道的研究表明，牛巴贝斯虫RAP-1对来自牛巴贝斯虫免疫牛的辅助性T（Th）细胞具有强烈免疫原性，并且与B细胞表位一样，Th细胞表位在不同的牛巴贝斯虫菌株中保守，但在双芽巴贝斯虫RAP-1中不保守。来自免疫牛的淋巴细胞在受到牛巴贝斯虫墨西哥株攻击后，会针对源自墨西哥株的重组牛巴贝斯虫RAP-1蛋白发生增殖。用重组RAP-1蛋白刺激淋巴细胞建立的T细胞系对牛巴贝斯虫裂殖子有反应，但对双芽巴贝斯虫裂殖子无反应。通过用牛巴贝斯虫膜抗原反复刺激淋巴细胞建立的T细胞系对RAP-1强烈增殖，证明了该蛋白的免疫显性性质。RAP-1特异性CD4 + T细胞克隆识别牛巴贝斯虫的墨西哥、得克萨斯、澳大利亚和以色列株，但不识别双芽巴贝斯虫裂殖子或重组双芽巴贝斯虫RAP-1。对RAP-1特异性Th细胞克隆中细胞因子mRNA的分析显示，γ干扰素强烈表达，但白细胞介素-2（IL-2）、IL-4或IL-10表达很少或不表达。通过酶联免疫吸附测定证实了γ干扰素的产生。这些结果表明，有可能使用选定的牛巴贝斯虫RAP-1肽作为免疫原，在接触牛巴贝斯虫时引发强烈的、记忆性的、菌株交叉反应性1型免疫反应。
