坦桑尼亚牛和水牛源小泰勒虫 CD8+ 抗原的多样性。

Diversity of two Theileria parva CD8+ antigens in cattle and buffalo-derived parasites in Tanzania.

机构信息

Department of Animal, Aquaculture and Range Sciences, College of Agriculture, Sokoine University of Agriculture P.O. Box 3004, Morogoro, Tanzania; Department of Disease Control, School of Veterinary Medicine, University of Zambia, P.O. Box 32379, Lusaka, Zambia.

Department of Animal, Aquaculture and Range Sciences, College of Agriculture, Sokoine University of Agriculture P.O. Box 3004, Morogoro, Tanzania.

出版信息

Ticks Tick Borne Dis. 2019 Aug;10(5):1003-1017. doi: 10.1016/j.ttbdis.2019.05.007. Epub 2019 May 22.

DOI:10.1016/j.ttbdis.2019.05.007

PMID:31151920

Abstract

Theileria parva is a tick-transmitted protozoan parasite that causes a disease called East Coast fever (ECF) in cattle. This important tick borne-disease (TBD) causes significant economic losses in cattle in many sub-Saharan countries, including Tanzania. Cattle immunization using Muguga cocktail has been recommended as an effective method for controlling ECF in pastoral farming systems in Tanzania. However, immunity provided through immunization is partially strain-specific. Therefore, the control of ECF in Tanzania is still a challenge due to inadequate epidemiological information. This study was conducted to assess genetic diversity of Tp1 and Tp2 genes from T. parva isolates that are recognized by CD8 + T-cells in cattle and buffalo. The Tp1 and Tp2 genes are currently under evaluation as candidates for inclusion in a subunit vaccine. A total of 130 blood samples collected from cattle which do not interact with buffalo (98), cattle co-grazing with buffalo (19) and buffalo (13) in Mara, Mbeya, Morogoro, Tanga, and Coast regions in Tanzania were used in this study. Genomic DNA was extracted from the blood samples, Tp1 and Tp2 genes were amplified using nested PCR and the PCR products were purified and sequenced. The partial sequencing of the Tp1 and Tp2 genes from T. parva isolates exhibited polymorphisms in both loci, including the epitope-containing regions. Results for sequence analysis showed that the overall nucleotide polymorphism (π) was 0.7% and 13.5% for Tp1 and Tp2, respectively. The Tajima's D and Fu's Fs test showed a negative value for both Tp1 and Tp2 genes, indicating deviations from neutrality due to a recent population expansion. The study further revealed a low to high level of genetic differentiations between populations and high genetic variability within populations. The study also revealed that most samples from the seven populations possessed several epitopes in antigens that were identical to those in the T. parva Muguga reference stock, which is the main component of the widely used live vaccine cocktail. Therefore, different strategic planning and cost-effective control measures should be implemented in order to reduce losses caused by ECF in the study areas.

摘要

小泰勒虫是一种通过蜱传播的原生动物寄生虫，会导致牛的东海岸热（ECF）疾病。这种重要的蜱传疾病（TBD）在包括坦桑尼亚在内的许多撒哈拉以南非洲国家的牛群中造成了重大经济损失。在坦桑尼亚的牧场系统中，使用 Muguga 鸡尾酒对牛进行免疫接种已被推荐为控制 ECF 的有效方法。然而，通过免疫接种提供的免疫力部分具有菌株特异性。因此，由于缺乏流行病学信息，坦桑尼亚的 ECF 控制仍然是一个挑战。本研究旨在评估被牛 CD8+T 细胞识别的 T. parva 分离株的 Tp1 和 Tp2 基因的遗传多样性。Tp1 和 Tp2 基因目前正在作为候选疫苗亚单位进行评估。从坦桑尼亚的 Mara、Mbeya、Morogoro、Tanga 和 Coast 地区的不与水牛接触的牛（98 只）、与水牛混养的牛（19 只）和水牛（13 只）中采集了 130 份血液样本用于本研究。从血液样本中提取基因组 DNA，使用巢式 PCR 扩增 Tp1 和 Tp2 基因，然后纯化和测序 PCR 产物。从 T. parva 分离株的 Tp1 和 Tp2 基因的部分测序显示，两个基因座均存在多态性，包括表位所在区域。序列分析结果表明，Tp1 和 Tp2 的核苷酸总多态性（π）分别为 0.7%和 13.5%。Tp1 和 Tp2 基因的 Tajima's D 和 Fu's Fs 检验均显示负值，表明由于近期种群扩张，存在偏离中性的情况。研究进一步揭示了种群之间的遗传分化程度从低到高，以及种群内的高遗传变异性。研究还表明，来自七个种群的大多数样本在抗原中都具有与 Muguga 参考株相同的几个表位，Muguga 参考株是广泛使用的活疫苗鸡尾酒的主要成分。因此，应在不同地区实施不同的战略规划和具有成本效益的控制措施，以减少研究区域内 ECF 造成的损失。