Salih Diaeldin A, Pelle Roger, Mwacharo Joram M, Njahira Moses N, Marcellino Wani L, Kiara Henry, Malak Agol K, El Hussein Abdel Rahim M, Bishop Richard, Skilton Robert A
Biosciences eastern and central Africa-International Livestock Research Institute Hub (BecA-ILRI Hub), Nairobi, Kenya.
Central Veterinary Research Laboratory, Khartoum, Sudan.
PLoS One. 2017 Feb 23;12(2):e0171426. doi: 10.1371/journal.pone.0171426. eCollection 2017.
East Coast fever (ECF), caused by Theileria parva infection, is a frequently fatal disease of cattle in eastern, central and southern Africa, and an emerging disease in South Sudan. Immunization using the infection and treatment method (ITM) is increasingly being used for control in countries affected by ECF, but not yet in South Sudan. It has been reported that CD8+ T-cell lymphocytes specific for parasitized cells play a central role in the immunity induced by ITM and a number of T. parva antigens recognized by parasite-specific CD8+ T-cells have been identified. In this study we determined the sequence diversity among two of these antigens, Tp1 and Tp2, which are under evaluation as candidates for inclusion in a sub-unit vaccine. T. parva samples (n = 81) obtained from cattle in four geographical regions of South Sudan were studied for sequence polymorphism in partial sequences of the Tp1 and Tp2 genes. Eight positions (1.97%) in Tp1 and 78 positions (15.48%) in Tp2 were shown to be polymorphic, giving rise to four and 14 antigen variants in Tp1 and Tp2, respectively. The overall nucleotide diversity in the Tp1 and Tp2 genes was π = 1.65% and π = 4.76%, respectively. The parasites were sampled from regions approximately 300 km apart, but there was limited evidence for genetic differentiation between populations. Analyses of the sequences revealed limited numbers of amino acid polymorphisms both overall and in residues within the mapped CD8+ T-cell epitopes. Although novel epitopes were identified in the samples from South Sudan, a large number of the samples harboured several epitopes in both antigens that were similar to those in the T. parva Muguga reference stock, which is a key component in the widely used live vaccine cocktail.
东海岸热(ECF)由小泰氏梨浆虫感染引起,是非洲东部、中部和南部牛群中一种常见的致命疾病,在南苏丹还是一种新出现的疾病。在受东海岸热影响的国家,越来越多地采用感染与治疗方法(ITM)进行免疫控制,但南苏丹尚未采用。据报道,针对被寄生细胞的CD8 + T细胞淋巴细胞在ITM诱导的免疫中起核心作用,并且已经鉴定出一些被寄生虫特异性CD8 + T细胞识别的小泰氏梨浆虫抗原。在本研究中,我们确定了其中两种抗原Tp1和Tp2的序列多样性,这两种抗原正在作为亚单位疫苗的候选成分进行评估。对从南苏丹四个地理区域的牛身上获得的小泰氏梨浆虫样本(n = 81)进行了Tp1和Tp2基因部分序列的序列多态性研究。结果显示,Tp1中有8个位置(1.97%)、Tp2中有78个位置(15.48%)具有多态性,分别在Tp1和Tp2中产生了4种和14种抗原变体。Tp1和Tp2基因的总体核苷酸多样性分别为π = 1.65%和π = 4.76%。这些寄生虫样本采自相距约300公里的区域,但群体间遗传分化的证据有限。序列分析表明,总体上以及在已定位的CD8 + T细胞表位内的残基中,氨基酸多态性数量有限。虽然在南苏丹的样本中鉴定出了新的表位,但大量样本在这两种抗原中都含有几个与广泛使用的活疫苗混合物中的关键成分小泰氏梨浆虫穆古加参考株相似的表位。