Parasites, Vectors and Vector-Borne Diseases, Agricultural Research Council-Onderstepoort Veterinary Institute, Onderstepoort 0110, South Africa.
Parasitology. 2011 May;138(6):766-79. doi: 10.1017/S0031182011000187. Epub 2011 Feb 25.
Sequence variation within the 18S SSU rRNA V4 hyper-variable region can affect the accuracy of real-time hybridization probe-based diagnostics for the detection of Theileria spp. infections. This is relevant for assays that use non-specific primers, such as the real-time hybridization assay for T. parva (Sibeko et al. 2008). To assess the effect of sequence variation on this test, the Theileria 18S gene from 62 buffalo and 49 cattle samples was cloned and ∼1000 clones sequenced. Twenty-six genotypes were detected which included known and novel genotypes for the T. buffeli, T. mutans, T. taurotragi and T. velifera clades. A novel genotype related to T. sp. (sable) was also detected in 1 bovine sample. Theileria genotypic diversity was higher in buffalo compared to cattle. Polymorphism within the T. parva hyper-variable region was confirmed by aberrant real-time melting peaks and supported by sequencing of the S5 ribosomal gene. Analysis of the S5 gene suggests that this gene can be a marker for species differentiation. T. parva, T. sp. (buffalo) and T. sp. (bougasvlei) remain the only genotypes amplified by the primer set of the hybridization assay. Therefore, the 18S sequence diversity observed does not seem to affect the current real-time hybridization assay for T. parva.
18S SSU rRNA V4 高变区的序列变异可能会影响基于实时杂交探针的检测 Theileria spp. 感染的准确性。对于使用非特异性引物的检测方法，这是相关的，例如用于 T. parva 的实时杂交检测（Sibeko 等人，2008 年）。为了评估序列变异对该检测的影响，从 62 头水牛和 49 头牛的样本中克隆了 Theileria 18S 基因，并对约 1000 个克隆进行了测序。检测到 26 种基因型，包括已知和新型的 T. buffeli、T. mutans、T. taurotragi 和 T. velifera 分支的基因型。还在 1 头牛样本中检测到与 T. sp.（sable）相关的新型基因型。水牛的 Theileria 基因型多样性高于牛。T. parva 高变区的多态性通过实时熔解峰的异常得到证实，并通过 S5 核糖体基因的测序得到支持。对 S5 基因的分析表明，该基因可以作为物种分化的标志。T. parva、T. sp.（水牛）和 T. sp.（bougasvlei）仍然是杂交检测引物组扩增的唯一基因型。因此，观察到的 18S 序列多样性似乎不会影响当前用于 T. parva 的实时杂交检测。
