Laboratorio de Inmunología Experimental, Instituto Nacional de Pediatría, Insurgentes Sur 3700-C, Colonia Insurgentes-Cuicuilco, Delegación Coyoacán, C.P. 04530 Ciudad de México, Mexico; Programa de Doctorado en Ciencias de la Producción y de la Salud Animal, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Av. Universidad 3000, Circuito Exterior S/N Delegación Coyoacán, C.P. 04510 Ciudad Universitaria, Ciudad de México, Mexico.
Laboratorio de Inmunología Experimental, Instituto Nacional de Pediatría, Insurgentes Sur 3700-C, Colonia Insurgentes-Cuicuilco, Delegación Coyoacán, C.P. 04530 Ciudad de México, Mexico.
Int J Parasitol. 2020 Jan;50(1):85-90. doi: 10.1016/j.ijpara.2019.12.001. Epub 2019 Dec 19.
Genotyping of Toxoplasma gondii remains a relevant topic of study, since genotypes can be related to the presentation and severity of toxoplasmosis. To date, 292 restriction fragment length polymorphism genotypes have been described around the world. Serosurveys in southeastern Mexico have documented exposure in over 70% of people and certain animals. Recently, we have described new genotypes and mixed infections in feral cats from Quintana Roo. Thus, the aim of this study was to genotype T. gondii and to describe its genetic variability, from naturally infected stray dogs of Chiapas, which has different geographical and climatic conditions from those found at the Yucatan Peninsula and the other parts of the country. Eleven stray dogs were captured and bled to obtain DNA, and then they were euthanized to perform necropsies and to collect target tissues. Diagnosis of T. gondii was done by quantitative real-time PCR (qPCR) and endpoint PCR. Genotyping was carried out, amplifying 12 polymorphic markers and 15 microsatellites. Atypical SAG3 gene products were cloned and sequenced. All blood samples of dogs were positive to T. gondii DNA by PCR. Two isolates were obtained from pooled heart and diaphragm tissue of two dogs. Two complete PCR-RFLP genotypes were identified (type BrIII and #28). Four animals had mixed infections. A new RFLP atypical allele for the SAG3 marker was observed; cloning and sequencing analysis of this locus revealed mixed infection by a strain identical to GT1, and one type I × II intragenic recombinant. The microsatellite analysis revealed that both isolates are atypical. Thus, atypical new genotypes of T. gondii and mixed infections were found in dogs of Chiapas. The results found here and in genotyping studies in México suggest that the southeastern region favours wide genetic diversity of T. gondii and the possible presence of virulent genotypes such as those found in central and South America.
弓形虫基因分型仍然是一个相关的研究课题，因为基因型可能与弓形虫病的表现和严重程度有关。迄今为止，全世界已经描述了 292 种限制片段长度多态性基因型。在墨西哥东南部的血清学调查记录了超过 70%的人和某些动物的感染。最近，我们在金塔纳罗奥州的野生猫中描述了新的基因型和混合感染。因此，本研究的目的是对来自恰帕斯州的自然感染的流浪狗进行弓形虫基因分型，并描述其遗传变异性，恰帕斯州与尤卡坦半岛和该国其他地区的地理和气候条件不同。捕获了 11 只流浪狗并采集了血液以获得 DNA，然后对其进行安乐死以进行尸检并收集目标组织。通过定量实时 PCR(qPCR)和终点 PCR 进行 T. gondii 的诊断。通过扩增 12 个多态性标记和 15 个微卫星来进行基因分型。克隆和测序了异常的 SAG3 基因产物。所有狗的血液样本通过 PCR 均对 T. gondii DNA 呈阳性。从两只狗的心脏和膈肌组织中混合获得了两个分离株。鉴定出了两种完整的 PCR-RFLP 基因型（BrIII 型和#28 型）。四例动物发生了混合感染。观察到 SAG3 标记的新的非典型 RFLP 等位基因；对该基因座的克隆和测序分析显示，由与 GT1 相同的菌株和一个 I×II 种内重组引起的混合感染。微卫星分析表明两种分离株均为非典型。因此，恰帕斯州的狗中发现了新的非典型弓形虫基因型和混合感染。这里和墨西哥基因分型研究的结果表明，东南部地区有利于弓形虫的广泛遗传多样性，并且可能存在像在中美洲和南美洲发现的毒力基因型。
