Valadas Samantha Y O B, da Silva Juliana I G, Lopes Estela Gallucci, Keid Lara B, Zwarg Ticiana, de Oliveira Alice S, Sanches Thaís C, Joppert Adriana M, Pena Hilda F J, Oliveira Tricia M F S, Ferreira Helena L, Soares Rodrigo M
Department of Preventive Veterinary Medicine and Animal Health, University of São Paulo, São Paulo, SP, Brazil.
Department of Veterinary Medicine, University of São Paulo, SP, Brazil.
Exp Parasitol. 2016 May;164:71-8. doi: 10.1016/j.exppara.2016.02.008. Epub 2016 Feb 18.
Although few species of Sarcocystis are known to use marsupials of the genus Didelphis as definitive host, an extensive diversity of alleles of surface antigen genes (sag2, sag3, and sag4) has been described in samples of didelphid opossums in Brazil. In this work, we studied 25 samples of Sarcocystis derived from gastrointestinal tract of opossums of the genus Didelphis by accessing the variability of sag2, sag3, sag4, gene encoding cytochrome b (cytB) and first internal transcribed spacer (ITS1). Reference samples of Sarcocystis neurona (SN138) and Sarcocystis falcatula (SF1) maintained in cell culture were also analyzed. We found four allele variants of cytB, seven allele variants of ITS1, 10 allele variants of sag2, 13 allele variants of sag3, and 6 allele variants of sag4. None of the sporocyst-derived sequences obtained from Brazilian opossums revealed 100% identity to SN138 at cytB gene, nor to SN138 or SF1 at ITS1 locus. In addition, none of the sag alleles were found identical to either SF1 or SN138 homologous sequences, and a high number of new sag allele types were found other than those previously described in Brazil. Out of ten sag2 alleles, four are novel, while eight out of 13 sag3 alleles are novel and one out of six sag4 alleles is novel. Further studies are needed to clarify if such a vast repertoire of allele variants of Sarcocystis is the consequence of re-assortments driven by sexual exchange, in order to form individuals with highly diverse characteristics, such as pathogenicity, host spectrum, among others or if it only represents allele variants of different species with different biological traits.
虽然已知少数种类的肉孢子虫以袋鼬属有袋动物作为终末宿主，但在巴西的袋鼬样本中已发现表面抗原基因（sag2、sag3和sag4）的等位基因具有广泛的多样性。在这项研究中，我们通过分析sag2、sag3、sag4、细胞色素b（cytB）编码基因和第一内部转录间隔区（ITS1）的变异性，研究了25份源自袋鼬属有袋动物胃肠道的肉孢子虫样本。还分析了细胞培养中保存的肉孢子虫神经元虫（SN138）和肉孢子虫镰刀形虫（SF1）的参考样本。我们发现了cytB的4个等位基因变体、ITS1的7个等位基因变体、sag2的10个等位基因变体、sag3的13个等位基因变体和sag4的6个等位基因变体。从巴西有袋动物获得的所有子孢子衍生序列在cytB基因上与SN138的同源性均未达到100%，在ITS1位点上与SN138或SF1的同源性也未达到100%。此外，未发现任何sag等位基因与SF1或SN138的同源序列相同，并且发现了大量除巴西先前描述的以外的新sag等位基因类型。在10个sag2等位基因中，有4个是新的；在13个sag3等位基因中有8个是新的；在6个sag4等位基因中有1个是新的。需要进一步研究来阐明肉孢子虫如此大量的等位基因变体是由有性交换驱动的重排导致的结果，从而形成具有高度多样化特征（如致病性、宿主谱等）的个体，还是仅仅代表具有不同生物学特性的不同物种的等位基因变体。
