Cordon-Obras Carlos, Cano Jorge, González-Pacanowska Dolores, Benito Agustin, Navarro Miguel, Bart Jean-Mathieu
Instituto de Parasitología y Biomedicina "López-Neyra", CSIC, Consejo Superior de Investigaciones Científicas, Granada, Spain.
Centro Nacional de Medicina Tropical, Instituto de Salud Carlos III, Madrid, Spain.
PLoS One. 2013 Dec 23;8(12):e85072. doi: 10.1371/journal.pone.0085072. eCollection 2013.
Trypanosoma brucei gambiense infection is widely considered an anthroponosis, although it has also been found in wild and domestic animals. Thus, fauna could act as reservoir, constraining the elimination of the parasite in hypo-endemic foci. To better understand the possible maintenance of T. b. gambiense in local fauna and investigate the molecular mechanisms underlying adaptation, we generated adapted cells lines (ACLs) by in vitro culture of the parasites in different mammalian sera. Using specific antibodies against the Variant Surface Glycoproteins (VSGs) we found that serum ACLs exhibited different VSG variants when maintained in pig, goat or human sera. Although newly detected VSGs were independent of the sera used, the consistent appearance of different VSGs suggested remodelling of the co-transcribed genes at the telomeric Expression Site (VSG-ES). Thus, Expression Site Associated Genes (ESAGs) sequences were analysed to investigate possible polymorphism selection. ESAGs 6 and 7 genotypes, encoding the transferrin receptor (TfR), expressed in different ACLs were characterised. In addition, we quantified the ESAG6/7 mRNA levels and analysed transferrin (Tf) uptake. Interestingly, the best growth occurred in pig and human serum ACLs, which consistently exhibited a predominant ESAG7 genotype and higher Tf uptake than those obtained in calf and goat sera. We also detected an apparent selection of specific ESAG3 genotypes in the pig and human serum ACLs, suggesting that other ESAGs could be involved in the host adaptation processes. Altogether, these results suggest a model whereby VSG-ES remodelling allows the parasite to express a specific set of ESAGs to provide selective advantages in different hosts. Finally, pig serum ACLs display phenotypic adaptation parameters closely related to human serum ACLs but distinct to parasites grown in calf and goat sera. These results suggest a better suitability of swine to maintain T. b. gambiense infection supporting previous epidemiological results.
布氏冈比亚锥虫感染虽然也在野生动物和家畜中被发现，但广泛被认为是一种人兽共患病。因此，动物群可能充当储存宿主，限制了低流行地区寄生虫的消除。为了更好地理解布氏冈比亚锥虫在当地动物群中的可能维持情况，并研究其适应的分子机制，我们通过在不同哺乳动物血清中体外培养寄生虫，生成了适应性细胞系（ACL）。使用针对可变表面糖蛋白（VSG）的特异性抗体，我们发现血清ACL在猪、山羊或人血清中培养时表现出不同的VSG变体。虽然新检测到的VSG与所用血清无关，但不同VSG的一致出现表明端粒表达位点（VSG-ES）处共转录基因的重塑。因此，分析了表达位点相关基因（ESAG）序列，以研究可能的多态性选择。对在不同ACL中表达的编码转铁蛋白受体（TfR）的ESAG 6和7基因型进行了表征。此外，我们对ESAG6/7 mRNA水平进行了定量，并分析了转铁蛋白（Tf）摄取情况。有趣的是，在猪和人血清ACL中生长最好，它们始终表现出主要的ESAG7基因型，并且比在小牛和山羊血清中获得的ACL具有更高的Tf摄取。我们还在猪和人血清ACL中检测到特定ESAG3基因型的明显选择，表明其他ESAG可能参与宿主适应过程。总之，这些结果提出了一个模型，即VSG-ES重塑使寄生虫能够表达一组特定的ESAG，从而在不同宿主中提供选择优势。最后，猪血清ACL显示出与人类血清ACL密切相关但与在小牛和山羊血清中生长的寄生虫不同的表型适应参数。这些结果表明猪更适合维持布氏冈比亚锥虫感染，支持了先前的流行病学结果。
