Publication: Trypanosoma brucei gambiense adaptation to different mammalian sera is associated with VSG expression site plasticity
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2013-12-23
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Cordon-Obras, Carlos ISCIII 
Ochando, Jordi ISCIII 
González-Pacanowska, Dolores
Benito, Agustin ISCIII
Navarro, Miguel
Bart, Jean-Mathieu
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Public Library of Science (PLOS)
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Abstract
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.
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Adaptation, Physiological Analysis of Variance Animals DNA Primers DNA, Complementary Disease Reservoirs Fluorescent Antibody Technique Genetic Variation Genotype Glycoproteins Goats Humans Mammals Membrane Glycoproteins Protozoan Proteins Reverse Transcriptase Polymerase Chain Reaction Serum Species Specificity Swine Transferrin Trypanosoma brucei gambiense
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Bibliographic citation
PLoS One. 2013 Dec 23;8(12):e85072.