Is the genetic variability of Cathepsin B important in the pathogenesis of Blastocystis spp.?
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The potential role of Blastocystis as a pathogen is controversial because it is found in both symptomatic and asymptomatic carriers. Since Cathepsin B has been identified as a main virulence factor that contributes to the pathogenesis of this parasite, the purpose of this study was to analyze the genetic polymorphisms of cathepsin B from Blastocystis from patients with irritable bowel syndrome and from asymptomatic carriers. DNA from fecal samples of both groups, which were previously genotyped by 18S sequencing, was used to amplify a fragment of the cathepsin B gene. Phylogenetic reconstructions were performed and some genetic population indexes were obtained. Amplicons of 27 samples (15 cases, 10 controls, and two commercial ATCC strains) were obtained and analyzed. Phylogenetic reconstructions using nucleotides or inferred amino acid sequences did not separate between cases or controls or among subtypes. Regarding the values of genetic variability, we found that the haplotype and nucleotide diversity indexes of cathepsin B from cases and controls were similar to the values of 18S from controls. By contrast, 18S from cases showed low variability, suggesting that the genetic variability of cathepsin B was not related to the symptomatology of Blastocystis carriers. However, since no polymorphisms related to cases or controls were found, it is logical to assume that the potential damage caused by Blastocystis in situ may be due to unclear mechanisms of Cathepsin B regulation and expression that should be studied in future studies.
KeywordsBlastocystis spp. cathepsin B Subtypes Irritable bowel syndrome Genetic polymorphism Pathogenesis
The authors acknowledge Eduardo Lopez-Escamilla, Saul Cano-Colin, and William Arony Martinez-Flores for technical support.
This work was supported by Consejo Nacional de Ciencia y Tecnologia (CONACYT) grant CB-2011/168619. Nelly Raquel Gonzalez-Arenas is a doctoral student from Programa de Doctorado en Ciencias Biomedicas, Universidad Nacional Autonoma de Mexico (UNAM) and received fellowships 220301 and 25263 (CB-2011/168619) by CONACYT.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
Informed consent was obtained from all participants included in the study.
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