Detecção de Escherichia coli enterotoxigênica por anticorpos anti-EtpA ligados a nanopartículas magnéticas

Abstract

Diarrheal diseases account for the second leading cause of death in children underfive years of age, below only pneumonia, killing about 760,000 children per year. The enterotoxigenic E. coli (ETEC) lineage is considered to be one of the most frequent causative agents of childhood diarrhea and travelers' diarrhea in low and middle-income countries. Among the virulence factors secreted by ETEC, the exoprotein EtpA has been described as an important protein that interacts with the highly conserved regions of the bacterial flagellum. These interactions are critical for adhesion, colonization, and delivery of toxins to enterocytes by ETEC. A new detection tool for enterotoxigenic E. coli bacteria was developed in the present work. Initially, the best antigenic sequence of the chimeric EtpA protein was determined by in silico prediction assays. After the construction of the recombinant antigen, we evaluated the production of anti-EtpA polyclonal antibodies in mice that were stimulated with this antigen. The mapping of epitopes using synthetic peptides demonstrated that only the 1.1 peptide was reactive to the pool of sera from the immunized animals. Specific recognition of anti-EtpA antibodies were assessed by flow cytometry. The results showed that the developed antibody was able to recognize the native EtpA protein. The evaluation of the specificity of anti-EtpA antibodies against different strains of diarrheogenic E. coli demonstrated the highest percentage and specificity for the ETEC strain (7.2%). The antibodies were then coupled into magnetic beads for the capture and detection of ETEC isolates. The results by cytometry showed high sensitivity, specificity and the efficacy of the method of separation and detection of these pathogens by magnetic beads bound to anti-EtpA antibodies.