O26 Polysaccharides as Key Players in Enteropathogenic E. coli Immune Evasion and Vaccine Development.

Enteropathogenic Escherichia coli (EPEC) produce a capsule of polysaccharides identical to those composing the O-antigen polysaccharide of its LPS (lipopolysaccharide) molecules. In light of this, the impact of O26 polysaccharides on the immune evasion mechanisms of capsulated O26 EPEC compared to non-capsulated enterohemorrhagic Escherichia coli (EHEC) was investigated. Our findings reveal that there was no significant difference between the levels in EPEC and EHEC of rhamnose (2.8:2.5), a molecule considered to be a PAMP (Pathogen Associated Molecular Patterns). However, the levels of glucose (10:1.69), heptose (3.6:0.89) and N-acetylglucosamine (4.5:2.10), were significantly higher in EPEC than EHEC, respectively. It was also observed that the presence of a capsule in EPEC inhibited the deposition of C3b on the bacterial surface and protected the pathogen against lysis by the complement system. In addition, the presence of a capsule also protected EPEC against phagocytosis by macrophages. However, the immune evasion provided by the capsule was overcome in the presence of anti-O26 polysaccharide antibodies, and additionally, these antibodies were able to inhibit O26 EPEC adhesion to human epithelial cells. Finally, the results indicate that O26 polysaccharides can generate an effective humoral immune response, making them promising antigens for the development of a vaccine against capsulated O26 E. coli.

O26 Polysaccharides as key players in enteropathogenic E. coli immune evasion and vaccine development

Enteropathogenic Escherichia coli (EPEC) produce a capsule of polysaccharides identical to those composing the O-antigen polysaccharide of its LPS (lipopolysaccharide) molecules. In light of this, the impact of O26 polysaccharides on the immune evasion mechanisms of capsulated O26 EPEC compared to non-capsulated enterohemorrhagic Escherichia coli (EHEC) was investigated. Our findings reveal that there was no significant difference between the levels in EPEC and EHEC of rhamnose (2.8:2.5), a molecule considered to be a PAMP (Pathogen Associated Molecular Patterns). However, the levels of glucose (10:1.69), heptose (3.6:0.89) and N-acetylglucosamine (4.5:2.10), were significantly higher in EPEC than EHEC, respectively. It was also observed that the presence of a capsule in EPEC inhibited the deposition of C3b on the bacterial surface and protected the pathogen against lysis by the complement system. In addition, the presence of a capsule also protected EPEC against phagocytosis by macrophages. However, the immune evasion provided by the capsule was overcome in the presence of anti-O26 polysaccharide antibodies, and additionally, these antibodies were able to inhibit O26 EPEC adhesion to human epithelial cells. Finally, the results indicate that O26 polysaccharides can generate an effective humoral immune response, making them promising antigens for the development of a vaccine against capsulated O26 E. coli.

O55 Polysaccharides Are Good Antigen Targets for the Formulation of Vaccines against O55 STEC and Capsulated aEPEC Strains.

The serogroup O55 of E. coli is composed of strains whose mechanisms of virulence are different from each other. Since the O55 polysaccharides are present in all E. coli O55 strains, and so are the polymers that compose the capsule of O55 atypical enteropathogenic E. coli (aEPEC), it was investigated whether anti-O55 antibodies were able to help the innate immune system to eliminate capsulated aEPEC and Shiga toxin-producing E. coli (STEC) belonging to the serogroup O55. The results demonstrate that the capsule of EPEC was able to inhibit the deposition of C3b on the bacterial surface and, as a consequence, their lysis by the alternative pathway of the complement system. However, in the presence of antibodies, the ability of the complement to lyse these pathogens was restored. It was also observed that macrophages were able to ingest EPEC and STEC, but they were only able to kill the ingested pathogens in the presence of antibodies. Anti-O55 antibodies were also able to inhibit aEPEC and STEC O55 adherence to human epithelial cells. In summary, the results demonstrated that the O55 polysaccharides have the potential to induce an effective humoral immune response against STEC and EPEC, indicating that they are good antigen targets to be used in vaccine formulations against these pathogens.

Open chromatin analysis in Trypanosoma cruzi life forms highlights critical differences in genomic compartments and developmental regulation at tDNA loci.

BACKGROUND: Genomic organization and gene expression regulation in trypanosomes are remarkable because protein-coding genes are organized into codirectional gene clusters with unrelated functions. Moreover, there is no dedicated promoter for each gene, resulting in polycistronic gene transcription, with posttranscriptional control playing a major role. Nonetheless, these parasites harbor epigenetic modifications at critical regulatory genome features that dynamically change among parasite stages, which are not fully understood. RESULTS: Here, we investigated the impact of chromatin changes in a scenario commanded by posttranscriptional control exploring the parasite Trypanosoma cruzi and its differentiation program using FAIRE-seq approach supported by transmission electron microscopy. We identified differences in T. cruzi genome compartments, putative transcriptional start regions, and virulence factors. In addition, we also detected a developmental chromatin regulation at tRNA loci (tDNA), which could be linked to the intense chromatin remodeling and/or the translation regulatory mechanism required for parasite differentiation. We further integrated the open chromatin profile with public transcriptomic and MNase-seq datasets. Strikingly, a positive correlation was observed between active chromatin and steady-state transcription levels. CONCLUSION: Taken together, our results indicate that chromatin changes reflect the unusual gene expression regulation of trypanosomes and the differences among parasite developmental stages, even in the context of a lack of canonical transcriptional control of protein-coding genes.

Escherichia coli Strains Responsible for Cystitis in Female Pediatric Patients with Normal and Abnormal Urinary Tracts Have Different Virulence Profiles.

The role of uropathogenic Escherichia coli (UPEC) in colonization and infection of female patients with anatomical and functional abnormalities of the urinary system is elusive. In this study, the phenotype, genotype and the phylogeny of UPEC strains isolated from the urine of pediatric female patients with cystitis of normal and abnormal urinary tract were determined. Multiplex PCR results demonstrated that 86% of the strains isolated from female patients with normal urinary tract (NUT), belonged to the phylo-groups B2 and D. Their prevalence decreased to 23% in strains isolated from patients with abnormal urinary tract (AUT). More of the isolates from AUT patients produced a biofilm on polystyrene and polyvinyl chloride (PVC), adhered to epithelial cells, and encoded pap and sfa genes than strains isolated from female patients with NUT. In contrast, a higher number of hemolysin-producing strains with serogroups associated with UPEC were isolated from patients with NUT. In summary, the results suggest that cystitis in female patients with NUT is associated with ExPEC, whereas cystitis in female patients with AUT is associated with pathogenic intestinal E. coli strains that have acquired the ability to colonize the bladder.

O55 polysaccharides are good antigen targets for the formulation of vaccines against O55 STEC and capsulated aEPEC strains

The serogroup O55 of E. coli is composed of strains whose mechanisms of virulence are different from each other. Since the O55 polysaccharides are present in all E. coli O55 strains, and so are the polymers that compose the capsule of O55 atypical enteropathogenic E. coli (aEPEC), it was investigated whether anti-O55 antibodies were able to help the innate immune system to eliminate capsulated aEPEC and Shiga toxin-producing E. coli (STEC) belonging to the serogroup O55. The results demonstrate that the capsule of EPEC was able to inhibit the deposition of C3b on the bacterial surface and, as a consequence, their lysis by the alternative pathway of the complement system. However, in the presence of antibodies, the ability of the complement to lyse these pathogens was restored. It was also observed that macrophages were able to ingest EPEC and STEC, but they were only able to kill the ingested pathogens in the presence of antibodies. Anti-O55 antibodies were also able to inhibit aEPEC and STEC O55 adherence to human epithelial cells. In summary, the results demonstrated that the O55 polysaccharides have the potential to induce an effective humoral immune response against STEC and EPEC, indicating that they are good antigen targets to be used in vaccine formulations against these pathogens.

Open chromatin analysis in Trypanosoma cruzi life forms highlights critical differences in genomic compartments and developmental regulation at tDNA loci

Background Genomic organization and gene expression regulation in trypanosomes are remarkable because protein-coding genes are organized into codirectional gene clusters with unrelated functions. Moreover, there is no dedicated promoter for each gene, resulting in polycistronic gene transcription, with posttranscriptional control playing a major role. Nonetheless, these parasites harbor epigenetic modifications at critical regulatory genome features that dynamically change among parasite stages, which are not fully understood. Results Here, we investigated the impact of chromatin changes in a scenario commanded by posttranscriptional control exploring the parasite Trypanosoma cruzi and its differentiation program using FAIRE-seq approach supported by transmission electron microscopy. We identified differences in T. cruzi genome compartments, putative transcriptional start regions, and virulence factors. In addition, we also detected a developmental chromatin regulation at tRNA loci (tDNA), which could be linked to the intense chromatin remodeling and/or the translation regulatory mechanism required for parasite differentiation. We further integrated the open chromatin profile with public transcriptomic and MNase-seq datasets. Strikingly, a positive correlation was observed between active chromatin and steady-state transcription levels. Conclusion Taken together, our results indicate that chromatin changes reflect the unusual gene expression regulation of trypanosomes and the differences among parasite developmental stages, even in the context of a lack of canonical transcriptional control of protein-coding genes.