Biology subjects

Andre, A. C.

Publications and source records attributed to Andre, A. C..

2 recordsLinked to original sources

bioRxiv2023

SPATEs promote the survival of Shigella to the plasma complement system upon hemorrhage and bacteremia

Shigella spp. are the causative agents of shigellosis, which remains a leading cause of death in children under the age of five. Shigellosis is characterized by fever and results in hemorrhagic diarrhea; in more severe cases, Shigella bacteremia has been reported. These clinical features strongly suggest that Shigella survive exposure to plasma, although this has not yet been studied at the molecular level. In this report, we confirmed in a guinea pig model of shigellosis that local hemorrhages were induced by S. flexneri 5a and S. sonnei, and we demonstrated that Shigella reached mucosal CD31+/CD34+ blood vessels during the late stages of infection and further disseminated in the bloodstream. These results confirmed the exposure of Shigella to plasma components within the hemorrhagic colonic mucosa and in the bloodstream. We demonstrated that all the tested Shigella strains survived plasma exposure in vitro, and we showed that Serine Protease Autotransporters of Enterobacteriaceae (SPATEs) are essential for Shigella dissemination within the colonic mucosa. We have confirmed that SPATEs are expressed and secreted in poorly oxygenated environments encountered by Shigella from hypoxic foci of infection to the bloodstream. We further demonstrated that SPATEs promoted Shigella survival in plasma, by cleaving complement component 3 (C3), thereby impairing complement system activation. We have shown here that the ability of Shigella to survive plasma exposure is a key factor in its virulence, both within primary foci and systemically. Significance StatementIn this study we aimed to better understand the significance of the ability of Shigella to survive plasma exposure, as we observed that non-pathogenic E. coli rapidly lysed upon exposure. Indeed, we reported that Shigella was already exposed to plasma components within the colonic mucosa, as we reported in a guinea pig model of shigellosis that hemorrhages were induced, that were associated with local diffusion of plasma components in the infected colonic mucosa. Shigella was obviously exposed to plasma during bacteremia. The ability of Shigella to survive in plasma has not been previously reported. Here we have shown, first, that Shigella was able to divide and grow in the presence of human plasma, and second, we found that SPATEs played a central role in this process by impairing with the activation of the complement system.

microbiology↗

bioRxiv2020

The ascorbate-deficient guinea pig model of shigellosis allows the study of the entire Shigella life cycle

Shigella spp. are the causative agents of bacillary dysentery or shigellosis, mainly in children living in developing countries. The study of Shigella entire life cycle in vivo and the evaluation of vaccine candidates protection efficacy have been hampered by the lack of a suitable animal model of infection (1). None of the ones evaluated so far (mouse, rabbit, guinea pig) allows to recapitulate shigellosis symptoms upon Shigella oral challenge. Historical reports suggest that dysentery and scurvy are both metabolic diseases associated with ascorbate-deficiency. Mammals which are susceptible to Shigella infection (humans, non-human primates and guinea pigs) are the lonely ones which are unable to synthesize ascorbate. We optimized a low-ascorbate diet to induce moderate ascorbate-deficiency but not scurvy in guinea pigs (Ascplasma conc.=1.6 M vs 36 M with optimal ascorbate supply). We demonstrated that moderate ascorbate-deficiency increases shigellosis severity during extended period of time (up to 48h) with all strains tested (Shigella flexneri 5a and 2a, Shigella sonnei). At late time-points, a massive influx of neutrophils was observed both within the disrupted colonic mucosa and in the luminal compartment, although Shigella remains able to disseminate deep into the organ to reach the sub-mucosal layer and the bloodstream. This new model of shigellosis opens new doors for the study both of Shigella infection strategy and innate and adaptive immune responses to Shigella infection. It may be also of a great interest to study the virulence of other pathogen for which no suitable animal model of infection is available (Vibrio cholerae, Yersinia pestis, Mycobacterium tuberculosis or Campylobacter jejuni, among others). SignificanceThe study of Shigella virulence cycle in vivo has been hampered by the lack of a suitable animal model, which would allow the colonic mucosa infection upon oral challenge. Based on historical reports and physiological aspects, it was suggested that ascorbate-deficiency may stand as a new dysentery risk-factor. To test this hypothesis, we set up a new ascorbate-deficient guinea pig model and demonstrated for the first time that the Shigella infectious process occurred for extended period of time (up to 48h) and demonstrated that shigellosis severity was higher in ascorbate-deficient animal. Ascorbate-deficient guinea pig model of infection may be used to assess the virulence of other pathogens for which no suitable animal model of infection is still lacking.

microbiology↗