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Current mouse models for evaluating the efficacy of live oral cholera vaccines (OCVs) have important limitations. Conventionally raised adult mice are resistant to intestinal colonization by Vibrio cholerae , but germfree mice can be colonized and have been used to study OCV immunogenicity. However, germfree animals have impaired immune systems and intestinal physiology; also, live OCVs colonize germfree mice for many months, which does not mimic the clearance kinetics of live OCVs in humans. In this study, we leveraged antibiotic-treated, conventionally raised adult mice to study the effects of transient intestinal colonization by a live OCV V. cholerae strain. In a single-dose vaccination regimen, we found that HaitiV, a live-attenuated OCV candidate, was cleared by streptomycin-treated adult mice within 2 weeks after oral inoculation. This transient colonization elicited far stronger adaptive immune correlates of protection against cholera than did inactivated whole-cell HaitiV. Infant mice from HaitiV-vaccinated dams were also significantly more protected from choleric disease than pups from inactivated-HaitiV-vaccinated dams. Our findings establish the benefits of antibiotic-treated mice for live-OCV studies as well as their limitations and underscore the immunogenicity of HaitiV. IMPORTANCE Oral cholera vaccines (OCVs) are being deployed to combat cholera, but current killed OCVs require multiple doses and show little efficacy in young children. Live OCVs have the potential to overcome these limitations, but small-animal models for testing OCVs have shortcomings. We used an antibiotic treatment protocol for conventional adult mice to study the effects of short-term colonization by a single dose of HaitiV, a live-OCV candidate. Vaccinated mice developed vibriocidal antibodies against V. cholerae and delivered pups that were resistant to cholera, whereas mice vaccinated with inactivated HaitiV did not. These findings demonstrate HaitiV's immunogenicity and suggest that this antibiotic treatment protocol will be useful for evaluating the efficacy of live OCVs., (Copyright © 2020 American Society for Microbiology.)

Efficient acquisition of extracellular nutrients is essential for bacterial pathogenesis, however the identities and mechanisms for transport of many of these substrates remain unclear. Here, we investigate the predicted iron-binding transporter AfuABC and its role in bacterial pathogenesis in vivo. By crystallographic, biophysical and in vivo approaches, we show that AfuABC is in fact a cyclic hexose/heptose-phosphate transporter with high selectivity and specificity for a set of ubiquitous metabolites (glucose-6-phosphate, fructose-6-phosphate and sedoheptulose-7-phosphate). AfuABC is conserved across a wide range of bacterial genera, including the enteric pathogens EHEC O157:H7 and its murine-specific relative Citrobacter rodentium, where it lies adjacent to genes implicated in sugar sensing and acquisition. C. rodentium ΔafuA was significantly impaired in an in vivo murine competitive assay as well as its ability to transmit infection from an afflicted to a naïve murine host. Sugar-phosphates were present in normal and infected intestinal mucus and stool samples, indicating that these metabolites are available within the intestinal lumen for enteric bacteria to import during infection. Our study shows that AfuABC-dependent uptake of sugar-phosphates plays a critical role during enteric bacterial infection and uncovers previously unrecognized roles for these metabolites as important contributors to successful pathogenesis.

• Mammalian, non-mammalian, and invertebrate species are currently used to model Vibrio cholerae pathogenicity. • Models vary considerably in their recapitulation of V. cholerae- host interactions in the human intestine. • Recent work in animals has revealed molecular details of the host- V. cholerae -microbiome axis. • Open areas for investigation include intestinal innate defense against V. cholerae and determinants of cholera transmission. The human diarrheal disease cholera is caused by the bacterium Vibrio cholerae. Efforts to develop animal models that closely mimic cholera to study the pathogenesis of this disease began >125 years ago. Here, we review currently used non-surgical, oral inoculation-based animal models for investigation of V. cholerae intestinal colonization and disease and highlight recent discoveries that have illuminated mechanisms of cholera pathogenesis and immunity, particularly in the area of how V. cholerae interacts with the gut microbiome to influence infection. The emergence of high-throughput tools for studies of pathogen–host interactions, along with continued advances in host genetic engineering and manipulation in animal models of V. cholerae will deepen understanding of cholera pathogenesis, uncovering knowledge important for control of this globally important bacterial pathogen. [ABSTRACT FROM AUTHOR]