Biology subjects

Leitner, D. R.

Publications and source records attributed to Leitner, D. R..

5 recordsLinked to original sources

bioRxiv2026

Antibody-recruiting molecules based on mimotope fusion peptides and a dimeric antibiotic

New therapeutic approaches are needed to treat infections due to multidrug resistant (MDR) Gram-negative bacteria. The use of antibody-recruiting molecules (ARMs) is a promising approach to address the MDR problem given their potential to engage both the adaptive and innate immune systems to treat bacterial infections. Here we present two new strategies to create ARMs. First, we show that a 9-mer antimicrobial peptide (K6) can be fused to a 11-mer mimotope peptide recognized by antibodies targeting the Vibrio cholerae O1 O-antigen to produce an ARM peptide (FZ5) that can render E. coli more sensitive to complement killing in the presence of antibodies that recognize this mimotope. FZ5 can drive killing by complement in the presence of rabbit antibodies raised against O1 serogroup V. cholerae as well as antibodies present in human sera elicited by immunization with the live attenuated cholera vaccine PanChol. We also describe a strategy that combines bacterial surface binding with hapten display through the use of homodimers of the antibiotic streptomycin (Str) and anti-Str antibodies elicited by Str-protein conjugate vaccines. When combined with dimeric Str derivatives and human complement, polyclonal anti-streptomycin antisera kills E. coli by targeting the Str hapten. Dimeric forms of Str also significantly enhanced killing of a Str-resistant P. aeruginosa clinical isolate dependent on low levels of human complement and polyclonal anti-Str antibody. Together these data suggest that anti-bacterial ARM molecules based on mimotope display through simple synthetic fusion peptides, or dimeric haptens have promise as new approaches for the treatment of MDR bacterial infections.

microbiology↗

bioRxiv2025

Vibrio cholerae serotype impacts pathogenicity

The O1 serogroup of Vibrio cholerae has caused all cholera pandemics and for over a century V. cholerae O1 outbreak strains have been characterized by their serotype. The two V. cholerae serotypes differ by the presence (Ogawa) or absence (Inaba) of methylation of the terminal sugar on the lipopolysaccharide O1-antigen. Serotype switching often occurs during epidemics and has historically been attributed to the pathogen adapting to immune pressures. Here we address the impact of serotype on V. cholerae pathogenicity using otherwise isogenic Ogawa and Inaba versions of several clinical V. cholerae O1 isolates. Our findings indicate that O1 antigen methylation in Ogawa strains promotes V. cholerae colonization, infectivity and resistance to antimicrobial peptides. We propose that methylation of the O1 antigen elevates colonization by shielding the bacterium from cationic antimicrobial peptides at the pH of the small intestine. These observations provide insights into the biological significance of the V. cholerae O1 serotypes.

microbiology↗

bioRxiv2024

The Mla pathway promotes Vibrio cholerae re-expansion from stationary phase

Bacteria have evolved diverse strategies to ensure survival under nutrient-limited conditions, where rapid energy generation is not achievable. Here, we performed a transposon insertion site sequencing loss-of-function screen to identify Vibrio cholerae genes that promote the pathogens fitness in stationary phase. We discovered that the Mla (maintenance of lipid asymmetry) pathway, which is crucial for transferring phospholipids from the outer to the inner membrane, is critical for stationary phase fitness. Competition experiments with barcoded and fluorophore labeled wild-type and mlaE mutant V. cholerae revealed that the Mla pathway promotes re-expansion from 48h stationary phase cultures. The mutants defect in transitioning out of stationary phase into active growth (culturability) was also observed in monocultures at 48h. However, by 96h the culturability of the mutant and wild-type strains were equivalent. By monitoring the abundances of genomically barcoded libraries of wild-type and {Delta}mlaE strains, we observed that a few barcodes dominated the mutant culture at 96h, suggesting that the similarity of the population sizes at this time was caused by expansion of a subpopulation containing a mutation that suppressed the mlaE mutants defect. Whole genome sequencing revealed that mlaE suppressors inactivated flagellar biosynthesis. Additional mechanistic studies support the idea that the Mla pathway is critical for the maintenance of V. choleraes culturability as it promotes energy homeostasis, likely due to its role in regulating outer membrane vesicle shedding. Together our findings provide insights into the cellular processes that control re-expansion from stationary phase and demonstrate a previously undiscovered role for the Mla pathway. ImportanceBacteria regularly encounter conditions with nutrient scarcity, where cell growth and division are minimal. Knowledge of the pathways that enable re-growth following nutrient restriction are limited. Here, using the cholera pathogen, we uncovered a role for the Mla pathway, a system that enables phospholipid re-cycling, in promoting Vibrio cholerae re-expansion from stationary phase cultures. Cells labeled with DNA barcodes or fluorophores were useful to demonstrate that though the abundances of wild-type and Mla mutant cells were similar in stationary phase cultures, they had marked differences in their capacities to regrow on plates. Of note, Mla mutant cells lose cell envelope components including high energy phospholipids due to OMV shedding. Our findings suggest that the defects in cellular energy homeostasis which emerge in the absence of the Mla pathway underlie its importance in maintaining V. cholerae culturability.

microbiology↗

bioRxiv2022

Reemergence of cholera in Haiti

Cholera was absent from Haiti until an inadvertent introduction by United Nations security forces in October 2010. The ensuing epidemic sickened 820,000 and caused 9,792 reported deaths1. The last cholera case in Haiti was recorded in January 2019, and in February 2022, Haiti was declared to have eliminated cholera2. In late September of 2022, a new outbreak began in Port-au-Prince and rapidly expanded to 964 suspected cases by mid-October of which 115 were confirmed by culture.3 Here, we present genomic and phenotypic analysis of the Vibrio cholerae isolated from a stool sample collected on September 30th, 2022 of an index case - a 10-year-old girl who presented with watery diarrhea and severe dehydration - to address the origins of the epidemic.

microbiology↗

bioRxiv2021

Non-toxigenic Vibrio cholerae challenge strains for evaluating vaccine efficacy and inferring mechanisms of protection

Human challenge studies are instrumental for testing cholera vaccines, but these studies use outdated strains and require inpatient facilities. Here, we created next-generation isogenic Ogawa and Inaba V. cholerae challenge strains (ZChol strains) derived from a contemporary Zambian clinical isolate representative of current dominant pandemic V. cholerae. To minimize the risk of severe diarrhea these strains were rendered non-toxigenic, since antibody responses which limit V. cholerae colonization are the primary mechanism of immune protection. These strains did not cause diarrhea in infant mice and proved to accurately gauge reduction in intestinal colonization mediated by effective vaccination. They are also valuable as targets for measuring vibriocidal antibody responses. Using barcoded ZChol strains, we discovered that vaccination tightens the infection bottleneck without restricting pathogen expansion in vivo. ZChol strains have the potential to enhance the safety, relevance, and scope of future cholera vaccine challenge studies and be valuable reagents for studies of immunity to cholera.

microbiology↗