The 2022 Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference: Summary of abstract-based presentations.

The global nonprofit organization PATH hosted the third Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference in Washington, DC, on November 29 to December 1, 2022. With a combination of plenary sessions and posters, keynote presentations, and breakout workshops, the 2022 VASE Conference featured key updates on research related to the development of vaccines against neglected diarrheal pathogens including Shigella, enterotoxigenic Escherichia coli (ETEC), Campylobacter, and Salmonella. The presentations and discussions highlighted the significant impact of these diarrheal pathogens, particularly on the health of infants and young children in low- and middle-income countries, reflecting the urgent need for the development and licensure of new enteric vaccines.

Genomic, transcriptomic, and phenotypic differences among archetype strains of serotypes 2a, 3a, and 6.

Given the genomic diversity between serotypes and the paucity of data to support serotype-specific phenotypic differences, we applied and functional analyses of archetype strains of 2457T (2a), J17B (3a), and CH060 (6). These archetype strains represent the three leading serotypes recommended for inclusion in multivalent vaccines. Characterizing the genomic and phenotypic variation among these clinically prevalent serotypes is an important step toward understanding serotype-specific host-pathogen interactions to optimize the efficacy of multivalent vaccines and therapeutics.

The role of the minor colonization factor CS14 in adherence to intestinal cell models by geographically diverse ETEC isolates.

Enterotoxigenic (ETEC) is a primary causative agent of diarrhea in travelers and young children in low- to middle-income countries. ETEC adheres to small intestinal epithelia via colonization factors (CFs) and secretes heat-stable toxin and/or heat-labile toxin, causing dysregulated ion transport and water secretion. There are over 30 CFs identified, including major CFs associated with moderate-to-severe diarrhea (MSD) and minor CFs for which a role in pathogenesis is less clear.

The role of CFA/I in adherence and toxin delivery by ETEC expressing multiple colonization factors in the human enteroid model.

Enterotoxigenic Escherichia coli (ETEC) is a primary causative agent of diarrhea in travelers and young children in low-to-middle-income countries (LMICs). ETEC adhere to intestinal epithelia via colonization factors (CFs) and secrete heat-stable toxin (ST) and/or heat-labile toxin (LT), causing dysregulated cellular ion transport and water secretion. ETEC isolates often harbor genes encoding more than one CF that are targets as vaccine antigens.

Pathogenomic analyses of Shigella isolates inform factors limiting shigellosis prevention and control across LMICs.

Shigella spp. are the leading bacterial cause of severe childhood diarrhoea in low- and middle-income countries (LMICs), are increasingly antimicrobial resistant and have no widely available licenced vaccine. We performed genomic analyses of 1,246 systematically collected shigellae sampled from seven countries in sub-Saharan Africa and South Asia as part of the Global Enteric Multicenter Study (GEMS) between 2007 and 2011, to inform control and identify factors that could limit the effectiveness of current approaches.

The O-Ag Antibody Response to Francisella Is Distinct in Rodents and Higher Animals and Can Serve as a Correlate of Protection.

Identifying correlates of protection (COPs) for vaccines against lethal human (Hu) pathogens, such as (), is problematic, as clinical trials are currently untenable and the relevance of various animal models can be controversial. Previously, Hu trials with the live vaccine strain (LVS) demonstrated ~80% vaccine efficacy against low dose (~50 CFU) challenge; however, protection deteriorated with higher challenge doses (~2000 CFU of SchuS4) and no COPs were established. Here, we describe our efforts to develop clinically relevant, humoral COPs applicable to high-dose, aerosol challenge with S4.

Sequence variations in the ETEC CS6 operon affect transcript and protein expression.

Enterotoxigenic (ETEC) is a leading cause of diarrheal disease in developing nations where it accounts for a significant disease burden in children between the ages of 0 to 59 months. It is also the number one bacterial causative agent of traveler's diarrhea. ETEC infects hosts through the fecal-oral route and utilizes colonization factors (CF) to adhere within the small intestine.

Evaluation of a Live Attenuated Vaccine Strain in the Human Enteroid Model.

is a leading cause of bacillary dysentery worldwide, responsible for high death rates especially among children under five in low-middle income countries. prevails in high-income countries and is becoming prevalent in industrializing countries, where multi-drug resistant strains have emerged, as a significant public health concern. One strategy to combat drug resistance in is the development of effective vaccines.

Deletion Mutants of Phagosomal Transporters FptA and FptF Are Highly Attenuated for Virulence and Are Protective Against Lethal Intranasal LVS Challenge in a Murine Model of Respiratory Tularemia.

() is a Gram-negative, facultative intracellular bacterium that is a Tier 1 Select Agent of concern for biodefense for which there is no licensed vaccine. A subfamily of 9 phagosomal transporter () genes belonging to the Major Facilitator Superfamily of transporters was identified as critical to pathogenesis and potential targets for attenuation and vaccine development. We evaluated the attenuation and protective capacity of LVS derivatives with deletions of the and genes in the C57BL/6J mouse model of respiratory tularemia.

Tick extracellular vesicles enable arthropod feeding and promote distinct outcomes of bacterial infection.

Extracellular vesicles are thought to facilitate pathogen transmission from arthropods to humans and other animals. Here, we reveal that pathogen spreading from arthropods to the mammalian host is multifaceted. Extracellular vesicles from Ixodes scapularis enable tick feeding and promote infection of the mildly virulent rickettsial agent Anaplasma phagocytophilum through the SNARE proteins Vamp33 and Synaptobrevin 2 and dendritic epidermal T cells.

Identification of an Attenuated Substrain of SCHU S4 by Phenotypic and Genotypic Analyses.

Pneumonic tularemia is a highly debilitating and potentially fatal disease caused by inhalation of Most of our current understanding of its pathogenesis is based on the highly virulent subsp. strain SCHU S4. However, multiple sources of SCHU S4 have been maintained and propagated independently over the years, potentially generating genetic variants with altered virulence.

Anti-CfaE nanobodies provide broad cross-protection against major pathogenic enterotoxigenic Escherichia coli strains, with implications for vaccine design.

Enterotoxigenic Escherichia coli (ETEC) is estimated to cause approximately 380,000 deaths annually during sporadic or epidemic outbreaks worldwide. Development of vaccines against ETEC is very challenging due to the vast heterogeneity of the ETEC strains. An effective vaccines would have to be multicomponent to provide coverage of over ten ETEC strains with genetic variabilities.

Research in a time of enteroids and organoids: how the human gut model has transformed the study of enteric bacterial pathogens.

Enteric bacterial pathogens cause significant morbidity and mortality globally. Studies in tissue culture and animal models shaped our initial understanding of these host-pathogen interactions. However, intrinsic shortcomings in these models limit their application, especially in translational applications like drug screening and vaccine development.

A bivalent vaccine confers immunogenicity and protection against and enterotoxigenic infections in mice.

Vaccine studies for and enterotoxigenic have been impaired by the lack of optimal animal models. We used two murine models to show that a 2a bivalent vaccine (CVD 1208S-122) expressing enterotoxigenic colonization factor antigen-I (CFA/I) and the binding subunits A2 and B of heat labile-enterotoxin (LTb) is immunogenic and protects against weight loss and diarrhea. These findings document the immunogenicity and pre-clinical efficacy effects of CVD 1208S-122 vaccine and suggest that further work can help elucidate relevant immune responses and ultimately its clinical efficacy in humans.

Characterization of Schu S4 mutants as live attenuated tularemia vaccine candidates.

There is a need for development of an effective vaccine against , as this potential bioweapon has a high mortality rate and low infectious dose when delivered via the aerosol route. Moreover, this Tier 1 agent has a history of weaponization. We engineered targeted mutations in the Type A strain subspecies Schu S4 in genes encoding critical enzymes in aromatic amino acid biosynthesis.

A new human challenge model for testing heat-stable toxin-based vaccine candidates for enterotoxigenic Escherichia coli diarrhea - dose optimization, clinical outcomes, and CD4+ T cell responses.

ClinicalTrials.gov ClinicalTrials.gov, Project ID: NCT02870751.

Vaccines Against Shigella and Enterotoxigenic Escherichia coli: A summary of the 2018 VASE Conference.

PATH hosted the second Vaccines Against Shigella and Enterotoxigenic Escherichia coli (VASE) Conference in Mexico City in June 2018, again providing experts from around the world an opportunity to participate in a highly collaborative forum to discuss progress in the development of new enteric vaccines. Through a combination of plenary sessions and posters, keynote presentations, and workshops, the 2018 VASE Conference aimed to accelerate communication and progress among those working to achieve the goal of licensed vaccines against these two bacterial pathogens. Many presentations recognized the importance of diarrheal disease and long-term sequelae caused by infections with Shigella and enterotoxigenic E.

Experimental Infection of Human Volunteers with the Heat-Stable Enterotoxin-Producing Enterotoxigenic Strain TW11681.

Infection with enterotoxigenic (ETEC) producing the heat-stable enterotoxin (ST) is one of the most important causes of childhood diarrhoea in low- and middle-income countries. Here, we undertook a controlled human infection model (CHIM) study to investigate whether ST-producing ETEC strain TW11681 would be suitable for testing the protective efficacy of new ST-based vaccine candidates in vaccine challenge models. In groups of three, nine volunteers ingested 1 × 10, 1 × 10, or 1 × 10 colony-forming units (CFU) of TW11681.

A tale of two bacterial enteropathogens and one multivalent vaccine.

Shigella and enterotoxigenic Escherichia coli (ETEC) are among the top four enteric pathogens that cause diarrheal illness in young children in developing countries and are major etiologic agents of travellers' diarrhoea. A single vaccine that could target both of these pathogens would have significant public health impact. In this review, we highlight the many pivotal contributions of Phillippe Sansonetti to the identification of molecular mechanisms of pathogenesis of Shigella that paved the way for the development of rationally designed, novel vaccines candidates.

Development, Characterization, and Standardization of a Nose-Only Inhalation Exposure System for Exposure of Rabbits to Small-Particle Aerosols Containing Francisella tularensis.

Inhalation of causes pneumonic tularemia in humans, a severe disease with a 30 to 60% mortality rate. The reproducible delivery of aerosolized virulent bacteria in relevant animal models is essential for evaluating medical countermeasures. Here we developed optimized protocols for infecting New Zealand White (NZW) rabbits with aerosols containing We evaluated the relative humidity, aerosol exposure technique, and bacterial culture conditions to optimize the spray factor (SF), a central metric of aerosolization.

Genome and Functional Characterization of Colonization Factor Antigen I- and CS6-Encoding Heat-Stable Enterotoxin-Only Enterotoxigenic Reveals Lineage and Geographic Variation.

Enterotoxigenic Escherichia coli (ETEC) is a significant cause of childhood diarrhea and is a leading cause of traveler's diarrhea. ETEC strains encoding the heat-stable enterotoxin (ST) are more often associated with childhood diarrhea than ETEC strains that encode only the heat-labile enterotoxin (LT). Colonization factors (CFs) also have a demonstrated role in ETEC virulence, and two of the most prevalent CFs among ETEC that have caused diarrhea are colonization factor antigen I (CFA/I) and CS6.

A roadmap for enterotoxigenic vaccine development based on volunteer challenge studies.

Enterotoxigenic (ETEC) is a major cause of travelers' diarrhea and of diarrhea among young children in developing countries. Experimental challenge studies in adult volunteers have played a pivotal role in establishing ETEC as an enteric pathogen, elucidating its pathogenesis by identifying specific virulence attributes, characterizing the human immune response to clinical and sub-clinical ETEC infection and assessing preliminarily the clinical acceptability, immunogenicity and efficacy of prototype ETEC vaccines. This review provides a historical perspective of experimental challenge studies with ETEC.

A murine model of diarrhea, growth impairment and metabolic disturbances with infection and the role of zinc deficiency.

is one of the major enteric pathogens worldwide. We present a murine model of infection and investigate the role of zinc deficiency (ZD). C57BL/6 mice fed either standard chow (HC) or ZD diets were pretreated with an antibiotic cocktail and received strain 2457T orally.

Evaluating Shigella flexneri Pathogenesis in the Human Enteroid Model.

The enteric pathogen is one of the leading causes of moderate-to-severe diarrhea and death in young children in developing countries. Transformed cell lines and animal models have been widely used to study pathogenesis. In addition to altered physiology, transformed cell lines are composed of a single cell type that does not sufficiently represent the complex multicellular environment of the human colon.