What risks should be permissible in controlled human infection model studies?

Streptococcus pneumoniae is the leading cause of morbidity and mortality due to community acquired pneumonia, bacterial meningitis and bacteraemia worldwide. Pneumococcal conjugate vaccines protect against invasive disease, but are expensive to manufacture, limited in serotype coverage, associated with serotype replacement and demonstrate reduced effectiveness against mucosal colonisation. As asymptomatic colonisation of the human nasopharynx is a prerequisite for pneumococcal disease, this is proposed as a marker for novel vaccine efficacy. Our team established a safe and reproducible pneumococcal controlled human infection model at Liverpool School of Tropical Medicine (LSTM). This has been used to test vaccine induced protection against nasopharyngeal carriage for ten years in over 1000 participants. We will transfer established standardised operating procedures from LSTM to Malawi and test in up to 36 healthy participants. Primary endpoint: detection of the inoculated pneumococci by classical culture from nasal wash recovered from the participants after pneumococcal challenge. Secondary endpoints: confirmation of robust clinical and laboratory methods for sample capture and processing. Tertiary endpoints: participant acceptability of study and methods. We will test three doses of pneumococcal inoculation (20,000, 80,000 and 160,000 colony forming units [CFUs] per naris) using a parsimonious study design intended to reduce unnecessary exposure to participants. We hypothesise that 80,000 CFUs will induce nasal colonisation in approximately half of participants per established LSTM practice. The aims of the feasibility study are: 1) Establish Streptococcus pneumoniae experimental human pneumococcal carriage in Malawi; 2) Confirm optimal nasopharyngeal pneumococcal challenge dose; 3) Confirm safety and measure potential symptoms; 4) Confirm sampling protocols and laboratory assays; 5) Assess feasibility and acceptability of consent and study procedures. Confirmation of pneumococcal controlled human infection model feasibility in Malawi will enable us to target pneumococcal vaccine candidates for an at-risk population who stand the most to gain from new and improved vaccine strategies.

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EnterotoxigenicE. colivirulence gene regulation in human infections

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1808982115 ◽

2018 ◽

Vol 115 (38) ◽

pp. E8968-E8976 ◽

Cited By ~ 15

Author(s):

Alexander A. Crofts ◽

Simone M. Giovanetti ◽

Erica J. Rubin ◽

Frédéric M. Poly ◽

Ramiro L. Gutiérrez ◽

...

Keyword(s):

Gene Expression ◽

Virulence Factor ◽

Virulence Gene ◽

Human Infection ◽

Anaerobic Growth ◽

Infection Model ◽

Low Oxygen ◽

Virulence Gene Expression ◽

Factor Expression

EnterotoxigenicEscherichia coli(ETEC) is a global diarrheal pathogen that utilizes adhesins and secreted enterotoxins to cause disease in mammalian hosts. Decades of research on virulence factor regulation in ETEC has revealed a variety of environmental factors that influence gene expression, including bile, pH, bicarbonate, osmolarity, and glucose. However, other hallmarks of the intestinal tract, such as low oxygen availability, have not been examined. Further, determining how ETEC integrates these signals in the complex host environment is challenging. To address this, we characterized ETEC’s response to the human host using samples from a controlled human infection model. We found ETEC senses environmental oxygen to globally influence virulence factor expression via the oxygen-sensitive transcriptional regulator fumarate and nitrate reduction (FNR) regulator. In vitro anaerobic growth replicates the in vivo virulence factor expression profile, and deletion offnrin ETEC strain H10407 results in a significant increase in expression of all classical virulence factors, including the colonization factor antigen I (CFA/I) adhesin operon and both heat-stable and heat-labile enterotoxins. These data depict a model of ETEC infection where FNR activity can globally influence virulence gene expression, and therefore proximity to the oxygenated zone bordering intestinal epithelial cells likely influences ETEC virulence gene expression in vivo. Outside of the host, ETEC biofilms are associated with seasonal ETEC epidemics, and we find FNR is a regulator of biofilm production. Together these data suggest FNR-dependent oxygen sensing in ETEC has implications for human infection inside and outside of the host.

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IgA and IgG1 Specific to Vi Polysaccharide of Salmonella Typhi Correlate With Protection Status in a Typhoid Fever Controlled Human Infection Model

Frontiers in Immunology ◽

10.3389/fimmu.2019.02582 ◽

2019 ◽

Vol 10 ◽

Cited By ~ 7

Author(s):

Lindsay C. Dahora ◽

Celina Jin ◽

Rachel L. Spreng ◽

Frederick Feely ◽

Ryan Mathura ◽

...

Keyword(s):

Typhoid Fever ◽

Salmonella Typhi ◽

Human Infection ◽

Infection Model

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The Background, Role and Approach for Development of a Controlled Human Infection Model for Nontyphoidal Salmonella

10.1007/82_2021_246 ◽

2021 ◽

Author(s):

Calman A. MacLennan

Keyword(s):

Human Infection ◽

Infection Model

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Consensus Report on Shigella Controlled Human Infection Model: Introduction and Overview

Clinical Infectious Diseases ◽

10.1093/cid/ciz886 ◽

2019 ◽

Vol 69 (Supplement_8) ◽

pp. S577-S579 ◽

Cited By ~ 1

Author(s):

Calman A MacLennan ◽

Anastazia Older Aguilar ◽

A Duncan Steele

Keyword(s):

Best Practices ◽

Vaccine Development ◽

Disease Process ◽

The United States ◽

Human Infection ◽

Infection Model ◽

Infectious Agents ◽

Vaccine Candidates ◽

Infection Models ◽

Consensus Report

Abstract In recent years, controlled human infection models (CHIMs) have become available for a range of infectious agents and have proved invaluable for understanding the disease process, pathogenesis, and mechanisms of immunity. CHIM studies have also contributed significantly to advancing development of a number of vaccines by providing an indication of vaccine efficacy. The Shigella CHIM has been established in 3 sites in the United States, and it is likely that the CHIM will play an important regulatory role for advancing the range of Shigella vaccine candidates that are currently in development. This supplement describes the harmonization of best practices across sites, with a view to maximizing the contribution that CHIM studies can make to Shigella vaccine development.

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Establishment of a Controlled Human Infection Model with a Lyophilized Strain of Shigella sonnei 53G

mSphere ◽

10.1128/msphere.00416-20 ◽

2020 ◽

Vol 5 (5) ◽

Cited By ~ 1

Author(s):

Robert W. Frenck ◽

Michelle Dickey ◽

Akamol E. Suvarnapunya ◽

Lakshmi Chandrasekaran ◽

Robert W. Kaminski ◽

...

Keyword(s):

Vaccine Development ◽

Human Infection ◽

Shigella Sonnei ◽

World Health ◽

Infection Model ◽

Sample Collection ◽

Open Label ◽

Content Type ◽

Infection Models ◽

Study Results

ABSTRACT Controlled human infection models (CHIMs) are useful for vaccine development. To improve on existing models, we developed a CHIM using a lyophilized preparation of Shigella sonnei strain 53G produced using current good manufacturing practice (cGMP). Healthy adults were enrolled in an open-label dose-ranging study. Following administration of a dose of rehydrated S. sonnei strain 53G, subjects were monitored for development of disease. The first cohort received 500 CFU of 53G, and dosing of subsequent cohorts was based on results from the previous cohort. Subjects were administered ciprofloxacin on day 5 and discharged home on day 8. Subjects returned as outpatients for clinical checks and sample collection. Attack rates increased as the dose of S. sonnei was increased. Among those receiving the highest dose (1,760 CFU), 70% developed moderate to severe diarrhea, 50% had dysentery, and 40% had fever. Antilipopolysaccharide responses were observed across all cohorts. An S. sonnei CHIM using a lyophilized lot of strain 53G was established. A dose in the range of 1,500 to 2,000 CFU of 53G was selected as the dose for future challenge studies using this product. This model will enable direct comparison of study results between institutions and ensure better consistency over time in the challenge inoculum. IMPORTANCE Controlled human infection models (CHIMs) are invaluable tools utilized to understand the human response to infection, potentially leading to protective immune mechanisms and allowing efficacy testing of enteric countermeasures, including vaccines, antibiotics, and other products. The development of an improved Shigella CHIM for both Shigella sonnei and Shigella flexneri is consistent with international efforts, supported by international donors and the World Health Organization, focused on standardizing Shigella CHIMs and using them to accelerate Shigella vaccine development. The use of lyophilized Shigella challenge strains rather than plate-grown inoculum preparations is considered an important step forward in the standardization process. Furthermore, the results of studies such as this justify the development of lyophilized preparations for additional epidemiologically important S. flexneri serotypes, including S. flexneri 3a and S. flexneri 6.

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Surface Properties and MC3T3-E1 Cell Response of Cortical Bone Allografts Modified with Low-Concentration Phosphoric Acid

Cellular Physiology and Biochemistry ◽

10.1159/000470823 ◽

2017 ◽

Vol 41 (4) ◽

pp. 1572-1583 ◽

Cited By ~ 3

Author(s):

Zengfa Huang ◽

Cheng Cheng ◽

Jing Wang ◽

Hui Wei ◽

Xianzhe Liu ◽

...

Keyword(s):

Contact Angle ◽

Phosphoric Acid ◽

Western Blotting ◽

Animal Experiments ◽

Biomechanical Properties ◽

Potential Method ◽

Infection Model ◽

Low Concentration ◽

Model Studies ◽

Bone Allografts

Background/Aims: This experimental study aimed to evaluate the effect of low-concentration phosphoric acid on the surface structure of cortical allografts. Methods: Allogenic cortical bones were obtained from femurs and tibias of New Zealand white rabbits. The bones were modified by treatment with various concentrations of phosphoric acid (10%, 20% or 30%) for 10, 30 or 60 minutes, then evaluated by the following methods: 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) and LIVE/DEAD assay, alkaline phosphatase (ALP) assay, biomechanical properties testing, contact angle detection, quantitative real-time polymerase chain reaction (Q-PCR), western blotting and scanning electron microscopy (SEM). Results: Compared with the other groups, the group modified with 10% H3PO4 for 10 minutes had lower cytotoxicity according to MTT and LIVE/DEAD assays, higher hydrophilicity in the contact angle detection test and greater stability in the biomechanical properties test. Moreover, an up-regulation of osteopontin (OPN) in bones modified with 10% H3PO4 was observed by Q-PCR and western blotting. In addition, ALP assay and SEM showed that surface porosity and osteoinductivity were increased in the group modified with 10% H3PO4. Conclusions: Low-concentration phosphoric acid may be a potential method for surface modification of cortical allografts. Further animal experiments and animal infection model studies are required to validate the efficacy of surface-modified cortical allografts to repair large segmental bone defects.

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The Virulence of S. marcescens Strains Isolated From Contaminated Blood Products Is Divergent in the C. elegans Infection Model

Frontiers in Genetics ◽

10.3389/fgene.2021.667062 ◽

2021 ◽

Vol 12 ◽

Author(s):

Alexander Diamandas ◽

Mikhail R. Razon ◽

Sandra Ramirez-Arcos ◽

Ann Karen C. Brassinga

Keyword(s):

Blood Donation ◽

Phylogenetic Analyses ◽

Bursaphelenchus Xylophilus ◽

Human Infection ◽

Genomic Diversity ◽

Multi Drug Resistance ◽

Clinical Strain ◽

Infection Model ◽

Pinewood Nematode ◽

Environmental Strain

Bacterial contamination of platelet concentrates (PCs) can occur during blood donation or PC processing, necessitating routine screening to identify contaminated products in efforts to prevent adverse transfusion reactions in recipient patients. Serratia marcescens is a common bacterial contaminant, and its resilient nature coupled with genetic promiscuity imbue this environmental bacterium with resistance to disinfectants and antibiotics enhancing bacterial virulence. In this study, we aim to understand adaptive survival mechanisms through genetic characterization of two S. marcescens strains, CBS11 and CBS12, isolated from PCs by Canadian Blood Services. Genomic analyses of the two strains indicated that CBS11 has one chromosome and one plasmid (pAM01), whereas CBS12 has no plasmids. Phylogenetic analyses show that CBS11 and CBS12 are non-clonal strains, with CBS11 clustering closely with clinical strain CAV1492 and less so with environmental strain PWN146, and CBS12 clustering with a clinical strain AR_0027. Interestingly, pAM01 was most closely related to PWN146p1, a plasmid found in S. marcescens PWN146 strain associated with pinewood nematode Bursaphelenchus xylophilus. Lastly, the genomic diversity of CBS11 and CBS12 was not reflected in the antibiotic resistance profiles as they were remarkably similar to one another, but was reflected in the virulence phenotypes assessed in the Caenorhabditis elegans nematode infection model, with CBS11 being more virulent then CBS12. Taken together, we suggest that S. marcescens environmental isolates that feature evolutionary diverse genomics are better equipped to adapt and thrive in varied environments, such as that of PCs, and therefore is as much of a concern as multi-drug resistance for human infection potential.

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