Efficacy Evaluation of an Intradermally Delivered Enterotoxigenic Escherichia coli CF Antigen I Fimbrial Tip Adhesin Vaccine Coadministered with Heat-Labile Enterotoxin with LT(R192G) against Experimental Challenge with Enterotoxigenic E. coli H10407 in Healthy Adult Volunteers

Ramiro L Gutiérrez; Chad K Porter; Clayton Harro; Kawsar Talaat; Mark S Riddle; Barbara DeNearing; Jessica Brubaker; Milton Maciel Jr; Renee M Laird; Steven Poole; Subra Chakraborty; Nicole Maier; David A Sack; Stephen J Savarino

doi:10.3390/microorganisms12020288

Efficacy Evaluation of an Intradermally Delivered Enterotoxigenic Escherichia coli CF Antigen I Fimbrial Tip Adhesin Vaccine Coadministered with Heat-Labile Enterotoxin with LT(R192G) against Experimental Challenge with Enterotoxigenic E. coli H10407 in Healthy Adult Volunteers

Microorganisms. 2024 Jan 29;12(2):288. doi: 10.3390/microorganisms12020288.

Authors

Ramiro L Gutiérrez¹, Chad K Porter¹, Clayton Harro², Kawsar Talaat², Mark S Riddle¹, Barbara DeNearing², Jessica Brubaker², Milton Maciel Jr^{1

3}, Renee M Laird^{1

3}, Steven Poole^{1

3}, Subra Chakraborty⁴, Nicole Maier⁵, David A Sack², Stephen J Savarino¹

Affiliations

¹ Naval Medical Research Command, Silver Spring, MD 20910, USA.
² Center for Immunization Research, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21224, USA.
³ Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD 20817, USA.
⁴ Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA.
⁵ PATH, Washington, DC 20001, USA.

Abstract

Background: Enterotoxigenic E. coli (ETEC) is a principal cause of diarrhea in travelers, deployed military personnel, and children living in low to middle-income countries. ETEC expresses a variety of virulence factors including colonization factors (CF) that facilitate adherence to the intestinal mucosa. We assessed the protective efficacy of a tip-localized subunit of CF antigen I (CFA/I), CfaE, delivered intradermally with the mutant E. coli heat-labile enterotoxin, LTR192G, in a controlled human infection model (CHIM).

Methods: Three cohorts of healthy adult subjects were enrolled and given three doses of 25 μg CfaE + 100 ng LTR192G vaccine intradermally at 3-week intervals. Approximately 28 days after the last vaccination, vaccinated and unvaccinated subjects were admitted as inpatients and challenged with approximately 2 × 10⁷ cfu of CFA/I+ ETEC strain H10407 following an overnight fast. Subjects were assessed for moderate-to-severe diarrhea for 5 days post-challenge.

Results: A total of 52 volunteers received all three vaccinations; 41 vaccinated and 43 unvaccinated subjects were challenged and assessed for moderate-to-severe diarrhea. Naïve attack rates varied from 45.5% to 64.7% across the cohorts yielding an overall efficacy estimate of 27.8% (95% confidence intervals: -7.5-51.6%). In addition to reducing moderate-severe diarrhea rates, the vaccine significantly reduced loose stool output and overall ETEC disease severity.

Conclusions: This is the first study to demonstrate protection against ETEC challenge after intradermal vaccination with an ETEC adhesin. Further examination of the challenge methodology is necessary to address the variability in naïve attack rate observed among the three cohorts in the present study.

Keywords: CfaE; H10407; LTR192G antigen/adjuvant; efficacy; enterotoxigenic E. coli; intradermal; vaccine.

Grants and funding

This work is supported by funds from the Military Infectious Diseases Research Program and the Navy Advanced Development Program. It was also supported, in part, by the Bill and Melinda Gates Foundation (OPP1112376). Under the grant conditions of the Bill and Melinda Gates Foundation, a Creative Commons Attribution 4.0 Generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.