O-Specific Polysaccharide Responses and Cholera

Cholera is a severe dehydrating illness of humans. It is endemic in over 50 countries and causes 3 to 5 million cases a year, resulting in approximately 100,000 deaths. Currently available cholera vaccines are poorly immunogenic in children under the age of 5 years, and often do not induce robust long-term memory responses in immunologically naïve populations. Antibodies targeting O-specific polysaccharide (OSP) are associated with protection against cholera. We here propose to extend our highly productive ongoing R37 international program that is defining OSP-specific immune responses in humans with cholera, including how OSP-specific antibodies protect. Such knowledge would be high impact and would directly inform cholera control efforts, including advancement of next generation cholera vaccines. In Aim #1, we will continue to define mechanisms of protection against V. cholerae afforded by OSP-specific responses using human isogenic OSP-specific monoclonal antibodies and human enteroid models. In Aim #2, we will define single cell and population responses at the mucosal surface in mucosal tissue samples obtained through endoscopic biopsy of cholera patients using single-nuclei sequencing (snRNA-seq) with T cell receptor (TCR) and B cell receptor (BCR) sequencing. In Aim #3, we will (a) define the OSP-specific response in intestinal tissue and luminal contents of patients recovering from cholera in Bangladesh, (b) deeply interrogate peripheral blood antigen-specific and functional immune responses using a system serology- based approach, and correlate these responses to responses directly assessed at the mucosal surface [in (3a)], and (c) assess the validity of whether such peripheral markers predict protection against cholera in our ongoing household contact study in Bangladesh. This extension builds upon our fully-approved and ongoing human, animal and bench-top studies, protocols and samplings, including at the International Centre for Diarrhoeal Disease Research-Bangladesh (icddr.b); no new additions are proposed. RELEVANCE (See instructions): Currently available oral cholera vaccines have a number of shortcomings. Developing improved vaccines or vaccination strategies is hampered by the reality that we do not currently understand the mechanism of immune protection against cholera although it is known that a primary component of that immunity targets O-specific polysaccharide (OSP) of V. cholerae. We here propose an investigative approach to define and evaluate OSP-specific responses during cholera.