Abstract
Cholera caused by V. choleraeO1 confers at least 3-10 years of protection against subsequent disease irrelevant of age, despite relatively rapid fall in antibody levels in peripheral blood, suggesting memory B cell responses may play an important role in protection. The V. choleraeO1 -specific polysaccharide (OSP) component of lipopolysaccharide (LPS) is responsible for serogroup specificity, and it is unclear if young children are capable of developing memory B cell responses against OSP, a T cell-independent antigen, following cholera. To address this, we assessed OSP-specific memory B cell responses in young children (2-5 years, n= 11), older children (6-17 years, n=21), and adults (18-55 years, n=28) with cholera caused by V. choleraeO1 in Dhaka, Bangladesh. We also assessed memory B cell responses against LPS and vibriocidal responses, and plasma antibody responses against OSP, LPS, and cholera toxin B subunit (CtxB; a T cell-dependent antigen) on days 2, 7, as well as 30, 90 and 180 after convalescence. In all age cohorts, vibriocidal responses and plasma OSP, LPS, and CtxB-specific responses peaked on day 7, and fell toward baseline over the follow-up period. In comparison, we were able to detect OSP memory B cell responses in all age cohorts of patients with detectable responses over baseline for 90-180 days. Our results suggest that OSP-specific memory B cell responses can occur following cholera, even in the youngest children, and may explain in part the age-independent induction of long-term immunity following naturally acquired disease.