Single-Cell Analysis of the Plasmablast Response to Vibrio cholerae Demonstrates Expansion of Cross-Reactive Memory B Cells

Abstract

We characterized the acute B cell response in adults with cholera by analyzing the repertoire, specificity, and functional characteristics of 138 monoclonal antibodies (MAbs) generated from single-cell-sorted plasmablasts. We found that the cholera-induced responses were characterized by high levels of somatic hypermutation and large clonal expansions. A majority of the expansions targeted cholera toxin (CT) or lipopolysaccharide (LPS). Using a novel proteomics approach, we were able to identify sialidase as another major antigen targeted by the antibody response to Vibrio cholerae infection. Antitoxin MAbs targeted both the A and B subunits, and most were also potent neutralizers of enterotoxigenic Escherichia coli heat-labile toxin. LPS-specific MAbs uniformly targeted the O-specific polysaccharide, with no detectable responses to either the core or the lipid moiety of LPS. Interestingly, the LPS-specific antibodies varied widely in serotype specificity and functional characteristics. One participant infected with the Ogawa serotype produced highly mutated LPS-specific antibodies that preferentially bound the previously circulating Inaba serotype. This demonstrates durable memory against a polysaccharide antigen presented at the mucosal surface and provides a mechanism for the long-term, partial heterotypic immunity seen following cholera.

The regulation of gut mucosal IgA B-cell responses: recent developments

“…35,86,189 These observations converge on the notion that activated B cells can re-utilize pre-existing GC in PP, which is central to explaining how gut IgA responses are synchronized and that even TI antigens will drive somatically mutated B-cell clones in the gut. 87 By contrast, in CD40-and T-cell-deficient mice IgA CSR can occur, but SHM is not observed in the IgV H -genes. 35,86 Hence, IgA CSR does not strictly require GC formations in PP, but can occur at a GL7 int stage, prior to GC maturation.…”

“…72 This theory is supported by studies by Pabst and co-workers who have found extensive mutations in the vast majority of IgA-genes from isolated LP cells of wild-type mice using next-generation sequencing. 12,86,87 Indeed, IgA B cells reactive to LPS, a T-cell-independent antigen, were mutated in humans. 87…”

“…12,86,87 Indeed, IgA B cells reactive to LPS, a T-cell-independent antigen, were mutated in humans. 87…”

Antibody-Based Correlates of Protection against Cholera: Analysis of a Challenge Study of a Cholera-Naive Population

“…CVD 103-HgR has been shown to induce the production of serum vibriocidal antibodies ( 2 ). Vibriocidal antibodies are complement-fixing bactericidal antibodies that are primarily directed against the O antigen moiety of the lipopolysaccharide (LPS) antigen ( 3 ), and an association between high titers of these antibodies and protection against cholera has been observed for populations living in areas where cholera is endemic ( 4 , 5 ). Since an effective cholera vaccine must engender a local immune response in the gut mucosa, the vibriocidal antibody titer in serum is considered to be only an indirect marker of an appropriate intestinal response to vaccination, and the vibriocidal response is viewed as a nonmechanistic correlate of protection.…”

Impact of Toxin-Specific Antibodies on the Adjuvanticity and Inflammatory Effects Induced by Parenterally Administered Escherichia coli heat-Labile Toxin

“…Such restriction may also apply to protein adjuvant, such as derivatives of LT and CT. Individuals naturally or deliberately challenged with ETEC or Vibrio cholera strains mount local and systemic antibody responses to LT [15][16][17][18]. Some reports demonstrate that the rate of seroconversion directed towards LT is high, ranging from 75% to 92% at the first infection and reaching about 50-60% under rechallenge [15,18,19].…”