Circulating cholera antitoxin memory cells in the blood one year after oral cholera vaccination in humans

Oral vaccination with the combined B subunit/whole cell cholera vaccine generates antitoxin memory cells that could be isolated from peripheral blood for at least 1 year after immunization. These memory cells were triggered by antigen in vitro to produce antitoxin in the presence of autologous T cells and monocytes. Antitoxin-producing peripheral blood lymphocytes (PBL) were found in 4 out of 5 previously vaccinated subjects. IgA and IgM isotypes dominated the memory response. The antigen-dose dependency and requirements for a specific ratio of T to B cells for activation of the memory cells in vitro implies T-cell control of antitoxin responses. These antitoxin memory cells in peripheral blood (and corresponding antibacterial memory cells) might represent a pool of circulating cells that on renewed exposure to cholera rapidly produce protective antibody in the gut and thus might have a central role in the long-term protection against reinfection and disease seen in convalescents from cholera.