Cholera antibody production in vitro by peripheral blood lymphocytes following oral immunization of humans and mice.

We have studied specific antibody production from peripheral blood lymphocytes (PBL) after oral cholera immunization of humans and mice. Two oral immunizations with cholera toxin (CT) in mice or a single dose of the combined cholera B-subunit/whole cell vaccine in humans gave rise to PBL which spontaneously secreted cholera-specific antibodies when cultured in vitro. A high proportion of IgA antibodies was seen in contrast to antibodies produced by PBL after parenteral immunization which were predominantly IgG. Cultured PBL produced antitoxin as well as anti-lipopolysaccharide antibodies after oral immunization, whereas serum only revealed titre rises for anti-CT. Antibody-secreting PBL appeared in the blood 2-4 days after immunization and persisted for about two weeks with a peak after 6-8 days. Mitogen stimulation in vitro of PBL from multiply-orally vaccinated humans activated a population of specific IgM antibody-secreting cells which persisted for several months following immunization, suggesting the presence of long-lived memory cells. The analysis of IgA antibody production from in-vitro cultured PBL seems to be a promising technique to assess the local immunogenicity of oral vaccines.