Protection against Bordetella pertussis in mice in the absence of detectable circulating antibody: Implications for long-term immunity in children

Most vaccines used for humans work through humoral immunity, yet many appea r to be protective even after specific circulating antibody levels have wan ed to undetectable levels. Furthermore, it has been difficult to define a s erologic correlate of protection against a number of infectious diseases, i ncluding those caused by Bordetella pertussis. B. pertussis clearance in im munized mice has been shown to correlate with pertussis vaccine efficacy in children. This murine respiratory challenge model was used to demonstrate persistent vaccine-induced protection against B, per tussis in the absence of circulating antibody at the time of challenge. Whole-cell and acellular pertussis vaccines induced persistent memory T and B cells and anamnestic a ntibody responses after challenge. The findings suggest that immunologic me mory is more significant in protection than is the induction of immediate a ntibody responses and imply that vaccinated children still may be protected against disease following the disappearance of specific serum IgG.