Impaired long-term maintenance and function of Bordetella pertussis specific B cell memory

Frequent occurrence of whooping cough in vaccinated populations suggests limited duration of vaccine-induced immunological memory. To investigate peculiarities in B cell memory specific for pertussis antigens P.69 pertactin (P.69 Prn), pertussis toxin (Ptx) and filamentous hemagglutinin (FHA), we monitored the induction and maintenance of specific serum IgG, long-lived bone marrow (BM)-derived plasma cell (PC) and splenic memory B cell (Bmem) populations in a long-term preclinical vaccination model. Groups of BALB/c mice were primed and boosted (day 28) with a combined diphtheria (D), tetanus (T), acellular pertussis (aP) vaccine (DTaP) or whole cell pertussis (P) vaccine (DTP) and the immune status was followed over time. Levels of pertussis specific IgG, induced after primary and booster immunization, peaked at day 98 to decline thereafter. This was not paralleled by a decay, but rather an increase in BM resident specific PC, over time (>1 year). In contrast, splenic Bmem peaked after booster immunization to decline till background levels. Late recall of immunological memory more than 1 year after primary and booster vaccination, however, did reveal a rapid proliferative response of pre-existing Bmem but failed to evoke an anamnestic IgG response. A combination of waning P-antigen specific IgG production by PC and poor functions of the Bmem compartment such as self-maintenance and anamnestic IgG responses could be a hallmark of waning pertussis immunity. A better understanding of the mechanisms of limited immunological memory to pertussis may help to improve current vaccines.