Neutralizing antibodies to adenylate cyclase toxin promote phagocytosis ofBordetella pertussis by human neutrophils

A previous study showed that opsonization with human immune serum could eit her promote or antagonize phagocytosis of Bordetella pertussis by human neu trophils depending on whether the bacteria expressed adenylate cyclase toxi n. Opsonization of the wild-type strain inhibited phagocytosis relative to unopsonized controls. In contrast, mutants lacking adenylate cyclase toxin were efficiently phagocytosed when opsonized with human immune serum. In th is study, me examined opsonization in the presence or absence of monoclonal antibodies to adenylate cyclase toxin. Addition of neutralizing monoclonal antibodies to adenylate cyclase toxin converted a serum that previously in hibited both attachment and phagocytosis of the wild-type strain to one tha t increased both attachment and phagocytosis compared to the no-serum contr ol. Monoclonal antibodies that recognize the adenylate cyclase toxin but fa il to neutralize activity were without effect. These results suggest that a denylate cyclase toxin inhibits both Fc receptor-mediated attachment and ph agocytosis of B. pertussis by neutrophils.