Characterization of Individual Human Antibodies That Bind Pertussis Toxin Stimulated by Acellular Immunization

Abstract

Despite high vaccination rates, the incidence of whooping cough has steadily been increasing in developing countries for several decades. The current acellular pertussis (aP) vaccines all include the major protective antigen pertussis toxin (PTx) and are safer, but they appear to be less protective than infection or older, whole-cell vaccines. To better understand the attributes of individual antibodies stimulated by aP, we isolated plasmablast clones recognizing PTx after booster immunization of two donors. Five unique antibody sequences recognizing native PTx were recovered and expressed as recombinant human IgG1 antibodies. The antibodies all bind different epitopes on the PTx S1 subunit, B oligomer, or S1-B subunit interface, and just one clone neutralized PTx in an in vitro assay. To better understand the epitopes bound by the nonneutralizing S1-subunit antibodies, comprehensive mutagenesis with yeast display provided a detailed map of the epitope recognized by antibodies A8 and E12. Residue R76 is required for antibody A8 binding and is present on the S1 surface but is only partially exposed in the holotoxin, providing a structural explanation for A8's inability to neutralize holotoxin. The B-subunit-specific antibody D8 inhibited PTx binding to a model receptor and neutralized PTx in vitro as well as in an in vivo leukocytosis assay. This is the first study, to our knowledge, to identify individual human antibodies stimulated by the acellular pertussis vaccine and demonstrates the feasibility of using these approaches to address outstanding issues in pertussis vaccinology, including mechanisms of accelerated waning of protective immunity despite repeated aP immunization.

Evaluation of Anti-PT Antibody Response after Pertussis Vaccination and Infection: The Importance of Both Quantity and Quality

“…Furthermore, the study by Acquaye-Seedah et al, found antibodies after ACVs from genetically distinct plasmablasts to 1B7, but those were not as potent to neutralize PT as the 1B7 reference Mab. Of interest, out of these clones, no clone was bound to the 11E6-like epitope [ 115 ].…”

Acellular Pertussis Vaccines Induce Anti-pertactin Bactericidal Antibodies Which Drives the Emergence of Pertactin-Negative Strains

“…In Denmark, a PTX one-component vaccine has been used to replace wP vaccines, which shows efficacy against the disease and is still in use ( Thierry-Carstensen et al, 2013 ). Antibodies directed against PTX neutralize the toxin ( Acquaye-Seedah et al, 2018 ) and are important in providing protection against disease. Despite high B. pertussis colonization following B. pertussis challenge, infant baboons born to mothers vaccinated with the PTX mono-component vaccine show no disease symptoms, compared to baboons born to unvaccinated mothers that have the disease ( Kapil et al, 2018 ).…”

Pertussis Toxin: A Key Component in Pertussis Vaccines?

“…Further characterization of T- and B-cell epitopes in PT, both from natural B. pertussis infections and vaccination, is needed to help better select PT-inactivation and stabilization methods, preserve potential protective vaccine epitopes, and better understand waning protective immunity to aP vaccination [91,92]. It is also important to consider adjuvants in vaccine formulations.…”