Prior exposure to B. pertussis shapes the mucosal antibody response to acellular pertussis booster vaccination

Antibody and B-cell Immune Responses Against Bordetella Pertussis Following Infection and Immunization

Neither immunization nor recovery from natural infection provides life-long protection against Bordetella pertussis. Replacement of a whole-cell pertussis (wP) vaccine with an acellular pertussis (aP) vaccine, mutations in B. pertussis strains, and better diagnostic techniques, contribute to resurgence of number of cases especially in young infants. Development of new immunization strategies relies on a comprehensive understanding of immune system responses to infection and immunization and how triggering these immune components would ensure protective immunity. In this review, we assess how B cells, and their secretory products, antibodies, respond to B. pertussis infection, current and novel vaccines and highlight similarities and differences in these responses. We first focus on antibody-mediated immunity. We discuss antibody (sub)classes, elaborate on antibody avidity, ability to neutralize pertussis toxin, and summarize different effector functions, i.e. ability to activate complement, promote phagocytosis and activate NK cells. We then discuss challenges and opportunities in studying B-cell immunity. We highlight shared and unique aspects of B-cell and plasma cell responses to infection and immunization, and discuss how responses to novel immunization strategies better resemble those triggered by a natural infection (i.e., by triggering responses in mucosa and production of IgA). With this comprehensive review, we aim to shed some new light on the role of B cells and antibodies in the pertussis immunity to guide new vaccine development.

Nasal vaccines for pertussis

Whooping cough, caused by Bordetella pertussis, is still a major cause of morbidity and mortality worldwide. Current acellular pertussis (aP) vaccines induce potent circulating IgG and prevent severe disease in children/adults and in infants born to vaccinated mothers. However, they do not prevent nasal infection, allowing asymptomatic transmission of B. pertussis. Studies in animal models have demonstrated that, unlike natural infection, immunization with aP vaccines fails to induce secretory immunoglobulin A (IgA) or interleukin-17 (IL-17)-secreting tissue-resident memory CD4 T (TRM) cells, required for sustained sterilizing immunity in the nasal mucosa. Live-attenuated vaccines or aP vaccines formulated with novel adjuvants that induce respiratory IgA and TRM cells, especially when delivered by the nasal route, are in development and have considerable promise as next-generation vaccines against pertussis.

T cell reactivity to Bordetella pertussis is highly diverse regardless of childhood vaccination

The incidence of whooping cough due to Bordetella pertussis (BP) infections has increased recently. It is believed that the shift from whole-cell pertussis (wP) vaccines to acellular pertussis (aP) vaccines may be contributing to this rise. While T cells are key in controlling and preventing disease, nearly all knowledge relates to antigens in aP vaccines. A whole-genome mapping of human BP-specific CD4+ T cell responses was performed in healthy vaccinated adults and revealed unexpected broad reactivity to hundreds of antigens. The overall pattern and magnitude of T cell responses to aP and non-aP vaccine antigens are similar regardless of childhood vaccination, suggesting that asymptomatic infections drive the pattern of T cell reactivity in adults. Lastly, lack of Th1/Th2 polarization to non-aP vaccine antigens suggests these antigens have the potential to counteract aP vaccination Th2 bias. These findings enhance our insights into human T cell responses to BP and identify potential targets for next-generation pertussis vaccines.

Genome-wide characterization of T cell responses to Bordetella pertussis reveals broad reactivity and similar polarization irrespective of childhood vaccination profiles

The incidence of whooping cough (pertussis), the respiratory disease caused by Bordetella pertussis (BP) has increased in recent years, and it is suspected that the switch from whole-cell pertussis (wP) to acellular pertussis (aP) vaccines may be a contributing factor to the rise in morbidity. While a growing body of evidence indicates that T cells play a role in the control and prevention of symptomatic disease, nearly all data on human BP-specific T cells is related to the four antigens contained in the aP vaccines, and data detailing T cell responses to additional non-aP antigens, are lacking. Here, we derived a full-genome map of human BP-specific CD4+ T cell responses using a high-throughput ex vivo Activation Induced Marker (AIM) assay, to screen a peptide library spanning over 3000 different BP ORFs. First, our data show that BP specific-CD4+ T cells are associated with a large and previously unrecognized breadth of responses, including hundreds of targets. Notably, fifteen distinct non-aP vaccine antigens were associated with reactivity comparable to that of the aP vaccine antigens. Second, the overall pattern and magnitude of CD4+ T cell reactivity to aP and non-aP vaccine antigens was similar regardless of aP vs wP childhood vaccination history, suggesting that the profile of T cell reactivity in adults is not driven by vaccination, but rather is likely driven by subsequent asymptomatic or sub-clinical infections. Finally, while aP vaccine responses were Th1/Th2 polarized as a function of childhood vaccination, CD4+ T cell responses to non-aP BP antigens vaccine responses were not, suggesting that these antigens could be used to avoid the Th2 bias associated with aP vaccination. Overall, these findings enhance our understanding of human T cell responses against BP and suggest potential targets for designing next-generation pertussis vaccines.

Prior exposure to B. pertussis shapes the mucosal antibody response to acellular pertussis booster vaccination

Bordetella pertussis (Bp), the causative agent of pertussis, continues to circulate despite widespread vaccination programs. An important question is whether and how (sub)clinical infections shape immune memory to Bp, particularly in populations primed with acellular pertussis vaccines (aP). Here, we examine the prevalence of mucosal antibodies against non-vaccine antigens in aP-primed children and adolescents of the BERT study (NCT03697798), using antibody binding to a Bp mutant strain lacking aP antigens (Bp_mut). Our study identifies increased levels of mucosal IgG and IgA binding to Bp_mut in older aP-primed individuals, suggesting different Bp exposure between aP-primed birth cohorts, in line with pertussis disease incidence data. To examine whether Bp exposure influences vaccination responses, we measured mucosal antibody responses to aP booster vaccination as a secondary study outcome. Although booster vaccination induces significant increases in mucosal antibodies to Bp in both cohorts, the older age group that had higher baseline antibodies to Bp_ mut shows increased persistence of antibodies after vaccination.