The Use of Innovative Two-Component Cluster Analysis and Serodiagnostic Cut-Off Methods to Estimate Prevalence of Pertussis Reinfections

Superior B. pertussis Specific CD4+ T-Cell Immunity Imprinted by Natural Infection

Pertussis remains endemic in vaccinated populations due to waning of vaccine-induced immunity and insufficient interruption of transmission. Correlates of long-term protection against whooping cough remain elusive but increasing evidence from experimental models indicates that the priming of particular lineages of B. pertussis (Bp) specific CD4+ T cells is essential to control bacterial load. Critical hallmarks of these protective CD4+ T cell lineages in animals are suggested to be their differentiation profile as Th1 and Th17 cells and their tissue residency. These features seem optimally primed by previous infection but insufficiently or only partially by current vaccines. In this review, evidence is sought indicating whether infection also drives such superior Bp specific CD4+ T cell lineages in humans. We highlight key features of effector immunity downstream of Th1 and Th17 cell cytokines that explain clearing of primary Bp infections in naïve hosts, and effective prevention of infection in convalescent hosts during secondary challenge. Outstanding questions are put forward that need answers before correlates of human Bp infection-primed CD4+ T cell immunity can be used as benchmark for the development of improved pertussis vaccines.

Detection of opsonizing antibodies directed against a recently circulating Bordetella pertussis strain in paired plasma samples from symptomatic and recovered pertussis patients

Correlates of protection (CoPs) against the highly contagious respiratory disease whooping cough, caused by Bordetella pertussis, remain elusive. Characterizing the antibody response to this pathogen is essential towards identifying potential CoPs. Here, we evaluate levels, avidity and functionality of B. pertussis-specific-antibodies from paired plasma samples derived from symptomatic and recovered pertussis patients, as well as controls. Natural infection is expected to induce protective immunity. IgG levels and avidity to nine B. pertussis antigens were determined using a novel multiplex panel. Furthermore, opsonophagocytosis of a B. pertussis clinical isolate by neutrophils was measured. Findings indicate that following infection, B. pertussis-specific antibody levels of (ex-) pertussis patients waned, while the avidity of antibodies directed against the majority of studied antigens increased. Opsonophagocytosis indices decreased upon recovery, but remained higher than controls. Random forest analysis of all the data revealed that 28% of the opsonophagocytosis index variances could be explained by filamentous hemagglutinin- followed by pertussis toxin-specific antibodies. We propose to further explore which other B. pertussis-specific antibodies can better predict opsonophagocytosis. Moreover, other B. pertussis-specific antibody functions as well as the possible integration of these functions in combination with other immune cell properties should be evaluated towards the identification of CoPs against pertussis.

Impact of age and vaccination history on long-term serological responses after symptomatic B. pertussis infection, a high dimensional data analysis

Capturing the complexity and waning patterns of co-occurring immunoglobulin (Ig) responses after clinical B. pertussis infection may help understand how the human host gradually loses protection against whooping cough. We applied bi-exponential modelling to characterise and compare B. pertussis specific serological dynamics in a comprehensive database of IgG, IgG subclass and IgA responses to Ptx, FHA, Prn, Fim2/3 and OMV antigens of (ex-) symptomatic pertussis cases across all age groups. The decay model revealed that antigen type and age group were major factors determining differences in levels and kinetics of Ig (sub) classes. IgG-Ptx waned fastest in all age groups, while IgA to Ptx, FHA, Prn and Fim2/3 decreased fast in the younger but remained high in older (ex-) cases, indicating an age-effect. While IgG1 was the main IgG subclass in response to most antigens, IgG2 and IgG3 dominated the anti-OMV response. Moreover, vaccination history plays an important role in post-infection Ig responses, demonstrated by low responsiveness to Fim2/3 in unvaccinated elderly and by elevated IgG4 responses to multiple antigens only in children primed with acellular pertussis vaccine (aP). This work highlights the complexity of the immune response to this re-emerging pathogen and factors determining its Ig quantity and quality.