Preclinical B. pertussis challenge models were successfully established in Europe. The effect of different inoculation routes on disease and microbiological endpoints was assessed, and novel, advanced in vivo imaging methods were used to investigate pathophysiology. A series of studies with B. pertussis were performed to compare whole-cell and acellular pertussis vaccines to immunity induced by prior infection. These studies identified a number of humoral and cellular immune features that are important for protection against infection, including a crucial role for tissue-resident memory cells, IL17 and neutrophils in the clearance of B. pertussis from the respiratory tract. The establishment of preclinical challenge models in Europe provides essential capacity to vaccine companies for evaluating the efficacy of new pertussis vaccines against disease.
Due to the infeasibility of large-scale studies to demonstrate efficacy of next generation pertussis vaccines against clinical endpoints of disease, controlled human infection models (CHIMs) are likely to play a key role in the development and licensure of new pertussis vaccines. CHIM studies potentially provide the fastest, most cost-effective and most controlled option to establish proof-of-concept for new products. As such, a controlled human B. pertussis infection model was developed by the consortium. A first-in-human, inpatient, dose-escalation study was performed with wild type B. pertussis, aiming to achieve >70% colonization in volunteers with an acceptable safety profile. This study identified the inoculum dose that induced 80% colonization, with no evidence of bacterial shedding. Based on the safety and microbiological parameters of the dose-escalation study, a second, outpatient dose-validation study was performed, aiming to identify immunological biomarkers associated with protection against B. pertussis. Systems immunology analysis identified a number of biomarkers that were associated with early control of bacterial infection, highlighting the role of mucosal immunity in protection, particularly the role of mucosal antibodies, Th2-associated responses and cellular responses.
PERISCOPE also performed an observational clinical study in four different age groups of patients that were diagnosed with pertussis. Patients were followed up for up to 1 year after infection to investigate the functionality and persistence of the immune response to pertussis. In parallel, the consortium performed an international multi-center acellular pertussis booster vaccination study that was performed in the same age groups as the pertussis patients.
Finally, three infant vaccination studies were performed in Finland, the UK and the Gambia (AWARE2, GAPs, MIFI). Despite the major impact of the COVID-19 pandemic, these studies were successfully completed within the project period, with immunological analysis partially complete and/or still ongoing.
A biobank for sample storage from all clinical studies was established. This biobank acted as the central repository for distribution of samples to the partner laboratories for analysis.
The consortium interacted with regulatory authorities in an effort to gain insight into the potential acceptance of results from the PERISCOPE project, as well as to identify potential regulatory pathways for licensure of the next generation of pertussis vaccines. Meetings were held with the European Medicine’s Agency (EMA), during which results from the PERISCOPE project were presented and valuable feedback was obtained on the position of the preclinical and human challenge models for regulatory purposes.
A biomarker discovery platform was established to investigate the immune response to pertussis, with a clear focus on clinical development. In total, 14 novel immunological assays were developed and qualified for analysis, either in central laboratories for centrally-biobanked samples and/or locally for samples that needed to be analysed immediately. These biomarker assays were selected to measure crucial aspects of immunity to pertussis, including quantification of serum and mucosal antibodies and their functional properties (bactericidal activity, complement deposition, inhibition of bacterial adherence to epithelial cells, pertussis toxin neutralization, etc), as well as cellular immune responses to pertussis in blood, focusing on antigen-specific T- and B-cells. These assays were successfully applied to clinical samples obtained from the vaccination and/or challenge studies described above. In addition to biomarker assays that assess antigen-specific properties, we also established and/or applied a number of general phenotyping assays, aimed at quantifying (changes in) cell populations and/or gene expression in peripheral blood and in the upper respiratory tract, using advanced immunological methods such as EuroFlow, CyTOF and (single-cell) RNAseq. To handle the complexity and richness of clinical and immunological data from the various clinical studies, we established a tranSMART database to centrally store immunological and participant-level data from all clinical studies. Finally, bioinformatics analysis pipelines were established for systems immunological analysis of these data.
