Dissecting Adult Peripheral Cellular Immunity to Bordetella pertussis: Innate-Associated IFN-γ Responses, Transient T-Cell Recall, and HLA-A*02-Associated CD8+ Reactivity.

Bordetella pertussis elicits both innate and adaptive cellular responses, yet their relative contributions to peripheral interferon-γ (IFN-γ) measurements and the temporal dynamics of circulating T-cell reactivity in adults remain incompletely defined. B. pertussis-reactive cellular immunity was investigated in 42 adult donors, including 26 healthy donors and 16 donors with a history of pertussis, using standard and modified IFN-γ enzyme-linked immunospot (ELISpot) assays with a chemically inactivated whole-cell B. pertussis preparation, bacterial innate-biased stimuli, and a peptide-based T-cell recall control, together with human leukocyte antigen A*02 (HLA-A*02) genotyping. Short-term stimulation of unfractionated peripheral blood mononuclear cells (PBMCs) generated readily detectable IFN-γ spot formation that was not clearly stratified by childhood vaccination background or previous pertussis history. In a subset of seven donors, lipopolysaccharide and B. pertussis-derived lipooligosaccharide generated strong total PBMC signals but little detectable pattern-defined T-cell-associated spot formation, whereas the whole-cell pertussis preparation retained a detectable T-cell-associated component under modified assay conditions. Among seven donors available for longitudinal follow-up after pertussis, pattern-defined T-cell-associated IFN-γ spot frequencies in peripheral blood were highest at the recovery sampling point, were significantly reduced at one month, decreased further by three months, remained markedly reduced at six months, and approached background levels at 12 months after recovery. Directly measured CD8+ IFN-γ responses were preferentially detected in HLA-A*02-positive donors. These findings indicate that cellular composition and sampling time affect the interpretation of peripheral IFN-γ responses to B. pertussis and show an association between HLA-A*02 status and detectable CD8+ reactivity.