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 contribution to peripheral IFN-γ measurements and the temporal behavior of circulating T-cell immunity in adults remain incompletely defined. We investigated B. pertussis-reactive cellular immunity in peripheral blood in healthy and convalescent adult donors using IFN-γ ELISpot assays after stimulation with whole-cell B. pertussis or bacterial components (LPS and B. pertussis-derived LOS), and HLA-A02 genotyping. Short-term stimulation of unfractionated PBMCs produced a prominent IFN-γ response that was not clearly associated with previous vaccination or pertussis history. LOS and LPS induced strong responses in PBMCs but little detectable IFN-γ secretion by T cells, whereas whole-cell B. pertussis retained T-cell-associated IFN-γ response. Circulating B. pertussis-reactive T-cell responses were highest after recovery, declined substantially within approximately 3 months, and approached baseline by ≥1 year. CD8+ IFN-γ responses were preferentially detected in HLA-A*02-positive donors. These findings indicate that adult peripheral immunity to B. pertussis comprises cellularly and temporally distinct IFN-γ-producing components and that cellular context, time after infection, and HLA class I genotype influence their detection and interpretation.