O-antigen deficiency in Porphyromonas gingivalis attenuates dendritic cell-driven Th1/Th17-associated CD4+ T-cell responses

Porphyromonas gingivalis is a keystone periodontal pathogen whose lipopolysaccharide (LPS) contributes to immune dysregulation during periodontitis. Dendritic cells (DCs) link microbial recognition to adaptive immunity; however, how P. gingivalis LPS shapes DC activation and subsequent CD4 + T-cell responses remains incompletely understood. This study examined responses of human monocyte-derived DCs (hMoDCs) and downstream autologous CD4 + T lymphocytes to P. gingivalis strains that differ in complete LPS expression. hMoDCs were stimulated with the wild-type W50 strain, the isogenic O-antigen-deficient ΔPG1051 mutant, the complemented cΔPG1051 strain, or left unstimulated. We evaluated hMoDC maturation, cytokine responses, and expression of IRF4, IRF8, NOTCH2, and BATF3 by flow cytometry, RT-qPCR, and ELISA. We then co-cultured stimulated hMoDCs with autologous CD4 + T lymphocytes to assess cytokine and RANKL responses by RT-qPCR and ELISA and lineage-associated transcription factor expression by RT-qPCR. All P. gingivalis strains induced comparable maturation of hMoDCs. In contrast, W50 induced robust expression of Th1- and Th17-polarizing cytokines and increased IRF4 and NOTCH2 expression. Notably, ΔPG1051 markedly attenuated these hMoDC responses, and cΔPG1051 restored them. Consistently, CD4 + T lymphocytes co-cultured with ΔPG1051-stimulated hMoDCs showed attenuated Th1- and Th17-type responses, with reduced mRNA expression of Th1- and Th17-related cytokines, T-bet, RORC2, and RANKL, and lower protein levels of IL-1β, TNF-α, IL-6, IL-17A, IL-23, and RANKL. In contrast, Th2- and Treg-associated cytokines and transcription factors remained largely unchanged. These findings demonstrate that intact P. gingivalis LPS is a major determinant of DC inflammatory programming and its downstream capacity to promote Th1- and Th17-associated CD4 + T-cell responses.