Neutrophils, also known as polymorphonuclear leukocytes (PMNs), form a significant component of the innate host response, and the consequence of the interaction between the oral microbiota and PMNs is a crucial determinant of oral health status. The impact of radiation therapy (RT) for head and neck tumour (HNT) treatment on the oral innate immune system, neutrophils in particular, and the oral microbiome has not been thoroughly investigated. Therefore, the objective of this study was to characterize RT-mediated changes in oral neutrophils (oPMNs) and the oral microbiome in patients undergoing RT to treat HNTs. Oral rinse samples were collected prior to, during and post-RT from HNT patients receiving RT at Dental Oncology at Princess Margaret Cancer Centre. The oPMNs counts and activation states were analysed using flow cytometry, and the oral microbiome was analysed using 16S rRNA gene sequencing. Statistically significant (p < 0.05) drops in oPMN counts and the activation states of the CD11b, CD16, CD18, CD64 and H3Cit markers from pre-RT to post-RT were observed. Moreover, exposure to RT caused a significant reduction in the relative abundance of commensal Gram-negative bacteria and increased the commensal Gram-positive microbes. Ionizing radiation for the treatment of HNTs simultaneously decreased the recruitment of oPMNs into the oral cavity and suppressed their activation state. The oral microbiome composition post-RT was altered significantly due to RT which may favour the colonization of specific microbial communities unfavourable for the long-term development of a balanced oral microbiome.

Neutrophils, the most numerous leukocytes, play an important role in maintaining oral health through interactions with oral microbial biofilms. Both neutrophil hyperactivity and the bacterial subversion of neutrophil responses can cause inflammation-mediated tissue damage like that seen in periodontal disease.

Lantibiotics are ribosomally synthesized and posttranslationally modified peptides (RiPPs) that are produced by bacteria. Interest in this group of natural products is increasing rapidly as alternatives to conventional antibiotics. Some human microbiome–derived commensals produce lantibiotics to impair pathogens’ colonization and promote healthy microbiomes. Streptococcus salivarius is one of the first commensal microbes to colonize the human oral cavity and gastrointestinal tract, and its biosynthesis of RiPPs, called salivaricins, has been shown to inhibit the growth of oral pathogens. Herein, we report on a phosphorylated class of three related RiPPs, collectively referred to as salivaricin 10, that exhibit proimmune activity and targeted antimicrobial properties against known oral pathogens and multispecies biofilms. Strikingly, the immunomodulatory activities observed include upregulation of neutrophil-mediated phagocytosis, promotion of antiinflammatory M2 macrophage polarization, and stimulation of neutrophil chemotaxis—these activities have been attributed to the phosphorylation site identified on the N-terminal region of the peptides. Salivaricin 10 peptides were determined to be produced by S. salivarius strains found in healthy human subjects, and their dual bactericidal/antibiofilm and immunoregulatory activity may provide new means to effectively target infectious pathogens while maintaining important oral microbiota.

Background/Objectives: Aging alters neutrophil functions, which may contribute to the progression and severity of periodontitis-related alveolar bone loss. Neutrophils play a key role in immune defense. However, the effects of aging on neutrophil functions and their contribution to periodontal disease remain unclear. This study examined age-related neutrophil dysfunction and its impact on periodontal bone loss. Methods: We used young (6 weeks old) and aged (18 months old) C57BL/6 mice to assess age-related neutrophil function. Neutrophil migration, superoxide production, phagocytic activity, and NETosis were evaluated. A peritonitis model and a ligature-induced periodontitis model were employed to investigate the relationship between neutrophil activity and alveolar bone loss. Results: Neutrophils from aged mice exhibited reduced migration toward pathogens compared to those from young mice. However, aged neutrophils showed increased superoxide production, elevated phagocytic activity, and enhanced NETosis. In the periodontitis models, these age-related neutrophil alterations coincided with accelerated alveolar bone loss in aged mice. Conclusions: The findings indicate that aging is linked to dysregulated neutrophil functions, characterized by excessive oxidative stress, heightened phagocytosis, and increased NETosis. These functional changes may contribute to immune dysregulation and tissue damage, thereby promoting age-related alveolar bone loss in periodontitis.

Non-invasive quantitative assessment of oral inflammatory burden could complement conventional periodontal evaluation; however, current clinical methods primarily characterize disease after structural and tissue changes have occurred. In our previously reported DePerio framework, we demonstrated the feasibility of enriching oral polymorphonuclear neutrophils (oPMNs) from saliva through their differential adhesion to a hydrophilic cornstarch (CS)-coated surface, followed by brightfield imaging and AI-assisted quantification. Building on this framework, here we present BioSA, with an emphasis on the mechanistic and quantitative characterization of this biologically inspired adhesion-based oPMN isolation process, analogous to leukocyte adhesion behavior in blood capillaries. We systematically investigate the contributions of surface physicochemical properties, oPMN surface characteristics, and physical forces governing preferential oPMN retention and epithelial-cell removal. The optimized adhesion-based isolation reduced epithelial-cell contamination by 91% while preserving >98% of oPMNs, outperforming the evaluated filtration- and poly-L-lysine (PLL)-based approaches. Following isolation, brightfield images were analyzed using an AI-assisted deep-learning model for automated oPMN quantification. Across 30 independent test days, BioSA measurements were strongly associated with those obtained using the reference HEMO method (R² ≈ 0.99; MAE ≈ 2.06 × 10⁵ cells/10 mL), while method agreement and systematic differences were further evaluated using Bland–Altman analysis. The deep-learning detector achieved 98% sensitivity, 97% precision, and an F1 score of 0.97 on a dataset containing 4617 manually annotated oPMNs. Using data-driven oPMN concentration ranges informed by prior literature, we further explored five oral inflammatory load (OIL) strata. These strata are hypothesis-generating and should not be interpreted as validated diagnostic stages or as replacements for the 2017 periodontitis staging and grading framework. Operating with standard brightfield microscopy and a cloud-based AI interface, BioSA reduces analysis time from 15 to 20 min to less than 2 min per sample. Collectively, this study extends the DePerio framework by providing mechanistic insight into biologically inspired adhesion-based oPMN isolation and demonstrates its potential for rapid, quantitative, and exploratory assessment of oral inflammatory burden.