Periodontitis Primes the Oral Microenvironment for PS-Dependent Non-Canonical Entry Pathways Linked to SARS-CoV-2 Susceptibility

SARS-CoV-2 infection extends beyond the respiratory tract, with the oral cavity emerging as a critical site of viral activity shaped by epithelial receptor expression, microbial interactions, and inflammatory status. Periodontal disease (PD), a chronic dysbiotic condition, may heighten susceptibility to SARS-CoV-2 through inflammation-driven upregulation of non-canonical viral entry pathways. In this study, we investigated genes in the phosphatidylserine (PS)–dependent pathway, including ADAM17, ATP11c, TIM1, TIM3, and TIM4, in gingival tissue, saliva, and oral keratinocytes to define how PD and SARS-CoV-2 coordinately modulate oral viral entry mechanisms. Prepandemic gingival biopsies revealed significant upregulation of all non-canonical receptors in inflamed tissue, indicating that PD alone establishes a permissive molecular environment for PS-mediated microbial entry. In a post-vaccination cohort, salivary expression of these receptors was markedly elevated in COVID-19–positive individuals with PD, accompanied by significantly increased salivary PS levels, suggesting synergistic effects of viral exposure and periodontal inflammation. In vitro co-infection of primary human oral keratinocytes with SARS-CoV-2 and periodontal pathogens ( P. gingivalis , A. actinomycetemcomitans ) induced robust, synergistic activation of PS-dependent entry genes, particularly TIM family receptors. Together, these findings identify PS and its associated receptors as inflammation-responsive mediators that expand SARS-CoV-2 entry routes in the oral mucosa. This work highlights a mechanistic intersection between COVID-19 and periodontal disease, with implications for viral persistence, immune dysregulation, and long-term oral health outcomes.