Salivary microRNA Profiling of Long COVID Subjects Reveals Host-Encoded Regulators of Inflammation and Viral Persistence

Abstract

Periodontal disease and COVID-19 are linked by convergent immunoinflammatory pathways, yet the molecular basis of their interaction remains poorly defined. Here, we present a comprehensive salivary microRNA profile from individuals with prior SARS-CoV-2 infection, sampled approximately 3-6 months after diagnosis and meeting criteria for long COVID, providing new insight into the post-viral oral microenvironment. Salivary miRNA sequencing revealed widespread repression in patients with PD, consistent with persistent immune dysregulation. Relative to COVID-19-negative/PD-negative controls, thirty-two miRNAs were differentially expressed in COVID-19-positive/PD-positive individuals, all significantly downregulated. A similar signature was observed in a post-vaccination cohort for the selected dysregulated miRNAs. Integrative pathway analyses identified these miRNAs as regulators of core inflammatory circuits, including Ras, MAPK, and NF{kappa}B signaling, converging on IL-1{beta}- and TNF-centered networks relevant to both PD and COVID-19. Mechanistically, restoration of three downregulated miRNAs, miR- miR-30e-3p 106-3p-3p, and miR-652-3p attenuated NF{kappa}B activation and cytokine release in TLR-stimulated human oral keratinocytes, while their functional suppression using inhibitors potentiates inflammation. These miRNAs were also predicted to target SARS-CoV-2 spike and nucleocapsid transcripts, an interaction validated by dual-luciferase reporter assays. Their overexpression further reduced spike and nucleocapsid expression in Beta- and Omicron-infected epithelial cells, as measured by flow cytometry and RT-qPCR confirming host miRNAs as potent endogenous SARS-CoV-2 restriction factor. Together, these findings identify salivary host miRNAs as mechanistic regulators of oral inflammatory tone and viral persistence, establishing a molecular link between periodontal inflammation and post-COVID oral pathology.