Herpesvirus Simplex Virus-1 Exploits Inflammation to Infect Periodontal Stem Cells and Disrupt Lineage Commitment

Elevated levels of Herpes Simplex Virus 1 (HSV-1) have been reported in periodontitis, however, the tropism and relationship with periodontal inflammation are poorly characterized. This study investigated how inflammation affects viral tropism toward human periodontal ligament stem cells (hPDLSCs).

HSV-1 gB and gD transcripts in healthy and diseased human gingiva were measured by RT-qPCR and confirmed in HSV-1-infected murine gingiva. HSV-1 infection in hPDLSCs was analyzed by imaging and flow cytometry. hPDLSCs were individually treated with IL-6, TNF-α, GMCSF, IL-10, or PgLPS, and HSV-1 replication was assessed by infecting with the 17 GFP strain. Lineage markers in virally infected hPDLSCs during osteogenic differentiation were measured by RT-qPCR and immunofluorescence in vitro and validated in vivo. Mice subjected to ligature-induced periodontitis (LIP) and infected with HSV-1 were examined for gingival histology, inflammatory cytokines, and alveolar bone loss.

Inflamed human gingiva showed higher expression of viral transcripts compared to healthy controls. In mouse oral HSV-1 infection, gB and gD expression increased over time, with higher levels in mice with ligature-induced periodontitis. Virus infected hPDLSCs challenged with inflammatory mediators or PgLPS showed higher GFP, while IL-10 treatment attenuated GFP levels. Importantly, HSV-1 17 GFP infection affected osteoblast lineage commitment by promoting the expression of key transcription factors in vitro and in vivo. Compared to the LIP alone group, higher levels of inflammatory markers and bone loss were evident in HSV-1 infected with LIP.

hPDLSCs are trophic to HSV-1 in vitro and in vivo, with periodontal inflammation playing a significant role in viral tropism.