Abstract: Objective To study the lymphoproliferative responses to HHV-6 （Human Herpesvirus-6, HHV-6）among patients with oral squamous cell carcinoma, and discuss the role of HHV-6 in the pathogenesis of oral squamous cell carcinoma. Methods IgG antibody to HHV-6 in plasma were identified by means of indirect immunofluorescence (IIF). Immuno-magnetic beads were used to prepare CD4+ T cells and CD8+ T cells. The proliferation of CD4+ T cells, CD8+ T cells and PBMCs stimulated with HHV-6 or anti-CD3 antibodies were measured by means of 3H-thymidine uptake. The percentage of CD4+ CD25+ Treg cells（Regulatory T cell,Treg）within the peripheral blood CD4+ T cell compartment was analyzed by flow cytometry. Results Significantly higher proportion of patients with oral squamous cell carcinoma had IgG antibody to HHV-6 (8/8 ) in plasma compared with those in control subjects (12/20 )；The proliferative responses of PBMCs and CD4+ T cells from patients withoral squamous cell carcinoma to HHV-6 were significantly decreased compared to those from HHV-6-infected and uninfected healthy individuals（P＜ 0.05；P＜ 0.05）. The proliferative responses of PBMCs and CD4+ T cells from HHV-6-infected healthy individuals to HHV-6 were significantly decreased compared to those from HHV-6-uninfected healthy individuals（P＜ 0.05）；Patients with oral squamous cell carcinoma had a significantly higher percentage of CD4+ CD25+ Treg cells within the peripheral blood CD4+ T cell compartment compared with HHV-6 infected and uninfected healthy individuals did. Conclusion These results demonstrated that impairment of HHV-6-specific CD4+ T cell immune responses in patients with oral squamous cell carcinoma, therefore, HHV-6 possibly plays a role in the pathogenesis of oral squamous cell carcinoma.

Key words: Human herpesvirus-6, oral squamous cell carcinoma, lymphoproliferation, CD4+ CD25+ Treg cell