Direct infection of primary salivary gland epithelial cells by human T lymphotropic virus type I in patients with Sjögren's syndrome.

Objective: To investigate whether human T lymphotropic virus type I (HTLV-I) directly infects salivary gland epithelial cells (SGECs) and induces the niche of the salivary glands in patients with Sjögren's syndrome (SS).

Methods: SGECs were cultured with the HTLV-I-producing CD4+ T cell line HCT-5 or with Jurkat cells. Antibody arrays, immunofluorescence analysis, and enzyme-linked immunosorbent assay (ELISA) were used to determine the profiles of inflammation-related molecules, and the profiles of apoptosis-related molecules were determined by antibody array and immunofluorescence analysis. The presence of HTLV-I-related molecules was assessed by immunofluorescence analysis and in situ polymerase chain reaction. Apoptosis of SGECs was evaluated by TUNEL staining.

Results: Among the SGECs, 7.8 ± 1.3% (mean ± SD) were positive for HTLV-I-related proteins after 96-hour coculture with HCT-5 cells. Nuclear NF-κB p65 was also detected in 10% of the SGECs. The presence of HTLV-I proviral DNA in SGECs after coculture with HCT-5 cells was detected by in situ polymerase chain reaction. After coculture of SGECs with HCT-5, the expression of cytokines and chemokines, including soluble intercellular adhesion molecule 1, RANTES, and interferon γ-induced protein 10 kd (IP-10/CXCL10) was increased in a time-dependent manner. The expression of proapoptotic molecules (e.g., cytochrome c and Fas) and antiapoptotic molecules (e.g., Bcl-2, Heme oxygenase 2, and Hsp27) was increased in the SGECs cocultured with HCT-5, showing that apoptosis of SGECs was not detected after coculture with HCT-5 or Jurkat cells.

Conclusion: HTLV-I is thought to infect SGECs and alter their cellular functions. These changes may induce the niche of SS and contribute to the development of SS in anti-HTLV-I antibody-positive individuals.