Uric acid enhances T cell immune responses to hepatitis B surface antigen-pulsed-dendritic cells in mice

To study the induction of T cellular immune responses in BALB/c mice immunized with uric acid and dendritic cells (DCs) pulsed with hepatitis B virus surface antigen (HBsAg).

DCs were generated from bone-marrow cells of BABL/c mice, and then pulsed or unpulsed with HBsAg protein (HBsAg-pulsed-DCs or unpulsed-DCs) in vitro. BABL/c mice were immunized with HBsAg-pulsed-DCs (1 x 10(6)) and uric acid, injected through the tail vein of each mouse. The mice in control groups were immunized with HBsAg-pulsed-DCs alone, unpulsed-DCs alone or 200 microg uric acid alone or PBS alone. The immunization was repeated 7 d later. Cytotoxic T lymphocytes (CTLs) in vivo were determined by the CFSE labeled spleen lysis assay. Spleen cells or spleen T cells were isolated, and re-stimulated in vitro with HBsAg for 120 h or 72 h. Production of IFN-gamma and IL-4 secreted by spleen cells were determined by ELISA method; proliferation of spleen T cells were detected by flow cytometry.

The cytotoxicities of HBsAg-specific-CTLs, generated after immunization of HBsAg-pulsed-DCs and uric acid, were 68.63% +/- 11.32% and significantly stronger than that in the control groups (P < 0.01). Compared with control groups, in mice treated with uric acid and HBsAg-pulsed-DCs, the spleen T cell proliferation to HBsAg re-stimulation was stronger (1.34 +/- 0.093 vs 1.081 +/- 0.028, P < 0.01), the level of IFN-gamma secreted by splenocytes was higher (266.575 +/- 51.323 vs 135.223 +/- 32.563, P < 0.01) , and IL-4 level was lower (22.385 +/- 2.252 vs 40.598 +/- 4.218, P < 0.01).

Uric acid can strongly enhance T cell immune responses induced by HBsAg-pulsed-DCs vaccine. Uric acid may serve as an effective adjuvant of DC vaccine against HBV infection.