Chronic ethanol diet increases regulatory T-cell activity and inhibits hepatitis C virus core-specific cellular immune responses in mice

Aim: Chronic ethanol consumption is associated with persistent hepatitis C viral (HCV) infection. This study explores the role of the host cellular immune response to HCV core protein in a murine model and how chronic ethanol consumption alters T-cell regulatory (Treg) populations. Methods: BALB/c mice were fed an isocaloric control or ethanol liquid diet. Dendritic cells (DC) were isolated after expansion with a hFl3tL-expression plasmid and subsequently transfected with HCV core protein. Core-containing DC (1×10⁶) were s.c. injected (×3) in mice every 2weeks. Splenocytes from immunized mice were isolated and stimulated with HCV core protein to measure generation of viral antigen-specific Treg, as well as secretion of interleukin (IL)-2, tumor necrosis factor (TNF)-α and IL-4. Cytotoxicity was measured by lactate dehydrogenase release from HCV core-expressing syngeneic SP2/19 myeloma cells. Results: Splenocytes from mice immunized with ethanol-derived and HCV core-loaded DC exhibited significantly lower in vitro cytotoxicity compared to mice immunized with HCV core-loaded DC derived from isocaloric pair-fed controls. Stimulation with HCV core protein triggered higher IL-2, TNF-α and IL-4 release in splenocytes following immunization with core-loaded DC derived from controls as compared to chronic ethanol-fed mice. Splenocytes derived from mice immunized with core-loaded DC isolated from ethanol-fed mice exhibited a significantly higher CD25⁺FOXP3⁺ and CD4⁺FOXP3⁺Treg population. Conclusion: These results suggest that immunization with HCV core-containing DC from ethanol-fed mice induces an increase in the CD25⁺FOXP3⁺ and CD4⁺FOXP3⁺Treg population and may suppress HCV core-specific CD4⁺ and CD8⁺ T-cell immune responses.