Production of interferon-γ and interleukin-10 after inactivated hepatitis A immunization

Study Objective. To assess helper T cell function by measuring cytokine production over time after hepatitis A immunization. Design. Open-label, single-dose study. Setting. General clinical research center of a university hospital. Subjects. Twenty-five healthy adults. Intervention. Each subject was immunized with inactivated hepatitis A vaccine; blood was drawn on day 0 (the day of immunization) and days 2, 5, 7, 10, and 28 after immunization. Measurements and Main Results. Production of interferon (IFN)-gamma and interleukin (IL)-10 by peripheral blood mononuclear cells stimulated in culture with hepatitis A virus was measured by enzyme-linked immunosorbent assay. Concentrations of hepatitis A antibody were measured on day 28. Both IFN-gamma and IL-10 production peaked on day 10 after immunization (IFN-gamma day 0 median = 7.35 pg/ml, interquartile ratio [IQR] = 20.8 vs day 10 median = 22.35 pg/ml, IQR 42.4, p<0.05; IL-10 day 0 median = 1.00, IQR = 7.4 vs day 10 median 11.75 pg/ml, IQR = 92.3, p<0.02, Wilcoxon signed rank test). The IL-10:IFN-gamma ratio on day 10 correlated with antibody production (Pearson product moment correlation 0.46, p<0.05). This ratio was used as a measure of helper T cell phenotype. Conclusion. Both IFN-gamma and IL-10 are produced in response to hepatitis A vaccine. The parallel production after immunization may contribute to the high efficacy of these vaccine preparations in inducing both cell-mediated immune response and a protective antibody response.