Interferon-gamma (IFN-gamma) response to different hepatitis B virus antigens in hepatitis B virus infection.

The IFN-gamma levels in serum and cultured supernatant of peripheral blood mononuclear cells (PBMCs) were compared after stimulation by HBsAg ad, HBsAg ay and HBcAg among 3 groups of subjects i.e. patients with acute HBV infection, patients with chronic HBV infection and subjects recovered from HBV infection. Uninfected vaccinated group was taken as control. Serum and PBMCs were obtained from 38 individuals between 18-50 years of age. PBMCs were separated from heparinised blood by Ficoll-Hypaque density gradient centrifugation technique and cultured in CO2 incubator after stimulation by HBV surface and core antigens. IFN-gamma concentration was measured in serum and culture supernatant of PBMCs by an in-house ELISA technique. The mean serum IFN-gamma levels in acute, chronic, recovered and control groups were 88 pg/ml, 96.6 pg/ml, 155 pg/ml and 205 pg/ml respectively. On stimulation by HBsAg ad, IFN-gamma levels in cultured PBMCs of the above mentioned groups were 282.50 pg/ml, 307.45 pg/ml, 915.62 pg/ml and 511.67 pg/ml respectively, while in the same group on HBsAg ay stimulation, IFN-gamma levels were 246.25 pg/ml, 374.70 pg/ml, 1040 pg/ml and 465.83 pg/ml respectively. On stimulation by HBcAg, the IFN-gamma levels were 875 pg/ml, 128.50 pg/ml, 905 pg/ml and 235.33 pg/ml respectively in the acute, chronic, recovered and control groups. When compared with serum, significantly higher levels of IFN-gamma in cultured supernatant of PBMCs were observed after stimulation by HBsAg ad and HBsAg ay subtype in cases of chronic (p<0.05) and recovered groups (p<0.01 and p<0.001 respectively). However, no statistically significant difference of IFN-gamma level was observed between serum and PBMCs amongst the acute and control groups when stimulated by either of the HBsAg subtypes or HBcAg. In the recovered group, IFN-gamma levels produced by PBMCs after stimulation by HBcAg were significantly higher than that of serum (p<0.01). The study concludes that on subsequent exposure, PBMCs of the recovered group produces higher levels of IFN-gamma in response to different hepatitis B antigens. This response perhaps is able to protect individuals who are unable to develop anti-HBs.

Expression of Th1 and Th2 type cytokines responding to HBsAg and HBxAg in chronic hepatitis B patients

The cytokine pattern on viral antigen recognition is believed to exert a profound influence on the resolution of viral infections and viral clearance. This study was initiated to investigate whether a cytokine imbalance oriented toward Th2 type response plays a role in chronic hepatitis B. Cytokine profiles of peripheral blood mononuclear cells associated with chronic hepatitis B were analysed by RT-PCR. Upon HBsAg stimulation, expression of IFN-gamma, IL-2, IL-4, and IL-10 was detected in 41%, 8%, 41%, and 50% of the patients, respectively. Among these cytokines, the expression of IFN-gamma was associated with high levels of serum AST/ALT. However, we could not prove that Th2 type cytokines had a protective effect on hepatocytes. Upon HBxAg stimulation, there was no recognizable association of cytokine patterns with AST/ALT levels. In conclusion, production of a Th1 cytokine, IFN-gamma, by HBsAg-reactive cells was associated with hepatocyte damage in chronic hepatitis B, while no counteracting effect of Th2 cytokines produced by those cells was observed.