The influence of marginal zinc deficient diet on post-vaccination immune response against hepatitis B in rats.

Aim: To evaluate in vitro T lymphocyte proliferation and specific antibody response to hepatitis B vaccination in two groups of rats fed with normal and marginal zinc content.

Methods: Twenty-two Wistar-Albino rats were randomly assigned into two groups and were fed with constant diet. Zinc was suplemented 10mg/kg dry weight in group I (marginal zinc content) (n=14) and 30mg/kg dry weight in group II (n=8). Hepatitis B vaccine (Engerix B, 4mug) was administered intramuscularly after 8 weeks on feeding and a booster dose was applied 4 weeks after the first injection. Rats were killed 3 weeks after the second injection. Peripheral blood mononuclear cells were stimulated in vitro by PHA (2.5mug/ml) and hepatitis B surface antigen (2.5, 5, 10mug/ml). Proliferation was evaluated by ELISA (celltiter-96 aqueous one solution cell proliferation assay). Serum zinc, anti-HBs titer and zinc per dry liver weight were also measured. Two groups were compared with respect to antigen specific antibody and lymphocyte proliferation responses. Proliferation response to HbsAg were expressed as net percent increase (pci) in lymphocyte proliferation from the baseline activity.

Results: Rats' mean body weight and weight gain per month were similar. Median serum zinc was 39 (23-75) and 76(64-115)mug/dl of groups I and II rats, respectively (p<0.05), while there was no difference in liver zinc content between the two groups (37mug/g dry weight versus 32mug/g dry weight). Median anti-HBs levels of groups I and II were 741 (0-10,000)IU/l, 5791 (558-10,000)IU/l, respectively (p<0.05). In lymphocyte proliferation assays, mean net pci with HbsAg of 5 and 10mug/ml were 9.4% and 11.3% in group I rats; while they were 25.3% and 26.1% in group II rats (p<0.01 and p<0.01, respectively).

Conclusion: In vitro cell-mediated immune response and in vivo specific antibody response to hepatitis B vaccine was decreased in rats fed a diet with marginal zinc content. These observations have shown that marginal Zn deficiency might influence the efficacy of hepatitis B vaccination in humans.