[Effect of exogenous epitopes of helper T lymphocyte on humoral immunity of HBV S gene DNA immunity].

Objective: To study the effect of exogenous epitope of helper T lymphocyte (HTL) on humoral immunity of HBV S gene DNA immunity.

Methods: Two universal HTL epitopes, amino acid residue (aa) 830-843 of the tetanus toxoid (TTE) and artificial epitope (PADRE), and 3 unique epitopes, aa1-20 of tubercle bacteria hot shock protein 65 (TBE), aa54-65 of rubella protein E2-4 (ME) and aa35-48 of trachoma hot shock protein 60 (CE) were chosen. Eukaryotic expression vectors were constructed by inserting single or multiple exogenous epitopes in HBV S gene just after the initial code of translation. BALB/c mice were inoculated with 100 micro g of recombinant DNA per mouse, and given boost inoculation for 3 times with 3-week interval. Mouse blood were collected one month just after the third boost inoculation. Anti-HBs was detected using Abbott test kits.

Results: HBV S eukaryotic gene expression vectors, pHB and 6 exogenous HTL epitope HBV S gene vectors, pHB-TBE, pHB-PADRE, pHB-TTE, pHB-MTE2, pHB-MTE3 and pHB-MTE5 were constructed successfully with anti-HBs level (IU/L) of 10 +/- 5, 5 +/- 5, 49 +/- 7, 29 +/- 6, 16 +/- 8, 23 +/- 7 and 28 +/- 8 respectively. Among 3 single epitopes, TTE and PADRE had obviously effect on promoting the anti-HBs response of HBV S gene, while TBE had no promoting effect. All of the 3 multiple epitopes were shown the effect of immune promoting.

Conclusion: Some exogenous HTL epitopes had obviously effect on promoting the anti-HBs response of HBV S gene. Multiple epitopes also had humoral immunity promoting effect, but there was no synergic effect among their own HTL epitopes. PADRE might be an important candidate for new efficient HB vaccine. The multiple epitope cluster consisted form 5 exogenous epitopes might be an important candidate for the reinoculating HB vaccine or therapy HB vaccine.