Synthesis of multiple antigenic peptide vaccine based on predominant epitopes of Helicobacter pylori UreB protein and immunoprotection of the vaccine
Objective To generate a prokaryotic expression system of series predominant epitopes (UreB322 and UreB527) of Helicobacter pylori UreB protein,and to synthesize a multiple antigenic peptide (MAP) vaccine by linking both the two epitopes with a peptide carrier (Poly-Asp-Lys),and to determine the immunogenicity and immunoprotection of the MAP vaccine.Methods Linking primer PCR was performed to generate an enterokinase(EK) site-containing series UreB322 and UreB527 epitope encoding gene for construction of its prokaryotic expression system.The expressed target recombinant fusion protein 8 ×[rEK-UreB322-EK-UreB527-EK] was hydrolyzed with EK and then rUreB322-EK and rUreB527-EK epitope peptides were extracted using a Sephadex G-25 column.rUreB322-EK,rUreB527-EK and Poly-Asp-Lys were linked using carbodiimide method to produce a MAP vaccine (MAP-rUreB322/B527).The antigenicity and immunoreactivity of each of the two epitope peptides and MAP-rUreB322/527 were determined by ELISA and Western blot assay.An animal H.pylori strain SS1-infected model in BALB/c mice was used to detect the immunoprotection of MAP-rUreB322/527.Results An octuple-repeated series UreB322-UreB527 encoding gene and its prokaryotic expression system were obtained.The yield of target fusion protein 8×[rEKUreB322-EK-rUreB527-EK] was as high as 48％ of the total bacterial proteins.EK hydrolyzed the target fusion protein completely into rUreB322-EK and rUreB527-EK peptides.The linking ratio of rUreB322-EK,rUreB527-EK and Poly-Asp-Lys was as high as 92.5％.The antibody against whole cell of H.pylori and rUreB-IgG could recognize and combine with the rUreB322-EK,rUreB527-EK or MAP-rUreB322/527.The specific serum antibody level in MAP-rUreB322/527-immunized mice was significantly higher than that in rUreB-immunized mice (P＜0.05).The immunoprotective rates(83.3％ and 91.7％ ) by immunization with 50 or 100 μg MAP-rUreB322/527 in the H.pyloristrain SSI-infected mice were significantly higher that those(d1.7％ and 50.0％ ) by immunization with equal rUreB(P＜0.05).Conclusion An gene composed for encoding a repeated series predominant epitopes of H.pylori UreB protein and its prokaryotic expression system are successfully generated in this study.MAP-rUreB322/527,the multiple antigenic peptide vaccine based on the two predominant epitopes of UreB,can noticeably increase the immunoprotection in H.py/or/infected mice. 
 
Key words: 
Helicobacter py/ori; UreB; Predominant antigenic epitopes; Multiple antigenic peptide vaccine; Immunoprotection