Prokaryotic expression and antigen characteristics of EB virus latent membrane protein 2 ( EBV-LMP2) multi-epitopes / 中华微生物学和免疫学杂志

ABSTRACT

Objective To express in prokaryotic system and to analyze the antigenic specificity of EB virus(EBV) latent membrane protein 2(LMP2) multi-epitopes gene rich of T cell and B cell epitopes.Methods Using on-line prediction service, T cell epitopes and B cell epitopes of EB virus latent membrane protein 2 were predicted. The genes rich of CTL and th cell epitopes were selected as the candidate gene sequences, while B cell epitopes around them were taken into account. The finial selected multi-epitope gene was synthesized after being optimized according to prokaryotic codon bias and inserted into prokaryotic expression vector pET32a( + ) to get the recombinant plasmid pET32a( + )/EBV-LMP2 multi-epitopes. After transformed into E. coli BL21 (DE3) and induced by IPTG, the target multi-epitopes gene can be expressed as Trx-His fusion protein. The expression products can be identified by SDS-PAGE and Western blot. Moreover, rabbit serum antibody to EBV membrane protein and nasopharyngeal carcinoma(NPC) patient serum were used respectively to detect the antigenic specificity of the multi-epitopes. Meanwhile, 6-8 weeks female BALB/c mice were immunized with EBV-LMP2 multi-epitope at 2 week intervals, three times in all, Trx-His protein and PBS were set as the control groups. At the second week after the last immunization, the mice were sacrificed. LDH and indirect ELISA were taken to detect the specific spleen CTL activityand specific IgG in serum, which reflected the immunogenicity of the EBV-LMP2 multi-epitope. Results Two amino acid sequences which locate at the LMP2 (aa195 -232 ) and LMP2 (aa419-436 ) were selected and connected in series to be the target gene. The recombinant plasmid containing EBV-LMP2 multi-epitope gene successfully constructed and the target protein was expressed in E. coli BL21 ( DE3 ). The relative molecular mass(Mr) of The expression products is about 27 × 103 , which matches up to the expected Mr. The antigenic specificity of the multi-epitopes protein was identified by Western blot and the multi-epitopes protein also can be detected by rabbit serum antibody to EBV membrane protein and NPC patient serum respectively. In the result of the animal experiment, EBV-LMP2 multi-epitope was able to induce the specific CTL activity in BALB/c mice. With the increasing of the effector target ( E T) 1 5,1 10, 1 25, the CTL activity was also increased wih( 12.52% + 2.59% ), (21.80% + 1.08% ), (23.68% + 3.74% ) respectively; EBV-LMP2 multi-epitope was able to induce LMP2-specific antibody response(A490 =0.258 +0.040) as compared with Trx-His protein(A490 =0.095 +0.011) and PBS(A490 =0.068 +0.014,P＜0.05＝. Conclusion The EBV-LMP2 multi-epitopes gene was designed successfully and expressed precisely in prokaryotic expression system with good antigenicity and immunogenicity.