Design and expression of fusion protein consists of HBsAg and Polyepitope of HCV as an HCV potential vaccine

Immune response induced by recombinant pres2/S-protein and a pres2-S-protein fused with a core 18-27 antigen fragment of hepatitis B virus compared to conventional HBV vaccine

Although comprehensive vaccination is the cornerstone of public health programs to control hepatitis B virus (HBV) infections, 5% of people who receive the existing vaccine do not develop proper immunity against HBV. To overcome this challenge, researchers have tried using various protein fragments encoded by the virus genome to achieve better immunization rates. An important antigenic component of HBsAg called the preS2/S or M protein has also received much attention in this area. The gene sequences of preS2/S and Core18-27 peptide were extracted from the GenBank (NCBI). Final gene synthesis was conducted with pET28. Groups of BALB/c mice were immunized with 10 μg/ml of recombinant proteins and 1 μg/ml CPG7909 adjuvant. Serum levels of IF-γ, TNF-α, IL-2, IL-4, and IL-10 were measured by ELISA assay method on spleen cell cultures on day 45, and IgG1, IgG2a, and total IgG titers obtained from mice serum were quantified on days 14 and 45. Statistical analysis did not show any significant difference between the groups regarding IF-γ level. There were, however, significant differences in terms of IL-2 and IL-4 levels between the groups receiving preS2/S-C18-27 with and without adjuvant and the groups receiving both preS2/S and preS2/S-C18-27 (Plus Recomb-Plus Recomb: the group of mice that received both preS2/S and preS2/S-C18-27 simultaneously). The strongest total antibody production was induced by immunization with both recombinant proteins without CPG adjuvant. The groups that received both preS2/S and preS2/S-C18-27, whether with or without adjuvant, were significantly different from those that received the conventional vaccine considering most abundant interleukins. This difference suggested that higher levels of efficacy can be achieved by the use of multiple virus antigen fragments rather than using a single fragment.

Comparison of Immune Response in Mice Immunized with Recombinant PreS2/S-C18-27 Protein Derived from Hepatitis B Virus with Commercial Vaccine

BACKGROUND & OBJECTIVE

The vaccine available to prevent Hepatitis B virus disease is ineffective in 5% of people due to the use of HBsAg as a weak immunogenic factor. In the present study, PreS2/S fused to C18-27 peptide fragment as an effective antigen and is proposed as a promising vaccine candidate compared with the conventional vaccine prescribed in the vaccination program.

METHODS

After the synthesis of PreS2/S genes and C18-27 peptide fragment in pET28a, the recombinant protein was confirmed by Western blotting. The efficacy of the PreS2/S-C18-27 protein was compared with the conventional vaccine injected into five groups of rats. Finally, the cytokine level of IF-r, IL-2, IL-4, IL-10, TNF-a, IgG1, and IgG2a were measured using the ELISA method.

RESULTS

This study showed no significant difference between the recombinant vaccine group and PBS control group in the IF-r test, but there was a significant difference between groups testing IL-2 and IL-10. In addition, the group receiving the recombinant vaccine with CPG adjuvant at a dilution of 1/10 in the IgG total test on days 14 and 45 after the first injection showed a significant difference in comparison with other groups.

CONCLUSION

This study showed no statistically significant difference between the recombinant protein vaccine group and the conventional vaccine group. The Th1- mediated immune responses obtained from recombinant proteins with and without CPG performed better than conventional vaccines, possibly due to the functional deficiency of the available vaccines.

Effects of mRNA secondary structure on the expression of HEV ORF2 proteins in Escherichia coli

Background

Viral protein expression in Escherichia coli (E. coli) is a powerful tool for structural/functional studies as well as for vaccine and diagnostics development. However, numerous factors such as codon bias, mRNA secondary structure and nucleotides distribution, have been indentified to hamper this heterologous expression.

Results

In this study, we combined computational and biochemical methods to analyze the influence of these factors on the expression of different segments of hepatitis E virus (HEV) ORF 2 protein and hepatitis B virus surface antigen (HBsAg). Three out of five HEV antigens were expressed while all three HBsAg fragments were not. The computational analysis revealed a significant difference in nucleotide distribution between expressed and non-expressed genes; and all these non-expressing constructs shared similar stable 5′-end mRNA secondary structures that affected the accessibility of both Shine-Dalgarno (SD) sequence and start codon AUG. By modifying the 5′-end of HEV and HBV non-expressed genes, there was a significant increase in the total free energy of the mRNA secondary structures that permitted the exposure of the SD sequence and the start codon, which in turn, led to the successful expression of these genes in E. coli.

Conclusions

This study demonstrates that the mRNA secondary structure near the start codon is the key limiting factor for an efficient expression of HEV ORF2 proteins in E. coli. It describes also a simple and effective strategy for the production of viral proteins of different lengths for immunogenicity/antigenicity comparative studies during vaccine and diagnostics development.

Electronic supplementary material

The online version of this article (10.1186/s12934-017-0812-8) contains supplementary material, which is available to authorized users.