Inhibitory effect of rBCG containing the fusion gene BFNA on EBV-positive tumours

Abstract

Background To obtain recombinant Bacillus Calmette-Guérin (rBCG) containing an Epstein–Barr virus (EBV) fusion gene that can inhibit EBV-positive cancer. Methods We obtained BZLF1 and EBNA1 cDNA, and overlapped jointly to assemble the fusion gene BFNA. Then pMV-BFNA was transformed into BCG-competent cells after inserting BFNA into pMV38. With western blotting to detect the target fusion protein, specific antibodies were detected in serum by ELISAs and spleen cell-specific cytokines were detected by ELISPOT. CTL activity, tumour weight, tumour formation time and mouse survival were analysed in EBV-positive tumour cell (NPRC18) cancer models, and flow cytometry was performed to analyse the quantities of CD8⁺ and CD4⁺ T cells in C57BL/6J mice. Single-factor analysis of variance was performed with SPSS 19.0 to evaluate rBCG inhibition. Results The molecular weight of the fusion protein was approximately 55.5 kD. The titer of antibody in the rBCG group was highly significant (P ≤ 0.01)and prolonged that tumorigenesis time, the specific killing ability targeting the recombinant target protein was increased. The rBCG group with the BFNA fusion gene demonstrated a better effect on tumours than BCG-EBNA1 and BCG-BZLF1 groups. Based on flow cytometry analysis, the numbers of CD4⁺ T and CD8⁺ T cells in the blood of the rBCG group were significantly higher than the control group (P < 0.01). The mice injected with rBCG had more obvious lymphocyte infiltration in the tumour area. Conclusions The rBCG exerts an obvious immune effect in mice and an inhibitory effect on EBV-positive tumour cell cancer models.