Attenuated Salmonella carrying plasmid co-expressing HPV16 L1 and siRNA-E6 for cervical cancer therapy

Changshuai Wang,Tuo Zhou,Junyu Chen,Taiwei Wang,Zhuo Zhang,Yu Jiang,Shuhua Zhao,Wenxi Tan,Shan Wu,Lijing Zhao

doi:10.1038/s41598-021-99425-3

Abstract

Human papillomavirus (HPV) infection is the major etiological factor for cervical cancer. HPV prophylactic vaccines based on L1 virus-like particles have been considered as an effective prevention method. However, existing recombination vaccines are too expensive for developing countries. DNA vaccines might be a lower-cost and effective alternative. In this study, a plasmid (pcDNA3.1-HPV16-L1) and a co-expressing plasmid (pcDNA3.1-HPV16-L1-siE6) carried by attenuated Salmonella were constructed and their prevention and treatment effect on cervical cancer were observed, respectively. The results showed that pcDNA3.1-HPV16-L1 carried by attenuated Salmonella could induce the production of HPV16-L1 antibodies, IL-2 and INF-γ in mice serum, which presented its prevention effect on HPV. Subsequently, E6 and E7 gene silencing by pCG-siE6 inhibited the growth of cervical cancer both in vitro and in vivo. Furthermore, L1 up-regulation and E6/E7 down-regulation caused by co-expressing plasmid (pcDNA3.1-HPV16-L1-siE6) contributed to a significant anti-tumor effect on the mice. This study suggests that pcDNA3.1-HPV16-L1-siE6 carried by attenuated Salmonella has a synergistic effect of immune regulation and RNA interference in cervical cancer treatment.

Highlights

Human papillomavirus (HPV) infection is the major etiological factor for cervical cancer
These results indicated that HPV16-L1 protein was successfully expressed and formed into self-assembly virus-like particles (VLPs) in BHK cells
After being treated by attenuated Salmonella carrying pcDNA3.1-HPV16-L1 plasmid, the serum and genital secretions of mice were collected for enzyme-linked immunosorbent assay (ELISA) assay

Summary

Introduction

Human papillomavirus (HPV) infection is the major etiological factor for cervical cancer. HPV prophylactic vaccines based on L1 virus-like particles have been considered as an effective prevention method. A plasmid (pcDNA3.1HPV16-L1) and a co-expressing plasmid (pcDNA3.1-HPV16-L1-siE6) carried by attenuated Salmonella were constructed and their prevention and treatment effect on cervical cancer were observed, respectively. This study suggests that pcDNA3.1-HPV16-L1-siE6 carried by attenuated Salmonella has a synergistic effect of immune regulation and RNA interference in cervical cancer treatment. Three HPV prophylactic vaccines based on L1 VLPs have been widely used in developed countries and showed a desired reduction of 38% in high grade d ysplasia[9]. Many studies showed that silencing E6 and/or E7 gene by small interference RNA (siRNA) can significantly inhibit the development of cervical cancer in vitro or in vivo[13,14,15]. A previous study testified that a HPV16-L1 expressing plasmid carried by attenuated Salmonella (Ty21a) successfully induced HPV16 neutralizing antibodies in serum and genital secretions in mice m odel[10]

Methods

Results

Conclusion