Incorporation of Escherichia coli heat-labile enterotoxin B subunit into rabies virus particles enhances its immunogenicity in mice and dogs

•Scientific question: To reduce and eliminate the rabies epidemic, it is essential to improve the effectiveness of the rabies vaccine.•Evidence before this study: Many studies have demonstrated that adjuvants, particularly molecular adjuvants targeting the immune cells, play an important role in improving the immune efficacy of inactivated vaccines. Escherichia coli heat-labile enterotoxin B subunit (LTB) shows advantages in promoting the immune efficacy of vaccines by activating the dendritic cells.•New findings: A recombinant virus rCVS11-LTB was constructed in this study, which could display the LTB protein on the surface of viral particles. Inactivated rCVS11-LTB was able to induce the higher levels of virus-neutralizing antibodies (VNAs) in both mice and dogs, and to induce faster and stronger cellular immune responses and the production of CD4+ CTM in mice than rCVS11 post immunization. In addition, two doses of inactivated rCVS11-LTB could completely protect the mice from the challenge with a lethal dose of rabies virus.•Significance of the study: The recombinant virus rCVS11-LTB chimeric-expressing the molecular adjuvant LTB can induce high levels of humoral and cellular immune responses in vivo and provide 100% protection against RABV challenge in mice, demonstrating its potential as an effective inactivated rabies vaccine candidate. Although inactivated vaccines against rabies have the advantage of high safety, effective protection against rabies virus (RABV) infection often requires multiple, high-dose immunization. Incorporating a molecular adjuvant into the viral particles has been found to be a useful strategy to promote the immune effectiveness of inactivated vaccines. In this study, we constructed a recombinant virus, rCVS11-LTB, which chimerically expresses a molecular adjuvant heat-labile enterotoxin B subunit (LTB) protein on the surface of the RABV particles. Immunogenicity in vivo was found to be promoted by rCVS11-LTB through the activation of dendritic cells (DCs). Our results demonstrated that inactivated rCVS11-LTB was able to induce higher levels of virus-neutralizing antibodies (VNAs) in both mice and dogs than the parent virus rCVS11, to enhance the cellular immune response and T cell immune memory in mice, and was also able to provide 100% protection in mice from lethal doses of rabies virus, indicating its potential as a safe and effective inactivated rabies vaccine candidate.