An attenuated African swine fever virus expressing the E2 glycoprotein of classical swine fever virus protects pigs against challenge of both viruses

African swine fever (ASF) and classical swine fever (CSF) are highly contagious diseases with high morbidity and mortality rates resulting in an enormous impact on the global pig industry. A bivalent vaccine that simultaneously protects against both ASF and CSF is highly desirable. We previously developed a seven-gene-deleted African swine fever virus (ASFV) attenuated vaccine candidate (HLJ/18-7GD) that provides complete protection against homologous strains. Herein, we constructed a recombinant virus HLJ/18-7GD-E2 by inserting the classical swine fever virus (CSFV) E2 gene into the HLJ/18-7GD via homologous recombination. After continuous in vitro passaging, Western blotting analysis showed that the E2 gene was expressed and stably maintained within the ASFV genome. Next, the immunogenicity and protective efficacy of the recombinant HLJ/18-7GD-E2 virus was evaluated in pigs. The results revealed that a single dose of 106 TCID50 of HLJ/18-7GD-E2 induced an efficient immune response and provided complete protection against lethal challenges with ASFV or CSFV. These results demonstrate that recombinant ASFV expressing the CSFV E2 protein has potential as a bivalent live attenuated vaccine, providing solid protection against ASFV and CSFV infection in pigs.