Sequencing p72 gene of field strain of African swine fever virus (ASFV) in Vietnam and generation of enhanced immunogenic fusion protein G-p72 potentially expressed as a recombinant antigen in ASFV subunit vaccine

Protein p72 is the major surface protein of African swine fever virus (ASFV), which is immunogenic and can prime the host to elicit a protective immune response, while G protein is the surface glycoprotein of vesicular stomatitis virus (VSV), which is well-known to be a strong antigen to stimulate an effective humoral immunity. The aim of this study was to sequence full length p72 gene of a field strain of ASFV causing typical ASF in Dong Nai province in 2020 and fuse this p72 gene with VSV G gene to generate a recombinant fusion gene G-p72 that could simultaneously express both proteins and stimulate a better host immune response than p72 expression alone. The sequence of the gene showed 99.59% nucleotide sequence similarity to an ASFV isolate from China. The PCR was employed to produce the recombinant G-p72 gene, which was cloned into plasmid pET28a, followed by transformation into E. coli BL21 (DE3) for protein expression. The G-p72 expression was induced at 37°C and 28°C for 6 and 16 h, respectively. The expression showed that G-p72 was observed at 28°C for 16 h. In summary, the full length p72 gene of a field strain of ASFV was successfully sequenced and expressed as the recombinant G-p72 protein in E. coli BL21 (DE3). The expression level of the G-p72 fusion should be optimized and the immunogenicity of the recombinant protein should be examined in futher studies.