Method for preparing foot-and-mouth disease virus-like particles

A method for preparing serotype 0 FMDV-like particles, the method comprising:

• 1) amplifying a smt3 gene from a genome of Saccharomyces cerevisiae strain EGY48, enzymatically cleaving the amplified smt3 gene and a pET-28a vector using Nco I and BamH I, inserting the cleaved smt3 gene into the cleaved pET-28a vector to obtain a small ubiquitin-like modifier (SUMO) fusion expression vector pSM1, and replacing the kanamycin resistance gene of the pSM1 with an ampicillin resistance gene to obtain a SUMO fusion expression vector pSM2;
• 2) designing primers based on a porcine serotype 0 FMDV, extracting a viral RNA from the porcine serotype 0 FMDV, and performing reverse transcription and amplification to yield genes VP0, VP3, and VP1, wherein an upstream primer and a downstream primer for VP0 amplification have sequences of SEQ ID NO:
• 3 and SEQ ID NO:
• 4, respectively;
• an upstream primer and a downstream primer for VP3 amplification have sequences of SEQ ID NO:
• 7 and SEQ ID NO:
• 8, respectively;
• and an upstream primer and a downstream primer for VP1 amplification have sequences of SEQ ID NO:
• 5 and SEQ ID NO:
• 6, respectively;
• the upstream primer for VP0 amplification, the upstream primer for VP3 amplification, and the upstream primer for VP1 amplification each comprise a BsmB I restriction site;
• and the downstream primer for VP0 amplification, the downstream primer for VP3 amplification, and the downstream primer for VP1 amplification each comprise a BamH I restriction site;
• 3) enzymatically cleaving the genes VP0, VP3, and VP1 using BsmB I/BamH I respectively to yield corresponding fragments, enzymatically cleaving the vectors pSM1, pSM2, and pSM1 using Bsa I, inserting the fragments into the cleaved vectors pSM1, pSM2, and pSM1 to obtain recombinant expression vectors pSM1/VP0, pSM2/VP3, and pSM1/VP1, respectively, wherein the recombinant expression vectors pSM1/VP0, pSM2/VP3, and pSM1/VP1 each comprise the smt3 gene;
• 4) performing amplification by using the recombinant expression vector pSM1/VP1 as a template and T7BamH I primer and VP1Xho I primer to obtain a DNA fragment, wherein the DNA fragment comprises the VP1 gene and a prokaryotic expression element, the prokaryotic expression element comprises a T7 promoter;
• the T7BamH I primer has a sequence of SEQ ID NO:
• 9;
• and the VP1Xho I primer has a sequence of SEQ ID NO:
• 10;
• 5) enzymatically cleaving the DNA fragment from 4) and the recombinant expression vector pSM1/VP0 using BamH I/Xho I, inserting the cleaved DNA fragment into the cleaved recombinant expression vector pSM1/VP0 to obtain a recombinant co-expression vector pSM1/VP0-VP1;
• 6) co-transforming the recombinant expression vector pSM2/VP3 from 3) and the recombinant co-expression vector pSM1/VP0-VP1 from 5) into competent cells BL21-CodonPlus (DE3)-RIL, picking a monoclonal colony, and inoculating and culturing the monoclonal colony in a medium containing ampicillin, kanamycin, and chloramphenicol to obtain a bacterial suspension;
• 7) adding isopropyl β-D-1-thiogalactopyranoside(IPTG) to the bacterial suspension at a concentration of 0.5 mmol/L, allowing bacterial expression for 16 hrs, collecting bacterial cells from the bacterial suspension, suspending the bacterial cells in a buffer, ultrasonicating the bacterial cells, and centrifuging to obtain the recombinant proteins in the supernatant;
• and
• 8) purifying the recombinant proteins of 7) and collecting a liquid comprising VP0, VP1, and VP3 proteins, dialyzing the liquid against the dialysis buffer PBS to assemble the VP0, VP1, and VP3 proteins to yield serotype 0 FMDV-like particles.