Construction And Characteristics Of PH Sensitive Murine Polyomavirus Virus-like Particle

pH-sensitive nanoparticles have a wide range of applications in various fields such as drug delivery systems.Virus-like particle（VLP）has abundant modifiable sites at surface,nanoscale cavity structure and good biocompatibility.It is convenient to regulate the structure through the modification of structural proteins.Therefore,a pH-sensitive VLP was constructed by introducing charged fragments into wild-type VLP as pH-sensitive modules.Firstly,a negatively charged VP1（m-VP1）was constructed by introducing eight aspartic acid into the HI loop of the structural protein（VP1）of murine polyomavirus（MPV）,while a positively charged VP1（m+VP1）was constructed by eight arginine.The recombinant plasmids pQE-80L-wtVP1,pQE-80L-m-VP1 and pQE-80L-m+VP1were constructed and transformed into E.coli to express wtVP1,m-VP1 and m+VP1.The expression condition was optimized.Induction of 22 h was started when the OD₆₀₀ value of the broth was approximately 0.5,using 0.6 mmol/L IPTG.The yield of purified m-VP1,m+VP1 and wild-type VP1（wtVP1）was 80.0 mg/（L medium）,77.4mg/（L medium）and 113.2 mg/（L medium）,respectively.The self-assembly of VP1 to VLP was then examined.Successful assembly into mutant VLP（mVLP）with a particle size of 40-50 nm was observed using equimolecular mixture of m-VP1 and m+VP1.The morphology and size of mVLP was consistent with wild-type VLP（wtVLP）.Moreover,the change of OD₃₅₀ during self-assembly indicated that the best self-assembly of mVLP was obtained at pH 8.0,with a higher efficiency than wtVLP.Self-assembly efficiency decreased when pH deviated from this value,confirming that mVLP has pH sensitivity and the pH-sensitive MPV VLP has been successfully constructed.