Rational Design of pH Sensitive MS2 Virus‐Like Particles for Drug Delivery Applications

Abstract

Virus‐like particles (VLPs) have emerged as promising drug delivery and imaging scaffolds. VLPs made from the MS2 Bacteriophage Coat Protein (CP) enter cells via receptor‐mediated endocytosis and are believed to accumulate in the endosomal pathway. This pathway involves a decrease in pH levels that can potentially trigger the disassembly of acid sensitive VLPs, leading to cargo release. However, MS2 CPWT VLPs are highly stable in the endosomal pH range (4.5–5.5), which could slow endosomal release of cargo within the cell. Here, we set out to identify an acid‐sensitive variant of the MS2 CP that could lead to faster cargo release in the acidic environment of the endosome. We identified a previously‐unknown double mutant, CPT71H/E76C, that exhibits significant acid sensitivity in vitro at the endosomal pH range, in contrast to MS2 CPWT. The population of CPT71H/E76C VLPs was measured after a 4 h incubation at 37°C in a pH range from 1.0 to 7.3 with High Performance Liquid Chromatography using a Size Exclusion Chromatography column (HPLC‐SEC). Acid screens showed CPT71H/E76C to have 50% less well‐formed VLP at pH 4.9. These mutations alter a key hydrogen bond interaction, which could be the reason for increased acid sensitivity. To explore this hypothesis, capsids were alkylated with N‐ethylmaleimide, a moiety that could restore the hydrogen bond between the residues, and screen for acid sensitivity. Results showed modified capsids had an acid sensitivity similar to CPT71H, suggesting the hydrogen bond is involved in this property. Acid sensitive CPT71H/E76C could potentially improve the delivery of drugs to cancer cells.Support or Funding InformationNIH‐ MARC (5T34GM007821‐38) and the Amgen Scholars FoundationThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.