Engineered MS2 Virus Capsids for Cellular Display of Peptide Antigens

ABSTRACT Our ability to respond to emerging pandemics and pathogen resistance relies critically on our ability to build vaccines quickly and efficiently. In this report we used an efficient enzymatic oxidative coupling reaction to create a viral capsid-based vaccine platform that is modular and quickly adaptable for many different pathogens. Tyrosinase-mediated oxidative coupling was used to conjugate C-terminal tyrosine residues on peptide antigens to cysteine residues installed inside MS2 viral capsids. This strategy is particularly promising because the capsids protect the internally conjugated peptides from protease degradation before they are delivered into cells. The vaccine constructs were tested for MHC presentation followed by T-cell activation. Mutants of the MS2 capsid itself activated DC2.4 cells, serving as an adjuvant to help induce the immune response to delivered antigens. The MS2-peptide constructs were shown to be stable in serum, activate DC2.4 cells, and lead to MHC-presentation of peptide antigens with subsequent activation of antigen-specific T-cell hybridomas. Taken together, these results demonstrate effective activation of the adaptive immune system in vitro. This synthetic platform can be used to build new vaccines for many different diseases for which immunodominant peptide antigens are known because the antigens can be quickly interchanged while the MS2 scaffold remains the same. Additionally, this platform allows for multiple peptide antigens to be delivered simultaneously in each capsid, which could provide enhanced immunity against resistant strains and be useful for cancer vaccine development. Competing Interest Statement MBF has a financial interest in Catena Bio-sciences, which has licensed the technology used to make the conjugates described here-in, and both he and the company may benefit from commercializa-tion of the results of this research. Footnotes This version of the manuscript has been revised to add further studies demonstrating site-selectivity of the MS2-peptide conjugation, to compare conjugation efficiencies measured using SDS-PAGE and MS, and to add DLS measurements of the constructs. Additionally, further comments and explanations have been given to better introduce and explain important immunological concepts involved in this work.