Increased Immunogenicity of Full-Length Protein Antigens through Sortase-Mediated Coupling on the PapMV Vaccine Platform.

Marie-Ève Laliberté-Gagné,Jérome Estaquier,Pierre Savard,Marilène Bolduc,Philippe Casault,Ariane Thérien,Denis Leclerc,Caroline Garneau

doi:10.3390/vaccines7020049

Abstract

Background: Flexuous rod-shape nanoparticles—made of the coat protein of papaya mosaic virus (PapMV)—provide a promising vaccine platform for the presentation of viral antigens to immune cells. The PapMV nanoparticles can be combined with viral antigens or covalently linked to them. The coupling to PapMV was shown to improve the immune response triggered against peptide antigens (<39 amino acids) but it remains to be tested if large proteins can be coupled to this platform and if the coupling will lead to an immune response improvement. Methods: Two full-length recombinant viral proteins, the influenza nucleoprotein (NP) and the simian immunodeficiency virus group-specific protein antigen (GAG) were coupled to PapMV nanoparticles using sortase A. Mice were immunized with the nanoparticles coupled to the antigens and the immune response directed to the antigens were analyzed by ELISA and ELISPOT. Results: We showed the feasibility of coupling two different full-length proteins (GAG and NP) to the nanoparticle. We also showed that the coupling to PapMV nanoparticles improved significantly the humoral and the cytotoxic T lymphocyte (CTL) immune response to the antigens. Conclusion: This proof of concept demonstrates the versatility and the efficacy of the PapMV vaccine platform in the design of vaccines against viral diseases.

Highlights

Recent advances in vaccinology lead to the development of subunit vaccines, in replacement of the traditional live attenuated or inactivated vaccines, to ease and accelerate manufacturing and to maximize safety
We showed that coupling to the nanoparticle significantly enhanced the antibody and the cellular cytotoxic T lymphocyte (CTL) immune responses directed toward the coupled large protein antigens, showing the potential of this technology in the design of vaccines to viral diseases
Tag, was only available for reaction with SrtA on the extremities of the nanoparticle. This arrangement preserves the surface of the nanoparticle, which is probably involved in the immune enhancement properties of the papaya mosaic virus (PapMV) nanoparticles as previously described [7]

Summary

Introduction

Recent advances in vaccinology lead to the development of subunit vaccines, in replacement of the traditional live attenuated or inactivated vaccines, to ease and accelerate manufacturing and to maximize safety One drawback of this strategy is the weak immunogenicity of the subunit vaccines and the multiple injections necessary for reaching protective antibody titers. To alleviate this problem, the multimerization of recombinant antigens onto nanoparticles was shown to increase both antigen immunogenicity and stability [1,2,3,4]. We showed that the coupling to PapMV nanoparticles improved significantly the humoral and the cytotoxic T lymphocyte (CTL)

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