Engineering of papaya mosaic virus (PapMV) nanoparticles with a CTL epitope derived from influenza NP.

J Nanobiotechnology. 2013 Apr 4;11:10.

Babin C, Majeau N, Leclerc D.

Department of Microbiology, Infectiology and Immunology, Infectious Disease Research Center, Laval University, 2705 boul. Laurier, Quebec city, PQ G1V 4G2, Canada.

Abstract

BACKGROUND: The ever-present threat of infectious disease, e.g. influenza pandemics, and the increasing need for new and effective treatments in immunotherapy are the driving forces that motivate research into new and innovative vaccine platforms. Ideally, such platforms should trigger an efficient CTL response, be safe, and easy to manufacture. We recently developed a novel nanoparticle adjuvant comprised of papaya mosaic virus (PapMV) coat protein (CP) assembled around an RNA. The PapMV nanoparticle is an efficient vaccine platform in which the peptide antigen is fused to the C-terminus of the PapMV CP, leading to nanoparticles presenting surface-exposed epitope. The fusion stabilizes the epitope and improves its immunogenicity. We found recently that C-terminal fusions are not always efficient, depending on the nature of the peptide fused to the platform.

RESULTS: We chose a CTL epitope derived from the nucleocapsid (NP) of influenza virus (NP147-155) for this proof-of-concept demonstration. Recombinant nanoparticles harbouring a fusion at the N-terminus were more efficient in triggering a CTL response. Efficacy appeared to be linked to the stability of the nanoparticles at 37°C. We also showed that discs–smaller than nanoparticles–made of 20 subunits of PapMV CP are less efficient for induction of a CTL response in mice, revealing that assembly of the recombinant PapMV CP into nanoparticles is crucial to triggering an efficient CTL response.

CONCLUSION: The point of fusion on the PapMV vaccine platform is critical to triggering an efficient CTL response. Efficacy is linked to nanoparticle stability; nanoparticles must be stable at 37°C but remain susceptible to cellular proteases to ensure efficient processing of the CTL epitope by cells of the immune system. The results of this study improve our understanding of the PapMV vaccine platform, which will facilitate the design of efficient vaccines to various infectious threats.

PMID: 23556511

 

Supplementary

The manuscript of Babin et al., focuses on the refinement of the fusion of a CTL epitope on the PapMV vaccine platform. This study revealed the importance to maintain the native structure of the PapMV CP when a fusion is made directly to this protein scaffold. The nature (hydrophobic or charged), the length (up to 40 amino acids were successfully fused to the PapMV CP) and the site of fusion of the peptide to the CP can all impact on the structure. The N and the C-terminus of the PapMV CP were shown to be the easiest and more successful point of fusion so far. Even if almost all the entire 3D structure of the PapMV CP is known, it is still difficult to predict in silico the impact of a given fusion on the ability of the recombinant protein to self assemble into nanoparticles. Therefore, we concluded that the only way to evaluate if the vaccine platform can accommodate a fusion is to produce the recombinant protein and perform the assembly in the laboratory.

This paper also revealed that the stability of the recombinant nanoparticle that present the epitope is as important for the trigger of a CTL response (CD8+ mediated) than for a humoral response (antibodies)(Rioux et al., 2012). This is remarkable because the pathways of activation of those two arms of the immune system are intrinsically very different and based on different cell types (B vs CD8+ cells). Nevertheless, their activation can be largely influence by CD4+ T cells, which is likely to play a key role in the immune response triggered with this vaccine platform.

This vaccine platform has a very promising future for the development of peptide based vaccine that can trigger both arms of the immune system, the humoral and the CTL response with the proper antigen and applications can be developed to most infectious diseases and cancer.

Denis Leclerc-1Figure 1. PapMV nanoparticle is a versatile vaccine platform. Optimized fusion of a B cell or a CTL epitope to the PapMV CP are used to generate recombinant nanoparticles that are very immunogenic. They can be used to immunized mice and induce either a humoral or a CTL response depending on the nature of the peptide fused to its surface. Recombinant nanoparticles become an efficient vaccine that can be used to fight infectious disease and cancer.

 

Reference:

Rioux, G., Babin, C., Majeau, N. and Leclerc, D. (2012). Engineering of papaya mosaic virus (PapMV) nanoparticles through fusion of the HA11 peptide to several putative surface-exposed sites. Plos One 7:e31925.

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