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

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.

Better Adjuvants for Better Vaccines: Progress in Adjuvant Delivery Systems, Modifications, and Adjuvant–Antigen Codelivery

“…Influenza M2e peptide was conjugated with PapMV coat-protein (CP) by Sortase A to obtain an antigen-adjuvant complex with good immune response [119]. In another study, the PapMV CP and full-length influenza nucleoprotein were covalently coupled with Sortase A, and the resulting complex induced stronger cellular and humoral immunity [120]. The TLR2 agonist FSL-1 was coupled to the surface of group A streptococcal recombinant protein using Sortase A.…”

Recent Advances in the Use of Plant Virus-Like Particles as Vaccines

“…As alternatives to genetic fusions, other approaches can result in antigen presentation, such as chemical coupling or physical binding of the antigen to the VLP surface using binding partner molecules. Successful examples of the generation of vaccines using the chemical or enzymatic coupling of whole antigens include studies of experimental vaccines against Francisella tularensis [42], influenza [43], Yersinia pestis [44], Plasmodium vivax [45], and Zika virus [46].…”

Modulation of Antigen Display on PapMV Nanoparticles Influences Its Immunogenicity

“…To circumvent this problem, a novel approach, in which the peptide is fused directly onto self-assembled nanoparticles [ 32 , 33 ] using a bacterial transpeptidase—sortase A (SrtA)—was developed [ 34 , 35 ]. This approach is more flexible than genetic fusion to the CP, and it allows the fusion of larger peptides (>39 amino acids) [ 33 ] and even full-length proteins [ 35 ]. In each case, attachment of the antigens to the PapMV vaccine platform significantly improved the humoral and/or the CD8+ -mediated immune response to the coupled peptide antigen [ 33 , 35 ].…”

“…This approach is more flexible than genetic fusion to the CP, and it allows the fusion of larger peptides (>39 amino acids) [ 33 ] and even full-length proteins [ 35 ]. In each case, attachment of the antigens to the PapMV vaccine platform significantly improved the humoral and/or the CD8+ -mediated immune response to the coupled peptide antigen [ 33 , 35 ]. The SrtA enzyme joins the receptor motif (LPETGG), genetically fused to the PapMV CP (PapMV-C), to the donor motif provided by the antigen (repeated G motif) [ 33 , 35 , 36 ] generating a candidate vaccine.…”