Portable SPR proved its value in evaluating a novel vaccine platform — demonstrating that high-quality binding data doesn't require a fixed benchtop instrument.
Traditional vaccine platforms such as the flu vaccine are primarily based on the growth of viruses in chicken eggs, which is time consuming (takes more than 6 months) and the process is tedious. Furthermore, it is no more than 50% effective due to the ability of influenza viruses to mutate rapidly. The emergency use of mRNA-based vaccines to stem the spread of COVID-19 has been a huge game changer in vaccine production.
In an effort to discover a cost-effective vaccine that also offers broad and long-lasting protection against the influenza virus, there has been a focus on an alternative vaccine platform based on a rod-shaped nanoparticle composed of the coat protein of a plant virus called the papaya mosaic virus (PapMV) that self-assembles around an ssRNA, which is then fused with a peptide from the influenza virus. This strategy has been shown to trigger specific immune responses, resulting in 100% survival rate in mice studies.
SPR Experimental Details
Two batches of serum samples were prepared for this experiment from the same group of mice — serum samples drawn before immunization (pre-immunized) and after immunization (immunized). The mice were immunized with the PapMV nanoparticle that was fused with the m2 peptide, a peptide that is part of a conserved protein of the influenza virus.
The P4SPR gold sensor chips were functionalized with Afficoat™, a self-assembled monolayer that serves both as a covalent linker and a coating that minimizes non-specific protein adsorption. The PapMV nanoparticles were immobilized onto Afficoat-functionalized chips by using NHS and EDC chemistries.
Comparison of Pre-Immunized and Immunized Mice Sera
Immunized mice had serum that contained higher levels of antibodies, demonstrating that the use of the PapMV-m2 peptide vaccine platform was effective in eliciting a heightened immune response. These data also show that the P4SPR can differentiate the level of antibodies between the two types of samples while immersed in a complex matrix, i.e. mouse serum.
The entire set of sensorgrams took about 40 min to obtain once the baseline was stabilized. With these data on hand, it is also possible to estimate the KD for the PapMV and antibody interactions using the SPR shift at equilibrium from each dilution.
Conclusions
P4SPR is a simple SPR system that can be used to evaluate the humoral effects of a novel vaccine platform in mice. The immobilization steps were straightforward and the generation of SPR data could be obtained quickly even for complex biological samples such as mouse serum.
References
[1] Bolduc M, et al. The quest for a nanoparticle-based vaccine inducing broad protection to influenza viruses. Nanomed.: Nanotechnol., Biol., and Med., 2018, 14, 2563–257.
[2] Laliberté-Gagné ME, et al. Modulation of Antigen Display on PapMV Nanoparticles Influences Its Immunogenicity. MDPI Vaccines 2021, 9, 33.