Pentablock Copolymer Micelle Nanoadjuvants Enhance Cytosolic Delivery of Antigen and Improve Vaccine Efficacy while Inducing Low Inflammation

Abstract

As the focus has shifted from traditional killed or live, attenuated vaccines towards subunit vaccines, improvements in vaccine safety have been confronted with low immunogenicity of protein antigens. This issue has been addressed by synthesizing and designing a wide variety of antigen carriers and adjuvants, such as Toll-like receptor agonists (e.g., MPLA, CpG). Studies have focused on optimizing adjuvants for improved cellular trafficking, cytosolic availability, and improved antigen presentation. In this work, we describe the design of novel amphiphilic pentablock copolymer (PBC) adjuvants that exhibit high biocompatibility and reversible pH-and temperature-sensitive micelle formation. We demonstrate improved humoral immunity in mice in response to single dose immunization with PBC micelle adjuvants compared to soluble antigen alone. With the motive of exploring the mechanism of action of these PBC micelles, we studied intracellular trafficking of these PBC micelles with a model antigen and demonstrated that the PBC micelles associate with the antigen and enhance its cytosolic delivery to antigen presenting cells. We posit that these PBC micelles operate via immune-enhancing mechanisms that are different from that of traditional Toll-like receptor activating adjuvants. The metabolic profile of antigen presenting cells stimulated with traditional adjuvants and the PBC micelles also suggests distinct mechanisms of action. A key finding from this study is the low production of nitric oxide and reactive oxygen species by antigen presenting cells when stimulated by PBC micelle adjuvants in sharp contrast to TLR adjuvants. Together, these studies provide a basis for rationally developing novel vaccine adjuvants that are safe, that induce low inflammation, and that can efficiently deliver antigen to the cytosol.

Self-assembling synthetic nanoadjuvant scaffolds cross-link B cell receptors and represent new platform technology for therapeutic antibody production

“…This process involves the crosslinking of the BCRs by repetitive or complexed/aggregated Ag, which would up-regulate Nur77 expression. Our studies demonstrated that PBC micelles, shown previously to associate with Ag (16,33), can facilitate cross-linking of BCRs, resulting in B cell activation. We first investigated the interaction of the PBC micelle-Ag complexes with the BCRs by analyzing Nur77 expression.…”

Single dose combination nanovaccine provides protection against influenza A virus in young and aged mice

“…56 Therefore, the inclusion of micelles and CDNs, which induce high antibody titers early postimmunization, are beneficial co-adjuvants. 19,20,23 Finally, the micelles may provide a depot of antigens and/or nanoadjuvants and encourage delivery of antigen to the cytosol. 20 These nanoadjuvants used concomitantly set the stage for the development of an efficacious single dose influenza virus nanovaccine for older adults.…”

“…In contrast, we did not observe any significant upregulation of the cell surface markers when stimulated with micelles, which is consistent with our previous findings in young splenic DCs. 20 Additionally, two sub-populations of conventional DCs were analyzed: CD8α + (Fig. 5B) and CD103 + (Fig.…”

“…4 Similarly, pentablock copolymers based on Pluronic F127 and polydiethylaminoethyl methacrylate (PDEAEM) represent another effective platform for affording sustained release of antigen, depositing the antigen in the cytosol, and promoting the rapid development of antibody titers. 19,20 Our previous work has shown that combination nanovaccines consisting of both polyanhydride nanoparticles and pentablock copolymers provided the greatest protection against influenza in young mice compared to either nanoadjuvant alone. 21 That being said, older adults often require vaccines which stimulate the immune system without exacerbating the already inflamed state.…”

Polymeric nanoparticle vaccines to combat emerging and pandemic threats

“…Amphiphilic polymers are able to undergo self-assembly in an aqueous solution, forming particulate micellar nanosystems with diameters ranging from 13 nm [ 205 ] to 150 nm [ 206 ]. The micelles consist of a hydrophobic polymer core conjugated to a hydrophilic polymer constituting the shell, which have been utilized either as an adjuvant [ 207 ] or as a nanocarrier for antigens [ 151 , 206 , [208] , [209] , [210] ] as well as for co-delivery of molecular adjuvants and antigens [ [211] , [212] , [213] , [214] ]. The hydrophilic polymer shells are mostly formed using PEG to provide colloidal stability, as well as to reduce retention at the injection site and improve lymphatic trafficking to the draining LNs [ 215 ].…”