Overcoming Symmetry Mismatch in Vaccine Nanoassembly through Spontaneous Amidation

SpyMask enables combinatorial assembly of bispecific binders

Bispecific antibodies are a successful and expanding therapeutic class. Standard approaches to generate bispecifics are complicated by the need for disulfide reduction/oxidation or specialized formats. Here we present SpyMask, a modular approach to bispecifics using SpyTag/SpyCatcher spontaneous amidation. Two SpyTag-fused antigen-binding modules can be precisely conjugated onto DoubleCatcher, a tandem SpyCatcher where the second SpyCatcher is protease-activatable. We engineer a panel of structurally-distinct DoubleCatchers, from which binders project in different directions. We establish a generalized methodology for one-pot assembly and purification of bispecifics in 96-well plates. A panel of binders recognizing different HER2 epitopes were coupled to DoubleCatcher, revealing unexpected combinations with anti-proliferative or pro-proliferative activity on HER2-addicted cancer cells. Bispecific activity depended sensitively on both binder orientation and DoubleCatcher scaffold geometry. These findings support the need for straightforward assembly in different formats. SpyMask provides a scalable tool to discover synergy in bispecific activity, through modulating receptor organization and geometry.

SpyTag/SpyCatcher display of influenza M2e peptide on norovirus-like particle provides stronger immunization than direct genetic fusion

Introduction

Virus-like particles (VLPs) are similar in size and shape to their respective viruses, but free of viral genetic material. This makes VLP-based vaccines incapable of causing infection, but still effective in mounting immune responses. Noro-VLPs consist of 180 copies of the VP1 capsid protein. The particle tolerates C-terminal fusion partners, and VP1 fused with a C-terminal SpyTag self-assembles into a VLP with SpyTag protruding from its surface, enabling conjugation of antigens via SpyCatcher.

Methods

To compare SpyCatcher-mediated coupling and direct peptide fusion in experimental vaccination, we genetically fused the ectodomain of influenza matrix-2 protein (M2e) directly on the C-terminus of norovirus VP1 capsid protein. VLPs decorated with SpyCatcher-M2e and VLPs with direct M2 efusion were used to immunize mice.

Results and discussion

We found that direct genetic fusion of M2e on noro-VLP raised few M2e antibodies in the mouse model, presumably because the short linker positions the peptide between the protruding domains of noro-VLP, limiting its accessibility. On the other hand, adding aluminum hydroxide adjuvant to the previously described SpyCatcher-M2e-decorated noro-VLP vaccine gave a strong response against M2e. Surprisingly, simple SpyCatcher-fused M2e without VLP display also functioned as a potent immunogen, which suggests that the commonly used protein linker SpyCatcher-SpyTag may serve a second role as an activator of the immune system in vaccine preparations. Based on the measured anti-M2e antibodies and cellular responses, both SpyCatcher-M2e as well as M2e presented on the noro-VLP via SpyTag/Catcher show potential for the development of universal influenza vaccines.

On-Demand Dynamic Chirality Selection in Flower Corolla-like Micropillar Arrays

Chiral morphology has been intensively studied in various fields including biology, organic chemistry, pharmaceuticals, and optics. On-demand and dynamic chiral inversion not only cannot be realized in most intrinsically chiral materials but also has mostly been limited to chemical or light-induced methods. Herein, we report reversible real-time magneto-mechanical chiral inversion of a three-dimensional (3D) micropillar array between achiral, clockwise, and counterclockwise chiral arrangements. Inspired by the flower corolla, achiral arrays of five and six radially arranged semicylindrical micropillars were employed as model systems to investigate the dynamic symmetry properties of arrays consisting of odd and even numbers of micropillars, respectively. Each micropillar underwent twisting actuation with a different twisting angle depending on the angle with the magnetic field direction and magnetic flux density, thereby collectively changing the chirality from the achiral to chiral state. Importantly, the morphological handedness of the micropillars was inverted within a few seconds by manipulating the direction of the magnetic field. A chiral morphology consisting of magnetically twisted micropillars was shape-fixed by the introduction of a polymeric binder. This binder could be simply washed off to return the shape-fixed twisted micropillars to their initial straight state. Magnetically programmable and reproducible 3D flower corolla-like micropillar arrays are expected to expand the potential of shape-reconfigurable devices that require real-time chiral manipulation in ambient environments.

Development of a synthetic nanoparticle vaccine presenting the HIV-1 envelope glycoprotein

Two-component self-assembling virus-like particles (VLPs) are promising scaffolds for achieving high-density display of HIV-1 envelope (gp140) trimers, which can improve the induction of neutralising antibodies (NAbs). In this study gp140 was displayed on the surface of VLPs formed by the AP205 phage coat protein. The CAP256 SU gp140 antigen was selected as the patient who this virus was isolated from developed broadly neutralising antibodies (bNAbs) shortly after superinfection with this virus. The CAP256 SU envelope is also sensitive to several bNAbs and has shown enhanced reactivity for certain bNAb precursors. A fusion protein comprising the HIV-1 CAP256 SU gp140 and the SpyTag (ST) (gp140-ST) was produced in HEK293 cells, and trimers were purified to homogeneity using gel filtration. SpyCatcher (SC)-AP205 VLPs were produced inEscherichia coliand purified by ultracentrifugation. The gp140-ST trimers and the SC-AP205 VLPs were mixed in varying molar ratios to generate VLPs displaying the glycoprotein (AP205-gp140-ST particles). Dynamic light scattering, negative stain electron microscopy and 2D classification indicated that gp140-ST was successfully bound to the VLPs, although not all potential binding sites were occupied. The immunogenicity of the coupled VLPs was evaluated in a pilot study in rabbits. One group was injected four times with coupled VLPs, and the second group was primed with DNA vaccines expressing Env and a mosaic Gag, followed by modified vaccinia Ankara expressing the same antigens. The animals were then boosted twice with coupled VLPs. Encouragingly, gp140-ST displayed on SC-AP205 VLPs was an effective boost to heterologously primed rabbits, leading to induction of autologous Tier 2 neutralising antibodies in 2/5 rabbits. However, four inoculations of coupled VLPs alone failed to elicit any Tier 2 antibodies. These results demonstrate that the native-like structure of HIV-1 envelope trimers and selection of a geometrically-suitable nanoparticle scaffold to achieve a high-density display of the trimers are important considerations that could improve the effect of nanoparticle-displayed gp140.

N-Terminal Modification of Gly-His-Tagged Proteins with Azidogluconolactone

Site-specific protein modifications are vital for biopharmaceutical drug development. Gluconoylation is a non-enzymatic, post-translational modification of N-terminal HisTags. We report high-yield, site-selective in vitro α-aminoacylation of peptides, glycoproteins, antibodies, and virus-like particles (VLPs) with azidogluconolactone at pH 7.5 in 1 h. Conjugates slowly hydrolyse, but diol-masking with borate esters inhibits reversibility. In an example, we multimerise azidogluconoylated SARS-CoV-2 receptor-binding domain (RBD) onto VLPs via click-chemistry, to give a COVID-19 vaccine. Compared to yeast antigen, HEK-derived RBD was immunologically superior, likely due to observed differences in glycosylation. We show the benefits of ordered over randomly oriented multimeric antigen display, by demonstrating single-shot seroconversion and best virus-neutralizing antibodies. Azidogluconoylation is simple, fast and robust chemistry, and should accelerate research and development.