Asymmetric bifunctional protein nanoparticles through redesign of self-assembly

Monitoring Dynamic Conformations of a Single Fluorescent Molecule Inside a Protein Cavity

Fluorescence nanoscopy and single-molecule methods are entering the realm of structural biology, breaking new ground for dynamic structural measurements at room temperature and liquid environments. Here, single-molecule localization microscopy, polarization-dependent single-molecule excitation, and protein engineering are combined to determine the orientation of a fluorophore forming hydrogen bonds inside a protein cavity. The observed conformations are in good agreement with molecular dynamics simulations, enabling a new, more realistic interplay between experiments and simulations to identify stable conformations and the key interactions involved. Furthermore, jumps between conformations can be monitored with a precision of 3° and a time resolution of a few seconds, confirming the potential of this methodology for retrieving dynamic structural information of nanoscopic biological systems under physiologically compatible conditions.

Asymmetric Assembly and Self-Adjuvanted Antigen Delivery Platform for Improved Antigen Uptake and Antitumor Effect

The development of effective tumor vaccines is an important direction in the field of cancer prevention/immunotherapy. Efficient antigen delivery is essential for inducing effective antitumor responses for tumor vaccines. Lumazine synthase (BLS) from Brucella spp. is a decameric protein with delivery and adjuvant properties, but its application in tumor vaccines is limited. Here, we developed an antigen delivery platform by combining a BLS asymmetric assembly and the Plug-and-Display system of SpyCatcher/SpyTag. An asymmetric assembly system consisting of BLSke and BLSdr was developed to equally assemble two molecules. Then, the MHC-I-restricted ovalbumin peptide (OVA(257-264) SIINFEKL) was conjugated with BLSke, and a cell-penetrating peptide (CPP) KALA was conjugated with BLSdr using the SpyCatcher/SpyTag system. KALA modification enhanced internalization of OVA peptides by DCs as well as promoted the maturation of DCs and the cross-presentation of SIINFEKL. Moreover, the immunotherapy of a KALA-modified vaccine suppressed tumor growth and enhanced CD8⁺ T cell responses in E.G7-OVA tumor-bearing mice. In the prophylactic model, KALA-modified vaccination showed the most significant protective effect and significantly prolonged the survival period of tumor challenged mice. In conclusion, the asymmetric assembly platform equally assembles two proteins or peptides, avoiding their spatial or functional interference. This asymmetric assembly and Plug-and-Display technology provide a universal platform for rapid development of personalized tumor vaccines.

Argentinian AntiCovid Consortium, Berguer PM, Blaustein M, Bredeston LM, Craig PO, D’Alessio C, Elias F, Farré PC, Fernández NB, Gentili HG, Gándola YB, Gasulla J, Gudesblat GE, Herrera MG, Ibañez LI, Idrovo-Hidalgo T, Nadra AD, Noseda DG, Paván CH, Pavan MF, Pignataro MF, Roman EA, Ruberto LAM, Rubinstein N, Sanchez MV, Santos J, Wetzler DE, Zelada AM. Covalent coupling of Spike's receptor binding domain to a multimeric carrier produces a high immune response against SARS-CoV-2

The receptor binding domain (RBD) of the Spike protein from SARS-CoV-2 is a promising candidate to develop effective COVID-19 vaccines since it can induce potent neutralizing antibodies. We have previously reported the highly efficient production of RBD in Pichia pastoris, which is structurally similar to the same protein produced in mammalian HEK-293T cells. In this work we designed an RBD multimer with the purpose of increasing its immunogenicity. We produced multimeric particles by a transpeptidation reaction between RBD expressed in P. pastoris and Lumazine Synthase from Brucella abortus (BLS), which is a highly immunogenic and very stable decameric 170 kDa protein. Such particles were used to vaccinate mice with two doses 30 days apart. When the particles ratio of RBD to BLS units was high (6-7 RBD molecules per BLS decamer in average), the humoral immune response was significantly higher than that elicited by RBD alone or by RBD-BLS particles with a lower RBD to BLS ratio (1-2 RBD molecules per BLS decamer). Remarkably, multimeric particles with a high number of RBD copies elicited a high titer of neutralizing IgGs. These results indicate that multimeric particles composed of RBD covalent coupled to BLS possess an advantageous architecture for antigen presentation to the immune system, and therefore enhancing RBD immunogenicity. Thus, multimeric RBD-BLS particles are promising candidates for a protein-based vaccine.

Functional protein shells fabricated from the self-assembling protein sheets of prokaryotic organelles

Fabricating single component protein compartments from the shells proteins of bacterial microcompartments.