Linker-Mediated Assembly of Virus-Like Particles into Ordered Arrays via Electrostatic Control
Nanoscale virus-like particles (VLPs), which are self-assembled from protein subunits, offer the possibility of generating hierarchically assembled functional materials such as biomimetic catalytic systems and optical metamaterials. We explore the capacity to control and tune a higher-order assembly of VLPs into ordered array materials over a wide range of ionic conditions using a combination of experimental and computational methods.
The integrated methodology demonstrates that P22 VLP variants, genetically engineered to exhibit different surface charges, self-assemble into ordered arrays in the presence of PAMAM dendrimers acting as oppositely charged, macromolecular linkers. Ordered assembly occurs at an optimal ionic strength that strongly correlates with the VLP surface charge. The ordered VLP arrays exhibit the same long-range order and a similar configuration of VLP-bound dendrimers, regardless of the VLP surface charge.
The experimentally validated model identifies key electrostatic and kinetic mechanisms underlying the self-assembly process and guides the modulation of dendrimer concentration as a control parameter to tune the assembly of VLPs. The integrated approach opens new design and control strategies to fabricate active functional materials via the self-assembly of engineered VLPs.
Capsid destabilization and epitope alterations of human papillomavirus 18 in the presence of thimerosal
Thimerosal has been widely used as a preservative in drug and vaccine products for decades. Due to the strong propensity to modify thiols in proteins, conformational changes could occur due to covalent bond formation between ethylmercury (a degradant of thimerosal) and thiols. Such a conformational change could lead to partial or even complete loss of desirable protein function. This study aims to investigate the effects of thimerosal on the capsid stability and antigenicity of recombinant human papillomavirus (HPV) 18 virus-like particles (VLPs).
Dramatic destabilization of the recombinant viral capsid upon thimerosal treatment was observed. Such a negative effect on the thermal stability of VLPs preserved with thimerosal was shown to be dependent on the thimerosal concentration. Two highly neutralizing antibodies, 13H12 and 3C3, were found to be the most sensitive to thimerosal treatment. The kinetics of antigenicity loss, when monitored with 13H12 or 3C3 as probes, yielded two distinctly different sets of kinetic parameters, while the data from both monoclonal antibodies (mAbs) followed a biphasic exponential decay model.
The potential effect of thimerosal on protein function, particularly for thiol-containing proteinaceous active components, needs to be comprehensively characterized during formulation development when a preservative is necessary.
The stressed life of a lipid in the Zika virus membrane
Protein-lipid interactions modulate a plethora of physiopathologic processes and have been the subject of countless studies. However, these kinds of interactions in the context of viral envelopes have remained relatively unexplored, partially because the intrinsically small dimensions of the molecular systems escape to the current resolution of experimental techniques. However, coarse-grained and multiscale simulations may fill that niche, providing nearly atomistic resolution at an affordable computational price. Here we use multiscale simulations to characterize the lipid-protein interactions in the envelope of the Zika Virus, a prominent member of the Flavivirus genus.
Comparisons between the viral envelope and simpler molecular systems indicate that the viral membrane is under extreme pressures and asymmetric forces. Furthermore, the dense net of protein–protein contacts established by the envelope proteins creates poorly solvated regions that destabilize the external leaflet leading to a decoupled dynamics between both membrane layers. These findings lead to the idea that the Flaviviral membrane may store a significant amount of elastic energy, playing an active role in the membrane fusion process.
B19-VLPs as an effective delivery system for tumour antigens to induce humoral and cellular immune responses against triple negative breast cancer
Cancer immunotherapy is emerging as a viable treatment option for several types of cancer. Active immunotherapy aims for the induction of specific antitumor immune responses; this goal requires strategies capable of increasing the immunogenicity of tumour antigens. Parvovirus B19 virus-like particles (B19-VLPs) formed of VP2 protein had been shown to be an effective multi-neoepitope delivery system capable of inducing specific cellular responses towards coupled antigens and reducing tumour growth and lung metastases in triple negative breast cancer mouse model.
These findings encouraged us to further characterise these VP2 B19-VLPs by testing their capacity to simultaneously induce cellular and humoral responses towards other tumour-associated antigens, as this had not yet been evaluated. Here, we designed and evaluated in the 4T1 breast cancer model the prophylactic and therapeutic effect of VP2 B19-VLPs decorated with cellular (P53) and humoral (MUC1) epitopes. Balb/c mice were immunised with chimeric VLPs, vehicle, or VLPs plus adjuvant.
Tumour establishment and growth, lung metastasis, and cellular and humoral immune responses were evaluated. The prophylactic administration of chimeric VLPs without adjuvant prevented the establishment of the tumour, while by therapeutic administration, chimeric VLPs induced smaller tumour growth and decreased the number of metastases in the lung compared to wild-type VLPs. Chimeric VLPs induced high antibody titres towards the MUC1 epitope, as well as specific cellular responses towards P53 epitopes in lymph nodes local to the tumour. Our results reinforce and extend the utility of VP2 B19-VLPs as an encouraging tumour antigen delivery system in cancer immunotherapy able to improve tumour immunity in TNBC by inducing cellular and humoral immune responses.