A dual-antigen self-amplifying RNA SARS-CoV-2 vaccine induces potent humoral and cellular immune responses and protects against SARS-CoV-2 variants through T cell-mediated immunity.

Self-amplifying RNA vaccines may induce equivalent or more potent immune responses at lower doses compared to non-replicating mRNA vaccines via amplified antigen expression. In this paper, we demonstrate that 1 µg of an LNP-formulated dual-antigen self-amplifying RNA vaccine (ZIP1642), encoding both the S-RBD and N antigen, elicits considerably higher neutralizing antibody titers against Wuhan-like Beta B.1.351 and Delta B.1.617.2 SARS-CoV-2 variants compared to those of convalescent patients. In addition, ZIP1642 vaccination in mice expanded both S- and N-specific CD3+CD4+ and CD3+CD8+ T cells and caused a Th1 shifted cytokine response. We demonstrate that the induction of such dual antigen-targeted cell-mediated immune response may provide better protection against variants displaying highly mutated Spike proteins, as infectious viral loads of both Wuhan-like and Beta variants were decreased after challenge of ZIP1642 vaccinated hamsters. Supported by these results, we encourage redirecting focus toward the induction of multiple antigen-targeted cell-mediated immunity in addition to neutralizing antibody responses to bypass waning antibody responses and attenuate infectious breakthrough and disease severity of future SARS-CoV-2 variants.

From PERK to RIPK1: Design, synthesis and evaluation of novel potent and selective necroptosis inhibitors.

Receptor-Interacting serine/threonine-Protein Kinase 1 (RIPK1) emerged as an important driver of inflammation and, consequently, inflammatory pathologies. The enzymatic activity of RIPK1 is known to indirectly promote inflammation by triggering cell death, in the form of apoptosis, necroptosis and pyroptosis. Small molecule Receptor-Interacting serine/threonine-Protein Kinase 1 inhibitors have therefore recently entered clinical trials for the treatment of a subset of inflammatory pathologies. We previously identified GSK2656157 (GSK'157), a supposedly specific inhibitor of protein kinase R (PKR)-like ER kinase (PERK), as a much more potent type II Receptor-Interacting serine/threonine-Protein Kinase 1 inhibitor. We now performed further structural optimisation on the GSK'157 scaffold in order to develop a novel class of more selective Receptor-Interacting serine/threonine-Protein Kinase 1 inhibitors. Based on a structure-activity relationship (SAR) reported in the literature, we anticipated that introducing a substituent on the para-position of the pyridinyl ring would decrease the interaction with PERK. Herein, we report a series of novel GSK'157 analogues with different para-substituents with increased selectivity for Receptor-Interacting serine/threonine-Protein Kinase 1. The optimisation led to UAMC-3861 as the best compound of this series in terms of activity and selectivity for Receptor-Interacting serine/threonine-Protein Kinase 1 over PERK. The most selective compounds were screened in vitro for their ability to inhibit RIPK1-dependent apoptosis and necroptosis. With this work, we successfully synthesised a novel series of potent and selective type II Receptor-Interacting serine/threonine-Protein Kinase 1 inhibitors based on the GSK'157 scaffold.

Imidazole-4-acetic acid, a new lead structure for interaction with the taurine transporter in outer blood-retinal barrier cells.

Retinal diseases leading to impaired vision and ultimately blindness are mainly characterized by ischemic and hypoxic stress. Targeting the retinal ρ-containing γ-aminobutyric acid type A receptors (ρ GABAARs) and thereby decreasing the retinal neuronal activity has been proposed as a novel therapeutic approach. The taurine transporter (TAUT) plays a key role in the retinal transport of GABA and has been previously suggested to display a higher functional activity in the retina compared to the brain. TAUT would therefore stand as a suitable target for the selective delivery of ρ GABAAR ligands into the retina. Consequently, an in vitro model of TAUT at the outer blood-retinal barrier (BRB) was developed and characterized using the ARPE-19 cell line. Furthermore, the structural requirements of GABAAR ligands for interacting with TAUT at the BRB were investigated for a series of standard GABAAR ligands by testing their ability to inhibit the TAUT-mediated influx of taurine in ARPE-19 cells. Results showed that taurine influx was seven-fold higher when the ARPE-19 cells were cultured under hyperosmotic conditions and was demonstrated to display saturable kinetics (Km=27.7±2.2µM and Jmax=24.2±0.6pmol/cm2·min). Furthermore, the taurine influx was significantly inhibited in a concentration-dependent manner by GABA and imidazole-4-acetic acid (IAA), which is a naturally occurring metabolite of histamine. These compounds display similar Ki values of 644.2µM and 658.6µM, respectively. Moreover, IAA demonstrated higher inhibitory properties than the other tested GABA analogs: 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP), 4,5,6,7-tetrahydropyrazolo[5,4-c]pyridin-3-ol (Aza-THIP), muscimol, and thiomuscimol. These studies demonstrated that IAA interacts with TAUT, which makes IAA a new lead structure in the development of new compounds, which are not only interacting with TAUT but also potent ρ GABAAR ligands.