No abstract

ABSTRACTmRNA vaccines have emerged as a most promising and potent platform in the fight against various diseases including the COVID-19 pandemic. However, the intrinsic instability, varying side effects associated with the delivery systems, and continuous emergence of virus variants highlight the urgent need for the development of stable, safe and efficacious mRNA vaccines. In this study, by screening a panel of proprietary biodegradable ionizable lipidoids, we reported on a novel mRNA vaccine (cmRNA-1130) formed from a biodegradable lipidoid with eight ester bonds in the branched tail (AX4) and synthetic circular mRNA (cmRNA) encoding the trimeric Delta receptor binding domain (RBD) of SARS-CoV-2 spike protein for the induction of robust immune activation. The AX4-based lipid nanoparticles (AX4-LNP) revealed much faster elimination rate from liver and spleen in comparison with commercialized MC3-based LNP (MC3-LNP) and afforded normal level of alanine transferase (ALT), aspartate aminotransferase (AST), and creatinine (CRE) in BALB/c mice. Following intramuscular (IM) administration in BALB/c mice, cmRNA-1130 elicited potent and sustained neutralizing antibodies, RBD-specific CD4+ and CD8+ T effector memory cells (Tem), and Th1-biased T cell activations. cmRNA-1130 vaccine showed excellent stability against 6-month storage at 4 □ and freezing-thawing cycles. In brief, our study highlights mRNA vaccines based on cmRNA and biodegradable AX4 lipids hold great potential as superb therapeutic platforms for the treatment of varying diseases.

No abstract

The application of mRNA as a novel kind of vaccine has been proved recently, due to the emergence use authorization (EUA) by FDA for the two COVID-19 mRNA vaccines developed by Moderna and BioNTech. Both of the two vaccines are based on canonical linear mRNA, and encapsulated by lipid nanoparticle (LNP). Circular mRNA, which is found to mediate potent and durable protein expression, is an emerging technology recently. Owing to its simplicity of manufacturing and superior performance of protein expression, circular mRNA is believed to be a disruptor for mRNA area. However, the application of circular mRNA is still at an initiation stage, proof of concept for its usage as future medicine or vaccine is necessary. In the current study, we established a novel kind of circular mRNA, termed C-RNA, based on Echovirus 29 (E29)-derived internal ribosome entry sites (IRES) and newly designed homology arms and RNA spacers. Our results demonstrated that this kind of circular mRNA is able to mediate strong and durable protein expression, compared to typical linear mRNA. Moreover, for the first time, our study demonstrated that direct intratumoral administration of C-RNA encoding a mixture of cytokines achieved successful modulation of intratumoral and systematic anti-tumor immune responses and finally leading to an enhancement of anti-PD-1 antibody-induced tumor repression in syngeneic mouse model. Additionally, after an optimization of the circular mRNA formulation, a significant improvement of C-RNA mediated protein expression was observed. With this optimized formulation, C-RNA induced enhanced anti-tumor effect via intratumoral administration and elicited significant activation of tumor-infiltrated total T cells and CD8+ T cells. Collectively, we established C-RNA, a novel circular mRNA platform, and demonstrated that it can be applied for direct intratumoral administration for cancer therapy.

Anaplasma phagocytophilum, the aetiologic agent of human granulocytic anaplasmosis (HGA) is an obligate intracellular Gram-negative bacterium with the genome size of 1.47 megabases. The intracellular life style and small size of genome suggest that A. phagocytophilum has to modulate a multitude of host cell physiological processes to facilitate its replication. One strategy employed by A. phagocytophilum is through its type IV secretion system (T4SS), which translocates bacterial effectors into target cells to disrupt normal cellular activities. In this study we developed a TEM-1 β-lactamase based protein translocation assay and applied this assay for identification of A. phagocytophilum T4SS effectors. An A. phagocytophilum hypothetical protein, APH0215 is identified as a T4SS effector protein and found interacting with trans-Golgi network in transfected cells. Hereby, this protein translocation assay developed in this study will facilitate the identification of A. phagocytophilum T4SS effectors and elucidation of HGA pathogenesis.