ABSTRACT
A safe and effective vaccine against COVID-19 is urgently needed in quantities that are sufficient to immunize large populations. Here we report the preclinical development of two vaccine candidates (BNT162b1 and BNT162b2) that contain nucleoside-modified messenger RNA that encodes immunogens derived from the spike glycoprotein (S) of SARS-CoV-2, formulated in lipid nanoparticles. BNT162b1 encodes a soluble, secreted trimerized receptor-binding domain (known as the RBD-foldon). BNT162b2 encodes the full-length transmembrane S glycoprotein, locked in its prefusion conformation by the substitution of two residues with proline (S(K986P/V987P); hereafter, S(P2) (also known as P2 S)). The flexibly tethered RBDs of the RBD-foldon bind to human ACE2 with high avidity. Approximately 20% of the S(P2) trimers are in the two-RBD 'down', one-RBD 'up' state. In mice, one intramuscular dose of either candidate vaccine elicits a dose-dependent antibody response with high virus-entry inhibition titres and strong T-helper-1 CD4+ and IFNγ+CD8+ T cell responses. Prime-boost vaccination of rhesus macaques (Macaca mulatta) with the BNT162b candidates elicits SARS-CoV-2-neutralizing geometric mean titres that are 8.2-18.2× that of a panel of SARS-CoV-2-convalescent human sera. The vaccine candidates protect macaques against challenge with SARS-CoV-2; in particular, BNT162b2 protects the lower respiratory tract against the presence of viral RNA and shows no evidence of disease enhancement. Both candidates are being evaluated in phase I trials in Germany and the USA1-3, and BNT162b2 is being evaluated in an ongoing global phase II/III trial (NCT04380701 and NCT04368728).
Subject(s)
COVID-19 Vaccines/immunology , COVID-19/immunology , COVID-19/prevention & control , Disease Models, Animal , SARS-CoV-2/immunology , Aging/immunology , Animals , Antibodies, Neutralizing/immunology , Antibodies, Viral/immunology , Antigens, Viral/chemistry , Antigens, Viral/genetics , Antigens, Viral/immunology , BNT162 Vaccine , COVID-19/blood , COVID-19/therapy , COVID-19/virology , COVID-19 Vaccines/administration & dosage , COVID-19 Vaccines/chemistry , COVID-19 Vaccines/genetics , Cell Line , Clinical Trials as Topic , Female , Humans , Immunization, Passive , Internationality , Macaca mulatta/immunology , Macaca mulatta/virology , Male , Mice , Mice, Inbred BALB C , Models, Molecular , Protein Multimerization , RNA, Viral/analysis , Respiratory System/immunology , Respiratory System/virology , SARS-CoV-2/chemistry , SARS-CoV-2/genetics , Solubility , Spike Glycoprotein, Coronavirus/chemistry , Spike Glycoprotein, Coronavirus/genetics , Spike Glycoprotein, Coronavirus/immunology , T-Lymphocytes/immunology , Vaccination , Vaccines, Synthetic/administration & dosage , Vaccines, Synthetic/chemistry , Vaccines, Synthetic/genetics , Vaccines, Synthetic/immunology , COVID-19 Serotherapy , mRNA VaccinesABSTRACT
Synthetic mRNA has emerged as a powerful tool for the transfer of genetic information, and it is being explored for a variety of therapeutic applications. Many of these applications require prolonged intracellular persistence of mRNA to improve bioavailability of the encoded protein. mRNA molecules are intrinsically unstable and their intracellular kinetics depend on the UTRs embracing the coding sequence, in particular the 3' UTR elements. We describe here a novel and generally applicable cell-based selection process for the identification of 3' UTRs that augment the expression of proteins encoded by synthetic mRNA. Moreover, we show, for two applications of mRNA therapeutics, namely, (1) the delivery of vaccine antigens in order to mount T cell immune responses and (2) the introduction of reprogramming factors into differentiated cells in order to induce pluripotency, that mRNAs tagged with the 3' UTR elements discovered in this study outperform those with commonly used 3' UTRs. This approach further leverages the utility of mRNA as a gene therapy drug format.
