An mRNA Vaccine Protects Mice against Multiple Tick-Transmitted Flavivirus Infections

Summary: Powassan virus (POWV) is an emerging tick-transmitted flavivirus that circulates in North America and Russia. Up to 5% of deer ticks now test positive for POWV in certain regions of the northern United States. Although POWV infections cause life-threatening encephalitis, there is no vaccine or countermeasure available for prevention or treatment. Here, we developed a lipid nanoparticle (LNP)-encapsulated modified mRNA vaccine encoding the POWV prM and E genes and demonstrated its immunogenicity and efficacy in mice following immunization with one or two doses. The POWV mRNA vaccine induced high titers of neutralizing antibody and sterilizing immunity against lethal challenge with different POWV strains. The mRNA vaccine also induced cross-neutralizing antibodies against multiple other tick-borne flaviviruses and protected mice against the distantly related Langat virus. These data demonstrate the utility of the LNP-mRNA vaccine platform for the development of vaccines with protective activity against multiple flaviviruses. : VanBlargan et al. demonstrate a lipid nanoparticle-encapsulated mRNA vaccine against Powassan virus, an emerging tick-borne flavivirus, is highly immunogenic in mice and protects against lethal Powassan virus infection. Furthermore, the vaccine induces a cross-reactive antibody response against other tick-borne flavivirus that is protective against disease caused by Langat virus infection in mice. Keywords: flavivirus, vaccine, pathogenesis, encephabilitis, mouse model

Rational Design and In Vivo Characterization of mRNA-Encoded Broadly Neutralizing Antibody Combinations against HIV-1

Monoclonal antibodies have been used successfully as recombinant protein therapy; however, for HIV, multiple broadly neutralizing antibodies may be necessary. We used the mRNA-LNP platform for in vivo co-expression of 3 broadly neutralizing antibodies, PGDM1400, PGT121, and N6, directed against the HIV-1 envelope protein. mRNA-encoded HIV-1 antibodies were engineered as single-chain Fc (scFv-Fc) to overcome heavy- and light-chain mismatch. In vitro neutralization breadth and potency of the constructs were compared to their parental IgG form. We assessed the ability of these scFv-Fcs to be expressed individually and in combination in vivo, and neutralization and pharmacokinetics were compared to the corresponding full-length IgGs. Single-chain PGDM1400 and PGT121 exhibited neutralization potency comparable to parental IgG, achieving peak systemic concentrations ≥ 30.81 μg/mL in mice; full-length N6 IgG achieved a peak concentration of 974 μg/mL, but did not tolerate single-chain conversion. The mRNA combination encoding full-length N6 IgG and single-chain PGDM1400 and PGT121 was efficiently expressed in mice, achieving high systemic concentration and desired neutralization potency. Analysis of mice sera demonstrated each antibody contributed towards neutralization of multiple HIV-1 pseudoviruses. Together, these data show that the mRNA-LNP platform provides a promising approach for antibody-based HIV treatment and is well-suited for development of combination therapeutics

Optimization of Lipid Nanoparticles for Intramuscular Administration of mRNA Vaccines

mRNA vaccines have the potential to tackle many unmet medical needs that are unable to be addressed with conventional vaccine technologies. A potent and well-tolerated delivery technology is integral to fully realizing the potential of mRNA vaccines. Pre-clinical and clinical studies have demonstrated that mRNA delivered intramuscularly (IM) with first-generation lipid nanoparticles (LNPs) generates robust immune responses. Despite progress made over the past several years, there remains significant opportunity for improvement, as the most advanced LNPs were designed for intravenous (IV) delivery of siRNA to the liver. Here, we screened a panel of proprietary biodegradable ionizable lipids for both expression and immunogenicity in a rodent model when administered IM. A subset of compounds was selected and further evaluated for tolerability, immunogenicity, and expression in rodents and non-human primates (NHPs). A lead formulation was identified that yielded a robust immune response with improved tolerability. More importantly for vaccines, increased innate immune stimulation driven by LNPs does not equate to increased immunogenicity, illustrating that mRNA vaccine tolerability can be improved without affecting potency. Keywords: mRNA, vaccines, LNP, intramuscular, lipids, tolerability, immunogenicity, formulatio

A Lassa virus mRNA vaccine confers protection but does not require neutralizing antibody in a guinea pig model of infection

Abstract Lassa virus is a member of the Arenaviridae family, which causes human infections ranging from asymptomatic to severe hemorrhagic disease with a high case fatality rate. We have designed and generated lipid nanoparticle encapsulated, modified mRNA vaccines that encode for the wild-type Lassa virus strain Josiah glycoprotein complex or the prefusion stabilized conformation of the Lassa virus glycoprotein complex. Hartley guinea pigs were vaccinated with two 10 µg doses, 28 days apart, of either construct. Vaccination induced strong binding antibody responses, specific to the prefusion conformation of glycoprotein complex, which were significantly higher in the prefusion stabilized glycoprotein complex construct group and displayed strong Fc-mediated effects. However, Lassa virus-neutralizing antibody activity was detected in some but not all animals. Following the challenge with a lethal dose of the Lassa virus, all vaccinated animals were protected from death and severe disease. Although the definitive mechanism of protection is still unknown, and assessment of the cell-mediated immune response was not investigated in this study, these data demonstrate the promise of mRNA as a vaccine platform against the Lassa virus and that protection against Lassa virus can be achieved in the absence of virus-neutralizing antibodies

Multivalent mRNA-DTP vaccines are immunogenic and provide protection from Bordetella pertussis challenge in mice

Abstract Acellular multivalent vaccines for pertussis (DTaP and Tdap) prevent symptomatic disease and infant mortality, but immunity to Bordetella pertussis infection wanes significantly over time resulting in cyclic epidemics of pertussis. The messenger RNA (mRNA) vaccine platform provides an opportunity to address complex bacterial infections with an adaptable approach providing Th1-biased responses. In this study, immunogenicity and challenge models were used to evaluate the mRNA platform with multivalent vaccine formulations targeting both B. pertussis antigens and diphtheria and tetanus toxoids. Immunization with mRNA formulations were immunogenetic, induced antigen specific antibodies, as well as Th1 T cell responses. Upon challenge with either historical or contemporary B. pertussis strains, 6 and 10 valent mRNA DTP vaccine provided protection equal to that of 1/20th human doses of either DTaP or whole cell pertussis vaccines. mRNA DTP immunized mice were also protected from pertussis toxin challenge as measured by prevention of lymphocytosis and leukocytosis. Collectively these pre-clinical mouse studies illustrate the potential of the mRNA platform for multivalent bacterial pathogen vaccines

Vaccine mediated protection against Zika virus-induced congenital disease

Washington University School of Medicine. Department of Medicine. St. Louis, MO, USA.Washington University School of Medicine. Department of Medicine. St. Louis, MO, USA.University of Texas Medical Branch. Department of Biochemistry & Molecular Biology. Galveston, TX, USA.University of Texas Medical Branch. Department of Biochemistry & Molecular Biology. Galveston, TX, USA.National Institutes of Health. Laboratory of Viral Diseases. Viral Pathogenesis Section. Bethesda, MD. USAWashington University School of Medicine. Department of Obstetrics and Gynecology. St. Louis, MO, USA.Moderna Venture. Valera LLC. Technology Square. Cambridge, MA, USA.Washington University School of Medicine. Department of Medicine. St. Louis, MO, USA.University of Texas Medical Branch. Department of Biochemistry & Molecular Biology. Galveston, TX, USA / Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Ananindeua, PA, Brasil.University of Texas Medical Branch. Department of Biochemistry & Molecular Biology. Galveston, TX, USA / Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Ananindeua, PA, Brasil.University of Texas Medical Branch. Department of Biochemistry & Molecular Biology. Galveston, TX, USA / University of Texas Medical Branch. Department of Pathology. Galveston, TX, USA.National Institutes of Health. Laboratory of Viral Diseases. Viral Pathogenesis Section. Bethesda, MD, USA.University of Texas Medical Branch. Department of Pathology. Galveston, TX, USA.University of Texas Medical Branch. Department of Microbiology and Immunology. Galveston, TX, USA / University of Texas Medical Branch. Sealy Center for Vaccine Development. Galveston, TX, USA.University of Texas Medical Branch. Department of Pathology. Galveston, TX, USA / University of Texas Medical Branch. Sealy Center for Vaccine Development. Galveston, TX, USA.University of Texas Medical Branch. Department of Microbiology and Immunology. Galveston, TX, USA / University of Texas Medical Branch. Institute for Human infections and Immunity. Galveston, TX, USA / University of Texas Medical Branch. Sealy Center for Vaccine Development. Galveston, TX, USA.Ministério da Saúde. Secretaria de Vigilância em Saúde. Instituto Evandro Chagas. Ananindeua, PA, Brasil / Pará State University. Department of Pathology. Belém, PA, Brazil.University of Texas Medical Branch. Department of Pathology. Galveston, TX, USA / University of Texas Medical Branch. Institute for Human infections and Immunity. Galveston, TX, USA.Moderna Venture. Valera LLC. Technology Square. Cambridge, MA, USA.Washington University School of Medicine. Department of Obstetrics and Gynecology. St. Louis, MO, USA / Washington University School of Medicine. Department of Pathology and Immunology. St. Louis, MO, USA.National Institutes of Health. Laboratory of Viral Diseases. Viral Pathogenesis Section. Bethesda, MD, USA.University of Texas Medical Branch. Department of Biochemistry & Molecular Biology. Galveston, TX, USA / University of Texas Medical Branch. Institute for Translational Science. Galveston, TX, USA / University of Texas Medical Branch. Institute for Human infections and Immunity. Galveston, TX, USA / University of Texas Medical Branch. Department of Pharmacology & Toxicology. Galveston, TX, USA / University of Texas Medical Branch. Sealy Center for Structural Biology & Molecular Biophysics. Galveston, TX, USA.Washington University School of Medicine. Department of Medicine. St. Louis, MO, USA / Washington University School of Medicine. Department of Pathology and Immunology. St. Louis, MO, USA / Washington University School of Medicine. Department of Molecular Microbiology. St. Louis, MO, USA / Washington University School of Medicine. The Andrew M. and Jane M. Bursky Center for Human Immunology and Immunotherapy Programs. St. Louis, MO, USA.The emergence of Zika virus (ZIKV) and its association with congenital malformations has prompted the rapid development of vaccines. Although efficacy with multiple viral vaccine platforms has been established in animals, no study has addressed protection during pregnancy. We tested in mice two vaccine platforms, a lipid nanoparticle-encapsulated modified mRNA vaccine encoding ZIKV prM and E genes and a live-attenuated ZIKV strain encoding an NS1 protein without glycosylation, for their ability to protect against transmission to the fetus. Vaccinated dams challenged with a heterologous ZIKV strain at embryo day 6 (E6) and evaluated at E13 showed markedly diminished levels of viral RNA in maternal, placental, and fetal tissues, which resulted in protection against placental damage and fetal demise. As modified mRNA and live-attenuated vaccine platforms can restrict in utero transmission of ZIKV in mice, their further development in humans to prevent congenital ZIKV syndrome is warranted

Human immunoglobulin repertoire analysis guides design of vaccine priming immunogens targeting HIV V2-apex broadly neutralizing antibody precursors

Broadly neutralizing antibodies (bnAbs) to the HIV envelope (Env) V2-apex region are important leads for HIV vaccine design. Most V2-apex bnAbs engage Env with an uncommonly long heavy-chain complementarity-determining region 3 (HCDR3), suggesting that the rarity of bnAb precursors poses a challenge for vaccine priming. We created precursor sequence definitions for V2-apex HCDR3-dependent bnAbs and searched for related precursors in human antibody heavy-chain ultradeep sequencing data from 14 HIV-unexposed donors. We found potential precursors in a majority of donors for only two long-HCDR3 V2-apex bnAbs, PCT64 and PG9, identifying these bnAbs as priority vaccine targets. We then engineered ApexGT Env trimers that bound inferred germlines for PCT64 and PG9 and had higher affinities for bnAbs, determined cryo-EM structures of ApexGT trimers complexed with inferred-germline and bnAb forms of PCT64 and PG9, and developed an mRNA-encoded cell-surface ApexGT trimer. These methods and immunogens have promise to assist HIV vaccine development.</p

Vaccination induces broadly neutralizing antibody precursors to HIV gp41

A key barrier to the development of vaccines that induce broadly neutralizing antibodies (bnAbs) against human immunodeficiency virus (HIV) and other viruses of high antigenic diversity is the design of priming immunogens that induce rare bnAb-precursor B cells. The high neutralization breadth of the HIV bnAb 10E8 makes elicitation of 10E8-class bnAbs desirable; however, the recessed epitope within gp41 makes envelope trimers poor priming immunogens and requires that 10E8-class bnAbs possess a long heavy chain complementarity determining region 3 (HCDR3) with a specific binding motif. We developed germline-targeting epitope scaffolds with affinity for 10E8-class precursors and engineered nanoparticles for multivalent display. Scaffolds exhibited epitope structural mimicry and bound bnAb-precursor human naive B cells in ex vivo screens, protein nanoparticles induced bnAb-precursor responses in stringent mouse models and rhesus macaques, and mRNA-encoded nanoparticles triggered similar responses in mice. Thus, germline-targeting epitope scaffold nanoparticles can elicit rare bnAb-precursor B cells with predefined binding specificities and HCDR3 features.</p