mRNA Vaccine Mitigates SARS-CoV-2 Infections and COVID-19

Abstract

The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in December of 2019 and is responsible for millions of infections and deaths across the globe. Vaccination against SARS-CoV-2 has proven effective to contain the spread of the virus and reduce disease. The production and distribution of these vaccines occurred at a remarkable pace, largely through the employment of the novel mRNA platform. However, interruptions in supply chain and high demand for clinical grade reagents have impeded the manufacture and distribution of mRNA vaccines at a time when accelerated vaccine deployment is crucial. Furthermore, the emergence of SARS-CoV-2 variants across the globe continues to threaten the efficacy of vaccines encoding the ancestral virus spike protein. Here, we report results from preclinical studies on mRNA vaccines developed using a proprietary mRNA production process developed by GreenLight Biosciences. Two mRNA vaccines encoding the full-length, nonstabilized SARS-CoV-2 spike protein, GLB-COV2-042 and GLB-COV2-043, containing uridine and pseudouridine, respectively, were evaluated in rodents for their immunogenicity and protection from SARS-CoV-2 challenge with the ancestral strain and the Alpha (B.1.1.7) and Beta (B.1.351) variants. In mice and hamsters, both vaccines induced robust spike-specific binding and neutralizing antibodies, and in mice, vaccines induced significant T cell responses with a clear Th1 bias. In hamsters, both vaccines conferred significant protection following challenge with SARS-CoV-2 as assessed by weight loss, viral load, and virus replication in the lungs and nasopharynx. These results support the development of GLB-COV2-042 and GLB-COV2-043 for clinical use. IMPORTANCE SARS-CoV-2 continues to disrupt everyday life and cause excess morbidity and mortality worldwide. Vaccination has been key to quelling the impact of this respiratory pathogen, and mRNA vaccines have led the charge on this front. However, the emergence of SARS-CoV-2 variants has sparked fears regarding vaccine efficacy. Furthermore, SARS-CoV-2 vaccines continue to be unevenly distributed across the globe. For these reasons and despite the success of emergency authorized and licensed SARS-CoV-2 vaccines, additional vaccines are needed to meet public health demands. The studies presented here are significant as they demonstrate robust protective efficacy of mRNA vaccines developed by GreenLight Biosciences against not only wild-type SARS-CoV-2, but also Alpha and Beta variants. These results support the progression of GreenLight Biosciences SARS-CoV-2 mRNA vaccines to clinical trials as another defense against SARS-CoV-2.

Keywords: SARS-CoV-2; coronavirus; mRNA; vaccines; virology.

FIG 1

Immunogenicity in mice following GLB-SARS-CoV mRNA vaccination. 8-week-old female C57BL/6 mice were immunized with 100 μg (n = 5), 30 μg (n = 5), or 5 μg (n = 5) of GLB-COV2-042 or GLB-COV2-043 mRNA on days 0 and 21. Blood was collected on days 0, 28, and 42 for serum antibody analysis. Spleens for T cell analysis were collected ~3 months postinitial immunization. (a) Postprime neutralizing antibody titers on day 21 (b) Postboost neutralizing antibody titers on day 28. (c) Postboost neutralizing antibody titers on day 42. (d) Cytokine secretion of restimulated splenocytes. (e) Percent of CD4⁺ T cells secreting Th1/2 cytokines. (f) Percent of CD8⁺ T cells secreting Th1/2 cytokines. Means and standard deviations are shown. Data from controls were combined for statistical analyses. Statistical analyses were performed using rank-based Mann-Whitney and Holm-Šidάk multiple-comparison tests. Statistical signifiers above bars represent significance between that group and controls. *, P < 0.05; ***, P < 0.005; ****, P < 0.001.

FIG 2

Immunogenicity in hamsters and protection from challenge with SARS-CoV-2 USA-WA1/2020. Golden Syrian Hamsters (n = 4 male and n = 4 female) were vaccinated with 100, 30, or 5 μg of GLB-COV2-042 or GLB-COV2-043 on days 0 and 21. (a and b) FRNT results on days 21 and 39. Means and standard deviations are shown. (c) Percent body weight change of each vaccination group over 14 days postinfection. Data from controls were combined for statistical analyses. Statistical analyses were performed using rank-based Mann-Whitney and Holm-Šidάk multiple-comparison tests. Statistical signifiers above bars represent significance between that group and controls. *, P < 0.05; ***, P < 0.005; ****, P < 0.001.

FIG 3

Quantification of SARS-CoV-2 in lungs of GLB-COV2 mRNA-vaccinated hamsters following SARS-CoV-2 challenge. Golden Syrian Hamsters (n = 4 male and n = 4 female) were vaccinated with 100, 30, or 5 μg of GLB-COV2-042 or GLB-COV2-043 on days 0 and 21 and challenges on day 42. (a and b) Detection of SARS-CoV-2 nucleocapsid via RT-qPCR at days 2 and 4 postchallenge. (c and d) Detection of active viral particles via TCID₅₀ at days 2 and 4 postchallenge. Means and standard deviations are shown. Data from controls were combined for statistical analysis. Statistical analyses were performed using rank-based Mann-Whitney and Holm-Šidάk multiple-comparison tests. Statistical signifiers above bars represent significance between that group and controls. *, P < 0.05; ***, P < 0.005; ****, P < 0.001.

FIG 4

Quantification of SARS-CoV-2 in the nasopharynx of GLB-COV2 mRNA-vaccinated hamsters following viral challenge. Golden Syrian Hamsters (n = 4 male and n = 4 female) were vaccinated with 100, 30, or 5 μg of GLB-COV2-042 or GLB-COV2-043 on days 0 and 21 and challenged on day 42. (a and b) Detection of SARS-CoV-2 nucleocapsid via qPCR at days 2 and 4 postchallenge. (c and d) Detection of active viral particles via TCID₅₀ at days 2 and 4 postchallenge. Means and standard deviations are shown. Data from controls were combined for statistical analysis. Statistical analyses were performed using rank-based Mann-Whitney and Holm-Šidάk multiple-comparison tests. Statistical signifiers above bars represent significance between that group and controls. *, P < 0.05; ***, P < 0.005; ****, P < 0.001.

FIG 5

Neutralizing antibody response to WA-1 and variant SARS-CoV-2 viruses. Golden Syrian Hamsters (n = 8/group) were vaccinated with 30 μg of GLB-COV2-043 on days 0 and 21. Day 39 microneutralization titers in vaccinated and unvaccinated animals against each challenge virus are shown. Statistical analyses were performed using rank-based Mann-Whitney and Holm-Šidάk multiple-comparison tests. Statistical signifiers above bars represent significance between that group and controls. *, P < 0.05; ***, P < 0.005; ****, P < 0.001.

FIG 6

Morbidity in hamsters vaccinated with GLB-COV2 mRNA vaccines following SARS-CoV-2 variant challenge. Golden Syrian Hamsters (n = 8) were vaccinated with 30 μg of GLB-COV2-043 on days 0 and 21 and challenged on day 42. Percent body weight change of each vaccination group over 14 days postinfection.

FIG 7

Viral titers in hamsters vaccinated with GLB-COV2 mRNA vaccines following SARS-CoV-2 variant challenge. Golden Syrian Hamsters (n = 8) were vaccinated with 30 μg of GLB-COV2-043 on days 0 and 21 and challenged on day 42. (a to c) Nasal wash TCID₅₀ values over the course of infection. (d to f) Area under the curve analysis of nasal wash TCID₅₀ values. (g-i) Lung TCID₅₀ values 2 days postchallenge (n = 4). (j to l) Trachea TCID₅₀ values 2 days postchallenge (n = 4). Means and standard deviations are shown. Data from controls were combined for statistical analysis. Statistical analyses were performed using rank-based Mann-Whitney and Holm-Šidάk multiple-comparison tests. Statistical signifiers above bars represent significance between that group and controls. *, P < 0.05; ***, P < 0.005; ****, P < 0.001.