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Kachko A, Selvaraj P, Liu S, Kim J, Rotstein D, Stauft CB, Chabot S, Rajasagi N, Zhao Y, Wang T, Major M. Vaccine-associated respiratory pathology correlates with viral clearance and protective immunity after immunization with self-amplifying RNA expressing the spike (S) protein of SARS-CoV-2 in mouse models. Vaccine 2024; 42:608-619. [PMID: 38142216 DOI: 10.1016/j.vaccine.2023.12.052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 12/18/2023] [Accepted: 12/18/2023] [Indexed: 12/25/2023]
Abstract
In this study, we evaluated the immunogenicity and protective immunity of in vitro transcribed Venezuelan equine encephalitis virus (VEEV TC-83 strain) self-amplifying RNA (saRNA) encoding the SARS-CoV-2 spike (S) protein in wild type (S-WT) and stabilized pre-fusion conformations (S-PP). Immunization with S-WT and S-PP saRNA induced specific neutralizing antibody responses in both K18-Tg hACE2 (K18) and BALB/c mice, as assessed using SARS-CoV-2 pseudotyped viruses. Protective immunity was assessed in challenge experiments. Two immunizations with S-WT and S-PP induced protective immunity, evidenced by lower mortality, lower weight loss and more than one log10 lower subgenomic virus RNA titers in the upper and lower respiratory tracts in both K18 and BALB/c mice. Histopathologic examination of lungs post-challenge showed that immunization with S-WT and S-PP resulted in a higher degree of immune cell infiltration and inflammatory changes, compared with control mice, characterized by high levels of T- and B-cell infiltration. No substantial differences were found in the presence and localization of eosinophils, macrophages, neutrophils, and natural killer cells. CD4 and CD8 T-cell depletion post immunization resulted in reduced lung inflammation post challenge but also prolonged virus clearance. These data indicate that immunization with saRNA encoding the SARS-CoV-2 S protein induces immune responses that are protective following challenge, that virus clearance is associated with pulmonary changes caused by T-cell and B-cell infiltration in the lungs, but that this T and B-cell infiltration plays an important role in viral clearance.
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Affiliation(s)
- Alla Kachko
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA.
| | - Prabhuanand Selvaraj
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Shufeng Liu
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Jaekwan Kim
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - David Rotstein
- Division of Food Compliance, Center for Veterinary Medicine, Food and Drug Administration, Rockville, MD, USA
| | - Charles B Stauft
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Sylvie Chabot
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Naveen Rajasagi
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Yangqing Zhao
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Tony Wang
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
| | - Marian Major
- Division of Viral Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, MD, USA
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