Intravenous administration of BCG protects mice against lethal SARS-CoV-2 challenge.
J Exp Med 2022;
219:e20211862. [PMID:
34889942 PMCID:
PMC8669500 DOI:
10.1084/jem.20211862]
[Citation(s) in RCA: 51] [Impact Index Per Article: 25.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 11/05/2021] [Accepted: 11/30/2021] [Indexed: 12/24/2022] Open
Abstract
In addition to providing partial protection against pediatric tuberculosis, vaccination with bacille Calmette-Guérin (BCG) has been reported to confer nonspecific resistance to unrelated pulmonary pathogens, a phenomenon attributed to the induction of long-lasting alterations within the myeloid cell compartment. Here, we demonstrate that intravenous, but not subcutaneous, inoculation of BCG protects human-ACE2 transgenic mice against lethal challenge with SARS-CoV-2 (SCV2) and results in reduced viral loads in non-transgenic animals infected with an α variant. The observed increase in host resistance was associated with reductions in SCV2-induced tissue pathology, inflammatory cell recruitment, and cytokine production that multivariate analysis revealed as only partially related to diminished viral load. We propose that this protection stems from BCG-induced alterations in the composition and function of the pulmonary cellular compartment that impact the innate response to the virus and ensuing immunopathology. While intravenous BCG vaccination is not a clinically acceptable practice, our findings provide an experimental model for identifying mechanisms by which nonspecific stimulation of the pulmonary immune response promotes host resistance to SCV2 lethality.
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