Native immunogenicity of SARS-CoV-2 proteins may be sufficient to elicit protective immunity in humans. Accidental mucosal exposure in a laboratory scientist (P001) to a commercially-obtained, purified SARS-CoV-2 recombinant S1 subunit (S1) protein resulted in S1-reactive antibodies with serum titers up to 1:12,800. A surrogate virus neutralization test (sVNT) demonstrated enduring neutralizing antibodies (nAbs). P001 PBMCs and whole blood exposed to S1 protein resulted in interferon-γ (IFN-γ) release ex vivo . Importantly, no systemic adverse events were observed. Potent immunogenicity of full-length S1 protein in a water-in-oil emulsion provides important clues for COVID-19 vaccine development and may serve as the basis of a low-cost, stable, and highly scalable intranasal vaccine candidate to address COVID-19 globally.
Inadvertent Human Mucosal Exposure to SARS-CoV-2 Recombinant S1 Protein Elicits Immunity