Intranasal administration of a single dose of a candidate live attenuated vaccine derived from an NSP16-deficient SARS-CoV-2 strain confers sterilizing immunity in animals

Cell Mol Immunol. 2022 May;19(5):588-601. doi: 10.1038/s41423-022-00855-4. Epub 2022 Mar 29.


Live attenuated vaccines might elicit mucosal and sterilizing immunity against SARS-CoV-2 that the existing mRNA, adenoviral vector and inactivated vaccines fail to induce. Here, we describe a candidate live attenuated vaccine strain of SARS-CoV-2 in which the NSP16 gene, which encodes 2'-O-methyltransferase, is catalytically disrupted by a point mutation. This virus, designated d16, was severely attenuated in hamsters and transgenic mice, causing only asymptomatic and nonpathogenic infection. A single dose of d16 administered intranasally resulted in sterilizing immunity in both the upper and lower respiratory tracts of hamsters, thus preventing viral spread in a contact-based transmission model. It also robustly stimulated humoral and cell-mediated immune responses, thus conferring full protection against lethal challenge with SARS-CoV-2 in a transgenic mouse model. The neutralizing antibodies elicited by d16 effectively cross-reacted with several SARS-CoV-2 variants. Secretory immunoglobulin A was detected in the blood and nasal wash of vaccinated mice. Our work provides proof-of-principle evidence for harnessing NSP16-deficient SARS-CoV-2 for the development of live attenuated vaccines and paves the way for further preclinical studies of d16 as a prototypic vaccine strain, to which new features might be introduced to improve safety, transmissibility, immunogenicity and efficacy.

Keywords: 2′-O-methyltransferase; Live attenuated vaccine; Mucosal immunity; NSP16; Sterilizing immunity; T-cell response.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Intranasal
  • Animals
  • Antibodies, Neutralizing
  • Antibodies, Viral
  • COVID-19 Vaccines
  • COVID-19* / prevention & control
  • Cricetinae
  • Mice
  • Mice, Transgenic
  • SARS-CoV-2*
  • Spike Glycoprotein, Coronavirus
  • Vaccines, Attenuated / genetics


  • Antibodies, Neutralizing
  • Antibodies, Viral
  • COVID-19 Vaccines
  • Spike Glycoprotein, Coronavirus
  • Vaccines, Attenuated
  • spike protein, SARS-CoV-2

Supplementary concepts

  • SARS-CoV-2 variants