Ad26 vector-based COVID-19 vaccine encoding a prefusion-stabilized SARS-CoV-2 Spike immunogen induces potent humoral and cellular immune responses.
Level 5 - mechanism / opinion, no new human data
Preclinical in vitro and animal (mouse) research.
PubMed 33083026 · doi:10.1038/s41541-020-00243-x
What was done
Researchers evaluated design modifications for an adenovirus serotype 26 (Ad26) vector-based SARS-CoV-2 vaccine candidate. They tested the effects of prefusion-stabilizing substitutions (furin cleavage site mutations and two consecutive prolines in the S2 hinge region) and signal peptide choices on spike protein conformation and antibody binding in vitro. The optimized construct, encoding a membrane-bound stabilized spike protein with a wild-type signal peptide (Ad26.COV2.S), was then tested for humoral and cellular immunogenicity in mice.
What was found
In vitro characterization showed that stabilizing substitutions increased the ratio of neutralizing versus non-neutralizing antibody binding, consistent with a prefusion conformation, and the wild-type signal peptide supported correct protein cleavage. In mice, the construct elicited potent neutralizing antibody responses and Th1-polarized (IFN-γ) cellular immunity. The abstract provides no exact quantitative values or sample sizes.
Why it matters
This study established the preclinical construct design and rationale for the Ad26.COV2.S COVID-19 vaccine prior to clinical testing.
Limits
The study is limited to in vitro and mouse models with no quantitative metrics reported in the abstract. Protection against viral challenge, duration of immunity, and human efficacy cannot be determined from these data alone.
Cited by
- supports The mRNA and Johnson & Johnson COVID-19 vaccines incorporate two proline amino acid substitutions into the SARS-CoV-2 spike protein sequence to stabilize it in a closed, prefusion conformation.