Along with colleagues, CITF Scientific Advisor Dr. Matthew Cheng and CITF-funded researcher Dr. Donald Vinh from McGill University and the RI-MUHC, have been studying the effectiveness and immunogenicity of the Made-in-Quebec, plant-based Medicago vaccine. In a pre-print, not yet peer-reviewed, they found 94% of participants had detectable antibodies against SARS-CoV-2 at six months post second dose. Twenty-one days after the second dose, neutralizing antibodies against the Alpha, Beta and Gamma variants were found in almost all participants.
Samples from 20 healthy individuals were collected 21 days after each dose of the vaccine (two doses in total). The findings include:
- At six months post-second dose, all participants had antibodies against the Spike protein of the virus, while antibodies were present in 94% of participants.
- When measuring , almost all participants had detectable IFN-γ (94%) and IL-4 (92%) responses.
- For both antibodies and cell-mediated immunity, there was a slight decline at day 201 compared to day 21 post-second dose; however, a high proportion of participants continued to have detectable values.
- Vaccinated individuals had a high neutralization capacity (>400 band range) to the original strain and to variants of concern when measured with a pseudovirus neutralization assay. High neutralization capacity was observed in:
- 4% (17/18) for the original strain
- 2% (16/19) for the Alpha variant
- 4% (9/19) for the Beta variant
- 9% (15/19) for the Gamma variant.
- A live virus neutralization assay was also used and detectable antibody responses were observed in:
- 100% (19/19) of participants to the original strain and Alpha variant
- 7% (18/19) of participants to the Beta and Gamma variants.
This study provides evidence of a lasting immune response against SARS-CoV-2 post-second dose of this Made-in-Quebec Medicago vaccine. The capacity of antibodies to eliminate variants of concern also appears to be maintained 21 days post-second dose.
Gobeil PA, Pillet S, Boulay I, Charland N, Lorin A, Cheng M, Vinh D, Boutet P, Van Der Most R, Roman F, Perez MAC, D’Aoust MA, Landry N, Ward BJ. Durability and Cross-Reactivity of Immune Responses Induced by an AS03 Adjuvanted Plant-Based Recombinant Virus-Like Particle Vaccine for COVID-19. medRxiv. 2021 Jan 1. doi: 10.1101/2021.08.04.21261507