Humoral and cellular immune responses to CoronaVac up to one year after vaccination.

Coronavac is a widely used SARS-CoV-2 inactivated vaccine, but its long-term immune response assessment is still lacking. We evaluated SARS-CoV-2-specific immune responses, including T cell activation markers, antigen-specific cytokine production and antibody response following vaccination in 53 adult and elderly individuals participating in a phase 3 clinical trial. Activated follicular helper T (Tfh), non-Tfh and memory CD4+ T cells were detected in almost all subjects early after the first vaccine dose. Activated memory CD4+ T cells were predominantly of central and effector memory T cell phenotypes and were sustained for at least 6 months. We also detected a balanced Th1-, Th2- and Th17/Th22-type cytokine production that was associated with response over time, together with particular cytokine profile linked to poor responses in older vaccinees. SARS-CoV-2-specific IgG levels peaked 14 days after the second dose and were mostly stable over one year. CoronaVac was able to induce a potent and durable antiviral antigen-specific cellular response and the cytokine profiles related to the response over time and impacted by the senescence were defined.

Humoral and cellular immune responses to CoronaVac assessed up to one year after vaccination.

Background: The Sinovac SARS-CoV-2 inactivated vaccine (CoronaVac) has been demonstrated to be safe, well tolerated, and efficacious in preventing mild and severe Covid-19. Although different studies have demonstrated its short-term immunogenicity, long-term cellular and humoral response evaluations are still lacking. Methods: Cellular and humoral responses were assessed after enrollment of volunteers in the PROFISCOV phase 3 double-blind, randomized, placebo-controlled clinical trial to evaluate CoronaVac. Assays were performed using flow cytometry to evaluate cellular immune response and an antigen binding electrochemiluminescence assay to detect antigen-specific antibodies to the virus. Results: Fifty-three volunteers were selected for long term assessment of their SARS-CoV-2-specific immune responses. CD4 + T cell responses (including circulating follicular helper (cTfh, CD45RA - CXCR5 + ) expressing CD40L, as well as non-cTfh cells expressing CXCR3) were observed early upon the first vaccine dose, increased after the second dose, remaining stable for 6-months. Memory CD4 + T cells were detected in almost all vaccinees, the majority being central memory T cells. IgG levels against Wuhan/WH04/2020 N, S and receptor binding domain (RBD) antigens and the variants of concern (VOCs, including B.1.1.7/Alpha, B.1.351/Beta and P.1/Gamma) S and RBD antigens peaked 14 days after the second vaccine shot, and were mostly stable for a 1-year period. Conclusions: CoronaVac two-doses regimen is able to induce a potent and durable SARS-CoV-2 specific cellular response. The cellular reaction is part of a coordinated immune response that includes high levels of specific IgG levels against parental and SARS-CoV-2 VOC strains, still detected after one year. Funding: Fundação Butantan, Instituto Butantan and São Paulo Research Foundation (FAPESP) (grants 2020/10127-1 and 2020/06409-1). This work has also been supported by NIH contract 75N93019C00065 (A.S, D.W). PATH facilitated reagent donations for this work with support by the Bill & Melinda Gates Foundation (INV-021239). Under the grant conditions of the foundation, a Creative Commons Attribution 4.0 generic License has already been assigned to the Author Accepted Manuscript version that might arise from this submission.

A Newcastle disease virus expressing a stabilized spike protein of SARS-CoV-2 induces protective immune responses

Rapid development of COVID-19 vaccines has helped mitigating SARS-CoV-2 spread, but more equitable allocation of vaccines is necessary to limit the global impact of the COVID-19 pandemic and the emergence of additional variants of concern. We have developed a COVID-19 vaccine candidate based on Newcastle disease virus (NDV) that can be manufactured at high yields in embryonated eggs. Here, we show that the NDV vector expressing an optimized spike antigen (NDV-HXP-S) is a versatile vaccine inducing protective antibody responses. NDV-HXP-S can be administered intramuscularly as inactivated vaccine or intranasally as live vaccine. We show that NDV-HXP-S GMP-produced in Vietnam, Thailand and Brazil is effective in the hamster model. Furthermore, we show that intramuscular vaccination with NDV-HXP-S reduces replication of tested variants of concerns in mice. The immunity conferred by NDV-HXP-S effectively counteracts SARS-CoV-2 infection in mice and hamsters.