RESUMO
A self-transcribing and replicating RNA (STARR)-based vaccine (LUNAR-COV19) has been developed to prevent SARS-CoV-2 infection. The vaccine encodes an alphavirus-based replicon and the SARS-CoV-2 full-length spike glycoprotein. Translation of the replicon produces a replicase complex that amplifies and prolongs SARS-CoV-2 spike glycoprotein expression. A single prime vaccination in mice led to robust antibody responses, with neutralizing antibody titers increasing up to day 60. Activation of cell-mediated immunity produced a strong viral antigen-specific CD8+ T lymphocyte response. Assaying for intracellular cytokine staining for interferon (IFN)γ and interleukin-4 (IL-4)-positive CD4+ T helper (Th) lymphocytes as well as anti-spike glycoprotein immunoglobulin G (IgG)2a/IgG1 ratios supported a strong Th1-dominant immune response. Finally, single LUNAR-COV19 vaccination at both 2 µg and 10 µg doses completely protected human ACE2 transgenic mice from both mortality and even measurable infection following wild-type SARS-CoV-2 challenge. Our findings collectively suggest the potential of LUNAR-COV19 as a single-dose vaccine.
Assuntos
Anticorpos Neutralizantes/biossíntese , Anticorpos Antivirais/biossíntese , Vacinas contra COVID-19/administração & dosagem , COVID-19/prevenção & controle , SARS-CoV-2/efeitos dos fármacos , Glicoproteína da Espícula de Coronavírus/imunologia , Vacinas Sintéticas/administração & dosagem , Alphavirus/genética , Alphavirus/imunologia , Enzima de Conversão de Angiotensina 2/genética , Enzima de Conversão de Angiotensina 2/imunologia , Animais , Linfócitos T CD8-Positivos/efeitos dos fármacos , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/virologia , COVID-19/imunologia , COVID-19/patologia , COVID-19/virologia , Vacinas contra COVID-19/biossíntese , Vacinas contra COVID-19/genética , Vacinas contra COVID-19/imunologia , Feminino , Expressão Gênica , Humanos , Imunidade Celular/efeitos dos fármacos , Imunidade Humoral/efeitos dos fármacos , Interferon gama/genética , Interferon gama/imunologia , Interleucina-4/genética , Interleucina-4/imunologia , Camundongos , Camundongos Transgênicos , Replicon/imunologia , SARS-CoV-2/imunologia , SARS-CoV-2/patogenicidade , Glicoproteína da Espícula de Coronavírus/química , Glicoproteína da Espícula de Coronavírus/genética , Células Th1/efeitos dos fármacos , Células Th1/imunologia , Células Th1/virologia , Transgenes , Resultado do Tratamento , Vacinação/métodos , Vacinas Sintéticas/biossíntese , Vacinas Sintéticas/genética , Vacinas Sintéticas/imunologia , Vacinas de mRNARESUMO
Combination of waning immunity and lower effectiveness against new SARS-CoV-2 variants of approved COVID-19 vaccines necessitates new vaccines. We evaluated two doses, 28 days apart, of ARCT-154, a self-amplifying mRNA COVID-19 vaccine, compared with saline placebo in an integrated phase 1/2/3a/3b controlled, observer-blind trial in Vietnamese adults (ClinicalTrial.gov identifier: NCT05012943). Primary safety and reactogenicity outcomes were unsolicited adverse events (AE) 28 days after each dose, solicited local and systemic AE 7 days after each dose, and serious AEs throughout the study. Primary immunogenicity outcome was the immune response as neutralizing antibodies 28 days after the second dose. Efficacy against COVID-19 was assessed as primary and secondary outcomes in phase 3b. ARCT-154 was well tolerated with generally mild-moderate transient AEs. Four weeks after the second dose 94.1% (95% CI: 92.1-95.8) of vaccinees seroconverted for neutralizing antibodies, with a geometric mean-fold rise from baseline of 14.5 (95% CI: 13.6-15.5). Of 640 cases of confirmed COVID-19 eligible for efficacy analysis most were due to the Delta (B.1.617.2) variant. Efficacy of ARCT-154 was 56.6% (95% CI: 48.7- 63.3) against any COVID-19, and 95.3% (80.5-98.9) against severe COVID-19. ARCT-154 vaccination is well tolerated, immunogenic and efficacious, particularly against severe COVID-19 disease.