RESUMO
BACKGROUND: Vaccines in emergency use are efficacious against COVID-19, yet vaccine-induced prevention against nasal SARS-CoV-2 infection remains suboptimal. METHODS: Since mucosal immunity is critical for nasal prevention, we investigated the efficacy of an intramuscular PD1-based receptor-binding domain (RBD) DNA vaccine (PD1-RBD-DNA) and intranasal live attenuated influenza-based vaccines (LAIV-CA4-RBD and LAIV-HK68-RBD) against SARS-CoV-2. FINDINGS: Substantially higher systemic and mucosal immune responses, including bronchoalveolar lavage IgA/IgG and lung polyfunctional memory CD8 T cells, were induced by the heterologous PD1-RBD-DNA/LAIV-HK68-RBD as compared with other regimens. When vaccinated animals were challenged at the memory phase, prevention of robust SARS-CoV-2 infection in nasal turbinate was achieved primarily by the heterologous regimen besides consistent protection in lungs. The regimen-induced antibodies cross-neutralized variants of concerns. Furthermore, LAIV-CA4-RBD could boost the BioNTech vaccine for improved mucosal immunity. INTERPRETATION: Our results demonstrated that intranasal influenza-based boost vaccination induces mucosal and systemic immunity for effective SARS-CoV-2 prevention in both upper and lower respiratory systems. FUNDING: This study was supported by the Research Grants Council Collaborative Research Fund, General Research Fund and Health and Medical Research Fund in Hong Kong; Outbreak Response to Novel Coronavirus (COVID-19) by the Coalition for Epidemic Preparedness Innovations; Shenzhen Science and Technology Program and matching fund from Shenzhen Immuno Cure BioTech Limited; the Health@InnoHK, Innovation and Technology Commission of Hong Kong; National Program on Key Research Project of China; donations from the Friends of Hope Education Fund; the Theme-Based Research Scheme.
Assuntos
Vacinas contra COVID-19 , COVID-19/prevenção & controle , Imunização Secundária , Vacinas contra Influenza , SARS-CoV-2 , Vacinas de DNA , Administração Intranasal , Animais , COVID-19/genética , COVID-19/imunologia , Vacinas contra COVID-19/genética , Vacinas contra COVID-19/imunologia , Chlorocebus aethiops , Modelos Animais de Doenças , Cães , Feminino , Células HEK293 , Humanos , Imunidade nas Mucosas , Vacinas contra Influenza/genética , Vacinas contra Influenza/imunologia , Células Madin Darby de Rim Canino , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Transgênicos , SARS-CoV-2/genética , SARS-CoV-2/imunologia , Vacinas Atenuadas/genética , Vacinas Atenuadas/imunologia , Vacinas de DNA/genética , Vacinas de DNA/imunologia , Células VeroRESUMO
BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) contains the furin cleavage Proline-Arginine-Arginine-Alanine (PRRA) motif in the S1/S2 region, which enhances viral pathogenicity but is absent in closely related bat and pangolin coronaviruses. Whether bat-like coronaviral variants without PRRA (∆PRRA) can establish natural infections in humans is unknown. METHODS: Here, we developed a duplex digital polymerase chain reaction assay to examine ∆PRRA variants in Vero-E6-propagated isolates, human organoids, experimentally infected hamsters, and coronavirus disease 2019 (COVID-19) patients. RESULTS: We found that SARS-CoV-2, as currently transmitting in humans, contained a quasispecies of wild-type, ∆PRRA variants and variants that have mutations upstream of the PRRA motif. Moreover, the ∆PRRA variants were readily detected despite being at a low intra-host frequency in transmitted founder viruses in hamsters and in COVID-19 patients, including in acute cases and a family cluster, with a prevalence rate of 52.9%. CONCLUSIONS: Our findings demonstrate that bat-like SARS-CoV-2ΔPRRA not only naturally exists but remains transmissible in COVID-19 patients, which has significant implications regarding the zoonotic origin and natural evolution of SARS-CoV-2.
