Safety and immunogenicity of SARS-CoV-2 self-amplifying RNA vaccine expressing anchored RBD: a randomised, observer-blind, phase 1 study

BACKGROUNDVLPCOV-01 is a lipid nanoparticle-encapsulated self-amplifying RNA (saRNA) vaccine that expresses a membrane-anchored receptor-binding domain (RBD) derived from the SARS-CoV-2 spike protein. METHODSA phase 1 study of VLPCOV-01 was conducted at Medical Corporation Heishinkai OPHAC Hospital, Japan. Participants aged 18 to 55 or [≥]65 years who had completed two doses of the BNT162b2 mRNA vaccine 6 to 12 months previously were randomised to receive one intramuscular vaccination of 0{middle dot}3, 1{middle dot}0, or 3{middle dot}0 g VLPCOV-01, 30 g BNT162b2, or placebo between February 16, 2022, and March 17, 2022. Solicited adverse events were collected up to 6 days post-administration. Interim immunogenicity analyses included SARS-CoV-2 IgG and neutralising antibody titres. Follow-up for safety and immunogenicity evaluation is ongoing. (The trial is registered: jRCT2051210164). FINDINGS92 healthy adults were enrolled, with 60 participants receiving VLPCOV-01. No serious adverse events were reported up to 26 weeks, and no prespecified trial-halting events were met. VLPCOV-01 induced robust IgG titres against SARS-CoV-2 RBD protein that were maintained up to 26 weeks in non-elderly participants, with geometric means ranging from 5037 (95% CI 1272-19,940) at 0{middle dot}3 g to 12,873 (95% CI 937-17,686) at 3 g, in comparison to 3166 (95% CI 1619-6191) with 30 g BNT162b2. Among elderly participants, IgG titres at 26 weeks post-vaccination with 3 g VLPCOV-01 were 9865 (95% CI 4396-22138) compared to 4183 (95% CI 1436-12180) following vaccination with 30 g BNT162b2. Pseudovirus neutralising antibody responses were observed against multiple SARS-CoV-2 variants and strongly correlated with anti-SARS-CoV-2 IgG (r=0{middle dot}950, p<0{middle dot}001). INTERPRETATIONVLPCOV-01 is immunogenic following low dose administration, with anti-SARS-CoV-2 immune responses comparable to BNT162b2. These findings support further development of VLPCOV-01 as a COVID-19 booster vaccine and the potential for saRNA vectors as a vaccine platform. FUNDINGSupported by AMED, Grant No. JP21nf0101627.

Modeling SARS-CoV-2 infection and its individual differences with ACE2-expressing human iPS cells

Genetic differences are a primary reason for differences in the susceptibility and severity of coronavirus disease 2019 (COVID-19). Because induced pluripotent stem (iPS) cells maintain the genetic information of the donor, they can be used to model individual differences in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in vitro. Notably, undifferentiated human iPS cells themselves cannot be infected bySARS-CoV-2. Using adenovirus vectors, here we found that human iPS cells expressing the SARS-CoV-2 receptor angiotensin-converting enzyme 2 (ACE2) (ACE2-iPS cells) can be infected with SARS-CoV-2. In infected ACE2-iPS cells, the expression of SARS-CoV-2 nucleocapsid protein, the budding of viral particles, the production of progeny virus, double membrane spherules, and double-membrane vesicles were confirmed. We also evaluated COVID-19 therapeutic drugs in ACE2-iPS cells and confirmed the strong antiviral effects of Remdesivir, EIDD-2801, and interferon-beta. In addition, we performed SARS-CoV-2 infection experiments on ACE2-iPS/ES cells from 8 individuals. Male iPS/ES cells were more capable of producing the virus as compared with female iPS/ES cells. These findings suggest that ACE2-iPS cells can not only reproduce individual differences in SARS-CoV-2 infection in vitro, but they are also a useful resource to clarify the causes of individual differences in COVID-19 due to genetic differences. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/432218v1_ufig1.gif" ALT="Figure 1"> View larger version (112K): org.highwire.dtl.DTLVardef@165ec06org.highwire.dtl.DTLVardef@6a9d67org.highwire.dtl.DTLVardef@1840dd3org.highwire.dtl.DTLVardef@a7a4bb_HPS_FORMAT_FIGEXP M_FIG C_FIG

Generation of human bronchial organoids for SARS-CoV-2 research

Coronavirus disease 2019 (COVID-19) is a disease that causes fatal disorders including severe pneumonia. To develop a therapeutic drug for COVID-19, a model that can reproduce the viral life cycle and evaluate the drug efficacy of anti-viral drugs is essential. In this study, we established a method to generate human bronchial organoids (hBO) from commercially available cryopreserved human bronchial epithelial cells and examined whether they could be used as a model for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) research. Our hBO contain basal, club, ciliated, and goblet cells. Angiotensin-converting enzyme 2 (ACE2), which is a receptor for SARS-CoV-2, and transmembrane serine proteinase 2 (TMPRSS2), which is an essential serine protease for priming spike (S) protein of SARS-CoV-2, were highly expressed. After SARS-CoV-2 infection, not only the intracellular viral genome, but also progeny virus, cytotoxicity, pyknotic cells, and moderate increases of the type I interferon signal could be observed. Treatment with camostat, an inhibitor of TMPRSS2, reduced the viral copy number to 2% of the control group. Furthermore, the gene expression profile in SARS-CoV-2-infected hBO was obtained by performing RNA-seq analysis. In conclusion, we succeeded in generating hBO that can be used for SARS-CoV-2 research and COVID-19 drug discovery. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/115600v2_ufig1.gif" ALT="Figure 1"> View larger version (99K): org.highwire.dtl.DTLVardef@13a6908org.highwire.dtl.DTLVardef@1c59300org.highwire.dtl.DTLVardef@362167org.highwire.dtl.DTLVardef@1cb31ed_HPS_FORMAT_FIGEXP M_FIG C_FIG