ABSTRACT
Human Angiotensin-Converting Enzyme 2 (hACE2) is the major receptor enabling host cell invasion by SARS-CoV-2 via interaction with Spike glycoprotein. The murine ACE2 ortholog does not interact efficiently with SARS-CoV-2 Spike and therefore the conventional laboratory mouse strains are not permissive to SARS-CoV-2 replication. Here, we generated new hACE2 transgenic mice, which harbor the hACE2 gene under the human keratin 18 promoter, in C57BL/6 "HHD-DR1" background. HHD-DR1 mice are fully devoid of murine Major Histocompatibility Complex (MHC) molecules of class-I and -II and express only MHC molecules from Human Leukocyte Antigen (HLA) HLA 02.01, DRA01.01, DRB1.01.01 alleles, widely expressed in human populations. We selected three transgenic strains, with various hACE2 mRNA expression levels and distinctive profiles of lung and/or brain permissiveness to SARS-CoV-2 replication. Compared to the previously available B6.K18-ACE22Prlmn/JAX mice, which have limited permissiveness to SARS-CoV-2 Omicron replication, these three new hACE2 transgenic strains display higher levels of hACE2 mRNA expression, associated with high permissiveness to the replication of SARS-CoV-2 Omicron sub-variants. As a first application, one of these MHC- and ACE2-humanized strains was successfully used to show the efficacy of a lentiviral vector-based COVID-19 vaccine candidate.
Subject(s)
Severe Acute Respiratory Syndrome , COVID-19 , Pemphigus, Benign FamilialABSTRACT
Memory B-cell and antibody responses to the SARS-CoV-2 spike protein contribute to long-term immune protection against severe COVID-19, which can also be prevented by antibody-based interventions. Here, wide SARS-CoV-2 immunoprofiling in COVID-19 convalescents combining serological, cellular and monoclonal antibody explorations, revealed humoral immunity coordination. Detailed characterization of a hundred SARS-CoV-2 spike memory B-cell monoclonal antibodies uncovered diversity in their repertoire and antiviral functions. The latter were influenced by the targeted spike region with strong Fc-dependent effectors to the S2 subunit and potent neutralizers to the receptor binding domain. Amongst those, Cv2.1169 and Cv2.3194 antibodies cross-neutralized SARS-CoV-2 variants of concern including Omicron BA.1 and BA.2. Cv2.1169, isolated from a mucosa-derived IgA memory B cell, demonstrated potency boost as IgA dimers and therapeutic efficacy as IgG antibodies in animal models. Structural data provided mechanistic clues to Cv2.1169 potency and breadth. Thus, potent broadly neutralizing IgA antibodies elicited in mucosal tissues can stem SARS-CoV-2 infection, and Cv2.1169 and Cv2.3194 are prime candidates for COVID-19 prevention and treatment.
Subject(s)
COVID-19 , AtaxiaABSTRACT
As the COVID-19 pandemic continues and new SARS-CoV-2 variants of concern emerge, the adaptive immunity initially induced by the first-generation COVID-19 vaccines wains and needs to be strengthened and broadened in specificity. Vaccination by the nasal route induces mucosal humoral and cellular immunity at the entry point of SARS-CoV-2 into the host organism and has been shown to be the most effective for reducing viral transmission. The lentiviral vaccination vector (LV) is particularly suitable for this route of immunization because it is non-cytopathic, non-replicative and scarcely inflammatory. Here, to set up an optimized cross-protective intranasal booster against COVID-19, we generated an LV encoding stabilized Spike of SARS-CoV-2 Beta variant (LV::SBeta-2P). mRNA vaccine primed and -boosted mice, with waning primary humoral immunity at 4 months post-vaccination, were boosted intranasally with LV::SBeta-2P. Strong boost effect was detected on cross-sero-neutralizing activity and systemic T-cell immunity. In addition, mucosal anti-Spike IgG and IgA and lung resident B cells, effector memory and resident T cells were productively induced, correlating with complete pulmonary protection against the SARS-CoV-2 Delta variant, demonstrating the suitability of the LV::SBeta-2P vaccine candidate as an intranasal booster against COVID-19.
Subject(s)
COVID-19 , Encephalomyelitis, Acute DisseminatedABSTRACT
COVID-19 vaccines already in use or in clinical development may have safety concerns, limited immunogenicity in high-risk groups or reduced efficacy against emerging SARS-CoV-2 variants. In addition, although the neurotropism of SARS-CoV-2 is well established, the vaccine strategies currently developed have not taken into account the protection of the central nervous system. Here, we generated a transgenic mouse strain expressing the human Angiotensin Converting Enzyme 2, with unprecedented brain as well as lung permissibility to SARS-CoV-2 replication. Using this stringent transgenic model, we demonstrated that a non-integrative lentiviral vector, encoding for the spike glycoprotein of the ancestral Wuhan SARS-CoV-2, used in intramuscular prime and intranasal boost elicits sterilizing protection of lung and brain against both the Wuhan and the most genetically distant Manaus P.1 SARS-CoV-2 variants. Beyond the induction of strong neutralizing antibodies, the mechanism underlying this broad protection spectrum involves a robust protective spike-specific CD8+ T-cell immunity, unaffected by the recent mutations accumulated in the emerging SARS-CoV-2 variants.
Subject(s)
COVID-19ABSTRACT
Non-integrative, non-cytopathic and non-inflammatory lentivectors are particularly suitable for mucosal vaccination and recently emerge as a promising strategy to elicit sterilizing prophylaxis against SARS-CoV-2 in preclinical animal models. Here, we demonstrate that a single intranasal administration of a lentivector encoding a prefusion form of SARS-CoV-2 spike glycoprotein induces full protection of respiratory tracts and totally avoids pulmonary inflammation in the susceptible hamster model. More importantly, we generated a new transgenic mouse strain, expressing the human Angiotensin Converting Enzyme 2, with unprecedent brain permissibility to SARS-CoV-2 replication and developing a lethal disease in <4 days post infection. Even though the neurotropism of SARS-CoV-2 is now well established, so far other vaccine strategies under development have not taken into account the protection of central nervous system. Using our highly stringent transgenic model, we demonstrated that an intranasal booster immunization with the developed lentivector vaccine candidate achieves full protection of both respiratory tracts and central nervous system against SARS-CoV-2.
Subject(s)
Pneumonia , Severe Acute Respiratory SyndromeABSTRACT
We developed a potent vaccination strategy, based on lentiviral vector (LV), capable of inducing neutralizing antibodies specific to the Spike glycoprotein (S) of SARS-CoV-2, the etiologic agent of CoronaVirus Disease 2019 (COVID-19). Among several LV encoding distinct variants of S, a single one encoding the full-length, membrane anchored S (LV::SFL) triggered high antibody titers in mice, with neutralization activities comparable to patients recovered from COVID-19. LV::SFL systemic vaccination in mice, in which the expression of the CoV2 receptor hACE2 was induced by transduction of the respiratory tract cells by an adenoviral type 5 (Ad5) vector, despite an intense serum neutralizing activity, only {approx}1 log10 reduction of lung viral loads was observed after SARS-CoV2 challenge. We thus explored the strategy of targeting the immune response to the upper respiratory tract through an intranasal boost administration. Even though, after a prime and target regimen, the systemic neutralizing activity did not increase substantially, {approx}5 log10 decrease in lung viral loads was achieved, with the loads in some animals under the limit of detection of a highly sensitive RT-PCR assay. The conferred protection also avoided largely pulmonary inflammation. We confirmed the vaccine efficacy and inhibition of lung inflammation using both integrative and non-integrative LV platforms in golden hamsters, naturally permissive to SARS-CoV2 replication and restituting human COVID-19 physiopathology. Our results provide the proof-of-principle evidence of marked prophylactic effects of an LV-based vaccination strategy against SARS-CoV-2 in two pre-clinical animal models and designate the intranasal LV::SFL-based immunization as a vigorous and promising vaccine approach against COVID-19.