DNA origami vaccine (DoriVac) nanoparticles improve both humoral and cellular immune responses to infectious diseases (preprint)

Current SARS-CoV-2 vaccines have demonstrated robust induction of neutralizing antibodies and CD4+ T cell activation, however CD8+ responses are variable, and the duration of immunity and protection against variants are limited. Here we repurposed our DNA origami vaccine platform, DoriVac, for targeting infectious viruses, namely SARS-CoV-2, HIV, and Ebola. The DNA origami nanoparticle, conjugated with infectious-disease-specific HR2 peptides, which act as highly conserved antigens, and CpG adjuvant at precise nanoscale spacing, induced neutralizing antibodies, Th1 CD4+ T cells, and CD8+ T cells in naive mice, with significant improvement over a bolus control. Pre-clinical studies using lymph-node-on-a-chip systems validated that DoriVac, when conjugated with antigenic peptides or proteins, induced promising cellular immune responses in human cells. These results suggest that DoriVac holds potential as a versatile, modular vaccine platform, capable of inducing both humoral and cellular immunities. The programmability of this platform underscores its potential utility in addressing future pandemics.

Brain and Lung Cross-Protection against Ancestral or Emerging SARS-CoV-2 by Intranasal Lentiviral Vaccination in a New hACE2 Transgenic Murine Model (preprint)

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.

Full Brain and Lung Prophylaxis against SARS-CoV-2 by Intranasal Lentiviral Vaccination in a New hACE2 Transgenic Mouse Model or Golden Hamsters (preprint)

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.

Intranasal Immunization with a Lentiviral Vector Coding for SARS-CoV-2 Spike Protein Confers Vigorous Protection in Pre-Clinical Animal Models (preprint)

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.