Structural insights of a highly potent pan-neutralizing SARS-CoV-2 human monoclonal antibody (preprint)

As the coronavirus disease 2019 (COVID-19) pandemic continues, there is a strong need for highly potent monoclonal antibodies (mAbs) that are resistant against severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) variants of concern (VoCs). To date there have been four major variants (Alpha, Beta, Gamma, Delta) that have tested the efficacy of the vaccines and have led to some breakthrough infections amongst vaccinated populations. Here, we evaluate the potency of a previously described mAb J08 against these variants using cell-based assays and delve into the molecular details of the binding interaction using cryo-EM. We show that mAb J08 is unique because it has low nanomolar affinity against the VoCs, binds high on the receptor binding domain (RBD) ridge and is therefore unaffected by most mutations, and can bind in the RBD-up and -down conformations. These findings further validate the phase II/III human clinical trial underway using mAb J08 as a monoclonal therapy. One sentence summaryMonoclonal antibody J08 can potently neutralize wild-type SARS-CoV-2 and variants of concern by binding to the ridge of the receptor binding domain in up and down conformations and thereby avoid the effects of current escape mutations.

Anti-Spike Antibodies and Neutralising Antibody Activity in People Living with HIV Vaccinated with COVID-19 mRNA-1273 Vaccine: A Prospective Cohort Study (preprint)

Background: Vaccines against COVID-19 are a powerful tool to control the current SARS-CoV-2 pandemic. A thorough description of their immunogenicity among people living with HIV (PLWHIV) is necessary. We aimed to assess the immunogenicity of the mRNA-1273 vaccine among PLWHIV.Methods: In this prospective cohort, adult PLWHIV outpatients were enrolled during the Italian vaccination campaign. Enrolment was allowed irrespective of ongoing combination antiretroviral therapy (ART), plasma HIV viral load and CD4+ T cell count. A two-dose regimen of mRNA-1273, with administrations performed 28 days apart, was employed. The primary outcomes were anti-spike (anti-S) antibody titres and neutralising antibody activity, assessed 28 days after completing the vaccination schedule, compared with individuals not affected by HIV (referred as healthy-donors, HDs). Findings: CD4+ T cell count groups and anti-nucleocapside (anti-N) positive serology were the only variables associated with anti-spike (anti-S) antibody titres (expressed as U/mL) and neutralising antibody activity. Anti-S antibodies were higher in COVID-19-experienced PLWHIV (median 12500 U/mL IQR [5704-12500]) than in COVID-19-naïve PLWHIV (median 2437 U/mL IQR [1485-4526]) but did not differ from those observed in COVID-19-experienced HDs (median 1077 U/mL IQR [702-7551]). Neutralising antibody activity in sera was higher in COVID-19-experienced PLWHIV (median 10888 IQR [2478-14416]) compared to COVID-19-naïve PLWHIV (median 1192 IQR [742-2421]) but was comparable to those observed in COVID-19-experienced HDs (median 20959 U/mL IQR [10060-31857]). When stratified according to CD4+ T cell count (<350 cells/μL, 350-500 cells/μL, >500 cells/μL), anti-S antibody titres (median 2173 U/mL [IQR 897-4109], 5763 IU/mL [IQR 4801-12500], 2449 U/mL [IQR 1524-5704]) were not lower to those observed among HDs (median 1425 U/mL [IQR 599-6131]). In addition, neutralising antibody activity, stratified according to the CD4+ T cell count (median 1314 [IQR 606-2477], 3329 IU/mL [IQR 1905-10508], 1227 U/mL [IQR 761-3032]), was similar to those displayed by HDs (median 2112 U/mL [IQR 719-8889]).Interpretation: Inoculation with mRNA-1273 vaccine given 4 weeks apart produced adequate immune responses in PLWHIV, who are well controlled on ART, irrespective of CD4+ T cell count and equivalent to individuals without HIV infection, supporting vaccination in PLWHIV.Funding: This study was partially supported by Italian Ministry of Health Ricerca Corrente 2021 and Grant Ricerca Finalizzata GR 2018-12365699, by Intesa San Paolo COVID-19 emergency 2020 funds, and by Fondazione Cariplo (INNATE-CoV).Declaration of Interest: All other authors declare no competing interests.Ethical Approval: The study protocol (286_2021) was approved by the INMI “Lazzaro Spallanzani” Ethics Committee (Roma, Italy),

COVID-eVax, an electroporated plasmid DNA vaccine candidate encoding the SARS-CoV-2 Receptor Binding Domain, elicits protective immune responses in animal models of COVID-19 (preprint)

The COVID-19 pandemic caused by the {beta}-coronavirus SARS-CoV-2 has made the development of safe and effective vaccines a critical global priority. To date, four vaccines have already been approved by European and American authorities for preventing COVID-19 but the development of additional vaccine platforms with improved supply and logistics profiles remains a pressing need. Here we report the preclinical evaluation of a novel COVID-19 vaccine candidate based on the electroporation of engineered, synthetic cDNA encoding a viral antigen in the skeletal muscle, a technology previously utilized for cancer vaccines. We constructed a set of prototype DNA vaccines expressing various forms of the SARS-CoV-2 Spike (S) protein and assessed their immunogenicity in animal models. Among them, COVID-eVax - a DNA plasmid encoding a secreted monomeric form of SARS-CoV-2 S protein RBD - induced the most potent anti-SARS-CoV-2 neutralizing antibody responses (including against the current most common variants of concern) and a robust T cell response. Upon challenge with SARS-CoV-2, immunized K18-hACE2 transgenic mice showed reduced weight loss, improved pulmonary function and significantly lower viral replication in the lungs and brain. COVID-eVax conferred significant protection to ferrets upon SARS-CoV-2 challenge. In summary, this study identifies COVID-eVax as an ideal COVID-19 vaccine candidate suitable for clinical development. Accordingly, a combined phase I-II trial has recently started in Italy.