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biorxiv; 2022.
Preprint in English | bioRxiv | ID: ppzbmed-10.1101.2022.03.15.484542


The SARS-CoV-2 Omicron variant of concern comprises three sublineages designated BA.1, BA.2, and BA.3, with BA.2 steadily replacing the globally dominant BA.1. We show that the large number of BA.1 and BA.2 spike mutations severely dampen plasma neutralizing activity elicited by infection or seven clinical vaccines, with cross-neutralization of BA.2 being consistently more potent than that of BA.1, independent of the vaccine platform and number of doses. Although mRNA vaccines induced the greatest magnitude of Omicron BA.1 and BA.2 plasma neutralizing activity, administration of a booster based on the Wuhan-Hu-1 spike sequence markedly increased neutralizing antibody titers and breadth against BA.1 and BA.2 across all vaccines evaluated. Our data suggest that although BA.1 and BA.2 evade polyclonal neutralizing antibody responses, current vaccine boosting regimens may provide sufficient protection against Omicron-induced disease.

biorxiv; 2021.
Preprint in English | bioRxiv | ID: ppzbmed-10.1101.2021.12.19.473391


Numerous safe and effective COVID-19 vaccines have been developed that utilize various delivery technologies and engineering strategies. The influence of the SARS-CoV-2 spike (S) glycoprotein conformation on antibody responses induced by vaccination or infection in humans remains unknown. To address this question, we compared plasma antibodies elicited by six globally-distributed vaccines or infection and observed markedly higher binding titers for vaccines encoding a prefusion-stabilized S relative to other groups. Prefusion S binding titers positively correlated with plasma neutralizing activity, indicating that physical stabilization of the prefusion conformation enhances protection against SARS-CoV-2. We show that almost all plasma neutralizing activity is directed to prefusion S, in particular the S1 subunit, and that variant cross-neutralization is mediated solely by RBD-specific antibodies. Our data provide a quantitative framework for guiding future S engineering efforts to develop vaccines with higher resilience to the emergence of variants and longer durability than current technologies.

biorxiv; 2021.
Preprint in English | bioRxiv | ID: ppzbmed-10.1101.2021.12.12.472269


The recently emerged SARS-CoV-2 Omicron variant harbors 37 amino acid substitutions in the spike (S) protein, 15 of which are in the receptor-binding domain (RBD), thereby raising concerns about the effectiveness of available vaccines and antibody therapeutics. Here, we show that the Omicron RBD binds to human ACE2 with enhanced affinity relative to the Wuhan-Hu-1 RBD and acquires binding to mouse ACE2. Severe reductions of plasma neutralizing activity were observed against Omicron compared to the ancestral pseudovirus for vaccinated and convalescent individuals. Most (26 out of 29) receptor-binding motif (RBM)-directed monoclonal antibodies (mAbs) lost in vitro neutralizing activity against Omicron, with only three mAbs, including the ACE2-mimicking S2K146 mAb, retaining unaltered potency. Furthermore, a fraction of broadly neutralizing sarbecovirus mAbs recognizing antigenic sites outside the RBM, including sotrovimab, S2X259 and S2H97, neutralized Omicron. The magnitude of Omicron-mediated immune evasion and the acquisition of binding to mouse ACE2 mark a major SARS-CoV-2 mutational shift. Broadly neutralizing sarbecovirus mAbs recognizing epitopes conserved among SARS-CoV-2 variants and other sarbecoviruses may prove key to controlling the ongoing pandemic and future zoonotic spillovers.

ssrn; 2021.
Preprint in English | PREPRINT-SSRN | ID: ppzbmed-10.2139.ssrn.3918861


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),

medrxiv; 2021.
Preprint in English | medRxiv | ID: ppzbmed-10.1101.2021.08.12.21261976


Antibodies against cationic platelet chemokine, platelet factor 4 (PF4/CXCL4) have been described in heparin-induced thrombocytopenia (HIT) but also in patients positive for anti-phospholipid antibodies (aPL) even in the absence of heparin treatment and HIT-related clinical manifestations. Anti-PF4 antibodies have been recently described also in subjects who developed thrombosis with thrombocytopenia syndrome (TTS) in association with adenoviral vector-based, but not with mRNA-based COVID-19 vaccines. We investigated whether COVID-19 vaccination affects the production of anti-PF4 immunoglobulins detectable by solid phase assay in aPL-positive patients and their ability to induce in vitro platelet activation. Anti-PF4 were found in 9/126 aPL-positive patients, 4/50 COVID-19, 9/49 other infections and 1/50 aPL-negative systemic lupus erythematosus patients. Clinical manifestations of TTS were not observed in any aPL patient positive for anti-PF4, whose sera failed to cause platelet aggregations. The administration of COVID-19 vaccines did not affect the production of anti-PF4 immunoglobulins or their ability to cause platelet aggregation in 44 aPL-positive patients tested before and after vaccination. In conclusion, heparin treatment-independent anti-PF4 antibodies can be found in aPL-positive patients and asymptomatic carriers, but their presence, titer as well as in vitro effect on platelet activation are not affected by COVID-19 vaccination.