Biology subjects

Franzetti Pellanda, A.

Publications and source records attributed to Franzetti Pellanda, A..

4 recordsLinked to original sources

bioRxiv2026

Dissociation kinetics and avidity gate SARS-CoV-2 neutralization by HR2 stem helix antibodies

SARS-CoV-2 evolution has reduced the efficacy of clinical monoclonal antibodies, underscoring the need for therapeutics targeting conserved viral regions. The Spike (S) heptad repeat 2 (HR2) stem helix is highly conserved across SARS-CoV-2 variants and related betacoronaviruses. Although antibodies to this region can neutralize infection, their natural occurrence and evolution remain poorly understood. We previously identified human neutralizing antibodies to a conserved peptide within this region (HR2 coldspot). Here, we show that plasma IgG reactivity to this region remains rare, even after repeated antigen exposure. Longitudinal analysis over 30 months revealed continued somatic hypermutation of HR2-specific antibodies, yet none surpassed the potency or breadth of hr2.016, which emerged shortly after primary infection. Crystal structures of four HR2 stem helix antibodies revealed convergent recognition across distinct antibody lineages. Comparison of hr2.016 with its non-neutralizing clonal relative hr2.086 showed that structural convergence masks distinct binding kinetics. Surface plasmon resonance and molecular dynamics simulations revealed a more stable interaction network for hr2.016, with slower dissociation and prolonged S residence time. Neutralization required the IgG format, supporting an avidity-driven mechanism. Together, these findings define kinetic and avidity constraints governing neutralization at the HR2 stem helix and position hr2.016 as a resilient therapeutic candidate.

immunology↗

bioRxiv2022

Maturation of SARS-CoV-2 Spike-specific memory B cells drives resilience to viral escape

Memory B cells (MBCs) generate rapid antibody responses upon secondary encounter with a pathogen. Here, we investigated the kinetics, avidity and cross-reactivity of serum antibodies and MBCs in 155 SARS-CoV-2 infected and vaccinated individuals over a 16-month timeframe. SARS-CoV-2-specific MBCs and serum antibodies reached steady-state titers with comparable kinetics in infected and vaccinated individuals. Whereas MBCs of infected individuals targeted both pre- and postfusion Spike (S), most vaccine-elicited MBCs were specific for prefusion S, consistent with the use of prefusion-stabilized S in mRNA vaccines. Furthermore, a large fraction of MBCs recognizing postfusion S cross-reacted with human betacoronaviruses. The avidity of MBC-derived and serum antibodies increased over time resulting in enhanced resilience to viral escape by SARS-CoV-2 variants, including Omicron BA.1 and BA.2 sub-lineages, albeit only partially for BA.4 and BA.5 sublineages. Overall, the maturation of high-affinity and broadly-reactive MBCs provides the basis for effective recall responses to future SARS-CoV-2 variants.

immunology↗

bioRxiv2021

SARS-CoV-2 immune evasion by variant B.1.427/B.1.429

SARS-CoV-2 entry is mediated by the spike (S) glycoprotein which contains the receptor-binding domain (RBD) and the N-terminal domain (NTD) as the two main targets of neutralizing antibodies (Abs). A novel variant of concern (VOC) named CAL.20C (B.1.427/B.1.429) was originally detected in California and is currently spreading throughout the US and 29 additional countries. It is unclear whether antibody responses to SARS-CoV-2 infection or to the prototypic Wuhan-1 isolate-based vaccines will be impacted by the three B.1.427/B.1.429 S mutations: S13I, W152C and L452R. Here, we assessed neutralizing Ab responses following natural infection or mRNA vaccination using pseudoviruses expressing the wildtype or the B.1.427/B.1.429 S protein. Plasma from vaccinated or convalescent individuals exhibited neutralizing titers, which were reduced 3-6 fold against the B.1.427/B.1.429 variant relative to wildtype pseudoviruses. The RBD L452R mutation reduced or abolished neutralizing activity of 14 out of 35 RBD-specific monoclonal antibodies (mAbs), including three clinical-stage mAbs. Furthermore, we observed a complete loss of B.1.427/B.1.429 neutralization for a panel of mAbs targeting the N-terminal domain due to a large structural rearrangement of the NTD antigenic supersite involving an S13I-mediated shift of the signal peptide cleavage site. These data warrant closer monitoring of signal peptide variants and their involvement in immune evasion and show that Abs directed to the NTD impose a selection pressure driving SARS-CoV-2 viral evolution through conventional and unconventional escape mechanisms.

immunology↗

bioRxiv2021

Clonal dissection of immunodominance and cross-reactivity of the CD4+ T cell response to SARS-CoV-2

The identification of CD4+ T cell epitopes is essential for the design of effective vaccines capable of inducing neutralizing antibodies and long-term immunity. Here we demonstrate in COVID-19 patients a robust CD4+ T cell response to naturally processed SARS-CoV-2 Spike and Nucleoprotein, including effector, helper and memory T cells. By characterizing 2,943 Spike-reactive T cell clones, we found that 34% of the clones and 93% of the patients recognized a conserved immunodominant region encompassing residues S346-365 in the RBD and comprising three nested HLA-DR and HLA-DP restricted epitopes. By using pre- and post-COVID-19 samples and Spike proteins from alpha and beta coronaviruses, we provide in vivo evidence of cross-reactive T cell responses targeting multiple sites in the SARS-CoV-2 Spike protein. The possibility of leveraging immunodominant and cross-reactive T helper epitopes is instrumental for vaccination strategies that can be rapidly adapted to counteract emerging SARS-CoV-2 variants.

immunology↗