Publications by authors named "Chiara Silacci-Fregni"

Little information is available about the nature of the immune response in children after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or vaccination. The aim of this study is to define the seroprevalence and the features of the antibody response in children of Southern Switzerland during the different waves of Coronavirus Disease 2019 (COVID-19) pandemic. By analyzing 756 sera collected from children aged 0 to 16 years admitted to the Institute of Pediatrics of Southern Switzerland during the prepandemic period (before March 2020) and the first four pandemic waves (between March 2020 and June 2022), we investigated binding titers, cross-reactivity, and neutralizing properties of the serum antibodies against SARS-CoV-2 variants.

View Article and Find Full Text PDF

Currently circulating SARS-CoV-2 variants have acquired convergent mutations at hot spots in the receptor-binding domain (RBD) of the spike protein. The effects of these mutations on viral infection and transmission and the efficacy of vaccines and therapies remains poorly understood. Here we demonstrate that recently emerged BQ.

View Article and Find Full Text PDF

Currently circulating SARS-CoV-2 variants acquired convergent mutations at receptor-binding domain (RBD) hot spots. Their impact on viral infection, transmission, and efficacy of vaccines and therapeutics remains poorly understood. Here, we demonstrate that recently emerged BQ.

View Article and Find Full Text PDF

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 time frame. SARS-CoV-2-specific MBCs and serum antibodies reached steady-state titers with comparable kinetics in infected and vaccinated individuals.

View Article and Find Full Text PDF

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron sublineages carry distinct spike mutations resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters elicit plasma-neutralizing antibodies against Omicron BA.1, BA.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF
Article Synopsis
  • - Memory B cells can last a lifetime and quickly turn into antibody-producing cells when they encounter an antigen again, but their relationship with circulating plasmablasts is not fully understood.
  • - A study using single-cell sequencing revealed that in two healthy individuals, the memory B cell populations were largely made up of large clonal families of IgM, IgA, and IgG2 antibodies, while IgG1 families, particularly those for recall antigens, were smaller.
  • - Long-term analysis showed that the memory B cell families remained stable over time, and many of the newly formed plasmablasts originated from these long-term memory B cells, indicating that they play an ongoing role in the immune response.
View Article and Find Full Text PDF

SARS-CoV-2 Omicron sublineages carry distinct spike mutations and represent an antigenic shift resulting in escape from antibodies induced by previous infection or vaccination. We show that hybrid immunity or vaccine boosters result in potent plasma neutralizing activity against Omicron BA.1 and BA.

View Article and Find Full Text PDF

Patients on dialysis are at risk of severe course of SARS-CoV-2 infection. Understanding the neutralizing activity and coverage of SARS-CoV-2 variants of vaccine-elicited antibodies is required to guide prophylactic and therapeutic COVID-19 interventions in this frail population. By analyzing plasma samples from 130 hemodialysis and 13 peritoneal dialysis patients after two doses of BNT162b2 or mRNA-1273 vaccines, we found that 35% of the patients had low-level or undetectable IgG antibodies to SARS-CoV-2 Spike (S).

View Article and Find Full Text PDF

The recently emerged SARS-CoV-2 Omicron variant encodes 37 amino acid substitutions in the spike protein, 15 of which are in the receptor-binding domain (RBD), thereby raising concerns about the effectiveness of available vaccines and antibody-based therapeutics. Here we show that the Omicron RBD binds to human ACE2 with enhanced affinity, relative to the Wuhan-Hu-1 RBD, and binds to mouse ACE2. Marked reductions in neutralizing activity were observed against Omicron compared to the ancestral pseudovirus in plasma from convalescent individuals and from individuals who had been vaccinated against SARS-CoV-2, but this loss was less pronounced after a third dose of vaccine.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF
Article Synopsis
  • Researchers used human monoclonal antibodies (humAbs) to explore how tetanus neurotoxin affects neurons and assess these antibodies as a potential alternative to hyperimmune sera for preventing and treating tetanus in mice.
  • They identified two highly effective tetanus neurotoxin-specific antibodies that block the toxin's ability to bind to and enter neurons, providing insights into the disease's cellular mechanisms.
  • The findings indicate that these antibodies could not only prevent experimental tetanus when administered beforehand but also effectively neutralize the toxin even after exposure, suggesting promising applications for human treatment in future clinical trials.
View Article and Find Full Text PDF

The spillovers of betacoronaviruses in humans and the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants highlight the need for broad coronavirus countermeasures. We describe five monoclonal antibodies (mAbs) cross-reacting with the stem helix of multiple betacoronavirus spike glycoproteins isolated from COVID-19 convalescent individuals. Using structural and functional studies, we show that the mAb with the greatest breadth (S2P6) neutralizes pseudotyped viruses from three different subgenera through the inhibition of membrane fusion, and we delineate the molecular basis for its cross-reactivity.

View Article and Find Full Text PDF

The recent emergence of SARS-CoV-2 variants of concern and the recurrent spillovers of coronaviruses into the human population highlight the need for broadly neutralizing antibodies that are not affected by the ongoing antigenic drift and that can prevent or treat future zoonotic infections. Here we describe a human monoclonal antibody designated S2X259, which recognizes a highly conserved cryptic epitope of the receptor-binding domain and cross-reacts with spikes from all clades of sarbecovirus. S2X259 broadly neutralizes spike-mediated cell entry of SARS-CoV-2, including variants of concern (B.

View Article and Find Full Text PDF

An ideal therapeutic anti-SARS-CoV-2 antibody would resist viral escape, have activity against diverse sarbecoviruses, and be highly protective through viral neutralization and effector functions. Understanding how these properties relate to each other and vary across epitopes would aid the development of therapeutic antibodies and guide vaccine design. Here we comprehensively characterize escape, breadth and potency across a panel of SARS-CoV-2 antibodies targeting the receptor-binding domain (RBD).

View Article and Find Full Text PDF

Background: Hospital healthcare workers (HCW), in particular those involved in the clinical care of COVID-19 cases, are presumably exposed to a higher risk of acquiring the disease than the general population.

Methods: Between April 16 and 30, 2020 we conducted a prospective, SARS-CoV-2 seroprevalence study in HCWs in Southern Switzerland. Participants were hospital personnel with varying COVID-19 exposure risk depending on job function and working site.

View Article and Find Full Text PDF

The recent emergence of SARS-CoV-2 variants of concern (VOC) and the recurrent spillovers of coronaviruses in the human population highlight the need for broadly neutralizing antibodies that are not affected by the ongoing antigenic drift and that can prevent or treat future zoonotic infections. Here, we describe a human monoclonal antibody (mAb), designated S2X259, recognizing a highly conserved cryptic receptor-binding domain (RBD) epitope and cross-reacting with spikes from all sarbecovirus clades. S2X259 broadly neutralizes spike-mediated entry of SARS-CoV-2 including the B.

View Article and Find Full Text PDF

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.

View Article and Find Full Text PDF

Some Plasmodium falciparum repetitive interspersed families of polypeptides (RIFINs)-variant surface antigens that are expressed on infected erythrocytes-bind to the inhibitory receptor LAIR1, and insertion of DNA that encodes LAIR1 into immunoglobulin genes generates RIFIN-specific antibodies. Here we address the general relevance of this finding by searching for antibodies that incorporate LILRB1, another inhibitory receptor that binds to β2 microglobulin and RIFINs through their apical domains. By screening plasma from a cohort of donors from Mali, we identified individuals with LILRB1-containing antibodies.

View Article and Find Full Text PDF

The SARS-CoV-2 spike (S) glycoprotein contains an immunodominant receptor-binding domain (RBD) targeted by most neutralizing antibodies (Abs) in COVID-19 patient plasma. Little is known about neutralizing Abs binding to epitopes outside the RBD and their contribution to protection. Here, we describe 41 human monoclonal Abs (mAbs) derived from memory B cells, which recognize the SARS-CoV-2 S N-terminal domain (NTD) and show that a subset of them neutralize SARS-CoV-2 ultrapotently.

View Article and Find Full Text PDF

Transmission of SARS-CoV-2 is uncontrolled in many parts of the world; control is compounded in some areas by the higher transmission potential of the B.1.1.

View Article and Find Full Text PDF

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) transmission is uncontrolled in many parts of the world, compounded in some areas by higher transmission potential of the B1.1.7 variant now seen in 50 countries.

View Article and Find Full Text PDF