Biology subjects

Cipolla, M.

Publications and source records attributed to Cipolla, M..

4 recordsLinked to original sources

bioRxiv2020

A Broadly Neutralizing Macaque Monoclonal Antibody Against the HIV-1 V3-Glycan Patch

A small fraction of HIV-1 infected humans develop potent broadly neutralizing antibodies (bNAbs) against HIV-1 that can protect macaques from infection with simian immunodeficiency HIV chimeric virus (SHIV). Similarly, a small number of macaques infected with SHIVs also develop broadly neutralizing serologic activity, but less is known about the nature of these simian antibodies. Here we report on a monoclonal antibody, Ab1485, isolated from a macaque infected with SHIVAD8 that developed broadly neutralizing serologic activity mapping to the V3-glycan region of HIV-1 Env. Ab1485 neutralizes 38.1 % of HIV-1 isolates in a panel of 42 pseudoviruses with a geometric mean IC50 of 0.055 g/ml and SHIVAD8 with an IC50 of 0.028 g/ml. Ab1485 binds to the V3-glycan epitope in a glycan-dependent manner as determined by ELISA and neutralization assays with JRCSF mutant viruses. A 3.5 [A] cryo-electron microscopy structure of Ab1485 in complex with a native-like SOSIP Env trimer showed conserved contacts with the N332gp120 glycan and gp120 GDIR peptide motif, but in a distinct Env-binding orientation relative to human V3/N332gp120 glycan-targeting bNAbs. Finally, intravenous infusion of Ab1485 protected macaques from a high dose intrarectal challenge with SHIVAD8. We conclude that macaques can develop bNAbs against the V3-glycan patch that resemble human V3-glycan bNAbs. Significance statementRhesus macaques infected with SHIV are an important model for evaluating HIV-1 prevention and therapy strategies and can also be used to evaluate humoral immune responses to candidate HIV-1 vaccines, but whether macaques produce human-like bNAbs has not been evaluated. Like HIV-1 infected humans, 10-20% of the SHIVAD8 challenged macaques develop low levels of neutralizing antibodies, and only one macaque has developed broad and potent serologic neutralizing activity. We have examined the antibody response of this macaque (CE8J) and we report on the cloning and molecular characterization of a bNAb produced in this elite neutralizing non-human primate, its structure bound to an HIV-1 Env trimer, and the implications for development of vaccines targeting the V3-glycan patch of Env.

immunology↗

bioRxiv2020

Escape from neutralizing antibodies by SARS-CoV-2 spike protein variants

Neutralizing antibodies elicited by prior infection or vaccination are likely to be key for future protection of individuals and populations against SARS-CoV-2. Moreover, passively administered antibodies are among the most promising therapeutic and prophylactic anti-SARS-CoV-2 agents. However, the degree to which SARS-CoV-2 will adapt to evade neutralizing antibodies is unclear. Using a recombinant chimeric VSV/SARS-CoV-2 reporter virus, we show that functional SARS-CoV-2 S protein variants with mutations in the receptor binding domain (RBD) and N-terminal domain that confer resistance to monoclonal antibodies or convalescent plasma can be readily selected. Notably, SARS-CoV-2 S variants that resist commonly elicited neutralizing antibodies are now present at low frequencies in circulating SARS-CoV-2 populations. Finally, the emergence of antibody-resistant SARS-CoV-2 variants that might limit the therapeutic usefulness of monoclonal antibodies can be mitigated by the use of antibody combinations that target distinct neutralizing epitopes.

microbiology↗

bioRxiv2020

Measuring SARS-CoV-2 neutralizing antibody activity using pseudotyped and chimeric viruses

The emergence of SARS-CoV-2 and the ensuing explosive epidemic of COVID19 disease has generated a need for assays to rapidly and conveniently measure the antiviral activity of SARS-CoV-2-specific antibodies. Here, we describe a collection of approaches based on SARS-CoV-2 spike-pseudotyped, single-cycle, replication-defective human immunodeficiency virus type-1 (HIV-1) and vesicular stomatitis virus (VSV), as well as a replication-competent VSV/SARS-CoV-2 chimeric virus. While each surrogate virus exhibited subtle differences in the sensitivity with which neutralizing activity was detected, the neutralizing activity of both convalescent plasma and human monoclonal antibodies measured using each virus correlated quantitatively with neutralizing activity measured using an authentic SARS-CoV-2 neutralization assay. The assays described herein are adaptable to high throughput and are useful tools in the evaluation of serologic immunity conferred by vaccination or prior SARS-CoV-2 infection, as well as the potency of convalescent plasma or human monoclonal antibodies.

microbiology↗

bioRxiv2020

Convergent Antibody Responses to SARS-CoV-2 Infection in Convalescent Individuals

During the COVID-19 pandemic, SARS-CoV-2 infected millions of people and claimed hundreds of thousands of lives. Virus entry into cells depends on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (S). Although there is no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-21-5. Here we report on 149 COVID-19 convalescent individuals. Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal neutralizing titers ranging from undetectable in 33% to below 1:1000 in 79%, while only 1% showed titers >1:5000. Antibody cloning revealed expanded clones of RBD-specific memory B cells expressing closely related antibodies in different individuals. Despite low plasma titers, antibodies to three distinct epitopes on RBD neutralized at half-maximal inhibitory concentrations (IC50s) as low as single digit ng/mL. Thus, most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective.

immunology↗