Biology subjects

Harari, S.

Publications and source records attributed to Harari, S..

7 recordsLinked to original sources

bioRxiv2026

Mutations to the HCoV-229E spike have counterbalancing effects on serum antibody neutralization and receptor binding

Human coronavirus 229E (HCoV-229E) is an endemic pathogen that causes repeated "common-cold" infections throughout life. Like other coronaviruses, it accumulates spike mutations that erode antibody immunity and enable reinfection. Here, we use pseudovirus deep mutational scanning to measure how mutations to the HCoV-229E spike affect its cell entry function, binding to its human APN receptor, and neutralization by human sera with a range of sensitivities to erosion by viral evolution. We find that both receptor binding and serum neutralization are affected by mutations across spike, including many that modulate these properties by affecting the balance of up versus down conformations of the spike receptor-binding domain (RBD). In particular, some mutations increase both receptor binding and serum neutralization by shifting the RBD to a more up conformation, suggesting that the HCoV-229E spike has evolved to shield key RBD neutralizing epitopes at the cost of less efficient receptor binding.

microbiology↗

bioRxiv2025

Functional and antigenic constraints on the Nipah virus fusion protein

Nipah virus is a highly pathogenic virus in the family Paramyxoviridae that utilizes two distinct surface glycoproteins to infect cells. The receptor-binding protein (RBP) binds host receptors whereas the fusion protein (F) merges viral and host membranes. Here, we use non-replicative pseudoviruses to safely measure the effects of all F single amino-acid residue mutations on its cell entry function and neutralization by monoclonal antibodies. We compare mutational tolerance in F with previous experimental measurements for RBP and show that F is much more functionally constrained than the RBP. We also identify mutationally intolerant sites on the F trimer surface and core that are critical for proper function, and describe mutations that are candidates for stabilizing F in the prefusion conformation for vaccine design. We quantify how F mutations affect neutralization by six monoclonal antibodies, and show that the magnitude of mutational effects on neutralization varies among antibodies. Our measurements of mutational effects on Nipah virus F predict the ability of the antibodies to neutralize the related Hendra virus. Overall, our work defines the functional and antigenic constraints on the F protein from an important zoonotic virus. ImportanceNipah virus sporadically spills over into humans, where it is often fatal. The Nipah fusion (F) protein is necessary for infection, and is a target for vaccines and antibody therapies. To better understand the constraints on this protein, we experimentally measured how [~]8,500 single amino-acid mutations to F affected its function using pseudoviruses that enable the safe study of protein mutants without the generation of actual replicative virus. We examined the effects of these mutations in the context of structural data and publicly available Nipah virus sequences to characterize the constraints that shape F protein evolution. This work has implications for understanding paramyxovirus fusion proteins, and informs the development of vaccines and monoclonal antibody therapies.

microbiology↗

bioRxiv2025

Spike mutations that affect the function and antigenicity of recent KP.3.1.1-like SARS-CoV-2 variants

SARS-CoV-2 is under strong evolutionary selection to acquire mutations in its spike protein that reduce neutralization by human polyclonal antibodies. Here we use pseudovirus-based deep mutational scanning to measure how mutations to the spike from the recent KP.3.1.1 SARS-CoV-2 strain affect cell entry, binding to ACE2 receptor, RBD up/down motion, and neutralization by human sera and clinically relevant antibodies. The spike mutations that most affect serum antibody neutralization sometimes differ between sera collected before versus after recent vaccination or infection, indicating these exposures shift the neutralization immunodominance hierarchy. The sites where mutations cause the greatest reduction in neutralization by post-vaccination or infection sera include receptor-binding domain (RBD) sites 475, 478 and 487, all of which have mutated in recent SARS-CoV-2 variants. Multiple mutations outside the RBD affect sera neutralization as strongly as any RBD mutations by modulating RBD up/down movement. Some sites that affect RBD up/down movement have mutated in recent SARS-CoV-2 variants. Finally, we measure how spike mutations affect neutralization by three clinically relevant SARS-CoV-2 antibodies: VYD222, BD55-1205, and SA55. Overall, these results illuminate the current constraints and pressures shaping SARS-CoV-2 evolution, and can help with efforts to forecast possible future antigenic changes that may impact vaccines or clinical antibodies. ImportanceThis study measures how mutations to the spike of a SARS-CoV-2 variant that circulated in early 2025 affect its function and recognition by both the polyclonal antibodies produced by the human immune system and monoclonal antibodies used as prophylactics. These measurements are made with a pseudovirus system that enables safe study of viral protein mutations using virions that can only infect cells once. The study identifies mutations that decrease recognition by current human antibody immunity; many of these mutations are increasingly being observed in new viral variants. It also shows the importance of mutations that move the spikes receptor binding domain up or down. Overall, these results are useful for forecasting viral evolution and assessing which newly emerging variants have reduced recognition by immunity and antibody prophylactics.

microbiology↗

bioRxiv2024

Diverse patterns of intra-host genetic diversity in chronically infected SARS-CoV-2 patients

In rare individuals with a severely immunocompromised system, chronic infections of SARS-CoV-2 may develop, where the virus replicates in the body for months. Sequencing of some chronic infections has uncovered dramatic adaptive evolution and fixation of mutations reminiscent of lineage-defining mutations of variants of concern (VOCs). This has led to the prevailing hypothesis that VOCs emerged from chronic infections. To examine the mutation dynamics and intra-host genomic diversity of SARS-CoV-2 during chronic infections, we focused on a cohort of nine immunocompromised individuals with chronic infections and performed longitudinal sequencing of viral genomes. We show that sequencing errors may cause erroneous inference of high genetic diversity, and to overcome this we used duplicate sequencing across patients and time-points, allowing us to distinguish errors from low frequency mutations. We further find recurrent low frequency mutations that we flag as most likely sequencing errors. This stringent approach allowed us to reliably infer low frequency mutations and their dynamics across time. We inferred a synonymous divergence rate of the virus of [~]2x10-6 mutations/base/day, consistent with the SARS-CoV-2 mutation rate estimated in tissue culture. The rate of non-synonymous divergence varied widely among the different patients. We highlight two patients with opposing patterns: in one patient the rate of divergence was zero, yet this patient harbored multiple presumably defective viruses at low frequencies throughout the infection. Another patient exhibited dramatic adaptive evolution, including clonal competition. Overall, our results suggest that the emergence of highly divergent variants from chronic infections is likely a very rare event and this emphasizes the need to better understand the conditions that allow such emergence events.

evolutionary biology↗

bioRxiv2024

Molecular basis of pathogenicity of the recently emerged FCoV-23 coronavirus

The ability of coronaviruses to recombine and cross species barriers affects human and animal health globally and is a pandemic threat. FCoV-23 is a recently emerged, highly pathogenic recombinant coronavirus responsible for a widespread outbreak of feline infectious peritonitis (FIP) likely linked to in-host viral evolution. Here, we report cryoEM structures of two FCoV-23 spike (S) isoforms explaining that the in-host loss of domain 0 observed in clinical samples enhances entry into cells and fusogenicity by facilitating protease access, leading to biotype switching and lethality. We show that FCoV-23 can use several aminopeptidase N (APN) orthologs as receptors and reveal the molecular determinants of receptor species tropism, including a glycan modulating human receptor utilization. We define antigenic relationships among alphacoronaviruses infecting humans and other mammalian species and identify a cross-reactive alphacoronavirus monoclonal antibody inhibiting FCoV-23 pseudovirus entry, paving the way for vaccine and therapeutic development targeting this highly pathogenic virus.

biochemistry↗

bioRxiv2023

Using big sequencing data to identify chronic SARS-Coronavirus-2 infections

The evolution of SARS-Coronavirus-2 (SARS-CoV-2) has been characterized by the periodic emergence of highly divergent variants, many of which may have arisen during chronic infections of immunocompromised individuals. Here, we harness a global phylogeny of [~]11.7 million SARS-CoV-2 genomes and search for clades composed of sequences with identical metadata (location, age, and sex) spanning more than 21 days. We postulate that such clades represent repeated sampling from the same chronically infected individual. A set of 271 such chronic-like clades was inferred, and displayed signatures of an elevated rate of adaptive evolution, in line with validated chronic infections. More than 70% of adaptive mutations present in currently circulating variants are found in BA.1 chronic-like clades that predate the circulating variants by months, demonstrating the predictive nature of such clades. We find that in chronic-like clades the probability of observing adaptive mutations is approximately 10-20 higher than that in global transmission chains. We next employ language models to find mutations most predictive of chronic infections and use them to infer hundreds of additional chronic-like clades in the absence of metadata and phylogenetic information. Our proposed approach presents an innovative method for mining extensive sequencing data and providing valuable insights into future evolutionary patterns.

evolutionary biology↗

bioRxiv2018

AccuNGS: a sequencing protocol for detection of ultra-rare variants reveals extensive variation in HIV during first days of infection

Mutations fuel evolution and facilitate adaptation to novel environments. However, characterizing the spectrum of mutations in a population is obscured by high error rates of next generation sequencing. Here, we present AccuNGS, a novel in vivo sequencing approach that detects variants as rare as 1:10,000. Applying it to 46 clinical samples taken from early infections of the human-infecting viruses HIV, RSV and CMV, revealed large differences in within-host genetic diversity among virus populations. Haplotype reconstruction revealed that increased diversity was mostly driven by multiple transmitted/founder viruses in HIV and CMV samples. Conversely, we detected an abundance of defective virus genomes (DVGs) in RSV samples, including hyper-edited genomes, nonsense mutations and single point deletions. Higher proportions of DVGs correlated with increased viral loads, suggesting increased cellular co-infection rates, which enable DVG persistence. AccuNGS establishes a general platform that allows detecting DVGs, and in general, rare variants that drive evolution.

bioinformatics↗