Biology subjects

Tarr, A. W.

Publications and source records attributed to Tarr, A. W..

4 recordsLinked to original sources

bioRxiv2025

An ultra-long heavy chain bovine antibody neutralizes SARS-CoV-2 and reacts broadly with sarbecoviruses.

The ongoing threat of new SARS-CoV-2 variants and other sarbecoviruses has driven efforts to develop broadly neutralizing monoclonal antibodies (mAbs). This study used immunized cattle, known for producing antibodies with ultra-long CDRH3 domains, to generate 33 mAbs, ten of which had ultra-long CDRH3s (>50 amino acids). Of these, mAbs P7 and 99, demonstrated broad and potent neutralization. Notably, mAb P7 neutralized all tested variants, including SARS-CoV-1, with IC50 values between 0.05 and 9.2 {micro}g/mL, and showed cross-reactivity with RBDs from various sarbecoviruses. Structural analysis revealed that mAb 99 binds the spike proteins RBD at the ACE2 binding site. Although the exact binding of P7 wasnt resolved, evidence suggests it targets a hidden epitope, promoting spike trimer dissociation via its extended CDRH3. In Syrian hamsters, both mAbs significantly reduced lung viral loads. These results support the potential of bovine-derived mAbs, particularly those with ultra-long CDRH3s, for future antiviral therapies.

immunology↗

bioRxiv2024

Wisteria floribunda agglutinin enhances Zaire ebolavirus entry through interactions at specific N-linked glycosylation sites on the virus glycoprotein complex

Entry of Zaire ebolavirus (EBOV) into a host cell is a complex process requiring interactions between the viral glycoproteins (GP) and cellular factors. These entry factors are cell-specific and can include cell surface lectins and phosphatidylserine receptors. NPC1 is critical to the late stage of the entry process. Entry has been demonstrated to be enhanced by interactions between the virion and surface-expressed lectins, which interact with carbohydrate moieties attached to the GP. In addition, soluble lectins, including mannose binding lectin (MBL), can enhance entry in vitro. However, the mechanism of lectin-mediated enhancement remains to be defined. This study investigated the potential of three plant lectins, Wisteria floribunda agglutinin (WFA), soybean agglutinin (SBA) and Galanthus nivalis agglutinin (GNA), which possess different carbohydrate binding specificities, to enhance EBOV entry by binding to the GP. WFA was observed to potently enhance entry of lentiviral pseudotype viruses (PVs) expressing the GP of three Ebolavirus species (Zaire, Sudan [SUDV] and Reston [RESTV]), with the greatest impact on EBOV. SBA had a modest enhancing effect on entry that was specific to EBOV, while GNA had no impact on entry of any of the Ebolavirus species. None of the lectins enhanced entry of control PVs expressing the surface proteins of other RNA viruses tested. WFA was demonstrated to bind directly with the EBOV-GP via the glycans, and mutational analysis implicated N238 as contributing to the interaction. Furthermore, enhancement was observed in both human and bat cell lines indicating a highly conserved mechanism of action. We conclude that binding of WFA to EBOV GP through interactions including the glycan at N238 results in GP alterations that enhance entry, providing evidence of a mechanism for lectin-mediated virus entry enhancement. Targeting lectin-ligand interactions presents a potential strategy for restricting Ebolavirus entry.

microbiology↗

bioRxiv2022

SARS-CoV-2 entry route impacts a range of downstream viral and cellular processes

SARS-CoV-2 entry is promoted by both cell-surface TMPRSS2 and endolysosomal cathepsins. To investigate the impact of differentially routed virions on host and viral processes, lung epithelial cells expressing distinct combinations of entry factors were infected with authentic viruses. Entry route determined early rates of viral replication and transcription, egress and inhibitor sensitivity, with differences observed between virus strains. Transcriptional profiling revealed that induction of innate immunity was correlated to viral genome and transcript abundance in infected cells. Surface entry triggered early activation of antiviral responses, reducing cumulative virion production, while endolysosomal entry delayed antiviral responses and prolonged virus shedding due to extended cell viability. The likely molecular footprints of escape from antiviral effector targeting were also recorded in viral genomes and correlated with entry route-dependent immune status of cells. TMPRSS2 orthologues from diverse mammals, but not zebra fish, facilitated infection enhancement, which was more pronounced for ancestral strains. Leveraging RNA-seq and scRNA-seq datasets from SARS-CoV-2 infected hamsters, we validate aspects of our model in vivo. In summary, we demonstrate that distinct cellular and viral processes are linked to viral entry route, collectively modulating virus shedding, cell-death rates and viral genome evolution.

microbiology↗

bioRxiv2019

Extraction-free direct PCR from dried serum spots permits HBV genotyping and RAS identification by Sanger and minION sequencing

In order to achieve the commitment made by the World Health Organisation to eliminate viral hepatitis by 2030, it is essential that clinicians can obtain basic sequencing data for hepatitis B virus (HBV) infected patients. While accurate diagnosis of HBV is achievable in most clinical settings, genotyping and identification of resistance-associated substitutions (RAS) present a practical challenge in regions with limited healthcare and biotechnology infrastructure. Here we outline two workflows for generating clinically relevant HBV sequence data directly from dried serum spot (DSS) cards without DNA extraction using either Sanger, or the portable MinION sequencing platforms. Data obtained from the two platforms were highly consistent and allowed determination of HBV genotype and RAS. This is the first demonstration of MinION sequencing from DSS, illustrating the broad utility of this sequencing technology. We demonstrated the clinical application of this technology using sera sampled on DSS cards obtained from both Iraq and Brazil. The sample stability provided by DSS cards, combined with the rapid PCR and sequencing protocols will enable regional/national centres to provide information relevant to patient management. By providing viable workflows for both the Sanger and MinION sequencing platforms, which vary greatly in the infrastructure and expertise required, we demonstrate that MinION sequencing is a viable method for HBV genotyping in resource-limited settings. These workflows could also be applied to sequencing of other blood borne DNA viruses and bacterial pathogens.

microbiology↗