Biology subjects

Kovacs, E.

Publications and source records attributed to Kovacs, E..

5 recordsLinked to original sources

bioRxiv2026

Acquisition of specific human respiratory tract binding of 2.3.4.4b H5N1 hemagglutinins requires multiple mutations

It has been suggested that the hemagglutinin of the human-infecting cattle-derived 2.3.4.4b virus A/Texas/34 (H5TX) requires only one mutation, namely Q226L, to switch from binding avian-type to human-type receptor preference. In this study, we examined the binding of H5TX Q226L, along with other key mutations, to sections of human trachea. We conclude that, while H5TX Q226L can bind human-type receptors, more than a single mutation is required for this protein to bind to human respiratory tract tissue. We also report changes in receptor-binding specificity of another 2.3.4.4b HA mutant, H5FR Q226L, associated with the presence of a multibasic cleavage site. This study offers insight into the determinants of evolution towards human-type receptor binding in currently circulating H5Nx viruses. It also emphasizes the importance of testing individual strains using additional methods, including tissue-based approaches, alongside synthetic glycans. ImportanceCurrently, H5N1 influenza A viruses are responsible for numerous zoonotic spillover events, from infecting birds to other mammals, including dairy cattle. Although no human-to-human transmission has been observed, several people have been infected. This host range expansion is typically linked to changes in one of the viral surface proteins, hemagglutinin, which can switch its preference from avian-type to human-type receptors. To better understand the potential of the currently circulating H5N1 virus to transmit among humans, we evaluated the effects of the Q226L mutation, in combination with other amino acid substitutions, on binding to the human trachea. We also studied the effect of the multibasic cleavage site, a specific motif present in highly pathogenic influenza strains, on receptor binding properties. These findings provide insight into the role of receptor binding in influenza infections.

microbiology↗

bioRxiv2026

H5N1 2.3.4.4b HA E190D and Q226H mutations, picked up as minority variants in a patient, result in an inability to bind sialic acid.

A human infection with clade 2.3.4.4b H5N1 influenza A virus in Canada revealed minority variants E190D and Q226H in the hemagglutinin (HA) receptor-binding site (RBS). Because mutations at positions 190 and 226 have been associated with altered receptor specificity in other influenza subtypes, we investigated their impact on receptor binding in H5 HA. Using a recombinant protein approach and an ELISA-based glycan-binding assay, we assessed binding to representative avian- and human-type sialylated glycans. Both single mutations and their combination resulted in a complete loss of detectable binding to the tested glycans. To evaluate whether this phenotype was background-dependent, Q226H was additionally introduced into two other H5 HA proteins, each representing a distinct clade. In both cases, the mutation similarly abolished receptor binding. These findings independently validate recent glycan microarray observations and demonstrate that the patient-derived E190D and Q226H substitutions severely impair receptor-binding capacity across multiple H5 backgrounds. Single mutations at key RBS residues in H5 often disrupt receptor binding rather than confer human-type receptor specificity, confirming complex mutational pathways required for adaptation to human-type receptors.

microbiology↗

bioRxiv2025

Thiamine transporter 2 and Janus kinase 2 inhibitor, fedratinib suppresses thermogenic activation of human neck area-derived adipocytes

IntroductionBrown adipocytes consume higher amounts of metabolic substrates and regulators including thiamine during adrenergic stimulation supporting heat generation. Our previous findings showed that fedratinib, a potent inhibitor of thiamine transporter (ThTr) 2 and Janus kinase 2 (JAK2), reduced thermogenic activity; however, the underlying molecular mechanisms remain elusive. MethodsPrimary human subcutaneous (SC) and deep neck (DN)-derived adipocytes were treated with dibutyryl (db)-cAMP, fedratinib, or the combination of the two compounds after differentiation. Global transcriptomic analysis was performed by bulk RNA-sequencing. Differentially expressed genes were subjected to pathway enrichment analysis. We also utilized publicly available single-cell RNA-sequencing datasets and adiposetissue.org to correlate ThTr2 expression in adipose tissue to clinical parameters of patient cohorts. Amino acid flux was measured by metabolomics. Results and discussionThTr2 expression was observed exclusively enriched in the adipocytes cluster within human brown and white adipose tissue. In response to ThTr2 inhibition, the db-cAMP-stimulated upregulation of the canonical thermogenic markers and proton leak respiration, which associates with UCP1-dependent heat generation, was prevented in both adipocyte types. RNA-sequencing found 40 and 41 downregulated genes potentially underlying the metabolic changes in SC and DN-derived adipocytes, respectively, which were involved in various biological pathways, including transcriptional regulation of brown and beige adipocytes differentiation, signaling by interleukins, nicotinamide salvaging, and gene and protein expression by JAK/STAT signaling after interleukin-12 stimulation. The expression of recently identified thermogenesis regulators, such as transglutaminase (TGM) 2 and inhibitor of DNA binding (ID) 1, was also abrogated by ThTr2 inhibition during adrenergic stimulation. Intriguingly, glutamate transporter (GLT) 1 and L-amino acid transporter (LAT) 2 expression was also attenuated by fedratinib, restricting amino acid consumption. Finally, we found that the expression of ThTr2 in human white adipose tissue was inversely correlated with body mass index, waist-hip ratio, leptin secretion, and plasma insulin, glucose, cholesterol and triacylglycerol levels, supporting the importance of thiamine metabolism in adipocyte and metabolic health. O_LIFedratinib prevented adrenergic-stimulated upregulation of thermogenic genes. C_LIO_LIThe consumption of amino acids and the expression of their transporters decreased by fedratinib during adrenergic stimulation. C_LIO_LIOxygen consumption and proton leak respiration reflecting heat generation were abrogated by fedratinib. C_LI

cell biology↗

bioRxiv2022

Monitoring correlates of SARS-CoV-2 infection in cell culture using two-photon microscopy and a novel fluorescent calcium-sensitive dye

The organism-wide effects of viral infection SARS-CoV-2 are well studied, but little is known about the dynamics of how the infection spreads in time among or within cells due to the scarcity of suitable high-resolution experimental systems. Two-photon (2P) imaging combined with a proper subcellular staining technique has been an effective tool for studying mechanisms at such resolutions and organelle levels. Herein, we report the development of a novel calcium sensor molecule along with a 2P-technique for identifying imaging patterns associated with cellular correlates of infection damage within the cells. The method works as a cell viability assay and also provides valuable information on how the calcium level and intracellular distribution are perturbed by the virus. Moreover, it allows the quantitative analysis of infection dynamics. This novel approach facilitates the study of the infection progression and the quantification of the effects caused by viral variants and viral load.

microbiology↗

bioRxiv2020

Reef Cover: a coral reef classification for global habitat mapping from biophysical remote sensing.

Coral reef management and conservation stand to benefit from improved high-resolution global mapping. Yet classifications employed in large-scale reef mapping to date are typically poorly defined, not shared or region-specific. Here we present Reef Cover, a new coral reef geomorphic zone classification, developed to support global-scale coral reef habitat mapping in a transparent and version-based framework. We developed scalable classes by focusing on attributes that can be observed remotely, but whose membership rules also reflect knowledge of reef formation, growth and functioning. Bridging the divide between earth observation data and geo-ecological knowledge of reefs, Reef Cover maximises the trade-off between applicability at global scales, and relevance and accuracy at local scales. We use the Caroline and Mariana Island chains in the Pacific as a case study to demonstrate use of the classification scheme and its scientific and conservation applications. The primary application of Reef Cover is the Allen Coral Atlas global coral reef mapping project, but the system will support bespoke reef mapping conducted at a variety of spatial scales.

systems biology↗