Biology subjects

Horowitz, J. C.

Publications and source records attributed to Horowitz, J. C..

9 recordsLinked to original sources

bioRxiv2026

Heterogeneous causes of acute respiratory distress syndrome correlate with distinct peripheral polyunsaturated fatty acid metabolites

Acute Respiratory Distress Syndrome (ARDS), a heterogeneous syndrome of hypoxic respiratory failure secondary to dysregulated pulmonary inflammation, is caused by diverse insults. Because of this heterogeneity, mechanisms and treatments are difficult to study. As a treatment, n-3 polyunsaturated fatty acid (PUFA) supplementation has had mixed results. PUFAs and downstream oxylipins are important to pulmonary inflammation but are not well defined in ARDS. We hypothesized that differences in fatty acid metabolism, as measured by levels of n-3 and n-6 PUFAs and oxylipins, are associated with differences in ARDS outcomes, ARDS causes, and inflammation. To test this, PUFAs/oxylipins were measured by LC MS/MS in plasma samples from 90 patients with ARDS. Inflammatory cytokines (IL-6, IL-8) were measured by ELISA. Multivariate linear regressions modeled the relationship between PUFAs/oxylipins, inflammation, and ARDS mortality, severity and cause. Multiple n-3 and n-6 PUFA derived oxylipins were decreased in severe ARDS. We did not detect differences in PUFAs/oxylipins by mortality. PUFAs/oxylipins varied by cause of ARDS, especially between patients with sepsis and those with trauma. Furthermore, specific oxylipins were associated with IL-6 and IL-8. Based on our identification of oxylipins that vary by disease severity and injury, these metabolites should be considered as potential biomarkers and mechanisms of lung repair biomarkers. Furthermore, differences in PUFAs did not directly correlate with changes in oxylipins, suggesting differences in lipid metabolism by etiology of injury. Further consideration of differences in lipid metabolism in ARDS could identify potential subgroups that could benefit from n-3 PUFA supplementation or other therapies.

molecular biology↗

bioRxiv2024

Immune Evasion, Cell-Cell Fusion, and Spike Stability of the SARS-CoV-2 XEC Variant: Role of Glycosylation Mutations at the N-terminal Domain

SARS-CoV-2 continues to evolve, producing new variants that drive global COVID-19 surges. XEC, a recombinant of KS.1.1 and KP.3.3, contains T22N and F59S mutations in the spike proteins N-terminal domain (NTD). The T22N mutation, similar to the DelS31 mutation in KP.3.1.1, introduces a potential N-linked glycosylation site in XEC. In this study, we examined the neutralizing antibody (nAb) response and mutation effects in sera from bivalent-vaccinated healthcare workers, BA.2.86/JN.1 wave-infected patients, and XBB.1.5 monovalent-vaccinated hamsters, assessing responses to XEC alongside D614G, JN.1, KP.3, and KP.3.1.1. XEC demonstrated significantly reduced neutralization titers across all cohorts, largely due to the F59S mutation. Notably, removal of glycosylation sites in XEC and KP.3.1.1 substantially restored nAb titers. Antigenic cartography analysis revealed XEC to be more antigenically distinct from its common ancestral BA.2.86/JN.1 compared to KP.3.1.1, with the F59S mutation as a determining factor. Similar to KP.3.1.1, XEC showed reduced cell-cell fusion relative to its parental KP.3, a change attributed to the T22N glycosylation. We also observed reduced S1 shedding for XEC and KP.3.1.1, which was reversed by ablation of T22N and DelS31 glycosylation mutations, respectively. Molecular modeling suggests that T22N and F59S mutations of XEC alters hydrophobic interactions with adjacent spike protein residues, impacting both conformational stability and neutralization. Overall, our findings underscore the pivotal role of NTD mutations in shaping SARS-CoV-2 spike biology and immune escape mechanisms.

molecular biology↗

bioRxiv2024

Neutralization and Stability of JN.1-derived LB.1, KP.2.3, KP.3 and KP.3.1.1 Subvariants

During the summer of 2024, COVID-19 cases surged globally, driven by variants derived from JN.1 subvariants of SARS-CoV-2 that feature new mutations, particularly in the N-terminal domain (NTD) of the spike protein. In this study, we report on the neutralizing antibody (nAb) escape, infectivity, fusion, and stability of these subvariants--LB.1, KP.2.3, KP.3, and KP.3.1.1. Our findings demonstrate that all of these subvariants are highly evasive of nAbs elicited by the bivalent mRNA vaccine, the XBB.1.5 monovalent mumps virus-based vaccine, or from infections during the BA.2.86/JN.1 wave. This reduction in nAb titers is primarily driven by a single serine deletion (DelS31) in the NTD of the spike, leading to a distinct antigenic profile compared to the parental JN.1 and other variants. We also found that the DelS31 mutation decreases pseudovirus infectivity in CaLu-3 cells, which correlates with impaired cell-cell fusion. Additionally, the spike protein of DelS31 variants appears more conformationally stable, as indicated by reduced S1 shedding both with and without stimulation by soluble ACE2, and increased resistance to elevated temperatures. Molecular modeling suggests that the DelS31 mutation induces a conformational change that stabilizes the NTD and strengthens the NTD-Receptor-Binding Domain (RBD) interaction, thus favoring the down conformation of RBD and reducing accessibility to both the ACE2 receptor and certain nAbs. Additionally, the DelS31 mutation introduces an N-linked glycan modification at N30, which shields the underlying NTD region from antibody recognition. Our data highlight the critical role of NTD mutations in the spike protein for nAb evasion, stability, and viral infectivity, and suggest consideration of updating COVID-19 vaccines with antigens containing DelS31.

molecular biology↗

bioRxiv2024

PAI-1 Interaction with Sortilin Related Receptor-1 is Required for Lung Fibrosis

Plasminogen activator inhibitor-1 (PAI-1) has been previously shown to promote lung fibrosis via a mechanism that requires an intact vitronectin (VTN) binding site. In the present study, employing two distinct murine fibrosis models, we find that VTN is not required for PAI-1 to drive lung scarring. This result suggested the existence of a previously unrecognized profibrotic PAI-1-protein interaction involving the VTN-binding site for PAI-1. Using an unbiased proteomic approach, we identified sortilin related receptor 1 (SorlA) as the most highly enriched PAI-1 interactor in the fibrosing lung. We next investigated the role of SorlA in pulmonary fibrosis and found that SorlA deficiency protected against lung scarring in a murine model. We further show that, while VTN deficiency does not influence fibrogenesis in the presence or absence of PAI-1, SorlA is required for PAI-1 to promote scarring. These results, together with data showing increased SorlA levels in human IPF lung tissue, support a novel mechanism through which the potent profibrotic mediator PAI-1 drives lung fibrosis and implicate SorlA as a new therapeutic target in IPF treatment.

pathology↗

bioRxiv2024

Characteristics of JN.1-derived SARS-CoV-2 subvariants SLip, FLiRT, and KP.2 in neutralization escape, infectivity and membrane fusion

SARS-CoV-2 variants derived from the immune evasive JN.1 are on the rise worldwide. Here, we investigated JN.1-derived subvariants SLip, FLiRT, and KP.2 for their ability to be neutralized by antibodies in bivalent-vaccinated human sera, XBB.1.5 monovalent-vaccinated hamster sera, sera from people infected during the BA.2.86/JN.1 wave, and class III monoclonal antibody (Mab) S309. We found that compared to parental JN.1, SLip and KP.2, and especially FLiRT, exhibit increased resistance to COVID-19 bivalent-vaccinated human sera and BA.2.86/JN.1-wave convalescent sera. Interestingly, antibodies in XBB.1.5 monovalent vaccinated hamster sera robustly neutralized FLiRT and KP.2 but had reduced efficiency for SLip. These JN.1 subvariants were resistant to neutralization by Mab S309. In addition, we investigated aspects of spike protein biology including infectivity, cell-cell fusion and processing, and found that these subvariants, especially SLip, had a decreased infectivity and membrane fusion relative to JN.1, correlating with decreased spike processing. Homology modeling revealed that L455S and F456L mutations in SLip reduced local hydrophobicity in the spike and hence its binding to ACE2. In contrast, the additional R346T mutation in FLiRT and KP.2 strengthened conformational support of the receptor-binding motif, thus counteracting the effects of L455S and F456L. These three mutations, alongside D339H, which is present in all JN.1 sublineages, alter the epitopes targeted by therapeutic Mabs, including class I and class III S309, explaining their reduced sensitivity to neutralization by sera and S309. Together, our findings provide insight into neutralization resistance of newly emerged JN.1 subvariants and suggest that future vaccine formulations should consider JN.1 spike as immunogen, although the current XBB.1.5 monovalent vaccine could still offer adequate protection.

microbiology↗

bioRxiv2024

Distinct Patterns of SARS-CoV-2 BA.2.87.1 and JN.1 Variants in Immune Evasion, Antigenicity and Cell-Cell Fusion

The rapid evolution of SARS-CoV-2 variants presents a constant challenge to the global vaccination effort. In this study, we conducted a comprehensive investigation into two newly emerged variants, BA.2.87.1 and JN.1, focusing on their neutralization resistance, infectivity, antigenicity, cell-cell fusion, and spike processing. Neutralizing antibody (nAb) titers were assessed in diverse cohorts, including individuals who received a bivalent mRNA vaccine booster, patients infected during the BA.2.86/JN.1-wave, and hamsters vaccinated with XBB.1.5-monovalent vaccine. We found that BA.2.87.1 shows much less nAb escape from WT-BA.4/5 bivalent mRNA vaccination and JN.1-wave breakthrough infection sera compared to JN.1 and XBB.1.5. Interestingly. BA.2.87.1 is more resistant to neutralization by XBB.15-monovalent-vaccinated hamster sera than BA.2.86/JN.1 and XBB.1.5, but efficiently neutralized by a class III monoclonal antibody S309, which largely fails to neutralize BA.2.86/JN.1. Importantly, BA.2.87.1 exhibits higher levels of infectivity, cell-cell fusion activity, and furin cleavage efficiency than BA.2.86/JN.1. Antigenically, we found that BA.2.87.1 is closer to the ancestral BA.2 compared to other recently emerged Omicron subvariants including BA.2.86/JN.1 and XBB.1.5. Altogether, these results highlight immune escape properties as well as biology of new variants and underscore the importance of continuous surveillance and informed decision-making in the development of effective vaccines.

microbiology↗

bioRxiv2023

Immune Evasion, Infectivity, and Fusogenicity of SARS-CoV-2 Omicron BA.2.86 and FLip Variants

Evolution of SARS-CoV-2 requires the reassessment of current vaccine measures. Here, we characterized BA.2.86 and the XBB-lineage variant FLip by investigating their neutralization alongside D614G, BA.1, BA.2, BA.4/5, XBB.1.5, and EG.5.1 by sera from 3-dose vaccinated and bivalent vaccinated healthcare workers, XBB.1.5-wave infected first responders, and monoclonal antibody (mAb) S309. We assessed the biology of the variant Spikes by measuring viral infectivity and membrane fusogenicity. BA.2.86 is less immune evasive compared to FLip and other XBB variants, consistent with antigenic distances. Importantly, distinct from XBB variants, mAb S309 was unable to neutralize BA.2.86, likely due to a D339H mutation based on modeling. BA.2.86 had relatively high fusogenicity and infectivity in CaLu-3 cells but low fusion and infectivity in 293T-ACE2 cells compared to some XBB variants, suggesting a potentially differences conformational stability of BA.2.86 Spike. Overall, our study underscores the importance of SARS-CoV-2 variant surveillance and the need for updated COVID-19 vaccines.

microbiology↗

bioRxiv2023

RAB7 deficiency impairs pulmonary artery endothelial function and promotes pulmonary hypertension

Pulmonary arterial hypertension (PAH) is a devastating and progressive disease with limited treatment options. Endothelial dysfunction plays a central role in development and progression of PAH, yet the underlying mechanisms are incompletely understood. The endosome-lysosome system is important to maintain cellular health and the small GTPase RAB7 regulates many functions of this system. Here, we explored the role of RAB7 in endothelial cell (EC) function and lung vascular homeostasis. We found reduced expression of RAB7 in ECs from PAH patients. Endothelial haploinsufficiency of RAB7 caused spontaneous PH in mice. Silencing of RAB7 in ECs induced broad changes in gene expression revealed via RNA sequencing and RAB7 silenced ECs showed impaired angiogenesis, expansion of a senescent cell fraction, combined with impaired endolysosomal trafficking and degradation, which suggests inhibition of autophagy at the pre-degradation level. Further, mitochondrial membrane potential and oxidative phosphorylation were decreased, and glycolysis was enhanced. Treatment with the RAB7 activator ML-098 reduced established PH in chronic hypoxia/SU5416 rats. In conclusion, we demonstrate here for the first time the fundamental impairment of EC function by loss of RAB7 that leads to PH and show RAB7 activation as a potential therapeutic strategy in a preclinical model of PH.

physiology↗

bioRxiv2023

A role for Toll-like receptor 3 in lung vascular remodeling associated with SARS-CoV-2 infection

Cardiovascular sequelae of severe acute respiratory syndrome (SARS) coronavirus-2 (CoV-2) disease 2019 (COVID-19) contribute to the complications of the disease. One potential complication is lung vascular remodeling, but the exact cause is still unknown. We hypothesized that endothelial TLR3 insufficiency contributes to lung vascular remodeling induced by SARS-CoV-2. In the lungs of COVID-19 patients and SARS-CoV-2 infected Syrian hamsters, we discovered thickening of the pulmonary artery media and microvascular rarefaction, which were associated with decreased TLR3 expression in lung tissue and pulmonary artery endothelial cells (ECs). In vitro, SARS-CoV-2 infection reduced endothelial TLR3 expression. Following infection with mouse-adapted (MA) SARS-CoV-2, TLR3 knockout mice displayed heightened pulmonary artery remodeling and endothelial apoptosis. Treatment with the TLR3 agonist polyinosinic:polycytidylic acid reduced lung tissue damage, lung vascular remodeling, and endothelial apoptosis associated with MA SARS-CoV-2 infection. In conclusion, repression of endothelial TLR3 is a potential mechanism of SARS-CoV-2 infection associated lung vascular remodeling and enhancing TLR3 signaling is a potential strategy for treatment.

molecular biology↗