Biology subjects

Floyd, K. A.

Publications and source records attributed to Floyd, K. A..

6 recordsLinked to original sources

bioRxiv2026

Antigenic characterization of SARS-CoV-2 variants BA.3.2.1 and BA.3.2.2 in three animal models

BA.3.2, a variant of SARS-CoV-2 containing [~]40 mutations in its spike protein compared to its nearest ancestor, has spread globally since its first detection in South Africa in November 2024. Here, we report antigenic characterization of BA.3.2 viruses in three naive animal models, and visualize its antigenic phenotype in the context of SARS-CoV-2 evolution using antigenic cartography. We find that: (1) BA.3.2 is substantially antigenically divergent from existing SARS-CoV-2 variants; (2) infection with BA.3.2 in hamster and mouse animal models produces sera with lower homologous titer than infection with other variants. Both of these results may have implications for the selection of vaccine antigens.

microbiology↗

bioRxiv2025

The Synergy between a Silver-Ruthenium Antimicrobial and aminoglycosides is based on severe macromolecular damage

The rise of multidrug-resistant (MDR) bacterial pathogens, including uropathogenic Escherichia coli (UPEC), highlights the urgent need for alternative treatment strategies to restore antibiotic efficacy. The silver-ruthenium antimicrobial AGXX(R) exerts potent bactericidal effects through the production of reactive oxygen species (ROS); however, its potential synergy with antibiotics has not been thoroughly investigated. Here, we show that sublethal concentrations of AGXX(R) strongly enhance aminoglycoside-mediated killing across a diverse panel of Gram-negative and Gram-positive MDR clinical isolates, including highly aminoglycoside-resistant strains. Combinational treatments significantly reduced the effective concentrations of gentamicin, tobramycin, kanamycin, and amikacin required for bacterial killing. Mechanistic analyses revealed that AGXX(R)/aminoglycoside co-treatment induces pronounced intracellular ROS accumulation, resulting in severe proteotoxic stress, extensive protein aggregation, and DNA damage. Scavenging ROS abolished synergistic killing, establishing oxidative imbalance as the primary driver of the synergy between both antimicrobials. We further identify polyphosphate as a key bacterial defense mechanism that mitigates ROS accumulation, proteotoxicity, and genotoxic stress during combinational treatment. Moreover, AGXX(R)-aminoglycoside synergy was preserved in an artificial urine medium and across clinical UPEC isolates, underscoring its relevance to urinary tract infections. Together, these findings position AGXX(R) as a potent aminoglycoside adjuvant that restores antibiotic efficacy through ROS-driven macromolecular damage, supporting its development for combination therapies against MDR bacterial infections.

microbiology↗

bioRxiv2024

Eosinophils protect against SARS-CoV-2 following a vaccine breakthrough infection

Waning immunity and the emergence of immune evasive SARS-CoV-2 variants jeopardize vaccine efficacy leading to breakthrough infections. We have previously shown that innate immune cells play a critical role in controlling SARS-CoV-2. To investigate the innate immune response during breakthrough infections, we modeled breakthrough infections by challenging low-dose vaccinated mice with a vaccine-mismatched SARS-CoV-2 Beta variant. We found that low-dose vaccinated infected mice had a 2-log reduction in lung viral burden, but increased immune cell infiltration in the lung parenchyma, characterized by monocytes, monocyte-derived macrophages, and eosinophils. Single cell RNA-seq revealed viral RNA was highly associated with eosinophils that corresponded to a unique IFN-{gamma} biased signature. Antibody-mediated depletion of eosinophils in vaccinated mice resulted in increased virus replication and dissemination in the lungs, demonstrating that eosinophils in the lungs are protective during SARS-CoV-2 breakthrough infections. These results highlight the critical role for the innate immune response in vaccine mediated protection against SARS-CoV-2.

immunology↗

bioRxiv2021

Oxygen depletion and nitric oxide stimulate type IV MSHA pilus retraction in Vibrio cholerae via activation of the phosphodiesterase CdpA

Bacteria use surface appendages called type IV pili to perform diverse activities including DNA uptake, twitching motility, and attachment to surfaces. Dynamic extension and retraction of pili is often required for these activities, but the stimuli that regulate these dynamics remain poorly characterized. To study this question, we use the bacterial pathogen Vibrio cholerae, which uses mannose-sensitive hemagglutinin (MSHA) pili to attach to surfaces in aquatic environments as the first step in biofilm formation. Here, we find that V. cholerae cells retract MSHA pili and detach from a surface in microaerobic conditions. This response is dependent on the phosphodiesterase CdpA, which decreases intracellular levels of cyclic-di-GMP (c-di-GMP) under microaerobic conditions to induce MSHA pilus retraction. CdpA contains a putative NO-sensing NosP domain, and we demonstrate that nitric oxide (NO) is necessary and sufficient to stimulate CdpA-dependent detachment. Thus, we hypothesize that microaerobic conditions result in endogenous production of NO (or an NO-like molecule) in V. cholerae. Together, these results describe a regulatory pathway that allows V. cholerae to rapidly abort biofilm formation. More broadly, these results show how environmental cues can be integrated into the complex regulatory pathways that control pilus dynamic activity and attachment in bacterial species.

microbiology↗

bioRxiv2020

A Bacterial Signaling Network Controls Antibiotic Resistance by Regulating Anaplerosis of 2-oxoglutarate

Antibiotic resistance has become a global threat. In addition to acquiring resistance via horizontal gene transfer, bacteria can evade killing by temporarily modifying their cell envelope to prevent antibiotic-bacterial interactions. A critical gap in knowledge is how bacteria balance the metabolic needs of altering the cell envelope with the constant need to generate energy. Cross-regulation between two signaling networks in Escherichia coli increases resistance to positively charged antibiotics. We show that increased resistance is supported by metabolic re-wiring controlled by the QseB transcription factor. QseB controls the increase in 2-oxoglutarate required for lipid A modification, by upregulating three anaplerotic pathways that feed acetyl Co-A, succinate and fumarate into the TCA cycle. Exogenous addition of 2-oxoglutarate restores antibiotic resistance in the qseB deletion mutant. Antibiotic resistant clinical isolates bear mutations within QseB-mediated anaplerotic pathways. These findings are significant, because they uncover a previously unknown mechanism of metabolic control of antibiotic resistance.

microbiology↗

bioRxiv2019

Ciliary phosphatidylinositol phosphatase Inpp5e plays positive and negative regulatory roles in Shh signaling

Sonic hedgehog (Shh) signal transduction specifies ventral cell fates in the neural tube and is mediated by the Gli transcription factors that play both activator (GliA) and repressor (GliR) roles. Cilia are essential for Shh signal transduction and the ciliary phosphatidylinositol phosphatase, Inpp5e, is linked to Shh regulation. In the course of a forward genetic screen for recessive mouse mutants, we identified a functional null allele of Inpp5e, ridge top (rdg), with expanded ventral neural cell fates at E10.5. By E12.5, Inpp5erdg/rdg embryos displayed normal neural patterning and this correction over time required Gli3, the predominant repressor in neural patterning. Inpp5erdg function largely depended on the presence of cilia and on Smoothened, the obligate transducer of Shh signaling, indicating Inpp5e functions within the cilium to regulate the pathway. These data indicate that Inpp5e plays a more complicated role in Shh signaling than previously appreciated. We propose that Inpp5e attenuates Shh signaling in the neural tube through regulation of the relative timing of GliA and GliR production, which is important in understanding how duration of Shh signaling regulates neural tube patterning.\n\nSummary statementInpp5e attenuates Sonic hedgehog signal transduction through a combination of positive and negative regulatory roles that likely control the relative timing of Gli processing.

developmental biology↗