Biology subjects

Rosen, D. A.

Publications and source records attributed to Rosen, D. A..

6 recordsLinked to original sources

bioRxiv2025

Molecular response to the non-lytic peptide bac7 (1-35) triggers disruption of Klebsiella pneumoniae biofilm

Klebsiella pneumoniae is becoming increasingly difficult to treat as multidrug-resistant (MDR) strains become more prevalent. The formation of biofilm heightens this threat by embedding bacterial cells in a polysaccharide-rich matrix that limits antibiotic penetration. Here we dissect the anti-biofilm bovine host-defense cathelicidin peptide fragment bac7 (1-35), exploring its anti-biofilm mechanism, evaluating its ability to curb dissemination of hypervirulent K. pneumoniae, and testing its breadth of activity against diverse clinical isolates. Transcriptomic profiling revealed that bac7(1-35) simultaneously compromises the bacterial membrane and inhibits ribosomal function, a dual assault that precipitates rapid biofilm collapse and blocks bacterial spread. Further, the peptide eradicated biofilms produced by the strongest MDR clinical isolates in the Multidrug-Resistant Organism Repository and Surveillance Network (MRSN) diversity panel. Although bac7 (1-35) kills bacterial cells via a cytosolic mechanism, membrane interaction profiles varied among MRSN isolates, correlating with differential peptide translocation. In a delayed-treatment murine skin-abscess model, bac7 (1-35) halted in vivo dissemination of the hypervirulent strain NTUH-K2044. Collectively, these results delineate a multifaceted mode of action for bac7 (1-35) and underscore its therapeutic promise against biofilm-associated MDR K. pneumoniae infections. Author SummaryKlebsiella pneumoniae is a top-priority pathogen for new therapies, with many strains already approaching pan-drug resistant status. Biofilm formation further complicates treatment, yet biofilm-active therapeutics have not reached the clinic, in part because we still lack a detailed understanding of how to disrupt these impenetrable structures. Antimicrobial peptides are promising candidates and have shown biofilm-disruption potential. Here we provide mechanistic insight into how a host defense peptide dismantles pre-formed K. pneumoniae biofilms. We find that the peptides dual targeting of bacterial membranes and ribosomes triggers dispersal from the biofilm state and concomitantly downregulates factors required for surface attachment and extracellular matrix production. This mechanism involves a protein that, to our knowledge, has not been characterized in K. pneumoniae. Our findings reveal a switch that can be leveraged to reprogram biofilm maintenance toward dispersal in K. pneumoniae, advancing the path to peptide-based antibiofilm therapeutics.

microbiology↗

bioRxiv2024

Antibody responses in Klebsiella pneumoniae bloodstream infection: a cohort study

BackgroundKlebsiella pneumonia (Kpn) is the fourth leading cause of infection-related deaths globally, yet little is known about human antibody responses to invasive Kpn. In this study, we sought to determine whether the O-specific polysaccharide (OPS) antigen, a vaccine candidate, is immunogenic in humans with Kpn bloodstream infection (BSI). We also sought to define the cross-reactivity of human antibody responses among structurally related Kpn OPS subtypes and to assess the impact of capsule production on OPS-targeted antibody binding and function. MethodsWe measured plasma antibody responses to OPS (and MrkA, a fimbrial protein) in a cohort of patients with Kpn BSI and compared these with controls, including a cohort of healthy individuals and a cohort of individuals with Enterococcus BSI. We performed flow cytometry to measure the impact of Kpn capsule production on whole cell antibody binding and complement deposition, utilizing patient isolates with variable levels of capsule production and isogenic capsule-deficient strains derived from these isolates. FindingsWe enrolled 69 patients with Kpn BSI. Common OPS serotypes accounted for 57/69 (83%) of infections. OPS was highly immunogenic in patients with Kpn BSI, and peak OPS-IgG antibody responses in patients were 10 to 30-fold higher than antibody levels detected in healthy controls, depending on the serotype. There was significant cross-reactivity among structurally similar OPS subtypes, including the O1v1/O1v2, O2v1/O2v2 and O3/O3b subtypes. Physiological amounts of capsule produced by both hyperencapsulated and non-hyperencapsulated Kpn significantly inhibited OPS-targeted antibody binding and function. InterpretationOPS was highly immunogenic in patients with Kpn BSI, supporting its potential as a candidate vaccine antigen. The strong cross-reactivity observed between similar OPS subtypes in humans with Kpn BSI suggests that it may not be necessary to include all subtypes in an OPS-based vaccine. However, these observations are tempered by the fact that capsule production, even in non-highly encapsulated strains, has the potential to interfere with OPS antibody binding. This may limit the effectiveness of vaccines that exclusively target OPS. FundingNational Institute of Allergy and Infectious Diseases at the National Institutes of Health. Research in ContextO_ST_ABSEvidence before this studyC_ST_ABSDespite the potential of O-specific polysaccharide (OPS) as a vaccine antigen against Klebsiella pneumoniae (Kpn), the immunogenicity of OPS in humans remains largely unstudied, creating a significant knowledge gap with regard to vaccine development. A search of PubMed for publications up to March 18, 2024, using the terms "Klebsiella pneumoniae" and "O-specific polysaccharide" or "O-antigen" or "lipopolysaccharide" revealed no prior studies addressing OPS antibody responses in humans with Kpn bloodstream infections (BSI). One prior study1 evaluated antibody response to a single lipopolysaccharide (which contains one subtype of OPS) in humans with invasive Kpn infection; however, in this study OPS typing of the infecting strains and target antigen were not described. Added value of this studyOur investigation into OPS immunogenicity in a human cohort marks a significant advance. Analyzing plasma antibody responses in 69 patients with Kpn BSI, we found OPS to be broadly immunogenic across all the types and subtypes examined, and there was significant cross-reactivity among structurally related OPS antigens. We also demonstrated that Kpn capsule production inhibit OPS antibody binding and the activation of complement on the bacterial surface, even in classical Kpn strains expressing lower levels of capsule. Implications of all the available evidenceWhile the immunogenicity and broad cross-reactivity of OPS in humans with Kpn BSI suggests it is a promising vaccine candidate, the obstruction of OPS antibody binding and engagement by physiologic levels of Kpn capsule underscores the potential limitations of an exclusively OPS-antigen based vaccine for Kpn. Our study provides insights for the strategic development of vaccines aimed at combating Kpn infections, an important antimicrobial resistant pathogen.

microbiology↗

bioRxiv2023

A heptavalent O-antigen bioconjugate vaccine exhibits differential functional antibody responses against diverse Klebsiella pneumoniae isolates

Klebsiella pneumoniae is a concerning pathogen that is now the leading cause of neonatal sepsis and is increasingly difficult to treat due to heightened antibiotic resistance. Thus, there is an urgent need for preventive and effective immunotherapies targeting K. pneumoniae. Vaccination represents a tractable approach to combat this resistant bacterium in some settings; however, there is currently not a licensed K. pneumoniae vaccine available. K. pneumoniae surface polysaccharides, including the terminal O-antigen polysaccharides of lipopolysaccharide, have long been attractive candidates for vaccine inclusion. Herein we describe the generation of a bioconjugate vaccine targeting seven of the predominant O-antigen subtypes in K. pneumoniae. Each of the seven bioconjugates were immunogenic in isolation, with limited cross-reactivity among subtypes. Vaccine-induced antibodies demonstrated varying degrees of binding to a wide variety of K. pneumoniae strains, including suspected hypervirulent strains, all expressing different O-antigen and capsular polysaccharide combinations. Further, sera from vaccinated mice induced complement-mediated killing of many of these K. pneumoniae strains. Finally, we found that increased quantity of capsule interferes with O-antigen antibodies ability to bind and mediate killing of some K. pneumoniae strains, including those carrying hypervirulence-associated genes. Taken together, these data indicate that this novel heptavalent O-antigen bioconjugate vaccine formulation exhibits promising efficacy against some, but not all, K. pneumoniae isolates.

immunology↗

bioRxiv2022

Linking movement and dive data to prey distribution models: new insights in foraging behaviour and potential pitfalls of movement analyses

BackgroundAnimal movement data are regularly used to infer foraging behaviour and relationships to environmental characteristics, often to help identify critical habitat. To characterize foraging, movement models make a set of assumptions rooted in theory, for example, time spent foraging in an area increases with higher prey density. MethodsWe assessed the validity of these assumptions by associating horizontal movement and diving of satellite-telemetered ringed seals (Pusa hispida) - an opportunistic predator - in Hudson Bay, Canada, to modelled prey data and environmental proxies. ResultsModelled prey biomass data performed better than their environmental proxies (e.g., sea surface temperature) for explaining seal movement, however movement was not related to foraging effort. Counter to theory, seals appeared to forage more in areas with relatively lower prey diversity and biomass, potentially due to reduced foraging efficiency in those areas. ConclusionsOur study highlights the need to validate movement analyses with prey data to effectively estimate the relationship between prey availability and foraging behaviour.

ecology↗

bioRxiv2022

Capsular polysaccharide inhibits vaccine-induced O-antigen antibody binding and function across both classical and hypervirulent K2:O1 strains of Klebsiella pneumoniae

Klebsiella pneumoniae presents as two circulating pathotypes: classical K. pneumoniae (cKp) and hypervirulent K. pneumoniae (hvKp). Classical isolates are considered urgent threats due to their antibiotic resistance profiles, while hvKp isolates have historically been antibiotic susceptible. Recently, however, increased rates of antibiotic resistance have been observed in both hvKp and cKp, further underscoring the need for preventive and effective immunotherapies. Two distinct surface polysaccharides have gained traction as vaccine candidates against K. pneumoniae: capsular polysaccharide and the O-antigen of lipopolysaccharide. While both targets have practical advantages and disadvantages, it remains unclear which of these antigens included in a vaccine would provide superior protection against matched K. pneumoniae strains. Here, we report the production of two bioconjugate vaccines, one targeting the K2 capsular serotype and the other targeting the O1 O-antigen. Using murine models, we investigated whether these vaccines induced specific antibody responses that recognize K2:O1 K. pneumoniae strains. While each vaccine was immunogenic in mice, both cKp and hvKp strains exhibited decreased O-antibody binding in the presence of capsule. Further, O1 antibodies demonstrated decreased killing in serum bactericidal assays with encapsulated strains, suggesting that the presence of K. pneumoniae capsule blocks O1-antibody binding and function. Finally, the K2 vaccine outperformed the O1 vaccine against both cKp and hvKp in two different murine infection models. These data suggest that capsule-based vaccines may be superior to O-antigen vaccines for targeting hvKp and some cKp strains, due to capsule blocking the O-antigen. Significance StatementCurrently there are no licensed vaccines targeting K. pneumoniae, but several are in development. Two prominent K. pneumoniae surface polysaccharides (capsule and O-antigen) represent attractive vaccine targets; however, the relative efficacy of these potential vaccines against K. pneumoniae strains has not been directly compared. To inform future vaccine development, we evaluate two bioconjugate vaccines (targeting either capsule or O-antigen) demonstrating that each are immunogenic in murine models. However, we find that K. pneumoniae capsule largely inhibits recognition by antibodies raised against O-antigen. Further, we demonstrate that a capsule-based vaccine outperforms an O-antigen vaccine against both cKp and hvKp in murine models of pneumonia and bacteremia, suggesting that capsule-based vaccines offer superior protection from some K. pneumoniae infections.

microbiology↗

bioRxiv2020

Evidence for oligodendrocyte progenitor cell heterogeneity in the adult mouse brain.

White matter loss has been described as a common occurrence in Alzheimers disease (AD) patients for multiple decades. However, it remains unclear why oligodendrocyte progenitor cells (OPCs) fail to repair myelin deficits in these patients. Here, we show that clusterin, a risk factor for late-onset AD, is produced by OPCs and inhibits their differentiation into oligodendrocytes. Specifically, we demonstrate that a unique subset of OPCs produces clusterin. We show that phagocytosis of debris, including amyloid beta (A{beta}) and myelin, drives the upregulation of clusterin in OPCs. We confirm, in vivo, that A{beta} oligomers drive clusterin upregulation and that OPCs phagocytose A{beta}. Furthermore, we show that clusterin is a potent inhibitor of OPC differentiation and prevents the production of myelin proteins. Finally, we demonstrate that clusterin inhibits OPC differentiation by significantly reducing the production of IL-9 by OPCs. Our data reveals that clusterin may be responsible for the lack of myelin repair observed in AD and is a promising therapeutic target for AD-associated cognitive decline.

neuroscience↗