Biology subjects

Abuaita, B. H.

Publications and source records attributed to Abuaita, B. H..

11 recordsLinked to original sources

bioRxiv2025

Exposure to immune stimuli reprograms alveolar macrophages to acquire neutrophil-derived antimicrobial molecules to prevent staphylococcal pneumonia

The protective adaptation of innate immune defenses against respiratory pathogens has been linked to previous exposure to immune stimuli; however, the underlying mechanisms of these adaptations are not yet fully understood. Here, we show that pre-exposure to a low dose of non-specific immune stimuli or infection protects against subsequent lethal methicillin-resistant Staphylococcus aureus (MRSA) challenge. This enhanced protection concurs with increased alveolar macrophages (AMs) resulting from a self-renewal process in the lungs. Importantly, these AMs are programmed to acquire neutrophil-released antimicrobial enzymes from the extracellular space to kill MRSA, prevent tissue damage, and rapidly restore lung homeostasis. The gain of AM functions is dependent on differential gene expression, including expression of the efferocytosis receptor MerTK and the anti-apoptotic regulator Bcl-xL. Thus, our data highlight that the acquisition of neutrophil enzymes by AMs is an integral component of innate immune adaptation.

immunology↗

bioRxiv2025

DRP1/DMNL-1-mediated mitochondrial fission augments Rickettsia parkeri replication in macrophages

Pathogenic Spotted Fever Group (SFG) Rickettsia species, including Rickettsia parkeri replicate in endothelial cells, monocytes, and macrophages in vitro and during infections in murine models of disease. We demonstrated that R. parkeri survives and proliferates within phagocytes and avoids intracellular killing within lysosomal compartments. We found that infection of human macrophage-like cells with a related SFG Rickettsia, R. conorii, resulted in a significant increase in mitochondria-associated proteins, suggesting that mitochondrial functions are involved in Rickettsia pathogenesis. Several intracellular bacterial pathogens manipulate host cell mitochondrial networks and stimulate mitochondrial fission mediated by a GTP-binding regulatory protein, DRP1/DMNL1, to promote intracellular replication. Here, we investigated the contribution of DRP1 in the growth of R. parkeri in macrophages. Murine immortalized bone marrow derived macrophages (iBMDMs) and primary human monocyte derived macrophages were infected with R. parkeri and mitochondrial dynamics (fission and network) were assessed by immunofluorescence microscopy. R. parkeri proliferated in macrophages, which coincided with a significant increase in mitochondria content and fission compared to uninfected cells. R. parkeri infection led to increases in host cell ATP production primarily due to mitochondrial respiration and bacteria were often found co-localized with mitochondrial fragments. Importantly, R. parkeri growth was significantly impacted in DRP1 deficient macrophages. These results suggest that the modulation of mitochondria content and dynamics are essential for replication and survival of pathogenic SFG Rickettsia species in macrophages and suggest that the metabolic requirements for obligate intracellular pathogens may differ from other pathogenic Gram-negative intracellular bacteria.

microbiology↗

bioRxiv2024

Activation of the endoplasmic reticulum stress regulator IRE1α compromises pulmonary host defenses

The endoplasmic reticulum (ER) stress sensor inositol-requiring enzyme 1- (IRE1) is associated with lung infections where innate immune cells are drivers for progression and resolution of inflammation. Yet, the role of IRE1 in pulmonary innate immune host defense during acute respiratory infection remains unexplored. Here, we found that activation of IRE1 in infected lungs compromises immunity against methicillin-resistant Staphylococcus aureus (MRSA)-induced primary and secondary pneumonia. Moreover, activation of IRE1 in MRSA-infected lungs and alveolar macrophages (AMs) leads to exacerbated production of inflammatory mediators followed by cell death. Ablation of myeloid IRE1 or global IRE1 inhibition confers protection against MRSA-induced pneumonia with improves survival, bacterial clearance, cytokine reduction, and lung injury. In addition, loss of myeloid IRE1 protects mice against MRSA-induced secondary to influenza pneumonia by promoting AM survival. Thus, activation of IRE1 is detrimental to pneumonia and therefore, it shows potential as a target to control excessive unresolved lung inflammation.

immunology↗

bioRxiv2022

The IRE1α-XBP1 signaling axis promotes glycolytic reprogramming in response to inflammatory stimuli

Immune cells must be able to adjust their metabolic programs to effectively carry out their effector functions. Here, we show that the ER stress sensor IRE1 and its downstream transcription factor XBP1 enhance the upregulation of glycolysis in classically activated macrophages (CAM). The IRE1-XBP1 signaling axis supports this glycolytic switch in macrophages when activated by LPS stimulation or infection with the intracellular bacterial pathogen Brucella abortus. Importantly, these different inflammatory stimuli have distinct mechanisms of IRE1 activation; while TLR4 supports glycolysis under both conditions, TLR4 is required for activation of IRE1 in response to LPS treatment but not B. abortus infection. Though IRE1 and XBP1 are necessary for maximal induction of glycolysis in CAM, activation of this pathway is not sufficient to increase the glycolytic rate of macrophages, indicating that the cellular context in which this pathway is activated ultimately dictates the cells metabolic response and that IRE1 activation may be a way to fine-tune metabolic reprogramming. IMPORTANCEThe immune system must be able to tailor its response to different types of pathogens in order to eliminate them and protect the host. When confronted with bacterial pathogens, macrophages, frontline defenders in the immune system, switch to a glycolysis-driven metabolism to carry out their antibacterial functions. Here, we show that IRE1, a sensor of ER stress, and its downstream transcription factor XBP1 support glycolysis in macrophages during infection with Brucella abortus or challenge with Salmonella LPS. Interestingly, these stimuli activate IRE1 by independent mechanisms. While the IRE1-XBP1 signaling axis promotes the glycolytic switch, activation of this pathway is not sufficient to increase glycolysis in macrophages. This study furthers our understanding of the pathways that drive macrophage immunometabolism and highlights a new role for IRE1 and XBP1 in innate immunity.

immunology↗

bioRxiv2022

Neutrophils prime unique transcriptional responses in intestinal organoids during infection with nontyphoidal Salmonella enterica serovars

Nontyphoidal strains of Salmonella enterica are a major cause of foodborne illnesses and infection with these bacteria result in inflammatory gastroenteritis. Neutrophils are a dominant immune cell type found at the site of infection in Salmonella-infected individuals, but how they regulate infection outcome is not well understood. Here we used a co-culture model of primary human neutrophils and human intestinal organoids to probe the role of neutrophils during infection with two of the most prevalent Salmonella serovars: Salmonella enterica serovar Enteritidis and Typhimurium. Using a transcriptomics approach, we identified a dominant role for neutrophils in mounting differential immune responses including production of pro-inflammatory cytokines, chemokines, and antimicrobial peptides. We also identified specific gene sets that are induced by neutrophils in response to Enteritidis or Typhimurium infection. By comparing host responses to these serovars, we uncovered differential regulation of host metabolic pathways particularly induction of cholesterol biosynthetic pathways during Typhimurium infection and suppression of RNA metabolism during Enteritidis infection. Together these findings provide insight into the role of human neutrophils in modulating different host responses to pathogens that cause similar disease in humans. ImportanceNontyphoidal serovars of Salmonella enterica are known to induce robust neutrophil recruitment in the gut during early stages of infection, but the specific role of neutrophils in regulating infection outcome of different serovars is poorly understood. Due to differences in human infection progression compared to small animal models, characterizing the role of neutrophils during infection has been challenging. Here we used a co-culture model of human intestinal organoids with human primary neutrophils to study the role of neutrophils during infection of human intestinal epithelium. Using a transcriptomics approach, we define neutrophil-dependent reprogramming of the host response to Salmonella, establishing a clear role in amplifying pro-inflammatory gene expression. Additionally, the host response driven by neutrophils differed between two similar nontyphoidal Salmonella serovars. These findings highlight the importance of building more physiological infection models to replicate human infection conditions to study host responses specific to individual pathogens.

immunology↗

bioRxiv2022

Cardiolipin coordinates inflammatory metabolic reprogramming through regulation of Complex II assembly and stability

Macrophage metabolic plasticity enables repurposing of electron transport from energy generation to inflammation and host defense. Altered Respiratory Complex II function has been implicated in cancer, diabetes and inflammation but regulatory mechanisms are incompletely understood. Here we show that macrophage inflammatory activation triggers Complex II disassembly and succinate dehydrogenase-B subunit loss through sequestration and mitophagy. Mitochondrial fission was required for lipopolysaccharide-stimulated succinate dehydrogenase-B degradation but not sequestration. We hypothesized that this Complex II regulatory mechanism might be coordinated by the mitochondrial phospholipid cardiolipin. Cardiolipin synthase knockdown prevented lipopolysaccharide-induced metabolic remodeling and Complex II disassembly, sequestration and degradation. Cardiolipin-depleted macrophages were defective in lipopolysaccharide-induced pro-inflammatory cytokine production, a phenotype partially rescued by Complex II inhibition. Thus, cardiolipin acts as a critical organizer of inflammatory metabolic remodeling.

immunology↗

bioRxiv2021

Human norovirus infection of primary B cells triggers immune activation in vitro

Human norovirus (HNoV) is a global health and socio-economic burden, estimated to infect every individual at least five times during their lifetime. The underlying mechanism for the potential lack of long-term immune protection from HNoV infections is not understood and prompted us to investigate HNoV susceptibility of primary human B cells and its functional impact. Primary B cells isolated from whole-blood were infected with HNoV-positive stool samples and harvested 3 days post infection (dpi) to assess viral RNA yield by RT-qPCR. A 3-18 fold increase in HNoV RNA yield was observed in 50-60% donors. Infection was further confirmed in B cells derived from splenic and lymph node biopsies. Next, we characterized infection of whole-blood derived B cells by flow cytometry in specific functional B cell subsets (naive CD27-IgD+, memory switched CD27+IgD-, memory unswitched CD27+IgD+ and double-negative CD27-IgD-). While susceptibility of subsets was similar, we observed changes in B cell subsets distribution upon infection that were recapitulated after treatment with HNoV virus-like particles and mRNA encoding for HNoV NS1-2 protein. Importantly, treatment of immortalized BJAB B cell lines with the predicted recombinant NS1 protein triggered cell proliferation, increased ATP production, and induced metabolic changes, as detected by means of CFSE/Ki67 staining, seahorse analysis and metabolomics, respectively. These data demonstrate the susceptibility of primary B cells to HNoV infection and suggest that the secreted NS1 protein affects B cell function, proliferation and metabolism in vitro, which could have implications for viral pathogenesis and immune response in vivo. ImportanceHuman norovirus (HNoV) is the most prevalent causative agent of gastroenteritis worldwide. Infection results in a self-limiting disease that can become chronic and severe in the immunocompromised, elderly and infants. There are currently no approved therapeutic and preventative strategies to limit the health and socio-economic burden associated with HNoV infections. Moreover, HNoV does not elicit life-long immunity as repeat infections are common, presenting a challenge for vaccine development. Given the importance of B cells for humoral immunity, we investigated susceptibility and impact of HNoV infection on human B cells. We found that HNoV replicates in human primary B cells derived from blood, spleen and lymph nodes specimens and induces functional changes in B cells, mediated in part by the non-structural protein NS1. Because of the secreted nature of NS1, we put forward the hypothesis that HNoV infection can modulate bystander B cell function with potential implications in systemic immune response.

microbiology↗

bioRxiv2020

Comparative transcriptional profiling of the early host response to infection by typhoidal and non-typhoidal Salmonella serovars in human intestinal organoids

Salmonella enterica represents over 2500 serovars associated with a wide-ranging spectrum of disease; from self-limiting gastroenteritis to invasive infection caused by non-typhoidal serovars (NTS) and typhoidal serovars, respectively. Host factors strongly influence infection outcome as malnourished or immunocompromised individuals can develop invasive infections from NTS, however, comparative host responses to individual serovars have been difficult to perform due to reliance on poorly representative model systems. Here we used human intestinal organoids (HIOs), a three-dimensional "gut-like" in vitro system derived from human embryonic stem cells, to elucidate similarities and differences in host responses to NTS and typhoidal serovars. HIOs discriminated between the two most prevalent NTS, Salmonella enterica serovar Typhimurium (STM) and Salmonella enterica serovar Enteritidis (SE), and typhoidal serovar Salmonella enterica serovar Typhi (ST) in epithelial cell invasion, replication and transcriptional responses. Pro-inflammatory signaling and cytokine output was reduced in ST-infected HIOs compared to NTS infections, reflecting early stages of NTS and typhoidal diseases. While we predicted that ST would induce a distinct transcriptional profile from the NTS strains, more nuanced expression profiles emerged. Notably, pathways involved in cell cycle, metabolism and mitochondrial functions were downregulated in STM-infected HIOs and upregulated in SE-infected HIOs. These results correlated with elevated levels of reactive oxygen species production in SE-infected HIOs compared to mock-infected HIOs. Collectively, these results suggest that the HIO model is well suited to reveal host transcriptional programming specific to individual Salmonella serovars, and that individual NTS may provoke unique host epithelial responses during intestinal stages of infection. Author SummarySalmonella enterica is the major causative agent of bacterial infections associated with contaminated food and water. Salmonella enterica consists of over 2500 serovars of which Typhimurium (STM), Enteritidis (SE) and Typhi (ST) are the three major serovars with medical relevance to humans. These serovars elicit distinctive immune responses and cause different diseases in humans, including self-limiting diarrhea, gastroenteritis and typhoid fever. Differences in the human host response to these serovars are likely to be a major contributing factor to distinct disease outcomes but are not well characterized, possibly due to the limitations of human-derived physiological infection models. Unlike immortalized epithelial cell culture models, human intestinal organoids (HIOs) are three-dimensional structures derived from embryonic stem cells that differentiate into intestinal mesenchymal and epithelial cells, mirroring key organizational aspects of the intestine. In this study, we used HIOs to monitor transcriptional changes during early stages of STM, SE and ST infection. Our comparative analysis showed that HIO inflammatory responses are the dominant response in all infections, but ST infection induces the weakest upregulation of inflammatory mediators relative to the other serovars. In addition, we identified several cellular processes, including cell cycle and mitochondrial functions, that were inversely regulated between STM and SE infection despite these serovars causing similar localized intestinal infection in humans. Our findings reinforce HIOs as an emerging model system to study Salmonella serovar infection, and provide global host transcriptional response profiles as a foundation for understanding human infection outcomes.

microbiology↗

bioRxiv2020

Salmonella enterica serovar Typhimurium SPI-1 and SPI-2 shape the transcriptional landscape of epithelial cells in a human intestinal organoid model system

The intestinal epithelium is a primary interface for engagement of the host response by foodborne pathogens, like Salmonella enterica serovar Typhimurium (STm). While interaction of STm with the mammalian host has been well studied in vitro in transformed epithelial cell lines or in the complex intestinal environment in vivo, few tractable models recapitulate key features of the intestinal epithelium. Human intestinal organoids (HIOs) contain a polarized epithelium with functionally differentiated cell subtypes, including enterocytes and goblet cells. HIOs contain luminal space that supports bacterial replication and are more amenable to experimental manipulation than animals while more reflective of physiological epithelial responses. Here we use the HIO model to define transcriptional responses of the host epithelium to STm infection, also determining host pathways dependent on Salmonella Pathogenicity Island-1 (SPI-1) and -2 (SPI-2) encoded Type 3 secretion systems (T3SS). Consistent with prior findings, we find that STm strongly stimulates pro-inflammatory gene expression. Infection-induced cytokine gene expression was rapid, transient and largely independent of SPI-1 T3SS-mediated invasion, likely due to continued luminal stimulation. Notably, STm infection led to significant down-regulation of host genes associated with cell cycle and DNA repair, an effect that required SPI-1 and SPI-2 T3SS. The transcriptional profile of cell cycle-associated target genes implicates multiple miRNAs as likely mediators of STm-dependent cell cycle suppression. These findings from Salmonella-infected HIOs delineate common and distinct contributions of SPI-1 and SPI-2 T3SSs in inducing early host responses during enteric infection and reveal host cell cycle as a potential target during STm intracellular infection. ImportanceSalmonella enterica serovar Typhimurium (STm) causes a significant health burden worldwide, yet host responses to initial stages of intestinal infection remain poorly understood. Due to differences in infection outcome between mice and humans, evaluating physiological host responses driven by major virulence determinants of Salmonella have been difficult to date. Here we use the 3D human intestinal organoid model to define early responses to infection with wildtype STm and mutants defective in the SPI-1 or SPI-2 Type 3 secretion systems. Both secretion system mutants show defects in a mouse model of oral Salmonella infection but the specific contributions of each secretion system are less well understood. We show that STm upregulates pro-inflammatory pathways independently of either secretion system while downregulation of host cell cycle pathways is dependent on both SPI-1 and SPI-2. These findings lay the groundwork for future studies investigating how SPI-1- and SPI-2-driven host responses affect infection outcome and show the potential of this model to study host-pathogen interactions with other serovars to understand how initial interactions with the intestinal epithelium may affect pathogenesis.

microbiology↗

bioRxiv2020

The branched chain aminotransferase IlvE promotes growth, stress resistance, and pathogenesis of Listeria monocytogenes

The bacterial plasma membrane is a key interface during pathogen-host interactions, and membrane composition enhances resistance against host antimicrobial defenses. Branched chain fatty acids (BCFAs) are the major plasma membrane component in the intracellular Gram-positive pathogen Listeria monocytogenes (Lm) and BCFA metabolism is essential for Lm growth and virulence. BCFA synthesis requires branched chain amino acids (BCAAs), and the BCAA Isoleucine (Ile) is a necessary substrate for the predominant membrane anteiso-BCFAs (ai-BCFAs) as well as an environmental signal for virulence regulation in Lm. In this study, we explored how two proteins that metabolize or sense Ile contribute to Lm growth, BCFA metabolism, and virulence. The IlvE aminotransferase incorporates Ile into ai-BCFAs, while CodY is an Ile-sensing regulator that coordinates BCAA synthesis and virulence gene expression. Analysis of deletion mutants lacking IlvE ({Delta}ilvE) or CodY ({Delta}codY) revealed a major role for IlvE under nutrient restriction and stress conditions. Cultures of the {Delta}ilvE mutant contained proportionally less ai-BCFAs relative to wild type, while of the {Delta}codY mutant had a lower proportion of ai-BCFAs in stationary phase, despite containing more cell-associated Ile. Both {Delta}ilvE and {Delta}codY mutants required exogenous Ile for optimal growth, but the {Delta}ilvE mutant had an absolute requirement for Valine and Leucine when Ile was absent. IlvE was also necessary for resistance to membrane stress, cell-to-cell spread, infection of primary macrophages, and virulence in mice. Our findings implicate IlvE as an integral aspect of Lm stress resistance and emphasize the central importance of Ile in Lm growth and virulence.

microbiology↗

bioRxiv2019

The IRE1α stress signaling axis is a key regulator of neutrophil antimicrobial effector function

Activation of the endoplasmic reticulum stress sensor, IRE1, is required for effective immune responses against bacterial infection and is associated with human inflammatory diseases where neutrophils are a key immune component. However, the specific role of IRE1 in regulating neutrophil effector function has not been studied. Here we show that infection-induced IRE1 activation licenses neutrophil antimicrobial capacity, including IL-1{beta} production, NET formation, and MRSA killing. Inhibition of IRE1 diminished production of mitochondrial reactive oxygen species (mROS) and decreased CASPASE-2 activation, which both contributed to neutrophil antimicrobial activity. Mice deficient in Caspase-2 were highly susceptible to MRSA infection and failed to form NETs in a subcutaneous abscess. IRE1 activation enhanced calcium influx and citrullination of histone H3 (Cit-H3) independently of mROS production, suggesting that IRE1 coordinates multiple pathways required for NET formation. Our data demonstrate that the IRE1-Caspase-2 axis is a major driver of neutrophil activity against MRSA infection and highlight the importance of IRE1 in neutrophil antibacterial function.\n\nOne Sentence SummaryIRE1 controls neutrophil antimicrobial defenses

immunology↗