Biology subjects

Leung, D. T.

Publications and source records attributed to Leung, D. T..

10 recordsLinked to original sources

bioRxiv2026

Longitudinal Changes in Nasal and Oral Microbiome and Antimicrobial Resistance Gene Profiles in Response to Human Fecal Microbiota Transplantation

The gut-lung axis describes interactions between intestinal and respiratory mucosal systems through microbial, metabolic, and immune pathways, but the systemic impact of gut-targeted therapies on upper respiratory tract (URT) communities remains underexplored. We conducted a longitudinal study in adult patients undergoing fecal microbiota transplantation (FMT) for recurrent Clostridioides difficile infection (CDI) alongside healthy controls. Fecal, nasal, and oral samples were collected at baseline (Day 0) and on Days 14 and 56 following FMT. Shotgun metagenomic sequencing was performed to quantify microbial diversity, taxonomic composition, and the abundance of antimicrobial resistance genes (ARGs). FMT was associated with increased gut diversity and decreased levels of key intestinal taxa commonly considered pathobionts, including Klebsiella spp., Escherichia spp., Shigella spp., and Klebsiella pneumoniae. At the phylum level, fecal Bacteroidota increased, while Mucoromycota decreased following treatment. Post-FMT nasal microbiome changes included reduced richness and diversity, expansion of Moraxella, and decreases in taxa linked with respiratory colonization, including Staphylococcus aureus and Streptococcus pneumoniae. By Day 56, nasal communities partially recovered toward healthy profiles. Baseline nasal ARG abundance decreased following FMT, particularly among {beta}-lactam, aminoglycoside, and fluoroquinolone resistance genes, and remained comparable to healthy controls by Day 56. In contrast, the oral microbiome and oral resistome remained largely stable, with only minor fluctuations, and no consistent increases in respiratory pathobiont-associated taxa. In summary, FMT was associated with broader effects beyond the gut, including changes in the URT microbial ecology and antimicrobial resistance profiles. Together, these findings are consistent evidence of gut-lung microbial interactions, linking intestinal dynamics with respiratory microbial composition and antimicrobial resistance patterns.

microbiology↗

bioRxiv2025

Insights into global antimicrobial resistance dynamics through the sequencing of enteric bacteria from U.S. international travelers

Antimicrobial resistance (AMR) is an urgent threat to public health, but gaps in surveillance limit the detection of emergent novel threats and knowledge about the global distribution of AMR genes. International travelers frequently acquire AMR organisms, and thus may provide a window into AMR dynamics in otherwise poorly monitored regions and environments. To assess the utility of travelers as global AMR sentinels, we collected pre- and post-travel stool samples from 608 travelers, which were screened for the presence of extended-spectrum beta-lactamase producing Enterobacterales, carbapenem-resistant Enterobacterales, and mcr-mediated colistin-resistant Enterobacterales. A total of 307 distinct AMR organisms were sequenced in order to determine genotypic patterns and their association with travel region and behavior. Travel-associated AMR organisms were overwhelmingly E. coli, which exhibited considerable phylogenetic diversity regardless of travel region. However, the prevalence of resistance genes varied by region, with blaCTX-M-55 and blaCTX-M-27 significantly more common in travelers returning from South America and South-Eastern Asia, respectively. Hybrid assembly and plasmid reconstruction revealed the genomic neighborhood of blaCTX-M-55 frequently matched a motif previously linked to animal populations. Contact with animals was also associated with virulence factors in acquired AMR organisms, including carriage of the ColV plasmid, a driver of avian pathogenic E. coli. We identified novel variants of the mcr-1 gene in strains acquired from Western Africa, highlighting the potential for traveler surveillance to detect emerging clinical threats. Ongoing efforts to track travel-acquired organisms could complement existing global AMR surveillance frameworks. ImportanceWe collected pre- and post-travel stool samples from 608 U.S. international travelers, which were screened for the presence of three clinically relevant antimicrobial-resistant organisms, with the goal of understanding the utility of travelers as sentinels for emerging AMR and identifying regional resistance patterns. We sequenced 307 organisms and uncovered significant diversity and geographic heterogeneity in AMR organisms. We found significant differences in certain resistance gene alleles of travelers returning from South America and South-Eastern Asia, traveler contact with animals associated with virulence factors, including a plasmid that is a known driver of avian pathogenic E. coli, and novel variants of the colistin resistance mcr-1 gene in strains acquired from Western Africa. This work emphasizes the value of monitoring international travelers as a proxy for understanding AMR patterns globally and could be an important addition to existing global AMR surveillance frameworks.

genomics↗

bioRxiv2024

MAIT Cells Modulate Innate Immune Cells and Inhibit Colon Cancer Growth

Mucosal-associated invariant T (MAIT) cells are innate-like T cells that can be activated by microbial antigens and cytokines and are abundant in mucosal tissues including the colon. MAIT cells have cytotoxic and pro-inflammatory functions and have potentials for use as adoptive cell therapy. However, studies into their anti-cancer activity, including their role in colon cancer, are limited. Using an animal model of colon cancer, we show that peritumoral injection of in vivo-expanded MAIT cells into RAG1-/- mice with MC38-derived tumors inhibits tumor growth compared to control. Multiplex cytokine analyses show that tumors from the MAIT cell-treated group have higher expression of markers for eosinophil-activating cytokines, suggesting an association between eosinophil recruitment and tumor inhibition. In a human peripheral leukocyte co-culture model, we show that leukocytes stimulated with MAIT ligand show an increase in eotaxin-1 production and activation of eosinophils, associated with increased cancer cell killing. In conclusion, we show that MAIT cells have a protective role in a murine colon cancer model, associated with modulation of the immune response to cancer, potentially involving eosinophil-associated mechanisms. Our results highlight the potential of MAIT cells for non-donor restricted colon cancer immunotherapy. Brief summaryIn models of colon cancer, MAIT cells have anti-tumor activity, associated with increased production of proinflammatory and eosinophil-modulating cytokines.

cancer biology↗

bioRxiv2022

Enhancing Mucosal-Associated Invariant T (MAIT) cell function and expansion with human selective serum

Mucosal-associated invariant T (MAIT) cells are promising innate-like lymphocytes with potential for use in anti-tumor immunotherapy. Existing MAIT cell expansion protocols are associated with potentially decremental phenotypic changes, including increased frequency of CD4+ MAIT cells and higher inhibitory receptor expression. In this study, we compared the effect on expansion of human MAIT cells of a serum replacement, Physiologix XF SR (Phx), with traditional serum fetal bovine serum (FBS) for supplementing RPMI-1640 media. Using flow cytometry, we found that Phx supported a significantly higher proliferative capacity for MAIT cells and resulted in a lower frequency of CD4+ MAIT cells, which have been associated with reduced Th1 effector and cytolytic functions. We saw that culturing MAIT cells in Phx led to better survival of MAIT cells and lower frequency of PD-1+ MAIT cells compared to FBS-supplemented media. Functionally, we saw that Phx supplementation was associated with a higher frequency of IFN-{gamma}+ MAIT cells after stimulation with E. coli compared to FBS-supplemented RPMI. In conclusion, we show that MAIT cells cultured in Phx have higher proliferative capacity, lower expression of inhibitory receptors, and have higher capacity to produce IFN-{gamma} after E. coli stimulation, compared to FBS-supplemented RPMI. This work shows that expanding MAIT cells with Phx compared to FBS-supplemented RPMI result in a more functionally desirable MAIT cell for future anti-tumor immunotherapy.

immunology↗

bioRxiv2022

Targeted multi-omic analysis of human skin tissue identifies alterations of conventional and unconventional T cells associated with burn injury

Burn injuries are a leading cause of unintentional injury, associated with a dysfunctional immune response and an increased risk of infections. Despite this, little is known about the role of T cells in human burn injury. In this study, we compared the activation and function of conventional T cells and unconventional T cell subsets in skin tissue from acute burn (within 7 days from initial injury) burn, late phase burn (beyond 7 days from initial injury), and non-burn patients. We compared T cell functionality by a combination of flow cytometry and a multi-omic single-cell approach with targeted transcriptomics and protein expression. We found a significantly lower proportion of CD8+ T cells in burn skin compared to non-burn skin, with CD4+ T cells making up the bulk of the T cell population. Both conventional and unconventional burn tissue T cells show significantly higher IFN-{gamma} and TNF- levels after stimulation than non-burn skin T cells. In sorted T cells, clustering showed that burn tissue had significantly higher expression of homing receptors CCR7, S1PR1, and SELL compared to non-burn skin. In unconventional T cells, including mucosal-associated invariant T (MAIT) and {gamma}{delta} T cells, we see significantly higher expression of cytotoxic molecules GZMB, PRF1, and GZMK. Multi-omics analysis of conventional T cells suggests a shift from tissue-resident T cells in non-burn tissue to a circulating T cell phenotype in burn tissue. In conclusion, by examining skin tissue from burn patients, our results suggest that T cells in burn tissue have a pro-inflammatory rather than a homeostatic tissue-resident phenotype, and that unconventional T cells have a higher cytotoxic capacity. Our findings have the potential to inform the development of novel treatment strategies for burns.

immunology↗

bioRxiv2022

Use of a MAIT activating ligand, 5-OP-RU, as a mucosal adjuvant in a murine model of Vibrio cholerae O1 vaccination.

BackgroundMucosal-associated invariant T (MAIT) cells are innate-like T cells enriched in the mucosa with capacity for B cell help. We hypothesize that targeting MAIT cells, using a MAIT activating ligand as an adjuvant, could improve mucosal vaccine responses to bacterial pathogens. MethodsWe utilized murine models of Vibrio cholerae vaccination to test the adjuvant potential of the MAIT activating ligand, 5-(2-oxopropylideneamino)-6-D-ribitylaminouracil (5-OP-RU). We measured V. cholerae-specific antibody and antibody-secreting cell responses, and used flow cytometry to examine MAIT cell and B cell phenotype, in blood, bronchoalveolar lavage fluid (BALF), and mucosal tissues, following intranasal vaccination with live V. cholerae O1 or a V. cholerae O1 polysaccharide conjugate vaccine. ResultsWe report significant expansion of MAIT cells in the lungs of 5-OP-RU treated mice, and increases in BALF V. cholerae O-specific-polysaccharide IgG responses in our conjugate vaccine model adjuvanted with low-dose 5-OP-RU. No significant differences in humoral responses were found in our live V. cholerae vaccination model. ConclusionsUsing a murine model, we demonstrate the potential, as well as the limitations, of targeting MAIT cells to improve antibody responses to a mucosal cholera vaccine. Our study highlights the need for future research optimizing MAIT cell targeting for improving mucosal vaccines. One Sentence SummaryTargeting mucosal-associated invariant T (MAIT) cells with a mucosal adjuvant in an intranasal cholera vaccine model resulted in significant expansion of lung MAIT cells, but limited improvements in cholera-specific antibody responses.

immunology↗

bioRxiv2020

Humans surviving cholera develop antibodies against Vibrio cholerae O-specific polysaccharide that inhibit pathogen motility

The mechanism of protection against cholera afforded by previous illness or vaccination is currently unknown. We have recently shown that antibodies targeting O-specific polysaccharide (OSP) of Vibrio cholerae correlate highly with protection against cholera. V. cholerae is highly motile and possesses a flagellum sheathed in O-specific polysaccharide (OSP), and motility of V. cholerae correlates with virulence. Using high speed video microscopy, and building upon previous animal-related work, we demonstrate that sera, polyclonal antibody fractions, and OSP-specific monoclonal antibodies recovered from humans surviving cholera block V. cholerae motility at both subagglutinating and agglutinating concentrations. This anti-motility effect is reversed by pre-adsorbing sera and polyclonal antibody fractions with purified OSP; and is associated with OSP-specific but not flagellin-specific monoclonal antibodies. F[ab] fragments of OSP-specific polyclonal antibodies do not inhibit motility, suggesting a requirement for antibody-mediated crosslinking in motility inhibition. We show that OSP-specific antibodies do not directly affect V. cholerae viability, but that OSP-specific monoclonal antibody highly protects against death in the murine cholera model. We used in vivo competitive index studies to demonstrate that OSP-specific antibodies impede colonization and survival of V. cholerae in intestinal tissues, and that this impact is motility-dependent. Our findings suggest that the impedance of motility by antibodies targeting V. cholerae OSP contributes to protection against cholera. IMPORTANCECholera is a severe dehydrating illness of humans caused by Vibrio cholerae. V. cholerae is a highly motile bacterium that has a single flagellum covered in lipopolysaccharide (LPS) displaying O-specific polysaccharide (OSP), and V. cholerae motility correlates with its ability to cause disease. The mechanisms of protection against cholera are not well understood; however, since V. cholerae is a non-invasive intestinal pathogen, it is likely that antibodies that bind the pathogen or its products in the intestinal lumen contribute to protection from infection. Here, we demonstrate that OSP-specific antibodies isolated from humans surviving cholera in Bangladesh inhibit V. cholerae motility and are associated with protection against challenge in a motility-dependent manner.

microbiology↗

bioRxiv2020

A novel subset of follicular helper-like MAIT cells has capacity for B cell help and antibody production in the mucosa.

Mucosal-associated invariant T (MAIT) cells are innate-like T lymphocytes that aid in protection against bacterial pathogens at mucosal surfaces via release of inflammatory cytokines and cytotoxic molecules. Recent evidence suggests MAIT cells are capable of providing B cell help. In this study, we describe a previously unreported population of CXCR5+ T follicular helper (Tfh)-like MAIT cells, MAITfh, that have the capacity to provide B cell help within mucosal lymphoid organs. MAITfh cells are preferentially located near germinal centers in human tonsils and express the classical Tfh-associated transcription factor, B-cell lymphoma 6 (BCL-6), co-stimulatory markers, inducible T cell costimulatory (ICOS) and programmed death receptor 1 (PD-1), and cytokines, interleukin (IL)-21. Furthermore, we demonstrate the ability of MAIT cells to provide B cell help in vivo following mucosal challenge with Vibrio cholerae. Specifically, we show that adoptive transfer of MAIT cells into {beta} T cell-deficient mice promoted B cell differentiation and increased serum V. cholerae-specific IgA responses. Our data demonstrate the capacity of MAIT cells to participate in adaptive immune responses, and suggest that MAIT cells may be potential targets for mucosal vaccines. One Sentence SummaryWe identified and characterized a novel subset of T follicular helper-like MAIT (MAITfh) cells that has the capacity to provide B cell help, and show the sufficiency of MAIT cells to promote production of pathogen-specific IgA antibodies and B cell differentiation in mucosal challenge.

immunology↗

bioRxiv2020

Intestinal infection results in impaired lung innate immunity to secondary respiratory infection.

BackgroundPneumonia and diarrhea are among the leading causes of death worldwide, and epidemiological studies have demonstrated that diarrhea is associated with an increased risk of subsequent pneumonia. Our aim was to determine the impact of intestinal infection on innate immune responses in the lung. MethodsUsing a mouse model of intestinal infection by Salmonella enterica serovar Typhimurium (S. Typhimurium (ST)), we investigated how infection in the gut compartment can modulate immunity in the lungs and impact susceptibility to bacterial (Klebsiella pneumoniae (KP)) challenge. ResultsWe found alterations in frequencies of innate immune cells in lungs of intestinally-infected mice compared to uninfected mice. On subsequent challenge with K. pneumoniae we found that mice with prior intestinal infection have higher lung bacterial burden and inflammation, increased neutrophil margination, and neutrophil extracellular traps (NETs), but lower overall numbers of neutrophils, compared to mice without prior intestinal infection. Total numbers of dendritic cells, innate-like T cells, and natural killer cells were not different between mice with and without prior intestinal infection. ConclusionsTogether, these results suggest that intestinal infection impacts lung innate immune responses, most notably neutrophil characteristics, potentially resulting in increased susceptibility to secondary pneumonia. Article summaryWe show, in a mouse model, that prior intestinal infection with Salmonella Typhimurium leads to increased susceptibility to respiratory Klebsiella pneumoniae infection, which is associated with altered neutrophil responses.

immunology↗

bioRxiv2020

Mucosal-associated invariant T (MAIT) cells mediate protective host responses in sepsis

Sepsis is a systemic inflammatory response to infection and a leading cause of death. Mucosal-associated invariant T (MAIT) cells are innate-like T cells enriched in mucosal tissues that recognize bacterial ligands. We investigated MAIT cells during clinical and experimental sepsis, and their contribution to host responses. In experimental sepsis, MAIT-deficient mice had significantly increased mortality and bacterial load, and reduced tissue-specific cytokine responses. MAIT cells of WT mice expressed lower levels of IFN-{gamma} and IL-17a during sepsis compared to sham surgery, changes not seen in non-MAIT T cells. MAIT cells of patients presenting with sepsis were significantly reduced in frequency, more activated, and had decreased IFN-{gamma} production when stimulated, compared to healthy donors and paired 90-day post-sepsis samples. Our data suggest that MAIT cells are highly activated and become dysfunctional during clinical sepsis, and contribute to tissue-specific cytokine responses that are protective against mortality during experimental sepsis.

physiology↗