Biology subjects

Bourgeois, J. S.

Publications and source records attributed to Bourgeois, J. S..

7 recordsLinked to original sources

bioRxiv2024

Differentiating Peromyscus leucopus bone marrow-derived macrophages for characterization of responses to Borrelia burgdorferi and lipopolysaccharide

Currently, most tools utilized in host-pathogen interaction studies depend on the use of human or mouse (Mus musculus) cells and tissues. While these species have led to countless breakthroughs in our understanding of infectious disease, there are undoubtably important biological processes that are missed by limiting studies to these two vertebrate species. For instance, it is well-established that a common North American deermouse, Peromyscus leucopus, has unique interactions with microbes, which likely shape its ability to serve as a critical reservoir for numerous zoonotic pathogens, including a Lyme disease spirochete, Borrelia burgdorferi. In this work, we expand the immunological toolkit to study P. leucopus biology by performing the first differentiation of deermouse bone marrow to macrophages using P. leucopus M-CSF producing HEK293T cells. We find that P. leucopus BMDMs generated through this method behave broadly very similarly to C57BL/6J macrophages generated with L-929 supernatant, though RNA sequencing revealed modest differences in transcriptomic responses to B. burgdorferi and lipopolysaccharide. In particular, differences in Il10 induction and caspase expression were observed between the species.

immunology↗

bioRxiv2024

Peromyscus leucopus, Mus musculus, and humans have distinct transcriptomic responses to larval Ixodes scapularis bites

Ixodes scapularis ticks are an important vector for at least six tick-borne human pathogens, including the predominant North American Lyme disease spirochete Borrelia burgdorferi. The ability for these ticks to survive in nature is credited, in part, to their ability to feed on a variety of hosts without excessive activation of the proinflammatory branch of the vertebrate immune system. While the ability for nymphal ticks to feed on a variety of hosts has been well-documented, the host-parasite interactions between larval I. scapularis and different vertebrate hosts is relatively unexplored. Here we report on the changes in the vertebrate transcriptome present at the larval tick bite site using the natural I. scapularis host Peromyscus leucopus deermouse, a non-natural rodent host Mus musculus (BALB/c), and humans. We note substantially less evidence of activation of canonical proinflammatory pathways in P. leucopus compared to BALB/c mice and pronounced evidence of inflammation in humans. Pathway enrichment analyses revealed a particularly strong signature of interferon gamma, tumor necrosis factor, and interleukin 1 signaling at the BALB/c and human tick bite site. We also note that bite sites on BALB/c mice and humans, but not deermice, show activation of wound-healing pathways. These data provide molecular evidence of the coevolution between larval I. scapularis and P. leucopus as well as expand our overall understanding of I. scapularis feeding. SignificanceIxodes scapularis tick bites expose humans to numerous diseases in North America. While larval tick feeding enables pathogens to enter the tick population and eventually spread to humans, how larval ticks interact with mammals has been understudied compared to other tick stages. Here we examined the transcriptomic response of a natural I. scapularis rodent host (Peromyscus leucopus), a non-native I. scapularis rodent host (Mus musculus), and an incidental host (humans). We find that there are differences in how all three species respond to larval I. scapularis, with the natural host producing the smallest transcriptomic signature of a canonical proinflammatory immune response and the incidental human host producing the most robust signature of inflammation in response to the larval tick. These data expand our understanding of the pressures on ticks in the wild and inform our ability to model these interactions in laboratory settings.

immunology↗

bioRxiv2022

A putative xanthine dehydrogenase protects Borrelia burgdorferi from reactive oxygen species and promotes virulence

Borrelia burgdorferi is a pathogenic bacterium and the causative agent of Lyme Disease. It is exposed to reactive oxygen species (ROS) in both the vertebrate and tick hosts. While some mechanisms by which B. burgdorferi ameliorates the effects of ROS exposure have been studied, there are likely many other unknown mechanisms of ROS neutralization that contribute to virulence. Here, we follow up on a three gene cluster of unknown function, BB_0554, BB_0555, and BB_0556, that our prior unbiased transposon insertional sequencing studies implicated in both ROS survival and survival in Ixodes scapularis. We confirmed these findings through genetic knockout and provide evidence that these genes are co-transcribed as an operon to produce a xanthine dehydrogenase. In agreement with these results, we found that B. burgdorferi exposure to either uric acid (a downstream product of xanthine dehydrogenase) or allopurinol (an inhibitor of xanthine dehydrogenase) could modulate sensitivity to ROS in a BB_0554-BB_0556 dependent manner. Together, this study identifies a previously uncharacterized three gene operon in B. burgdorferi as a putative xanthine dehydrogenase critical for virulence. ImportanceBorrelia burgdorferi, the causative agent of Lyme disease, is highly successful at evading host immune defenses such as reactive oxygen species, despite minimal identified defenses against oxidative stress. We identified a putative xanthine dehydrogenase that is important in survival of the organism when exposed to oxidative stress and in both its tick and murine hosts. The mechanism appears based on a previously unrecognized role of uric acid in neutralizing reactive oxygen species and highlights how B. burgdorferi can utilize its very limited metabolic capabilities in unique ways.

microbiology↗

bioRxiv2022

Human variation impacting MCOLN2 restricts Salmonella Typhi replication by magnesium deprivation

Human genetic diversity can reveal critical factors in host-pathogen interactions. This is especially useful for human-restricted pathogens like Salmonella enterica serovar Typhi (S. Typhi), the cause of Typhoid fever. One key dynamic during infection is competition for nutrients: host cells attempt to restrict intracellular replication by depriving bacteria of key nutrients or delivering toxic metabolites in a process called nutritional immunity. Here, a cellular genome-wide association study of intracellular replication by S. Typhi in nearly a thousand cell lines from around the world--and extensive follow-up using intracellular S. Typhi transcriptomics and manipulation of magnesium concentrations--demonstrates that the divalent cation channel mucolipin-2 (MCOLN2) restricts S. Typhi intracellular replication through magnesium deprivation. Our results reveal natural diversity in Mg2+ limitation as a key component of nutritional immunity against S. Typhi. One-Sentence SummaryHuman immune cells genetically vary in their ability to use magnesium deprivation to restrict growth of the typhoid fever bacterium.

genetics↗

bioRxiv2022

Single-cell genome-wide association reveals a nonsynonymous variant in ERAP1 confers increased susceptibility to influenza virus

Diversity in the human genome is one factor that confers resistance and susceptibility to infectious diseases. This is observed most dramatically during pandemics, where individuals exhibit large differences in risk and clinical outcomes against a pathogen infecting large portions of the worlds populations. Here, we developed scHi-HOST (single cell High-throughput Human in vitrO Susceptibility Testing), a method for rapidly identifying genetic variants that confer resistance and susceptibility to pathogens. scHi-HOST leverages scRNA-seq (single-cell RNA-sequencing) to simultaneously assign genetic identity to individual cells in mixed infections of cell lines of European, African, and Asian origin, reveal associated genetic variants for viral entry and replication, and identify expression quantitative trait loci (eQTLs). Applying scHi-HOST to influenza A virus (IAV), we identified eQTLs at baseline and in genes that are induced by IAV infection. Integration of scHi-HOST with a human IAV challenge study (Prometheus) revealed that a missense variant in ERAP1 (Endoplasmic reticulum aminopeptidase 1; rs27895) was associated with IAV burden in cells and human volunteers. Functional studies using RNA interference, ERAP1 inhibitor, and overexpression of alternative alleles demonstrated that ERAP1 is exploited by IAV to promote infection. Specifically, the nonsynonymous substitution, which results in a glycine to aspartate substitution at ERAP1 residue 348, would disrupt the substrate binding pocket of ERAP1, likely resulting in a significantly altered preference for substrates, poorer catalytic efficiency, or both. Finally, rs27895 exhibits substantial population differentiation, with the higher frequency of the minor T allele in two African populations likely contributing to the greater permissivity of cells from these populations to IAV infection. scHi-HOST is an important resource for understanding susceptibility to influenza and is a broadly applicable method for decoding human genetics of infectious disease.

genetics↗

bioRxiv2020

ARHGEF26 enhances Salmonella invasion and inflammation in cells and mice

Salmonella hijack host machinery in order to invade cells and establish infection. While considerable work has described the role of host proteins in invasion, much less is known regarding how natural variation in these invasion-associated host proteins affects Salmonella pathogenesis. Here we leveraged a candidate cellular GWAS screen to identify natural genetic variation in the ARHGEF26 (Rho Guanine Nucleotide Exchange Factor 26) gene that renders lymphoblastoid cells susceptible to Salmonella Typhi and Typhimurium invasion. Experimental follow-up redefined ARHGEF26s role in Salmonella epithelial cell invasion, identified serovar specific interactions, implicated ARHGEF26 in SopE-mediated invasion, and revealed that the ARHGEF26-associated proteins DLG1 and SCRIB facilitate S. Typhi uptake. Importantly, we show that ARHGEF26 plays a critical role in S. Typhimurium pathogenesis by contributing to bacterial burden in the enteric fever murine model, as well as inflammation in the gastroenteritis infection model. The impact of ARHGEF26 on inflammation was also seen in cells, as knockdown reduced IL-8 production in HeLa cells. Together, these data reveal pleiotropic roles for ARHGEF26 function during infection and highlight that many of the interactions that occur during infection that are thought to be well understood likely have underappreciated complexity. Author SummaryDuring infection, Salmonella manipulates host cells into engulfing the bacteria and establishing an intracellular niche. While many studies have identified genes involved in different stages of this Salmonella invasion process, few studies have examined how differences between human hosts contribute to infection susceptibility. Here we leveraged a candidate genetic screen to identify natural genetic variation in the human ARHGEF26 gene that correlates with Salmonella invasion. Springboarding from this result, we experimentally tested and revised existing models of ARHGEF26s role in Salmonella invasion, discovered an additional new role for ARHGEF26 during Salmonella disease, and confirmed our findings in mouse models. Building on how ARHGEF26 functions in other contexts, we implicated two ARHGEF26-interacting host proteins as contributors to Salmonella pathobiology. Collectively, these results identify a potential source of inter-person diversity in susceptibility to Salmonella disease, expand our molecular understanding of Salmonella infection to include a multifaceted role for ARHGEF26, and identify several important future directions that will be important to understand how Salmonella recruit and manipulate ARHGEF26 as well as how ARHGEF26 is able to drive Salmonella-beneficial processes.

microbiology↗

bioRxiv2018

Methylthioadenosine reduces host inflammatory response by suppressing Salmonella virulence

In order to deploy virulence factors at appropriate times and locations, microbes must rapidly sense and respond to various metabolite signals. Previously we showed transient elevation of the methionine-derived metabolite methylthioadenosine (MTA) in serum during systemic Salmonella enterica serovar Typhimurium (S. Typhimurium) infection. Here we explored the functional consequences of increased MTA concentrations on S. Typhimurium virulence. We found that MTA--but not other related metabolites involved in polyamine synthesis and methionine salvage--reduced motility, host cell pyroptosis, and cellular invasion. Further, we developed a genetic model of increased bacterial endogenous MTA production by knocking out the master repressor of the methionine regulon, metJ. Like MTA treated S. Typhimurium, the {Delta}metJ mutant displayed reduced motility, host cell pyroptosis, and invasion. These phenotypic effects of MTA correlated with suppression of flagellar and Salmonella pathogenicity island-1 (SPI-1) networks. {Delta}metJ S. Typhimurium had reduced virulence in oral infection of C57BL/6 mice. Finally, {Delta}metJ bacteria induced a less severe inflammatory cytokine response in a mouse sepsis model. These data provide a possible bacterial mechanism for our previous findings that pretreating mice with MTA dampens inflammation and prolongs survival. Together, these data indicate that exposure of S. Typhimurium to MTA or disruption of the bacterial methionine metabolism pathway is sufficient to suppress SPI-1 mediated processes, motility, and in vivo virulence.\n\nSignificanceSalmonella enterica serovar Typhimurium (S. Typhimurium) is a leading cause of gastroenteritis and bacteremia worldwide. Widespread multi-drug resistance, inadequate diagnostics, and the absence of a vaccine for use in humans, all contribute to the global burden of morbidity and mortality associated with S. Typhimurium infection. Here we find that increasing the concentration of the methionine derived metabolite methylthioadenosine, either in S. Typhimurium or in its environment, is sufficient to suppress virulence processes. These findings could be leveraged to inform future therapeutic interventions against S. Typhimurium aimed at manipulating either host or pathogen methylthioadenosine production.

microbiology↗