Department of Microbiology and Immunology

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4-Ethylguaiacol Modulates Neuroinflammation and Promotes Heme Oxygenase-1 Expression to Ameliorate Brain Injury in Ischemic Stroke
(Frontiers, 2022-07) Weng, Wen-Tsan; Kuo, Ping-Chang; Scofield, Barbara A.; Paraiso, Hallel C.; Brown, Dennis A.; Yu, I-Chen; Yen, Jui-Hung; Microbiology and Immunology, School of Medicine
Ischemic stroke is caused by a sudden reduction in cerebral blood flow that subsequently induces a complex cascade of pathophysiological responses, leading to brain inflammation and irreversible infarction. 4-ethylguaiacol (4-EG) is reported to suppress inflammatory immune responses. However, whether 4-EG exerts anti-inflammatory effects in ischemic stroke remains unexplored. We evaluated the therapeutic potential of 4-EG and examined the cellular and molecular mechanisms underlying the protective effects of 4-EG in ischemic stroke. The effect of 4-EG in ischemic stroke was determined by using a transient middle cerebral artery occlusion (MCAO) animal model followed by exploring the infarct size, neurological deficits, microglia activation, inflammatory cytokine production, blood–brain barrier (BBB) disruption, brain endothelial cell adhesion molecule expression, and microglial heme oxygenase-1 (HO-1) expression. Nrf2-/- and HO-1 inhibitor ZnPP-treated mice were also subjected to MCAO to evaluate the role of the Nrf2/HO-1 pathway in 4-EG-mediated protection in ischemic stroke. We found that 4-EG attenuated infarct size and neurological deficits, and lessened BBB disruption in ischemic stroke. Further investigation revealed that 4-EG suppressed microglial activation, peripheral inflammatory immune cell infiltration, and brain endothelial cell adhesion molecule upregulation in the ischemic brain. Finally, we identified that the protective effect of 4-EG in ischemic stroke was abolished in Nrf2-/– and ZnPP-treated MCAO mice. Our results identified that 4-EG confers protection against ischemic stroke and reveal that the protective effect of 4-EG in ischemic stroke is mediated through the induction of the Nrf2/HO1 pathway. Thus, our findings suggest that 4-EG could be developed as a novel therapeutic agent for the treatment of ischemic stroke.
4-Ethylguaiacol Modulates Neuroinflammation and Promotes Heme Oxygenase-1 Expression to Ameliorate Brain Injury in Ischemic Stroke
(Frontiers Media, 2022-07-01) Weng, Wen-Tsan; Kuo, Ping-Chang; Scofield, Barbara A.; Paraiso, Hallel C.; Brown, Dennis A.; Yu, I-Chen; Yen, Jui-Hung; Microbiology and Immunology, School of Medicine
Ischemic stroke is caused by a sudden reduction in cerebral blood flow that subsequently induces a complex cascade of pathophysiological responses, leading to brain inflammation and irreversible infarction. 4-ethylguaiacol (4-EG) is reported to suppress inflammatory immune responses. However, whether 4-EG exerts anti-inflammatory effects in ischemic stroke remains unexplored. We evaluated the therapeutic potential of 4-EG and examined the cellular and molecular mechanisms underlying the protective effects of 4-EG in ischemic stroke. The effect of 4-EG in ischemic stroke was determined by using a transient middle cerebral artery occlusion (MCAO) animal model followed by exploring the infarct size, neurological deficits, microglia activation, inflammatory cytokine production, blood-brain barrier (BBB) disruption, brain endothelial cell adhesion molecule expression, and microglial heme oxygenase-1 (HO-1) expression. Nrf2-/- and HO-1 inhibitor ZnPP-treated mice were also subjected to MCAO to evaluate the role of the Nrf2/HO-1 pathway in 4-EG-mediated protection in ischemic stroke. We found that 4-EG attenuated infarct size and neurological deficits, and lessened BBB disruption in ischemic stroke. Further investigation revealed that 4-EG suppressed microglial activation, peripheral inflammatory immune cell infiltration, and brain endothelial cell adhesion molecule upregulation in the ischemic brain. Finally, we identified that the protective effect of 4-EG in ischemic stroke was abolished in Nrf2-/- and ZnPP-treated MCAO mice. Our results identified that 4-EG confers protection against ischemic stroke and reveal that the protective effect of 4-EG in ischemic stroke is mediated through the induction of the Nrf2/HO1 pathway. Thus, our findings suggest that 4-EG could be developed as a novel therapeutic agent for the treatment of ischemic stroke.
A Member of an Ancient Family of Bacterial Amino Acids Transporters Contributes to Chlamydia Nutritional Virulence and Immune Evasion
(American Society for Microbiology, 2023) Banerjee, Arkaprabha; Sun, Yuan; Muramatsu, Matthew K.; Toh, Evelyn; Nelson, David E.; Microbiology and Immunology, School of Medicine
Many obligate intracellular bacteria, including members of the genus Chlamydia, cannot synthesize a variety of amino acids de novo and acquire these from host cells via largely unknown mechanisms. Previously, we determined that a missense mutation in ctl0225, a conserved Chlamydia open reading frame of unknown function, mediated sensitivity to interferon gamma. Here, we show evidence that CTL0225 is a member of the SnatA family of neutral amino acid transporters that contributes to the import of several amino acids into Chlamydia cells. Further, we show that CTL0225 orthologs from two other distantly related obligate intracellular pathogens (Coxiella burnetii and Buchnera aphidicola) are sufficient to import valine into Escherichia coli. We also show that chlamydia infection and interferon exposure have opposing effects on amino acid metabolism, potentially explaining the relationship between CTL0225 and interferon sensitivity. Overall, we show that phylogenetically diverse intracellular pathogens use an ancient family of amino acid transporters to acquire host amino acids and provide another example of how nutritional virulence and immune evasion can be linked in obligate intracellular pathogens.
A novel Gardnerella, Prevotella, and Lactobacillus standard that improves accuracy in quantifying bacterial burden in vaginal microbial communities
(Frontiers Media, 2023-06-19) Elnaggar, Jacob H.; Ardizzone, Caleb M.; Cerca, Nuno; Toh, Evelyn; Łaniewski, Paweł; Lillis, Rebecca A.; Herbst-Kralovetz, Melissa M.; Quayle, Alison J.; Muzny, Christina A.; Taylor, Christopher M.; Microbiology and Immunology, School of Medicine
Bacterial vaginosis (BV) is the most common vaginal dysbiosis. In this condition, a polymicrobial biofilm develops on vaginal epithelial cells. Accurately quantifying the bacterial burden of the BV biofilm is necessary to further our understanding of BV pathogenesis. Historically, the standard for calculating total bacterial burden of the BV biofilm has been based on quantifying Escherichia coli 16S rRNA gene copy number. However, E. coli is improper for measuring the bacterial burden of this unique micro-environment. Here, we propose a novel qPCR standard to quantify bacterial burden in vaginal microbial communities, from an optimal state to a mature BV biofilm. These standards consist of different combinations of vaginal bacteria including three common BV-associated bacteria (BVAB) Gardnerella spp. (G), Prevotella spp. (P), and Fannyhessea spp. (F) and commensal Lactobacillus spp. (L) using the 16S rRNA gene (G:P:F:L, G:P:F, G:P:L and 1G:9L). We compared these standards to the traditional E. coli (E) reference standard using known quantities of mock vaginal communities and 16 vaginal samples from women. The E standard significantly underestimated the copy numbers of the mock communities, and this underestimation was significantly greater at lower copy numbers of these communities. The G:P:L standard was the most accurate across all mock communities and when compared to other mixed vaginal standards. Mixed vaginal standards were further validated with vaginal samples. This new G:P:L standard can be used in BV pathogenesis research to enhance reproducibility and reliability in quantitative measurements of BVAB, spanning from the optimal to non-optimal (including BV) vaginal microbiota.
A TLR7-nanoparticle adjuvant promotes a broad immune response against heterologous strains of influenza and SARS-CoV-2
(Springer Nature, 2023) Yin, Qian; Luo, Wei; Mallajosyula, Vamsee; Bo, Yang; Guo, Jing; Xie, Jinghang; Sun, Meng; Verma, Rohit; Li, Chunfeng; Constantz, Christian M.; Wagar, Lisa E.; Li, Jing; Sola, Elsa; Gupta, Neha; Wang, Chunlin; Kask, Oliver; Chen, Xin; Yuan, Xue; Wu, Nicholas C.; Rao, Jianghong; Chien, Yueh-hsiu; Cheng, Jianjun; Pulendran, Bali; Davis, Mark M.; Microbiology and Immunology, School of Medicine
The ideal vaccine against viruses such as influenza and SARS-CoV-2 must provide a robust, durable and broad immune protection against multiple viral variants. However, antibody responses to current vaccines often lack robust cross-reactivity. Here we describe a polymeric Toll-like receptor 7 agonist nanoparticle (TLR7-NP) adjuvant, which enhances lymph node targeting, and leads to persistent activation of immune cells and broad immune responses. When mixed with alum-adsorbed antigens, this TLR7-NP adjuvant elicits cross-reactive antibodies for both dominant and subdominant epitopes and antigen-specific CD8+ T-cell responses in mice. This TLR7-NP-adjuvanted influenza subunit vaccine successfully protects mice against viral challenge of a different strain. This strategy also enhances the antibody response to a SARS-CoV-2 subunit vaccine against multiple viral variants that have emerged. Moreover, this TLR7-NP augments antigen-specific responses in human tonsil organoids. Overall, we describe a nanoparticle adjuvant to improve immune responses to viral antigens, with promising implications for developing broadly protective vaccines.
Abstract 16: Insights into Highly Engraftable Hematopoietic Cells from 27-Year Cryopreserved Umbilical Cord Blood
(Oxford University Press, 2023-09-04) Broxmeyer, Hal; Luchsinger, Larry; Weinberg, Rona; Jimenez, Alexandra; Masson Frenet, Emeline; van't Hof, Wouter; Capitano, Maegan; Hillyer, Christopher; Kaplan, Mark; Cooper, Scott; Ropa, James; Microbiology and Immunology, School of Medicine
Introduction: Cord blood banking has consistently outpaced the utilization of cord blood units (CBUs). Thus, the average duration of cryopreservation among banked CBUs will likely continue to increase. It remains unclear how long cryopreserved CBUs remain functional, and it is critical to determine whether duration of cryopreservation should be used as an exclusionary criterion during selection for clinical use or if alternative post-thaw metrics can identify potent cryopreserved CBUs regardless of age. Objectives: Our goal was to determine whether long-term (27-year) cryopreserved CBUs retain viable and functional hematopoietic stem (HSCs) and progenitor cells (HPCs). We further sought to leverage differences in HSC/HPC function (measured by in vivo engraftment) to demonstrate the utility of using omics approaches to identify candidate genes for use as molecular potency markers. Methods: We performed comprehensive ex vivo, in vivo, and molecular analyses on the numbers, viability, and function of three 27-year cryopreserved CBUs using 3-year cryopreserved and fresh CBUs for comparison. Assays included viability staining, immunophenotyping by flow cytometry, primary and secondary colony forming unit (CFU) assays, ex vivo expansion of immunophenotypic HSCs/HPCs/CFUs, limiting dilution transplantations into immune-deficient mice, secondary transplantations, and RNA-sequencing of sorted HSCs and multipotent progenitor cells. Results: Compared to fresh and recently cryopreserved CBU controls, long-term cryopreserved CBUs yield statistically similar numbers of viable immunophenotypic HSCs, multipotent HPCs, and committed myeloid and lymphoid HPCs. They retain highly functional cells, demonstrating similar primary and secondary CFU numbers and expansion capacity compared to controls, as well as robust engraftment, SCID repopulating cell frequency, and secondary engraftment capacity in mouse models of transplantation. Transcriptomic modelling revealed 18 genes, including MALT1 and MAP2K1, and several gene programs, including lineage determination programs and oxidative stress responses, that are strongly enriched in high engrafting HSCs/HPCs. Discussion: CBUs cryopreserved for up to 27 years retain highly functional HSCs/HPCs. Thus, duration of cryopreservation alone is not an ideal exclusionary criteria for selection of CBUs. Preserving older CBUs may help to maintain a large and diverse pool of donors for clinical selection. Further, transcriptomics can identify candidate genes associated with engraftment for elucidation of possible CBU potency markers regardless of the duration of cryopreservation.
Abstract 26: The Role of Oxygen in Cord Blood Hematopoietic Stem and Progenitor Cell Expansion and Engraftment
(Oxford University Press, 2023-09-04) Ropa, James; Gutch, Sarah; Beasley, Lindsay; Van't Hof, Wouter; Kaplan, Mark; Capitan, Maegan; Microbiology and Immunology, School of Medicine
Introduction: Hematopoietic stem (HSC) and progenitor cells (HPCs) are exposed to differing oxygen tensions ranging from <1% to 21% as they reside in/move through different tissues or are harvested for clinical utility. Functional changes in HSCs/HPCs are induced by acute changes in oxygen tension (e.g., a change in percent of cells in cycle). Objectives: We sought to determine if variable oxygen levels affect expansion and/or functional properties of cord blood (CB) HSCs/HPCs ex vivo and in vivo. Methods: Human CB CD34+ cells were grown in expansion culture +/-UM171, an agonist of HSC self-renewal that expands transplantable CB HSCs, in five oxygen tensions: 1%O2, 3%O2, 5%O2, 14%O2, and 21%O2. HSCs/HPCs were enumerated by flow cytometry. Functional HPCs were enumerated by plating in semi solid media for colony forming unit assays (CFU). Cell cycle and reactive oxygen species (ROS) were measured by flow cytometry. Ability of expanded cells to engraft was determined by transplantation in non-lethally irradiated NSG mice. Results: Immunophenotypic HPCs and functional HPC CFUs expanded significantly more after 7 days of growth in higher oxygen tensions (5%O2-21%O2) compared to lower (1%O2-3%O2), while immunophenotypic HSCs expanded best at 5% O2. HSCs/HPCs grown in low oxygen tensions had significantly lower ROS levels, significantly higher percentage of cells in G0, and were slightly but reproducibly smaller/less granular than those grown in high oxygen levels. HSC/HPC numbers were reduced in high oxygen tensions 1-2 days after plating but were better maintained in low, suggesting cells undergo a culture shock/stress after plating that is mitigated by reduced oxygen. In the presence of UM171, HSCs expanded significantly better at higher oxygen levels, but HPCs are better maintained in 5%O2. Ex vivo CD34+ expansions maintained under physiological O2 levels (1-14%O2) demonstrated significantly better/faster neutrophil recovery following transplantation compared to cells expanded at 21%O2 or input. Discussion: HSCs/HPCs proliferate rapidly in high oxygen but have fewer quiescent cells, higher ROS, and are larger and more granular which are all characteristics associated with exhaustion. While high oxygen allows for faster growth, low tensions may mitigate cell stress and allow for prolonged growth (i.e., HSC/HPC expansion) while maintaining functional properties.
Acetyl-Phosphate Is Not a Global Regulatory Bridge between Virulence and Central Metabolism in Borrelia burgdorferi
(Public Library of Science (PLoS), 2015) Richards, Crystal L.; Lawrence, Kevin A.; Su, Hua; Yang, Youyun; Yang, X. Frank; Dulebohn, Daniel P.; Gherardini, Frank C.; Department of Microbiology and Immunology, IU School of Medicine
In B. burgdorferi, the Rrp2-RpoN-RpoS signaling cascade is a distinctive system that coordinates the expression of virulence factors required for successful transition between its arthropod vector and mammalian hosts. Rrp2 (BB0763), an RpoN specific response regulator, is essential to activate this regulatory pathway. Previous investigations have attempted to identify the phosphate donor of Rrp2, including the cognate histidine kinase, Hk2 (BB0764), non-cognate histidine kinases such as Hk1, CheA1, and CheA2, and small molecular weight P-donors such as carbamoyl-phosphate and acetyl-phosphate (AcP). In a report by Xu et al., exogenous sodium acetate led to increased expression of RpoS and OspC and it was hypothesized this effect was due to increased levels of AcP via the enzyme AckA (BB0622). Genome analyses identified only one pathway that could generate AcP in B. burgdorferi: the acetate/mevalonate pathway that synthesizes the lipid, undecaprenyl phosphate (C55-P, lipid I), which is essential for cell wall biogenesis. To assess the role of AcP in Rrp2-dependent regulation of RpoS and OspC, we used a unique selection strategy to generate mutants that lacked ackA (bb0622: acetate to AcP) or pta (bb0589: AcP to acetyl-CoA). These mutants have an absolute requirement for mevalonate and demonstrate that ackA and pta are required for cell viability. When the ΔackA or Δpta mutant was exposed to conditions (i.e., increased temperature or cell density) that up-regulate the expression of RpoS and OspC, normal induction of those proteins was observed. In addition, adding 20mM acetate or 20mM benzoate to the growth media of B. burgdorferi strain B31 ΔackA induced the expression of RpoS and OspC. These data suggest that AcP (generated by AckA) is not directly involved in modulating the Rrp2-RpoN-RpoS regulatory pathway and that exogenous acetate or benzoate are triggering an acid stress response in B. burgdorferi.
Acetylation of E2 by P300 Mediates Topoisomerase Entry at the Papillomavirus Replicon
(American Society for Microbiology, 2019-03-21) Thomas, Yanique; Androphy, Elliot J.; Microbiology and Immunology, School of Medicine
Human papillomavirus (HPV) E2 proteins are integral for the transcription of viral genes and the replication and maintenance of viral genomes in host cells. E2 recruits the viral DNA helicase E1 to the origin. A lysine (K111), highly conserved among almost all papillomavirus (PV) E2 proteins, is a target for P300 (EP300) acetylation and is critical for viral DNA replication (E. J. Quinlan, S. P. Culleton, S. Y. Wu, C. M. Chiang, et al., J Virol 87:1497-1507, 2013, https://doi.org/10.1128/JVI.02771-12; Y. Thomas and E. J. Androphy, J Virol 92:e01912-17, 2018, https://doi.org/10.1128/JVI.01912-17). Since the viral genome exists as a covalently closed circle of double-stranded DNA, topoisomerase 1 (Topo1) is thought to be required for progression of the replication forks. Due to the specific effect of K111 mutations on DNA unwinding (Y. Thomas and E. J. Androphy, J Virol 92:e01912-17, 2018, https://doi.org/10.1128/JVI.01912-17), we demonstrate that the E2 protein targets Topo1 to the viral origin, and this depends on acetylation of K111. The effect was corroborated by functional replication assays, in which higher levels of P300, but not its homolog CBP, caused enhanced replication with wild-type E2 but not the acetylation-defective K111 arginine mutant. These data reveal a novel role for lysine acetylation during viral DNA replication by regulating topoisomerase recruitment to the replication origin.IMPORTANCE Human papillomaviruses affect an estimated 75% of the sexually active adult population in the United States, with 5.5 million new cases emerging every year. More than 200 HPV genotypes have been identified; a subset of them are linked to the development of cancers from these epithelial infections. Specific antiviral medical treatments for infected individuals are not available. This project examines the mechanisms that control viral genome replication and may allow the development of novel therapeutics.
Activation of Egr-1 expression in astrocytes by HIV-1 Tat: new insights into astrocyte-mediated Tat neurotoxicity
(Springer Nature, 2011-03) Fan, Yan; Zou, Wei; Green, Linden A.; oh Kim, Byung; He, Johnny J.; Microbiology and Immunology, School of Medicine
Human immunodeficiency virus type 1 (HIV-1) Tat plays an important role in HIV-associated neuropathogenesis; the underlying mechanisms are still evolving. We have recently shown that HIV-1 Tat induces expression of glial fibrillary acidic protein (GFAP), a characteristic of HIV-1 infection of the central nervous system (CNS). We have also shown that the Tat-induced GFAP expression in astrocytes is regulated by p300, and that deletion of the early growth response 1 (Egr-1) cis-transacting element within the p300 promoter abolishes Tat-induced GFAP expression. In this study, we further examined the relationship between Tat and Egr-1 in astrocytes. We found increased Egr-1 protein expression in Tat-expressing human astrocytoma cells and mouse primary astrocytes. Using the Egr-1 promoter-driven firefly luciferase reporter gene assay and the site-directed mutagenesis, we demonstrated that Tat increased Egr-1 expression by transactivating the Egr-1 promoter and involving specific serum response elements (SRE) within the promoter. Consistent with these data, we showed that Tat transactivation of the Egr-1 promoter was abrogated when astrocytes were cultured in serum-reduced media. Taken together, these results reveal that Tat directly transactivates Egr-1 expression and suggest that Tat interaction with Egr-1 is probably one of the very upstream molecular events that initiate Tat-induced astrocyte dysfunction and subsequent Tat neurotoxicity.

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