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All Publications

  • Identification of HIV gp41-specific antibodies that mediate killing of infected cells PLOS PATHOGENS Williams, K. L., Stumpf, M., Naiman, N., Ding, S., Garrett, M., Gobillot, T., Vezina, D., Dusenbury, K., Ramadoss, N. S., Basom, R., Kim, P. S., Finzi, A., Overbaugh, J. 2019; 15 (2)
  • Enhancing natural killer cell function with gp41-targeting bispecific antibodies to combat HIV infection Biorxiv Ramadoss, N. S., Zhao, N. A., Richardson, B. A., Grant, P. M., Kim, P. S., Blish, C. A. 2019
  • Cell-based screen for discovering lipopolysaccharide biogenesis inhibitors PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Zhang, G., Baidin, V., Pahil, K. S., Moison, E., Tomasek, D., Ramadoss, N. S., Chatterjee, A. K., McNamara, C. W., Young, T. S., Schultz, P. G., Meredith, T. C., Kahne, D. 2018; 115 (26): 6834?39


    New drugs are needed to treat gram-negative bacterial infections. These bacteria are protected by an outer membrane which prevents many antibiotics from reaching their cellular targets. The outer leaflet of the outer membrane contains LPS, which is responsible for creating this permeability barrier. Interfering with LPS biogenesis affects bacterial viability. We developed a cell-based screen that identifies inhibitors of LPS biosynthesis and transport by exploiting the nonessentiality of this pathway in Acinetobacter We used this screen to find an inhibitor of MsbA, an ATP-dependent flippase that translocates LPS across the inner membrane. Treatment with the inhibitor caused mislocalization of LPS to the cell interior. The discovery of an MsbA inhibitor, which is universally conserved in all gram-negative bacteria, validates MsbA as an antibacterial target. Because our cell-based screen reports on the function of the entire LPS biogenesis pathway, it could be used to identify compounds that inhibit other targets in the pathway, which can provide insights into vulnerabilities of the gram-negative cell envelope.

    View details for DOI 10.1073/pnas.1804670115

    View details for Web of Science ID 000436245000091

    View details for PubMedID 29735709

    View details for PubMedCentralID PMC6042065

  • Switch-mediated activation and retargeting of CAR-T cells for B-cell malignancies PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Rodgers, D. T., Mazagova, M., Hampton, E. N., Cao, Y., Ramadoss, N. S., Hardy, I. R., Schulman, A., Du, J., Wang, F., Singer, O., Ma, J., Nunez, V., Shen, J., Woods, A. K., Wright, T. M., Schultz, P. G., Kim, C. H., Young, T. S. 2016; 113 (4): E459-E468


    Chimeric antigen receptor T (CAR-T) cell therapy has produced impressive results in clinical trials for B-cell malignancies. However, safety concerns related to the inability to control CAR-T cells once infused into the patient remain a significant challenge. Here we report the engineering of recombinant antibody-based bifunctional switches that consist of a tumor antigen-specific Fab molecule engrafted with a peptide neo-epitope, which is bound exclusively by a peptide-specific switchable CAR-T cell (sCAR-T). The switch redirects the activity of the bio-orthogonal sCAR-T cells through the selective formation of immunological synapses, in which the sCAR-T cell, switch, and target cell interact in a structurally defined and temporally controlled manner. Optimized switches specific for CD19 controlled the activity, tissue-homing, cytokine release, and phenotype of sCAR-T cells in a dose-titratable manner in a Nalm-6 xenograft rodent model of B-cell leukemia. The sCAR-T-cell dosing regimen could be tuned to provide efficacy comparable to the corresponding conventional CART-19, but with lower cytokine levels, thereby offering a method of mitigating cytokine release syndrome in clinical translation. Furthermore, we demonstrate that this methodology is readily adaptable to targeting CD20 on cancer cells using the same sCAR-T cell, suggesting that this approach may be broadly applicable to heterogeneous and resistant tumor populations, as well as other liquid and solid tumor antigens.

    View details for DOI 10.1073/pnas.1524155113

    View details for Web of Science ID 000368617900010

    View details for PubMedCentralID PMC4743815

  • An Anti-B Cell Maturation Antigen Bispecific Antibody for Multiple Myeloma JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Ramadoss, N. S., Schulman, A. D., Choi, S., Rodgers, D. T., Kazane, S. A., Kim, C., Lawson, B. R., Young, T. S. 2015; 137 (16): 5288?91


    The development of immunotherapies for multiple myeloma is critical to provide new treatment strategies to combat drug resistance. We report a bispecific antibody against B cell maturation antigen (BiFab-BCMA), which potently and specifically redirects T cells to lyse malignant multiple myeloma cells. BiFab-BCMA lysed target BCMA-positive cell lines up to 20-fold more potently than a CS1-targeting bispecific antibody (BiFab-CS1) developed in an analogous fashion. Further, BiFab-BCMA robustly activated T cells in vitro and mediated rapid tumor regression in an orthotopic xenograft model of multiple myeloma. The in vitro and in vivo activities of BiFab-BCMA are comparable to those of anti-BCMA chimeric antigen receptor T cell therapy (CAR-T-BCMA), for which two clinical trials have recently been initiated. A BCMA-targeted bispecific antibody presents a promising treatment option for multiple myeloma.

    View details for DOI 10.1021/jacs.5b01876

    View details for Web of Science ID 000353931500012

    View details for PubMedID 25826669

  • Small molecule inhibitors of trans-translation have broad-spectrum antibiotic activity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Ramadoss, N. S., Alumasa, J. N., Cheng, L., Wang, Y., Li, S., Chambers, B. S., Chang, H., Chatterjee, A. K., Brinker, A., Engels, I. H., Keiler, K. C. 2013; 110 (25): 10282?87


    The trans-translation pathway for protein tagging and ribosome release plays a critical role for viability and virulence in a wide range of pathogens but is not found in animals. To explore the use of trans-translation as a target for antibiotic development, a high-throughput screen and secondary screening assays were used to identify small molecule inhibitors of the pathway. Compounds that inhibited protein tagging and proteolysis of tagged proteins were recovered from the screen. One of the most active compounds, KKL-35, inhibited the trans-translation tagging reaction with an IC50 = 0.9 然. KKL-35 and other compounds identified in the screen exhibited broad-spectrum antibiotic activity, validating trans-translation as a target for drug development. This unique target could play a key role in combating strains of pathogenic bacteria that are resistant to existing antibiotics.

    View details for DOI 10.1073/pnas.1302816110

    View details for Web of Science ID 000321500200059

    View details for PubMedID 23733947

    View details for PubMedCentralID PMC3690859

  • tmRNA Is Essential in Shigella flexneri PLOS ONE Ramadoss, N. S., Zhou, X., Keiler, K. C. 2013; 8 (2): e57537


    Nonstop mRNAs pose a challenge for bacteria, because translation cannot terminate efficiently without a stop codon. The trans-translation pathway resolves nonstop translation complexes by removing the nonstop mRNA, the incomplete protein, and the stalled ribosome. P1 co-transduction experiments demonstrated that tmRNA, a key component of the trans-translation pathway, is essential for viability in Shigella flexneri. tmRNA was previously shown to be dispensable in the closely related species Escherichia coli, because E. coli contains a backup system for trans-translation mediated by the alternative release factor ArfA. Genome sequence analysis showed that S. flexneri does not have a gene encoding ArfA. E. coli ArfA could suppress the requirement for tmRNA in S. flexneri, indicating that tmRNA is essential in S. flexneri because there is no functional backup system. These data suggest that resolution of nonstop translation complexes is required for most bacteria.

    View details for DOI 10.1371/journal.pone.0057537

    View details for Web of Science ID 000316849500112

    View details for PubMedID 23451240

    View details for PubMedCentralID PMC3581467

  • Pharmacological Inhibition of the ClpXP Protease Increases Bacterial Susceptibility to Host Cathelicidin Antimicrobial Peptides and Cell Envelope-Active Antibiotics ANTIMICROBIAL AGENTS AND CHEMOTHERAPY McGillivray, S. M., Tran, D. N., Ramadoss, N. S., Alumasa, J. N., Okumura, C. Y., Sakoulas, G., Vaughn, M. M., Zhang, D. X., Keiler, K. C., Nizet, V. 2012; 56 (4): 1854?61


    The ClpXP protease is a critical bacterial intracellular protease that regulates protein turnover in many bacterial species. Here we identified a pharmacological inhibitor of the ClpXP protease, F2, and evaluated its action in Bacillus anthracis and Staphylococcus aureus. We found that F2 exhibited synergistic antimicrobial activity with cathelicidin antimicrobial peptides and antibiotics that target the cell well and/or cell membrane, such as penicillin and daptomycin, in B. anthracis and drug-resistant strains of S. aureus. ClpXP inhibition represents a novel therapeutic strategy to simultaneously sensitize pathogenic bacteria to host defenses and pharmaceutical antibiotics.

    View details for DOI 10.1128/AAC.05131-11

    View details for Web of Science ID 000301898500023

    View details for PubMedID 22252821

    View details for PubMedCentralID PMC3318395

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