Julie Ledford

Julie Ledford

Associate Professor, Cellular and Molecular Medicine
Associate Professor, Immunobiology
Associate Professor, Medicine
Associate Professor, Clinical Translational Sciences
Associate Professor, Applied BioSciences - GIDP
Member of the Graduate Faculty
Associate Professor, BIO5 Institute
Primary Department
Contact
(520) 626-0276

Work Summary

Julie Ledford's research focuses on respiratory disease, and genetic and molecular mechanisms of allergic airway diseases in children.

Research Interest

Dr. Ledford’s current work in the area of pulmonary surfactant immunobiology combines her knowledge of mouse genetics, pulmonary disease models and immune function regulation and focuses on understanding the role of Surfactant Protein-A (SP-A) and how it regulates signaling pathways within various immune cell populations. Specifically, she is interested in how SP-A regulates degranulation, either directly or indirectly, of two important cell types in asthma: mast cells and eosinophils. More recently, Dr. Ledford’s research has focused on understanding how genetic variation within human SP-A2 alters functionality of the protein in relation to eosinophil activities and how this translates to characteristics observed in human asthma.

Publications

Ledford, J. G., Lo, B., Kislan, M. M., Thomas, J. M., Evans, K., Cain, D. W., Kraft, M., Williams, K. L., & Wright, J. R. (2010). Surfactant protein-A inhibits mycoplasma-induced dendritic cell maturation through regulation of HMGB-1 cytokine activity. Journal of immunology (Baltimore, Md. : 1950), 185(7), 3884-94.

During pulmonary infections, a careful balance between activation of protective host defense mechanisms and potentially injurious inflammatory processes must be maintained. Surfactant protein A (SP-A) is an immune modulator that increases pathogen uptake and clearance by phagocytes while minimizing lung inflammation by limiting dendritic cell (DC) and T cell activation. Recent publications have shown that SP-A binds to and is bacteriostatic for Mycoplasma pneumoniae in vitro. In vivo, SP-A aids in maintenance of airway homeostasis during M. pneumoniae pulmonary infection by preventing an overzealous proinflammatory response mediated by TNF-α. Although SP-A was shown to inhibit maturation of DCs in vitro, the consequence of DC/SP-A interactions in vivo has not been elucidated. In this article, we show that the absence of SP-A during M. pneumoniae infection leads to increased numbers of mature DCs in the lung and draining lymph nodes during the acute phase of infection and, consequently, increased numbers of activated T and B cells during the course of infection. The findings that glycyrrhizin, a specific inhibitor of extracellular high-mobility group box-1 (HMGB-1) abrogated this effect and that SP-A inhibits HMGB-1 release from immune cells suggest that SP-A inhibits M. pneumoniae-induced DC maturation by regulating HMGB-1 cytokine activity.

Ogawa, H., Ledford, J. G., Mukherjee, S., Aono, Y., Nishioka, Y., Lee, J. J., Izumi, K., & Hollingsworth, J. W. (2014). Surfactant protein D attenuates sub-epithelial fibrosis in allergic airways disease through TGF-β. Respiratory research, 15, 143.

Surfactant protein D (SP-D) can regulate both innate and adaptive immunity. Recently, SP-D has been shown to contribute to the pathogenesis of airway allergic inflammation and bleomycin-induced pulmonary fibrosis. However, in allergic airways disease, the role of SP-D in airway remodeling remains unknown. The objective of this study was to determine the contribution of functional SP-D in regulating sub-epithelial fibrosis in a mouse chronic house dust mite model of allergic airways disease.

Kummarapurugu, A., Ledford, J., Karandashova, S., & Voynow, J. (2017). High-Mobility Group Box 1 Upregulates Muc5AC and Muc5B Expression in Primary Airway Epithelial Cells. American Journal of Respiratory Cell and Molecular Biology.
Aono, Y., Ledford, J. G., Mukherjee, S., Ogawa, H., Nishioka, Y., Sone, S., Beers, M. F., Noble, P. W., & Wright, J. R. (2012). Surfactant protein-D regulates effector cell function and fibrotic lung remodeling in response to bleomycin injury. American journal of respiratory and critical care medicine, 185(5), 525-36.

Surfactant protein (SP)-D and SP-A have been implicated in immunomodulation in the lung. It has been reported that patients with idiopathic pulmonary fibrosis (IPF) often have elevated serum levels of SP-A and SP-D, although their role in the disease is not known.

Rabinowitz, J. E., Bowles, D. E., Faust, S. M., Ledford, J. G., Cunningham, S. E., & Samulski, R. J. (2004). Cross-dressing the virion: the transcapsidation of adeno-associated virus serotypes functionally defines subgroups. Journal of virology, 78(9), 4421-32.

For all adeno-associated virus (AAV) serotypes, 60 monomers of the Vp1, Vp2, and Vp3 structural proteins assemble via an unknown mechanism to form an intact capsid. In an effort to better understand the properties of the capsid monomers and their role in viral entry and infection, we evaluated whether monomers from distinct serotypes can be mixed to form infectious particles with unique phenotypes. This transcapsidation approach consisted of the transfection of pairwise combinations of AAV serotype 1 to 5 helper plasmids to produce mosaic capsid recombinant AAV (rAAV). All ratios (19:1, 3:1, 1:1, 1:3, and 1:19) of these mixtures were able to replicate the green fluorescent protein transgene and to produce capsid proteins. A high-titer rAAV was obtained with mixtures that included either serotype 1, 2, or 3, whereas an rAAV of intermediate titer was obtained from serotype 5 mixtures. Only mixtures containing the AAV4 capsid exhibited reduced packaging capacity. The binding profiles of the mixed-virus preparations to either heparin sulfate (HS) or mucin agarose revealed that only AAV3-AAV5 mixtures at the 3:1 ratio exhibited duality in binding. All other mixtures displayed either an abrupt shift or a gradual alteration in the binding profile to the respective ligand upon increase of a capsid component that conferred either HS or mucin binding. The transduction of cell lines was used to further evaluate the phenotypes of these transcapsidated virions. Three transduction profiles were observed: (i) small to no change regardless of ratio, (ii) a gradual increase in transduction consistent with titration of a second capsid component, or (iii) an abrupt increase in transduction (threshold effect) dependent on the specific ratios used. Interestingly, an unexpected synergistic effect in transduction was observed when AAV1 helper constructs were combined with type 2 or type 3 recipient helpers. Further studies determined that at least two components contributed to this observed synergy: (i) heparin-mediated binding from AAV2 and (ii) an unidentified enhancement activity from AAV1 structural proteins. Using this procedure of mixing different AAV helper plasmids to generate "cross-dressed" AAV virions, we propose an additional means of classifying new AAV serotypes into subgroups based on functional approaches to analyze AAV capsid assembly, receptor-mediated binding, and virus trafficking. Exploitation of this approach in generating custom-designed AAV vectors should be of significant value to the field of gene therapy.