Scrub typhus is a life-threatening disease caused Orientia tsutsugamushi, a LPS-negative bacterium that replicates preferentially in endothelial cells (EC) and monocytes. Approximately one million people are infected every year; about one third of world population is at risk of infection. There is no effective vaccine for this infection information on disease pathogenesis is limited. To address these challenges, we have developed mouse models that can mimic pathological features of human scrub typhus. We found that lethal infection was linked to excessive type 1, but deficient type 2, immune responses, which correlated with vascular damage in multiple organs. However, the underlying mechanisms are poorly defined. The goal of this study is to examine the molecular basis of such dysregulation by utilizing the EC-targeting model of O. tsutsugamushi Karp strain (OtK) infection, the most prevalent strain for human infections. Our central hypothesis is that type 1-skewed inflammatory responses and dysregulated angiopoietin (Ang) expression are leading causes for lethal OtK infection.
Aim 1 will examine the cellular sources of IFN-? and dual functions of IFN-?-related responses in bacterial clearance versus immunopathogenesis during Orientia infection. The innate vs. adaptive cell sources of IFN-? and its related CXCR3 chemokines in infected liver, lungs and spleen will be examined by using IFN-? reporter mice, as well as mice deficient in RAG2, IFN-? or CXCR3 expression. Mice receiving anti-IFN-? treatment at different stages of disease will help define in vivo function of IFN-? in bacterial clearance vs. immunopathogenesis. Immunological findings from the single-cell and molecular levels will be integrated with those from tissue bacterial load and pathology evaluations.
Aim 2 will test the hypothesis that endothelial activation/dysregulation initiated by bacterial infectionis ameliorated by IFN-?-related cytokines/chemokines. Lethally infected mice will be treated with recombinant Ang 1, alone or together with vascular endothelial growth factor (VEGF) or anti-IFN-?, at early and late stages of disease. Similar treatment in IFN-?-/- or CXCR3-/- mice, as well as EC-focused in vitro studies, will help dissect complex interplays between cytokines and vascular responses. This mechanism-focused study endorses synergy among research teams (each with unique expertise); it utilizes the state-of-art ABSL3/BSL3 facilities at UTMB. The long-term goal of this study is to define the pathogenic mechanisms associated with Orientia infection and to utilize this information for the design of control strategies. Discovery of the onet and nature of initial dysfunction will reveal the critical window for immune intervention, as well s for signature immune profiles for disease prognosis. This timely study will have a broad implication for other intracellular pathogens.

Public Health Relevance

Scrub typhus is a major public health problem, especially in the Asia-Pacific region, but our current knowledge of this disease is very limited. We will use comprehensive tools and animal models to examine early events in different infected organs and evaluate potential treatment options. This study will improve public health.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21AI117368-01
Application #
8873311
Study Section
Special Emphasis Panel (ZRG1-IDM-B (80))
Program Officer
Perdue, Samuel S
Project Start
2015-02-01
Project End
2017-01-31
Budget Start
2015-02-01
Budget End
2016-01-31
Support Year
1
Fiscal Year
2015
Total Cost
$232,500
Indirect Cost
$82,500
Name
University of Texas Medical Br Galveston
Department
Microbiology/Immun/Virology
Type
Schools of Medicine
DUNS #
800771149
City
Galveston
State
TX
Country
United States
Zip Code
77555
Soong, Lynn (2018) Dysregulated Th1 Immune and Vascular Responses in Scrub Typhus Pathogenesis. J Immunol 200:1233-1240
Soong, Lynn; Shelite, Thomas R; Xing, Yan et al. (2017) Type 1-skewed neuroinflammation and vascular damage associated with Orientia tsutsugamushi infection in mice. PLoS Negl Trop Dis 11:e0005765
Xu, Guang; Mendell, Nicole L; Liang, Yuejin et al. (2017) CD8+ T cells provide immune protection against murine disseminated endotheliotropic Orientia tsutsugamushi infection. PLoS Negl Trop Dis 11:e0005763
Soong, Lynn; Mendell, Nicole L; Olano, Juan P et al. (2016) An Intradermal Inoculation Mouse Model for Immunological Investigations of Acute Scrub Typhus and Persistent Infection. PLoS Negl Trop Dis 10:e0004884
Shelite, Thomas R; Liang, Yuejin; Wang, Hui et al. (2016) IL-33-Dependent Endothelial Activation Contributes to Apoptosis and Renal Injury in Orientia tsutsugamushi-Infected Mice. PLoS Negl Trop Dis 10:e0004467