Despite the advent of mass chemotherapy programs, schistosomiasis remains a very significant cause of human disease in Africa, The Middle East, Asia and South America. Our long-term goal is to understand the protective mechanisms that allow host survival in the face of extensive tissue damage associated with chronic schistosomiasis. Work over the last 15 years has revealed that the nature of the CD4+ T cell response induced by egg antigens is critical in determining the death or survival outcome of infection. The infection induces a Th2 response, and the Th2 bias is critical, since in the absence of IL-4, a major product of Th2 cells, infected mice die rapidly after eggs begin to be produced by the parasites, due to an immunopathologic response in which NO and TNF? (products of classically activated, M1 macrophages) are implicated. In contrast, infected wild type mice survive over long periods of time, thereby modeling the chronic nature of the disease in humans. In this model, as in humans, infection severity is linked to parasite burden (the more worm pairs a mouse is infected with, the more eggs it is exposed to, and the sicker it will be), and over time the repeated cycles of inflammation and resolution can lead to severe liver fibrosis, which again mirrors the most serious disease manifestation of human schistosomiasis. There is evidence that the protective mechanisms that permit host survival during schistosomiasis are mediated by cells that that can be categorized as alternatively activated (M2) macrophages, and that IgG1, which is made by B cells that have been helped by IL-4 producing T follicular helper (Tfh) cells, plays a role in this process during the later stages of disease. However, we have surprisingly little understanding of how these macrophage- and B cell-dependent mechanisms operate, and it is on these areas that our proposal focuses. We have two aims.
Specific Aim 1 is to understand the role of the Tfh/B cell axis during infection. Here we will determine the evolution of the T cell and B cell responses over time during infection, incorporating a detailed study of Th2 cells, Tfh cells and plasma cells. We will ask whether both Th2 and Tfh responses are modulated over time, and whether increasing the relative output of Tfh cells vs. Th2 effector cells improves the prognosis during chronic schistosomiasis. We will ask how B cells get into the liver during schistosomiasis and explore the fate and function of the cells once they have infiltrated this organ.
Specific Aim 2 is to establish the origin and function of hepatic macrophages during chronic infection. For this aim we will use new tools to explore the origin and role of macrophages in the hepatic tissues of chronically infected mice. We will ask whether the primary role of antibody is (in the form of immune complexes) to bind to Fc?RIIB on monocytes/macrophages and thereby inhibit inflammation during chronic schistosomiasis. We will determine how the absence of B cells influences the hepatic macrophage population and determine whether dysregulated thromboxane-A2 production by macrophages underlies the development of severe portal hypertension during chronic schistosomiasis in the absence of antibody.

Public Health Relevance

Schistosomiasis is a chronic Neglected Tropical Disease caused by infection with parasitic flatworms of the genus Schistosoma, that despite the availability of an excellent drug, and ongoing treatment programs, remains as prevalent as it was 20 years ago and continues to represent a cause of severe morbidity in millions of people. Infection causes a complex multi-organ disease characterized by marked inflammation in the liver, intestine and, in the most severe ceases, lungs. Survival with infection requires an appropriately regulated Th2 response. Understanding the intrinsic regulatory mechanisms that permit survival with chronic schistosome infection has broad therapeutic implications for not only schistosomiasis, but also other helminth infections, allergy/asthma and autoimmunity.

Agency
National Institute of Health (NIH)
Type
Research Project (R01)
Project #
5R01AI032573-23
Application #
8663821
Study Section
Pathogenic Eukaryotes Study Section (PTHE)
Program Officer
Wali, Tonu M
Project Start
Project End
Budget Start
Budget End
Support Year
23
Fiscal Year
2014
Total Cost
Indirect Cost
Name
Washington University
Department
Pathology
Type
Schools of Medicine
DUNS #
City
Saint Louis
State
MO
Country
United States
Zip Code
63130
Fairfax, Keke C; Everts, Bart; Smith, Amber M et al. (2013) Regulation of the development of the hepatic B cell compartment during Schistosoma mansoni infection. J Immunol 191:4202-10
Pedras-Vasconcelos, J A; Brunet, L R; Pearce, E J (2001) Profound effect of the absence of IL-4 on T cell responses during infection with Schistosoma mansoni. J Leukoc Biol 70:737-44
La Flamme, A C; Patton, E A; Pearce, E J (2001) Role of gamma interferon in the pathogenesis of severe schistosomiasis in interleukin-4-deficient mice. Infect Immun 69:7445-52
La Flamme, A C; Patton, E A; Bauman, B et al. (2001) IL-4 plays a crucial role in regulating oxidative damage in the liver during schistosomiasis. J Immunol 166:1903-11
La Flamme, A C; MacDonald, A S; Pearce, E J (2000) Role of IL-6 in directing the initial immune response to schistosome eggs. J Immunol 164:2419-26
La Flamme, A C; Pearce, E J (1999) The absence of IL-6 does not affect Th2 cell development in vivo, but does lead to impaired proliferation, IL-2 receptor expression, and B cell responses. J Immunol 162:5829-37
Brunet, L R; Kopf, M A; Pearce, E J (1999) Schistosoma mansoni: IL-4 is necessary for concomitant immunity in mice. J Parasitol 85:734-6
Brunet, L R; Finkelman, F D; Cheever, A W et al. (1997) IL-4 protects against TNF-alpha-mediated cachexia and death during acute schistosomiasis. J Immunol 159:777-85
Humphries, D; Vella, A T; Pearce, E J (1994) Increased CD4+ T cell-dependent anti-erythrocyte antibody levels following the onset of parasite egg production in Schistosoma mansoni infected mice. Parasite Immunol 16:469-77
Vella, A T; Pearce, E J (1994) Schistosoma mansoni egg-primed Th0 and Th2 cells: failure to down-regulate IFN-gamma production following in vitro culture. Scand J Immunol 39:12-8

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