Altered Circulating Levels of Matrix Metalloproteinases and Inhibitors Associated with Elevated Type 2 Cytokines in Lymphatic Filarial Disease

Lymphatic filariasis afflicts over 120 million people worldwide. While the infection is mostly clinically asymptomatic, approximately 40 million people suffer from overt, morbid clinical pathology characterized by swelling of the scrotal area and lower limbs (hydrocele and lymphedema). Host immunologic factors that influence the pathogenesis of disease in these individuals are not completely understood. Matrix metalloproteinases are a family of circulating and tissue proteins that influence the development of tissue fibrosis. They are regulated by another family of proteins called tissue inhibitors of metalloproteinases. The interplay between these proteins governs tissue fibrosis in a variety of conditions. In addition, certain cytokines are known to promote pro-fibrotic events. We have attempted to elucidate the role of the above-mentioned factors in disease pathogenesis by comparing the plasma levels of the various markers in four groups of individuals: chronic pathology individuals with or without active filarial infection; asymptomatic, filaria-infected individuals; and uninfected, endemic normal individuals. We show that altered ratios of the metalloproteinases and their inhibitors—as well as elevated levels of pro-fibrotic cytokines—characterize filarial infection-induced lymphatic pathology

Interleukin-10- and Transforming Growth Factor β-Independent Regulation of CD8+T Cells Expressing Type 1 and Type 2 Cytokines in Human Lymphatic Filariasis

Lymphatic filariasis is known to be associated with diminished CD4(+) Th1 and elevated CD4(+) Th2 responses to parasite-specific antigens. The roles of cytokine-expressing CD8(+) T cells in immune responses to filarial infections are not well defined. To study the roles of CD8(+) T cells expressing type 1, type 2, and type 17 cytokines in filarial infections, we examined the frequencies of these cells in clinically asymptomatic, patently infected (INF) individuals, directly ex vivo and in response to parasite or nonparasite antigens; these frequencies were compared with the results for individuals with filarial lymphedema (i.e., clinical pathology [CP]) and those without active infection or pathology (i.e., endemic normal [EN]). INF individuals exhibited significant decreases in the frequencies of CD8(+) T cells expressing tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and interleukin-22 (IL-22) at baseline and/or in response to filarial antigens, compared with CP and EN individuals. In contrast, the same individuals exhibited significant increases in the frequencies of CD8(+) T cells expressing IL-4, IL-5, IL-9, IL-13, and IL-21, compared with CP and/or EN individuals. Curative treatment resulted in significantly increased frequencies of CD8(+) T cells expressing IL-2 and significantly decreased frequencies of CD8(+) T cells expressing type 2 cytokines. Finally, the regulation of these responses appears to be independent of IL-10 and transforming growth factor β (TGF-β), since blockade of IL-10 or TGF-β signaling did not significantly alter the frequencies of type 1 or type 2 cytokine-expressing CD8(+) T cells. Our findings suggest that alterations in the frequencies of cytokine-expressing CD8(+) T cells are characteristic features of lymphatic filarial infections

Interleukin 1 (IL-1)- and IL-23-Mediated Expansion of Filarial Antigen-Specific Th17 and Th22 Cells in Filarial Lymphedema

Lymphatic filarial disease is known to be associated with elevated Th1 responses and normal or diminished Th2 responses to parasite-specific antigens. The roles of Th17 cells and the recently described Th22 cells have not been examined in detail in either filarial infection itself or in filarial disease (e.g., lymphedema and elephantiasis). To explore the roles of Th17 and Th22 cells and their subsets, we examined the frequencies of these cells in individuals with filarial lymphedema (chronic pathology [CP]), in clinically asymptomatic infected (INF) individuals, and in uninfected (UN) individuals ex vivo and in response to parasite and nonparasite antigens. Those with disease (CP) had significantly expanded frequencies of Th17 and Th22 cells, compared with either INF or UN individuals, at baseline (ex vivo) and in response to parasite antigens. This antigen-driven expansion of Th17 and Th22 cells was dependent on interleukin 1 (IL-1), IL-23, and, to lesser extent, transforming growth factor β (TGF-β), as blockade of any of these cytokines resulted in significantly diminished frequencies of Th17 and Th22 cells. Our findings, therefore, suggest that filarial parasite-driven expansion of Th17 and Th22 cells is associated with the pathogenesis of filarial infections and disease

Toll-Like Receptor- and Filarial Antigen-Mediated, Mitogen-Activated Protein Kinase- and NF-κB-Dependent Regulation of Angiogenic Growth Factors in Filarial Lymphatic Pathology

Filarial lymphatic pathology is of multifactorial origin, with inflammation, lymphangiogenesis, and innate immune responses all playing important roles. The role of Toll-like receptors (TLRs) in the development of filarial pathology is well characterized. Similarly, the association of pathology with elevated levels of plasma angiogenic factors has also been documented. To examine the association between TLR function and the development of lymphangiogenesis in filarial infections, we examined TLR- and filarial antigen-induced expression and production of various angiogenic growth factors. We demonstrate that TLR ligands (specifically TLR2, -3, and -5 ligands) induce significantly increased expression/production of vascular endothelial growth factor A (VEGF-A) and angiopoietin-1 (Ang-1) in the peripheral blood mononuclear cells of individuals with lymphatic pathology (CP individuals) compared to that in cells of asymptomatic infected (INF) individuals. Similarly, filarial antigens induce significantly enhanced production of VEGF-C in CP compared with INF individuals. TLR2-mediated enhancement of angiogenic growth factor production in CP individuals was shown to be dependent on mitogen-activated protein kinase (MAPK) and NF-κB signaling, as pharmacologic inhibition of either extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, or NF-κB signaling resulted in significantly diminished production of VEGF-A and Ang-1. Our data therefore strongly suggest an important association between TLR signaling and lymphangiogenesis in the development of pathology in human lymphatic filariasis

Parasite-Antigen Driven Expansion of IL-5− and IL-5+ Th2 Human Subpopulations in Lymphatic Filariasis and Their Differential Dependence on IL-10 and TGFβ

BACKGROUND: Two different Th2 subsets have been defined recently on the basis of IL-5 expression – an IL-5(+)Th2 subset and an IL-5(−)Th2 subset in the setting of allergy. However, the role of these newly described CD4(+) T cells subpopulations has not been explored in other contexts. METHODS: To study the role of the Th2 subpopulation in a chronic, tissue invasive parasitic infection (lymphatic filariasis), we examined the frequency of IL-5(+)IL-4(+)IL-13(+) CD4(+) T cells and IL-5(−)IL-4 IL-13(+) CD4(+) T cells in asymptomatic, infected individuals (INF) and compared them to frequencies (F(o)) in filarial-uninfected (UN) individuals and to those with filarial lymphedema (CP). RESULTS: INF individuals exhibited a significant increase in the spontaneously expressed and antigen-induced F(o) of both Th2 subpopulations compared to the UN and CP. Interestingly, there was a positive correlation between the F(o) of IL-5(+)Th2 cells and the absolute eosinophil and neutrophil counts; in addition there was a positive correlation between the frequency of the CD4(+)IL-5(−)Th2 subpopulation and the levels of parasite antigen – specific IgE and IgG4 in INF individuals. Moreover, blockade of IL-10 and/or TGFβ demonstrated that each of these 2 regulatory cytokines exert opposite effects on the different Th2 subsets. Finally, in those INF individuals cured of infection by anti-filarial therapy, there was a significantly decreased F(o) of both Th2 subsets. CONCLUSIONS: Our findings suggest that both IL-5(+) and IL-5(−)Th2 cells play an important role in the regulation of immune responses in filarial infection and that these two Th2 subpopulations may be regulated by different cytokine-receptor mediated processes

Circulating Microbial Products and Acute Phase Proteins as Markers of Pathogenesis in Lymphatic Filarial Disease

Lymphatic filariasis can be associated with development of serious pathology in the form of lymphedema, hydrocele, and elephantiasis in a subset of infected patients. Dysregulated host inflammatory responses leading to systemic immune activation are thought to play a central role in filarial disease pathogenesis. We measured the plasma levels of microbial translocation markers, acute phase proteins, and inflammatory cytokines in individuals with chronic filarial pathology with (CP Ag+) or without (CP Ag−) active infection; with clinically asymptomatic infections (INF); and in those without infection (endemic normal [EN]). Comparisons between the two actively infected groups (CP Ag+ compared to INF) and those without active infection (CP Ag− compared to EN) were used preliminarily to identify markers of pathogenesis. Thereafter, we tested for group effects among all the four groups using linear models on the log transformed responses of the markers. Our data suggest that circulating levels of microbial translocation products (lipopolysaccharide and LPS-binding protein), acute phase proteins (haptoglobin and serum amyloid protein-A), and inflammatory cytokines (IL-1β, IL-12, and TNF-α) are associated with pathogenesis of disease in lymphatic filarial infection and implicate an important role for circulating microbial products and acute phase proteins

Correlation between MMP/TIMP ratios and Type 2 cytokines in filaria-infected individuals.

<p>(A) MMP/TIMP ratios were correlated with the levels of IL-13 from individuals with active infection [CP Ag+ and INF (<i>n</i> = 102–114)]. (B) MMP/TIMP ratios were correlated with the levels of IL-5 from individuals with active infection [CP Ag+ and INF (<i>n</i> = 102–114)]. CP Ag+ individuals are shown in gray circles and INF in dark circles. P and r values were calculated using the Spearman rank correlation test.</p

Filarial lymphedema is not associated with elevated levels of FGF-2 or PDGF-AA.

<p>(A) Plasma levels of FGF-2 and PDGF-AA from filarial lymphedema individuals with active infection [CP Ag+] (<i>n</i> = 21–22) and asymptomatic infected [INF] (n = 22–39) individuals were measured by ELISA. (B) Plasma levels of FGF-2 and PDGF-AA from filarial lymphedema individuals without active infection [CP Ag−] (n = 22–38) and endemic normal [EN] (n = 21–33) individuals were measured by ELISA. P values were calculated using the Mann-Whitney test.</p

Characteristics of the study population.

<p>Characteristics of the study population.</p

Filarial lymphedema is associated with elevated levels of TIMP-1 and 2.

<p>(A) Plasma levels of TIMP-1, -2, -3, and -4 from filarial lymphedema individuals with active infection [CP Ag+] (<i>n</i> = 28) and asymptomatic infected [INF] (n = 66–76) individuals were measured by ELISA. (B) Plasma levels of TIMP-1, -2, -3, and -4 from filarial lymphedema individuals without active infection [CP Ag−] (n = 66–76) and endemic normal [EN] (n = 73) individuals were measured by ELISA. P values were calculated using the Mann-Whitney test.</p