[show abstract][hide abstract] ABSTRACT: The filarial nematode Onchocerca volvulus is the causative organism of river blindness. Our previous studies demonstrated an essential role for endosymbiotic Wolbachia bacteria in corneal disease, which is characterized by neutrophil infiltration into the corneal stroma and the development of corneal haze. To determine the role of Toll-like receptors (TLRs) in neutrophil recruitment and activation, we injected a soluble extract of O. volvulus containing Wolbachia bacteria into the corneal stromata of C57BL/6, TLR2-/-, TLR4-/-, TLR2/4-/-, and TLR9-/- mice. We found an essential role for TLR2, but not TLR4 or TLR9, in neutrophil recruitment to the cornea and development of corneal haze. Furthermore, chimeric mouse bone marrow studies showed that resident bone marrow-derived cells in the cornea can initiate this response. TLR2 expression was also essential for CXC chemokine production by resident cells in the cornea, including corneal fibroblasts, and for neutrophil activation. Taken together, these findings indicate that Wolbachia activates TLR2 on resident bone marrow-derived cells in the corneal stroma to produce CXC chemokines, leading to neutrophil recruitment to the corneal stroma, and that TLR2 mediates O. volvulus/Wolbachia-induced neutrophil activation and development of corneal haze.
Infection and immunity 01/2008; 75(12):5908-15. · 4.21 Impact Factor
[show abstract][hide abstract] ABSTRACT: Toll-like receptors (TLRs) regulate dendritic cell function and activate signals that mediate the nature of the adaptive immune response. The current study examined the role of TLRs in dendritic cell activation and in regulating T cell and antibody responses to antigens from the filarial parasites Onchocerca volvulus and Brugia malayi, which cause river blindness and lymphatic filariasis, respectively. Bone-marrow-derived CD11c(+) cells from C57BL/6 and TLR4(-/-) mice produced high levels of IL-6 and RANTES, and showed elevated surface CD40 expression, whereas CD11c(+) cells from myeloid differentiation factor 88(-/-) (MyD88(-/-)), TLR2(-/-) and TLR2/4(-/-) mice were not activated. Similarly, IFN-gamma production by splenocytes from immunized TLR2(-/-) mice was significantly impaired compared with splenocytes from C57BL/6 and TLR4(-/-) mice. In contrast, there was no difference among these strains in Th2-associated responses including IL-5 production by splenocytes from immunized animals, serum IgE and IgG(1), or eosinophil infiltration into the corneal stroma. Neutrophil recruitment to the cornea and CXC chemokine production was inhibited in immunized TLR2(-/-) mice compared with C57BL/6 and TLR4(-/-) mice. Taken together, these findings demonstrate an essential role for TLR2 in filaria-induced dendritic cell activation, IFN-gamma production and neutrophil migration to the cornea, but does not affect filaria-induced Th2-associated responses.
[show abstract][hide abstract] ABSTRACT: The discovery that endosymbiotic Wolbachia bacteria play an important role in the pathophysiology of diseases caused by filarial nematodes, including lymphatic filariasis and onchocerciasis (river blindness) has transformed our approach to these disabling diseases. Because these parasites infect hundreds of millions of individuals worldwide, understanding host factors involved in the pathogenesis of filarial-induced diseases is paramount. However, the role of early innate responses to filarial and Wolbachia ligands in the development of filarial diseases has not been fully elucidated. To determine the role of TLRs, we used cell lines transfected with human TLRs and macrophages from TLR and adaptor molecule-deficient mice and evaluated macrophage recruitment in vivo. Extracts of Brugia malayi and Onchocerca volvulus, which contain Wolbachia, directly stimulated human embryonic kidney cells expressing TLR2, but not TLR3 or TLR4. Wolbachia containing filarial extracts stimulated cytokine production in macrophages from C57BL/6 and TLR4(-/-) mice, but not from TLR2(-/-) or TLR6(-/-) mice. Similarly, macrophages from mice deficient in adaptor molecules Toll/IL-1R domain-containing adaptor-inducing IFN-beta and Toll/IL-1R domain-containing adaptor-inducing IFN-beta-related adaptor molecule produced equivalent cytokines as wild-type cells, whereas responses were absent in macrophages from MyD88(-/-) and Toll/IL-1R domain-containing adaptor protein (TIRAP)/MyD88 adaptor-like (Mal) deficient mice. Isolated Wolbachia bacteria demonstrated similar TLR and adaptor molecule requirements. In vivo, macrophage migration to the cornea in response to filarial extracts containing Wolbachia was dependent on TLR2 but not TLR4. These results establish that the innate inflammatory pathways activated by endosymbiotic Wolbachia in B. malayi and O. volvulus filaria are dependent on TLR2-TLR6 interactions and are mediated by adaptor molecules MyD88 and TIRAP/Mal.
The Journal of Immunology 02/2007; 178(2):1068-76. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Chronic infection with filarial nematodes results in development of a suppressive response to an immense parasite burden, thereby limiting pathological and clinical manifestations. However, pro-inflammatory responses to dead and degenerating Onchocerca volvulus worms and release of endosymbiotic Wolbachia bacteria result in corneal opacification, sacrification and visual impairment. This review discusses host and parasite factors implicated in maintaining this balance of pro- an anti-inflammatory responses, and will focus on adaptive and innate immunity to filarial antigens and endosymbiotic Wolbachia bacteria.
Chemical immunology and allergy 02/2007; 92:254-65.
[show abstract][hide abstract] ABSTRACT: Endosymbiotic Wolbachia bacteria that infect the filarial nematode Onchocerca volvulus were previously found to have an essential role in the pathogenesis of river blindness. The current study demonstrates that corneal inflammation induced by Wolbachia or O. volvulus antigens containing Wolbachia is completely dependent on expression of myeloid differentiation factor 88.
Infection and Immunity 05/2006; 74(4):2442-5. · 4.07 Impact Factor
[show abstract][hide abstract] ABSTRACT: Endosymbiotic Wolbachia bacteria are abundant in the filarial nematodes that cause onchocerciasis (river blindness), including the larvae (microfilariae) that migrate into the cornea. Using a mouse model of ocular onchocerciasis, we recently demonstrated that it is these endosymbiotic bacteria rather than the nematodes per se that induce neutrophil infiltration to the corneal stroma and loss of corneal clarity (Saint Andre et al., Science 295:1892-1895, 2002). To better understand the role of Wolbachia organisms in the pathogenesis of this disease, we examined the fate of these bacteria in the cornea by immunoelectron microscopy. Microfilariae harboring Wolbachia organisms were injected into mouse corneas, and bacteria were detected with antibody to Wolbachia surface protein. Within 18 h of injection, neutrophils completely surrounded the nematodes and were in close proximity to Wolbachia organisms. Wolbachia surface protein labeling was also prominent in neutrophil phagosomes, indicating neutrophil ingestion of Wolbachia organisms. Furthermore, the presence of numerous electron-dense granules around the phagosomes indicated that neutrophils were activated. To determine if Wolbachia organisms directly activate neutrophils, peritoneal neutrophils were incubated with either parasite extracts containing Wolbachia organisms, parasite extracts depleted of Wolbachia organisms (by antibiotic treatment of worms), or Wolbachia organisms isolated from filarial nematodes. After 18 h of incubation, we found that isolated Wolbachia organisms stimulated production of tumor necrosis factor alpha and CXC chemokines macrophage inflammatory protein 2 and KC by neutrophils in a dose-dependent manner. Similarly, these cytokines were induced by filarial extracts containing Wolbachia organisms but not by Wolbachia-depleted extracts. Taken together, these findings indicate that neutrophil activation is an important mechanism by which Wolbachia organisms contribute to the pathogenesis of ocular onchocerciasis.
Infection and Immunity 11/2004; 72(10):5687-92. · 4.07 Impact Factor
[show abstract][hide abstract] ABSTRACT: In this review, we describe the pathogenic role of Wolbachia endosymbiotic bacteria in filarial diseases, focusing on the host innate immune responses to filarial and Wolbachia products. A description of the host pathogen recognition and early inflammatory responses including TLR4-mediated signalling, chemokine and cytokine responses and inflammatory cell recruitment is provided from human studies and from animal models of filarial disease. Finally, the impact of the discovery and characterization of Wolbachia on filarial research and treatment programmes is discussed.
[show abstract][hide abstract] ABSTRACT: Infection with the parasitic nematode Onchocerca volvulus is associated with inflammation of the skin and cornea that can lead to blindness. Corneal damage is thought to occur as a result of the host inflammatory responses to degenerating microfilariae in the eye. We have utilized a murine model of corneal inflammation (keratitis) to investigate the immune and inflammatory responses associated with river blindness. Soluble extracts of O. volvulus, a filarial species that contains the endosymbiont bacteria Wolbachia or Acanthocheilonema viteae (a nematode not naturally infected with the bacteria) were injected into mouse corneas. Inflammatory responses and corneal changes were measured. We demonstrated a major role for endosymbiont Wolbachia bacteria and Toll-like receptor 4 (TLR4) in the pathogenesis of ocular onchocerciasis.
Journal of Endotoxin Research 02/2003; 9(6):390-4. · 3.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: Little is known about the effect of microgravity on gene expression, particularly in vivo during embryonic development. Using transgenic zebrafish that express the gfp gene under the influence of a beta-actin promoter, we examined the affect of simulated-microgravity on GFP expression in the heart. Zebrafish embryos, at the 18-20 somite-stage, were exposed to simulated-microgravity for 24 hours. The intensity of GFP fluorescence associated with the heart was then determined using fluorescence microscopy. Our measurements indicated that simulated-microgravity induced a 23.9% increase in GFP-associated fluorescence in the heart. In contrast, the caudal notochord showed a 17.5% increase and the embryo as a whole showed only an 8.5% increase in GFP-associated fluorescence. This suggests that there are specific effects on the heart causing the more dramatic increase. These studies indicate that microgravity can influence gene expression and demonstrate the usefulness of this in vivo model of 'reporter-gene' expression for studying the effects of microgravity.
Advances in Space Research 02/2003; 32(8):1641-6. · 1.18 Impact Factor
[show abstract][hide abstract] ABSTRACT: Over 150 million individuals worldwide are infected with filarial nematodes, which include Wuchereria bancrofti and Brugia malayi that cause lymphatic filariasis, and Onchocerca volvulus, which causes onchocerciasis (river blindness). These nematodes all harbor endosymbiotic Wolbachia bacteria throughout their life cycles, and it has become increasingly clear that Wolbachia have an important role in the pathogenesis of disease in the human host. This review discusses the evidence supporting the role of Wolbachia in the pathogenesis of river blindness, and the critical role of the Toll-like receptor pathway in the host immune response to these bacteria.