Eotaxin Is Specifically Cleaved by Hookworm Metalloproteases Preventing Its Action In Vitro and In Vivo

Abstract

Eotaxin is a potent eosinophil chemoattractant that acts selectively through CCR3, which is expressed on eosinophils, basophils, mast cells, and Th2-type T cells. This arm of the immune system is believed to have evolved to control helminthic parasites. We hypothesized that helminths may employ mechanisms to inhibit eosinophil recruitment, to prolong worm survival in the host. We observed that the excretory/secretory products of the hookworm Necator americanus inhibited eosinophil recruitment in vivo in response to eotaxin, but not leukotriene B4, a phenomenon that could be prevented by the addition of protease inhibitors. Using Western blotting, N. americanus supernatant was shown to cause rapid proteolysis of eotaxin, but not IL-8 or eotaxin-2. N. americanus homogenate was fractionated by gel filtration chromatography, and a FACS-based bioassay measured the ability of each fraction to inhibit the activity of a variety of chemokines. This resulted in two peaks of eotaxin-degrading activity, corresponding to ∼15 and 50 kDa molecular mass. This activity was specific for eotaxin, as responses to other agonists tested were unaffected. Proteolysis of eotaxin was prevented by EDTA and phenanthroline, indicating that metalloprotease activity was involved. Production of enzymes inactivating eotaxin may be a strategy employed by helminths to prevent recruitment and activation of eosinophils at the site of infection. As such this represents a novel mechanism of regulation of chemokine function in vivo. The existence of CCR3 ligands other than eotaxin (e.g., eotaxin-2) may reflect the evolution of host counter measures to parasite defense systems.

An asthma-associated genetic variant of STAT6 predicts low burden of ascaris worm infestation

“…A polygenic interaction, with a major effect from the pivotal Th-2 transduction molecule (STAT6), in limiting worm burden also accords with the strong evolutionary pressure that must be exerted by endemic helminth infection in billions of humans, and the helminths' many evasive and subversive tactics, directed at diverse elements of the human's protective responses to the parasite. 1,27 The chromosomal location of STAT-6 (chromosome 12) does not match chromosomal linkages recently observed between ascaris burden and chromosomes 1 and 13 in a Nepalese genetic isolate (Jirels). 28 Genetic differences between the Chinese and Jirels may explain this discrepancy, but we have no information on STAT6 variation in the Jirels.…”

Indomethacin Causes Prostaglandin D2-like and Eotaxin-like Selective Responses in Eosinophils and Basophils

“…Cell Preparation-Peripheral blood leukocyte preparations of granulocytes (containing eosinophils and neutrophils) and mononuclear cells (including basophils, monocytes, and lymphocytes) were prepared by plasma/Percoll gradients or Histopaque gradients as described (14,30,38). Cells prepared by either technique gave similar results in the highly sensitive assays of leukocyte shape change (data not shown).…”

Necator americanus: The Na-ASP-2 protein secreted by the infective larvae induces neutrophil recruitment in vivo and in vitro

“…The literature reveals that both inhibitory and chemoattractant parasite-derived molecules have been described. However, a closer examination of the published data unveiled that tissue-dwelling parasites (usually adults) often release inhibitory factors, possibly in an attempt to reduce the local immune response (Alkarmi and Behbehani, 1989;Culley et al, 2000;Keir et al, 2004;Leid et al, 1987;Lo et al, 1999). Conversely, tissue-migrating larvae usually secrete compounds that promote inflammation (Falcone et al, 2001;Horii et al, 1988;Niwa et al, 1998;Owhashi et al, 1985;Owhashi et al, 1997;Rubio de Kromer et al, 1998;Tanaka et al, 1979;Tanaka and Torisu, 1978).…”