Cell apoptosis induced by hookworm antigens: a strategy of immunomodulation.

While several mechanisms of immunoregulation have been demonstrated for hookworm and other neglected tropical infections, the influence of apoptosis in the immunomodulation of hookworm infection is still poorly understood. In this study, we demonstrate the cytotoxic and pro-apoptotic activity of hookworm antigens in Jurkat T cells, mesenteric lymph nodes lymphocytes of healthy and hookworm-infected hamsters and during human natural infection. Our results showed that in vitrostimulation of Jurkat T cells with antigens induces a significant decrease of cell viability leading to a relevant increase of apoptotic cells. Similar results were also observed in experimental conditions, for both healthy and hookworm-infected hamsters` lymphocytes. Flow cytometric analysis demonstrated that hookworm-infected patients presented a significant increase of CD4+, CD8+, and CD19+lymphocytes in early and/or late apoptosis when compared with non-infected individuals. The downmodulation of TNF receptors, as well as the up-regulation of the pro-apoptotic genes belonging to the BCL-2 and P53 families, suggest that hookworm antigens induced apoptosis by an intrinsic mitochondrial pathway, acting as a sophisticated strategy to safeguard parasite long-term survival in their hosts.

Induction of CD4(+)CD25(+)FOXP3(+) regulatory T cells during human hookworm infection modulates antigen-mediated lymphocyte proliferation.

Hookworm infection is considered one of the most important poverty-promoting neglected tropical diseases, infecting 576 to 740 million people worldwide, especially in the tropics and subtropics. These blood-feeding nematodes have a remarkable ability to downmodulate the host immune response, protecting themselves from elimination and minimizing severe host pathology. While several mechanisms may be involved in the immunomodulation by parasitic infection, experimental evidences have pointed toward the possible involvement of regulatory T cells (Tregs) in downregulating effector T-cell responses upon chronic infection. However, the role of Tregs cells in human hookworm infection is still poorly understood and has not been addressed yet. In the current study we observed an augmentation of circulating CD4(+)CD25(+)FOXP3(+) regulatory T cells in hookworm-infected individuals compared with healthy non-infected donors. We have also demonstrated that infected individuals present higher levels of circulating Treg cells expressing CTLA-4, GITR, IL-10, TGF-ß and IL-17. Moreover, we showed that hookworm crude antigen stimulation reduces the number of CD4(+)CD25(+)FOXP3(+) T regulatory cells co-expressing IL-17 in infected individuals. Finally, PBMCs from infected individuals pulsed with excreted/secreted products or hookworm crude antigens presented an impaired cellular proliferation, which was partially augmented by the depletion of Treg cells. Our results suggest that Treg cells may play an important role in hookworm-induced immunosuppression, contributing to the longevity of hookworm survival in infected people.

Hookworm products ameliorate dextran sodium sulfate-induced colitis in BALB/c mice.

BACKGROUND: Several lines of evidence have shown that helminthiasis can significantly reduce disease severity in animal models of intestinal inflammation, airway inflammation/hyperreactivity, diabetes, and multiple sclerosis. Identification and characterization of helminth-derived immunomodulatory molecules that contribute to anticolitis effects could lead to new therapeutic approaches in inflammatory bowel diseases (IBDs) without the need for helminth infection. We evaluated the therapeutic potential of adult human hookworm, Ancylostoma ceylanicum, crude (Aw) and excreted/secreted (ES) products on dextran sulfate sodium (DSS)-induced colitis in BALB/c mice. METHODS: Colitis was induced by 5% DSS oral administration for 7 days. Clinical disease severity was monitored daily during concomitant intraperitoneal treatment with helminth-derived products. Additionally, several pathways of immunological modulation induced by A. ceylanicum products (MPO, EPO, Th1, Th2, and Th17 cytokine responses) in the inflamed intestinal microenvironment were assessed. Finally, the histopathological profile of the colon was characterized. RESULTS: Hookworm products are able to modulate the potent proinflammatory response induced by DSS, mainly through the downregulation of Th1 and Th17 cytokines. These proteins also reduce clinical and colonic microscopic inflammation scores as well as EPO and MPO activity. CONCLUSIONS: Ancylostoma ceylanicum Aw and ES mediators have an important therapeutic potential in experimental colitis in mice, which may provide a more socially acceptable form of therapy for patients with IBDs as opposed to using living worms. Our results support the urgency of further isolation and recombinant expression of active hookworm products responsible for the beneficial effects on colitis.