Rapid Sequestration of Leishmania mexicana by Neutrophils Contributes to the Development of Chronic Lesion.

Authors:
Hurrell BP, Schuster S, Grün E, Coutaz M, Williams RA, Held W, Malissen B, Malissen M, Yousefi S, Simon HU5, Müller AJ, Tacchini-Cottier F
In:
Source: PLoS Pathog
Publication Date: (2015)
Issue: 11(5): e1004929
Research Area:
Immunotherapy / Hematology
Parasitology
Platform:
Nucleofector® I/II/2b
Experiment
pGL1313 was linearized by Pme1 and Pacl restriction digestion, purified and used for electroporation using the Amaxa nucleofaector system as previously described [67]. Briefly, 7 x 106 L. mexicana promastigotes at logarithmic growth phase were harvested and resuspended in 100 µl Human T Cell Nucleofector Solution. The transfected cells were cloned by serial dilution in presence of 50 µg/ml of hygromycin B (Sigma). Clones resistant to the antibiotic were obtained and Luciferase expression validated by the determination of luciferase activity. Lonza Summary: Leismania Mexicana causes chronic skin lesions in humans and the authors used a mouse model to study this disease. Upon infecting C57BL/6 mice, the authors found that neutrophils are recruited which ingest the parasite but do not kill them. As a result, the parasites continue to live and cause skin lesions. Therefore, what should be a beneficial immune response to the host benefits the parasite. The authors demonstrate that controlling neutrophil recruitment in the early stages of infection is critical in eliminating the illness.
Abstract
The protozoan Leishmania mexicana parasite causes chronic non-healing cutaneous lesions in humans and mice with poor parasite control. The mechanisms preventing the development of a protective immune response against this parasite are unclear. Here we provide data demonstrating that parasite sequestration by neutrophils is responsible for disease progression in mice. Within hours of infection L. mexicana induced the local recruitment of neutrophils, which ingested parasites and formed extracellular traps without markedly impairing parasite survival. We further showed that the L. mexicana-induced recruitment of neutrophils impaired the early recruitment of dendritic cells at the site of infection as observed by intravital 2-photon microscopy and flow cytometry analysis. Indeed, infection of neutropenic Genista mice and of mice depleted of neutrophils at the onset of infection demonstrated a prominent role for neutrophils in this process. Furthermore, an increase in monocyte-derived dendritic cells was also observed in draining lymph nodes of neutropenic mice, correlating with subsequent increased frequency of IFN?-secreting T helper cells, and better parasite control leading ultimately to complete healing of the lesion. Altogether, these findings show that L. mexicana exploits neutrophils to block the induction of a protective immune response and impairs the control of lesion development. Our data thus demonstrate an unanticipated negative role for these innate immune cells in host defense, suggesting that in certain forms of cutaneous leishmaniasis, regulating neutrophil recruitment could be a strategy to promote lesion healing.