Interactions between Neutrophils and <b><i>Leishmania braziliensis</i></b> Amastigotes Facilitate Cell Activation and Parasite Clearance

<i>Leishmania braziliensis</i> and <i>Leishmania amazonensis</i> are both causative agents of cutaneous leishmaniasis in South America. However, patient prognosis and the host immune response differ considerably depending on the infecting parasite species. The mechanisms underlying these differences appear to be multifactorial, with both host and parasite components contributing to disease outcome. As neutrophils are a prominent component of the inflammatory infiltrate in chronic cutaneous, diffuse cutaneous and mucocutaneous lesions, we examined neutrophil activation and microbicidal activity against amastigotes of <i>L. amazonensis </i>and <i>L. braziliensis</i>. We found that murine neutrophils internalized <i>L. braziliensis </i>amastigotes with greater efficiency than did <i>L. amazonensis </i>amastigotes. Additionally, <i>L. braziliensis </i>infection was a potent trigger for neutrophil activation, oxidative burst, degranulation and the production of interleukin (IL)-22 and IL-10, while <i>L. amazonensis </i>amastigotes poorly induced these responses. Finally, neutrophils were able to kill <i>L. braziliensis </i>amastigotes, especially when cells were activated with phorbol myristate acetate. <i>L. amazonensis</i> amastigotes, however, were highly resistant to neutrophil microbicidal mechanisms. This study reveals, for the first time, differential neutrophil responsiveness to distinct species of <i>Leishmania</i> amastigotes and highlights the complexity of neutrophil-amastigote interactions during chronic leishmaniasis.

Duke Scholars

Author Eric D. Carlsen Pathology