The different impact of drug-resistant Leishmania on the transcription programs activated in neutrophils.

Drug resistance threatens the effective control of infections, including parasitic diseases such as leishmaniases. Neutrophils are essential players in antimicrobial control, but their role in drug-resistant infections is poorly understood. Here, we evaluated human neutrophil response to clinical parasite strains having distinct natural drug susceptibility. We found that Leishmania antimony drug resistance significantly altered the expression of neutrophil genes, some of them transcribed by specific neutrophil subsets. Infection with drug-resistant parasites increased the expression of detoxification pathways and reduced the production of cytokines. Among these, the chemokine CCL3 was predominantly impacted, which resulted in an impaired ability of neutrophils to attract myeloid cells. Moreover, decreased myeloid recruitment when CCL3 levels are reduced was confirmed by blocking CCL3 in a mouse model. Collectively, these findings reveal that the interplay between naturally drug-resistant parasites and neutrophils modulates the infected skin immune microenvironment, revealing a key role of neutrophils in drug resistance. Overall design: To evaluate the response of human neutrophils to parasite strains having distinct drug susceptibility, we first isolated neutrophils from the peripheral blood of three healthy donors (dA, dB, dC). We infected neutrophils ex vivo with either drug-resistant parasites (R) or drug-susceptible parasites (S), or left the cells uninfected (UN). Neutrophils were harvested for RNA-sequencing after 6h of culture. Differential gene expression analysis was performed between infected conditions vs uninfected, as well as between cells exposed to drug-resistant parasites vs drug-susceptible parasites.