Leishmania infantum Lipophosphoglycan-Deficient Mutants: A Tool to Study Host Cell-Parasite Interplay.

Lipophosphoglycan (LPG) is the major surface glycoconjugate of metacyclic Leishmania promastigotes and is associated with virulence in various species of this parasite. Here, we generated a LPG-deficient mutant of Leishmania infantum , the foremost etiologic agent of visceral leishmaniasis in Brazil. The L. infantum LPG-deficient mutant (Δ lpg1 ) was obtained by homologous recombination and complemented via episomal expression of LPG1 (Δ lpg1 + LPG1 ). Deletion of LPG1 had no observable effect on parasite morphology or on the presence of subcellular organelles, such as lipid droplets. While both wild-type and add-back parasites reached late phase in axenic cultures, the growth of Δ lpg1 parasites was delayed. Additionally, the deletion of LPG1 impaired the outcome of infection in murine bone marrow-derived macrophages. Although no significant differences were observed in parasite load after 4 h of infection, survival of Δ lpg1 parasites was significantly reduced at 72 h post-infection. Interestingly, L . infantum LPG-deficient mutants induced a strong NF-κB-dependent activation of the inducible nitric oxide synthase (iNOS) promoter compared to wild type and Δ lpg1 + LPG1 parasites. In conclusion, the L. infantum Δ lpg1 mutant constitutes a powerful tool to investigate the role(s) played by LPG in host cell-parasite interactions.