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

Abstract

Lipophosphoglycan (LPG) is the major surface glycoconjugate of metacyclic <i>Leishmania</i> promastigotes and is associated with virulence in various species of this parasite. Here, we generated a LPG-deficient mutant of <i>Leishmania infantum</i>, the foremost etiologic agent of visceral leishmaniasis in Brazil. The <i>L. infantum</i> LPG-deficient mutant (Δ<i>lpg1</i>) was obtained by homologous recombination and complemented via episomal expression of <i>LPG1</i> (Δ<i>lpg1</i> + <i>LPG1</i>). Deletion of <i>LPG1</i> 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<i>lpg1</i> parasites was delayed. Additionally, the deletion of <i>LPG1</i> 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<i>lpg1</i> parasites was significantly reduced at 72 h post-infection. Interestingly, <i>L</i>. <i>infantum</i> LPG-deficient mutants induced a strong NF-κB-dependent activation of the inducible nitric oxide synthase (iNOS) promoter compared to wild type and Δ<i>lpg1</i> + <i>LPG1</i> parasites. In conclusion, the <i>L. infantum</i> Δ<i>lpg1</i> mutant constitutes a powerful tool to investigate the role(s) played by LPG in host cell-parasite interactions.