Guanylate-Binding Proteins Promote Host Defense Against Leishmania major by Balancing iNOS/Arg-1 in Myeloid Cells

Cutaneous leishmaniasis (CL) is a debilitating neglected tropical disease characterized by lesions that can range from self-healing to permanent disfigurations. A predominant Th1 response, which stimulates IFN-γ production, is crucial for parasite control during self-healing CL. While IFN-γ primarily activates macrophages to produce nitric oxide via inducible nitric oxide synthase (iNOS) leading to parasite control, IFN-γ also activates other downstream pathways involved in cell autonomous immunity. One such pathway is the activation of guanylate binding proteins (GBPs), a class of interferon inducible GTPases. However, the role of GBPs during CL has been minimally explored. Utilizing RNA-Seq we found that Leishmania major infection leads to the upregulation of several GBPs in C57Bl/6 mice. In vitro studies using GBPChr3 knockout (KO), and C57Bl/6 control mice reveal that bone marrow-derived macrophages (BMDMs) from KO mice exhibit higher parasite burdens following IFN-γ treatment, independent of GBP localization to the parasite. Single-cell RNA-Seq identifies macrophages as the primary expressers of GBPs during L. major infection in vivo. In vivo, GBPChr3 KO mice display increased disease severity and parasite load. GBPChr3 KO macrophages and monocytes show elevated ARG-1 and reduced iNOS expression, indicating a shift toward a parasite-permissive environment that supports parasite growth. These findings highlight a critical role for GBPs in immune-mediated control of CL.