Macrophages show unprecedented anti-HIV activity in HIV-infected iHMD-NSG mice

Very little is known about the role of macrophages as immune mediators during natural HIV infection. Humanized mice are a highly valuable in vivo model to study HIV pathogenesis. Still, the presence of murine mononuclear phagocytes in these models represents a significant limitation for the study of their human counterpart. Therefore, we generated a novel humanized mouse model for the selective depletion of human myeloid cells at a time point of our choosing. These inducible human myeloid cell depletion (iHMD) mice showed specific human myeloid cell depletion with no adverse events for the animals. We used this model to demonstrate that human mononuclear phagocytes restrict HIV replication in vivo by secreting antiviral cytokines and chemokines. These in vivo data were validated by a co-culture assay, showing soluble factors are at the basics of macrophage-mediated restriction of HIV. Transcriptomic data confirmed macrophages restrict HIV replication via upregulation of antiviral cytokines and chemokines. RNA sequencing CD4+ T-cells showed cellular activation, up-regulation of HIV restriction factors and the downregulation of DNA transcription and RNA translation in the presence of macrophages. This work describes a novel role of macrophages as effector cells acting against HIV replication and disease progression.