Microglia in the central nervous system are infected at early times following human or non- human primate infection with HIV-1. Microglia are infected early in the course of HIV disease in humans, and may represent a source of virus transmission or act as a reservoir of virus. Infection of microglia plays a role in HIV-associated dementia and other forms of HIV-associated neurological disease. Myeloid cells outside the CNS have been recently shown to capture HIV-1 particles through interactions between Siglec-1 and gangliosides on the viral lipid envelope. Particle capture and uptake by Siglec-1 leads to the formation of an intracellular compartment termed the virus-containing compartment (VCC) in monocyte-derived macrophages (MDMs). The VCC is also a potential contributor to a persistent viral reservoir and forms an immune- privileged compartment. The mechanisms of HIV-1 particle capture by microglia within the CNS have not yet been defined, and may differ from that of MDMs. Furthermore, the formation of the VCC has not been studied in microglia. Experiments in Aim 1 will define the mechanism of HIV particle capture and uptake by microglia and compare these to MDMs. The role of Siglec-1 and virion membrane gangliosides will be determined, and the role of inflammatory stimuli on capture and uptake quantified. Aim 2 will characterize the formation of the VCC within infected microglia, and will measure transmission of VCC virus to target cells. The potential of microRNA-124-induced microglial quiescence to prolong the viability of the VCC reservoir will be explored. Efforts to target the VCC will be performed using GM3-coated nanoparticles bearing neutralizing antibodies.

Project Narrative: This project will determine how HIV particles are captured by microglial cells, the predominant myeloid cell of the central nervous system that becomes infected with HIV in infected individuals. The formation of an intracellular compartment harboring virus (the virus-containing compartment) will be defined in HIV-infected microglia, and the ability of microglia to transmit virus to other cells measured following activation by inflammatory stimuli. These studies will help define how microglia harbor, retain, and transmit virus within the central nervous system.