The purpose of this notice of funding opportunity (NOFO) is to support research towards identifying and characterizing neuroimmune networks, communication pathways, and targets that reside within neuroimmune axes, in the context of HIV and substance use. This NOFO will also support research on the discovery of novel modulatory probes/tools that can advance our knowledge of the regulatory mechanisms by which neuroimmune interactions contribute to HIV and substance use disorder comorbidity.: