Characterization of cultured microglia that can be infected by HIV-1

Parenchymal microglia are targets of HIV infection. We, as well as others, have used in vitro microglia culture systems to study the tropism and repli cation of HIV. Characterization of perivascular and parenchymal microglia s urface markers in vivo, in vitro, and ex vivo, has led to the understanding that these cell populations are different, and data from both the HIV and SIV models support the hypothesis that they may play different roles in inf ection of the CNS. We determined that human adult parenchymal microglia cul tured from temporal lobe tissue for use in HIV replication studies, were CD 11c(+), CD45(+), CD68(+), CD14(-) when cultured with standard serum/cytokin e-supplemented media. To determine the influence of serum and cytokines on HIV replication in microglia, we designed a new protocol for culturing micr oglia, and compared the results obtained with this protocol with the standa rd approach previously described. Microglia cultured in the presence of a ' feeder' layer of glial cells and in the absence of serum and cytokines expr essed the same surface markers as pure microglia (>95%) cultured in supplem ented media. However, pure microglia cultured in the absence of both serum/ cytokines supplements and other glial cells, did not have characteristic mi croglial morphology and did not support HIV replication to as high a level. Lastly, we determined that unlike monocytes, ex vivo parenchymal microglia were capable of supporting HIV replication.