HIV downregulates interferon stimulated genes in primary macrophages.

HIV is able to outpace the innate immune response, including the response mediated by interferon (IFN), to establish a productive infection. However, monocyte derived macrophages (MDMs) may be protected from HIV infection by treatment with type I IFN before virus exposure. The ability of HIV to modulate the type I IFN-mediated innate immune response when it encounters a cell that has already been exposed to IFN was investigated. To investigate the presence of HIV on an established IFN response, MDMs were subjected to four different conditions: (1) IFN-treated only, (2) IFN-treated followed by HIV infection, (3) HIV infected only, and (4) a mock-treated and mock-infected control. Microarray gene expression analysis was performed on a total of 24 samples derived from the 4 conditions assessed at 3 time points (1, 4 and 8 days following treatment/infection) for both IFN-α2 or -ω. Initially, ISGs were identified as those that were upregulated greater than 2-fold by IFN alone (condition 1) at both Days 4 and 8. Then, the IFN-treated condition was compared to the IFN-treated followed by HIV-infection condition in order to identify those ISGs that were downregulated at least 1.5-fold by the presence of HIV at both days. Assuming that it would be counterproductive for HIV infection by itself to induce the expression of ISGs with putative anti-HIV effects, those ISGs that were upregulated greater than 2-fold in the HIV control were removed. Finally, ISGs that passed these filters and were concordant with both IFN-treatments (IFN-α2 and -ω) were identified and corresponded to the following 8 ISGs: AXL receptor tyrosine kinase (AXL), interferon-alpha inducible protein 27 (IFI27), interferon-induced protein 44 (IFI44), interferon-induced protein 44-like (IFI44L), ISG15, OAS1, OAS3 and XIAP associated factor 1 (XAF1). It should be noted that the IFN-α2 and -ω microarray experiments were performed in different batches but batch effects were not corrected since genes were identified by the filtering approach just described within each batch.