Background: HIV-associated neurocognitive disorders (HAND) persist despite the availability of combined antiretroviral therapy (cART) and believed to be at least partially the consequence of mechanisms associated with monocytes. In addition to transporting HIV into the brain, monocytes secrete pro-inflammatory cytokines that lead to neuronal damage. In this study, we analyzed cytokines that were secreted from CD14-selected peripheral blood mononuclear cells (PBMC) from HIV-infected individuals with HAND and normal cognition (NC) at baseline (cART naïve) and after one year on cART to determine which cytokines were associated with HAND.
Methods: The study population consisted of 61 HIV-infected Thais who were enrolled in SEARCH011 (NCT00782808); 28 diagnosed with HAND and 33 with NC at entry. PBMC were collected at baseline and 12 months post cART initiation. CD14+ PBMC were separated by magnetic beads and cultured overnight (median 91.4% purity by flow cytometry). Cytokine secretions were measured from the supernatants captured after 24 hour culture and using a custom 10-plex Milliplex MAP kit detecting fractalkine, IFN-g, IL-2, IL-4, IL-6, IL-8, IL-10, IP-10, MCP-1, and TNF-α. HIV DNA copies were also analyzed from the CD14+ PBMC using a real-time qPCR. Non-parametric Spearman correlation and Wilcoxon rank-sum test were conducted.
Results: Of the cytokines analyzed, only IL-8 and MCP-1 levels were significantly higher in those with HAND in comparison to NC at baseline (p<0.003). HIV DNA levels were directly correlated to IL-8 (r=0.33; p=0.01) and MCP-1 (r=0.39; p=0.003) at baseline but not after one year.
Conclusions: This study demonstrated that individuals with HAND experience continued inflammation and the type of cytokine supports monocyte involvement consistent with their likely role as viral reservoirs that continue to persist despite cART. High levels of IL-8 and MCP-1 continued to be secreted by CD14+ PBMC in individuals with HAND despite initiation of cART. We hypothesize that secretion of these cytokines may play an important role in promoting the continued transmigration of monocytes into the brain that leads to the persistence of HAND despite cART.