Background: The replication-competent HIV reservoir in circulating monocytes and how it relates to neurocognitive impairment in ART-suppressed chronic HIV infection are not understood.
Methods: Cryopreserved peripheral blood mononuclear cells collected at entry from ART-suppressed chronic HIV-infected individuals, whom were enrolled in a cross-sectional neuroHIV MRI study and had available age- and education-adjusted neuropsychological global and domain-specific z-scores, were cell-sorted using multi-parametric flow-cytometry for total monocytes and CD4 T cells. Subsequent flow-cytometry analyses confirmed 100% purity of sorted cell populations. Using a novel modified TZM-bl Assay (TZA), termed MoCo-TZA, frequencies of cells producing replication-competent HIV (IUPM) were calculated in monocytes and CD4 T cells. Total p24 associated with replication-competent HIV produced by monocytes and CD4 T cells were quantified using a relative light unit to replication-competent HIV-associated p24 standard curve in the MoCo-TZA. Ratios of total replication-competent HIV-associated p24 and IUPMs, termed infectious potential, were calculated for monocytes and CD4 T cells. Cognitive impairment was defined as a global z-score < -0.5 or a z-score < -0.5 in one cognitive domain known to be affected by HIV. Mann-Whitney and Spearman''s tests assessed group comparisons and correlations.
Results: All HIV-infected participants in cognitively-impaired (n=7) and normal (n=9) groups were male, on ART>3 months, and virally-suppressed (< 20 RNA copies/mL). There were no significant differences in median age (58vs.54), education years (14vs.15), and nadir and current CD4 T cell counts (139 cells/ul vs.69 cells/ul; 568 cells/ul vs.470 cells/ul). IUPMs in monocytes were detectable in 11 of 16 participants (median IUPM=1.32; range:0-16.01). IUPMs in CD4 T cells were detectable in 13 of 16 participants (median IUPM=7.22; range:0-52.57) and were significantly higher as compared to monocytes (p=0.004). Median infectious potential was slightly higher in monocytes as compared to CD4 T cells (0.443vs.0.104;p=0.271). Cognitively-impaired participants had significantly higher IUPMs in monocytes (4.43vs.0.31;p=0.015) and lower IUPMs in CD4 T cells (5.81vs.20.32;p=0.071) as compared to cognitively-normal participants. Infectious potentials between cognitive groups were similar for both cellular compartments. Higher monocyte-CD4 T cell IUPM ratios correlated with lower executive function (p=0.009), working memory (p=0.159), and global performance (p=0.084).
Conclusions: Despite ART-suppression, circulating monocytes capable of producing replication-competent HIV may contribute to neurocognitive impairment.