Higher circulating intermediate monocytes are associated with cognitive function in women with HIV

Abstract

BACKGROUNDIdentifying a quantitative biomarker of neuropsychiatric dysfunction in people with HIV (PWH) remains a significant challenge in the neuroHIV field. The strongest evidence to date implicates the role of monocytes in central nervous system (CNS) dysfunction in HIV, yet no study has examined monocyte subsets in blood as a correlate and/or predictor of neuropsychiatric function in virally suppressed PWH.METHODSIn 2 independent cohorts of virologically suppressed women with HIV (vsWWH; n = 25 and n = 18), whole blood samples were obtained either in conjunction with neuropsychiatric assessments (neuropsychological [NP] test battery, self-report depression and stress-related symptom questionnaires) or 1 year prior to assessments. Immune cell subsets were assessed by flow cytometry.RESULTSA higher proportion of intermediate monocytes (CD14+CD16+) was associated with lower global NP function when assessing monocytes concurrently and approximately 1 year before (predictive) NP testing. The same pattern was seen for executive function (mental flexibility) and processing speed. Conversely, there were no associations with monocyte subsets and depression or stress-related symptoms. Additionally, we found that a higher proportion of classical monocytes was associated with better cognition.CONCLUSIONAlthough it is widely accepted that lentiviral infection of the CNS targets cells of monocyte-macrophage-microglial lineage and is associated with an increase in intermediate monocytes in the blood and monocyte migration into the brain, the percentage of intermediate monocytes in blood of vsWWH has not been associated with neuropsychiatric outcomes. Our findings provide evidence for a new, easily measured, blood-based cognitive biomarker in vsWWH.FUNDINGR01-MH113512, R01-MH113512-S, P30-AI094189, R01-MH112391, R01-AI127142, R00-DA044838, U01-AI35004, and P30-MH075673.

Keywords: AIDS/HIV; Immunology; Monocytes; Neurological disorders.

Figure 1. Monocyte subset and MNC calculation for Baltimore cohort.

(A–F) A representative FACS gating scheme. (A) Doublets were excluded using FSC-A and FSC-H measurements, and (B) debris was gated out by drawing a gate on cell-sized events using FSC-A and SSC-A. (C) TLR2⁺ cells were gated as monocytes, and nongranulocyte TLR2^– cells were gated as lymphocytes. (D) TLR2^– lymphocytes were gated as CD3⁺ T cells or CD159a⁺ NK cells. (E) CD3⁺ cells were then gated as CD4⁺ or CD8⁺ T cells. (F) TLR2⁺ monocytes were gated based on the expression of CD14 and CD16 and classified as classical (CD14⁺CD16^–), intermediate (CD14⁺CD16⁺), or nonclassical (CD14^–CD16⁺) monocytes. (G) MNCs were counted in the whole blood sample, by summing both TLR2⁺ monocyte gating, which separates monocytes from granulocytes, and TLR2^– lymphocytes as smaller, agranular lymphocytes. Both were gated after debris and doublet removal. TLR2⁺ monocytes and CD4⁺ and CD8⁺ T cell populations were expressed as a percentage of MNCs. Monocyte subsets were expressed as either percentage of TLR2⁺ or percentage of MNCs.

Figure 2. A higher percentage of TLR2⁺ MNCs is associated with higher cognitive function.

Percentage of TLR2⁺ MNCs was measured concurrently with cognitive function in WWH (n = 25) living in Baltimore, Maryland, USA; Stroop-3 not shown (rs = 0.53, P < 0.001). Spearman’s Rho (rs) was used to examine the associations.

Figure 3. TLR2 numbers and associations with cognitive function are driven by an increase in classical monocytes, not maturation into other subsets.

(A) Associations (using rs) between percentage MNCs TLR2⁺ and percentage MNC monocyte subsets in WWH living in Baltimore, Maryland, USA (n = 25). (B) Statistically significant associations (using rs) between cognitive function in WWH living in Baltimore, Maryland, USA (n = 25), and concurrent measurements of the percentage MNC classical monocyte subset; letter fluency (rs = 0.43, P < 0.05), animal fluency (rs = 0.49, P < 0.05), and Stroop-3 (rs = 0.47, P < 0.05) not shown. Classical (CD14⁺CD16^–); intermediate (CD14⁺CD16⁺); nonclassical (CD14^–CD16⁺).

Figure 4. The percentage of intermediate monocyte subset negatively correlates with concurrent and predictive cognitive function.

(A) Higher numbers of intermediate monocytes are associated (using rs) with lower cognitive function measured concurrently in WWH (n = 25) living in Baltimore, Maryland, USA. Grooved Pegboard dominant hand not shown (rs = –0.44, P < 0.05). (B) Higher numbers of intermediate monocytes are associated (using rs) with lower executive function and processing speed when cognition was assessed approximately 1 year following monocyte assessment (median = 1.14; IQR 0.58) in WWH living in Bronx, New York, New York, USA (n = 18).