Despite being on effective antiretroviral therapy (ART), many HIV-infected individuals have impaired reconstitution of CD4 T cells. This is partly due to the fibrosis of lymphoid tissues (LT), which impedes signals important for T cell homeostasis. Macrophages (Mφ) are key regulators of tissue remodeling and fibrosis, though their involvement in LT fibrosis during chronic HIV has yet to be defined.
Inguinal lymph node (LN) excisions were performed by a board-certified surgeon on 6 virally-suppressed HIV-infected participants on ART and 4 HIV-uninfected participants recruited at the University Clinics at Kaka’ako at the John A. Burns School of Medicine. Immediately after excision, LN was divided into portions used for quantification of CD206+, CD163+, and CD169+ LN Mφ populations by multi-parametric flow cytometry and quantification of collagen fibers and CD4 T cells by IHC. Soluble markers of Mφ activation, fibrosis, and immune checkpoints were measured in cryopreserved plasma using ELISAs and Luminex. Statistical analyses performed were T-tests and Pearson correlations.
HIV-infected participants were older than those uninfected (median age: 59 years vs. 51; p=0.036). All participants were male and Caucasian, with no significant differences between groups. All HIV-infected participants were virally suppressed with a median current CD4 count of 538 cells/μl, nadir CD4 count of 65 cells/μl, and CD4 CD8 T cell ratio of 0.66. HIV-infected participants had higher frequencies of CD206+, CD169+, and CD163+ LN Mφ as compared to HIV-uninfected (CD206+: 0.27 vs. 0.13, p=0.087; CD169+: 0.56 vs. 0.31, p=0.136; CD163+: 0.047 vs. 0.017, p=0.286). CD163+ LN Mφ correlated with lower CD4 counts in blood (r=-0.827, p=0.042) and LN (r=-0.553, p=0.097), as well as lower CD4 CD8 T cell ratios (r=-0.833, p=0.039). CD163+ LN Mφ correlated with more collagen fibrils in LN (r=0.694, p=0.026) and higher plasma levels of fibrosis biomarkers: TGF-β1, r=805, p=0.005; TSP-1, r=0.740, p=0.014; and CICP, r=0.633, p=0.049. CD163+ LN Mφ correlated with higher plasma levels of soluble immune checkpoint receptors (sCTLA-4, r=0.767, p=0.010; sPD-1, r=0.713, p=0.021) and markers of Mφ activation (sCD163, r=0.867, p=0.001; Neopterin, r=0.736, p=0.015).
CD163+ LN Mφ are elevated in ART-treated chronic HIV infection and correlates with limited CD4 T cell reconstitution in blood and LN. CD163+ LN Mφ may play a role in the pathogenesis of LT fibrosis and warrants further study.