Background/Objectives: Restored CD4 absolute counts (CD4AC) and CD4/CD8 ratio in the setting of continuous antiretroviral treatment (ART) do not exclude a low-level immune activation associated with HIV reservoirs, microbial translocation, or the side effects of ART itself, which accelerates the aging of people living with HIV (PLHIV). To delineate biomarkers of incomplete immune restoration in PLHIV on successful ART, we evaluated T-lymphocyte mitochondrial parameters in relation to phenotypic markers of immune exhaustion and senescence. Methods: PLHIV with sustained viral suppression, CD4AC >500 and CD4/CD8 ratio >0.9 on ART (n = 39) were compared to age-matched ART-naïve donors (n = 27) and HIV(–) healthy controls (HC, n = 35). CD4 and CD8 differentiation and effector subsets (CCR7/CD45RA and CD27/CD28), activation, exhaustion, and senescence markers (CD38, CD39 Treg, CD57, TIGIT, and PD-1) were determined by flow cytometry. Mitochondrial mass (MM) and membrane potential (MMP) of CD8 and CD4 T cells were evaluated with MitoTracker Green and Red flow cytometry dyes. Results: ART+PLHIV differed from HC by increased CD4 TEMRA (5.3 (2.1–8.8) vs. 3.2 (1.6–4.4), p < 0.05), persistent TIGIT+CD57–CD27+CD28– CD8+ subset (53.9 (45.5–68.9) vs. 40.1 (26.7–58.5), p < 0.05), and expanding preapoptotic TIGIT–CD57+CD8+ effectors (9.2 (4.3–21.8) vs. 3.0 (1.5–7.3), p < 0.01) in correlation with increased CD8+ MMP (2527 (1675–4080) vs.1477 (1280–1691), p < 0.01). These aberrations were independent of age, time to ART, or ART duration, and were combined with increasing CD4 T cell MMP and MM. Conclusions: In spite of recovered CD4AC and CD4/CD8 ratio, the increased CD8+ MMP, combined with elevated markers of exhaustion and senescence in ART+PLHIV, signals a malfunction of the CD8 effector pool that may compromise viral reservoir latency.

Background/Objectives: Restored CD4 absolute counts (CD4AC) and CD4/CD8 ratio in the settings of continuous antiretroviral treatment (ART) do not exclude a low-level immune activation associated with HIV reservoirs, microbial translocation, or the side-effects of ART itself, that accelerates ageing of people living with HIV (PLHIV). To delineate biomarkers of incomplete immune restoration in PLHIV on successful ART, we evaluated T-lymphocyte mitochondrial parameters in relation to phenotypic markers of immune exhaustion and senescence. Methods: PLHIV with sustained viral supression, CD4AC >500 and CD4/CD8 ratio >0.9 on ART (n=39) were compared to age-matched ART-naïve donors (n=27) and HIV(-) healthy controls (HC, n=35). CD4 and CD8 differentiation and effector subsets (CCR7/CD45RA and CD27/CD28), activation, exhaustion, and senescence markers (CD38, CD39 Treg, CD57, TIGIT, PD-1) were determined by flow cytometry. Mitochondrial mass (MM) and membrane potential (MMP) of CD8 and CD4 T cells were evaluated with MitoTracker Green and Red flow cytometry dyes. Results: ART+PLHIV differed from HC by increased CD4 TEMRA (5.3 (2.1-8.8) vs. 3.2 (1.6-4.4), p<0.05), persistent TIGIT+CD57-CD27+CD28- CD8+ subset (53.9 (45.5-68.9) vs. 40.1 (26.7-58.5), p<0.05), and expanding preapoptotic TIGIT-CD57+CD8+ effectors (9.2 (4.3-21.8) vs. 3.0 (1.5-7.3), p<0.01) in correlation with increased CD8+ MMP (2527 (1675-4080) vs.1477 (1280-1691), p<0.01). These aberrations were independent of age, time to ART, ART duration, and were combined with an increasing CD4 T cell MMP and MM. Conclusions: In spite of recovered CD4AC and CD4/CD8, the increased CD8+ MMP combined with elevated markers of exhaustion and senescence in ART+PLHIV, signals a malfunction of the CD8 effector pool, that may compromise viral reservoirs latency.

The advances in antiretroviral therapy (ART) bring forth an ever-growing percentage of aging people living with HIV (PLHIV) with successful immune restoration (SIR) but increased comorbidities and reduced quality of life. The current criteria for SIR, CD4 absolute count (AC) >500 cells/µL, are proving not to be sufficiently informative enough for preventing or monitoring these unwelcome changes. Messenger RNA (mRNA) of genes, such as CXCL8, IL-6, and CSF-2, that have shown relations with HIV/HIV-associated comorbidities could represent early indicators of increase in viral load and/or pathological changes leading development of comorbidities. Our results display an underexpression of CXCL8 and IL-6 in ART+ PLHIV with CD4 AC >1,000, but not with CD4 AC 1,000 compared to ART+ CD4 AC 500.

Background: People living with HIV (PLHIV) who are capable of long-term viral suppression in the absence of antiretroviral therapy (ART) are defined as elite controllers (EC). Although there is evidence of phenotypic and functional alterations of T-lymphocytes in EC, neither the mechanisms of viral control, nor the necessity and timing of ART in this particular population have been elucidated. Case presentation: We report the case of untreated HIV+ patient with undetectable viral load (VL), and preserved CD4 T cell absolute count (AC) and CD4/CD8 ratio since diagnosis in 2018. The detailed phenotype of EC CD4 and CD8 T cell pools including differentiation, effector, activation, immunosenescence and exhaustion markers was distinct from sex- and age-matched ART+PLHIV with immune recovery, and close to HIV(-) healthy controls (HC), except for a temporary increase of CD57+ CD8 T cells in 2023. The only changing biomarkers were T cell mitochondrial mass (MM), slightly increased at the level of CD8 T cells in 2023, and drastically increased in both CD4 and CD8 T in 2025, together with the mitochondrial membrane potential (MMP), as compared to ART+PLHIV and HIV (-) HC. Conclusions: CD4 and CD8 T cells of EC experience intensive oxidative stress and functional burden, possibly linked to the continuous effective HIV-specific immune response. CD4 and CD8 T cell MM may serve as a monitoring marker preceding the irreversible changes of immune profile and loss of viral control, and possibly predict the time for start of ART.