Acute HIV Infection and ART Response: Insights into T Cell Subsets, Activation, Exhaustion, and Blood and GALT HIV Reservoir

Abstract

Investigating immunological and viral reservoir dynamics in blood and GALT during acute HIV phase advances understanding of HIV persistence. Dynamics of T cells and HIV reservoirs immediately after early ART require further investigation. We evaluated the ART impact at 12 (M12) and 24 months (M24) on immunological, virological and reservoir markers of 24 participants starting ART at Fiebig ≤ V (Baseline = D0) in a Brazilian cohort. We measured the frequency of T cell activation, exhaustion, memory subsets, Th17 and pTfh cells by flow cytometry and quantified total HIV DNA by qPCR in PBMC and GALT. Most participants were cisgender MSM (95.9%), with a median age of 27 years (IQR 25-36). At enrollment (D0), four participants used triple ART as PEP, and two were under oral PrEP and they exhibited higher CD4/CD8 ratios. Higher CD4/CD8 ratios were also observed in participants classified as Fiebig I to III. A total of 92% achieved viral suppression at M12 and 96% at M24. CD4 counts rose from 646 to 861 cells/mm³, and the CD4/CD8 ratio improved from 0.76 to 1.24 (p < 0.01). HIV DNA in PBMCs decreased 4-fold by M12 and 61-fold by M24, with 50% of participants reaching undetectable levels by M24 (p < 0.01). In GALT, undetectable HIV DNA increased from 27% at D0 to 75% at M12. HIV DNA in PBMCs and GALT correlated with plasma VL, while the CD4/CD8 ratio was inversely linked to PBMC reservoirs (rho = -0.66; p < 0.05). Early ART reduced activated CD8⁺ T cells (p < 0.05) but had minimal effects on CD4⁺ T cells or exhaustion markers. By M24, CD8⁺ TCM increased, and CD8⁺ TEF decreased (p < 0.01), while Th17 and pTfh levels remained stable. Early ART led to viral suppression and immune restoration, and influenced reservoir dynamics. The CD4/CD8 ratio was shown to be a key marker of early treatment success. Since a quarter of the participants were identified while initiating PrEP/PEP, it is important to consider the acute phase window according to vulnerability. Recent PEP/PrEP use often excludes participants from clinical trials on bNAbs and therapeutic vaccines targeting viral reservoirs during the acute phase of HIV. Since these are the populations that may benefit from these strategies, larger studies including those people are needed.

Keywords: CD4/CD8 ratio; Fiebig; GALT; HIV; activation; acute infection; cure; early treatment; exhaustion.

Figure 1

Flowchart of the study. D0: Day 0 or pre-ART visit; M12: month 12; M24: month 24; GALT: gut-associated lymphoid tissue; PBMC: peripheral blood mononuclear cells.

Figure 2

Longitudinal analysis of viral load and T cell count. (a) HIV viral load, (b) CD4 T Cell Count, and (c) CD4/CD8 Ratio at D0, M12, and M24. Fiebig stages are identified by colors as follows: red (I), blue (II), green (III), purple (IV), and orange (V). Participants who began ART prescribed as post-exposure prophylaxis (PEP) before the diagnosis are represented by the diamond symbol, while those identified while seeking pre-exposure prophylaxis (PrEP) at the time of diagnosis are represented by triangle symbols. For black error bars, central dots represent mean marginal estimates and parallel lines indicate the upper and lower 95% confidence interval limits. Gray boxplots represent the boxplot of the sampled distribution. (d) Correlation analysis of CD4/CD8 ratio and HIV RNA at D0. p-values were generated from mixed linear regression analysis and correlations were analyzed using Pearson’s correlation test. ** indicates p < 0.01.

Figure 3

Longitudinal analysis (a) Peripheral Blood Mononuclear Cells (PBMCs) and (b) Gut-Associated Lymphoid Tissue (GALT) harboring total HIV DNA at D0, M12, and M24 Fiebig stages are identified by colors as follows: red (I), blue (II), green (III), purple (IV), and orange (V). Participants who began ART prescribed as post-exposure prophylaxis (PEP) before the diagnosis are represented by the diamond symbol, while those identified while seeking pre-exposure prophylaxis (PrEP) at the time of diagnosis are represented by triangle symbols. For black error bars, central dots represent mean marginal estimates and parallel lines indicate the upper and lower 95% confidence interval limits. Gray boxplots represent the boxplot of the sampled distribution. The p-values were generated from mixed linear regression analysis. * indicates p < 0.05; ** indicates p < 0.01.

Figure 4

Longitudinal analysis T cell Activation. (a) CD4⁺ HLA-DR⁺ CD38⁺ and (b) CD8⁺ HLA-DR⁺ CD38⁺ T cells. Fiebig stages are identified by colors as follows: red (I), blue (II), green (III), purple (IV), and orange (V). Participants who began ART prescribed as post-exposure prophylaxis (PEP) before the diagnosis are represented by the diamond symbol, while those identified while seeking pre-exposure prophylaxis (PrEP) at the time of diagnosis are represented by triangle symbol. For black error bars, central dots represent mean marginal estimates and parallel lines indicate the upper and lower 95% confidence interval limits. Gray boxplots represent the boxplot of the sampled distribution. p-values were generated from mixed linear regression analysis and correlations were analyzed using Pearson’s correlation test. ** indicates p < 0.01.

Figure 5

Longitudinal analysis of T cell exhaustion. (a) CD4⁺ PD-1⁺ T cells and (b) CD8⁺ PD-1⁺ T cells. (c) Correlation between expression of PD-1 at M24 and HIV reservoir in PBMC at baseline. Fiebig stages are identified by colors as follows: red (I), blue (II), green (III), purple (IV), and orange (V). Participants who began ART prescribed as post-exposure prophylaxis (PEP) before the diagnosis are represented by the diamond symbol, while those identified while seeking pre-exposure prophylaxis (PrEP) at the time of diagnosis are represented by triangle symbols. For black error bars, central dots represent mean marginal estimates and parallel lines indicate the upper and lower 95% confidence interval limits. Gray boxplots represent the boxplot of the sampled distribution. p-values were generated from mixed linear regression analysis and correlations were analyzed using Pearson’s correlation test.

Figure 6

Longitudinal Analysis of the T cell substes. (a) CD4⁺ and (b) CD8⁺ T cell subsets. TN: Naive T cells, TCM: Central Memory T cells, TEM: Effector Memory T cells and TEF: Effector T cells. Fiebig stages are identified by colors as follows: red (I), blue (II), green (III), purple (IV), and orange (V). Participants who began ART prescribed as post-exposure prophylaxis (PEP) before the diagnosis are represented by the diamond symbol, while those identified while seeking pre-exposure prophylaxis (PrEP) at the time of diagnosis are represented by triangle symbols. For black error bars, central dots represent mean marginal estimates and parallel lines indicate the upper and lower 95% confidence interval limits. Gray boxplots represent the boxplot of the sampled distribution. p-values were derived from mixed linear regression analysis. * indicates p < 0.05; ** indicates p < 0.01.