Reduction in terminally differentiated T cells in virologically controlled HIV-infected aging patients on long-term antiretroviral therapy

Abstract

Several studies have shown an increased accumulation of terminally differentiated T cells during HIV infection, suggestive of exhaustion/senescence, causing dysregulation of T cell homeostasis and function and rapid HIV disease progression. We have investigated whether long-term antiretroviral therapy (ART), which controls viremia and restores CD4 T cell counts, is correlated with reduction in terminally differentiated T cells, improved ratios of naïve to memory and function of T cells in 100 virologically controlled HIV-infected patients. We show that while the median frequencies of terminally differentiated CD4+ and CD8+ T cells (CD28-, CD27-, CD57+ and CD28-CD57+), were higher in the virologically controlled HIV-infected patients' cohort compared with uninfected individuals' cohort, the frequencies of these cells significantly decreased with increasing CD4 T cell counts in HIV-infected patients. Although, the naïve CD4+ and CD8+ T cells were lower in HIV patients' cohort than uninfected cohort, there was a significant increase in both naïve CD4+ and CD8+ T cells with increasing CD4 T cell counts in HIV-infected patients. The underlying mechanism behind this increased naïve CD4+ and CD8+ T cells in HIV-infected patients was due to an increase in recent thymic emigrants, CD4+CD31+, as compared to CD4+CD31-. The CD4+ T cells of HIV-infected patients produced cytokines, including IL-2, IL-10 and IFN-γ comparable to uninfected individuals. In conclusion, virologically controlled HIV-infected patients on long-term ART show a significant reduction in terminally differentiated T cells, suggestive of decreased exhaustion/senescence, and improvement in the ratios of naïve to memory and function of T cells.

Fig 1. Distribution of CD4⁺ and CD8⁺ T cell subsets in HIV-infected patients with controlled viremia on long-term antiretroviral therapy (ART).

(A) Lymphocyte distribution measured as frequencies of CD4⁺, CD8⁺, and non-T cell populations in HIV-infected patients (HIV+) and uninfected controls (UNC). (B) Frequencies of CD8⁺ T cells by increasing CD4 T cell counts in HIV+ and UNC. Frequencies of CD4⁺ (C) and CD8⁺ (D) T cell subsets defined as naïve (N, CD28^IntCD95^LoCD45RA^HiCCR7^Hi), central memory (CM, CD28^HiCD95^HiCD45RA^LoCCR7^Hi) and effector memory (EM, CD28^LoCD95^HiCCR7^Lo). (n = 100 HIV+, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Fig 2. Distribution of CD4⁺ and CD8⁺ T cell phenotypes based on expression of CD28, CD27 and CD57 in HIV-infected patients with controlled viremia on ART.

Frequencies of CD28⁺/CD28^- cells (A), CD27⁺/CD27^- cells (B), CD57⁺/CD57^- cells (C), within the CD4⁺ T cell population in HIV+ and UNC. Frequencies of CD28⁺/CD28^- cells (D), CD27⁺/CD27^- cells (E), CD57⁺/CD57^- cells (F) within the CD8⁺ T cell population in HIV+ and UNC. (n = 100 HIV⁺, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Fig 3. Reduced frequencies of CD28^-, CD27^- and CD57⁺ T cells in HIV-infected patients with controlled viremia on ART with increasing CD4 T cell counts.

Frequencies of CD28⁺/CD28^- cells (A), CD27⁺/CD27^- cells (B), CD57⁺/CD57^- cells (C) within the CD4⁺ T cell population plotted with increasing CD4 T cell counts in HIV+ and UNC. Frequencies of CD28⁺/CD28^- cells (D), CD27⁺/CD27^- cells (E), CD57⁺/CD57^- cells (F) within the CD8⁺ T cell population plotted with increasing CD4 T cell counts in HIV+ and UNC. (n = 100 HIV⁺, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Fig 4. Characterization of early, intermediate, and late stage terminally differentiated CD4⁺ T cell subsets in HIV-infected patients with controlled viremia on ART.

Frequencies of CD4⁺ T cell subsets defined by expression patterns of CD28 and CD57 in HIV+ patients and uninfected individuals (A). Frequencies of (B) early stage (CD28⁺CD57^-), (C) intermediate stage (CD28^-CD57^-), and (D) late stage (CD28^-CD57⁺) cells within the CD4⁺ T cell population plotted with increasing CD4 T cell counts in HIV+ and UNC. (n = 100 HIV⁺, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Fig 5. Characterization of early, intermediate, and late stage terminally differentiated CD8⁺ T cell subsets in HIV-infected patients with controlled viremia on ART.

Frequencies of CD8⁺ T cell subsets defined by expression patterns of CD28 and CD57 in HIV+ and UNC (A). Frequencies of early stage (CD28⁺CD57^-) (B), intermediate stage (CD28^-CD57^-) (C), and late stage (CD28^-CD57⁺) (D) cells within the CD8⁺ T cell population plotted with increasing CD4 T cell counts in HIV+ and UNC. (n = 100 HIV⁺, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Fig 6. Recovery of CD4⁺ and CD8⁺ naïve to memory T cell ratios in HIV-infected patients with controlled viremia on ART.

Frequencies of naïve (N, CD28^IntCD95^LoCD45RA^HiCCR7^Hi) CD4⁺ T cells (A), and CD8⁺ T cells (B) plotted with increasing CD4 T cell counts in HIV+ and UNC. Frequencies of CD31⁺ and CD31^- cells on naïve CD4⁺ T cells (C), and naïve CD8⁺ T cells (D) in HIV+ and UNC. Frequencies of CD31⁺ and CD31^- cells on naïve CD4⁺ T cells (E), and naïve CD8⁺ T cells (F) plotted with increasing CD4 T cell counts in HIV+ and UNC. (n = 100 HIV⁺, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).

Fig 7. Evaluation of CD4⁺ T cell function, IL-2, IL-10 and IFN-γ production, in HIV-infected patients with controlled viremia on ART.

Frequencies of unstimulated and PMA stimulated IL-2 (A), IL-10 (C) and IFN-γ (E) CD4⁺ T cells in HIV+ and UNC. Frequencies of unstimulated and PMA stimulated IL-2 (B) IL-10 (D), IFN-γ (F) CD4⁺ T cells plotted with increasing CD4 T cell counts in HIV+ and UNC. (n = 100 HIV⁺, n = 75 UNC) (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).