Reduced IL-7R T Cell Expression and Increased Plasma sCD127 in Late Presenting HIV-Infected Individuals

Soluble IL-7Rα/sCD127 in Health, Disease, and Its Potential Role as a Therapeutic Agent

Soluble cytokine receptors can influence immune responses by modulating the biological functions of their respective ligands. These effects can be either agonistic or antagonistic and a number of soluble cytokine receptors have been shown to play critical roles in both maintenance of health and disease pathogenesis. Soluble IL-7Ra (sCD127) is one such example. With its impact on the IL-7/CD127 pathway, which is fundamental for the development and homeostasis of T cells, the role of sCD127 in health and disease has been extensively studied in recent years. Within this review, the role of sCD127 in maintaining host immune function is presented. Next, by addressing genetic factors affecting sCD127 expression and the associated levels of sCD127 production, the roles of sCD127 in autoimmune disease, infections and cancer are described. Finally, advances in the field of soluble cytokine therapy and the potential for sCD127 as a biomarker and therapeutic agent are discussed.

Soluble T-Cell Immunoglobulin Mucin Domain-3 Is Associated With Hepatitis C Virus Coinfection and Low-Grade Inflammation During Chronic Human Immunodeficiency Virus Infection

Background

In well treated human immunodeficiency virus infection (HIV), there is a residual immune activation and immune exhaustion that may contribute to increased risk of comorbidities. T-cell immunoglobulin mucin domain-3 (Tim-3) is an inhibitory molecule involved in HIV-associated T-cell dysfunction. The Tim-3 can be cleaved to soluble Tim-3 (sTim-3) that may serve as a soluble marker of immune exhaustion.

Methods

We measured sTim-3 with enzyme-linked immunosorbent assay DuoSets in a cross-sectional cohort of 1010 people with HIV (PWH) on antiretroviral therapy (ART), and 76 controls from the Copenhagen Co-Morbidity in HIV Infection (COCOMO) study, and in a longitudinal cohort of 60 PWH before and during ART.

Results

In the cross-sectional cohort, levels of sTim-3 were elevated in PWH on ART compared with controls, especially in hepatitis C virus (HCV)-coinfected individuals, and were associated with HCV viremia and inflammation. In the longitudinal cohort, pretreatment sTim-3 correlated with HIV viral load and decreased after ART initiation. Pretreatment sTim-3 correlated inversely with CD4 counts, but it did not predict immunological response in multivariable analyses.

Conclusions

Levels of sTim-3 decreased after ART initiation. In a cross-sectional cohort, levels of sTIM-3 were higher in PWH than in controls and were independently associated with HCV coinfection and high-sensitivity C-reactive protein, representing a potential link between immune exhaustion, inflammation, and risk of comorbidities.

Incomplete immune reconstitution in HIV/AIDS patients on antiretroviral therapy: Challenges of immunological non-responders

The morbidity and mortality of HIV type-1 (HIV-1)-related diseases were dramatically diminished by the grounds of the introduction of potent antiretroviral therapy, which induces persistent suppression of HIV-1 replication and gradual recovery of CD4⁺ T-cell counts. However, ∼10-40% of HIV-1-infected individuals fail to achieve normalization of CD4⁺ T-cell counts despite persistent virological suppression. These patients are referred to as "inadequate immunological responders," "immunodiscordant responders," or "immunological non-responders (INRs)" who show severe immunological dysfunction. Indeed, INRs are at an increased risk of clinical progression to AIDS and non-AIDS events and present higher rates of mortality than HIV-1-infected individuals with adequate immune reconstitution. To date, the underlying mechanism of incomplete immune reconstitution in HIV-1-infected patients has not been fully elucidated. In light of this limitation, it is of substantial practical significance to deeply understand the mechanism of immune reconstitution and design effective individualized treatment strategies. Therefore, in this review, we aim to highlight the mechanism and risk factors of incomplete immune reconstitution and strategies to intervene.

Increased Regulatory T-Cell Activity and Enhanced T-Cell Homeostatic Signaling in Slow Progressing HIV-infected Children

Pediatric slow progressors (PSP) are rare ART-naïve, HIV-infected children who maintain high CD4 T-cell counts and low immune activation despite persistently high viral loads. Using a well-defined cohort of PSP, we investigated the role of regulatory T-cells (TREG) and of IL-7 homeostatic signaling in maintaining normal-for-age CD4 counts in these individuals. Compared to children with progressive disease, PSP had greater absolute numbers of TREG, skewed toward functionally suppressive phenotypes. As with immune activation, overall T-cell proliferation was lower in PSP, but was uniquely higher in central memory TREG (CM TREG), indicating active engagement of this subset. Furthermore, PSP secreted higher levels of the immunosuppressive cytokine IL-10 than children who progressed. The frequency of suppressive TREG, CM TREG proliferation, and IL-10 production were all lower in PSP who go on to progress at a later time-point, supporting the importance of an active TREG response in preventing disease progression. In addition, we find that IL-7 homeostatic signaling is enhanced in PSP, both through preserved surface IL-7receptor (CD127) expression on central memory T-cells and increased plasma levels of soluble IL-7receptor, which enhances the bioactivity of IL-7. Combined analysis, using a LASSO modeling approach, indicates that both TREG activity and homeostatic T-cell signaling make independent contributions to the preservation of CD4 T-cells in HIV-infected children. Together, these data demonstrate that maintenance of normal-for-age CD4 counts in PSP is an active process, which requires both suppression of immune activation through functional TREG, and enhanced T-cell homeostatic signaling.

Brief Report: CD52 Expression on CD4+ T Cells in HIV-Positive Individuals on cART

BACKGROUND

HIV persists in a latent state in quiescent CD4 T cells preventing eradication of HIV. CD52 is a surface molecule modulated by HIV. We aimed at examining factors related to CD52 expression on CD4 T cells in HIV-positive individuals and the impact of initiation of combination antiretroviral therapy (cART).

METHODS

Peripheral blood mononuclear cells from 18 HIV-positive individuals and 10 uninfected age- and sex-matched controls were examined by flow cytometry for CD38 and CD52 expression on CD4 T cells. Stimulation assays were performed on 8 healthy blood donors to determine a cutoff for CD52 expression.

RESULTS

All examined CD4 T cells expressed CD52. However, both CD4 T cells with higher (CD52) and with lower CD52 expression (CD52dim) were found in HIV-positive individuals compared to uninfected controls. Two % CD52dim cells defined groups of high and low CD52: the group of individuals with high CD52 had higher CD4 counts at baseline (447 vs. 54 cells/µL, P = 0.02) and higher increase in CD4 counts during follow-up compared with low CD52 (P = 0.02). After 12 months of cART, CD52 increased (median fluorescence intensity 4846 vs. 5621, P < 0.05), whereas CD38 decreased (median fluorescence intensity 1519 vs. 730, P < 0.0001).

CONCLUSIONS

All HIV-positive individuals in this cohort had CD4 T cells that expressed CD52. Higher CD4 counts were found in those with high CD52. Furthermore, an increase in CD52 was found after 12 months of cART, indicating that anti-CD52 antibodies may be more efficient for depletion of CD4 T cells in HIV-positive individuals on cART.

Interferon-α-Mediated Activation of T Cells from Healthy and HIV-Infected Individuals Is Suppressed by Δ9-Tetrahydrocannabinol

Patients with HIV routinely use medicinal cannabinoids to treat neuropathic pain, anxiety, and human immunodeficiency virus (HIV)-associated wasting. However, Δ⁹-tetrahydrocannabinol (THC), the primary psychoactive cannabinoid in cannabis, suppresses T-cell function and secretion of interferons, both critically important in the antiviral immune response. Interferon-α (IFNα), a key cytokine in T-cell activation and peripheral control of HIV infection, can potentiate responsiveness to interleukin-7 (IL-7), a crucial homeostatic cytokine for peripheral T-cell maintenance. The objective of this investigation was to compare the response of T cells to stimulation by IFNα and IL-7 in T cells from healthy and HIV⁺ donors in the absence and presence of THC. To compare T-cell responses between healthy and HIV⁺ donors signaling through IFNα receptor, IFNα-induced expression of IL-7α receptor (IL-7Rα), cognate signaling through IL-7R, and on IL-7-mediated T-cell proliferation were measured by flow cytometry and real-time quantitative polymerase chain reaction. CD8⁺ T cells from HIV⁺ donors showed a diminished response to IFNα-induced phosphorylated signal transducer and activator of transcription-1 activation compared with CD8⁺ T cells from healthy donors, whereas CD4⁺ T cells from HIV⁺ donors and healthy donors were comparable. Treatment with IFNα promoted IL-7R expression and potentiated IL-7-induced STAT5 phosphorylation to augment IL-7-mediated proliferation by T cells from healthy and HIV⁺ donors. Finally, HIV⁺ donors exhibited reduced sensitivity to THC-mediated suppression by IFNα- and IL-7-mediated stimulation compared with healthy donors. These results further support THC as being immune suppressive while identifying putatively beneficial aspects of cannabinoid-based therapies in HIV⁺ patients.

Increased proportions of B cells with spontaneous production of interleukin-10 in HIV-infected individuals are normalized during combination antiretroviral therapy: a longitudinal study

Interleukin-10 (IL-10)-producing B cells (B10 cells) may inhibit HIV-specific T cells and are elevated in untreated HIV infection. We aimed to determine the effect of combination antiretroviral treatment (cART) on the proportion of B10 cells. Furthermore, we compared B10-cell proportions in HIV-infected progressors and viremic controllers. This was a prospective study including HIV-infected progressors, viremic controllers and healthy controls. Progressors initiating cART were followed for 6 months. Purified B cells were stimulated with CpG, alone or in combination with HIV gp120, and the proportion of B10 cells was measured by flow cytometry. Without stimulation, the B10-cell proportion was higher in progressors than in healthy controls, while viremic controllers and healthy controls had comparable proportions. Moreover, the proportion of CD24^hi CD38^hi transitional B cells was higher in progressors than in healthy controls. After initiation of cART, the proportion of B10 cells and transitional B cells decreased. In conclusion, progressors had elevated B10-cell proportions, while viremic controllers displayed normal proportions. After initiation of cART, the B10-cell proportion decreased. This could limit B10-cell-mediated suppression of specific CD8⁺ T-cell responses.

Tryptophan catabolism and immune activation in primary and chronic HIV infection

BACKGROUND

Kynurenine/Tryptophan ratio (KTR) is increased in HIV infection, and linked to immune activation. We hypothesized that early cART initiation results in lower KTR compared to late initiation. Furthermore, we hypothesized that KTR prior to cART is a predictor of the magnitude of subsequent reduction in immune activation.

METHODS

Prospective study including 57 HIV-infected individuals (primary HIV infection (N = 14), early presenters (>350 CD4+ T cells/μL, N = 24), late presenters (<200 CD4+ T cells/μL, N = 19)). Kynurenine and tryptophan were analysed by liquid chromatography-tandem mass spectrometry. Total CD4+ and CD8+ T cells were determined and proportion of activated CD38 + HLA-DR+ Tcells was measured using flow cytometry at baseline and after 6 and 12 months of cART.

RESULTS

At baseline, primary HIV infection had higher KTR than early presenters. However, similar KTR in primary HIV infection and early presenters was found after cART initiation, while late presenters had higher KTR at all time points. In primary HIV infection and early presenters, KTR was positively associated with proportion of activated cells at baseline. Furthermore, in early presenters the KTR at baseline was associated with proportion of activated cells after 6 and 12 months. Interestingly, in primary HIV infection the KTR at baseline was positively associated with reduction in proportion of CD8 + CD38 + HLA-DR T cells after 6 and 12 months.

CONCLUSIONS

Lower kynurenine/tryptophan ratio during follow-up was found after early initiation of cART. KTR in primary HIV infection and early presenters was positively associated with immune activation. Importantly, KTR in primary HIV infection predicted the magnitude of subsequent reduction in immune activation. Thus, a beneficial effect of early cART on KTR was suggested.

Immune recovery in acute and chronic HIV infection and the impact of thymic stromal lymphopoietin

Background

Symptomatic primary HIV infection is associated with an adverse prognosis, and immediate initiation of combination antiretroviral therapy (cART) is recommended. However, little is known about immunological predictors of immune recovery. Thymic Stromal Lymphopoietin (TSLP) is a cytokine that promotes CD4+ T cells homeostatic polyclonal proliferation and regulates Th17/regulatory T-cell balance, immunological functions known to be affected during primary HIV infection. The aim of this study was to describe immune recovery in primary and chronic HIV infection and possible impact of TSLP.

Methods

Prospective study including 100 HIV-infected individuals (primary HIV infection (N = 14), early presenters (>350 CD4+ T cells/μL, N = 42), late presenters without advanced disease (200–350 CD4+ T cells/μL, N = 24) and with advanced disease (<200 CD4+ T cells/μL, N = 20) and). Immune recovery was defined as increase in CD4+ T cells count from baseline to a given time of follow-up. Plasma TSLP was determined using ELISA and CD4+ T cell subpopulations (recent thymic emigrants, naïve and memory cells) were measured using flow cytometry at baseline and after 6, 12 and 24 months of cART.

Results

Immune recovery was comparable in all groups, and no differences in immune homeostasis were found between primary HIV infection and early presenters, whereas differences in absolute counts and proportions of CD4+ T cell subpopulations were found between primary HIV infection and late presenters. TSLP was elevated in primary HIV infection at baseline and after 24 months of cART. Interestingly, TSLP was negatively associated with proportion of recent thymic emigrants (correlation coefficient −0.60, p = 0.030). TSLP was not associated with immune recovery in primary HIV infection.

Conclusions

Immune recovery was comparable in primary and chronic HIV infection whereas differences in absolute counts and proportions of CD4+ T cell subpopulations were found between primary HIV infection and late presenters supporting early initiation of cART. Higher plasma TSLP was found in primary HIV infection, and TSLP was associated with lower thymic output, but not with immune recovery. These findings indicate a possible role of TSLP in immune homeostasis in HIV infection but do not support TSLP to affect immune recovery in primary HIV infection.