HIV infection perturbs interleukin-7 signaling at the step of STAT5 nuclear relocalization

Effects of Antiretroviral Treatment on Central and Peripheral Immune Response in Mice with EcoHIV Infection

HIV infection is an ongoing global health issue, despite increased access to antiretroviral therapy (ART). People living with HIV (PLWH) who are virally suppressed through ART still experience negative health outcomes, including neurocognitive impairment. It is increasingly evident that ART may act independently or in combination with HIV infection to alter the immune state, though this is difficult to disentangle in the clinical population. Thus, these experiments used multiplexed chemokine/cytokine arrays to assess peripheral (plasma) and brain (nucleus accumbens; NAc) expression of immune targets in the presence and absence of ART treatment in the EcoHIV mouse model. The findings identify the effects of EcoHIV infection and of treatment with bictegravir (B), emtricitabine (F), and tenofovir alafenamide (TAF) on the expression of numerous immune targets. In the NAc, this included EcoHIV-induced increases in IL-1α and IL-13 expression and B/F/TAF-induced reductions in KC/CXCL1. In the periphery, EcoHIV suppressed IL-6 and LIF expression, while B/F/TAF reduced IL-12p40 expression. In the absence of ART, IBA-1 expression was negatively correlated with CX3CL1 expression in the NAc of EcoHIV-infected mice. These findings identify distinct effects of ART and EcoHIV infection on peripheral and central immune factors and emphasize the need to consider ART effects on neural and immune outcomes.

Effects of antiretroviral treatment on central and peripheral immune response in mice with EcoHIV infection

HIV infection is an ongoing global health issue despite increased access to antiretroviral therapy (ART). People living with HIV (PLWH) who are virally suppressed through ART still experience negative health outcomes, including neurocognitive impairment. It is increasingly evident that ART may act independently or in combination with HIV infection to alter immune state, though this is difficult to disentangle in the clinical population. Thus, these experiments used multiplexed chemokine/cytokine arrays to assess peripheral (plasma) and brain (nucleus accumbens; NAc) expression of immune targets in the presence and absence of ART treatment in the EcoHIV mouse model. The findings identify effects of EcoHIV infection and of treatment with bictegravir (B), emtricitabine (F) and tenofovir alafenamide (TAF) on expression of numerous immune targets. In the NAc, this included EcoHIV-induced increases in IL-1α and IL-13 expression and B/F/TAF-induced reductions in KC/CXCL1. In the periphery, EcoHIV suppressed IL-6 and LIF expression, while B/F/TAF reduced IL-12p40 expression. In absence of ART, IBA-1 expression was negatively correlated with CX3CL1 expression in the NAc of EcoHIV-infected mice. These findings identify distinct effects of ART and EcoHIV infection on peripheral and central immune factors and emphasize the need to consider ART effects on neural and immune outcomes.

New Flow Cytometric Methods for Monitoring STAT5 Signaling Reveal Responses to SARS-CoV-2 Antigen-Specific Stimulation in FOXP3+ Regulatory T Cells also in Patients with Advanced Chronic Lymphocytic Leukemia

Increased frequency of CD4⁺CD25⁺ regulatory T-cells (Treg) has been associated with disease progression in chronic lymphocytic leukemia (CLL). Flow cytometric methods, which allow for the simultaneous analysis of their specific transcription factor Foxp3 and activated STAT proteins, together with proliferation can help to elucidate the signaling mechanisms driving Treg expansion and suppression of FOXP3- conventional CD4⁺T-cells (Tcon). Herein, we first report a novel approach in which STAT5 phosphorylation (pSTAT5) and proliferation (BrdU-FITC incorporation) could be analyzed specifically in FOXP3+ and FOXP3- responding cells after CD3/CD28 stimulation. The addition of magnetically purified CD4⁺CD25⁺ T-cells from healthy donors to cocultured autologous CD4⁺CD25^- T-cells resulted in suppression of Tcon cell cycle progression accompanied by a decrease in pSTAT5. Next, a method using imaging flow cytometry is presented for the detection of cytokine-dependent pSTAT5 nuclear translocation in FOXP3-expressing cells. Finally, we discuss our experimental data obtained by combining Treg pSTAT5 analysis and antigen-specific stimulation with SARS-CoV-2 antigens. Applying these methods on samples from patients revealed Treg responses to antigen-specific stimulation and significantly higher basal pSTAT5 in CLL patients treated with immunochemotherapy. Thus, we speculate that through the use of this pharmacodynamic tool, the efficacy of immunosuppressive drugs and their possible off-target effects can be assessed.

Preservation of lymphocyte functional fitness in perinatally-infected and treated HIV+ pediatric patients displaying sub-optimal viral control

Background

Host–pathogen dynamics associated with HIV infection are quite distinct in children versus adults. We interrogated the functional fitness of the lymphocyte responses in two cohorts of perinatally infected HIV+ pediatric subjects with early anti-retroviral therapy (ART) initiation but divergent patterns of virologic control. We hypothesized that sub-optimal viral control would compromise immune functional fitness.

Methods

The immune responses in the two HIV+ cohorts (n = 6 in each cohort) were benchmarked against the responses measured in age-range matched, uninfected healthy control subjects (n = 11) by utilizing tests for normality, and comparison [the Kruskal–Wallis test, and the two-tailed Mann–Whitney U test (where appropriate)]. Lymphocyte responses were examined by intra-cellular cytokine secretion, degranulation assays as well as phosflow. A subset of these data were further queried by an automated clustering algorithm. Finally, we evaluated the humoral immune responses to four childhood vaccines in all three cohorts.

Results

We demonstrate that contrary to expectations pediatric HIV+ patients with sub-optimal viral control display no significant deficits in immune functional fitness. In fact, the patients that display better virologic control lack functional Gag-specific T cell responses and compared to healthy controls they display signaling deficits and an enrichment of mitogen-stimulated CD3 negative and positive lymphocyte clusters with suppressed cytokine production.

Conclusions

These results highlight the immune resilience in HIV+ children on ART with sub-optimal viral control. With respect to HIV+ children on ART with better viral control, our data suggest that this cohort might potentially benefit from targeted interventions that might mitigate cell-mediated immune functional quiescence.

Structural and mutational analysis of member-specific STAT functions

BACKGROUND

The STAT family of transcription factors control gene expression in response to signals from various stimulus. They display functions in diseases ranging from autoimmunity and chronic inflammatory disease to cancer and infectious disease.

SCOPE OF REVIEW

This work uses an approach informed by structural data to explore how domain-specific structural variations, post-translational modifications, and the cancer genome mutational landscape dictate STAT member-specific activities.

MAJOR CONCLUSIONS

We illustrated the structure-function relationship of STAT proteins and highlighted their effect on member-specific activity. We correlated disease-linked STAT mutations to the structure and cancer genome mutational landscape and proposed rational drug targeting approaches of oncogenic STAT pathway addiction.

GENERAL SIGNIFICANCE

Hyper-activated STATs and their variants are associated with multiple diseases and are considered high value oncology targets. A full understanding of the molecular basis of member-specific STAT-mediated signaling and the strategies to selectively target them requires examination of the difference in their structures and sequences.

PLA2G1B is involved in CD4 anergy and CD4 lymphopenia in HIV-infected patients

The precise mechanism leading to profound immunodeficiency of HIV-infected patients is still only partially understood. Here, we show that more than 80% of CD4+ T cells from HIV-infected patients have morphological abnormalities. Their membranes exhibited numerous large abnormal membrane microdomains (aMMDs), which trap and inactivate physiological receptors, such as that for IL-7. In patient plasma, we identified phospholipase A2 group IB (PLA2G1B) as the key molecule responsible for the formation of aMMDs. At physiological concentrations, PLA2G1B synergized with the HIV gp41 envelope protein, which appears to be a driver that targets PLA2G1B to the CD4+ T cell surface. The PLA2G1B/gp41 pair induced CD4+ T cell unresponsiveness (anergy). At high concentrations in vitro, PLA2G1B acted alone, independently of gp41, and inhibited the IL-2, IL-4, and IL-7 responses, as well as TCR-mediated activation and proliferation, of CD4+ T cells. PLA2G1B also decreased CD4+ T cell survival in vitro, likely playing a role in CD4 lymphopenia in conjunction with its induced IL-7 receptor defects. The effects on CD4+ T cell anergy could be blocked by a PLA2G1B-specific neutralizing mAb in vitro and in vivo. The PLA2G1B/gp41 pair constitutes what we believe is a new mechanism of immune dysfunction and a compelling target for boosting immune responses in HIV-infected patients.

Interactions of the Nipah Virus P, V, and W Proteins across the STAT Family of Transcription Factors

The Nipah virus (NiV) phosphoprotein (P) gene encodes four proteins. Three of these-P, V, and W-possess a common N-terminal domain but distinct C termini. These proteins interact with immune modulators. Previous studies demonstrated that P, V, and W bind STAT1 and STAT4 and that V also interacts with STAT2 but not with STAT3. The STAT1 and STAT2 interactions block interferon (IFN)-induced STAT tyrosine phosphorylation. To more fully characterize the interactions of P, V, and W with the STATs, we screened for interaction of each viral protein with STATs 1 to 6 by coimmunoprecipitation. We demonstrate that NiV P, V, and W interact with STAT4 through their common N-terminal domain and block STAT4 activity, based on a STAT4 response element reporter assay. Although none of the NiV proteins interact with STAT3 or STAT6, NiV V, but not P or W, interacts with STAT5 through its unique C terminus. Furthermore, the interaction of NiV V with STAT5 was not disrupted by overexpression of the N-terminal binding STAT1 or the C-terminal binding MDA5. NiV V also inhibits a STAT5 response element reporter assay. Residues 114 to 140 of the common N-terminal domain of the NiV P gene products were found to be sufficient to bind STAT1 and STAT4. Analysis of STAT1-STAT3 chimeras suggests that the P gene products target the STAT1 SH2 domain. When fused to GST, the 114-140 peptide is sufficient to decrease STAT1 phosphorylation in IFN-β-stimulated cells, suggesting that this peptide could potentially be fused to heterologous proteins to confer inhibition of STAT1- and STAT4-dependent responses.IMPORTANCE How Nipah virus (NiV) antagonizes innate immune responses is incompletely understood. The P gene of NiV encodes the P, V, and W proteins. These proteins have a common N-terminal sequence that is sufficient to bind to STAT1 and STAT2 and block IFN-induced signal transduction. This study sought to more fully understand how P, V, and W engage with the STAT family of transcription factors to influence their functions. The results identify a novel interaction of V with STAT5 and demonstrate V inhibition of STAT5 function. We also demonstrate that the common N-terminal residues 114 to 140 of P, V, and W are critical for inhibition of STAT1 and STAT4 function, map the interaction to the SH2 region of STAT1, and show that a fusion construct with this peptide significantly inhibits cytokine-induced STAT1 phosphorylation. These data clarify how these important virulence factors modulate innate antiviral defenses.

The Dynamic Interface of Viruses with STATs

Viruses commonly antagonize the antiviral type I interferon response by targeting signal transducer and activator of transcription 1 (STAT1) and STAT2, key mediators of interferon signaling. Other STAT family members mediate signaling by diverse cytokines important to infection, but their relationship with viruses is more complex. Importantly, virus-STAT interaction can be antagonistic or stimulatory depending on diverse viral and cellular factors. While STAT antagonism can suppress immune pathways, many viruses promote activation of specific STATs to support viral gene expression and/or produce cellular conditions conducive to infection. It is also becoming increasingly clear that viruses can hijack noncanonical STAT functions to benefit infection. For a number of viruses, STAT function is dynamically modulated through infection as requirements for replication change. Given the critical role of STATs in infection by diverse viruses, the virus-STAT interface is an attractive target for the development of antivirals and live-attenuated viral vaccines. Here, we review current understanding of the complex and dynamic virus-STAT interface and discuss how this relationship might be harnessed for medical applications.

Benzotriazoles Reactivate Latent HIV-1 through Inactivation of STAT5 SUMOylation

The presence of latent HIV-1 in infected individuals represents a major barrier preventingviral eradication. For that reason, reactivation of latent viruses in the presence of antiretroviral regimens has been proposed as a therapeutic strategy to achieve remission. We screened for small molecules and identified several benzotriazole derivatives with the ability to reactivate latent HIV-1. In the presence of IL-2, benzotriazoles reactivated and reduced the latent reservoir in primary cells, and, remarkably, viral reactivation was achieved without inducing cell proliferation, T cell activation, or cytokine release. Mechanistic studies showed that benzotriazoles block SUMOylation of phosphorylated STAT5, increasing STAT5’s activity and occupancy of the HIV-1 LTR. Our results identify benzotriazoles as latency reversing agents and STAT5 signaling and SUMOylation as targets for HIV-1 eradication strategies. These compounds represent a different direction in the search for “shock and kill” therapies.

Aberrant plasma IL-7 and soluble IL-7 receptor levels indicate impaired T-cell response to IL-7 in human tuberculosis

T-cell proliferation and generation of protective memory during chronic infections depend on Interleukin-7 (IL-7) availability and receptivity. Regulation of IL-7 receptor (IL-7R) expression and signalling are key for IL-7-modulated T-cell functions. Aberrant expression of soluble (s) and membrane-associated (m) IL-7R molecules is associated with development of autoimmunity and immune failure in acquired immune deficiency syndrome (AIDS) patients. Here we investigated the role of IL-7/IL-7R on T-cell immunity in human tuberculosis. We performed two independent case-control studies comparing tuberculosis patients and healthy contacts. This was combined with follow-up examinations for a subgroup of tuberculosis patients under therapy and recovery. Blood plasma and T cells were characterised for IL-7/sIL-7R and mIL-7R expression, respectively. IL-7-dependent T-cell functions were determined by analysing STAT5 phosphorylation, antigen-specific cytokine release and by analysing markers of T-cell exhaustion and inflammation. Tuberculosis patients had lower soluble IL-7R (p < 0.001) and higher IL-7 (p < 0.001) plasma concentrations as compared to healthy contacts. Both markers were largely independent and aberrant expression normalised during therapy and recovery. Furthermore, tuberculosis patients had lower levels of mIL-7R in T cells caused by post-transcriptional mechanisms. Functional in vitro tests indicated diminished IL-7-induced STAT5 phosphorylation and impaired IL-7-promoted cytokine release of Mycobacterium tuberculosis-specific CD4⁺ T cells from tuberculosis patients. Finally, we determined T-cell exhaustion markers PD-1 and SOCS3 and detected increased SOCS3 expression during therapy. Only moderate correlation of PD-1 and SOCS3 with IL-7 expression was observed. We conclude that diminished soluble IL-7R and increased IL-7 plasma concentrations, as well as decreased membrane-associated IL-7R expression in T cells, reflect impaired T-cell sensitivity to IL-7 in tuberculosis patients. These findings show similarities to pathognomonic features of impaired T-cell functions and immune failure described in AIDS patients.

IL-7 is important for the development and homeostasis of T cells and promotes antigen-specific T-cell responses. Aberrant expression of plasma IL-7 and soluble IL-7R are found in autoimmune diseases and chronic viral infections. In AIDS patients—especially those who fail to reconstitute T-cell numbers during therapy—impaired IL-7-promoted T-cell functions indicated T-cell exhaustion/senescence. In order to evaluate the potential impact of IL-7 on tuberculosis, we characterised various parameters involved in the IL-7-response of tuberculosis patients and healthy contacts. Despite IL-7 being available at higher plasma levels among tuberculosis patients, the T-cell response to IL-7 was impaired when compared to healthy contacts. Soluble IL-7R levels were aberrantly low in plasma during acute tuberculosis but did not account for impaired IL-7 usage. Chronic inflammation in tuberculosis patients—reflected by increased IL-6 plasma levels—did not account for dysfunctional T-cell responses and analysed T-cell exhaustion markers were only moderately correlated. Our findings demonstrate that availability of IL-7 alone is not sufficient to promote protective T-cell immunity against tuberculosis. We describe aberrant IL-7/soluble IL-7R expression and impaired IL-7-mediated T-cell functions in tuberculosis patients with similarities and differences to described IL-7 dysregulation seen in patients with AIDS.

Compartment-specific distribution of human intestinal innate lymphoid cells is altered in HIV patients under effective therapy

Innate lymphocyte cells (ILCs), a novel family of innate immune cells are considered to function as key orchestrators of immune defences at mucosal surfaces and to be crucial for maintaining an intact intestinal barrier. Accordingly, first data suggest depletion of ILCs to be involved in human immunodeficiency virus (HIV)-associated damage of the intestinal mucosa and subsequent microbial translocation. However, although ILCs are preferentially localized at mucosal surfaces, only little is known regarding distribution and function of ILCs in the human gastrointestinal tract. Here, we show that in HIV(-) individuals composition and functional capacity of intestinal ILCs is compartment-specific with group 1 ILCs representing the major fraction in the upper gastrointestinal (GI) tract, whereas ILC3 are the predominant population in ileum and colon, respectively. In addition, we present first data indicating that local cytokine concentrations, especially that of IL-7, might modulate composition of gut ILCs. Distribution of intestinal ILCs was significantly altered in HIV patients, who displayed decreased frequency of total ILCs in ileum and colon owing to reduced numbers of both CD127(+)ILC1 and ILC3. Of note, frequency of colonic ILC3 was inversely correlated with serum levels of I-FABP and sCD14, surrogate markers for loss of gut barrier integrity and microbial translocation, respectively. Both expression of the IL-7 receptor CD127 on ILCs as well as mucosal IL-7 mRNA levels were decreased in HIV(+) patients, especially in those parts of the GI tract with reduced ILC frequencies, suggesting that impaired IL-7 responses of ILCs might contribute to incomplete reconstitution of ILCs under effective anti-retroviral therapy. This is the first report comparing distribution and function of ILCs along the intestinal mucosa of the entire human gastrointestinal tract in HIV(+) and HIV(-) individuals.

HIV-1 tat protein recruits CIS to the cytoplasmic tail of CD127 to induce receptor ubiquitination and proteasomal degradation

HIV-1 Tat protein down regulates expression of the IL-7 receptor alpha-chain (CD127) from the surface of CD8 T cells resulting in impaired T cell proliferation and cytolytic capacity. We have previously shown that soluble Tat protein is taken up by CD8 T cells and interacts with the cytoplasmic tail of CD127 to induce receptor degradation. The N-terminal domain of Tat interacts with CD127 while the basic domain directs CD127 to the proteasome. We have also shown that upon IL-7 binding to its receptor, CD127 is phosphorylated resulting in CIS-mediated proteasomal degradation. Here, we show that Tat mimics this process by recruiting CIS to CD127 in the absence of IL-7 and receptor phosphorylation, leading to CD127 ubiquitination and degradation. Tat therefore acts as an adapter to induce cellular responses under conditions where they may not otherwise occur. Thusly, Tat reduces IL-7 signaling and impairs CD8 T cell survival and function.

Alemtuzumab as Antirejection Therapy: T Cell Repopulation and Cytokine Responsiveness

Supplemental digital content is available in the text.

Background

Alemtuzumab induction therapy in kidney transplant patients results in T cell depletion followed by slow immune reconstitution of memory T cells with reduced immune functions. The kinetics and functional characteristics of T cell reconstitution when alemtuzumab is given during immune activation, ie, as antirejection therapy, are unknown.

Methods

Patients (n = 12) with glucocorticoid-resistant or severe vascular kidney transplant rejection were treated with alemtuzumab. Flow cytometric analysis was performed on whole blood to measure cell division by the marker Ki-67, and cytokine responsiveness by IL-2–mediated and IL-7–mediated phosphorylation of signal transducer and activator of transcription 5 of T cells before and during the first year after rejection therapy.

Results

At 1 year after alemtuzumab antirejection therapy, the total T cell population recovered to baseline level. Repopulation of CD4+ and CD8+ T cells was associated with increased percentages of Ki-67+ proliferating T cells (P < 0.05). In addition, both populations showed a phenotypic shift toward relatively more memory T cells (P < 0.01). At the functional level, IL-7 reactivity of CD4+ memory T cells was diminished, reflected by a decreased capacity to phosphorylate signal transducer and activator of transcription 5 during the first 6 months after alemtuzumab treatment (P < 0.05), whereas reactivity to IL-2 was preserved. CD8+ T cells were affected in terms of both IL-2 and IL-7 responses (both P < 0.05). After reconstitution, relatively more regulatory T cells were present, and a relatively high proportion of Ki-67+ T cells was observed.

Conclusions

Preliminary data from this small series suggest that alemtuzumab antirejection therapy induces homeostatic proliferation of memory and regulatory T cells with diminished responsiveness to the homeostatic cytokine IL-7. IL-2 responsiveness was affected in repopulated CD8+ T cells.

T cells Exhibit Reduced Signal Transducer and Activator of Transcription 5 Phosphorylation and Upregulated Coinhibitory Molecule Expression After Kidney Transplantation

BACKGROUND

T-cell depletion therapy is associated with diminished interleukin (IL)-7/IL-15-dependent homeostatic proliferation resulting in incomplete T-cell repopulation. Furthermore, it is associated with impaired T-cell functions. We hypothesized that this is the result of impaired cytokine responsiveness of T cells, through affected signal transducer and activator of transcription (STAT)5 phosphorylation and upregulation of coinhibitory molecules.

MATERIALS AND METHODS

Patients were treated with T cell-depleting rabbit antithymocyte globulin (rATG) (6 mg/kg, n = 17) or nondepleting, anti-CD25 antibody (basiliximab, 2 × 40 mg, n = 25) induction therapy, in combination with tacrolimus, mycophenolate mofetil, and steroids. Before and the first year after transplantation, IL-7 and IL-2 induced STAT5 phosphorylation, and the expression of the coinhibitory molecules programmed cell death protein 1 (PD-1), T cell immunoglobulin mucin-3 (TIM-3), lymphocyte activation gene-3 (LAG-3), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), cluster of differentiation (CD) 160, and CD244 was measured by flow cytometry.

RESULTS

The first year after rATG, CD4+, and CD8+ T cells were affected in their IL-7-dependent phosphorylation of STAT5 (pSTAT5) which was most outspoken in the CD8+ memory population. The capacity of CD4+ and CD8+ T cells to pSTAT5 in response to IL-2 decreased after both rATG and basiliximab therapy. After kidney transplantation, the percentage of TIM-3+, PD-1+, and CD160+CD4+ T cells and the percentage of CD160+ and CD244+CD8+ T cells increased, with no differences in expression between rATG- and basiliximab-treated patients. The decrease in pSTAT5 capacity CD8+ T cells and the increase in coinhibitory molecules were correlated.

CONCLUSIONS

We show that memory T cells in kidney transplant patients, in particular after rATG treatment, have decreased cytokine responsiveness by impaired phosphorylation of STAT5 and have increased expression of coinhibitory molecules, processes which were correlated in CD8+ T cells.

[IRIS: a paradoxical inflammatory reaction in patients treated simultaneously for tuberculosis and HIV]

Co-infection with Mycobacterium tuberculosis (Mtb) and human immunodeficiency virus (HIV) represents a major threat to public health worldwide. The treatment of patients coinfected by Mtb and HIV is often complicated by the occurrence of an immune reconstitution inflammatory syndrome (IRIS), resulting in the unexpected resumption of tuberculosis symptoms after the initiation of antiretroviral therapy. IRIS is associated with a rapid reconstitution of CD4(+) T cell responses specific for Mtb, which is promoted by the control of HIV replication and a high concentration of available interleukin-7. Macrophages, whose activity is suddenly stimulated by CD4(+) T cell help, respond by an exacerbated inflammatory response in Mtb-rich tissues. A major research objective remains to identify biomarkers which could allow a reliable prediction of IRIS occurrence, in order to optimize medical care for the many patients affected by both HIV and tuberculosis in resource-limited settings.

IFN-α exerts opposing effects on activation-induced and IL-7-induced proliferation of T cells that may impair homeostatic maintenance of CD4+ T cell numbers in treated HIV infection

To determine whether IFN-α is a cause of the T cell hyperactivation and IL-7 signaling pathway defects that are observed in some HIV patients receiving antiretroviral therapy, we have investigated the effect of IFN-α on the proliferation of CD4(+) and CD8(+) T cells from healthy donors (n = 30) and treated HIV(+) donors (n = 20). PBMC were cultured for 7 d with staphylococcal enterotoxin B or IL-7 in the absence or presence of 100 U/ml IFN-α8. Total and naive CD4(+) and CD8(+) T cells were assessed for proliferation (via Ki67 expression), CD127 expression, and phosphorylated STAT5 levels using flow cytometry. IFN-α significantly enhanced activation-induced proliferation (via staphylococcal enterotoxin B stimulation) but inhibited homeostatic proliferation (IL-7 induced) of CD4(+) and CD8(+) T cells. Both of these effects may adversely affect CD4(+) T cell homeostasis in HIV patients. CD127 expression was increased in both healthy and HIV(+) donors following culture with IFN-α8, and levels of IL-7-induced phosphorylated STAT5 were increased by IFN-α8 in healthy donors only. Hence, the inhibitory effects of IFN-α on IL-7-induced proliferation of CD4(+) T cells are unlikely to be mediated by downregulation of CD127 expression or inhibition of STAT5 phosphorylation. These data suggest that increased IFN-α activity may promote the loss of T cells by accelerating cell turnover and activation-induced cell death while decreasing the renewal of T cells by inhibiting the proliferative effect of IL-7.

Biomarkers of CD4+ T-cell activation as risk factors for tuberculosis-associated immune reconstitution inflammatory syndrome

OBJECTIVE

Patients coinfected with HIV and Mycobacterium tuberculosis frequently experience a paradoxical worsening of tuberculosis (TB) symptoms early after the initiation of combination antiretroviral therapy (cART). This immune reconstitution inflammatory syndrome (TB-IRIS) can lead to significant morbidity and needs to be distinguished from TB recurrence due to ineffective treatment. We investigated whether plasma biomarkers could predict the occurrence of TB-IRIS.

DESIGN

ANRS 129 BKVIR is a single-arm multicentre trial that enrolled 69 cART-naïve HIV-1-infected patients treated for TB. The patients received once-daily tenofovir/emtricitabine/efavirenz first-line regimen. TB-IRIS cases (IRIS+) were validated by an Event Review Committee.

METHODS

A panel of 26 plasma biomarkers was monitored longitudinally for 24 weeks from cART initiation onward, using multiplexed assays and high-sensitivity ELISA. Statistical analyses of biomarkers were adjusted for test multiplicity.

RESULTS

One-third of patients (n=23) experienced TB-IRIS. The inflammatory cytokines and chemokines interleukin (IL)-6, IL-8, interferon-gamma-induced protein 10 (IP-10), and tumour necrosis factor-alpha (TNF-α) showed increased plasma levels at week 4 in IRIS-positive (IRIS+) patients (P<0.05 for each biomarker). The soluble IL-2 receptor sCD25, which is released upon CD4 T-cell activation, was significantly increased at week 0 in IRIS+ patients (P<0.05), and remained elevated throughout follow-up. IL-7, a key homeostatic cytokine for CD4 T-cells, showed a trend for higher values in the TB-IRIS group. Both sCD25 and IL-7 baseline levels were independently associated with a shorter time to TB-IRIS occurrence (P=0.005 and P=0.02, respectively).

CONCLUSION

These findings support a role for CD4 T-cell activation prior to massive inflammation in the development of TB-IRIS.

Interleukin-7 signalling defects in naive CD4+ T cells of HIV patients with CD4+ T-cell deficiency on antiretroviral therapy are associated with T-cell activation and senescence

OBJECTIVE

To examine the relationship of defects in interleukin (IL)-7-induced naive CD4 T-cell homeostasis with residual immune activation and CD4 T-cell senescence in HIV patients receiving antiretroviral therapy (ART) who exhibit persistent CD4 T-cell deficiency.

DESIGN

IL-7 induced proliferation of, and IL-7 receptor signalling in, total and naive CD4 T cells of HIV patients who had low (<350 cells/μl) or normal (>500 cells/μl) CD4 T-cell counts on ART was examined and related to markers of CD4 T-cell activation and senescence and innate immune activation.

METHODS

Total, naive (CD45RA CD27) and CD31 naive CD4 T cells from aviremic HIV patients (n=39) with nadir CD4 T-cell counts less than 100 cells/μl, who had received ART for a median time of 7 (range 1-11) years, were assessed for CD127 expression, proliferation (Ki67), signal transducer and activator of transcription 5 phosphorylation (pSTAT5) and CD127 modulation following IL-7 stimulation. Changes were related to proportions of CD4 T cells expressing HLA-DR or CD57 and plasma levels of sCD14, CXCL9 and CXCL10.

RESULTS

Patients with CD4 T-cell deficiency exhibited lower expression of CD127 on total, naive and CD31 naive CD4 T cells. Downregulation of CD127 after culture with IL-7 correlated inversely with CD4 T-cell counts and directly with Ki67 expression. Induction of pSTAT5 in CD4 T-cell subsets was greater in patients with normal CD4 T-cell counts. CD127 expression correlated inversely with proportions of CD4CD57 T cells, and pSTAT5 induction correlated inversely with CD4 T-cell expression of HLA-DR and CD57.

CONCLUSION

Defects of IL-7 signalling in HIV patients with persistent CD4 T-cell deficiency receiving ART are associated with CD4 T-cell activation and senescence.

HIV immune activation drives increased Eomes expression in memory CD8 T cells in association with transcriptional downregulation of CD127

BACKGROUND

During HIV infection distinct mechanisms drive immune activation of the CD4 and CD8 T cells leading to CD4 T-cell depletion and expansion of the CD8 T-cell pool. This immune activation is polyclonal and extends beyond HIV-specific T cells. One consequence of this immune activation is a profound decrease in IL-7Rα (CD127) expression on memory CD8 T cells. The mechanisms leading to this are unknown and because of the potential impact of reduced IL-7 signaling in memory T cells specific to HIV and other pathogens, in the present study we examined the molecular mechanisms implicated in this downregulation of CD127.

METHODS

Membrane bound (mIL7RA) and soluble (sIL7RA) mRNA expression was determined by qRT-PCR. CD127, Eomesodermin (Eomes) and T-bet expression in healthy controls and HIV-infected patients were studied by flow cytometry.

RESULTS

CD127 downregulation occurs at the transcriptional level for both mIL7RA and sIL7RA alternative spliced forms in the CD127 memory CD8 T cells. CD127 memory CD8 T cells exhibited increased Eomes expression and an 'effector-like' gene profile. These changes were associated with higher HIV-RNA levels. Following combination antiretroviral therapy (cART), there was an increase in CD127 expression over an extended period of time (>5 months) which was associated with decreased Eomes expression.

CONCLUSION

CD127 is downregulated at a transcriptional level in memory CD8 T cells in association with upregulation of Eomes expression.

Short communication: nuclear JAK3 and its involvement in CD4 activation in HIV-infected patients

The subcellular localization of JAK3 was examined by quantitative image analysis. For the first time, JAK3 was found to be located in the nuclei of primary CD4 lymphocytes. A comparable quantity of JAK3 was recovered in CD4 lymphocytes from healthy donors and HIV-infected patients. By contrast, far more phosphorylated JAK3 (pJAK3) was found in the nuclei of CD4 lymphocytes from HIV-infected patients than from healthy donors. The correlation detected between the quantity of pJAK3 in the nuclei of CD4 lymphocytes and the increase in HLA-DR at their surface suggests that pJAK3 may play a role in the deleterious immune activation characterizing HIV-infected patients.

Cell signalling analyses in the functional genomics era

The advancements in proteomics over the past decade have brought tremendous increases in sensitivity of mass spectrometry (MS) analyses and new technologies such as methods for quantitative MS and phosphoproteomics. The development of antibodies targeting a large fraction of the human proteome as well as specific antibodies that detect phosphorylations and other post-translational modifications now allows detection of a great variety of signalling marks. Combined with medium and high throughput methods for detecting many parallel signalling events such as phospho-flow cytometry analyses and MS-based analyses to identify signalling complexes, the available tools now allows analysis of whole signalling networks facilitating systems level understanding of cellular signalling. The even more recent advances in chemical biology and chemical proteomics are further enhancing the development in this area by providing a cache of small molecule compounds allowing perturbations of signal pathways further advancing our global understanding of the signal transduction dynamics at the single cell level as well as in cellular system, tissue and whole organs. This review highlights the recent advances of quantitative MS, phosphoflow cytometry and chemical biology with focus on the dynamic spatiotemporal phosphorylation events, and examples of their application.

Lymphopenia-driven homeostatic regulation of naive T cells in elderly and thymectomized young adults

Reduced thymopoiesis and continuous mobilization of naive T cells into the effector-memory pool can lead to severe alterations of the naive T cell compartment. However, maintenance of the naive T cell population is essential to mount effective immune responses. Evidence of homeostatic regulation of naive T cells is currently debated in animal models. In humans, the situation remains unresolved, in particular with advanced age. In this study, we analyzed the CD4(+) and CD8(+) naive T cell compartments from elderly, young adults thymectomized during early childhood, and HIV-1-infected patients, which are characterized by T lymphocytopenia. We show a direct association between increased turnover and decreased frequency of naive T cells. Moreover, the IL-7-induced pathway was fully functional in naive T cells from elderly and young adults thymectomized during early childhood, who are characterized by elevated IL-7 plasma levels. Our findings support the establishment of homeostatic regulation of naive T cell proliferation in humans. This regulation is particularly active in lymphopenic hosts, such as elderly and thymectomized patients.

The role of cytokines in the pathogenesis and treatment of HIV infection

HIV immune activation plays an important role in the immunopathogenesis of the disease. The mechanisms driving this immune activation are partially defined and likely are the result of multiple factors. The introduction of combination antiretroviral therapy (cART) has improved the life expectancy of HIV infected individuals, however there is evidence that in the setting of "undetectable" HIV-RNA plasma levels, there is some level of persistent immune activation in these patients. A better understanding of the immune activation pathways should be of value in developing complementary therapies to restore the immune systems of patients with HIV infection. This review discusses the cytokine mediated pathways of immune activation of the CD4 and CD8 T cell pools during HIV infection.

Foxo3a: an integrator of immune dysfunction during HIV infection

Chronic HIV infection, which is primarily characterized by the progressive depletion of total CD4(+) T cells, also causes persistent inflammation and immune activation. This is followed by profound changes in cellular and tissue microenvironments that often lead to prolonged immune dysfunction. The global nature of this immune dysfunction suggests that factors that are involved in immune cell survival, proliferation, differentiation and maturation are all affected. Of particular interest is the transcriptional factor Foxo3a that regulates a number of genes that are critical in the development and the maintenance of T and B cells, dendritic cells (DCs) and macrophages. Alterations in the microenvironment mediated by HIV infection cause significant increase in the transcriptional activity of Foxo3a; this has major impact on T cell and B cell immunity. In fact, recent findings from HIV infected individuals highlight three important points: (1) the alteration of Foxo3a signaling during HIV infection deregulates innate and adaptive immune responses; (2) Foxo3a-mediated effects are reversible and could be restored by interfering with the Foxo3a pathway; and (3) down-regulation of Foxo3a transcriptional activity in elite controllers (ECs) represents a molecular signature, or a correlate of immunity, associated with natural protection and lack of disease progression. In this review, we will discuss how HIV-infection altered microenvironments could result in impaired immune responses via the Foxo3a signaling pathway. Defining precisely the molecular mechanisms of how persistent inflammation and immune activation are able to influence the Foxo3a pathway could ultimately help in the development of novel approaches to improve immune responses in HIV infected subjects.

The role of naïve T-cells in HIV-1 pathogenesis: an emerging key player

Functional naïve T-cells are critical for an effective immune response to multiple pathogens. HIV leads to a significant reduction in CD4+ naïve T-cell number and impaired function and there is incomplete recovery following combination antiretroviral therapy (cART). Here we review the basic homeostatic mechanisms that maintain naïve CD4+ T-cells and discuss recent developments in understanding the impact of HIV infection on naïve CD4+ T-cells. Finally we review therapeutic interventions in HIV-infected individuals aimed at specifically enhancing recovery of naïve CD4+ T-cells.