Immune restoration after antiretroviral therapy: the pitfalls of hasty or incomplete repairs

Influence of the timing of antiretroviral therapy on the potential for normalization of immune status in human immunodeficiency virus 1-infected individuals

IMPORTANCE

In individuals with human immunodeficiency virus 1 (HIV-1) infection who are receiving antiretroviral therapy (ART), factors that promote full immune recovery are not well characterized.

OBJECTIVE

To investigate the influence of the timing of ART relative to HIV-1 infection on normalization of CD4+ T-cell counts, AIDS risk, and immune function.

DESIGN, SETTING, AND PARTICIPANTS

Participants in the observational US Military HIV Natural History Study with documented estimated dates of seroconversion (EDS) who achieved virologic suppression with ART were evaluated. Markers indicative of immune activation, dysfunction, and responsiveness were determined. Responses to hepatitis B virus (HBV) vaccine, an indicator of in vivo immune function, were also assessed. The timing of ART was indexed to the EDS and/or entry into the cohort. The CD4+ counts in HIV-1-uninfected populations were surveyed.

MAIN OUTCOMES AND MEASURES

Normalization of CD4+ counts to 900 cells/μL or higher, AIDS development, HBV vaccine response, as well as T-cell activation, dysfunction, and responsiveness.

RESULTS

The median CD4+ count in HIV-1-uninfected populations was approximately 900 cells/μL. Among 1119 HIV-1-infected participants, CD4+ normalization was achieved in 38.4% vs 28.3% of those initiating ART within 12 months vs after 12 months from the EDS (P = .001). Incrementally higher CD4+ recovery (<500, 500-899, and ≥900 cells/μL) was associated with stepwise decreases in AIDS risk and reversion of markers of immune activation, dysfunction, and responsiveness to levels approximating those found in HIV-1-uninfected persons. Participants with CD4+ counts of 500 cells/μL or higher at study entry (adjusted odds ratio [aOR], 2.00; 95% CI, 1.51-2.64; P < .001) or ART initiation (aOR, 4.08; 95% CI, 3.14-5.30; P < .001) had significantly increased CD4+ normalization rates compared with other participants. However, even among individuals with a CD4+ count of 500 cells/μL or higher at both study entry and before ART, the odds of CD4+ normalization were 80% lower in those initiating ART after 12 months from the EDS and study entry (aOR, 0.20; 95% CI, 0.07-0.53; P = 001). Initiation of ART within 12 months of EDS vs later was associated with a significantly lower risk of AIDS (7.8% vs 15.3%; P = .002), reduced T-cell activation (percent CD4+HLA-DR+ effector memory T cells, 12.0% vs 15.6%; P = .03), and increased responsiveness to HBV vaccine (67.9% vs 50.9%; P = .07).

CONCLUSIONS AND RELEVANCE

Deferral of ART beyond 12 months of the EDS diminishes the likelihood of restoring immunologic health in HIV-1-infected individuals.

Antigen-specific interferon-gamma responses and innate cytokine balance in TB-IRIS

Background

Tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) remains a poorly understood complication in HIV-TB patients receiving antiretroviral therapy (ART). TB-IRIS could be associated with an exaggerated immune response to TB-antigens. We compared the recovery of IFNγ responses to recall and TB-antigens and explored in vitro innate cytokine production in TB-IRIS patients.

Methods

In a prospective cohort study of HIV-TB co-infected patients treated for TB before ART initiation, we compared 18 patients who developed TB-IRIS with 18 non-IRIS controls matched for age, sex and CD4 count. We analyzed IFNγ ELISpot responses to CMV, influenza, TB and LPS before ART and during TB-IRIS. CMV and LPS stimulated ELISpot supernatants were subsequently evaluated for production of IL-12p70, IL-6, TNFα and IL-10 by Luminex.

Results

Before ART, all responses were similar between TB-IRIS patients and non-IRIS controls. During TB-IRIS, IFNγ responses to TB and influenza antigens were comparable between TB-IRIS patients and non-IRIS controls, but responses to CMV and LPS remained significantly lower in TB-IRIS patients. Production of innate cytokines was similar between TB-IRIS patients and non-IRIS controls. However, upon LPS stimulation, IL-6/IL-10 and TNFα/IL-10 ratios were increased in TB-IRIS patients compared to non-IRIS controls.

Conclusion

TB-IRIS patients did not display excessive IFNγ responses to TB-antigens. In contrast, the reconstitution of CMV and LPS responses was delayed in the TB-IRIS group. For LPS, this was linked with a pro-inflammatory shift in the innate cytokine balance. These data are in support of a prominent role of the innate immune system in TB-IRIS.

Monocyte-activation phenotypes are associated with biomarkers of inflammation and coagulation in chronic HIV infection

BACKGROUND

Soluble biomarkers of inflammation predict non-AIDS related morbidity and mortality among human immunodeficiency virus (HIV)-infected persons. Exploring associations between plasma biomarkers and cellular phenotypes may identify sources of excess inflammation.

METHODS

Plasma biomarkers (interleukin 6 [IL-6] level, D-dimer level, high-sensitivity C-reactive protein [hsCRP] level, soluble CD14 [sCD14] level, and soluble CD163 [sCD163] level) were measured from cryopreserved samples from the Study to Understand the Natural History of HIV/AIDS in the Era of Effective Therapy (SUN Study). We performed immunophenotyping of peripheral blood mononuclear cells for markers of T-cell and monocyte activation, maturation, and migration. We evaluated associations between cellular phenotypes and soluble biomarkers by Spearman rank correlation and multivariate linear regression.

RESULTS

Participants' (n = 670) median age was 41 years, 88% were prescribed antiretroviral therapy, 72% had a plasma HIV RNA load of <400 copies/mL, and the median CD4(+) T-lymphocyte count was 471 cells/µL. After adjustment, CD14(++)CD16(+) monocytes were associated with higher levels of IL-6, hsCRP, and sCD163; associations with IL-6 and hsCRP persisted in persons with suppressed HIV replication. While CCR5(+) monocytes positively associated with D-dimer levels, CCR2(+) monocytes were inversely associated with hsCRP levels.

CONCLUSIONS

Plasma inflammatory biomarkers that predict morbidity and mortality were strongly associated with monocyte activation and migration, modestly associated with T-cell maturation, and not associated with CD8(+) T-cell activation phenotypes. These findings suggest that strategies to control monocyte activation warrant further investigation.

Can early therapy reduce inflammation?

PURPOSE OF REVIEW

Serious non-AIDS events or noninfectious complications of HIV infection far outnumber AIDS events in the current combination antiretroviral therapy (ART) era and are attributed to chronic inflammation. Thus, a better understanding of why inflammation persists on ART will assist in developing better therapeutic strategies, including optimal timing of ART initiation.

RECENT FINDINGS

Markers of inflammation and coagulation, such as D-dimer, interleukin-6, C-reactive protein, soluble CD14, and soluble CD163, predict end-organ disease and mortality, whereas markers of T-cell activation appear more predictive of CD4 T-cell decline, AIDS events, or response to therapy. Initiating ART at high CD4 T-cell counts can result in less inflammation as supported by studies in acute and early HIV infection, but antiretroviral drugs may differentially affect inflammatory pathways. Decreasing inflammation in HIV-uninfected individuals may decrease morbidity, but long-term outcomes studies in HIV-infected individuals are lacking.

SUMMARY

Circulating biomarkers of inflammation are among the strongest predictors of non-AIDS outcomes in treated HIV infection. With additional investigation, they may serve in the future as specific end-organ disease surrogate endpoints and may help identify those patients at highest risk of non-AIDS events who may benefit from either early ART and/or potential adjuvant anti-inflammatory therapies.

Human immunodeficiency virus-associated dementia: a link between accumulation of viral proteins and neuronal degeneration

In the late stage of human immunodeficiency virus-1 (HIV) infection, a subset of individuals develops HIV associated neurocognitive disorders (HAND), which in its severe form, is characterized by motor and cognitive dysfunction. Dendritic pruning, synaptic abnormalities and neuronal apoptosis are observed in these patients. There are numerous advances in our understanding of HIV interactions with cells of the central nervous system. However, the underlying causes of neurological symptoms and pathological alterations observed in HIV positive subjects are poorly understood. Moreover, little is still known about the molecular mechanisms by which HIV induces synaptic dysfunction and degeneration. HAND resembles other common neurological diseases such as Alzheimer's and Huntington's diseases. These neurodegenerative disorders are characterized by accumulation of toxic proteins such as tau and huntingtin, respectively, which promote axonal degeneration by impairing axonal transport. Axonal degeneration precedes neuronal death. Therefore, a better understanding of the mechanisms whereby HIV triggers axonal degeneration has potential implications for developing therapeutic compounds to prevent synaptic failure in HAND. This article highlights and reviews evidence showing that neuronal accumulation of viral proteins promotes axonal damage.