Pathogenesis and prevention of immune reconstitution disease during antiretroviral therapy

The immune reconstitution inflammatory syndrome: a clinical update

The immune reconstitution inflammatory syndrome (IRIS) is a well-described phenomenon in HIV-infected patients following initiation of antiretroviral therapy and can lead to significant morbidity and mortality in some patients. Risk for IRIS is enhanced in those with low CD4 counts and preexisting opportunistic infections. The development of pathogen-specific definitions of IRIS has aided classification of patients and has facilitated research. Newer data on optimal timing of ART initiation, with additional data in the setting of tuberculosis and cryptococcal meningitis, will help guide strategies to decrease the risk of IRIS but must balance the risks of HIV disease progression. Managing patients with IRIS can be challenging. Treatment options include pathogen-specific therapy, antiinflammatory therapies, and other novel approaches.

Management of the immune reconstitution inflammatory syndrome

The immune reconstitution inflammatory syndrome (IRIS) is a frequent early complication of antiretroviral therapy (ART) in patients with advanced HIV. Because there is no confirmatory diagnostic test, the diagnosis is based on clinical presentation and exclusion of alternative causes for deterioration, such as antimicrobial drug resistance. Opportunistic infection treatment should be optimized. Mild cases may require symptomatic therapy alone or nonsteroidal anti-inflammatory drugs. Corticosteroids have been used to treat more severe cases of IRIS associated with mycobacterial and fungal infections. There is evidence from a randomized controlled trial that prednisone reduces morbidity and improves symptoms in paradoxical tuberculosis (TB)-IRIS. Neurological TB-IRIS is potentially life-threatening; high-dose corticosteroids are indicated and ART interruption should be considered if level of consciousness is depressed. When considering corticosteroid treatment clinicians should be aware of their side effects and only use them when the diagnosis of IRIS is certain. In viral forms of IRIS corticosteroids are generally avoided.

Reducing deaths from tuberculosis in antiretroviral treatment programmes in sub-Saharan Africa

Mortality rates are high in antiretroviral therapy (ART) programmes in sub-Saharan Africa, especially during the first few months of treatment. Tuberculosis (TB) has been identified as a major underlying cause. Under routine programme conditions, between 5 and 40% of adult patients enrolling in ART services have a baseline diagnosis of TB. There is also a high TB incidence during the first few months of ART (much of which is prevalent disease missed by baseline screening) and long-term rates remain several-folds higher than background. We identify three groups of patients entering ART programmes for which different interventions are required to reduce TB-related deaths. First, diagnostic screening is needed in patients who have undiagnosed active TB so that timely anti-TB treatment can be started. This may be greatly facilitated by new diagnostic assays such as the Xpert MTB/RIF assay. Second, patients with a diagnosis of active TB need optimized case management, which includes early initiation of ART (with timing now defined by randomized controlled trials), trimethoprim-sulphamethoxazole prophylaxis and treatment of comorbidity. Third, all remaining patients who are TB-free at enrolment have high ongoing risk of developing TB and require preventive interventions, including optimized immune recovery (with ART ideally started early in the course of HIV infection), isoniazid preventive therapy and infection control to reduce infection risk. Further specific measures are needed to address multidrug-resistant TB (MDR-TB). Finally, scale-up of all these interventions requires nationally and locally tailored models of care that are patient-centred and provide integrated healthcare delivery for TB, HIV and other comorbidities.

Frequency, severity, and prediction of tuberculous meningitis immune reconstitution inflammatory syndrome

BACKGROUND

Tuberculosis immune reconstitution inflammatory syndrome (IRIS) is a common cause of deterioration in human immunodeficiency virus (HIV)-infected patients receiving tuberculosis treatment after starting antiretroviral therapy (ART). Potentially life-threatening neurological involvement occurs frequently and has been suggested as a reason to defer ART.

METHODS

We conducted a prospective study of HIV-infected, ART-naive patients with tuberculous meningitis (TBM). At presentation, patients started tuberculosis treatment and prednisone; ART was initiated 2 weeks later. Clinical and laboratory findings were compared between patients who developed TBM-IRIS (TBM-IRIS patients) and those who did not (non-TBM-IRIS patients). A logistic regression model was developed to predict TBM-IRIS.

RESULTS

Forty-seven percent (16/34) of TBM patients developed TBM-IRIS, which manifested with severe features of inflammation. At TBM diagnosis, TBM-IRIS patients had higher cerebrospinal fluid (CSF) neutrophil counts compared with non-TBM-IRIS patients (median, 50 vs 3 cells ×10(6)/L, P = .02). Mycobacterium tuberculosis was cultured from CSF of 15 TBM-IRIS patients (94%) compared with 6 non-TBM-IRIS patients (33%) at time of TBM diagnosis; relative risk of developing TBM-IRIS if CSF was Mycobacterium tuberculosis culture positive = 9.3 (95% confidence interval [CI], 1.4-62.2). The combination of high CSF tumor necrosis factor (TNF)-α and low interferon (IFN)-γ at TBM diagnosis predicted TBM-IRIS (area under the curve = 0.91 [95% CI, .53-.99]).

CONCLUSIONS

TBM-IRIS is a frequent, severe complication of ART in HIV-associated TBM and is characterized by high CSF neutrophil counts and Mycobacterium tuberculosis culture positivity at TBM presentation. The combination of CSF IFN-γ and TNF-α concentrations may predict TBM-IRIS and thereby be a means to individualize patients to early or deferred ART.

Pathogenesis of the immune reconstitution inflammatory syndrome in HIV-infected patients

PURPOSE OF REVIEW

The immune reconstitution inflammatory syndrome (IRIS) is an important clinical complication in HIV-infected patients initiating antiretroviral therapy. This review focuses on the latest literature pertaining to the pathogenesis of IRIS.

RECENT FINDINGS

The clinical manifestations of IRIS are heterogeneous due to the variety of opportunistic infections that are associated with this inflammatory syndrome. However, the disproportionate inflammation is a defining hallmark for which common mechanisms are suspected. Lymphopenia-induced proliferation in the context of systemic immune activation, presence of high antigenic exposure and a wider availability of interleukin-7 contribute to the exacerbated immune response underlying IRIS. Defect in pathogen clearance by phagocytes might favor high pathogen burden, which in turn is thought to activate both innate immune cells and pathogen-specific T cells upon correction of the CD4 T-cell lymphopenia, predisposing to IRIS. This common scenario might be further invigorated by functional impairments among regulatory T cells.

SUMMARY

Further insight into the cellular mechanisms driving IRIS is urgently needed. Understanding the relative contribution of distinct effector and regulatory T-cell subsets, and innate immune components to IRIS is required to inspire future therapeutic approaches.

Immune reconstitution inflammatory syndrome and the influence of T regulatory cells: a cohort study in The Gambia

Objective

The factors associated with the development of immune reconstitution inflammatory syndrome in HIV patients commencing antiretroviral therapy have not been fully elucidated. Using a longitudinal study design, this study addressed whether alteration in the levels of T regulatory cells contributed to the development of IRIS in a West African cohort of HIV-1 and HIV-2 patients. Seventy-one HIV infected patients were prospectively recruited to the study and followed up for six months. The patients were categorized as IRIS or non-IRIS cases following published clinical guidelines. The levels of T regulatory cells were measured using flow cytometry at baseline and all follow-up visits. Baseline cytokine levels of IL-2, IL-6, IFN-γ, TNF-α, MIP-1β, IL-1, IL-12, IL-13, and IL-10 were measured in all patients.

Results

Twenty eight percent of patients (20/71) developed IRIS and were predominantly infected with HIV-1. Patients developing IRIS had lower nadir CD4 T cells at baseline (p = 0.03) and greater CD4 T cell reconstitution (p = 0.01) at six months post-ART. However, the development of IRIS was not influenced by the levels of T regulatory cells. Similarly, baseline cytokine levels did not predict the onset of IRIS.

Conclusion

The development of IRIS was not associated with differences in levels of T regulatory cells or baseline pro-inflammatory cytokines.

[Immune reconstitution syndrome]

The immune reconstitution inflammatory syndrome (IRIS) represents a heterogeneous group of conditions. Whilst they typically present in HIV-infected patients with advanced immunodeficiency, IRIS have also been described in HIV-negative patients with immune reconstitution due to other causes of immunosuppression. Frequently IRIS results from an immune response against underlying infection (pathogen-associated IRIS). However, IRIS might become evident during immune reconstitution without an underlying pathogen such as a sarcoid-like illness or an autoimmune thyropathy. Here we report on the epidemiology and risk factors of IRIS along with diagnosis and management of this clinically important inflammatory syndrome.

Impact of immune reconstitution inflammatory syndrome on antiretroviral therapy adherence

OBJECTIVE

We determined the impact of immune reconstitution inflammatory syndrome (IRIS) on antiretroviral therapy (ART) adherence in a cohort of 274 human immunodeficiency virus (HIV)-infected South African adults initiating ART.

METHODS

We carried out a secondary analysis of data from a randomized controlled trial of partially supervised ART in Cape Town, South Africa. Monthly pill count adherence, viral suppression (HIV viral load < 50 c/mL), and IRIS events were documented. Poisson regression was used to identify variables associated with ART adherence below the median in the first 6 months of ART.

RESULTS

We enrolled 274 patients: 58% women, median age 34 years, median CD4 count 98 cells/μL, 46% World Health Organization clinical stage IV, and 40% on treatment for tuberculosis (TB). IRIS and TB-IRIS developed in 8.4% and 6.6% of patients, respectively. The median cumulative adherence at 6 months for those with an IRIS event vs no IRIS was 95.5% vs 98.2% (P = 0.04). Although not statistically significant, patients developing IRIS had a lower 6-month viral load suppression than those without IRIS (68% vs 80%, P = 0.32). ART adherence below the median of 98% was independently associated with alcohol abuse (relative risk [RR] 1.5; 95% confidence interval [CI] 1.2-1.9; P = 0.003) and IRIS events (RR 1.7; 95% CI 1.2-2.2; P = 0.001).

CONCLUSION

Although IRIS events were associated with slightly lower adherence rates, overall adherence to ART remained high in this study population. Concerns about IRIS should not deter clinicians from early ART initiation.