Immune reconstitution disease: recent developments and implications for antiretroviral treatment in resource-limited settings

Nuclear Factor of Activated T Cells and Cytokines Gene Expression of the T Cells in AIDS Patients with Immune Reconstitution Inflammatory Syndrome during Highly Active Antiretroviral Therapy

Background. The etiology of immune reconstitution inflammatory syndrome (IRIS) in AIDS patients after the initiation of HAART remains unknown. Several researches indicated that the development of IRIS is associated with the production and variation of cytokines, whose gene expression are closely related to the Ca2⁺/CN-nuclear factor of activated T cells (NFAT) pathway. Methods. We studied the expression of NFAT isoforms and their major target cytokines genes in peripheral blood CD3⁺ T cells of subjects through fluorescence quantitative PCR and explored the expression changes of these genes before and after HAART. Results. After the initiation of HARRT, NFAT1, IL-6, and IL-8 gene expression showed a reversal trend in the CD3⁺ T cells of the IRIS group and changed from low expression before HARRT to high expression after HARRT. In particular, the relative gene expression of NFAT1 was markedly higher compared with the other three isoforms. The IRIS group also showed higher NFAT4, NFAT2, NFAT1, IL-1β, IL-10, IL-2, IL-18, and TNF-α gene expression than the non-IRIS group. Conclusion. This study suggested that high expression levels of IL-2, IL-6, IL-8, TNF-α, IL-1β, IL-10, IL-12, and IL-18 can predict the risk of IRIS. The increased expression of NFAT1 and NFAT4 may promote the expression of cytokines, such as IL-6, IL-8, and TNF-α, which may promote the occurrence of IRIS.

Mycobacterial antigen driven activation of CD14++CD16- monocytes is a predictor of tuberculosis-associated immune reconstitution inflammatory syndrome

Paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) is an aberrant inflammatory response occurring in a subset of TB-HIV co-infected patients initiating anti-retroviral therapy (ART). Here, we examined monocyte activation by prospectively quantitating pro-inflammatory plasma markers and monocyte subsets in TB-HIV co-infected patients from a South Indian cohort at baseline and following ART initiation at the time of IRIS, or at equivalent time points in non-IRIS controls. Pro-inflammatory biomarkers of innate and myeloid cell activation were increased in plasma of IRIS patients pre-ART and at the time of IRIS; this association was confirmed in a second cohort in South Africa. Increased expression of these markers correlated with elevated antigen load as measured by higher sputum culture grade and shorter duration of anti-TB therapy. Phenotypic analysis revealed the frequency of CD14⁺⁺CD16⁻ monocytes was an independent predictor of TB-IRIS, and was closely associated with plasma levels of CRP, TNF, IL-6 and tissue factor during IRIS. In addition, production of inflammatory cytokines by monocytes was higher in IRIS patients compared to controls pre-ART. These data point to a major role of mycobacterial antigen load and myeloid cell hyperactivation in the pathogenesis of TB-IRIS, and implicate monocytes and monocyte-derived cytokines as potential targets for TB-IRIS prevention or treatment.

Tuberculosis and HIV majorly impact host immune responses, resulting in immune deregulation and inflammation-driven tissue damage. Initiation of anti-retroviral therapy in patients with HIV-TB co-infection may result in immune reconstitution inflammatory syndrome (TB-IRIS), a disorder associated with increased immunopathology due to unfettered inflammation after CD4⁺ T-cell reconstitution. Monocytes are critical to the innate immune system and play an important role in several inflammatory conditions associated with chronic infections. Immunopathogenesis of TB-IRIS has been linked to activation of the adaptive immune response against opportunistic infection, yet the role of monocytes is still unknown. Here we investigated associations between soluble markers of monocyte activation, differential activation of monocyte subsets and TB-IRIS prospectively in two geographically distinct HIV-TB co-infected patient cohorts. Prior to ART initiation, patients who developed IRIS displayed a biosignature of elevated soluble monocyte activation markers, which were closely related to the mycobacterial antigen load in sputum samples. Amongst monocyte subsets, we observed that pre-ART circulating CD14⁺⁺CD16⁻ cell frequency independently predicted TB-IRIS and expanded during IRIS events. This monocyte subset was tightly associated with systemic markers of inflammation, and was found to produce inflammatory cytokines. Identification of this monocyte subset and its link with inflammation may lead to conception of novel therapies reducing immunopathology in TB-IRIS.

Incidence and risk factors of serious adverse events during antituberculous treatment in Rwanda: a prospective cohort study

Background

Tuberculosis (TB) and TB-human immunodeficiency virus infection (HIV) coinfection is a major public health concern in resource-limited settings. Although TB treatment is challenging in HIV-infected patients because of treatment interactions, immunopathological reactions, and concurrent infections, few prospective studies have addressed this in sub-Saharan Africa.

In this study we aimed to determine incidence, causes of, and risk factors for serious adverse events among patients on first-line antituberculous treatment, as well as its impact on antituberculous treatment outcome.

Methods and findings

Prospective observational cohort study of adults treated for TB at the Internal Medicine department of the Kigali University Hospital from May 2008 through August 2009.

Of 263 patients enrolled, 253 were retained for analysis: median age 35 (Interquartile range, IQR 28–40), 55% male, 66% HIV-positive with a median CD4 count 104 cells/mm³ (IQR 44–248 cells/mm³). Forty percent had pulmonary TB, 43% extrapulmonary TB and 17% a mixed form. Sixty-four (26%) developed a serious adverse event; 58/167 (35%) HIV-infected vs. 6/86 (7%) HIV-uninfected individuals. Commonest events were concurrent infection (n = 32), drug-induced hepatitis (n = 24) and paradoxical reactions/TB-IRIS (n = 23).

HIV-infection (adjusted Hazard Ratio, aHR 3.4, 95% Confidence Interval, CI 1.4–8.7) and extrapulmonary TB (aHR 2, 95%CI 1.1–3.7) were associated with an increased risk of serious adverse events. For TB/HIV co-infected patients, extrapulmonary TB (aHR 2.0, 95%CI 1.1–3.9) and CD4 count <100 cells/mm3 at TB diagnosis (aHR 1.7, 95%CI 1.0–2.9) were independent predictors. Adverse events were associated with an almost two-fold higher risk of unsuccessful treatment outcome at 6 months (HR 1.89, 95%CI 1.3–3.0).

Conclusion

Adverse events frequently complicate the course of antituberculous treatment and worsen treatment outcome, particularly in patients with extrapulmonary TB and advanced immunodeficiency. Concurrent infection accounts for most events. Our data suggest that deterioration in a patient already receiving antituberculous treatment should prompt an aggressive search for additional infections.

Multi-analyte profiling of ten cytokines in South African HIV-infected patients with Immune Reconstitution Inflammatory Syndrome (IRIS)

Background

Immune reconstitution inflammatory syndrome (IRIS) is an important complication of HAART in sub-Saharan Africa, where opportunistic infections (OIs) including mycobacteria and cryptococcus are common. The immune system's role in HIV infected patients is complex with cytokine expression strongly influencing HIV infection and replication.

Methods

We determined the expression patterns of 10 cytokines by Luminex multi-analyte profiling in 17 IRIS nested case-control pairs participating in a prospective South African cohort initiating anti-retroviral therapy.

Results

Interferon-gamma (IFN-γ) expression was significantly elevated in IRIS cases compared to controls (median 9.88 pg/ml versus 2.68 pg/ml, respectively, P = 0.0057), while other cytokines displayed non-significant differences in expression. Significant correlation was observed between IL-6, IL-10, and IFN-γ expression in the IRIS patients.

Conclusions

Significantly increased expression levels of IFN-γ suggest that this cytokine possibly plays a role in IRIS pathology and is a potential diagnostic marker.

Risk factors for immune reconstitution inflammatory syndrome under combination antiretroviral therapy can be aetiology-specific

In order to discriminate general from aetiology-specific risk factors for immune reconstitution inflammatory syndrome (IRIS), we followed up, during six months, 99 patients with advanced HIV infection commencing antiretroviral therapy (ART) without active opportunistic infections or evident inflammation. IRIS predictors were determined by univariate analysis using clinical data from 76 ART-responding patients either completing follow-up or developing IRIS, and by multivariate analysis of inflammation, disease progression and nutrition status variables. We identified 23 primary IRIS events (30.3%). Univariate predictors for all IRIS events were higher platelet counts and lower CD4/CD8 ratio, whereas subclinical inflammation was the multivariate predictor. Platelets, alkaline phosphatase levels and %CD8 T-cells in univariate analysis also predicted mycobacteria-associated IRIS independently, remaining elevated during follow-up. Herpesvirus IRIS was predicted by platelets and inflammation. Indicators of advanced HIV disease and subclinical inflammation jointly predict IRIS, and some are specific of the underlying microbial aetiology, possibly explaining previous reports.

Validation of a published case definition for tuberculosis-associated immune reconstitution inflammatory syndrome

OBJECTIVE

To evaluate the International Network for the Study of HIV-associated IRIS (INSHI) case definitions for tuberculosis (TB)-associated immune reconstitution inflammatory syndrome (IRIS) in a South African cohort.

METHODS

Prospective cohort of 498 adult HIV-infected patients initiating antiretroviral therapy. Patients were followed up for 24 weeks and all clinical events were recorded. Events with TB-IRIS as possible cause were assessed by consensus expert opinion and INSHI case definition. Positive, negative, and chance-corrected agreement (kappa) were calculated, and reasons for disagreement were assessed.

RESULTS

One hundred and two (20%) patients were receiving TB therapy at antiretroviral therapy initiation. Three hundred and thirty-three events were evaluated (74 potential paradoxical IRIS, 259 potential unmasking IRIS). Based on expert opinion, there were 18 cases of paradoxical IRIS associated with TB and/or other opportunistic disease. The INSHI criteria for TB-IRIS agreed in 13 paradoxical cases, giving positive agreement of 72.2%, negative agreement in 52/56 non-TB-IRIS events (92.9%), and kappa of 0.66. There were 19 unmasking TB-IRIS cases based on expert opinion, of which 12 were considered IRIS using the INSHI definition (positive agreement 63.2%). There was agreement in all 240 non-TB-IRIS events (negative agreement 100%) and kappa was 0.76.

CONCLUSION

There was good agreement between the INSHI case definition for both paradoxical and unmasking TB-IRIS and consensus expert opinion. These results support the use of this definition in clinical and research practice, with minor caveats in its application.

Immunopathogenesis of immune reconstitution disease in HIV patients responding to antiretroviral therapy

PURPOSE OF REVIEW

The aim of this article is to review the most recent literature regarding the immunopathogenesis of pathogen-associated immune reconstitution disease and to discuss the role of immune activation and various effector molecules and cells such as macrophages, effector and regulatory T cells, and natural killer cells in immune reconstitution disease.

RECENT FINDINGS

Many HIV patients receiving antiretroviral treatment develop immune reconstitution disease, which is characterized by exaggerated inflammatory immune responses to replicating or dead pathogens. In the majority of these cases, immune reconstitution disease is associated with restoration of pathogen-specific cellular immune responses involving CD4 or CD8 effector T cells. The precise conditions that trigger immune reconstitution disease have not yet been identified. Immune reconstitution disease patients have overt immune activation, which may be due to poor homeostatic control after the fast initial immune recovery in patients receiving antiretroviral therapy. Poor homeostatic control in immune reconstitution disease patients may be linked to unbalanced restoration of effector and regulatory T cells.

SUMMARY

Although the precise mechanism of immune reconstitution disease is not well understood, it is probably related to rapid restoration of pathogen-specific immune responses and poor homeostatic control that promote exaggerated immunopathological responses, especially if viable pathogens or pathogen debris are present at high concentrations.

Ocular immune reconstitution inflammatory syndromes

PURPOSE OF REVIEW

The aim of this article is to review the current literature concerning immune reconstitution inflammatory syndrome in relation to the eye. The definition, epidemiology, pathophysiology, risk factors, clinical features, diagnosis and treatment are discussed.

RECENT FINDINGS

Immune reconstitution inflammatory syndrome affecting the eye has been documented in association with cytomegalovirus retinitis following the introduction of highly active antiretroviral therapy in a large number of patients. This syndrome is referred to as immune recovery uveitis, which is presumed to be mediated by recovery of immune responses specific to residual cytomegalovirus antigen located in the eye. In addition to improved immunity itself, risk factors include a low CD4 T count at the time of initiation of highly active antiretroviral therapy and involvement of a larger proportion of retina. Immune recovery uveitis is a major cause of visual loss and morbidity among patients with AIDS who are receiving highly active antiretroviral therapy.

SUMMARY

Immune recovery uveitis is the most common form of immune reconstitution inflammatory syndrome in HIV-infected patients with cytomegalovirus retinitis who are receiving highly active antiretroviral therapy. Clear clinical definitions are required for ocular immune reconstitution inflammatory syndromes to avoid misclassification of other inflammatory conditions. A multidisciplinary approach is important in the diagnosis and management of immune recovery uveitis.

Immunologic markers as predictors of tuberculosis-associated immune reconstitution inflammatory syndrome in HIV and tuberculosis coinfected persons in Thailand

This study analyzes immunologic markers to predict and diagnose tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) in HIV and TB coinfected adults who initiated antiretroviral therapy (ART) in Thailand. T helper 1 cytokines interleukin (IL)-2, IL-12, and interferon-gamma (IFN-gamma) levels in response to PPD and RD1 antigens were assessed prior to ART, at weeks 6, 12, and 24 of treatment, and at time of TB-IRIS. Of 126 subjects, 22 (17.5%) developed TB-IRIS; 14 (64%) subjects received steroid treatment and 3 (14%) received NSAIDs; none of the subjects died. Median interval between ART initiation and TB-IRIS development was 14 days. IFN-gamma, IL-2, and IL-12 responses did not differ between TB-IRIS and no TB-IRIS subjects (p > 0.05). More research into the immunopathogenesis of TB-IRIS and diagnostic potential of cytokine markers is warranted.

Unmasked tuberculosis and tuberculosis immune reconstitution inflammatory disease: a disease spectrum after initiation of antiretroviral therapy

Antiretroviral therapy (ART) has beneficial effects on mortality and lowers the incidence of diseases caused by opportunistic infections, such as tuberculosis (TB). Although ART has sustained long-term benefits, the risk of TB is high during the first 3 months after ART initiation. Among cases of ART-associated TB, we define "unmasked TB" as that which occurs in patients with reactivation disease who develop clinically recognizable TB after ART with the restoration of previously acquired TB antigen-specific functional immune responses. TB cases with clinical evidence of an inflammatory syndrome are a subset of these unmasked cases, which we define as "unmasked TB-immune reconstitution inflammatory syndrome." With more widespread use of ART in areas with a high prevalence of TB, unmasked TB will likely become more common. TB diagnostics with improved sensitivity and specificity are urgently needed to detect subclinical TB before it is unmasked.

Changing mortality risk associated with CD4 cell response to antiretroviral therapy in South Africa

OBJECTIVE

To determine the relationship between mortality risk and the CD4 cell response to antiretroviral therapy (ART).

DESIGN

Observational community-based ART cohort in South Africa.

METHODS

CD4 cell counts were measured 4 monthly, and deaths were prospectively ascertained. Cumulative person-time accrued within a range of updated CD4 cell count strata (CD4 cell-strata) was calculated and used to derive CD4 cell-stratified mortality rates.

RESULTS

Patients (2423) (median baseline CD4 cell count of 105 cells/microl) were observed for up to 5 years of ART. One hundred and ninety-seven patients died during 3155 person-years of observation. In microltivariate analysis, mortality rate ratios associated with 0-49, 50-99, 100-199, 200-299, 300-399, 400-499 and at least 500 cells/microl updated CD4 cell-strata were 11.6, 4.9, 2.6, 1.7, 1.5, 1.4 and 1.0, respectively. Analysis of CD4 cell count recovery permitted calculations of person-time accrued within these CD4 cell-strata. Despite rapid immune recovery, high mortality in the first year of ART was related to the large proportion of person-time accrued within CD4 cell-strata less than 200 cells/microl. Moreover, patients with baseline CD4 cell counts less than 100 cells/microl had much higher cumulative mortality estimates at 1 and 4 years (11.6 and 16.7%) compared with those of patients with baseline counts of at least 100 cells/microl (5.2 and 9.5%) largely because of greater cumulative person-time at CD4 cell counts less than 200 cells/microl.

CONCLUSION

Updated CD4 cell counts are the variable most strongly associated with mortality risk during ART. High cumicrolative mortality risk is associated with person-time accrued at low CD4 cell counts. National HIV programmes in resource-limited settings should be designed to minimize the time patients spend with CD4 cell counts less than 200 cells/microl both before and during ART.

Immune reconstitution disease associated with parasitic infections following initiation of antiretroviral therapy

PURPOSE OF REVIEW

The aim of this article is to review the literature concerning immune reconstitution disease associated with parasitic infections during antiretroviral therapy.

RECENT FINDINGS

Immune reconstitution disease is most commonly associated with mycobacterial, chronic viral and invasive fungal infections. The spectrum of infections recognized to be associated with this phenomenon is expanding, however, and now includes a number of parasite infections (protozoal and helminthic). A total of 24 suspected cases have been reported in association with the following diseases: leishmaniasis in its various forms (visceral, cutaneous, mucosal and post-kala-azar dermal leishmaniasis), toxoplasmosis, cryptosporidiosis, schistosomiasis and strongyloidiasis. All cases associated with helminthic infections (schistosomiasis and strongyloidiasis) occurred in immigrants from tropical countries living in high-income countries; four of the patients with leishmaniasis were either immigrants or migrants who had moved out of endemic areas. As access to antiretroviral therapy expands in resource-limited settings, the clinical spectrum, frequency and impact of immune reconstitution disease associated with parasitic infections must be defined.

SUMMARY

Reports of immune reconstitution disease associated with parasitic infections are increasing, with many occurring in immigrants or migrants from areas where these diseases are endemic. The importance of such cases in antiretroviral therapy programmes in resource-limited settings, however, is not yet known.