Martyn A. French

Tuberculosis-associated immune reconstitution inflammatory syndrome: case definitions for use in resource-limited settings

The immune reconstitution inflammatory syndrome (IRIS) has emerged as an important early complication of antiretroviral therapy (ART) in resource-limited settings, especially in patients with tuberculosis. However, there are no consensus case definitions for IRIS or tuberculosis-associated IRIS. Moreover, previously proposed case definitions are not readily applicable in settings where laboratory resources are limited. As a result, existing studies on tuberculosis-associated IRIS have used a variety of non-standardised general case definitions. To rectify this problem, around 100 researchers, including microbiologists, immunologists, clinicians, epidemiologists, clinical trialists, and public-health specialists from 16 countries met in Kampala, Uganda, in November, 2006. At this meeting, consensus case definitions for paradoxical tuberculosis-associated IRIS, ART-associated tuberculosis, and unmasking tuberculosis-associated IRIS were derived, which can be used in high-income and resource-limited settings. It is envisaged that these definitions could be used by clinicians and researchers in a variety of settings to promote standardisation and comparability of data.

The genetic basis for the association of the 8.1 ancestral haplotype (A1, B8, DR3) with multiple immunopathological diseases

Summary: An individuals major histocompatibility complex (MHC) ancestral haplotype (AH) is the dearest single determinant of susceptibility to MHC associated immunopathological disease, as it defines the alleles carried at all loci in the MHC. However, the direct effects of any of the 150–200 genes that constitute the MHC are difficult to determine since recombination only occurs at defined hotspots. This review concerns the 8.1 AH (HLA‐A1, C7, B8, C4AQ0, C4B1, DR3, DQ2), which is carried by most Caucasians with HLA‐B8. It is associated with accelerated human immunodeficiency virus (HIV) disease, and susceptibility to insulin‐dependent diabetes mellitns (IDDM), systemic lupus erythematosus, dermatitis herpetiformis, common variable immunodeficiency and IgA deficiency, myasthenia gravis and several other conditions. We have mapped susceptibility genes for HIV, IDDM and myasthenia gravis co the central MHC between HLA‐B and the tumour necrosis factor or complement genes. Here we consider which of the remaining 8.1‐associated diseases are more closely associated with HLA‐DR3 and/or DQ2. Several candidate genes in the central MHC have the potential to modulate immune or inflammatory responses in an antigen‐independent manner, as is seen in studies of cultured cells from healthy carriers of the 8.1 AH. Hence these genes may act as a common co‐factor in the diverse immunopathological conditions associated with the 8.1 AH.

Hepatitis C virus-associated hepatitis following treatment of HIV-infected patients with HIV protease inhibitors: an immune restoration disease?

Objective:To report observations from case studies on the pathogenic mechanisms underlying the acute hepatitis that sometimes occurs in hepatitis C virus (HCV) and HIV coinfected patients following treatment with potent antiretroviral therapy that includes a HIV protease inhibitor. Methods:Cases of acute hepatitis were identified from a group of 133 patients enrolled in a retrospective study of pathogen-associated inflammatory disease following the use of potent antiretroviral therapy. Data on serum alanine aminotransferase concentrations, clinical events, HCV antibodies, and liver biopsies were collected from medical records. HCV RNA assays and additional HCV antibody assays were undertaken on stored plasma or sera. Results:Three of the 133 patients (2%) developed symptomatic hepatitis. One was HCV antibody-positive prior to commencing antiretroviral therapy and developed hepatitis subsequent to an episode of Mycobacterium avium complex disease associated with immune restoration. However, the other two patients had previously undiagnosed HCV infection for up to 2 years prior to antiretroviral therapy, with HCV RNA detected but anti-HCV antibody repeatedly undetectable in stored plasma or sera. HCV antibody was only detectable after antiretroviral therapy-induced decrease in plasma HIV RNA and immunological reconstitution. Plasma HCV RNA increased after therapy in one of these patients, but in the other the level was not increased at a time of active hepatitis demonstrated by liver biopsy. Conclusions:Hepatitis in HCV–HIV-coinfected patients following treatment with potent antiretroviral therapy may reflect restoration of anti-HCV immune responses rather than increased HCV replication or a hepatotoxic effect of antiretroviral therapy.

B cell-intrinsic signaling through IL-21 receptor and STAT3 is required for establishing long-lived antibody responses in humans.

Engagement of cytokine receptors by specific ligands activate Janus kinase–signal transducer and activator of transcription (STAT) signaling pathways. The exact roles of STATs in human lymphocyte behavior remain incompletely defined. Interleukin (IL)-21 activates STAT1 and STAT3 and has emerged as a potent regulator of B cell differentiation. We have studied patients with inactivating mutations in STAT1 or STAT3 to dissect their contribution to B cell function in vivo and in response to IL-21 in vitro. STAT3 mutations dramatically reduced the number of functional, antigen (Ag)-specific memory B cells and abolished the ability of IL-21 to induce naive B cells to differentiate into plasma cells (PCs). This resulted from impaired activation of the molecular machinery required for PC generation. In contrast, STAT1 deficiency had no effect on memory B cell formation in vivo or IL-21–induced immunoglobulin secretion in vitro. Thus, STAT3 plays a critical role in generating effector B cells from naive precursors in humans. STAT3-activating cytokines such as IL-21 thus underpin Ag-specific humoral immune responses and provide a mechanism for the functional antibody deficit in STAT3-deficient patients.

Immune Reconstitution Inflammatory Syndrome: A Reappraisal

Individuals with human immunodeficiency virus infection who commence antiretroviral therapy when they are very immunodeficient are susceptible to immune reconstitution disorders. The most common disorders are the various forms of immune restoration disease (IRD) that appear to result from the restoration of a dysregulated immune response against pathogen-specific antigens. Essentially, any pathogen that can cause an opportunistic infection as a result of cellular immunodeficiency can provoke IRD when pathogen-specific immune responses recover during antiretroviral therapy. In resource-poor countries, Mycobacterium tuberculosis and Cryptococcus neoformans are the most significant pathogens, because the former causes substantial morbidity and the latter causes substantial mortality. IRD associated with these pathogens is characterized by severe inflammatory responses and is often referred to as immune reconstitution inflammatory syndrome. Prevention and treatment strategies for IRD are being developed, but preliminary data have demonstrated the efficacy of corticosteroid therapy in severe cases. Immune reconstitution after antiretroviral therapy may also be associated with autoimmune disease or sarcoidosis, both of which appear to have an immunopathogenesis that is different from that of IRD.

Higher Levels of CRP, D-dimer, IL-6, and Hyaluronic Acid Before Initiation of Antiretroviral Therapy (ART) Are Associated With Increased Risk of AIDS or Death

BACKGROUND Substantial morbidity occurs during the first year of antiretroviral therapy (ART) in persons with advanced human immunodeficiency virus (HIV) disease despite HIV suppression. Biomarkers may identify high-risk groups. METHODS Pre-ART and 1-month samples from an initial ART trial were evaluated for biomarkers associated with AIDS events or death within 1-12 months. Case patients (n = 63) and control patients (n = 126) were 1:2 matched on baseline CD4 cell count, hepatitis status, and randomization date. All had ≥ 1 log(10) HIV RNA level decrease at 1 month. RESULTS Case patients had more frequent prior AIDS events, compared with control patients (P = .004), but similar HIV RNA levels at baseline. Pre-ART and 1-month C-reactive protein (CRP), D-dimer, and interleukin 6 (IL-6) levels and pre-ART hyaluronic acid (HA) levels were associated with new AIDS events or death (P ≤ .01). Patients who experienced immune reconstitution inflammatory syndrome (IRIS) events had higher pre-ART tumor necrosis factor α (TNF-α) and HIV RNA levels and significant 1-month increases in CRP, D-dimer, IL-6, interleukin 8, CXCL10, TNF-α, and interferon-γ levels, compared with patients who experienced non-IRIS events (P ≤ .03). Individuals with baseline CRP and HA levels above the cohort median (>2.1 mg/L and >50.0 ng/mL, respectively) had increased risk of AIDS or death (OR, 4.6 [95% CI, 2.0-10.3]; P < .001) and IRIS (OR, 8.7 [95% CI, 2.2-34.8] P = .002). CONCLUSIONS Biomarkers of Inflammation (CRP, IL-6), coagulation (D-dimer), and tissue fibrosis (HA) measured pre-ART and at 1 month are associated with higher risk of AIDS events, IRIS, or death, warranting additional study as risk stratification strategies.

HIV protease inhibitor substitution in patients with lipodystrophy : a randomized, controlled, open-label, multicentre study

BackgroundLipodystrophy, dyslipidaemia and insulin resistance often complicate protease inhibitor-containing antiretroviral therapy. The aims of this study were to determine if these are reversible with continued HIV suppression following protease inhibitor substitution. MethodsEighty-one HIV protease inhibitor recipients (78 male; mean antiretroviral therapy, 55 months) with predominant peripheral lipoatrophy, HIV RNA < 400 copies/ml plasma for at least the preceding 6 months, and no prior abacavir, non-nucleoside analogue or adefovir therapy were randomized 3 : 2 to continue nucleoside analogues and substitute protease inhibitor(s) with abacavir, nevirapine, adefovir and hydroxyurea (n = 49) or to continue all therapy (n = 32) with an option to switch at week 24. The primary endpoints were total body fat and HIV RNA at week 24. Other assessments were regimen safety, regional body composition, metabolic parameters, quality of life, and CD4 T-lymphocyte counts to week 48. ResultsThere was a greater decline in total body fat in the switch group than in the continue group (−1.6 and −0.4 kg, respectively at week 24;P = 0.006). This comprised greater declines in limb and subcutaneous abdominal fat, and in intra-abdominal fat of patients with moderate or severe abdominal fat accumulation. Viral suppression was similar, despite 18 (37%) switch group patients ceasing at least one study drug by week 24 because of adverse events. Total cholesterol and triglycerides declined more in the switch group (both P < 0.002). High density lipoprotein cholesterol increased significantly in both groups at week 48 (P < 0.02). There was no change for any glycaemic parameter. ConclusionsIn predominantly lipoatrophic patients, switching from HIV protease inhibitor therapy lead to improved lipids and less intra-abdominal fat, but also to less peripheral fat, and had minimal effect on insulin resistance. Virological control in these heavily pretreated patients was unaffected, despite frequent switch drug cessations.

Functional STAT3 deficiency compromises the generation of human T follicular helper cells

T follicular helper (Tfh) cells are critical for providing the necessary signals to induce differentiation of B cells into memory and Ab-secreting cells. Accordingly, it is important to identify the molecular requirements for Tfh cell development and function. We previously found that IL-12 mediates the differentiation of human CD4(+) T cells to the Tfh lineage, because IL-12 induces naive human CD4(+) T cells to acquire expression of IL-21, BCL6, ICOS, and CXCR5, which typify Tfh cells. We have now examined CD4(+) T cells from patients deficient in IL-12Rβ1, TYK2, STAT1, and STAT3 to further explore the pathways involved in human Tfh cell differentiation. Although STAT1 was dispensable, mutations in IL12RB1, TYK2, or STAT3 compromised IL-12-induced expression of IL-21 by human CD4(+) T cells. Defective expression of IL-21 by STAT3-deficient CD4(+) T cells resulted in diminished B-cell helper activity in vitro. Importantly, mutations in STAT3, but not IL12RB1 or TYK2, also reduced Tfh cell generation in vivo, evidenced by decreased circulating CD4(+)CXCR5(+) T cells. These results highlight the nonredundant role of STAT3 in human Tfh cell differentiation and suggest that defective Tfh cell development and/or function contributes to the humoral defects observed in STAT3-deficient patients.

Cryptococcal immune reconstitution inflammatory syndrome in HIV-1-infected individuals: proposed clinical case definitions

Cryptococcal immune reconstitution inflammatory syndrome (IRIS) may present as a clinical worsening or new presentation of cryptococcal disease after initiation of antiretroviral therapy (ART), and is thought to be caused by recovery of cryptococcus-specific immune responses. We have reviewed reports of cryptococcal IRIS and have developed a consensus case definition specifically for paradoxical crytopcoccal IRIS in patients with HIV-1 and known cryptococcal disease before ART, and a separate definition for incident cryptococcosis developed during ART (termed ART-associated cryptococcosis), for which a proportion of cases are likely to be unmasking cryptococcal IRIS. These structured case definitions are intended to aid design of future clinical, epidemiological, and immunopathological studies of cryptococcal IRIS, to standardise diagnostic criteria, and to facilitate comparisons between studies. As for definitions of tuberculosis-associated IRIS, definitions for cryptococcal IRIS should be regarded as preliminary until further insights into the immunopathology of IRIS permit their refinement.

Polymorphisms in cytokine genes define subpopulations of HIV-1 patients who experienced immune restoration diseases

Objective: To further elucidate the immunopathogenesis of immune restoration diseases (IRD) in HIV patients responding to antiretroviral therapy and determine whether IRD associated with different opportunistic pathogens involve distinct immunopathological mechanisms. Design: DNA samples from patients with a range of IRD were typed for polymorphic loci in genes encoding immune-mediators. Methods: PCR–restriction fragment length polymorphism assays were used to type loci in the IL1A, IL1B, IL6, TNFA and IL12B genes. Alleles of a microsatellite in the CD30 promoter were determined by capillary electrophoresis. Results: Only 8% of patients with IRD associated with a herpesvirus infection carried IL12B-3′UTR*2, compared with 42–54% of patients with other or no IRD. Patients with IRD arising from mycobacterial infection rarely carried IL6-174*C (36% versus 61–71%) and never carried TNFA-308*2 (0% versus 23–52%). TNFA-308*2 was carried by 52% of patients who experienced IRD associated with a herpesvirus infection, as several patients with exacerbations of cytomegalovirus retinitis carried this as part of a HLA-A2,B44 haplotype. Polymorphisms in IL1A, IL1B and CD30 showed no distinct patterns. Conclusions: Distinct cytokine-mediated mechanisms contribute to IRD initiated by herpesvirus and mycobacterial infections.