The immunopathogenesis of the HIV tuberculosis immune reconstitution inflammatory syndrome

[Paradoxical tuberculosis reaction]

Paradoxical tuberculosis reaction is defined as the aggravation of lesions present at diagnosis or the development of new lesions under anti-tuberculosis treatment, after exclusion of other alternate causes. It affects 5 to 30% of tuberculosis patients, with a variable prevalence depending on the site of infection and the clinical background. The diagnosis of paradoxical reaction is one of elimination, and requires having ruled out therapeutic failure, notably linked to poor compliance and/or to the presence of mycobacterial antibiotic resistance. The severity of paradoxical tuberculosis reaction lies in its neurological impairment. Despite its clinical importance, the mechanisms involved remain poorly understood and its management is not consensual. Corticosteroids are the cornerstone in the medical management. The role of anti-TNF agents, currently proposed in cases of corticodependence or corticoresistance, remains to be properly defined.

A novel multi-component protein vaccine ECP001 containing a protein polypeptide antigen nPstS1 riching in T-cell epitopes showed good immunogenicity and protection in mice

Tuberculosis (TB) is an infectious disease that seriously affects human health. Until now, the only anti-TB vaccine approved for use is the live attenuated Mycobacterium bovis (M. bovis) vaccine - BCG vaccine, but its protective efficacy is relatively low and does not provide satisfactory protection against TB in adults. Therefore, there is an urgent need for more effective vaccines to reduce the global TB epidemic. In this study, ESAT-6, CFP-10, two antigens full-length and the T-cell epitope polypeptide antigen of PstS1, named nPstS1, were selected to form one multi-component protein antigens, named ECP001, which include two types, one is a mixed protein antigen named ECP001m, the other is a fusion expression protein antigen named ECP001f, as candidates for protein subunit vaccines. were prepared by constructing one novel subunit vaccine by mixing or fusing the three proteins and combining them with aluminum hydroxide adjuvant, and the immunogenicity and protective properties of the vaccine was evaluated in mice. The results showed that ECP001 stimulated mice to produce high titre levels of IgG, IgG1 and IgG2a antibodies; meanwhile, high levels of IFN-γ and a broad range of specific cytokines were secreted by mouse splenocytes; in addition, ECP001 inhibited the proliferation of Mycobacterium tuberculosis in vitro with a capacity comparable to that of BCG. It can be concluded that ECP001 is a novel effective multicomponent subunit vaccine candidate with potential as BCG Initial Immunisation-ECP001 Booster Immunisation or therapeutic vaccine for M. tuberculosis infection.

Immune reconstitution inflammatory syndrome in non-HIV cryptococcal meningitis: Cross-talk between pathogen and host

BACKGROUND

Cryptococcal meningitis (CM)-associated immune reconstitution inflammatory syndrome (IRIS) is associated with high mortality, the epidemiology and pathophysiology of which is poorly understood, especially in non-HIV populations.

OBJECTIVES

We aim to explore the incidence, clinical risk factors, immunological profiles and potential influence of leukotriene A4 hydroxylase (LTA4H) on non-HIV CM IRIS populations.

METHODS

In this observational cohort study, 101 previously untreated non-HIV CM patients were included. We obtained data for clinical variables, 27 cerebrospinal fluid (CSF) cytokines levels and LTA4H genotype frequencies. Changes of CSF cytokines levels before and at IRIS occurrence were compared.

RESULTS

Immune reconstitution inflammatory syndrome was identified in 11 immunocompetent males, generating an incidence of 10.9% in non-HIV CM patients. Patients with higher CrAg titres (> 1:160) were more likely to develop IRIS, and titre of 1:1280 is the optimum level to predict IRIS occurrence. Baseline CSF cytokines were significantly higher in IRIS group, which indicated a severe host immune inflammation response. Four LTA4H SNPs (rs17525488, rs6538697, rs17525495 and rs1978331) exhibited significant genetic susceptibility to IRIS in overall non-HIV CM, while five cytokines were found to be associated with rs1978331, and baseline monocyte chemotactic protein 1 (MCP-1) became the only cytokine correlated with both IRIS and LTA4H SNPs.

CONCLUSIONS

Our study suggested that non-HIV CM patients with high fungal burden and severe immune inflammation response were more likely to developed IRIS. LTA4H polymorphisms may affect the pathogenesis of IRIS by regulating the level of baseline CSF MCP-1.

Perspectives and Advances in the Understanding of Tuberculosis

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), remains a leading cause of death due to infection in humans. To more effectively combat this pandemic, many aspects of TB control must be developed, including better point of care diagnostics, shorter and safer drug regimens, and a protective vaccine. To address all these areas of need, better understanding of the pathogen, host responses, and clinical manifestations of the disease is required. Recently, the application of cutting-edge technologies to the study of Mtb pathogenesis has resulted in significant advances in basic biology, vaccine development, and antibiotic discovery. This leaves us in an exciting era of Mtb research in which our understanding of this deadly infection is improving at a faster rate than ever, and renews hope in our fight to end TB. In this review, we reflect on what is known regarding Mtb pathogenesis, highlighting recent breakthroughs that will provide leverage for the next leaps forward in the field.

JC Polyomavirus, progressive multifocal leukoencephalopathy and immune reconstitution inflammatory syndrome: a review

The human neurotropic virus JC Polyomavirus, a member of the Polyomaviridae family, is the opportunistic infectious agent causing progressive multifocal leukoencephalopathy, typically in immunocompromised individuals. The spectrum of underlying reasons for the systemic immunosuppression that permits JCV infection in the central nervous system has evolved over the past 2 decades, and therapeutic immunosuppression arousing JCV infection in the brain has become increasingly prominent as a trigger for PML. Effective immune restoration subsequent to human immunodeficiency virus-related suppression is now recognized as a cause for unexpected deterioration of symptoms in patients with PML, secondary to a rebound inflammatory phenomenon called immune reconstitution inflammatory syndrome, resulting in significantly increased morbidity and mortality in a disease already infamous for its lethality. This review addresses current knowledge regarding JC Polyomavirus, progressive multifocal leukoencephalopathy, progressive multifocal leukoencephalopathy-related immune reconstitution inflammatory syndrome, and the immunocompromised states that incite JC Polyomavirus central nervous system infection, and discusses prospects for the future management of these conditions.

Cryptococcosis-Associated Immune Reconstitution Inflammatory Syndrome Is Associated With Dysregulation of IL-7/IL-7 Receptor Signaling Pathway in T Cells and Monocyte Activation

BACKGROUND

Systemic levels of interleukin (IL)-7 at antiretroviral therapy (ART) initiation have previously been shown to be predictive of HIV-linked paradoxical cryptococcosis-associated immune reconstitution inflammatory syndrome (C-IRIS). We therefore explored IL-7/IL-7 receptor (IL-7/IL-7R) signaling pathway dysfunction, with related alterations in immune function, as a mechanism underlying C-IRIS.

METHOD

HIV-infected patients with cryptococcal meningitis who experienced C-IRIS (n = 27) were compared with CD4 T-cell count-matched counterparts without C-IRIS (n = 27), after antifungal therapy and pre-ART initiation. Flow cytometry was used to assess T-cell and monocyte phenotypes and functions.

RESULTS

Proportions of IL-7R+ CD4 or CD8 T cells correlated positively with CD4 T-cell counts and proportions of central memory and naive CD4 and CD8 T-cell pre-ART (all r > 0.50 and P < 0.05); however, the former negatively correlated with CD4 T-cell counts fold-increase on ART in non-C-IRIS but not C-IRIS patients. Higher frequencies of activated monocytes (CD14CD86 or CD14+HLA-DR+; P ≤ 0.038) were also observed in C-IRIS compared with non-C-IRIS patients, and those who failed to clear cryptococci from cerebrospinal fluid before ART had higher levels of activated monocytes (CD14+HLA-DR+, P = 0.017) compared with those who cleared. In multivariate regression, CD14+HLA-DR+ monocytes were independently associated with C-IRIS [hazard ratio = 1.055 (1.013-1.098); P = 0.009].

CONCLUSION

In contrast to non-C-IRIS patients, C-IRIS patients displayed a lack of association between proportions of IL-7R+ T cells and several markers of T-cell homeostasis. They also exhibited higher monocyte activation linked to cerebrospinal fluid cryptococcal culture positivity before ART. These data suggest a role for IL-7/IL-7R signaling pathway dysregulation in the pathogenesis of C-IRIS, possibly linked to monocyte activation and residual pathogen burden before ART.

Changes in the NK Cell Repertoire Related to Initiation of TB Treatment and Onset of Immune Reconstitution Inflammatory Syndrome in TB/HIV Co-infected Patients in Rio de Janeiro, Brazil-ANRS 12274

Tuberculosis (TB) is the most common comorbidity and the leading cause of death among HIV-infected individuals. Although the combined antiretroviral therapy (cART) during TB treatment improves the survival of TB/HIV patients, the occurrence of immune reconstitution inflammatory syndrome (IRIS) in some patients poses clinical and scientific challenges. This work aimed to evaluate blood innate lymphocytes during therapeutic intervention for both diseases and their implications for the onset of IRIS. Natural killer (NK) cells, invariant NKT cells (iNKT), γδ T cell subsets, and in vitro NK functional activity were characterized by multiparametric flow cytometry in the following groups: 33 TB/HIV patients (four with paradoxical IRIS), 27 TB and 25 HIV mono-infected subjects (prior to initiation of TB treatment and/or cART and during clinical follow-up to 24 weeks), and 25 healthy controls (HC). Concerning the NK cell repertoire, several activation and inhibitory receptors were skewed in the TB/HIV patients compared to those in the other groups, especially the HCs. Significantly higher expression of CD158a (p = 0.025), NKp80 (p = 0.033), and NKG2C (p = 0.0076) receptors was detected in the TB/HIV IRIS patients than in the non-IRIS patients. Although more NK degranulation was observed in the TB/HIV patients than in the other groups, the therapeutic intervention did not alter the frequency during follow-up (weeks 2-24). A higher frequency of the γδ T cell population was observed in the TB/HIV patients with inversion of the Vδ2⁺/Vδ2^- ratio, especially for those presenting pulmonary TB, suggesting an expansion of particular γδ T subsets during TB/HIV co-infection. In conclusion, HIV infection impacts the frequency of circulating NK cells and γδ T cell subsets in TB/HIV patients. Important modifications of the NK cell repertoire were observed after anti-TB treatment (week 2) but not during the cART/TB follow-up (weeks 6-24). An increase of CD161⁺ NK cells was related to an unfavorable outcome. Despite the low number of cases, a more preserved NK cell profile was detected in IRIS patients previous to treatment, suggesting a role for these cells in IRIS onset. Longitudinal evaluation of the NK repertoire showed the impact of TB treatment and implicated these cells in TB pathogenesis in TB/HIV co-infected patients.

Plasma But Not Cerebrospinal Fluid Interleukin 7 and Interleukin 5 Levels Pre-Antiretroviral Therapy Commencement Predict Cryptococcosis-Associated Immune Reconstitution Inflammatory Syndrome

Background

Patients with human immunodeficiency virus/AIDS-associated cryptococcal meningitis (CM) frequently experience clinical deterioration, known as cryptococcosis-associated immune reconstitution inflammatory syndrome (C-IRIS), upon initiation of antiretroviral therapy (ART). The immunological mechanisms underlying C-IRIS are incompletely defined and no reliable predictive biomarkers exist. We investigated whether plasma or cerebrospinal fluid (CSF) levels of cytokines and chemokines predicted C-IRIS and are potential predictive biomarkers.

Methods

Patients with CM who experienced C-IRIS (N = 27) upon ART initiation were compared to CD4+ T-cell count-matched patients without C-IRIS (N = 27). Plasma and CSF collected pre-ART were assayed for cytokines and chemokines using a 17-plex Luminex kit or enzyme-linked immunosorbent assay. Cox proportional hazards regression and principal component analyses were also performed.

Results

Plasma interleukin (IL) 2, IL-4, IL-5, IL-7, IL-17, interferon-γ, and tumor necrosis factor-α levels were higher in C-IRIS patients compared to controls (all P < .05), with IL-5 and IL-7 significant after Bonferroni-Holm correction. In multivariate Cox proportional hazards regression, high IL-5 (hazard ratio [HR], 5.76 [95% confidence interval {CI}, .77-43.0]; P = .088) and IL-7 (HR, 9.30 [95% CI, 1.96-44.0]; P = .005) were predictive of C-IRIS. Plasma IL-5 (P = .0008) and IL-10 (P = .0089) were lower in those who achieved CSF cryptococcal culture negativity compared to those with positive cultures pre-ART. There were no significant differences in CSF cytokine or chemokine levels between cases and controls.

Conclusions

High plasma IL-5 and IL-7 levels pre-ART were associated with increased risk of developing C-IRIS. High IL-5 levels may reflect a Th2 environment associated with impaired clearance of cryptococci while high IL-7 levels may reflect IL-7/IL-7R pathway dysfunction in T cells, both of which could be associated with C-IRIS immunopathogenesis.

Risk factors and frequency of tuberculosis-associated immune reconstitution inflammatory syndrome among HIV/Tuberculosis co-infected patients in Southern India

Immune reconstitution inflammatory syndrome (IRIS) continues to be a complication in HIV/tuberculosis (TB) co-infected patients initiating highly active antiretroviral therapy (HAART). The aim of this study was to evaluate the risk factors associated with developing IRIS to identify a possible biomarker to predict or diagnose IRIS in patients initiating HAART. A total of 175 HIV/TB co-infected patients initiating HAART were followed up longitudinally during September 2010 to May 2013 attending a HIV care clinic in Chennai. Patients were followed up longitudinally after HAART initiation and baseline demographic, laboratory parameters and treatment characteristics between patients with IRIS events and those without IRIS events were compared. Chi-square or Fisher's exact test for categorical variables and a Wilcoxon rank-sum test for continuous variables were performed using SPSS, version 12.0 software. Patients with IRIS had a significantly lower median baseline CD4+ T-cell count (P = 0.0039). There were no differences in terms of sex, CD4 T-cell %, plasma viral load, time interval between initiating ATT and HAART between the IRIS and non-IRIS patients. Low CD4+ T-cell count (<100 cells/μL) could be used as a marker to screen and monitor patients initiating HAART.

Neutrophil Activation and Enhanced Release of Granule Products in HIV-TB Immune Reconstitution Inflammatory Syndrome

BACKGROUND

Tuberculosis immune reconstitution inflammatory syndrome (TB-IRIS) remains incompletely understood. Neutrophils are implicated in tuberculosis pathology but detailed investigations in TB-IRIS are lacking. We sought to further explore the biology of TB-IRIS and, in particular, the role of neutrophils.

SETTING

Two observational, prospective cohort studies in HIV/TB coinfected patients starting antiretroviral therapy (ART), 1 to analyze gene expression and subsequently 1 to explore neutrophil biology.

METHODS

nCounter gene expression analysis was performed in patients with TB-IRIS (n = 17) versus antiretroviral-treated HIV/TB coinfected controls without IRIS (n = 17) in Kampala, Uganda. Flow cytometry was performed in patients with TB-IRIS (n = 18) and controls (n = 11) in Cape Town, South Africa to determine expression of neutrophil surface activation markers, intracellular cytokines, and human neutrophil peptides (HNPs). Plasma neutrophil elastase and HNP1-3 were quantified using enzyme-linked immunosorbent assay. Lymph node immunohistochemistry was performed on 3 further patients with TB-IRIS.

RESULTS

There was a significant increase in gene expression of S100A9 (P = 0.002), NLRP12 (P = 0.018), COX-1 (P = 0.025), and IL-10 (P = 0.045) 2 weeks after ART initiation in Ugandan patients with TB-IRIS versus controls, implicating neutrophil recruitment. Patients with IRIS in both cohorts demonstrated increases in blood neutrophil count, plasma HNP and elastase concentrations from ART initiation to week 2. CD62L (L-selectin) expression on neutrophils increased over 4 weeks in South African controls whereas patients with IRIS demonstrated the opposite. Intense staining for the neutrophil marker CD15 and IL-10 was seen in necrotic areas of the lymph nodes of the patients with TB-IRIS.

CONCLUSIONS

Neutrophils in TB-IRIS are activated, recruited to sites of disease, and release granule contents, contributing to pathology.

Immunogenicity and protective efficacy of multistage vaccine candidates (Mtb8.4-HspX and HspX-Mtb8.4) against Mycobacterium tuberculosis infection in mice

In this study, Mtb8.4 and HspX, which are expressed at proliferating and dormant stages of Mycobacterium tuberculosis (M. tuberculosis), respectively, were chosen to construct two fusion proteins, Mtb8.4-HspX (8.4H) and HspX-Mtb8.4 (H8.4), and we investigated whether the antigen dose and protein sequential order could impact the immunogenicity and protective efficacy of these fusion protein vaccines against M. tuberculosis. C57BL/6 mice were vaccinated with new constructions containing a fusion protein with adjuvant of N, N'-dimethyl-N, N'-dioctadecylammonium bromide (DDA) or a mixed adjuvant composed of DDA, polyribocytidylic acid and gelatin (DPG), and the antigen specific immune responses and protective efficacy against M. tuberculosis H37Rv were evaluated. The results showed that both antigens, Mtb8.4-HspX and HspX-Mtb8.4, could elicit strong human T cell responses. With the existing of DDA adjuvant, HspX-Mtb8.4 induced significantly higher secretion level of IFN-γ and TNF-α in spleen cells than Mtb8.4-HspX (p<0.05). In its protective efficacy study, the isolated bacterial Colony Form Unit (CFU) in H8.4-DPG group was significantly reduced compared to 8.4H-DPG group (p<0.05). Furthermore, with the stimulation of Mtb8.4 in vitro, the secretion of IFN-γ and TNF-α from mice immunized with 20μg of H8.4 exhibited relative higher level than the group immunized by 7μg of H8.4 (p<0.05), whereas, IL-2 secreting showed contrary result. The data suggest that the antigen sequential order and dose selection should be considered when a tuberculosis protein vaccine is to be constructed and its immune strategy is to be planned.

TB-IRIS: Proteomic analysis of in vitro PBMC responses to Mycobacterium tuberculosis and response modulation by dexamethasone

Paradoxical tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) occurs in 8-54% of South African patients undergoing treatment for tuberculosis/human immunodeficiency virus co-infection. Improved TB-IRIS molecular pathogenesis understanding would enhance risk stratification, diagnosis, prognostication, and treatment. We assessed how TB-IRIS status and dexamethasone influence leukocyte proteomic responses to Mycobacterium tuberculosis (Mtb). Patient blood was obtained three weeks post-anti-retroviral therapy initiation. Isolated mononuclear cells were stimulated ex vivo with heat-killed Mtb in the presence/absence of dexamethasone. Mass spectrometry-based proteomic comparison of TB-IRIS and non-IRIS patient-derived cells facilitated generation of hypotheses regarding pathogenesis. Few represented TB-IRIS-group immune-related pathways achieved significant activation, with relative under-utilisation of "inter-cellular interaction" and "Fcγ receptor-mediated phagocytosis" (but a tendency towards apoptosis-related) pathways. Dexamethasone facilitated significant activation of innate-related pathways. Differentially-expressed non-IRIS-group proteins suggest focused and co-ordinated immunological pathways, regardless of dexamethasone status. Findings suggest a relative deficit in TB-IRIS-group responses to and clearance of Mtb antigens, ameliorated by dexamethasone.

Paradoxical TB-IRIS in HIV-infected adults: a systematic review and meta-analysis

Paradoxical tuberculosis immune reconstitution inflammatory syndrome (TB-IRIS) was first described almost two decades ago. We undertook this systematic review and meta-analysis to collate findings across studies that have reported the incidence, clinical features, management and outcomes of paradoxical TB-IRIS. Forty studies that cumulatively reported 1048 paradoxical TB-IRIS cases were included. The pooled estimated incidence among patients with HIV-associated TB initiating antiretroviral therapy was 18% (95% CI: 16-21%). Frequent features were pulmonary and lymph node involvement. Hospitalization occurred in 25% (95% CI: 19-30%). In studies that reported treatment, corticosteroids were prescribed more frequently (38%; 95% CI: 27-48%) than nonsteroidal anti-inflammatory drugs (28%; 95% CI: 2-53%). Case fatality was 7% (95% CI: 4-11%), but death attributed to TB-IRIS occurred in 2% of cases (95% CI: 1-3%).

Persistent high mortality in advanced HIV/TB despite appropriate antiretroviral and antitubercular therapy: an emerging challenge

Approximately 1.1 million, or 13 %, of all TB cases in 2013 were coinfected with HIV, and in some African countries, such as Botswana and Swaziland, 60-80 % of TB cases are coinfected with HIV. Effective therapies for both HIV and TB exist, yet patients presenting with TB and advanced HIV still experience high rates of morbidity and mortality despite initiation of both antitubercular and antiretroviral therapy (ART). Previous reviews and research have focused largely on TB-associated immune reconstitution inflammatory syndrome (TB-IRIS) as a type of complicated outcome on ART in advanced HIV/TB, but recent data indicate that immunologic failure despite suppressive ART is associated with early mortality. In this review, we examine recent findings regarding early mortality in HIV/TB and emerging concepts in the pathophysiology of TB-IRIS, in order to provide an integrated view of factors determining outcomes in coinfected people as well as highlight key needs for future research and therapeutic development.

Diabetes as an increasingly common comorbidity among patient hospitalizations for tuberculosis in the USA

OBJECTIVE

Diabetes is a risk factor for active tuberculosis (TB). The purpose of this paper was to estimate the risk of hospitalization for TB with and without a secondary diagnosis of diabetes in groups with different ethnic backgrounds.

RESEARCH DESIGN AND METHODS

We used the Nationwide Inpatient Sample from 1998 to 2011, identifying all patients with a primary diagnosis of TB and/or a secondary diagnosis of diabetes (type 1 or type 2) or HIV. Next, we performed logistic regression to investigate the association of diabetes status, HIV status, and race (and the interaction of diabetes and race) with the risk of hospitalization with a primary diagnosis of TB. We also included a time covariate, to determine whether potential risk factors changed during the study period.

RESULTS

Controlling for HIV status, diabetes did not increase the odds of TB in white and black patients. However, in Hispanic and Asian/Pacific Islander patients, diabetes increased the odds of TB by a factor of 1.7 (95% CI 1.51 to 1.83). Asian/Pacific Islanders who had diabetes but not HIV experienced 26.4 (95% CI 23.1 to 30.1) times the odds of TB relative to the white males without diabetes or HIV. In addition, the percent of TB cases that belong to these high-risk groups (Asian/Pacific Islander/Hispanic diabetics) has more than doubled from 4.6% in 1998 to 9.6% in 2011.

CONCLUSIONS

In specific demographic groups, diabetes was a strong risk factor for hospital admissions for TB.

T cells and adaptive immunity to Mycobacterium tuberculosis in humans

The adaptive immune response mediated by T cells is critical for control of Mycobacterium tuberculosis (M. tuberculosis) infection in humans. However, the M. tuberculosis antigens and host T-cell responses that are required for an effective adaptive immune response to M. tuberculosis infection are yet to be defined. Here, we review recent findings on CD4(+) and CD8(+) T-cell responses to M. tuberculosis infection and examine the roles of distinct M. tuberculosis-specific T-cell subsets in control of de novo and latent M. tuberculosis infection, and in the evolution of T-cell immunity to M. tuberculosis in response to tuberculosis treatment. In addition, we discuss recent studies that elucidate aspects of M. tuberculosis-specific adaptive immunity during human immunodeficiency virus co-infection and summarize recent findings from vaccine trials that provide insight into effective adaptive immune responses to M. tuberculosis infection.

Acquired immunodeficiencies and tuberculosis: focus on HIV/AIDS and diabetes mellitus

The spread of human immunodeficiency virus (HIV) infection within Africa led to marked increases in numbers of cases of tuberculosis (TB), and although the epidemic peaked in 2006, there were still 1.8 million new cases in 2013, with 29.2 million prevalent cases. Half of all TB cases in Africa are in those with HIV co-infection. A brief review of the well-documented main immunological mechanisms of HIV-associated increased susceptibility to TB is presented. However, a new threat is facing TB control, which presents itself in the form of a rapid increase in the number of people living with type II diabetes mellitus (T2DM), particularly in areas that are already hardest hit by the TB epidemic. T2DM increases susceptibility to TB threefold, and the TB burden attributable to T2DM is 15%. This review addresses the much smaller body of research information available on T2DM-TB, compared to HIV-TB comorbidity. We discuss the altered clinical presentation of TB in the context of T2DM comorbidity, changes in innate and adaptive immune responses, including lymphocyte subsets and T-cell phenotypes, the effect of treatment of the different comorbidities, changes in biomarker expression and genetic predisposition to the respective morbidities, and other factors affecting the comorbidity. Although significant gains have been made in improving our understanding of the underlying mechanisms of T2DM-associated increased susceptibility, knowledge gaps still exist that require urgent attention.

HIV-tuberculosis-associated immune reconstitution inflammatory syndrome is characterized by Toll-like receptor and inflammasome signalling

Patients with HIV-associated tuberculosis (TB) initiating antiretroviral therapy (ART) may develop immune reconstitution inflammatory syndrome (TB-IRIS). No biomarkers for TB-IRIS have been identified and the underlying mechanisms are unclear. Here we perform transcriptomic profiling of the blood samples of patients with HIV-associated TB. We identify differentially abundant transcripts as early as week 0.5 post ART initiation that predict downstream activation of proinflammatory cytokines in patients who progress to TB-IRIS. At the characteristic time of TB-IRIS onset (week 2), the signature is characterized by over-representation of innate immune mediators including TLR signalling and TREM-1 activation of the inflammasome. In keeping with the transcriptional data, concentrations of plasma cytokines and caspase-1/5 are elevated in TB-IRIS. Inhibition of MyD88 adaptor and group 1 caspases reduces secretion of cytokines including IL-1 in TB-IRIS patients. These data provide insight on the pathogenesis of TB-IRIS and may assist the development of specific therapies.

Some patients with HIV-associated tuberculosis develop an immune reconstitution inflammatory syndrome (TB-IRIS) in response to antiretroviral therapy. Here the authors identify genes differentially expressed in patients likely to progress to TB-IRIS and find activation of Toll-like receptor and inflammasome pathways.

Interleukin 27R regulates CD4+ T cell phenotype and impacts protective immunity during Mycobacterium tuberculosis infection

Loss of IL-27R on T cells results in increased protection from Mycobacterium tuberculosis. Torrado et al. demonstrate that IL-27R^−/− T cells show improved fitness that is associated with decreased expression of cell death molecules, maintenance of IL-2 production, and preferential accumulation in the lung parenchyma and around infected macrophages.

CD4⁺ T cells mediate protection against Mycobacterium tuberculosis (Mtb); however, the phenotype of protective T cells is undefined, thereby confounding vaccination efforts. IL-27 is highly expressed during human tuberculosis (TB), and absence of IL-27R (Il27ra) specifically on T cells results in increased protection. IL-27R deficiency during chronic Mtb infection does not impact antigen-specific CD4⁺ T cell number but maintains programmed death-1 (PD-1), CD69, and CD127 expression while reducing T-bet and killer cell lectin-like receptor G1 (KLRG1) expression. Furthermore, T-bet haploinsufficiency results in failure to generate KLRG1⁺, antigen-specific CD4⁺ T cells, and in improved protection. T cells in Il27ra^−/− mice accumulate preferentially in the lung parenchyma within close proximity to Mtb, and antigen-specific CD4⁺ T cells lacking IL-27R are intrinsically more fit than intact T cells and maintain IL-2 production. Improved fitness of IL-27R–deficient T cells is not associated with increased proliferation but with decreased expression of cell death–associated markers. Therefore, during Mtb infection, IL-27R acts intrinsically on T cells to limit protection and reduce fitness, whereas the IL-27R–deficient environment alters the phenotype and location of T cells. The significant expression of IL-27 in TB and the negative influence of IL-27R on T cell function demonstrate the pathway by which this cytokine/receptor pair is detrimental in TB.

Towards tuberculosis elimination: an action framework for low-incidence countries

This paper describes an action framework for countries with low tuberculosis (TB) incidence (<100 TB cases per million population) that are striving for TB elimination. The framework sets out priority interventions required for these countries to progress first towards "pre-elimination" (<10 cases per million) and eventually the elimination of TB as a public health problem (less than one case per million). TB epidemiology in most low-incidence countries is characterised by a low rate of transmission in the general population, occasional outbreaks, a majority of TB cases generated from progression of latent TB infection (LTBI) rather than local transmission, concentration to certain vulnerable and hard-to-reach risk groups, and challenges posed by cross-border migration. Common health system challenges are that political commitment, funding, clinical expertise and general awareness of TB diminishes as TB incidence falls. The framework presents a tailored response to these challenges, grouped into eight priority action areas: 1) ensure political commitment, funding and stewardship for planning and essential services; 2) address the most vulnerable and hard-to-reach groups; 3) address special needs of migrants and cross-border issues; 4) undertake screening for active TB and LTBI in TB contacts and selected high-risk groups, and provide appropriate treatment; 5) optimise the prevention and care of drug-resistant TB; 6) ensure continued surveillance, programme monitoring and evaluation and case-based data management; 7) invest in research and new tools; and 8) support global TB prevention, care and control. The overall approach needs to be multisectorial, focusing on equitable access to high-quality diagnosis and care, and on addressing the social determinants of TB. Because of increasing globalisation and population mobility, the response needs to have both national and global dimensions.

Duality of lipid mediators in host response against Mycobacterium tuberculosis: good cop, bad cop

Lipid mediators play an important role in infection- and tissue injury-driven inflammatory responses and in the subsequent inhibition and resolution of the response. Here, we discuss recent findings that substantiate how Mycobacterium tuberculosis promotes its survival in the host by dysregulation of lipid mediator balance. By inhibiting prostaglandin E2 (PGE2) and enhancing lipoxin production, M. tuberculosis induces necrotic death of the macrophage, an environment that favors its growth. These new findings provide opportunities for developing and repurposing therapeutics to modulate lipid mediator balance and enhance M. tuberculosis growth restriction.

Anti-CD20 antibody therapy and susceptibility to Pneumocystis pneumonia

Anti-CD20 antibody therapy has been a useful medication for managing non-Hodgkin's lymphoma as well as autoimmune diseases characterized by autoantibody generation. CD20 is expressed during most developmental stages of B lymphocytes; thus, CD20 depletion leads to B-lymphocyte deficiency. As the drug has become more widely used, there has been an increase in the number of case reports of patients developing Pneumocystis pneumonia. The role of anti-CD20 in Pneumocystis jirovecii infection is under debate due to the fact that most patients receiving it are on a regimen of multiple immunosuppressive medications. To address the specific role of CD20 depletion in host immunity against Pneumocystis, we examined a murine anti-CD20 depleting antibody. We demonstrated that anti-CD20 alone is permissive for Pneumocystis infection and that anti-CD20 impairs components of type II immunity, such as production of interleukin-4 (IL-4), IL-5, and IL-13 by whole-lung cells, in response to Pneumocystis murina. We also demonstrated that CD4(+) T cells from mice treated with anti-CD20 during Pneumocystis infection are incapable of mounting a protective immune response when transferred into Rag1(-/-) mice. Thus, CD20(+) cells are critical for generating protective CD4(+) T-cell immune responses against this organism.

Tuberculosis and HIV Coinfection

Tuberculosis (TB) and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) constitute the main burden of infectious disease in resource-limited countries. In the individual host, the two pathogens, Mycobacterium tuberculosis and HIV, potentiate one another, accelerating the deterioration of immunological functions. In high-burden settings, HIV coinfection is the most important risk factor for developing active TB, which increases the susceptibility to primary infection or reinfection and also the risk of TB reactivation for patients with latent TB. M. tuberculosis infection also has a negative impact on the immune response to HIV, accelerating the progression from HIV infection to AIDS. The clinical management of HIV-associated TB includes the integration of effective anti-TB treatment, use of concurrent antiretroviral therapy (ART), prevention of HIV-related comorbidities, management of drug cytotoxicity, and prevention/treatment of immune reconstitution inflammatory syndrome (IRIS).

Immune reconstitution inflammatory syndrome in HIV-infected patients

Access to antiretroviral therapy (ART) is improving worldwide. Immune reconstitution inflammatory syndrome (IRIS) is a common complication of ART initiation. In this review, we provide an overview of clinical and epidemiological features of HIV-associated IRIS, current understanding of pathophysiological mechanisms, available therapy, and preventive strategies. The spectrum of HIV-associated IRIS is described, with a particular focus on three important pathogen-associated forms: tuberculosis-associated IRIS, cryptococcal IRIS, and Kaposi's sarcoma IRIS. While the clinical features and epidemiology are well described, there are major gaps in our understanding of pathophysiology and as a result therapeutic and preventative strategies are suboptimal. Timing of ART initiation is critical to reduce IRIS-associated morbidity. Improved understanding of the pathophysiology of IRIS will hopefully enable improved diagnostic modalities and better targeted treatments to be developed.

[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.

Neutrophil-associated central nervous system inflammation in tuberculous meningitis immune reconstitution inflammatory syndrome

BACKGROUND

The immunopathogenesis of tuberculosis-associated immune reconstitution inflammatory syndrome (IRIS) remains incompletely understood, and we know of only 1 disease site-specific study of the underlying immunology; we recently showed that Mycobacterium tuberculosis culture positivity and increased neutrophils in the cerebrospinal fluid (CSF) of patients with tuberculous meningitis (TBM) are associated with TBM-IRIS. In this study we investigated inflammatory mediators at the disease site in patients with TBM-IRIS.

METHODS

We performed lumbar puncture at 3-5 time points in human immunodeficiency virus (HIV)-infected patients with TBM (n = 34), including at TBM diagnosis, at initiation of antiretroviral therapy (ART) (day 14), 14 days after ART initiation, at presentation of TBM-IRIS, and 14 days thereafter. We determined the concentrations of 40 mediators in CSF (33 paired with blood) with Luminex or enzyme-linked immunosorbent assays. Findings were compared between patients who developed TBM-IRIS (n = 16) and those who did not (TBM-non-IRIS; n = 18).

RESULTS

At TBM diagnosis and 2 weeks after ART initiation, TBM-IRIS was associated with severe, compartmentalized inflammation in the CSF, with elevated concentrations of cytokines, chemokines, neutrophil-associated mediators, and matrix metalloproteinases, compared with TBM-non-IRIS. Patients with TBM-non-IRIS whose CSF cultures were positive for M. tuberculosis at TBM diagnosis (n = 6) showed inflammatory responses similar to those seen in patients with TBM-IRIS at both time points. However, at 2 weeks after ART initiation, S100A8/A9 was significantly increased in patients with TBM-IRIS, compared with patients with TBM-non-IRIS whose cultures were positive at baseline.

CONCLUSIONS

A high baseline M. tuberculosis antigen load drives an inflammatory response that manifests clinically as TBM-IRIS in most, but not all, patients with TBM. Neutrophils and their mediators, especially S100A8/A9, are closely associated with the central nervous system inflammation that characterizes TBM-IRIS.

Developments in HIV-1 immunotherapy and therapeutic vaccination

Since the human immunodeficiency virus (HIV-1) pandemic began, few prophylactic vaccines have reached phase III trials. Only one has shown partial efficacy in preventing HIV-1 infection. The introduction of antiretroviral therapy (ART) has had considerable success in controlling infection and reducing transmission but in so doing has changed the nature of HIV-1 infection for those with access to ART. Access, compliance, and toxicity alongside the emergence of serious non-AIDS morbidity and the sometimes poor immune reconstitution in ART-treated patients have emphasized the need for additional therapies. Such therapy is intended to contribute to control of HIV-1 infection, permit structured treatment interruptions, or even establish a functional cure of permanently suppressed and controlled infection. Both immunotherapy and therapeutic vaccination have the potential to reach these goals. In this review, the latest developments in immunotherapy and therapeutic vaccination are discussed.