Interplay between systemic inflammation, anemia, and mycobacterial dissemination and its impact on mortality in TB-associated HIV: a prospective cohort study

Oxidative battles in tuberculosis: walking the ferroptotic tightrope

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), remains one of the leading causes of death worldwide. TB pathogenesis is shaped by a complex interaction between the pathogen and host immune responses, particularly through mechanisms such as oxidative stress and ferroptosis; a form of regulated necrotic cell death driven by iron-dependent lipid peroxidation. This Review highlights recent insights into how Mtb modulates oxidative stress pathways and thus triggers ferroptosis in host cells. Understanding the interplay between oxidative stress responses and cellular and tissue necrosis opens new avenues for therapeutic interventions of TB by controlling bacterial growth and preventing host tissue damage.

Altered IL-6 signalling and risk of tuberculosis: a multi-ancestry mendelian randomisation study

BACKGROUND

The role of IL-6 responses in human tuberculosis risk is unknown. IL-6 signalling inhibitors, such as tocilizumab, are thought to increase the risk of progression to tuberculosis, and screening for latent Mycobacterium tuberculosis infection before using these drugs is widely recommended. We used single nucleotide polymorphisms (SNPs) in and near the IL-6 receptor gene (IL6R), including the non-synonymous variant, rs2228145, for which the C allele contributes to reduced classic (cis) IL-6 signalling activity, to test the hypothesis that altered IL-6 signalling is causally associated with the risk of developing tuberculosis.

METHODS

We performed a meta-analysis of genome-wide association studies (GWAS) published in English from database inception to Jan 1, 2024. GWAS were identified from the European Bioinformatics Institute, MRC Integrative Epidemiology Unit catalogues, and MEDLINE, selecting publicly available studies for which tuberculosis was an outcome and that included the IL6R rs2228145 SNP. Using each study's population-level summary statistics, effect estimates were extracted for each additional copy of the C allele of rs2228145. We used these estimates to perform multi-ancestry, two-sample mendelian randomisation analyses to estimate the causal effect of reduced IL-6 signalling on tuberculosis. Our primary analyses used rs2228145-C as a genetic instrument, weighted on C-reactive protein (CRP) reduction as a measure of the effect on IL-6 signalling. We also took an alternative, ancestry-specific, multiple SNP approach using IL-6 receptor plasma protein as an exposure. Additionally, we compared the effects of rs2228145 in tuberculosis with those in critical COVID-19, rheumatoid arthritis, Crohn's disease, and coronary artery disease using the summary statistics extracted from GWAS.

FINDINGS

17 GWAS were included, collating data for 19 302 individuals with tuberculosis (cases) and 1 019 821 population controls across multiple ancestries. For each additional rs2228145-C allele, the odds of tuberculosis reduced (odds ratio [OR] 0·94 [95% CI 0·92-0·97]; p=6·8 × 10-6). Multi-ancestry mendelian randomisation analyses supported these findings, with decreased odds of tuberculosis associated with readouts of reduced IL-6 signalling (0·52 [0·39-0·69] for each natural log CRP decrease; p=6·8 × 10-6), with weak evidence of heterogeneity (I2=0·315; p=0·11). Ancestry-specific, multiple SNP mendelian randomisation using increase in IL-6 receptor plasma protein as an exposure revealed a similar reduced risk of tuberculosis (OR 0·94 [95% CI 0·93-0·96]; p=2·4 × 10-10). The protective effects on tuberculosis seen with rs2228145-C were similar in size and direction to those observed in critical COVID-19 (0·66 [0·50-0·86]), Crohn's disease (0·57 [0·44-0·74]), and rheumatoid arthritis (0·45 [0·36-0·58]), all of which benefit from the therapeutic effects of IL-6 antagonism.

INTERPRETATION

Our findings propose a causal relationship between reduced IL-6 signalling and lower risk of tuberculosis, akin to the effect seen in other IL-6 mediated diseases. This study suggests that IL-6 antagonists do not increase the risk of tuberculosis but rather should be investigated as therapeutic adjuncts in its treatment.

FUNDING

UK National Institute for Health and Care Research, Wellcome Trust, EU European Regional Development Fund, the Welsh Government, and UK Research and Innovation.

Modern differential diagnosis of various types of anemia in patients with HIV-associated disease

This article substantiates the development of a diagnostic algorithm to differentiate between anemia of chronic disease (ACD) and iron deficiency anemia (IDA) in patients with HIV-associated disease. A cross-sectional descriptive study included 125 patients with HIV-associated disease, 101 of whom had anemia syndrome and 24 were without it (control group). Patients with anemia were divided into three groups: Group 1 with ACD only, Group 2 with ACD and IDA, and Group 3 with IDA only. Upon admission, all patients underwent assessments for red blood cell count, hemoglobin, IL-6, IL-10, and IL-1β, IFN-γ, TNF-α, ferritin, C-reactive protein, transferrin, hepcidin, and soluble transferrin receptor levels. Discriminant analysis followed by obtaining a canonical linear discriminant function was used to calculate a mathematical model for the differential diagnosis of ACD and IDA. Canonical analysis was also used to obtain centroids for ACD (2.86 arbitrary units) and IDA (2.54 arbitrary units). A patient with a calculated canonical linear discriminant function was to be assigned to the group of ACD or IDA based on the minimal distance to the corresponding centroid. The resulting mathematical model has 88.8% sensitivity and 100% specificity. The use of IL-6 and ferritin concentrations is also proposed as independent laboratory markers for the differential diagnosis of ACD and IDA. The canonical linear discriminant function obtained from the calculations, along with the levels of IL-6 and ferritin in the blood, have high diagnostic value for verifying ACD and IDA in patients with HIV-related disease. Their use enables the determination of the type of anemia during the initial contact between the physician and the patient.

Burden of mortality and its predictors among TB-HIV co-infected patients in Ethiopia: Systematic review and meta-analysis

BACKGROUND

Human immunodeficiency virus (HIV) and tuberculosis (TB) are still the two major deadly pandemics globally, causes 167,000 deaths in 2022. The two lethal combinations pose a substantial challenge to public health, especially in areas with high burden of both diseases such as Sub-Saharan Africa including Ethiopia. However, there is no study that showed national figure on mortality of TB/HIV co-infected patients. Hence, this review intended to provide pooled mortality rate and its predictors among patients co- infected with twin pandemics.

METHODS

Using reputable electronic data bases, primary studies were searched from January 25 to February 5, 2024. The review included papers published in English language conducted between 2004 and 2024. Heterogeneity between included studies was evaluated using Cochrane Q-test and the I2 statistics. Sub-group analysis was done to mitigate significant heterogeneity. Sensitivity analysis was also done to evaluate the effect of single studies on pooled estimated result.

RESULTS

In this systematic review and meta-analysis a total of 5,210 study participants were included from 15 primary studies. The review disclosed that the pooled proportion and incidence of mortality were 18.73% (95% CI: 15.92-20.83) and 4.94 (95% CI: 2.98-6.89) respectively. Being bedridden and ambulatory functional status, poor ART adherence, CD4 count below the threshold (<200 cells/mm3), advanced WHO clinical staging, not provision of cotrimoxazole and isoniazid preventing therapy, anemia and extra pulmonary TB were significant predictors of mortality.

CONCLUSION AND RECOMMENDATIONS

The analyzed data of this systematic review and meta-analysis depicted that the national pooled proportion and incidence of mortality among TB-HIV co-infected patients were considered to be still high. The authors strongly recommended scale up and continuous provision of cotrimoxazole and isoniazid preventive therapy. In addition, early identification and treatment of anemia will greatly halt the high burden of mortality. Generally, to reduce mortality and improve survival, a collaborative effort is mandatory to emphasize close follow up of patients with identified predictors.

Disseminated tuberculosis is associated with impaired T cell immunity mediated by non-canonical NF-κB pathway

OBJECTIVES

The mechanism that leads to disseminated tuberculosis in HIV-negative patients is still largely unknown. T cell subsets and signaling pathways that were associated with disseminated tuberculosis were investigated.

METHODS

Single-cell profiling of whole T cells was performed to identify T cell subsets and enriched signaling pathways that were associated with disseminated tuberculosis. Flow cytometric analysis and blocking experiment were used to investigate the findings obtained by transcriptome sequencing.

RESULTS

Patients with disseminated tuberculosis had depleted Th1, Tc1 and Tc17 cell subsets, and IFNG was the most down-regulated gene in both CD4 and CD8 T cells. Gene Ontology analysis showed that non-canonical NF-κB signaling pathway, including NFKB2 and RELB genes, was significantly down-regulated and was probably associated with disseminated tuberculosis. Expression of several TNF superfamily ligands and receptors, such as LTA and TNF genes, were suppressed in patients with disseminated tuberculosis. Blocking of TNF-α and soluble LTα showed that TNF-α was involved in IFN-γ production and LTα influenced TNF-α expression in T cells.

CONCLUSIONS

Impaired T cell IFN-γ response mediated by suppression of TNF and non-canonical NF-κB signaling pathways might be responsible for disseminated tuberculosis.