A Systematic Review of the Clinical Diagnosis of Transient Hypogammaglobulinemia of Infancy.

Transient hypogammaglobulinemia of infancy (THI) is a primary immunodeficiency caused by a temporary decline in serum immunoglobulin G (IgG) levels greater than two standard deviations below the mean age-specific reference values in infants between 5 and 24 months of age. Preterm infants are particularly susceptible to THI, as IgG is only transferred across the placenta from mother to infant during the third trimester of pregnancy. This study aimed to conduct a systematic review of the diagnostic criteria for transient hypogammaglobulinemia of infancy. Systematic review: Three electronic databases (PubMed, MEDLINE, and Google Scholar) were manually searched from September 2021 to April 2022. Abstracts were screened to assess their fit to the inclusion criteria. Data were extracted from the selected studies using an adapted extraction tool (Cochrane). The studies were then assessed for bias using an assessment tool adapted from Cochrane. Of the 215 identified articles, 16 were eligible for examining the diagnostic criteria of THI. These studies were also assessed for bias in the six domains. A total of five studies (31%) had a low risk of bias, while four studies (25%) had a high risk of bias, and bias in the case of seven studies (44%) was unclear. We conclude that THI is only definitively diagnosed after abnormal IgG levels normalise. Hence, THI is not a benign condition, and monitoring for subsequent recurrent infections must be conducted. The diagnostic criteria should also include vaccine and isohaemagglutinin responses to differentiate THI from other immunological disorders in infants.

SARS-CoV-2 infection dysregulates NAD metabolism.

Introduction: Severe COVID-19 results initially in pulmonary infection and inflammation. Symptoms can persist beyond the period of acute infection, and patients with Post-Acute Sequelae of COVID (PASC) often exhibit a variety of symptoms weeks or months following acute phase resolution including continued pulmonary dysfunction, fatigue, and neurocognitive abnormalities. We hypothesized that dysregulated NAD metabolism contributes to these abnormalities. Methods: RNAsequencing of lungs from transgenic mice expressing human ACE2 (K18-hACE2) challenged with SARS-CoV-2 revealed upregulation of NAD biosynthetic enzymes, including NAPRT1, NMNAT1, NAMPT, and IDO1 6 days post-infection. Results: Our data also demonstrate increased gene expression of NAD consuming enzymes: PARP 9,10,14 and CD38. At the same time, SIRT1, a protein deacetylase (requiring NAD as a cofactor and involved in control of inflammation) is downregulated. We confirmed our findings by mining sequencing data from lungs of patients that died from SARS-CoV-2 infection. Our validated findings demonstrating increased NAD turnover in SARS-CoV-2 infection suggested that modulating NAD pathways may alter disease progression and may offer therapeutic benefits. Specifically, we hypothesized that treating K18-hACE2 mice with nicotinamide riboside (NR), a potent NAD precursor, may mitigate lethality and improve recovery from SARS-CoV-2 infection. We also tested the therapeutic potential of an anti- monomeric NAMPT antibody using the same infection model. Treatment with high dose anti-NAMPT antibody resulted in significantly decreased body weight compared to control, which was mitigated by combining HD anti-NAMPT antibody with NR. We observed a significant increase in lipid metabolites, including eicosadienoic acid, oleic acid, and palmitoyl carnitine in the low dose antibody + NR group. We also observed significantly increased nicotinamide related metabolites in NR treated animals. Discussion: Our data suggest that infection perturbs NAD pathways, identify novel mechanisms that may explain some pathophysiology of CoVID-19 and suggest novel strategies for both treatment and prevention.

Innate metabolic responses against viral infections.

Metabolic adaptation to viral infections critically determines the course and manifestations of disease. At the systemic level, a significant feature of viral infection and inflammation that ensues is the metabolic shift from anabolic towards catabolic metabolism. Systemic metabolic sequelae such as insulin resistance and dyslipidaemia represent long-term health consequences of many infections such as human immunodeficiency virus, hepatitis C virus and severe acute respiratory syndrome coronavirus 2. The long-held presumption that peripheral and tissue-specific 'immune responses' are the chief line of defence and thus regulate viral control is incomplete. This Review focuses on the emerging paradigm shift proposing that metabolic engagements and metabolic reconfiguration of immune and non-immune cells following virus recognition modulate the natural course of viral infections. Early metabolic footprints are likely to influence longer-term disease manifestations of infection. A greater appreciation and understanding of how local biochemical adjustments in the periphery and tissues influence immunity will ultimately lead to interventions that curtail disease progression and identify new and improved prognostic biomarkers.

Elevated CD4 + T-cell glucose metabolism in HIV+ women with diabetes mellitus.

OBJECTIVE: Immune dysfunction and chronic inflammation are characteristic of HIV infection and diabetes mellitus, with CD4 + T-cell metabolism implicated in the pathogenesis of each disease. However, there is limited information on CD4 + T-cell metabolism in HIV+ persons with diabetes mellitus. We examined CD4 + T-cell glucose metabolism in HIV+ women with and without diabetes mellitus. DESIGN: A case-control study was used to compare CD4 + T-cell glucose metabolism in women with HIV with or without diabetes mellitus. METHODS: Nondiabetic (HIV+DM-, N = 20) or type 2 diabetic HIV+ women with (HIV+DM+, N  = 16) or without (HIV+DMTx+, N  = 18) antidiabetic treatment were identified from the WIHS and matched for age, race/ethnicity, smoking status and CD4 + cell count. CD4 + T-cell immunometabolism was examined by flow cytometry, microfluidic qRT-PCR of metabolic genes, and Seahorse extracellular flux analysis of stimulated CD4 + T cells. RESULTS: HIV+DM+ displayed a significantly elevated proportion of CD4 + T cells expressing the immunometabolic marker GLUT1 compared with HIV+DMTx+ and HIV+DM- ( P  = 0.04 and P  = 0.01, respectively). Relative expression of genes encoding key enzymes for glucose metabolism pathways were elevated in CD4 + T cells of HIV+DM+ compared with HIV+DMTx+ and HIV+DM-. T-cell receptor (TCR)-activated CD4 + T cells from HIV+DM+ showed elevated glycolysis and oxidative phosphorylation compared with HIV+DM-. CONCLUSION: CD4 + T cells from HIV+DM+ have elevated glucose metabolism. Treatment of diabetes mellitus among women with HIV may partially correct CD4 + T-cell metabolic dysfunction.

Corrigendum: Plasma Markers of Disrupted Gut Permeability in Severe COVID-19 Patients.

[This corrects the article DOI: 10.3389/fimmu.2021.686240.].

Non-invasive plasma glycomic and metabolic biomarkers of post-treatment control of HIV.

Non-invasive biomarkers that predict HIV remission after antiretroviral therapy (ART) interruption are urgently needed. Such biomarkers can improve the safety of analytic treatment interruption (ATI) and provide mechanistic insights into the host pathways involved in post-ART HIV control. Here we report plasma glycomic and metabolic signatures of time-to-viral-rebound and probability-of-viral-remission using samples from two independent cohorts. These samples include a large number of post-treatment controllers, a rare population demonstrating sustained virologic suppression after ART-cessation. These signatures remain significant after adjusting for key demographic and clinical confounders. We also report mechanistic links between some of these biomarkers and HIV latency reactivation and/or myeloid inflammation in vitro. Finally, machine learning algorithms, based on selected sets of these biomarkers, predict time-to-viral-rebound with 74% capacity and probability-of-viral-remission with 97.5% capacity. In summary, we report non-invasive plasma biomarkers, with potential functional significance, that predict both the duration and probability of HIV remission after treatment interruption.

Plasma Markers of Disrupted Gut Permeability in Severe COVID-19 Patients.

A disruption of the crosstalk between the gut and the lung has been implicated as a driver of severity during respiratory-related diseases. Lung injury causes systemic inflammation, which disrupts gut barrier integrity, increasing the permeability to gut microbes and their products. This exacerbates inflammation, resulting in positive feedback. We aimed to test whether severe Coronavirus disease 2019 (COVID-19) is associated with markers of disrupted gut permeability. We applied a multi-omic systems biology approach to analyze plasma samples from COVID-19 patients with varying disease severity and SARS-CoV-2 negative controls. We investigated the potential links between plasma markers of gut barrier integrity, microbial translocation, systemic inflammation, metabolome, lipidome, and glycome, and COVID-19 severity. We found that severe COVID-19 is associated with high levels of markers of tight junction permeability and translocation of bacterial and fungal products into the blood. These markers of disrupted intestinal barrier integrity and microbial translocation correlate strongly with higher levels of markers of systemic inflammation and immune activation, lower levels of markers of intestinal function, disrupted plasma metabolome and glycome, and higher mortality rate. Our study highlights an underappreciated factor with significant clinical implications, disruption in gut functions, as a potential force that may contribute to COVID-19 severity.

Phospholipid Metabolism Is Associated with Time to HIV Rebound upon Treatment Interruption.

Lipids are biologically active molecules involved in a variety of cellular processes and immunological functions, including inflammation. It was recently shown that phospholipids and their derivatives, lysophospholipids, can reactivate latent (dormant) tumor cells, causing cancer recurrence. However, the potential link between lipids and HIV latency, persistence, and viral rebound after cessation of antiretroviral therapy (ART) has never been investigated. We explored the links between plasma lipids and the burden of HIV during ART. We profiled the circulating lipidome from plasma samples from 24 chronically HIV-infected individuals on suppressive ART who subsequently underwent an analytic treatment interruption (ATI) without concurrent immunotherapies. The pre-ATI viral burden was estimated as time-to-viral-rebound and viral load set points post-ATI. We found that higher pre-ATI levels of lysophospholipids, including the proinflammatory lysophosphatidylcholine, were associated with faster time-to-viral-rebound and higher viral set points upon ART cessation. Furthermore, higher pre-ATI levels of the proinflammatory by-product of intestinal lysophosphatidylcholine metabolism, trimethylamine-N-oxide (TMAO), were also linked to faster viral rebound post-ART. Finally, pre-ATI levels of several phosphatidylcholine species (lysophosphatidylcholine precursors) correlated strongly with higher pre-ATI levels of HIV DNA in peripheral CD4+ T cells. Our proof-of-concept data point to phospholipids and lysophospholipids as plausible proinflammatory contributors to HIV persistence and rapid post-ART HIV rebound. The potential interplay between phospholipid metabolism and both the establishment and maintenance of HIV latent reservoirs during and after ART warrants further investigation.IMPORTANCE The likelihood of HIV rebound after stopping antiretroviral therapy (ART) is a combination of the size of HIV reservoirs that persist despite ART and the host immunological and inflammatory factors that control these reservoirs. Therefore, there is a need to comprehensively understand these host factors to develop a strategy to cure HIV infection and prevent viral rebound post-ART. Lipids are important biologically active molecules that are known to mediate several cellular functions, including reactivating latent tumor cells; however, their role in HIV latency, persistence, and post-ART rebound has never been investigated. We observed significant links between higher levels of the proinflammatory lysophosphatidylcholine and its intestinal metabolic by-product, trimethylamine-N-oxide, and both faster time-to-viral-rebound and higher viral load set point post-ART. These data highlight the need for further studies to understand the potential contribution of phosphatidylcholine and lysophosphatidylcholine metabolism in shaping host immunological and inflammatory milieu during and after ART.

CD4 T Cell Metabolism Is a Major Contributor of HIV Infectivity and Reservoir Persistence.

HIV infection is characterized by elevated glycolytic metabolism in CD4 T cells. In their recent study, Valle-Casuso et al. demonstrated that both increased glucose utilization and glutamine metabolism are essential for HIV infectivity and replication in CD4 T cells. Here, we discuss the broader implications of immunometabolism in studies of HIV persistence and their potential to inform new treatment and curative strategies.

The Multiparametric Analysis of Mitochondrial Dynamics in T Cells from Cryopreserved Peripheral Blood Mononuclear Cells (PBMCs).

The analysis of mitochondrial dynamics within immune cells allows us to understand how fundamental metabolism influences immune cell functions, and how dysregulated immunometabolic processes impact biology and disease pathogenesis. For example, during infections, mitochondrial fission and fusion coincide with effector and memory T-cell differentiation, respectively, resulting in metabolic reprogramming. As frozen cells are generally not optimal for immunometabolic analyses, and given the logistic difficulties of analysis on cells within a few hours of blood collection, we have optimized and validated a simple cryopreservation protocol for peripheral blood mononuclear cells, yielding >95% cellular viability, as well as preserved metabolic and immunologic properties. Combining fluorescent dyes with cell surface antibodies, we demonstrate how to analyze mitochondrial density, membrane potential, and reactive oxygen species production in CD4 and CD8 T cells from cryopreserved clinical samples.

Sialyl-LewisX Glycoantigen Is Enriched on Cells with Persistent HIV Transcription during Therapy.

A comprehensive understanding of the phenotype of persistent HIV-infected cells, transcriptionally active and/or transcriptionally inactive, is imperative for developing a cure. The relevance of cell-surface glycosylation to HIV persistence has never been explored. We characterize the relationship between cell-surface glycomic signatures and persistent HIV transcription in vivo. We find that the cell surface of CD4+ T cells actively transcribing HIV, despite suppressive therapy, harbors high levels of fucosylated carbohydrate ligands, including the cell extravasation mediator Sialyl-LewisX (SLeX), compared with HIV-infected transcriptionally inactive cells. These high levels of SLeX are induced by HIV transcription in vitro and are maintained after therapy in vivo. Cells with high-SLeX are enriched with markers associated with HIV susceptibility, signaling pathways that drive HIV transcription, and pathways involved in leukocyte extravasation. We describe a glycomic feature of HIV-infected transcriptionally active cells that not only differentiates them from their transcriptionally inactive counterparts but also may affect their trafficking abilities.

The clock is ticking: the impact of ageing on T cell metabolism.

It is now clear that access to specific metabolic programmes controls the survival and function of various immune cell populations, including T cells. Efficient naïve and memory T cell homoeostasis requires the use of specific metabolic pathways and differentiation requires rapid and dramatic metabolic remodelling. While we are beginning to appreciate the crucial role of metabolic programming during normal T cell physiology, many of the potential impacts of ageing on metabolic homoeostasis and remodelling in T cells remain unexplored. This review will outline our current understanding of T cell metabolism and explore age-related metabolic changes that are postulated or have been demonstrated to impact T cell function.

Glycolysis Is Required for LPS-Induced Activation and Adhesion of Human CD14+CD16- Monocytes.

Monocytes in humans consist of 3 subsets; CD14+CD16- (classical), CD14+CD16+ (intermediate) and CD14dimCD16+ (non-classical), which exhibit distinct and heterogeneous responses to activation. During acute inflammation CD14+CD16- monocytes are significantly elevated and migrate to the sites of injury via the adhesion cascade. The field of immunometabolism has begun to elucidate the importance of the engagement of specific metabolic pathways in immune cell function. Yet, little is known about monocyte metabolism and the role of metabolism in mediating monocyte activation and adherence to vessels. Accordingly, we aimed to determine whether manipulating the metabolism of CD14+CD16- monocytes alters their ability to become activated and adhere. We discovered that LPS stimulation increased the rate of glycolysis in human CD14+CD16- monocytes. Inhibition of glycolysis with 2-deoxy-D-glucose blunted LPS-induced activation and adhesion of monocytes. Mechanistically, we found that increased glycolysis was regulated by mTOR-induced glucose transporter (GLUT)-1. Furthermore, enhanced glycolysis increased accumulation of reactive oxygen species (ROS) and activation of p38 MAPK, which lead to activation and adhesion of monocytes. These findings reveal that glycolytic metabolism is critical for the activation of CD14+CD16- monocytes and contributes to our understanding of the interplay between metabolic substrate preference and immune cell function.

Inflammatory and immunometabolic consequences of gut dysfunction in HIV: Parallels with IBD and implications for reservoir persistence and non-AIDS comorbidities.

The gastrointestinal mucosa is critical for maintaining the integrity and functions of the gut. Disruption of this barrier is a hallmark and a risk factor for many intestinal and chronic inflammatory diseases. Inflammatory bowel disease (IBD) and HIV infection are characterized by microbial translocation and systemic inflammation. Despite the clinical overlaps between HIV and IBD, significant differences exist such as the severity of gut damage and mechanisms of immune cell homeostasis. Studies have supported the role of metabolic activation of immune cells in promoting chronic inflammation in HIV and IBD. This inflammatory response persists in HIV+ persons even after long-term virologic suppression by antiretroviral therapy (ART). Here, we review gut dysfunction and microbiota changes during HIV infection and IBD, and discuss how this may induce metabolic reprogramming of monocytes, macrophages and T cells to impact disease outcomes. Drawing from parallels with IBD, we highlight how factors such as lipopolysaccharides, residual viral replication, and extracellular vesicles activate biochemical pathways that regulate immunometabolic processes essential for HIV persistence and non-AIDS metabolic comorbidities. This review highlights new mechanisms and support for the use of immunometabolic-based therapeutics towards HIV remission/cure, and treatment of metabolic diseases.

Obesity and Fat Metabolism in Human Immunodeficiency Virus-Infected Individuals: Immunopathogenic Mechanisms and Clinical Implications.

Metabolic complications relating to complex effects of viral and immune-mediated mechanisms are now a focus of clinical care among persons living with human immunodeficiency virus (PLHIV), and obesity is emerging as a critical problem. To address knowledge gaps, the US National Institutes of Health sponsored a symposium in May 2018 entitled "Obesity and Fat Metabolism in HIV-infected Individuals." Mechanisms relating to adipose dysfunction and fibrosis, immune function, inflammation, and gastrointestinal integrity were highlighted as contributors to obesity among PLHIV. Fibrotic subcutaneous adipose tissue is metabolically dysfunctional and loses its capacity to expand, leading to fat redistribution, including visceral obesity and ectopic fat accumulation, promoting insulin resistance. Viral proteins, including viral protein R and negative regulatory factor, have effects on adipogenic pathways and cellular metabolism in resident macrophages and T cells. HIV also affects immune cell trafficking into the adipose compartments, with effects on adipogenesis, lipolysis, and ectopic fat accumulation. Key cellular metabolic functions are likely to be affected in PLHIV by gut-derived cytokines and altered microbiota. There are limited strategies to reduce obesity specifically in PLHIV. Enhancing our understanding of critical pathogenic mechanisms will enable the development of novel therapeutics that may normalize adipose tissue function and distribution, reduce inflammation, and improve insulin sensitivity in PLHIV.

A Bioelectronic System to Measure the Glycolytic Metabolism of Activated CD4+ T Cells.

The evaluation of glucose metabolic activity in immune cells is becoming an increasingly standard task in immunological research. In this study, we described a sensitive, inexpensive, and non-radioactive assay for the direct and rapid measurement of the metabolic activity of CD4+ T cells in culture. A portable, custom-built Cell Culture Metabolite Biosensor device was designed to measure the levels of acidification (a proxy for glycolysis) in cell-free CD4+ T cell culture media. In this assay, ex vivo activated CD4+ T cells were incubated in culture medium and mini electrodes were placed inside the cell free culture filtrates in 96-well plates. Using this technique, the inhibitors of glycolysis were shown to suppress acidification of the cell culture media, a response similar to that observed using a gold standard lactate assay kit. Our findings show that this innovative biosensor technology has potential for applications in metabolic research, where acquisition of sufficient cellular material for ex vivo analyses presents a substantial challenge.

Induction of HIF-1α by HIV-1 Infection in CD4+ T Cells Promotes Viral Replication and Drives Extracellular Vesicle-Mediated Inflammation.

Chronic immune activation and inflammation are hallmarks of HIV-1 infection and a major cause of serious non-AIDS events in HIV-1-infected individuals on antiretroviral treatment (ART). Herein, we show that cytosolic double-stranded DNA (dsDNA) generated in infected CD4+ T cells during the HIV-1 replication cycle promotes the mitochondrial reactive oxygen species (ROS)-dependent stabilization of the transcription factor hypoxia-inducible factor 1α (HIF-1α), which in turn, enhances viral replication. Furthermore, we show that induction of HIF-1α promotes the release of extracellular vesicles (EVs). These EVs foster inflammation by inducing the secretion of gamma interferon by bystander CD4+ T cells and secretion of interleukin 6 (IL-6) and IL-1ß by bystander macrophages through an HIF-1α-dependent pathway. Remarkably, EVs obtained from plasma samples from HIV-1-infected individuals also induced HIF-1α activity and inflammation. Overall, this study demonstrates that HIF-1α plays a crucial role in HIV-1 pathogenesis by promoting viral replication and the release of EVs that orchestrate lymphocyte- and macrophage-mediated inflammatory responses.IMPORTANCE Human immunodeficiency virus type 1 (HIV-1) is a very important global pathogen that preferentially targets CD4+ T cells and causes acquired immunodeficiency syndrome (AIDS) if left untreated. Although antiretroviral treatment efficiently suppresses viremia, markers of immune activation and inflammation remain higher in HIV-1-infected patients than in uninfected individuals. The hypoxia-inducible factor 1α (HIF-1α) is a transcription factor that plays a fundamental role in coordinating cellular metabolism and function. Here we show that HIV-1 infection induces HIF-1α activity and that this transcription factor upholds HIV-1 replication. Moreover, we demonstrate that HIF-1α plays a key role in HIV-1-associated inflammation by promoting the release of extracellular vesicles which, in turn, trigger the secretion of inflammatory mediators by noninfected bystander lymphocytes and macrophages. In summary, we identify that the coordinated actions of HIF-1α and extracellular vesicles promote viral replication and inflammation, thus contributing to HIV-1 pathogenesis.