Emerging Role and Characterization of Immunometabolism: Relevance to HIV Pathogenesis, Serious Non-AIDS Events, and a Cure

The immunosuppressive tuberculosis-associated microenvironment inhibits viral replication and promotes HIV-1 latency in CD4+ T cells

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is the most common coinfection among people living with HIV-1. This coinfection is associated with accelerated HIV-1 disease progression and reduced survival. However, the impact of the HIV-1/TB coinfection on HIV-1 replication and latency in CD4+ T cells remains poorly studied. Using the acellular fraction of tuberculous pleural effusion (TB-PE), we investigated whether viral replication and HIV-1 latency in CD4+ T cells are affected by a TB-associated microenvironment. Our results revealed that TB-PE impaired T cell receptor-dependent cell activation and decreased HIV-1 replication in CD4+ T cells. Moreover, this immunosuppressive TB microenvironment promoted viral latency and inhibited HIV-1 reactivation. This study indicates that the TB-induced immune response may contribute to the persistence of the viral reservoir by silencing HIV-1 expression, allowing the virus to persist undetected by the immune system, and increasing the size of the latent HIV-1 reservoir.

Immunometabolites in viral infections: Action mechanism and function

The interplay between viral pathogens and host metabolism plays a pivotal role in determining the outcome of viral infections. Upon viral detection, the metabolic landscape of the host cell undergoes significant changes, shifting from oxidative respiration via the tricarboxylic acid (TCA) cycle to increased aerobic glycolysis. This metabolic shift is accompanied by elevated nutrient accessibility, which is vital for cell function, development, and proliferation. Furthermore, depositing metabolites derived from fatty acids, TCA intermediates, and amino acid catabolism accelerates the immunometabolic transition, facilitating pro-inflammatory and antimicrobial responses. Immunometabolites refer to small molecules involved in cellular metabolism regulating the immune response. These molecules include nutrients, such as glucose and amino acids, along with metabolic intermediates and signaling molecules adenosine, lactate, itaconate, succinate, kynurenine, and prostaglandins. Emerging evidence suggests that immunometabolites released by immune cells establish a complex interaction network within local niches, orchestrating and fine-tuning immune responses during viral diseases. However, our current understanding of the immense capacity of metabolites to convey essential cell signals from one cell to another or within cellular compartments remains incomplete. Unraveling these complexities would be crucial for harnessing the potential of immunometabolites in therapeutic interventions. In this review, we discuss specific immunometabolites and their mechanisms of action in viral infections, emphasizing recent findings and future directions in this rapidly evolving field.

The changing landscape of HIV-associated kidney disease

The HIV epidemic has devastated millions of people globally, with approximately 40 million deaths since its start. The availability of antiretroviral therapy (ART) has transformed the prognosis of millions of individuals infected with HIV such that a diagnosis of HIV infection no longer automatically confers death. However, morbidity and mortality remain substantial among people living with HIV. HIV can directly infect the kidney to cause HIV-associated nephropathy (HIVAN) - a disease characterized by podocyte and tubular damage and associated with an increased risk of kidney failure. The reports of HIVAN occurring primarily in those of African ancestry led to the discovery of its association with APOL1 risk alleles. The advent of ART has led to a substantial decrease in the prevalence of HIVAN; however, reports have emerged of an increase in the prevalence of other kidney pathology, such as focal segmental glomerulosclerosis and pathological conditions associated with co-morbidities of ageing, such as hypertension and diabetes mellitus. Early initiation of ART also results in a longer cumulative exposure to medications, increasing the likelihood of nephrotoxicity. A substantial body of literature supports the use of kidney transplantation in people living with HIV, demonstrating significant survival benefits compared with that of people undergoing chronic dialysis, and similar long-term allograft and patient survival compared with that of HIV-negative kidney transplant recipients.

The Potential of Clostridium butyricum to Preserve Gut Health, and to Mitigate Non-AIDS Comorbidities in People Living with HIV

A dramatic reduction in mortality among people living with HIV (PLWH) has been achieved during the modern antiretroviral therapy (ART) era. However, ART does not restore gut barrier function even after long-term viral suppression, allowing microbial products to enter the systemic blood circulation and induce chronic immune activation. In PLWH, a chronic state of systemic inflammation exists and persists, which increases the risk of development of inflammation-associated non-AIDS comorbidities such as metabolic disorders, cardiovascular diseases, and cancer. Clostridium butyricum is a human butyrate-producing symbiont present in the gut microbiome. Convergent evidence has demonstrated favorable effects of C. butyricum for gastrointestinal health, including maintenance of the structural and functional integrity of the gut barrier, inhibition of pathogenic bacteria within the intestine, and reduction of microbial translocation. Moreover, C. butyricum supplementation has been observed to have a positive effect on various inflammation-related diseases such as diabetes, ulcerative colitis, and cancer, which are also recognized as non-AIDS comorbidities associated with epithelial gut damage. There is currently scant published research in the literature, focusing on the influence of C. butyricum in the gut of PLWH. In this hypothesis review, we speculate the use of C. butyricum as a probiotic oral supplementation may well emerge as a potential future synergistic adjunctive strategy in PLWH, in tandem with ART, to restore and consolidate intestinal barrier integrity, repair the leaky gut, prevent microbial translocation from the gut, and reduce both gut and systemic inflammation, with the ultimate objective of decreasing the risk for development of non-AIDS comorbidities in PLWH.

Whole genome sequencing reveals population diversity and variation in HIV-1 specific host genes

HIV infection continues to be a major global public health issue. The population heterogeneity in susceptibility or resistance to HIV-1 and progression upon infection is attributable to, among other factors, host genetic variation. Therefore, identifying population-specific variation and genetic modifiers of HIV infectivity can catapult the invention of effective strategies against HIV-1 in African populations. Here, we investigated whole genome sequences of 390 unrelated HIV-positive and -negative individuals from Botswana. We report 27.7 million single nucleotide variations (SNVs) in the complete genomes of Botswana nationals, of which 2.8 million were missing in public databases. Our population structure analysis revealed a largely homogenous structure in the Botswana population. Admixture analysis showed elevated components shared between the Botswana population and the Niger-Congo (65.9%), Khoe-San (32.9%), and Europeans (1.1%) ancestries in the population of Botswana. Statistical significance of the mutational burden of deleterious and loss-of-function variants per gene against a null model was estimated. The most deleterious variants were enriched in five genes: ACTRT2 (the Actin Related Protein T2), HOXD12 (homeobox D12), ABCB5 (ATP binding cassette subfamily B member 5), ATP8B4 (ATPase phospholipid transporting 8B4) and ABCC12 (ATP Binding Cassette Subfamily C Member 12). These genes are enriched in the glycolysis and gluconeogenesis (p < 2.84e-6) pathways and therefore, may contribute to the emerging field of immunometabolism in which therapy against HIV-1 infection is being evaluated. Published transcriptomic evidence supports the role of the glycolysis/gluconeogenesis pathways in the regulation of susceptibility to HIV, and that cumulative effects of genetic modifiers in glycolysis/gluconeogenesis pathways may potentially have effects on the expression and clinical variability of HIV-1. Identified genes and pathways provide novel avenues for other interventions, with the potential for informing the design of new therapeutics.

ROS-Induced Mitochondrial Dysfunction in CD4 T Cells from ART-Controlled People Living with HIV

We have previously demonstrated mitochondrial dysfunction in aging CD4 T cells from antiretroviral therapy (ART)-controlled people living with HIV (PLWH). However, the underlying mechanisms by which CD4 T cells develop mitochondrial dysfunction in PLWH remain unclear. In this study, we sought to elucidate the mechanism(s) of CD4 T cell mitochondrial compromise in ART-controlled PLWH. We first assessed the levels of reactive oxygen species (ROS), and we observed significantly increased cellular and mitochondrial ROS levels in CD4 T cells from PLWH compared to healthy subjects (HS). Furthermore, we observed a significant reduction in the levels of proteins responsible for antioxidant defense (superoxide dismutase 1, SOD1) and ROS-mediated DNA damage repair (apurinic/apyrimidinic endonuclease 1, APE1) in CD4 T cells from PLWH. Importantly, CRISPR/Cas9-mediated knockdown of SOD1 or APE1 in CD4 T cells from HS confirmed their roles in maintaining normal mitochondrial respiration via a p53-mediated pathway. Reconstitution of SOD1 or APE1 in CD4 T cells from PLWH successfully rescued mitochondrial function as evidenced by Seahorse analysis. These results indicate that ROS induces mitochondrial dysfunction, leading to premature T cell aging via dysregulation of SOD1 and APE1 during latent HIV infection.

Altered lipid metabolites accelerate early dysfunction of T cells in HIV-infected rapid progressors by impairing mitochondrial function

The complex mechanism of immune-system damage in HIV infection is incompletely understood. HIV-infected "rapid progressors" (RPs) have severe damage to the immune system early in HIV infection, which provides a "magnified" opportunity to study the interaction between HIV and the immune system. In this study, forty-four early HIV-infected patients (documented HIV acquisition within the previous 6 months) were enrolled. By study the plasma of 23 RPs (CD4⁺ T-cell count < 350 cells/µl within 1 year of infection) and 21 "normal progressors" (NPs; CD4⁺ T-cell count > 500 cells/μl after 1 year of infection), eleven lipid metabolites were identified that could distinguish most of the RPs from NPs using an unsupervised clustering method. Among them, the long chain fatty acid eicosenoate significantly inhibited the proliferation and secretion of cytokines and induced TIM-3 expression in CD4⁺ and CD8⁺ T cells. Eicosenoate also increased levels of reactive oxygen species (ROS) and decreased oxygen consumption rate (OCR) and mitochondrial mass in T cells, indicating impairment in mitochondrial function. In addition, we found that eicosenoate induced p53 expression in T cells, and inhibition of p53 effectively decreased mitochondrial ROS in T cells. More importantly, treatment of T cells with the mitochondrial-targeting antioxidant mito-TEMPO restored eicosenoate-induced T-cell functional impairment. These data suggest that the lipid metabolite eicosenoate inhibits immune T-cell function by increasing mitochondrial ROS by inducing p53 transcription. Our results provide a new mechanism of metabolite regulation of effector T-cell function and provides a potential therapeutic target for restoring T-cell function during HIV infection.

Cellular Senescence in Immunity against Infections

Cellular senescence is characterized by irreversible cell cycle arrest in response to different triggers and an inflammatory secretome. Although originally described in fibroblasts and cell types of solid organs, cellular senescence affects most tissues with advancing age, including the lymphoid tissue, causing chronic inflammation and dysregulation of both innate and adaptive immune functions. Besides its normal occurrence, persistent microbial challenge or pathogenic microorganisms might also accelerate the activation of cellular aging, inducing the premature senescence of immune cells. Therapeutic strategies counteracting the detrimental effects of cellular senescence are being developed. Their application to target immune cells might have the potential to improve immune dysfunctions during aging and reduce the age-dependent susceptibility to infections. In this review, we discuss how immune senescence influences the host's ability to resolve more common infections in the elderly and detail the different markers proposed to identify such senescent cells; the mechanisms by which infectious agents increase the extent of immune senescence are also reviewed. Finally, available senescence therapeutics are discussed in the context of their effects on immunity and against infections.

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.

A randomized control trial of high-dose micronutrient-antioxidant supplementation in healthy persons with untreated HIV infection

Background

Although micronutrient and antioxidant supplementation are widely used by persons with human immunodeficiency virus (HIV), a therapeutic role beyond recommended daily allowances (RDA) remains unproven. An oral high-dose micronutrient and antioxidant supplement (Treatment) was compared to an RDA supplement (Control) for time to progressive immunodeficiency or initiation of antiretroviral therapy (ART) in people living with HIV (PLWH).

Methods

This study was a randomized, double-blind, placebo-controlled multicenter clinical trial. PLWH were recruited from Canadian HIV Trials Network sites, and followed quarterly for two years. Eligible participants were asymptomatic, antiretroviral treatment (ART)-naïve, HIV-seropositive adults with a CD4 T lymphocyte count (CD4 count) between 375–750 cells/μL. Participants were randomly allocated 1:1 to receive Treatment or Control supplements. The primary outcome was a composite of time-to-first of confirmed CD4 count below 350 cells/μL, initiation of ART, AIDS-defining illness or death. Primary analysis was by intention-to-treat. Secondary outcomes included CD4 count trajectory from baseline to ART initiation or two years. A Data and Safety Monitoring Board reviewed the study for safety, recruitment and protocol adherence every six months.

Results

Of 171 enrolled participants: 66 (38.6%) experienced a primary outcome: 27 reached a CD4 count below 350 cells/μL, and 57 started ART. There was no significant difference in time-to-first outcome between groups (Hazard Ratio = 1.05; 95%CI: 0.65, 1.70), or in time to any component outcome. Using intent-to-treat censoring, mean annualized rates of CD4 count decline were -42.703 cells/μL and -79.763 cells/μL for Treatment and Control groups, with no statistical difference in the mean change between groups (-37.06 cells/μL/52 weeks, 95%CI: (-93.59, 19.47); p = 0.1993). Accrual was stopped at 171 of the 212 intended participants after an interim analysis for futility, although participant follow-up was completed.

Conclusions

In ART-naïve PLWH, high-dose antioxidant, micronutrient supplementation compared to RDA supplementation had no significant effect on disease progression or ART initiation.

Clinical trial registration

ClinicalTrials.gov Identifier: NCT00798772.

Modulation of Macrophage Immunometabolism: A New Approach to Fight Infections

Macrophages are essential innate immune cells that contribute to host defense during infection. An important feature of macrophages is their ability to respond to extracellular cues and to adopt different phenotypes and functions in response to these stimuli. The evidence accumulated in the last decade has highlighted the crucial role of metabolic reprogramming during macrophage activation in infectious context. Thus, understanding and manipulation of macrophage immunometabolism during infection could be of interest to develop therapeutic strategies. In this review, we focus on 5 major metabolic pathways including glycolysis, pentose phosphate pathway, fatty acid oxidation and synthesis, tricarboxylic acid cycle and amino acid metabolism and discuss how they sustain and regulate macrophage immune function in response to parasitic, bacterial and viral infections as well as trained immunity. At the end, we assess whether some drugs including those used in clinic and in development can target macrophage immunometabolism for potential therapy during infection with an emphasis on SARS-CoV2 infection.

Two-Drug Regimens for HIV-Current Evidence, Research Gaps and Future Challenges

During the last 30 years, antiretroviral treatment (ART) for human immunodeficiency virus (HIV) infection has been continuously evolving. Since 1996, three-drug regimens (3DR) have been standard-of-care for HIV treatment and are based on a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI) plus two nucleoside reverse transcriptase inhibitors (NRTIs). The effectiveness of first-generation 3DRs allowed a dramatic increase in the life expectancy of HIV-infected patients, although it was associated with several side effects and ART-related toxicities. The development of novel two-drug regimens (2DRs) started in the mid-2000s in order to minimize side effects, reduce drug-drug interactions and improve treatment compliance. Several clinical trials compared 2DRs and 3DRs in treatment-naïve and treatment-experienced patients and showed the non-inferiority of 2DRs in terms of efficacy, which led to 2DRs being used as first-line treatment in several clinical scenarios, according to HIV clinical guidelines. In this review, we summarize the current evidence, research gaps and future prospects of 2DRs.

HIV-Sheltering Platelets From Immunological Non-Responders Induce a Dysfunctional Glycolytic CD4+ T-Cell Profile

Immunological non-responders (InRs) are HIV-infected individuals in whom the administration of combination antiretroviral therapy (cART), although successful in suppressing viral replication, cannot properly reconstitute patient circulating CD4⁺ T-cell number to immunocompetent levels. The causes for this immunological failure remain elusive, and no therapeutic strategy is available to restore a proper CD4⁺ T-cell immune response in these individuals. We have recently demonstrated that platelets harboring infectious HIV are a hallmark of InR, and we now report on a causal connection between HIV-containing platelets and T-cell dysfunctions. We show here that in vivo, platelet–T-cell conjugates are more frequent among CD4⁺ T cells in InRs displaying HIV-containing platelets (<350 CD4⁺ T cells/μl blood for >1 year) as compared with healthy donors or immunological responders (IRs; >350 CD4⁺ T cells/μl). This contact between platelet containing HIV and T cell in the conjugates is not infectious for CD4⁺ T cells, as coculture of platelets from InRs containing HIV with healthy donor CD4⁺ T cells fails to propagate infection to CD4⁺ T cells. In contrast, when macrophages are the target of platelets containing HIV from InRs, macrophages become infected. Differential transcriptomic analyses comparing InR and IR CD4⁺ T cells reveal an upregulation of genes involved in both aerobic and anaerobic glycolysis in CD4⁺ T cells from InR vs. IR individuals. Accordingly, InR platelets containing HIV induce a dysfunctional increase in glycolysis-mediated energy production in CD4⁺ T cells as compared with T cells cocultured with IR platelets devoid of virus. In contrast, macrophage metabolism is not affected by platelet contact. Altogether, this brief report demonstrates a direct causal link between presence of HIV in platelets and T-cell dysfunctions typical of InR, contributing to devise a platelet-targeted therapy for improving immune reconstitution in these individuals.

Comprehensive metabolomics profiling reveals common metabolic alterations underlying the four major non-communicable diseases in treated HIV infection

Background

HIV infection and normal aging share immune and inflammatory changes that result in premature aging and non-communicable diseases (NCDs), but the exact pathophysiology is not yet uncovered. We identified the common metabolic pathways underlying various NCDs in treated HIV infection.

Methods

We performed untargeted metabolomics including 87 HIV-negative (–) normal controls (NCs), 87 HIV-positive (+) NCs, and 148 HIV+ subjects with only one type of NCDs, namely, subclinical carotid atherosclerosis, neurocognitive impairment (NCI), liver fibrosis (LF) and renal impairment. All HIV+ subjects were virally suppressed.

Results

HIV+ patients presented widespread alterations in cellular metabolism compared to HIV– NCs. Glycerophospholipid (GPL) metabolism was the only one disturbed pathway presented in comparisons including HIV– NCs across age groups, HIV+ NCs across age groups, HIV+ NCs vs HIV– NCs and each of HIV+ NCDs vs HIV+ NCs. D-glutamine and D-glutamate metabolism and alanine-aspartate-glutamate metabolism were presented in comparisons between HIV+ NCs vs HIV– NCs, HIV+ LF or HIV+ NCI vs HIV+ NCs. Consistently, subsequent analysis identified a metabolomic fingerprint specific for HIV+ NCDs, containing 42 metabolites whose relative abundance showed either an upward (mainly GPL-derived lipid mediators) or a downward trend (mainly plasmalogen phosphatidylcholines, plasmalogen phosphatidylethanolamines, and glutamine) from HIV– NCs to HIV+ NCs and then HIV+ NCDs, reflecting a trend of increased oxidative stress.

Interpretation

GPL metabolism emerges as the common metabolic disturbance linking HIV to NCDs, followed by glutamine and glutamate metabolism. Together, our data point to the aforementioned metabolisms and related metabolites as potential key targets in studying pathophysiology of NCDs in HIV infection and developing therapeutic interventions.

Funding

China National Science and Technology Major Projects on Infectious Diseases, National Natural Science Foundation of China, Yi-wu Institute of Fudan University, and Shanghai Municipal Health and Family Planning Commission.

Critical role of the CD44lowCD62Llow CD8+ T cell subset in restoring antitumor immunity in aged mice

CD8⁺ T cells play a central role in antitumor immune responses that kill cancer cells directly. In aged individuals, CD8⁺ T cell immunity is strongly suppressed, which is associated with cancer and other age-related diseases. The mechanism underlying this age-related decrease in immune function remains largely unknown. This study investigated the role of T cell function in age-related unresponsiveness to PD-1 blockade cancer therapy. We found inefficient generation of CD44^lowCD62L^low CD8⁺ T cell subset (P4) in draining lymph nodes of tumor-bearing aged mice. In vitro stimulation of naive CD8⁺ T cells first generated P4 cells, followed by effector/memory T cells. The P4 cells contained a unique set of genes related to enzymes involved in one-carbon (1C) metabolism, which is critical to antigen-specific T cell activation and mitochondrial function. Consistent with this finding, 1C-metabolism-related gene expression and mitochondrial respiration were down-regulated in aged CD8⁺ T cells compared with young CD8⁺ T cells. In aged OVA-specific T cell receptor (TCR) transgenic mice, ZAP-70 was not activated, even after inoculation with OVA-expressing tumor cells. The attenuation of TCR signaling appeared to be due to elevated expression of CD45RB phosphatase in aged CD8⁺ T cells. Surprisingly, strong stimulation by nonself cell injection into aged PD-1-deficient mice restored normal levels of CD45RB and ameliorated the emergence of P4 cells and 1C metabolic enzyme expression in CD8⁺ T cells, and antitumor activity. These findings indicate that impaired induction of the P4 subset may be responsible for the age-related resistance to PD-1 blockade, which can be rescued by strong TCR stimulation.

The PI3K pathway as a therapeutic intervention point in inflammatory bowel disease

With glucose being the preferred source of energy in activated T cells, targeting glycolysis has become an attractive therapeutic intervention point for chronic inflammatory bowel diseases (IBD). The switch to glycolysis is mediated by phosphoinositide‐3‐kinases (PI3K) which relay signals from surface receptors to the AKT pathway. We first confirmed by analysis of the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) that metabolism is shifted towards glycolysis in IBD patients as compared to non‐IBD donors. In contrast to non‐IBD donors, OCR correlated with ECAR (IBD: cor = 0.79, p = 2E‐10; non‐IBD: cor = 0.37, p = n.s.), in IBD patients. Second, we tested the PI3K inhibitor copanlisib as a potential therapeutic. Ex vivo, copanlisib suppressed the ECAR significantly in T cells activated by anti‐CD3 antibodies and significantly decreased ECAR rates in the presence of copanlisib (anti‐CD3: 58.24 ± 29.06; copanlisib: 43.16 ± 20.23, p < .000. In addition, copanlisib impaired the activation of CD4⁺ CD25⁺ T cells (anti‐CD3: 42.15 ± 21.46; anti‐CD3 + copanlisib: 26.06 ± 21.82 p = .013) and the secretion of cytokines (IFNγ: anti‐CD3: 6332.0 ± 5707.61 pmol/ml; anti‐CD3 + copanlisib: 6332.0 ± 5707.61, p = .018). In vivo, copanlisib significantly improved the histological scores (ethanol: 8.5 ± 3.81; copanlisib: 4.57 ± 2.82, p = .006) in the NSG‐UC mouse model. Orthogonal partial least square analysis confirmed the efficacy of copanlisib. These data suggest that the PI3K pathway provides an attractive therapeutic intervention point in IBD for patients in relapse. Targeting metabolic pathways have the potential to develop phase dependent therapies.

Mitochondrial Functions Are Compromised in CD4 T Cells From ART-Controlled PLHIV

The hallmark of HIV/AIDS is a gradual depletion of CD4 T cells. Despite effective control by antiretroviral therapy (ART), a significant subgroup of people living with HIV (PLHIV) fails to achieve complete immune reconstitution, deemed as immune non-responders (INRs). The mechanisms underlying incomplete CD4 T cell recovery in PLHIV remain unclear. In this study, CD4 T cells from PLHIV were phenotyped and functionally characterized, focusing on their mitochondrial functions. The results show that while total CD4 T cells are diminished, cycling cells are expanded in PLHIV, especially in INRs. HIV-INR CD4 T cells are more activated, displaying exhausted and senescent phenotypes with compromised mitochondrial functions. Transcriptional profiling and flow cytometry analysis showed remarkable repression of mitochondrial transcription factor A (mtTFA) in CD4 T cells from PLHIV, leading to abnormal mitochondrial and T cell homeostasis. These results demonstrate a sequential cellular paradigm of T cell over-activation, proliferation, exhaustion, senescence, apoptosis, and depletion, which correlates with compromised mitochondrial functions. Therefore, reconstituting the mtTFA pathway may provide an adjunctive immunological approach to revitalizing CD4 T cells in ART-treated PLHIV, especially in INRs.

Granulocyte Macrophage-Colony Stimulating Factor Reverses HIV Protein-Induced Mitochondrial Derangements in Alveolar Macrophages

Despite the advent of antiretroviral therapy, people living with HIV suffer from a range of infectious and noninfectious pulmonary complications. HIV impairs antioxidant defenses and innate immune function of the alveolar macrophage by diminishing granulocyte macrophage-colony stimulating factor (GM-CSF) signaling. Since GM-CSF may be linked to mitochondria, we sought to determine the effects of HIV on GM-CSF receptor expression and alveolar macrophage mitochondrial function. At an academic medical center, studies were completed on alveolar macrophages isolated from both wild-type and HIV transgenic (HIV Tg) rats and human subjects with and without HIV. Primary macrophages were plated and evaluated for expression of GM-CSF receptor beta, phagocytic index, and mitochondrial function in the presence and absence of GM-CSF treatment. GM-CSF receptor expression and mitochondrial function were impaired in macrophages isolated from HIV Tg rats, and treatment with GM-CSF restored GM-CSF receptor expression and mitochondrial function. GM-CSF treatment of HIV Tg rats also increased alveolar macrophage levels of the mitochondrial proteins voltage-dependent anion-selective channel 1 (VDAC) and glucose-regulated protein 75 (Grp75). Similar to the HIV Tg rat model, impairments in mitochondrial bioenergetics were confirmed in alveolar macrophages isolated from human subjects with HIV. HIV-associated impairments in alveolar macrophage mitochondrial bioenergetics likely contribute to innate immune dysfunction in HIV infection, and GM-CSF treatment may offer a novel therapeutic strategy for mitigating these deleterious effects.

The Impact of HIV- and ART-Induced Mitochondrial Dysfunction in Cellular Senescence and Aging

According to the WHO, 38 million individuals were living with human immunodeficiency virus (HIV), 25.4 million of which were using antiretroviral therapy (ART) at the end of 2019. Despite ART-mediated suppression of viral replication, ART is not a cure and is associated with viral persistence, residual inflammation, and metabolic disturbances. Indeed, due to the presence of viral reservoirs, lifelong ART therapy is required to control viremia and prevent disease progression into acquired immune deficiency syndrome (AIDS). Successful ART treatment allows people living with HIV (PLHIV) to achieve a similar life expectancy to uninfected individuals. However, recent studies have illustrated the presence of increased comorbidities, such as accelerated, premature immune aging, in ART-controlled PLHIV compared to uninfected individuals. Studies suggest that both HIV-infection and ART-treatment lead to mitochondrial dysfunction, ultimately resulting in cellular exhaustion, senescence, and apoptosis. Since mitochondria are essential cellular organelles for energy homeostasis and cellular metabolism, their compromise leads to decreased oxidative phosphorylation (OXPHOS), ATP synthesis, gluconeogenesis, and beta-oxidation, abnormal cell homeostasis, increased oxidative stress, depolarization of the mitochondrial membrane potential, and upregulation of mitochondrial DNA mutations and cellular apoptosis. The progressive mitochondrial damage induced by HIV-infection and ART-treatment likely contributes to accelerated aging, senescence, and cellular dysfunction in PLHIV. This review discusses the connections between mitochondrial compromise and cellular dysfunction associated with HIV- and ART-induced toxicities, providing new insights into how HIV and current ART directly impact mitochondrial functions and contribute to cellular senescence and aging in PLHIV. Identifying this nexus and potential mechanisms may be beneficial in developing improved therapeutics for treating PLHIV.

Landscape of T Cells Transcriptional and Metabolic Modules During HIV Infection Based on Weighted Gene Co-expression Network Analysis

Human immunodeficiency virus (HIV) causes acquired immunodeficiency syndrome (AIDS). HIV infection affects the functions and metabolism of T cells, which may determine the fate of patients; however, the specific pathways activated in different T-cell subtypes (CD4⁺ and CD8⁺ T cells) at different stages of infection remain unclear. We obtained transcriptome data of five individuals each with early HIV infection, chronic progressive HIV infection, and no HIV infection. Weighted gene co-expression network analysis was used to evaluate changes in gene expression to determine the antiviral response. An advanced metabolic algorithm was then applied to compare the alterations in metabolic pathways in the two T-cell subtypes at different infection stages. We identified 23 and 20 co-expressed gene modules in CD4⁺ T and CD8⁺ T cells, respectively. CD4⁺ T cells from individuals in the early HIV infection stage were enriched in genes involved in metabolic and infection-related pathways, whereas CD8⁺ T cells were enriched in genes involved in cell cycle and DNA replication. Three key modules were identified in the network common to the two cell types: NLRP1 modules, RIPK1 modules, and RIPK2 modules. The specific role of NLRP1 in the regulation of HIV infection in the human body remains to be determined. Metabolic functional analysis of the two cells showed that the significantly altered metabolic pathways after HIV infection were valine, leucine, and isoleucine degradation; beta-alanine metabolism; and PPAR signaling pathways. In summary, we found the core gene expression modules and different pathways activated in CD4⁺ and CD8⁺ T cells, along with changes in their metabolic pathways during HIV infection progression. These findings can provide an overall resource for establishing biomarkers to facilitate early diagnosis and potential guidance for new targeted therapeutic strategies.

HIV and the tuberculosis "set point": how HIV impairs alveolar macrophage responses to tuberculosis and sets the stage for progressive disease

As HIV has fueled a global resurgence of tuberculosis over the last several decades, there is a growing awareness that HIV-mediated impairments in both innate and adaptive immunity contribute to the heightened risk of tuberculosis in people with HIV. Since early immune responses to Mycobacterium tuberculosis (Mtb) set the stage for subsequent control or progression to active tuberculosis disease, early host-pathogen interactions following Mtb infection can be thought of as establishing a mycobacterial "set point," which we define as the mycobacterial burden at the point of adaptive immune activation. This early immune response is impaired in the context of HIV coinfection, allowing for a higher mycobacterial set point and greater likelihood of progression to active disease with greater bacterial burden. Alveolar macrophages, as the first cells to encounter Mtb in the lungs, play a critical role in containing Mtb growth and establishing the mycobacterial set point. However, a number of key macrophage functions, ranging from pathogen recognition and uptake to phagocytosis and microbial killing, are blunted in HIV coinfection. To date, research evaluating the effects of HIV on the alveolar macrophage response to Mtb has been relatively limited, particularly with regard to the critical early events that help to dictate the mycobacterial set point. A greater understanding of alveolar macrophage functions impacted by HIV coinfection will improve our understanding of protective immunity to Mtb and may reveal novel pathways amenable to intervention to improve both early immune control of Mtb and clinical outcomes for the millions of people worldwide infected with HIV.

Mitochondrial oxidative phosphorylation in peripheral blood mononuclear cells is decreased in chronic HIV and correlates with immune dysregulation

Background

Cellular immunometabolism among people living with HIV (PLWH) on antiretroviral therapy (ART) remains under investigated. We assessed the relationships between mitochondrial oxidative phosphorylation (OXPHOS) in peripheral blood mononuclear cells (PBMCs) and blood parameters associated with HIV immune dysregulation.

Methods

PLWH ≥40 years old and on stable ART ≥3 months were enrolled (N = 149). OXPHOS complex I (CI, NADH dehydrogenase) and complex IV (CIV, cytochrome c oxidase) protein levels in PBMCs were quantified using immunoassays. Monocyte subsets and markers of T-cell activation, senescence, and exhaustion were measured on PBMC by flow cytometry. Plasma inflammatory mediators were quantified using a multiplex assay. HIV-uninfected group (N = 44) of similar age, gender, and ethnicity had available OXPHOS levels.

Results

PLWH had a median age of 51 years. Majority were male (88.6%), Caucasian (57.7%), and with undetectable plasma HIV RNA <50 copies/mL (84.6%). Median CI level was lower in PLWH compared with the HIV-seronegative group (65.5 vs 155.0 optical density/μg protein x 10³, p <0.0001). There was no significant difference in median CIV levels. Lower OXPHOS levels correlated with lower CD4% and CD4/CD8 ratio. On multivariable linear regression adjusted for age, current use of zidovudine/didanosine, and HIV RNA (detectable versus undetectable), lower OXPHOS levels were significantly associated with higher MPO, SAA, SAP, and sVCAM, and higher frequencies of intermediate (CD14⁺⁺CD16⁺) monocytes and TIGIT+TIM3+ CD4 T-cell (p<0.01).

Conclusion

CI PBMC protein levels were decreased in PLWH on ART. Decreased OXPHOS correlated with disease severity and inflammation. Further studies on the relationship between immunometabolism and immune dysregulation in HIV are warranted.

Tissue memory CD4+ T cells expressing IL-7 receptor-alpha (CD127) preferentially support latent HIV-1 infection

The primary reservoir for HIV is within memory CD4+ T cells residing within tissues, yet the features that make some of these cells more susceptible than others to infection by HIV is not well understood. Recent studies demonstrated that CCR5-tropic HIV-1 efficiently enters tissue-derived memory CD4+ T cells expressing CD127, the alpha chain of the IL7 receptor, but rarely completes the replication cycle. We now demonstrate that the inability of HIV to replicate in these CD127-expressing cells is not due to post-entry restriction by SAMHD1. Rather, relative to other memory T cell subsets, these cells are highly prone to undergoing latent infection with HIV, as revealed by the high levels of integrated HIV DNA in these cells. Host gene expression profiling revealed that CD127-expressing memory CD4+ T cells are phenotypically distinct from other tissue memory CD4+ T cells, and are defined by a quiescent state with diminished NFκB, NFAT, and Ox40 signaling. However, latently-infected CD127+ cells harbored unspliced HIV transcripts and stimulation of these cells with anti-CD3/CD28 reversed latency. These findings identify a novel subset of memory CD4+ T cells found in tissue and not in blood that are preferentially targeted for latent infection by HIV, and may serve as an important reservoir to target for HIV eradication efforts.

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.

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.

HIV infection and latency induce a unique metabolic signature in human macrophages

Currently, a major barrier to curing HIV infection is the generation of tissue-associated, non-replicating, long-lasting viral reservoirs that are refractory to therapy and can be reactivated upon anti-retroviral therapy interruption. One of these reservoirs are latently HIV-infected macrophages. Here, we show that HIV infection of macrophages results in survival of a small population of infected cells that are metabolically altered and characterized by mitochondrial fusion, lipid accumulation, and reduced mitochondrial ATP production. No changes in glycolysis were detected. Metabolic analysis indicated an essential role of succinate and other TCA metabolites in the tricarboxylic acid (TCA) cycle in mediating lipid accumulation and oxidative phosphorylation (OXPHOS) in the mitochondria. Furthermore, we show that while uninfected and HIV infected macrophages use fatty acids and glucose as primary sources of energy, surviving HIV infected macrophages also use glutamine/glutamate as a major energy source, and blocking these new sources of energy resulted in the killing of latent HIV infected macrophages. Together, our data provide a new understanding of the formation, properties, and potential novel ways to eliminate macrophage viral reservoirs.

TSC1 and DEPDC5 regulate HIV-1 latency through the mTOR signaling pathway

The latent reservoir of HIV-1 presents a major barrier to viral eradication. The mechanism of the establishment and maintenance of the latent viral reservoir is not yet fully understood, which hinders the development of effective curative strategies. In this study, we identified two inhibitory genes, TSC1 and DEPDC5, that maintained HIV-1 latency by suppressing the mTORC1 pathway. We first adapted a genome-wide CRISPR screening approach to identify host factors required for HIV latency in a T-cell-based latency model and discovered two inhibitory genes, TSC1 and DEPDC5, which are potentially involved in HIV-1 latency. Knockout of either TSC1 or DEPDC5 led to enhanced HIV-1 reactivation in both a T-cell line (C11) and a monocyte cell line (U1), and this enhancement could be antagonized by the mTORC1 inhibitor rapamycin. Further evaluation of the mechanism revealed that TSC1 suppresses AKT-mTORC1-S6 via downregulation of Rheb, whereas DEPDC5 inhibits AKT-mTORC1-S6 through RagA. Overall, both TSC1 and DEPDC5 negatively regulate the AKT-mTORC1 pathway, and thus their agonists could be used in the development of new therapeutic approaches for activating HIV-1 latency.

Polymorphism rs1385129 Within Glut1 Gene SLC2A1 Is Linked to Poor CD4+ T Cell Recovery in Antiretroviral-Treated HIV+ Individuals

Untreated HIV infection is associated with progressive CD4+ T cell depletion, which is generally recovered with combination antiretroviral therapy (cART). However, a significant proportion of cART-treated individuals have poor CD4+ T cell reconstitution. We investigated associations between HIV disease progression and CD4+ T cell glucose transporter-1 (Glut1) expression. We also investigated the association between these variables and specific single nucleotide polymorphisms (SNPs) within the Glut1 regulatory gene AKT (rs1130214, rs2494732, rs1130233, and rs3730358) and in the Glut1-expressing gene SLC2A1 (rs1385129 and rs841853) and antisense RNA 1 region SLC2A1-AS1 (rs710218). High CD4+Glut1+ T cell percentage is associated with rapid CD4+ T cell decline in HIV-positive treatment-naïve individuals and poor T cell recovery in HIV-positive individuals on cART. Evidence suggests that poor CD4+ T cell recovery in treated HIV-positive individuals is linked to the homozygous genotype (GG) associated with SLC2A1 SNP rs1385129 when compared to those with a recessive allele (GA/AA) (odds ratio = 4.67; P = 0.04). Furthermore, poor response to therapy is less likely among Australian participants when compared against American participants (odds ratio: 0.12; P = 0.01) despite there being no difference in prevalence of a specific genotype for any of the SNPs analyzed between nationalities. Finally, CD4+Glut1+ T cell percentage is elevated among those with a homozygous dominant genotype for SNPs rs1385129 (GG) and rs710218 (AA) when compared to those with a recessive allele (GA/AA and AT/TT respectively) (P < 0.04). The heterozygous genotype associated with AKT SNP 1130214 (GT) had a higher CD4+Glut1+ T cell percentage when compared to the dominant homozygous genotype (GG) (P = 0.0068). The frequency of circulating CD4+Glut1+ T cells and the rs1385129 SLC2A1 SNP may predict the rate of HIV disease progression and CD4+ T cell recovery in untreated and treated infection, respectively.

Exploiting immune cell metabolic machinery for functional HIV cure and the prevention of inflammaging

An emerging paradigm in immunology suggests that metabolic reprogramming and immune cell activation and functions are intricately linked. Viral infections, such as HIV infection, as well as cancer force immune cells to undergo major metabolic challenges. Cells must divert energy resources in order to mount an effective immune response. However, the fact that immune cells adopt specific metabolic programs to provide host defense against intracellular pathogens and how this metabolic shift impacts immune cell functions and the natural course of diseases have only recently been appreciated. A clearer insight into how these processes are inter-related will affect our understanding of several fundamental aspects of HIV persistence. Even in patients with long-term use of anti-retroviral therapies, HIV infection persists and continues to cause chronic immune activation and inflammation, ongoing and cumulative damage to multiple organs systems, and a reduction in life expectancy. HIV-associated fundamental changes to the metabolic machinery of the immune system can promote a state of “inflammaging”, a chronic, low-grade inflammation with specific immune changes that characterize aging, and can also contribute to the persistence of HIV in its reservoirs. In this commentary, we will bring into focus evolving concepts on how HIV modulates the metabolic machinery of immune cells in order to persist in reservoirs and how metabolic reprogramming facilitates a chronic state of inflammation that underlies the development of age-related comorbidities. We will discuss how immunometabolism is facilitating the changing paradigms in HIV cure research and outline the novel therapeutic opportunities for preventing inflammaging and premature development of age-related conditions in HIV ⁺ individuals.

Sugar or Fat?-Metabolic Requirements for Immunity to Viral Infections

The realization that an intricate link exists between the metabolic state of immune cells and the nature of the elicited immune responses has brought a dramatic evolution to the field of immunology. We will focus on how metabolic reprogramming through the use of glycolysis and fatty-acid oxidation (sugar or fat) regulates the capacity of immune cells to mount robust and effective immune responses. We will also discuss how fine-tuning sugar and fat metabolism may be exploited as a novel immunotherapeutic strategy to fight viral infections or improve vaccine efficacy.

Metabolically active CD4+ T cells expressing Glut1 and OX40 preferentially harbor HIV during in vitro infection

High glucose transporter 1 (Glut1) surface expression is associated with increased glycolytic activity in activated CD4+ T cells. Phosphatidylinositide 3‐kinases (PI3K) activation measured by p‐Akt and OX40 is elevated in CD4+Glut1+ T cells from HIV+ subjects. TCR engagement of CD4+Glut1+ T cells from HIV+ subjects demonstrates hyperresponsive PI3K‐mammalian target of rapamycin signaling. High basal Glut1 and OX40 on CD4+ T cells from combination antiretroviral therapy (cART)‐treated HIV+ patients represent a sufficiently metabolically active state permissive for HIV infection in vitro without external stimuli. The majority of CD4+OX40+ T cells express Glut1, thus OX40 rather than Glut1 itself may facilitate HIV infection. Furthermore, infection of CD4+ T cells is limited by p110γ PI3K inhibition. Modulating glucose metabolism may limit cellular activation and prevent residual HIV replication in ‘virologically suppressed’ cART‐treated HIV+ persons.

Assessment of metabolic and mitochondrial dynamics in CD4+ and CD8+ T cells in virologically suppressed HIV-positive individuals on combination antiretroviral therapy

Metabolism plays a fundamental role in supporting the growth, proliferation and effector functions of T cells. We investigated the impact of HIV infection on key processes that regulate glucose uptake and mitochondrial biogenesis in subpopulations of CD4+ and CD8+ T cells from 18 virologically-suppressed HIV-positive individuals on combination antiretroviral therapy (cART; median CD4+ cell count: 728 cells/μl) and 13 HIV seronegative controls. Mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) production were also analysed in total CD4+ and CD8+ T cells. Among HIV+/cART individuals, expression of glucose transporter (Glut1) and mitochondrial density were highest within central memory and naïve CD4+ T cells, and lowest among effector memory and transitional memory T cells, with similar trends in HIV-negative controls. Compared to HIV-negative controls, there was a trend towards higher percentage of circulating CD4+Glut1+ T cells in HIV+/cART participants. There were no significant differences in mitochondrial dynamics between subject groups. Glut1 expression was positively correlated with mitochondrial density and MMP in total CD4+ T cells, while MMP was also positively correlated with ROS production in both CD4+ and CD8+ T cells. Our study characterizes specific metabolic features of CD4+ and CD8+ T cells in HIV-negative and HIV+/cART individuals and will invite future studies to explore the immunometabolic consequences of HIV infection.

Metabolic reprogramming during hepatitis B disease progression offers novel diagnostic and therapeutic opportunities

Metabolic remodeling occurs in immune cells during an infection. Host cells must upregulate energy production for growth, proliferation, and effector functions to limit the damage imposed by pathogens. One example, the hepatitis B virus, induces hepatic injury in human hepatocytes through dysregulation of aerobic glycolysis and lipid metabolism. Increased glycolytic metabolism mediated by elevated expression of Glut1, glucose influx, and lactate secretion is associated with this Warburg phenotype, a classic metabolic signature also observed in cancer cells. This article brings into focus the tight interaction between HBV infection and metabolic dysfunction and how these processes facilitate the progression of end-stage liver diseases, such as hepatocellular carcinoma. We also provide evidence and models by which other viruses such as HIV and Zika disrupt their host metabolic machinery. The emergence of the immunometabolism field provides novel opportunities to take advantage of intermediary metabolites and key metabolic pathways for diagnostic and therapeutic purposes.

Increased glucose transporter-1 expression on intermediate monocytes from HIV-infected women with subclinical cardiovascular disease

OBJECTIVE

People living with HIV (PLWH) have chronic immune activation and increased cardiovascular disease (CVD) risk. Activation of monocytes and T lymphocytes causes upregulation of glucose transporter-1 (GLUT1) for efficient function. PLWH have an increased percentage of GLUT1-expressing monocytes and T lymphocytes, but it is unclear if these cells are associated with CVD. We evaluated the expression of GLUT1 and CD38 on monocyte and T lymphocyte populations from HIV-infected women with subclinical CVD.

METHODS

Participants with more than 75th percentile (n = 15) and less than 25th percentile (n = 15) age-adjusted intima-media thickness (IMT) at the right common carotid artery and bifurcation were identified from the Women's Interagency HIV Study. Groups were matched by age, race/ethnicity, smoking status, and CD4 cell count. All women were receiving suppressive antiretroviral therapy except for one high and one low IMT participant. Monocyte and T lymphocyte populations were evaluated for GLUT1 and CD38 expression using flow cytometry.

RESULTS

Intermediate monocytes from high IMT women had significantly increased expression of GLUT1 (310 MFI vs. 210 MFI, P = 0.024) (66.4% vs. 48.5%, P = 0.031) and CD38 (339 MFI vs. 211 MFI, P = 0.002) (10.5% vs. 3.8%, P = 0.0002) compared with women with low IMT. High and low IMT participants showed no differences in GLUT1 or CD38 expression on classical monocytes, nonclassical monocytes, CD4 and CD8 T lymphocytes.

CONCLUSION

GLUT1-expressing intermediate monocytes are elevated in HIV-infected women with subclinical CVD. These cells may contribute to development of CVD in PLWH and could be a novel target to limit inflammation.

A Simple Flow Cytometric Method to Measure Glucose Uptake and Glucose Transporter Expression for Monocyte Subpopulations in Whole Blood

Monocytes are innate immune cells that can be activated by pathogens and inflammation associated with certain chronic inflammatory diseases. Activation of monocytes induces effector functions and a concomitant shift from oxidative to glycolytic metabolism that is accompanied by increased glucose transporter expression. This increased glycolytic metabolism is also observed for trained immunity of monocytes, a form of innate immunological memory. Although in vitro protocols examining glucose transporter expression and glucose uptake by monocytes have been described, none have been examined by multi-parametric flow cytometry in whole blood. We describe a multi-parametric flow cytometric protocol for the measurement of fluorescent glucose analog 2-NBDG uptake in whole blood by total monocytes and the classical (CD14(++)CD16(-)), intermediate (CD14(++)CD16(+)) and non-classical (CD14(+)CD16(++)) monocyte subpopulations. This method can be used to examine glucose transporter expression and glucose uptake for total monocytes and monocyte subpopulations during homeostasis and inflammatory disease, and can be easily modified to examine glucose uptake for other leukocytes and leukocyte subpopulations within blood.