Exosomes as Conduits: Facilitating Hepatitis B Virus-Independent Hepatitis D Virus Transmission and Propagation in Hepatocytes.

A number of research studies, including ours, have spotlighted exosomes as critical facilitators of viral dissemination. While hepatitis B virus (HBV) transmission through exosomes has been studied, the focus on its satellite virus, the hepatitis delta virus (HDV), has been unexplored in this context. HDV, although being a defective virus, can replicate its genome autonomously within hepatocytes, independently of HBV. Investigations on Huh7 cells revealed an intriguing phenomenon: the HDV proteins, S-HDAg and L-HDAg, are transmitted between cells without a complete viral structure. Detailed analysis further revealed that the expression of these proteins not only bolstered exosome secretion but also ensured their enrichment within these vesicles. Our experimental approach utilized transfection of various plasmids to examine the role of HDV RNA and proteins in the process. One salient finding was the differential propagation of the HDV proteins S-HDAg and L-HDAg, suggesting intricate molecular mechanisms behind their transmission. Notably, the purity of our exosome preparations was monitored using markers such as TSG101 and CD81. Importantly, these exosomes were found to carry both HDV RNA and proteins, highlighting their role in HDV dissemination. This novel study underscores the role of exosomes in mediating the transmission of HDV components between hepatocytes independent of HBV. These revelations about the exosomal pathway of HDV transmission provide a foundation for the development of innovative therapeutic strategies against HDV infections.

Harnessing Autophagy to Overcome Antigen-Specific T-Cell Dysfunction: Implication for People Living with HIV-1.

Like other chronic viral infections, HIV-1 persistence inhibits the development of antigen-specific memory T-cells, resulting in the exhaustion of the immune response and chronic inflammation. Autophagy is a major lysosome-dependent mechanism of intracellular large-target degradation such as lipid and protein aggregates, damaged organelles, and intracellular pathogens. Although it is known that autophagy may target HIV-1 for elimination, knowledge of its function as a metabolic contributor in such viral infection is only in its infancy. Recent data show that elite controllers (EC), who are HIV-1-infected subjects with natural and long-term antigen (Ag)-specific T-cell protection against the virus, are characterized by distinct metabolic autophagy-dependent features in their T-cells compared to other people living with HIV-1 (PLWH). Despite durable viral control with antiretroviral therapy (ART), HIV-1-specific immune dysfunction does not normalize in non-controller PLWH. Therefore, the hypothesis of inducing autophagy to strengthen their Ag-specific T-cell immunity against HIV-1 starts to be an enticing concept. The aim of this review is to critically analyze promises and potential limitations of pharmacological and dietary interventions to activate autophagy in an attempt to rescue Ag-specific T-cell protection among PLWH.

Obesity alters monocyte developmental trajectories to enhance metastasis.

Obesity is characterized by chronic systemic inflammation and enhances cancer metastasis and mortality. Obesity promotes breast cancer metastasis to lung in a neutrophil-dependent manner; however, the upstream regulatory mechanisms of this process remain unknown. Here, we show that obesity-induced monocytes underlie neutrophil activation and breast cancer lung metastasis. Using mass cytometry, obesity favors the expansion of myeloid lineages while restricting lymphoid cells within the peripheral blood. RNA sequencing and flow cytometry revealed that obesity-associated monocytes resemble professional antigen-presenting cells due to a shift in their development and exhibit enhanced MHCII expression and CXCL2 production. Monocyte induction of the CXCL2-CXCR2 axis underlies neutrophil activation and release of neutrophil extracellular traps to promote metastasis, and enhancement of this signaling axis is observed in lung metastases from obese cancer patients. Our findings provide mechanistic insight into the relationship between obesity and cancer by broadening our understanding of the interactive role that myeloid cells play in this process.

Autophagy-dependent glutaminolysis drives superior IL21 production in HIV-1-specific CD4 T cells.

The maintenance of a strong IL21 production in memory CD4 T cells, especially in HIV-1-specific cells, represents a major correlate of natural immune protection against the virus. However, the molecular mechanisms underlying IL21 production during HIV-1 infection, which is only elevated among the naturally protected elite controllers (EC), are still unknown. We recently found out that lipophagy is a critical immune mediator that control an antiviral metabolic state following CD8A T cell receptor engagement, playing an important role in the natural control of HIV-1 infection. This led us to investigate whether the beneficial role of a strong macroautophagy/autophagy, could also be used to ensure effective IL21 production as well. Herein, we confirm that after both polyclonal and HIV-1-specific activation, memory CD4 T cells (Mem) from EC display enhanced activity of the autophagy-mediated proteolysis compared to ART. Our results indicate that the enhanced autophagy activity in EC was controlled by the energy-sensing PRKAA1 (protein kinase AMP-activated catalytic subunit alpha 1). We further confirmed the critical role of the autophagy-mediated proteolysis in the strong IL21 production in EC by using BECN1 gene silencing as well as protease, PRKAA1, and lysosomal inhibitors. Finally, we established that high autophagy-mediated proteolysis in EC fuels their cellular rates of mitochondrial respiration due to glutaminolysis. Our data confirm the critical role of autophagy in dictating the metabolic input, which is required not only to ensure protective cytotoxic CD8A T cell responses, but also to provide strong IL21 production among antiviral CD4 T cells.Abbreviations: AKG: alpha-ketoglutarate; ART: patients under antiretroviral therapy; ATG7: autophagy related 7; BaF: bafilomycin A1; BECN1: beclin 1; Chloro.: chloroquine; EC: elite controllers; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; FOXO3: forkhead box O3; GLS: glutaminase; GLUD1: glutamate dehydrogenase 1; HIVneg: HIV-1-uninfected control donors; IFNG/IFN-γ: interferon gamma; IL21: interleukin 21; MTOR: mechanistic target of rapamycin kinase; PBMC: peripheral blood mononuclear cells; PRKAA1: protein kinase AMP-activated catalytic subunit alpha 1; SQSTM1: sequestosome 1; TCA: tricarboxylic acid cycle; ULK1: unc-51 like autophagy activating kinase.

Entry of the Varicellovirus Canid herpesvirus 1 into Madin-Darby canine kidney epithelial cells is pH-independent and occurs via a macropinocytosis-like mechanism but without increase in fluid uptake.

Canid herpesvirus 1 (CHV-1) is a Varicellovirus that causes self-limiting infections in adult dogs but morbidity and mortality in puppies. Using a multipronged approach, we discovered the CHV-1 entry pathway into Madin-Darby canine kidney (MDCK) epithelial cells. We found that CHV-1 triggered extensive host cell membrane lamellipodial ruffling and rapid internalisation of virions in large, uncoated vacuoles, suggestive of macropinocytosis. Treatment with inhibitors targeting key macropinocytosis factors, including inhibitors of Na+ /H+ exchangers, F-actin, myosin light-chain kinase, protein kinase C, p21-activated kinase, phosphatidylinositol-3-kinase and focal adhesion kinase, significantly reduced viral replication. Moreover, the effect was restricted to exposure to the inhibitors early in infection, confirming a role for the macropinocytic machinery during entry. The profile of inhibitors also suggested a role for signalling via integrins and receptor tyrosine kinases in viral entry. In contrast, inhibitors of clathrin, caveolin, microtubules and endosomal acidification did not affect CHV-1 entry into MDCK cells. We found that the virus colocalised with the fluid-phase uptake marker dextran; however, surprisingly, CHV-1 infection did not enhance the uptake of dextran. Thus, our results indicate that CHV-1 uses a macropinocytosis-like, pH-independent entry pathway into MDCK cells, which nevertheless is not based on stimulation of fluid uptake. TAKE AWAYS: CHV-1 enters epithelial cells via a macropinocytosis-like mechanism. CHV-1 induces extensive lamellipodial ruffling. CHV-1 entry into MDCK cells is pH-independent.

The RyfA small RNA regulates oxidative and osmotic stress responses and virulence in uropathogenic Escherichia coli.

Urinary tract infections (UTIs) are a common bacterial infectious disease in humans, and strains of uropathogenic Escherichia coli (UPEC) are the most frequent cause of UTIs. During infection, UPEC must cope with a variety of stressful conditions in the urinary tract. Here, we demonstrate that the small RNA (sRNA) RyfA of UPEC strains is required for resistance to oxidative and osmotic stresses. Transcriptomic analysis of the ryfA mutant showed changes in expression of genes associated with general stress responses, metabolism, biofilm formation and genes coding for cell surface proteins. Inactivation of ryfA in UPEC strain CFT073 decreased urinary tract colonization in mice and the ryfA mutant also had reduced production of type 1 and P fimbriae (pili), adhesins which are known to be important for UTI. Furthermore, loss of ryfA also reduced UPEC survival in human macrophages. Thus, ryfA plays a key regulatory role in UPEC adaptation to stress, which contributes to UTI and survival in macrophages.

Latest developments in tryptophan metabolism: Understanding its role in B cell immunity.

One of the most essential and important building blocks of life is the tryptophan amino acid. As such, the pathways surrounding its metabolism are often crucial for the maintenance of proper cell activity and homeostasis. The ratios of tryptophan to kynurenine, mainly mediated by indoleamine 2,3-dioxygenase activity, is a key parameter in the inflammation as well as immunomodulation of both aseptic and septic diseases. As a result, several studies have been published to better understand the mechanisms by which the tryptophan pathways lead to such outcomes. Many have focused on gut health and cells associated with the given environment, the majority of which constitute regulatory T cells and T helper 17 cells. However, recent studies have highlighted the role of this molecular pathway on its capacity to modulate B cells functions and humoral immunity. Accordingly, the focus of this short review is to examine the key tryptophan pathways and their impact on B cells demonstrated by those studies. A better understanding of the role of tryptophan and its metabolites is crucial for its use in disease prevention and treatments.

Lipophagy confers a key metabolic advantage that ensures protective CD8A T-cell responses against HIV-1.

Although macroautophagy/autophagy has been proposed as a critical defense mechanism against HIV-1 by targeting viral components for degradation, its contribution as a catabolic process in providing optimal anti-HIV-1 immunity has never been addressed. The failure to restore proper antiviral CD8A/CD8 T-cell immunity, especially against HIV-1, is still the major limitation of current antiretroviral therapies. Consequently, it is of clinical imperative to provide new strategies to enhance the function of HIV-1-specific CD8A T-cells in patients under antiretroviral treatments (ART). Here, we investigated whether targeting autophagy activity could be an optional solution to make this possible. Our data show that, after both polyclonal and HIV-1-specific activation, CD8A T-cells from ART displayed reduced autophagy-dependent degradation of lysosomal contents when compared to naturally HIV-1 protected elite controllers (EC). We further confirmed in EC, by using specific BECN1 gene silencing and lysosomal inhibitors, the critical role of active autophagy in superior CD8A T-cell protection against HIV-1. More importantly, we found that an IL21 treatment was effective in rescuing the antiviral CD8A T-cell immunity from ART in an autophagy-dependent manner. Finally, we established that IL21-dependent rescue occurred due to the enhanced degradation of endogenous lipids via autophagy, referred to as lipophagy, which fueled the cellular rates of mitochondrial beta-oxidation. In summary, our data show that autophagy/lipophagy can be considered as a therapeutic tool to elicit functional antiviral CD8 T-cell responses. Our results also provide additional insights toward the development of improved T-cell-based prevention and cure strategies against HIV-1.Abbreviations: ART: patients under antiretroviral therapy; BaF: bafilomycin A1; BECN1: beclin 1; CEF: cytomegalo-, Epstein-Barr- and flu-virus peptide pool; Chloro.: chloroquine; EC: elite controllers; FAO: fatty acid beta-oxidation; HIVneg: HIV-1-uninfected control donors; IFNG/IFN-γ: interferon gamma; IL21: interleukin 21; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PBMC: peripheral blood mononuclear cells; SQSTM1: sequestosome 1; ULK1: unc-51 like autophagy activating kinase 1.

Cannabinoid-Induced Immunomodulation during Viral Infections: A Focus on Mitochondria.

This review examines the impact of cannabinoids on viral infections, as well as its effects on the mitochondria of the nervous and immune system. The paper conveys information about the beneficial and negative impacts of cannabinoids on viral infections, especially HIV-1. These include effects on the inflammatory response as well as neuroprotective effects. We also explore non-apoptotic mitochondrial pathways modulated by the activity of cannabinoids, resulting in modifications to cellular functions. As a large part of the literature derives from studies of the nervous system, we first compile the information related to mitochondrial functions in this system, particularly through the CB1 receptor. Finally, we reflect on how this knowledge could complement what has been demonstrated in the immune system, especially in the context of the CB2 receptor and Ca2+ uptake. The overall conclusion of the review is that cannabinoids have the potential to affect a broad range of cell types through mitochondrial modulation, be it through receptor-specific action or not, and that this pathway has a potential implication in cases of viral infection.

Plasticity in T-cell mitochondrial metabolism: A necessary peacekeeper during the troubled times of persistent HIV-1 infection.

The notion of immuno-metabolism refers to the crosstalk between key metabolic pathways and the development/maintenance of protective immunity in the context of physiological processes and anti-microbial defenses. Enthusiasm for immuno-metabolism in the context of HIV-1 infection, especially among T-cell lineages, continues to grow over time as science opens new therapeutic perspectives to limit viral pathogenesis and to boost anti-viral responses. The idea of "metabolism as a therapeutic target" is called metabolic reprogramming and is based on the use of specific metabolism-targeting drugs that are currently available for cancer therapy. In this review, we will focus on the evidence that shows the key role of mitochondria, the cell's powerhouses, and their ability to use diverse metabolic resources (referred to as metabolic plasticity) in providing optimal immune T-cell protection among HIV-1-infected patients. Conversely, we highlight observations indicating that mitochondria metabolic dysfunction associated with excessive glucose dependency, a phenomenon reported as "Warburg effect", results in the inability to mount and maintain effective T-cell-dependent immunity during persistent HIV-1 infection. Therefore, helping mitochondria to regain the metabolic plasticity and allow specific T-cells to adapt and thrive under unfavorable environmental conditions during HIV-1 infection may represent the next generation of combinatory treatment options for patients.

USP18 is a significant driver of memory CD4 T-cell reduced viability caused by type I IFN signaling during primary HIV-1 infection.

The loss of Memory CD4 T-cells (Mem) is a major hallmark of HIV-1 immuno-pathogenesis and occurs early during the first months of primary infection. A lot of effort has been put into understanding the molecular mechanisms behind this loss, yet they still have not been fully identified. In this study, we unveil the unreported role of USP18 in the deleterious effects of sustained type I IFN signaling on Mem, including HIV-1-specific CD4 T-cells. We find that interfering with IFN-I signaling pathway in infected patients, notably by targeting the interferon-stimulated gene USP18, resulted in reduced PTEN expression similar to those observed in uninfected control donors. We show that AKT activation in response to cytokine treatment, T-cell receptor (TcR) triggering, as well as HIV-1 Gag stimulation was significantly improved in infected patients when PTEN or USP18 were inhibited. Finally, our data demonstrate that higher USP18 in Mem from infected patients prevent proper cell survival and long-lasting maintenance in an AKT-dependent manner. Altogether, we establish a direct role for type I IFN/USP18 signaling in the maintenance of total and virus-specific Mem and provide a new mechanism for the reduced survival of these populations during primary HIV-1 infection.

Deciphering natural control of HIV-1: A valuable strategy to achieve antiretroviral therapy termination.

Antiretroviral therapy (ART) has dramatically reduced HIV-1-associated morbidity and mortality, and has transformed HIV-1 infection into a manageable chronic condition by suppressing viral replication. However, despite recent patient care improvements, ART still fails to cure HIV-1 infection due to the inability to counteract immune defects and metabolic disturbances that are associated with residual inflammation alongside viral persistence. Life-long drug administration also results in multiple side-effects in patients including lipodystrophy and insulin resistance. Thus, it is critical to find new ways to reduce the length of treatment and facilitate the termination of ART, for example by boosting protective immunity. The rare ability of some individuals to naturally control HIV-1 infection despite residual inflammation could be exploited to identify molecular mechanisms involved in host protection that may function as potential therapeutic targets. In this review, we highlight evidence illustrating the molecular and metabolic advantages of HIV-1 controllers over ART treated patients that contribute to the maintenance of effective antiviral immunity.

Sustained IFN-I Expression during Established Persistent Viral Infection: A "Bad Seed" for Protective Immunity.

Type I interferons (IFN-I) are one of the primary immune defenses against viruses. Similar to all other molecular mechanisms that are central to eliciting protective immune responses, IFN-I expression is subject to homeostatic controls that regulate cytokine levels upon clearing the infection. However, in the case of established persistent viral infection, sustained elevation of IFN-I expression bears deleterious effects to the host and is today considered as the major driver of inflammation and immunosuppression. In fact, numerous emerging studies place sustained IFN-I expression as a common nexus in the pathogenesis of multiple chronic diseases including persistent infections with the human immunodeficiency virus type 1 (HIV-1), simian immunodeficiency virus (SIV), as well as the rodent-borne lymphocytic choriomeningitis virus clone 13 (LCMV clone 13). In this review, we highlight recent studies illustrating the molecular dysregulation and resultant cellular dysfunction in both innate and adaptive immune responses driven by sustained IFN-I expression. Here, we place particular emphasis on the efficacy of IFN-I receptor (IFNR) blockade towards improving immune responses against viral infections given the emerging therapeutic approach of blocking IFNR using neutralizing antibodies (Abs) in chronically infected patients.