HIV and HCV activate the inflammasome in monocytes and macrophages via endosomal Toll-like receptors without induction of type 1 interferon

Targeting inflammasomes as a therapeutic potential for HIV/AIDS

Human immunodeficiency virus (HIV) infection in humans can cause a variety of symptoms. Among these, acquired immunodeficiency syndrome (AIDS) remains the most severe form. Current treatment of HIV/AIDS with antiretroviral drugs effectively inhibits HIV replication and infection and significantly extends the lifespan of HIV/AIDS patients. However, antiretroviral drugs cannot completely remove HIV from patients due to the high latency of HIV, and they possess side effects and can lead to drug resistance. HIV/AIDS remains to be an incurable disease, and new methods and drugs are still desirable. Inflammasomes were found to be activated during HIV infection and regulate AIDS progression. Previous reviews provide a simple summary of inflammasome activators and inhibitors during HIV infection without distinguishing the specific infection stage, this kind of summary does not provide any clinical target value. Here, we provide a comprehensive review of inflammasomes in HIV/AIDS according to the infection timeline and propose several inflammasome target strategies for clinical HIV/AIDS treatment. We systematacially summarized the activation and function of kinds inflammasomes during the different HIV infection stages, with the aim of providing new therapeutic targets and directions for HIV/AIDS and HIV-associated comorbidities.

Context-dependent role of sirtuin 2 in inflammation

Sirtuin 2 is a member of the sirtuin family nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases, known for its regulatory role in different processes, including inflammation. In this context, sirtuin 2 has been involved in the modulation of key inflammatory signaling pathways and transcription factors by deacetylating specific targets, such as nuclear factor κB and nucleotide-binding oligomerization domain-leucine-rich-repeat and pyrin domain-containing protein 3 (NLRP3). However, whether sirtuin 2-mediated pathways induce a pro- or an anti-inflammatory response remains controversial. Sirtuin 2 has been implicated in promoting inflammation in conditions such as asthma and neurodegenerative diseases, suggesting that its inhibition in these conditions could be a potential therapeutic strategy. Conversely, arthritis and type 2 diabetes mellitus studies suggest that sirtuin 2 is essential at the peripheral level and, thus, its inhibition in these pathologies would not be recommended. Overall, the precise role of sirtuin 2 in inflammation appears to be context-dependent, and further investigation is needed to determine the specific molecular mechanisms and downstream targets through which sirtuin 2 influences inflammatory processes in various tissues and pathological conditions. The present review explores the involvement of sirtuin 2 in the inflammation associated with different pathologies to elucidate whether its pharmacological modulation could serve as an effective strategy for treating this prevalent symptom across various diseases.

Help or Hinder: Protein Host Factors That Impact HIV-1 Replication

Interactions between human immunodeficiency virus type 1 (HIV-1) and the host factors or restriction factors of its target cells determine the cell's susceptibility to, and outcome of, infection. Factors intrinsic to the cell are involved at every step of the HIV-1 replication cycle, contributing to productive infection and replication, or severely attenuating the chances of success. Furthermore, factors unique to certain cell types contribute to the differences in infection between these cell types. Understanding the involvement of these factors in HIV-1 infection is a key requirement for the development of anti-HIV-1 therapies. As the list of factors grows, and the dynamic interactions between these factors and the virus are elucidated, comprehensive and up-to-date summaries that recount the knowledge gathered after decades of research are beneficial to the field, displaying what is known so that researchers can build off the groundwork of others to investigate what is unknown. Herein, we aim to provide a review focusing on protein host factors, both well-known and relatively new, that impact HIV-1 replication in a positive or negative manner at each stage of the replication cycle, highlighting factors unique to the various HIV-1 target cell types where appropriate.

Precision Phenotyping of Heart Failure in People with HIV: Early Insights and Challenges

PURPOSE OF REVIEW

People with HIV have an elevated risk of developing heart failure even with optimally controlled disease. In this review, we outline the various mechanisms through which HIV infection may directly and indirectly contribute to heart failure pathology and highlight the emerging relationship between HIV, chronic inflammation, and cardiometabolic disease.

RECENT FINDINGS

HIV infection leads to chronic inflammation, immune dysregulation, and metabolic imbalances even in those with well controlled disease. These dysregulations occur through several diverse mechanisms which may lead to manifestations of different phenotypes of heart failure in people with HIV. While it has long been known that people with HIV are at risk of developing heart failure, recent studies have suggested numerous complex mechanisms involving chronic inflammation, immune dysregulation, and metabolic derangement through which this may be mediated. Further comprehensive studies are needed to elucidate the precise relationship between these mechanisms and the development of different subtypes of heart failure in people with HIV.

Convergent evolution and targeting of diverse E2 epitopes by human broadly neutralizing antibodies are associated with HCV clearance

The early appearance of broadly neutralizing antibodies (bNAbs) in serum is associated with spontaneous hepatitis C virus (HCV) clearance, but to date, the majority of bNAbs have been isolated from chronically infected donors. Most of these bNAbs use the VH1-69 gene segment and target the envelope glycoprotein E2 front layer. Here, we performed longitudinal B cell receptor (BCR) repertoire analysis on an elite neutralizer who spontaneously cleared multiple HCV infections. We isolated 10,680 E2-reactive B cells, performed BCR sequencing, characterized monoclonal B cell cultures, and isolated bNAbs. In contrast to what has been seen in chronically infected donors, the bNAbs used a variety of VH genes and targeted at least three distinct E2 antigenic sites, including sites previously thought to be non-neutralizing. Diverse front-layer-reactive bNAb lineages evolved convergently, acquiring breadth-enhancing somatic mutations. These findings demonstrate that HCV clearance-associated bNAbs are genetically diverse and bind distinct antigenic sites that should be the target of vaccine-induced bNAbs.

Inflammatory Consequences: Hepatitis C Virus-Induced Inflammasome Activation and Pyroptosis

Hepatitis C virus (HCV), despite the availability of effective direct-acting antivirals (DAAs) that clear the virus from >95% of individuals treated, continues to cause significant health care burden due to disease progression that can lead to fibrosis, cirrhosis, and/or hepatocellular carcinoma. The fact that some people who are treated with DAAs still go on to develop worsening liver disease warrants further study into the immunopathogenesis of HCV. Many viral infections, including HCV, have been associated with activation of the inflammasome/pyroptosis pathway. This inflammatory cell death pathway ultimately results in cell lysis and release of inflammatory cytokines, IL-18 and IL-1β. This review will report on studies that investigated HCV and inflammasome activation/pyroptosis. This includes clinical in vivo data showing elevated pyroptosis-associated cytokines in the blood of individuals living with HCV, studies of genetic associations of pyroptosis-related genes and development of liver disease, and in vitro studies aimed at understanding the mechanism of pyroptosis induced by HCV. Finally, we discuss major gaps in understanding and outstanding questions that remain in the field of HCV-induced pyroptosis.

Advances in the mechanism of inflammasomes activation in herpes virus infection

Herpesviruses, prevalent DNA viruses with a double-stranded structure, establish enduring infections and play a part in various diseases. Despite their deployment of multiple tactics to evade the immune system, both localized and systemic inflammatory responses are triggered by the innate immune system's recognition of them. Recent progress has offered more profound understandings of the mechanisms behind the activation of the innate immune system by herpesviruses, specifically through inflammatory signaling. This process encompasses the initiation of an intracellular nucleoprotein complex, the inflammasome associated with inflammation.Following activation, proinflammatory cytokines such as IL-1β and IL-18 are released by the inflammasome, concurrently instigating a programmed pathway for cell death. Despite the structural resemblances between herpesviruses, the distinctive methods of inflammatory activation and the ensuing outcomes in diseases linked to the virus exhibit variations.The objective of this review is to emphasize both the similarities and differences in the mechanisms of inflammatory activation among herpesviruses, elucidating their significance in diseases resulting from these viral infections.Additionally, it identifies areas requiring further research to comprehensively grasp the impact of this crucial innate immune signaling pathway on the pathogenesis of these prevalent viruses.

SHIV-C109p5 NHP induces rapid disease progression in elderly macaques with extensive GI viral replication

CCR5-tropic simian/human immunodeficiency viruses (SHIV) with clade C transmitted/founder envelopes represent a critical tool for the investigation of HIV experimental vaccines and microbicides in nonhuman primates, although many such isolates lead to spontaneous viral control post infection. Here, we generated a high-titer stock of pathogenic SHIV-C109p5 by serial passage in two rhesus macaques (RM) and tested its virulence in aged monkeys. The co-receptor usage was confirmed before infecting five geriatric rhesus macaques (four female and one male). Plasma viral loads were monitored by reverse transcriptase-quantitative PCR (RT-qPCR), cytokines by multiplex analysis, and biomarkers of gastrointestinal damage by enzyme-linked immunosorbent assay. Antibodies and cell-mediated responses were also measured. Viral dissemination into tissues was determined by RNAscope. Intravenous SHIV-C109p5 infection of aged RMs leads to high plasma viremia and rapid disease progression; rapid decrease in CD4+ T cells, CD4+CD8+ T cells, and plasmacytoid dendritic cells; and wasting necessitating euthanasia between 3 and 12 weeks post infection. Virus-specific cellular immune responses were detected only in the two monkeys that survived 4 weeks post infection. These were Gag-specific TNFα+CD8+, MIP1β+CD4+, Env-specific IFN-γ+CD4+, and CD107a+ T cell responses. Four out of five monkeys had elevated intestinal fatty acid binding protein levels at the viral peak, while regenerating islet-derived protein 3α showed marked increases at later time points in the three animals surviving the longest, suggesting gut antimicrobial peptide production in response to microbial translocation post infection. Plasma levels of monocyte chemoattractant protein-1, interleukin-15, and interleukin-12/23 were also elevated. Viral replication in gut and secondary lymphoid tissues was extensive.IMPORTANCESimian/human immunodeficiency viruses (SHIV) are important reagents to study prevention of virus acquisition in nonhuman primate models of HIV infection, especially those representing transmitted/founder (T/F) viruses. However, many R5-tropic SHIV have limited fitness in vivo leading to many monkeys spontaneously controlling the virus post acute infection. Here, we report the generation of a pathogenic SHIV clade C T/F stock by in vivo passage leading to sustained viral load set points, a necessity to study pathogenicity. Unexpectedly, administration of this SHIV to elderly rhesus macaques led to extensive viral replication and fast disease progression, despite maintenance of a strict R5 tropism. Such age-dependent rapid disease progression had previously been reported for simian immunodeficiency virus but not for R5-tropic SHIV infections.

Distinct Types of Cell Death and Implications in Liver Diseases: An Overview of Mechanisms and Application

Cell death is associated with a variety of liver diseases, and hepatocyte death is a core factor in the occurrence and progression of liver diseases. In recent years, new cell death modes have been identified, and certain biomarkers have been detected in the circulation during various cell death modes that mediate liver injury. In this review, cell death modes associated with liver diseases are summarized, including some cell death modes that have emerged in recent years. We described the mechanisms associated with liver diseases and summarized recent applications of targeting cell death in liver diseases. It provides new ideas for the diagnosis and treatment of liver diseases. In addition, multiple cell death modes can contribute to the same liver disease. Different cell death modes are not isolated, and they interact with each other in liver diseases. Future studies may focus on exploring the regulation between various cell death response pathways in liver diseases.

NLRP3 Inflammasome Involvement in Heart, Liver, and Lung Diseases-A Lesson from Cytokine Storm Syndrome

Inflammation and inflammasomes have been proposed as important regulators of the host-microorganism interaction, playing a key role in morbidity and mortality due to the coronavirus disease 2019 (COVID-19) in subjects with chronic conditions and compromised immune system. The inflammasome consists of a multiprotein complex that finely regulates the activation of caspase-1 and the production and secretion of potent pro-inflammatory cytokines such as IL-1β and IL-18. The pyrin containing NOD (nucleotide-binding oligomerization domain) like receptor (NLRP) is a family of intracellular receptors, sensing patterns associated to pathogens or danger signals and NLRP3 inflammasome is the most deeply analyzed for its involvement in the innate and adaptive immune system as well as its contribution to several autoinflammatory and autoimmune diseases. It is highly expressed in leukocytes and up-regulated in sentinel cells upon inflammatory stimuli. NLRP3 expression has also been reported in B and T lymphocytes, in epithelial cells of oral and genital mucosa, in specific parenchymal cells as cardiomyocytes, and keratinocytes, and chondrocytes. It is well known that a dysregulated activation of the inflammasome is involved in the pathogenesis of different disorders that share the common red line of inflammation in their pathogenetic fingerprint. Here, we review the potential roles of the NLRP3 inflammasome in cardiovascular events, liver damage, pulmonary diseases, and in that wide range of systemic inflammatory syndromes named as a cytokine storm.

The role of pyroptosis in incomplete immune reconstitution among people living with HIV：Potential therapeutic targets

Globally, HIV infection causes significant morbidity and mortality, and is a major public health problem. Despite the fact that widespread use of antiretroviral therapy (ART) has substantially altered the natural history of HIV infection from originally being a universally lethal disease to now being a chronic medical condition for those taking appropriate treatment, approximately 10-40% of people living with HIV (PLWH) who take effective ART and maintain long-term viral suppression fail to achieve normalization of CD4 + T-cell counts. This phenomenon is referred to as incomplete immune reconstitution or immunological non-response. Although the precise mechanisms underlying this outcome have not been elucidated, recent evidence indicates that excessive pyroptosis may play a crucial role in the development of incomplete immune reconstitution. Pyroptosis is characterized by the formation of pores in the cell membrane, cell rupture, and secretion of intracellular contents and pro-inflammatory cytokines, including IL-1β and IL-18. This excessive inflammation-induced programmed cell death leads to a massive loss of CD4 + T-cells, and inflammatory consequences that may promote and sustain incomplete immune reconstitution. Herein, we review the possible pathways activated in HIV infection by inflammasomes that act as switches of pyroptosis, and the role of pyroptosis in HIV, as well as the relevance of CD4 + T-cells in incomplete immune reconstitution. We also highlight the possible mechanisms of pyroptosis involved in incomplete immune reconstitution, thus paving the way for the development of potential targets for the treatment of incomplete immune reconstitution.

Systemic cytokine and viral antigen-specific responses in hepatitis D virus RNA positive versus HDV RNA negative patients

Background

Hepatitis B virus (HBV)/Hepatitis D Virus (HDV) co-infection increases the risk of severe liver disease compared to HBV mono-infection. Adaptive immune responses to HDV are weakly detectable, and the involvement of innate immunity in the progression of HDV-related liver fibrosis is suggested. We hypothesize that an overall innate immune activation in HBV/HDV co-infection plays a role in liver disease progression and also impacts virus specific T cell response.

Methods

Sixteen HBV/HDV-co-infected-patients (median age 42y/7F/6 Asian/4 White/6 Black/15 HBeAg-) and 8 HBV monoinfected-patients (median age 39y/4F/4 Asian/3 Black/1 White/HBeAg-) with median follow-up of 5 years were enrolled. Liver fibrosis was assessed by liver stiffness measurement (LSM, FibroScan®). Proliferation of CD3 + CD4+ T cells in response to viral antigens using CFSE assays and cytokine secreting monocytes was analyzed by flow cytometry.

Results

Of 16 HBV/HDV, 11 were HDV-RNA+ (HBV-DNA 0-1,040 IU/mL), 5/11 Interferon (IFN) + Nucleos/tide Analog (NA), 3/11 NA monotherapy, median ALT 77 U/L at the time of sample collection, median LSM of 9.8. In 5 HDV RNA-, median HBV DNA 65 IU/mL, 4/5 prior IFN and/or NA, ALT 31 U/L, and median LSM 8.5 kPa. In 8 HBV controls, median HBV-DNA, ALT, LSM was 69 IU/mL, 33 U/L,5 kPa, respectively. PBMC stimulation with HBV core antigen (HBcAg) and HDV antigen (HDAg) showed weaker CD3 + CD4 + T-cell proliferation in HDV-RNA+ vs. HDV RNA- and HBV-mono-infected patients (p < 0.05). In HDV-RNA+ patients, a correlation between ALT and TNF-α (r = 0.76, p = 0.008), higher IL-10 levels and increased proportion of CD14 + TNF-α+ cells were found.

Conclusion

In summary, during HBV/HDV coinfection, HDV RNA+ patients had weaker HBV and HDV specific responses, associated with increased TNF-α + monocytes irrespective of IFN treatment.

HIV Infection: Shaping the Complex, Dynamic, and Interconnected Network of the Cytoskeleton

HIV-1 has evolved a plethora of strategies to overcome the cytoskeletal barrier (i.e., actin and intermediate filaments (AFs and IFs) and microtubules (MTs)) to achieve the viral cycle. HIV-1 modifies cytoskeletal organization and dynamics by acting on associated adaptors and molecular motors to productively fuse, enter, and infect cells and then traffic to the cell surface, where virions assemble and are released to spread infection. The HIV-1 envelope (Env) initiates the cycle by binding to and signaling through its main cell surface receptors (CD4/CCR5/CXCR4) to shape the cytoskeleton for fusion pore formation, which permits viral core entry. Then, the HIV-1 capsid is transported to the nucleus associated with cytoskeleton tracks under the control of specific adaptors/molecular motors, as well as HIV-1 accessory proteins. Furthermore, HIV-1 drives the late stages of the viral cycle by regulating cytoskeleton dynamics to assure viral Pr55Gag expression and transport to the cell surface, where it assembles and buds to mature infectious virions. In this review, we therefore analyze how HIV-1 generates a cell-permissive state to infection by regulating the cytoskeleton and associated factors. Likewise, we discuss the relevance of this knowledge to understand HIV-1 infection and pathogenesis in patients and to develop therapeutic strategies to battle HIV-1.

HIV-1 activates oxidative phosphorylation in infected CD4 T cells in a human tonsil explant model

Introduction

Human immunodeficiency virus type 1 (HIV-1) causes a chronic, incurable infection leading to immune activation and chronic inflammation in people with HIV-1 (PWH), even with virologic suppression on antiretroviral therapy (ART). The role of lymphoid structures as reservoirs for viral latency and immune activation has been implicated in chronic inflammation mechanisms. Still, the specific transcriptomic changes induced by HIV-1 infection in different cell types within lymphoid tissue remain unexplored.

Methods

In this study, we utilized human tonsil explants from healthy human donors and infected them with HIV-1 ex vivo. We performed single-cell RNA sequencing (scRNA-seq) to analyze the cell types represented in the tissue and to investigate the impact of infection on gene expression profiles and inflammatory signaling pathways.

Results

Our analysis revealed that infected CD4+ T cells exhibited upregulation of genes associated with oxidative phosphorylation. Furthermore, macrophages exposed to the virus but uninfected showed increased expression of genes associated with the NLRP3 inflammasome pathway.

Discussion

These findings provide valuable insights into the specific transcriptomic changes induced by HIV-1 infection in different cell types within lymphoid tissue. The activation of oxidative phosphorylation in infected CD4+ T cells and the proinflammatory response in macrophages may contribute to the chronic inflammation observed in PWH despite ART. Understanding these mechanisms is crucial for developing targeted therapeutic strategies to eradicate HIV-1 infection in PWH.

Heat-Killed Lacticaseibacillus paracasei Repairs Lipopolysaccharide-Induced Intestinal Epithelial Barrier Damage via MLCK/MLC Pathway Activation

Intestinal epithelial barrier function is closely associated with the development of many intestinal diseases. Heat-killed Lacticaseibacillus paracasei (HK-LP) has been shown to improve intestinal health and enhance immunity. However, the function of HK-LP in the intestinal barrier is still unclear. This study characterized the inflammatory effects of seven HK-LP (1 μg/mL) on the intestinal barrier using lipopolysaccharide (LPS) (100 μg/mL)-induced Caco-2 cells. In this study, HK-LP 6105, 6115, and 6235 were selected, and their effects on the modulation of inflammatory factors and tight junction protein expression (claudin-1, zona occludens-1, and occludin) were compared. The effect of different cultivation times (18 and 48 h) was investigated in response to LPS-induced intestinal epithelial barrier dysfunction. Our results showed that HK-LP 6105, 6115, and 6235 improved LPS-induced intestinal barrier permeability reduction and transepithelial resistance. Furthermore, HK-LP 6105, 6115, and 6235 inhibited the pro-inflammatory factors (TNF-α, IL-1β, IL-6) and increased the expression of the anti-inflammatory factors (IL-4, IL-10, and TGF-β). HK-LP 6105, 6115, and 6235 ameliorated the inflammatory response. It inhibited the nuclear factor kappa B (NF-κB) signaling pathway-mediated myosin light chain (MLC)/MLC kinase signaling pathway by downregulating the Toll-like receptor 4 (TLR4)/NF-κB pathway. Thus, the results suggest that HK-LP 6150, 6115, and 6235 may improve intestinal health by regulating inflammation and TJ proteins. Postbiotics produced by these strains exhibit anti-inflammatory properties that can protect the intestinal barrier.

The impact of cannabinoids on inflammasome signaling in HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) is a chronic disease that afflicts over 38 million people worldwide without a known cure. The advent of effective antiretroviral therapies (ART) has significantly decreased the morbidity and mortality associated with HIV-1 infection in people living with HIV-1 (PWH), thanks to durable virologic suppression. Despite this, people with HIV-1 experience chronic inflammation associated with co-morbidities. While no single known mechanism accounts for chronic inflammation, there is significant evidence to support the role of the NLRP3 inflammasome as a key driver. Numerous studies have demonstrated therapeutic impact of cannabinoids, including exerting modulatory effects on the NLRP3 inflammasome. Given the high rates of cannabinoid use in PWH, it is of great interest to understand the intersecting biology of the role of cannabinoids in HIV-1-associated inflammasome signaling. Here we describe the literature of chronic inflammation in people with HIV, the therapeutic impact of cannabinoids in PWH, endocannabinoids in inflammation, and HIV-1-associated inflammation. We describe a key interaction between cannabinoids, the NLRP3 inflammasome, and HIV-1 viral infection, which supports further investigation of the critical role of cannabinoids in HIV-1 infection and inflammasome signaling.

Infection of Pro- and Anti-Inflammatory Macrophages by Wild Type and Vaccine Strains of Measles Virus: NLRP3 Inflammasome Activation Independent of Virus Production

In humans and non-human primates, wild type (WT) measles virus (MeV) replicates extensively in lymphoid tissue and induces an innate response characteristic of NF-κB and inflammasome activation without type I interferon. In contrast, the live attenuated MeV vaccine (LAMV) replicates poorly in lymphoid tissue with little detectable in vivo cytokine production. To characterize the innate responses of macrophages to WT MeV and LAMV infection, we analyzed primary human monocyte-derived macrophages and phorbol myristic acid-matured monocytic THP-1 cells (M0) polarized to inflammatory (M1) and anti-inflammatory (M2) phenotypes 24 h after MeV infection. LAMV infected macrophages more efficiently than WT MeV but produced less virus than WT MeV-infected macrophages. Both strains induced production of NF-κB-responsive cytokines IL-6 and TNFα and inflammasome products IL-1β and IL-18 without evidence of pyroptosis. Analysis of THP-1 cells deficient in inflammasome sensors NOD-like receptor pyrin (NLRP)3, IFN-γ-inducible protein 16 (IFI16) or absent in melanoma (AIM)2; adaptor apoptosis-associated speck-like protein containing a CARD (ASC) or effector caspase 1 showed that IL-18 production was dependent on NLRP3, ASC, and caspase 1. However, M1 cells produced IL-1β in the absence of ASC or caspase 1 indicating alternate pathways for MeV-induced pro-IL-1β processing. Therefore, the innate response to in vitro infection of macrophages with both LAMV and WT MeV includes production of IL-6 and TNFα and activation of the NLRP3 inflammasome to release IL-1β and IL-18. LAMV attenuation impairs production of infectious virus but does not reduce ability to infect macrophages or innate responses to infection.

The anti-caspase 1 inhibitor VX-765 reduces immune activation, CD4+ T cell depletion, viral load, and total HIV-1 DNA in HIV-1 infected humanized mice

HIV-1 infection results in the activation of inflammasome that may facilitate viral spread and establishment of viral reservoirs. We evaluated the effects of the caspase-1 inhibitor VX-765 on HIV-1 infection in humanized NSG mice engrafted with human CD34⁺ hematopoietic stem cells. Expression of caspase-1, NLRP3, and IL-1β was increased in lymph nodes and bone marrow between day 1 and 3 after HIV-1 infection (mean fold change (FC) of 2.08, 3.23, and 6.05, p<0.001, respectively). IFI16 and AIM2 expression peaked at day 24 and coincides with increased IL-18 levels (6.89 vs 83.19 pg/ml, p=0.004), increased viral load and CD4⁺ T cells loss in blood (p<0.005 and p<0.0001, for the spleen respectively). Treatment with VX-765 significantly reduced TNF-α at day 11 (0.47 vs 2.2 pg/ml, p=0.045), IL-18 at day 22 (7.8 vs 23.2 pg/ml, p=0.04), CD4⁺ T cells (44.3% vs 36,7%, p=0.01), viral load (4.26 vs 4.89 log 10 copies/ml, p=0.027), and total HIV-1 DNA in the spleen (1 054 vs 2 889 copies /10⁶ cells, p=0.029). We demonstrated that targeting inflammasome activation early after infection may represent a therapeutic strategy towards HIV cure to prevent CD4⁺ T cell depletion and reduce immune activation, viral load, and the HIV-1 reservoir formation.

EV-A71 induced IL-1β production in THP-1 macrophages is dependent on NLRP3, RIG-I, and TLR3

Enterovirus A71 (EV-A71) is an emerging enterovirus that can cause neurological complications. Enhanced serum IL-1β levels were observed in EV-A71 patients with severe neurological symptoms. However, the roles of sensors in enterovirus-induced IL-1β production are unclear. In this study, we identified that pattern recognition receptors, including RIG-I, TLR3, and TLR8, are implicated in EV-A71-triggered IL-1β release in human macrophages. EV-A71 infection results in caspase-1 and caspase-8, which act as regulators of EV-A71-induced NLRP3 and RIG-I inflammasome activation. Moreover, knockdown of the expression of TLR3 and TLR8 decreased the released IL-1β in an NLRP3-dependent manner. Since TLR3 and TLR8 ligands promote NLRP3 inflammasome activation via caspase-8, the alternative pathway may be involved. In summary, these results indicate that activation of the NLRP3 and RIG-I inflammasomes in EV-A71-infected macrophages is mediated by caspase-1 and caspase-8 and affected by TLRs, including TLR3 and TLR8.

Significance of elevated serum and hepatic NOD-like receptor pyrin domain containing 3 (NLRP3) in hepatitis C virus-related liver disease

NOD-like receptor pyrin domain containing 3 (NLRP3) is a microbial and danger signal sensor that acts as a regulator of inflammation via activation of Caspase-1 (CASP1) and has been identified as a major contributor to human liver diseases. The present study was conducted to investigate the association between NLRP3 and the progression of hepatitis C virus (HCV)-related liver disease. Serum NLRP3 levels were analyzed in 49 patients with chronic HCV infection and 18 healthy controls and liver tissues from 34 patients were examined to assess the protein expression of NLRP3 and its activation marker CASP1 using immunohistochemical staining. The results showed that the median serum NLRP3 levels was significantly higher in HCV-infected patients compared with healthy controls (1040 pg/ml vs 695 pg/ml respectively, P < 0.001) and were positively correlated with hepatic NLRP3 and CASP1 expression (r = 0.749, P < 0.001 and r = 0.557, P = 0.001 respectively). The NLRP3 levels in serum and the liver significantly increased with worsening liver pathology and showed positive correlations with serum aminotransferases levels, HCV viremia, and albumin-bilirubin score (P < 0.05). The receiver operating characteristic curve analysis revealed a high diagnostic performance of serum NLRP3 in determining the extent of liver necroinflammation, fibrosis, and steatosis (area under the curve = 0.951, 0.971, and 0.917 respectively, P < 0.001). In conclusion, NLRP3 plays an important role in liver disease progression during HCV infection via CASP1 activation and might be a promising therapeutic target. Serum NLRP3 could be an additional biomarker for liver inflammation and fibrosis.

Evaluating the Cardiovascular Risk in an Aging Population of People With HIV: The Impact of Hepatitis C Virus Coinfection

Background People with HIV (PWH) are at an increased risk of cardiovascular disease (CVD) with an unknown added impact of hepatitis C virus (HCV) coinfection. We aimed to identify whether HCV coinfection increases the risk of type 1 myocardial infarction (T1MI) and if the risk differs by age. Methods and Results We used data from NA-ACCORD (North American AIDS Cohort Collaboration on Research and Design) from January 1, 2000, to December 31, 2017, PWH (aged 40-79 years) who had initiated antiretroviral therapy. The primary outcome was an adjudicated T1MI event. Those who started direct-acting HCV antivirals were censored at the time of initiation. Crude incidence rates per 1000 person-years were calculated for T1MI by calendar time. Discrete time-to-event analyses with complementary log-log models were used to estimate adjusted hazard ratios and 95% CIs for T1MI among those with and without HCV. Among 23 361 PWH, 4677 (20%) had HCV. There were 89 (1.9%) T1MIs among PWH with HCV and 314 (1.7%) among PWH without HCV. HCV was not associated with increased T1MI risk in PWH (adjusted hazard ratio, 0.98 [95% CI, 0.74-1.30]). However, the risk of T1MI increased with age and was amplified in those with HCV (adjusted hazard ratio per 10-year increase in age, 1.85 [95% CI, 1.38-2.48]) compared with those without HCV (adjusted hazard ratio per 10-year increase in age,1.30 [95% CI, 1.13-1.50]; P<0.001, test of interaction). Conclusions HCV coinfection was not significantly associated with increased T1MI risk; however, the risk of T1MI with increasing age was greater in those with HCV compared with those without, and HCV status should be considered when assessing CVD risk in aging PWH.

Flaviviridae Nonstructural Proteins: The Role in Molecular Mechanisms of Triggering Inflammation

Members of the Flaviviridae family are posing a significant threat to human health worldwide. Many flaviviruses are capable of inducing severe inflammation in humans. Flaviviridae nonstructural proteins, apart from their canonical roles in viral replication, have noncanonical functions strongly affecting antiviral innate immunity. Among these functions, antagonism of type I IFN is the most investigated; meanwhile, more data are accumulated on their role in the other pathways of innate response. This review systematizes the last known data on the role of Flaviviridae nonstructural proteins in molecular mechanisms of triggering inflammation, with an emphasis on their interactions with TLRs and RLRs, interference with NF-κB and cGAS-STING signaling, and activation of inflammasomes.

Methamphetamine induces transcriptional changes in cultured HIV-infected mature monocytes that may contribute to HIV neuropathogenesis

HIV-associated neurocognitive impairment (HIV-NCI) persists in 15-40% of people with HIV (PWH) despite effective antiretroviral therapy. HIV-NCI significantly impacts quality of life, and there is currently no effective treatment for it. The development of HIV-NCI is complex and is mediated, in part, by the entry of HIV-infected mature monocytes into the central nervous system (CNS). Once in the CNS, these cells release inflammatory mediators that lead to neuroinflammation, and subsequent neuronal damage. Infected monocytes may infect other CNS cells as well as differentiate into macrophages, thus contributing to viral reservoirs and chronic neuroinflammation. Substance use disorders in PWH, including the use of methamphetamine (meth), can exacerbate HIV neuropathogenesis. We characterized the effects of meth on the transcriptional profile of HIV-infected mature monocytes using RNA-sequencing. We found that meth mediated an upregulation of gene transcripts related to viral infection, cell adhesion, cytoskeletal arrangement, and extracellular matrix remodeling. We also identified downregulation of several gene transcripts involved in pathogen recognition, antigen presentation, and oxidative phosphorylation pathways. These transcriptomic changes suggest that meth increases the infiltration of mature monocytes that have a migratory phenotype into the CNS, contributing to dysregulated inflammatory responses and viral reservoir establishment and persistence, both of which contribute to neuronal damage. Overall, our results highlight potential molecules that may be targeted for therapy to limit the effects of meth on HIV neuropathogenesis.

An adverse outcome pathway-based approach to assess aurantio-obtusin-induced hepatotoxicity

Cassiae semen (CS), a traditional Chinese medicine, has various bioactivities in preclinical and clinical practice. Aurantio-obtusin (AO) is a major anthraquinone (AQ) ingredient derived from CS, and has drawn public concerns over its potential hepatotoxicity. We previously found that AO induces hepatic necroinflammation by activating NOD-like receptor protein 3 inflammasome signaling. However, the mechanisms contributing to AO-motivated hepatotoxicity remain unclear. Herein, we evaluated hepatotoxic effects of AO on three liver cell lines by molecular and biochemical analyses. We found that AO caused cell viability inhibition and biochemistry dysfunction in the liver cells. Furthermore, AO elevated reactive oxygen species (ROS), followed by mitochondrial dysfunction (decreases in mitochondrial membrane potential and adenosine triphosphate) and apoptosis (increased Caspase-3, Cleaved caspase-3, Cytochrome c and Bax expression, and decreased Bcl-2 expression). We also found that AO increased the lipid peroxidation (LPO) and enhanced ferroptosis by activating cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA)-cAMP response element-binding (CREB) pathway (increases in PKA, p-CREB, acyl-CoA synthetase long chain family member 4). Based on these results, we used an AOP framework to explore the mechanisms underlying AO's hepatotoxicity. It starts from molecular initiating event (ROS), and follows two critical toxicity pathways (i.e., mitochondrial dysfunction-mediated apoptosis and LPO-enhanced ferroptosis) over a series of key events (KEs) to the adverse outcome of hepatotoxicity. The results of an assessment confidence in the adverse outcome pathway (AOP) framework supported the evidence concordance in dose-response, temporal and incidence relationships between KEs in AO-induced hepatotoxicity. This study's findings offer a novel toxicity pathway network for AO-caused hepatotoxicity.

PRRSV Infection Induces Gasdermin D-Driven Pyroptosis of Porcine Alveolar Macrophages through NLRP3 Inflammasome Activation

For more than 3 decades, mounting evidence has associated porcine reproductive and respiratory syndrome virus (PRRSV) infection with late-term abortions and stillbirths in sows and respiratory disease in piglets, causing enormous economic losses to the global swine industry. However, to date, the underlying mechanisms of PRRSV-triggered cell death have not been well clarified, especially in the pulmonary inflammatory injury characterized by the massive release of pro-inflammatory factors. Here, we demonstrated that PRRSV infection triggered gasdermin D-mediated host pyroptosis in vitro and in vivo. Mechanistically, PRRSV infection triggered disassembly of the trans-Golgi network (TGN); the dispersed TGN then acted as a scaffold for NLRP3 activation through phosphatidylinositol-4-phosphate. In addition, PRRSV replication-transcription complex (RTC) formation stimulated TGN dispersion and pyroptotic cell death. Furthermore, our results indicated that TMEM41B, an endoplasmic reticulum (ER)-resident host protein, functioned as a crucial host factor in the formation of PRRSV RTC, which is surrounded by the intermediate filament network. Collectively, these findings uncover new insights into clinical features as previously unrecognized mechanisms for PRRSV-induced pathological effects, which may be conducive to providing treatment options for PRRSV-associated diseases and may be conserved during infection by other highly pathogenic viruses. IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the pathogens responsible for major economic losses in the global swine industry. Characterizing the detailed process by which PRRSV induces cell death pathways will help us better understand viral pathogenesis and provide implications for therapeutic intervention against PRRSV. Here, we showed that PRRSV infection induces GSDMD-driven host pyroptosis and IL-1β secretion through NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome activation in vitro and in vivo. Furthermore, the molecular mechanisms of PRRSV-induced NLRP3 inflammasome activation and pyroptosis are elucidated here. The dispersed trans-Golgi network (TGN) induced by PRRSV serves as a scaffold for NLRP3 aggregation into multiple puncta via phosphatidylinositol 4-phosphate (PtdIns4P). Moreover, the formation of PRRSV replication-transcription complex is essential for TGN dispersion and host pyroptosis. This research advances our understanding of the PRRSV-mediated inflammatory response and cell death pathways, paving the way for the development of effective treatments for PRRSV diseases.

Peste Des Petits Ruminants Virus N Protein Is a Critical Proinflammation Factor That Promotes MyD88 and NLRP3 Complex Assembly

Inflammatory responses play a central role in host defense against invading pathogens. Peste des petits ruminants virus (PPRV) causes highly contagious acute or subacute disease of small ruminants. However, the precise mechanism by which PPRV regulates inflammatory responses remains unknown. Here, we revealed a novel mechanism by which PPRV induces inflammation. Our study showed that PPRV induced the secretion of interleukin 1β (IL-1β) by activating the NF-κB signaling pathway and the NLRP3 inflammasome. Moreover, PPRV replication and protein synthesis were essential for NLRP3 inflammasome activation. Importantly, PPRV N protein promoted NF-κB signaling pathway and NLRP3 inflammasome via direct binding of MyD88 and NLPR3, respectively, and induced caspase-1 cleavage and IL-1β maturation. Biochemically, N protein interacted with MyD88 to potentiate the assembly of MyD88 complex and interacted with NLPR3 to facilitate NLRP3 inflammasome complex assembly by forming an N-NLRP3-ASC ring-like structure, leading to IL-1β secretion. These findings demonstrate a new function of PPRV N protein as an important proinflammation factor and identify a novel underlying mechanism modulating inflammasome assembly and function induced by PPRV. IMPORTANCE An important part of the innate immune response is the activation of NF-κB signaling pathway and NLPR3 inflammasome, which is induced upon exposure to pathogens. Peste des petits ruminants virus (PPRV) is a highly contagious virus causing fever, stomatitis, and pneumoenteritis in goats by inducing many proinflammatory cytokines. Although the NF-κB signaling pathway and NLRP3 inflammasome play an important role in regulating host immunity and viral infection, the precise mechanism by which PPRV regulates inflammatory responses remains unknown. This study demonstrates that PPRV induces inflammatory responses. Mechanistically, PPRV N protein facilitates the MyD88 complex assembly by directly binding to MyD88 and promotes the NLRP3 inflammasome complex assembly by directly binding to NLRP3 to form ring-like structures of N-NLRP3-ASC. These findings provide insights into the prevention and treatment of PPRV infection.

Herpesviruses and Inflammasomes: One Sensor Does Not Fit All

Herpesviruses are ubiquitous double-stranded DNA viruses that cause lifelong infections and are associated with a variety of diseases. While they have evolved multiple mechanisms to evade the immune system, they are all recognized by the innate immune system, which can lead to both localized and systemic inflammation. A more recently appreciated mechanism of herpesvirus innate immune activation is through inflammasome signaling. The inflammasome is an intracellular multiprotein complex that, when activated, leads to the release of proinflammatory cytokines, including IL-1β and IL-18, and activation of the inflammatory programed cell death pathway known as pyroptosis. Despite the herpesviruses sharing a similar structure, their mechanisms of inflammasome activation and the consequences of inflammasome activation in cases of virus-associated disease are not uniform. This review will highlight the similarities and differences among herpesviruses with regard to their mechanisms of inflammasome activation and impacts on diseases caused by herpesviruses. Furthermore, it will identify areas where additional studies are warranted to better understand the impact of this important innate immune signaling program on the pathogenesis of these common viruses.

RNA-Cholesterol Nanoparticles Function as Potent Immune Activators via TLR7 and TLR8

The innate immune system senses viral and bacterial ribonucleic acid (RNA) via pattern recognition receptors (PRR) leading to subsequent activation of the immune system. One group of RNA sensors is formed by endosomal/lysosomal Toll-like receptors (TLR) such as TLR7 and TLR8. During viral or bacterial infection, immunostimulatory RNA is part of the pathogen reaching the endosomal/lysosomal compartment after cellular uptake. Synthetic single-stranded or double-stranded oligoribonucleotides (ORN) can mimic RNA from pathogens and are widely used as activating ligands for TLR7 and TLR8. However, one limitation in the use of synthetic ORN driven immune stimulation is the need for transfection reagents for RNA delivery into cells. Here we demonstrate that the conjugation of cholesterol to a double-stranded version of immunostimulatory RNA40 strongly enhanced RNA uptake into monocytes and plasmacytoid dendritic cells when compared to naked RNA. Cholesterol-conjugated RNA (RNA-chol) formed nanoparticles that were superior to RNA-liposomes complexes in regard to induction of type I interferon from human and murine plasmacytoid dendritic cells as well as proinflammatory cytokine production (e.g. TNF-α, IL12p70 or IL-6) in human monocytes. Furthermore, the RNA40-chol induced cytokines in human monocyte cultures supported T_H1 and T_FH cell differentiation underscoring a strong adjuvant function of RNA-chol nanoparticles for adaptive immune responses. In summary, cholesterol-conjugated immunostimulatory RNA forms nanoparticles and functions as a potent immune adjuvant in human and murine immune cells. It further simplifies the use of immunostimulatory RNA by avoiding the need for liposomal transfection reagents.

Differential Cytokine Signatures of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and Influenza Infection Highlight Key Differences in Pathobiology

BACKGROUND

Several inflammatory cytokines are upregulated in severe coronavirus disease 2019 (COVID-19). We compared cytokines in COVID-19 versus influenza to define differentiating features of the inflammatory response to these pathogens and their association with severe disease. Because elevated body mass index (BMI) is a known risk factor for severe COVID-19, we examined the relationship of BMI to cytokines associated with severe disease.

METHODS

Thirty-seven cytokines and chemokines were measured in plasma from 135 patients with COVID-19, 57 patients with influenza, and 30 healthy controls. Controlling for BMI, age, and sex, differences in cytokines between groups were determined by linear regression and random forest prediction was used to determine the cytokines most important in distinguishing severe COVID-19 and influenza. Mediation analysis was used to identify cytokines that mediate the effect of BMI and age on disease severity.

RESULTS

Interleukin-18 (IL-18), IL-1β, IL-6, and tumor necrosis factor-α (TNF-α) were significantly increased in COVID-19 versus influenza patients, whereas granulocyte macrophage colony-stimulating factor, interferon-γ (IFN-γ), IFN-λ1, IL-10, IL-15, and monocyte chemoattractant protein 2 were significantly elevated in the influenza group. In subgroup analysis based on disease severity, IL-18, IL-6, and TNF-α were elevated in severe COVID-19, but not in severe influenza. Random forest analysis identified high IL-6 and low IFN-λ1 levels as the most distinct between severe COVID-19 and severe influenza. Finally, IL-1RA was identified as a potential mediator of the effects of BMI on COVID-19 severity.

CONCLUSIONS

These findings point to activation of fundamentally different innate immune pathways in severe acute respiratory syndrome coronavirus 2 and influenza infection, and emphasize drivers of severe COVID-19 to focus both mechanistic and therapeutic investigations.

Toll-Like Receptor (TLR) Signaling Enables Cyclic GMP-AMP Synthase (cGAS) Sensing of HIV-1 Infection in Macrophages

HIV-1 replicates in cells that express a wide array of innate immune sensors and may do so simultaneously with other pathogens. How a coexisting innate immune stimulus influences the outcome of HIV-1 sensing, however, remains poorly understood. Here, we demonstrate that the activation of a second signaling pathway enables a cyclic GMP-AMP synthase (cGAS)-dependent type I interferon (IFN-I) response to HIV-1 infection. We used RNA sequencing to determine that HIV-1 alone induced few or no signs of an IFN-I response in THP-1 cells. In contrast, when supplemented with suboptimal levels of bacterial lipopolysaccharide (LPS), HIV-1 infection triggered the production of elevated levels of IFN-I and significant upregulation of interferon-stimulated genes. LPS-mediated enhancement of IFN-I production upon HIV-1 infection, which was observed in primary macrophages, was lost by blocking reverse transcription and with a hyperstable capsid, pointing to viral DNA being an essential immunostimulatory molecule. LPS also synergistically enhanced IFN-I production by cyclic GMP-AMP (cGAMP), a second messenger of cGAS. These observations suggest that the DNA sensor cGAS is responsible for a type I IFN response to HIV-1 in concert with LPS receptor Toll-like receptor 4 (TLR4). Small amounts of a TLR2 agonist also cooperate with HIV-1 to induce type I IFN production. These results demonstrate how subtle immunomodulatory activity renders HIV-1 capable of eliciting an IFN-I response through positive cross talk between cGAS and TLR sensing pathways.

Aurantio-obtusin induces hepatotoxicity through activation of NLRP3 inflammasome signaling

Aurantio-obtusin (AO) is a major anthraquinone (AQ) compound derived from Cassiae semen (CS). Although pharmacological studies have shown that the CS extracts can serve as effective agents in preclinical and clinical practice, AQ-induced hepatotoxicity in humans has attracted widespread attention. To explore whether AO induces hepatotoxicity and its underlying mechanisms, we exposed larval zebrafish and mice to AO. We found that AO delayed yolk sac absorption, and increased liver area and inflammation in the larval zebrafish. This inflammation was manifested as an increase in liver neutrophils and the up-regulated mRNA expression of interleukin-6 (Il-6) and tumor necrosis factor-α (Tnf-α) in the larval zebrafish. Furthermore, a pharmacokinetics study showed that AO was quickly absorbed into the blood and rapidly metabolized in the mice. Of note, AO induced hepatotoxicity in a gender-dependent manner, characterized by liver dysfunction, increased hepatocyte necrosis with inflammatory infiltration, and up-regulated mRNAs of Il-6, Tnf-α and monocyte chemotactic protein 1(Mcp1) in the female mice after 28-day oral administration. It also highlighted that AO triggered NOD-like receptor protein (NLRP) signaling in the female mice, as evidenced by the increased NLRP3, Caspase-1, pro-IL-1β, IL-1β and IL-18. Finally, we found that AO led to a significant increase in potassium calcium-activated channel, subfamily N, member 4 (KCNN4) and reactive oxygen species (ROS) levels, along with decreased nuclear factor kappa B p65 (NF-κB p65), in the female mouse livers. In conclusion, AO induced hepatotoxicity by activating NLRP3 inflammasome signaling, at least in part, through increased KCNN4 and ROS production, and NF-κB inhibition.

Proto-pyroptosis: An Ancestral Origin for Mammalian Inflammatory Cell Death Mechanism in Drosophila melanogaster

Pyroptosis has been described in mammalian systems to be a form of programmed cell death that is important in immune function through the subsequent release of cytokines and immune effectors upon cell bursting. This form of cell death has been increasingly well-characterized in mammals and can occur using alternative routes however, across phyla, there has been little evidence for the existence of pyroptosis. Here we provide evidence for an ancient origin of pyroptosis in an in vivo immune scenario in Drosophila melanogaster. Crystal cells, a type of insect blood cell, were recruited to wounds and ruptured subsequently releasing their cytosolic content in a caspase-dependent manner. This inflammatory-based programmed cell death mechanism fits the features of pyroptosis, never before described in an in vivo immune scenario in insects and relies on ancient apoptotic machinery to induce proto-pyroptosis. Further, we unveil key players upstream in the activation of cell death in these cells including the apoptosome which may play an alternative role akin to the inflammasome in proto-pyroptosis. Thus, Drosophila may be a suitable model for studying the functional significance of pyroptosis in the innate immune system.

Pyroptosis in Steatohepatitis and Liver Diseases

Pyroptosis is an inflammatory form of regulated cell death, which functions in the clearance of intracellularly replicating pathogens by cell lysis in order to induce further immune response. Since the discovery of the gasdermin (GSDM) family, pyroptosis has attracted attention in a wide range of inflammatory diseases such as nonalcoholic steatohepatitis and other liver diseases. Due to the cleavage of GSDMs by different caspases, the amino-terminal GSDM fragments form membrane pores essential for pyroptosis that facilitate the release of inflammatory cytokines by loss of ionic gradient and membrane rupture. In this review, we address the key molecular and cellular processes that induce pyroptosis in the liver and its significance in the pathogenesis of common liver diseases in different human and experimental mice studies.

pMGF505-7R determines pathogenicity of African swine fever virus infection by inhibiting IL-1β and type I IFN production

Inflammatory factors and type I interferons (IFNs) are key components of host antiviral innate immune responses, which can be released from the pathogen-infected macrophages. African swine fever virus (ASFV) has developed various strategies to evade host antiviral innate immune responses, including alteration of inflammatory responses and IFNs production. However, the molecular mechanism underlying inhibition of inflammatory responses and IFNs production by ASFV-encoded proteins has not been fully understood. Here we report that ASFV infection only induced low levels of IL-1β and type I IFNs in porcine alveolar macrophages (PAMs), even in the presence of strong inducers such as LPS and poly(dA:dT). Through further exploration, we found that several members of the multigene family 360 (MGF360) and MGF505 strongly inhibited IL-1β maturation and IFN-β promoter activation. Among them, pMGF505-7R had the strongest inhibitory effect. To verify the function of pMGF505-7R in vivo, a recombinant ASFV with deletion of the MGF505-7R gene (ASFV-Δ7R) was constructed and assessed. As we expected, ASFV-Δ7R infection induced higher levels of IL-1β and IFN-β compared with its parental ASFV HLJ/18 strain. ASFV infection-induced IL-1β production was then found to be dependent on TLRs/NF-κB signaling pathway and NLRP3 inflammasome. Furthermore, we demonstrated that pMGF505-7R interacted with IKKα in the IKK complex to inhibit NF-κB activation and bound to NLRP3 to inhibit inflammasome formation, leading to decreased IL-1β production. Moreover, we found that pMGF505-7R interacted with and inhibited the nuclear translocation of IRF3 to block type I IFN production. Importantly, the virulence of ASFV-Δ7R is reduced in piglets compared with its parental ASFV HLJ/18 strain, which may due to induction of higher IL-1β and type I IFN production in vivo. Our findings provide a new clue to understand the functions of ASFV-encoded pMGF505-7R and its role in viral infection-induced pathogenesis, which might help design antiviral agents or live attenuated vaccines to control ASF.

African swine fever virus (ASFV) causes a highly lethal swine disease that is currently present in many countries, severely affecting the pig industry. Despite extensive research, effective vaccines and antiviral strategies are still lacking and relevant gaps in knowledge of the fundamental biology of the viral infection cycle exist. In this study, we found that ASFV infection only induced low levels of IL-1β and type I IFNs in porcine alveolar macrophages (PAMs) and identified that pMGF505-7R, a member of the multigene family 505 (MGF505), strongly inhibited IL-1β and IFN-β production. ASFV lacking the MGF505-7R gene (ASFV-Δ7R) had reduced virulence in piglets and induced increased IL-1β and IFN-β production in PAMs and pigs compared with its parental ASFV HLJ/18 strain. Our results significantly increase our knowledge to understand functions of ASFV-encoded pMGF505-7R and its roles in pathogenesis, which may shed light on future research on live attenuated vaccines and antiviral strategies.

The Inflammatory Relationship Between Hepatitis C Virus With Coronary and Carotid Atherosclerosis

Hepatitis C virus (HCV), a global health concern, has been linked to various hepatic and extrahepatic deleterious manifestations. Several observational studies have either supported the increased likelihood of coronary and carotid atherosclerosis after infection with HCV or refuted it. To date, there has been no clear consensus to support either train of thought, as randomized, controlled clinical trials have not been completed. In this review, we first discuss articles that support the notion that HCV infection leads to increased plaque formation due to systemic inflammation and then focus on articles that refute this idea. From the literature, we do know that both inflammatory and lipid processes play a role in plaque formation, and thus both components are important in the successful treatment of atherosclerosis. Based on our review of the literature, we do believe that HCV-infected individuals are at an increased risk for more severe coronary artery disease than their healthy counterparts. Although there is no irrefutable evidence that links HCV infection with plaque formation and/or rupture, cardioprotective measures should be taken to reduce poor health outcomes, especially in those individuals who are already at risk of coronary disease.

Differential recognition of HIV-stimulated IL-1β and IL-18 secretion through NLR and NAIP signalling in monocyte-derived macrophages

Macrophages are important drivers of pathogenesis and progression to AIDS in HIV infection. The virus in the later phases of the infection is often predominantly macrophage-tropic and this tropism contributes to a chronic inflammatory and immune activation state that is observed in HIV patients. Pattern recognition receptors of the innate immune system are the key molecules that recognise HIV and mount the inflammatory responses in macrophages. The innate immune response against HIV-1 is potent and elicits caspase-1-dependent pro-inflammatory cytokine production of IL-1β and IL-18. Although, NLRP3 has been reported as an inflammasome sensor dictating this response little is known about the pattern recognition receptors that trigger the “priming” signal for inflammasome activation, the NLRs involved or the HIV components that trigger the response. Using a combination of siRNA knockdowns in monocyte derived macrophages (MDMs) of different TLRs and NLRs as well as chemical inhibition, it was demonstrated that HIV Vpu could trigger inflammasome activation via TLR4/NLRP3 leading to IL-1β/IL-18 secretion. The priming signal is triggered via TLR4, whereas the activation signal is triggered by direct effects on Kv1.3 channels, causing K⁺ efflux. In contrast, HIV gp41 could trigger IL-18 production via NAIP/NLRC4, independently of priming, as a one-step inflammasome activation. NAIP binds directly to the cytoplasmic tail of HIV envelope protein gp41 and represents the first non-bacterial ligand for the NAIP/NLRC4 inflammasome. These divergent pathways represent novel targets to resolve specific inflammatory pathologies associated with HIV-1 infection in macrophages.

It has been previously shown that inflammasome activation can be triggered during viral infection to produce the active cytokines IL-1β and IL-18. Our study represents a significant advance, as we now show that in fact there are distinct NLR inflammasome complexes and viral ligands for IL-1β secretion (Vpu) compared to IL-18 secretion (gp41) in response to HIV-1.

Most importantly, we show that the HIV envelope protein gp41 represents the first non-bacterial ligand for the assembly of the NAIP/NLRC4 inflammasome. HIV gp41 is a viroporin, and thus our data demonstrates for the first time that the NAIP/NLRC4 inflammasome assembles for all pore-forming proteins, irrespective of whether they have a viral or bacterial origin. This is critical for the host antiviral response and has broad implications for innate immunity in general.

NLRP3 and IL-1β Gene Expression Is Elevated in Monocytes From HIV-Treated Patients With Neurocognitive Disorders

BACKGROUND

Systemic immune activation and inflammation in chronic HIV infection are driving factors of non-AIDS-related events, including neurocognitive impairment. The role of inflammasome in monocytes from patients with HIV infection has been extensively studied, but its association with the extent of neurocognitive dysfunction has been poorly investigated.

METHODS

We enrolled 79 HIV-positive patients; 44 with varying levels of HIV-associated neurocognitive disorder (HAND) and 35 without and 8 healthy donors. HAND subtypes included asymptomatic neurocognitive impairment (asymptomatic neurocognitive impairment; n = 19), mild neurocognitive disorder (MND; n = 17), and HIV-associated dementia (n = 8). We quantified plasmatic concentrations of proinflammatory cytokines (TNF-α, IL-6, IL-17A, IL-1β, and IFN-γ) for all HIV patients, and the mRNA expression of genes involved in the inflammasome activity (NLRP3, PYCARD, NAIP, AIM2, IL-1β, and IL-18) in monocytes of a subgroup of 28 HIV patients and 8 healthy donors.

RESULTS

HIV patients' plasma concentrations of IFN-γ, IL-1β, and IL-17A were undetectable. Levels of TNF-α and IL-6 were similar among the HIV patient groups. A trend toward an increased expression of inflammasome genes according to neurocognitive disorder severity was observed. Of note, the NLRP3 mRNA relative expression was higher in MND compared with other groups, and IL-1β was lower in MND than HIV-associated dementia patients.

CONCLUSIONS

Changes in inflammasome components in circulating monocytes according to different HAND severity suggest that NLRP3 may be a possible biomarker or target to better understand and treat the link between systemic inflammation and neurocognitive impairment in HIV infection.

Pathophysiological Roles of Mucosal-Associated Invariant T Cells in the Context of Gut Microbiota-Liver Axis

Mucosal-associated invariant T (MAIT) cells are a subset of T lymphocytes expressing a semi-invariant T-cell receptor (TCR) present as TCR Vα7.2-Jα33 in humans and TCR Vα19-Jα33 in mice. They are activated by ligands produced during microbial biosynthesis of riboflavin that is presented by major histocompatibility complex class I-related (MR1) molecules on antigen-presenting cells. MAIT cells also possess interleukin (IL)-12 and IL-18 receptors and can be activated by the respective cytokines released from microbially stimulated antigen-presenting cells. Therefore, MAIT cells can be involved in bacterial and viral defenses and are a significant part of the human immune system. They are particularly abundant in the liver, an organ serving as the second firewall of gut microbes next to the intestinal barrier. Therefore, the immune functions of MAIT cells are greatly impacted by changes in the gut-microbiota and play important roles in the gut-liver pathogenesis axis. In this review, we discuss the nature and mechanisms of MAIT cell activation and their dynamics during different types of liver pathogenesis conditions. We also share our perspectives on important aspects that should be explored further to reveal the exact roles that MAIT cells play in liver pathogenesis in the context of the gut microbiota.

Innate Immunity in Hepatitis C Virus Infection

Activation and viral control of the innate immune response are hallmarks of hepatitis C virus (HCV) infection and are major determinants of spontaneous clearance or progression to chronic infection and liver disease. In this review, we provide a contemporary overview of how HCV is sensed by the host cell to trigger innate immune activation and the mechanisms deployed by the virus to evade this response. Type I and III interferons (IFNs) are crucial mediators of antiviral innate immunity against HCV, and we specifically highlight the importance of IFN-λ host genetics for the outcome of HCV infection. Last, we focus on the proinflammatory responses elicited by HCV infection and describe our current understanding of how interleukin (IL)-1β signaling and cross talk between the IL-1β and IFN signaling pathways lead to sustained inflammation and increased risk of liver pathology.

The Inflammasome Components NLRP3 and ASC Act in Concert with IRGM To Rearrange the Golgi Apparatus during Hepatitis C Virus Infection

Numerous pathogens can affect cellular homeostasis and organelle dynamics. Hepatitis C virus (HCV) triggers Golgi fragmentation through the immunity-related GTPase M (IRGM), a resident Golgi protein, to enhance its lipid supply for replication.

Hepatitis C virus (HCV) infection triggers Golgi fragmentation through the Golgi-resident protein immunity-related GTPase M (IRGM). Here, we report the roles of NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) and ASC (apoptosis-associated speck-like protein containing a caspase activation and recruitment domain [CARD]), two inflammasome components, in the initial events leading to this fragmentation. We show that ASC resides at the Golgi with IRGM at homeostasis. Upon infection, ASC dissociates from both IRGM and the Golgi and associates with HCV-induced NLRP3. NLRP3 silencing inhibits Golgi fragmentation. ASC silencing disrupts the Golgi structure in both control and infected cells and reduces the localization of IRGM at the Golgi. IRGM depletion in the ASC-silenced cells cannot totally restore the Golgi structure. These data highlight a role for ASC, upstream of the formation of the inflammasome, in regulating IRGM through its control on the Golgi. A similar mechanism occurs in response to nigericin treatment, but not in cells infected with another member of the Flaviviridae family, Zika virus (ZIKV). We propose a model for a newly ascribed function of the inflammasome components in Golgi structural remodeling during certain stimuli.

IMPORTANCE Numerous pathogens can affect cellular homeostasis and organelle dynamics. Hepatitis C virus (HCV) triggers Golgi fragmentation through the immunity-related GTPase M (IRGM), a resident Golgi protein, to enhance its lipid supply for replication. Here, we reveal the role of the inflammasome components NLRP3 and ASC in this process, thus uncovering a new interplay between effectors of inflammation and viral infection or stress. We show that the inflammasome component ASC resides at the Golgi under homeostasis and associates with IRGM. Upon HCV infection, ASC is recruited to NLRP3 and dissociates from IRGM, causing Golgi fragmentation. Our results uncover that aside from their known function in the inflammation response, these host defense regulators also ensure the maintenance of intact intracellular structure in homeostasis, while their activation relieves factors leading to Golgi remodeling.

Immune Dysregulation in Myocardial Fibrosis, Steatosis, and Heart Failure: Current Insights from HIV and the General Population

PURPOSE OF REVIEW

HIV is an independent risk factor for heart failure (HF). Cardiac imaging studies in people with HIV (PWH) have identified myocardial pathologies, namely fibrosis and steatosis, that likely contribute to the higher risk of HF. In this review, we survey existing epidemiological, clinical, and mechanistic literature to identify potential pathways that may contribute to the burden of myocardial fibrosis and steatosis among PWH.

RECENT FINDINGS

Multiple cohort studies over the past 20 years have demonstrated a roughly 2-fold higher risk of incident HF in PWH, as well as a disproportionate burden of myocardial fibrosis and steatosis in PWH without HF. Both myocardial fibrosis and steatosis are known contributors to HF in adults without HIV. Pathways involving the NLRP3 inflammasome, TGF-β1, and adipocyte dysfunction are known to play a crucial role in the development of myocardial fibrosis and steatosis. Upregulation of these pathways in HIV due to direct effects of viral proteins, persistent immune dysregulation, gut epithelial breakdown and dysbiosis, and toxicities from antiretroviral therapy may contribute to myocardial dysfunction in HIV. Understanding these pathways may lead to more precise diagnostic and therapeutic targets to curb HF in PWH. During the past three decades, observational and mechanistic studies have provided important insights into risk factors and pathways that may contribute to the increased HF risk in PWH. Future work is needed to characterize these pathways more precisely in mechanistic studies of PWH, with the goal of ultimately deriving valuable targets for prevention, early diagnosis, and treatment of HF in PWH.

Immunotherapy of hepatocellular carcinoma with infection of hepatitis B or C virus

Hepatocellular carcinoma (HCC) has one of highest mortalities globally amongst cancers, but has limited therapeutic options once in the advanced stage. Hepatitis B or C virus infection are the most common drivers for HCC carcinogenesis, triggering chronic liver inflammation and adding to the complexity of the immune microecosystem of HCC. The emergence of immunotherapy has afforded a new avenue of therapeutic options for patients with advanced HCC with a history of hepatitis B or C virus infection. This article reviews the change of immunity elicited by hepatitis B or C virus infection, the immune feature of HCC, and the clinical evidence for immunotherapy in advanced HCC and discusses future directions in this field.

Interplays between inflammasomes and viruses, bacteria (pathogenic and probiotic), yeasts and parasites

In recent years, scientists studying the molecular mechanisms of inflammation have discovered an amazing phenomenon - the inflammasome - a component of the innate immune system that can regulate the functional activity of effector cells during inflammation. At present, it is known that inflammasomes are multimolecular complexes (cytosolic multiprotein oligomers of the innate immune system) that contain many copies of receptors recognizing the molecular structures of cell-damaging factors and pathogenic agents. Inflammasomes are mainly formed in myeloid cells, and their main function is participation in the cleavage of the pro-IL-1β and pro-IL-18 cytokines into their biologically active forms (IL-1β, IL-18). Each type of microorganism influences particular inflammasome activation, and long-term exposure of the organism to viruses, bacteria, yeasts or parasites, among others, can induce uncontrolled inflammation and autoinflammatory diseases. Therefore, this review aims to present the most current scientific data on the molecular interplay between inflammasomes and particular microorganisms. Knowledge about the mechanisms responsible for the interaction between the host and certain types of microorganisms could contribute to the individuation of innovative strategies for the treatment of uncontrolled inflammation targeting a specific type of inflammasome activated by a specific type of pathogen.

HIV-2-Infected Macrophages Produce and Accumulate Poorly Infectious Viral Particles

A significant proportion of HIV-2-infected patients exhibit natural virological control that is generally absent from HIV-1-infected patients. Along with CD4⁺ T cells, HIV-1 targets macrophages which may contribute to viral spreading and the latent reservoir. We have studied the relationship between macrophages and HIV-2, focusing on post-entry steps. HIV-2-infected monocyte-derived macrophages (MDMs) produced substantial amounts of viral particles that were largely harbored intracellularly. New viruses assembled at the limiting membrane of internal compartments similar to virus-containing compartments (VCCs) described for HIV-1. VCCs from MDMs infected with either virus shared protein composition and morphology. Strikingly, HIV-2 Gag was mostly absent from the cytosol and almost exclusively localized to the VCCs, whereas HIV-1 Gag was distributed in both locations. Ultrastructural analyses of HIV-2-infected MDMs revealed the presence of numerous VCCs containing both immature and mature particles in the lumen. HIV-2 particles produced de novo by MDMs were poorly infectious in reporter cells and in transmission to activated T cells through a process that appeared independent of BST2 restriction. Rather than being involved in viral spreading, HIV-2-infected macrophages may represent a cell-associated source of viral antigens that can participate in the immune control of HIV-2 infection.

What's in a prick? Vaccines and the cardiovascular system

Evidence suggests a crucial role for vaccines in cardiovascular disease, mediated not only by disease prevention but also by immunomodulatory effects. This review attempts to briefly present the effects of pathogens and vaccines on the cardiovascular system and potential mechanisms for the development of vaccines against cardiovascular diseases per se. Current epidemiological evidence regarding vaccine effectiveness in different categories of heart disease is discussed, as well as current international guidelines' recommendations. In summary, cardiologists should strive to promote vaccination against specific pathogens with proven beneficial effects on cardiovascular diseases.

NLRP3 Inflammasome Signaling as a Link Between HIV-1 Infection and Atherosclerotic Cardiovascular Disease

36.9 million people worldwide are living with HIV-1. The disease remains incurable and HIV-infected patients have increased risk of atherosclerosis. Inflammation is a key driver of atherosclerosis, but no targeted molecular therapies have been developed to reduce cardiovascular risk in people with HIV-1 (PWH). While the mechanism is unknown, there are several important inflammatory signaling events that are implicated in the development of chronic inflammation in PWH and in the inflammatory changes that lead to atherosclerosis. Here we describe the pro-inflammatory state of HIV-1 infection that leads to increased risk of cardiovascular disease, the role of the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome in HIV-1 infection, the role of the NLRP3 inflammasome in cardiovascular disease (CVD), and outline a model whereby HIV-1 infection can lead to atherosclerotic disease through NLRP3 inflammasome activation. Our discussion highlights the literature supporting HIV-1 infection as a stimulator of the NLRP3 inflammasome as a driver of atherosclerosis.

Hepatitis C Virus and Hepatocellular Carcinoma: When the Host Loses Its Grip

Chronic infection with hepatitis C virus (HCV) is a major cause of hepatocellular carcinoma (HCC). Novel treatments with direct-acting antivirals achieve high rates of sustained virologic response; however, the HCC risk remains elevated in cured patients, especially those with advanced liver disease. Long-term HCV infection causes a persistent and accumulating damage of the liver due to a combination of direct and indirect pro-oncogenic mechanisms. This review describes the processes involved in virus-induced disease progression by viral proteins, derailed signaling, immunity, and persistent epigenetic deregulation, which may be instrumental to develop urgently needed prognostic biomarkers and as targets for novel chemopreventive therapies.

Herpes simplex virus type 1 inflammasome activation in proinflammatory human macrophages is dependent on NLRP3, ASC, and caspase-1

The proinflammatory cytokines interleukin (IL)-1β and IL-18 are products of activation of the inflammasome, an innate sensing system, and important in the pathogenesis of herpes simplex virus type 1 (HSV-1). The release of IL-18 and IL-1β from monocytes/macrophages is critical for protection from HSV-1 based on animal models of encephalitis and genital infection, yet if and how HSV-1 activates inflammasomes in human macrophages is unknown. To investigate this, we utilized both primary human monocyte derived macrophages and human monocytic cell lines (THP-1 cells) with various inflammasome components knocked-out. We found that HSV-1 activates inflammasome signaling in proinflammatory primary human macrophages, but not in resting macrophages. Additionally, HSV-1 inflammasome activation in THP-1 cells is dependent on nucleotide-binding domain and leucine-rich repeat-containing receptor 3 (NLRP3), apoptosis-associated speck-like molecule containing a caspase recruitment domain (ASC), and caspase-1, but not on absent in melanoma 2 (AIM2), or gamma interferon-inducible protein 16 (IFI16). In contrast, HSV-1 activates non-canonical inflammasome signaling in proinflammatory macrophages that results in IL-1β, but not IL-18, release that is independent of NLRP3, ASC, and caspase-1. Ultraviolet irradiation of HSV-1 enhanced inflammasome activation, demonstrating that viral replication suppresses inflammasome activation. These results confirm that HSV-1 is capable of activating the inflammasome in human macrophages through an NLRP3 dependent process and that the virus has evolved an NLRP3 specific mechanism to inhibit inflammasome activation in macrophages.

Extracellular vesicle-mediated amyloid transfer to neural progenitor cells: implications for RAGE and HIV infection

Amyloid beta (Aβ) deposition was demonstrated to be elevated in the brains of HIV-infected patients and associated with neurocognitive decline; however, the mechanisms of these processes are poorly understood. The goal of the current study was to address the hypothesis that Aβ can be transferred via extracellular vesicles (ECVs) from brain endothelial cells to neural progenitor cells (NPCs) and that this process can contribute to abnormal NPC differentiation. Mechanistically, we focused on the role of the receptor for advanced glycation end products (RAGE) and activation of the inflammasome in these events. ECVs loaded with Aβ (Aβ-ECVs) were readily taken up by NPCs and Aβ partly colocalized with the inflammasome markers ASC and NLRP3 in the nuclei of the recipient NPCs. This colocalization was affected by HIV and RAGE inhibition by a high-affinity specific inhibitor FPS-ZM1. Blocking RAGE resulted also in an increase in ECV number produced by brain endothelial cells, decreased Aβ content in ECVs, and diminished Aβ-ECVs transfer to NPC nuclei. Interestingly, both Aβ-ECVs and RAGE inhibition altered NPC differentiation. Overall, these data indicate that RAGE inhibition affects brain endothelial ECV release and Aβ-ECVs transfer to NPCs. These events may modulate ECV-mediated amyloid pathology in the HIV-infected brain and contribute to the development of HIV-associated neurocognitive disorders.

Inflammasome in HIV infection: Lights and shadows

The importance of inflammasome, and related cytokines IL-1ß and IL-18, in host defense against pathogens is well documented, however, at the same time, dysregulation of inflammasome has been associated to multifactorial diseases characterized by chronic inflammation (i.e.: metabolic disorders, cardiovascular diseases, neurodegenerative diseases, autoimmunity, cancer). Inflammasome activation has been described in response to HIV-1 and possibly contributes to the resistance against virus establishment, however, on the other hand, when viral infection becomes chronic, independently from antiretroviral therapy, the increase constitutive activation of inflammasome has been eventually associated to a worse prognosis, raising the question about the role played by inflammasome and/or some specific receptors in this context. Due to the chance to imply targeted therapies that inhibit inflammasome activation and/or cytokines release, it will be important to define the impact of the complex in the pathogenesis of HIV. The purpose of this review is to depict the double-faced inflammasome role in HIV-1 infection, trying to unveil whether besides its role in first line defense against the virus, it exerts a harmful effect during the chronic phase of infection.