Frontline Science: HIV infection of Kupffer cells results in an amplified proinflammatory response to LPS

Acute Hepatitis due to Primary Human Immunodeficiency Virus Infection

The acute retroviral syndrome may present with diverse systemic manifestations and laboratory abnormalities. Here we present a rare case of primary human immunodeficiency virus (HIV) infection causing severe acute hepatitis. Liver histopathology demonstrated a pattern of lymphocytic inflammation consistent with acute hepatitis, high levels of HIV proviral DNA were detected within liver tissue, and immunofluorescence showed HIV p24 antigen within immune and parenchymal cells including hepatocytes. We review the literature pertaining to HIV infection of cell compartments within the liver and discuss the implications for HIV-associated acute liver disease.

Macrophages: Key Cellular Players in HIV Infection and Pathogenesis

Although cells of the myeloid lineages, including tissue macrophages and conventional dendritic cells, were rapidly recognized, in addition to CD4+ T lymphocytes, as target cells of HIV-1, their specific roles in the pathophysiology of infection were initially largely neglected. However, numerous studies performed over the past decade, both in vitro in cell culture systems and in vivo in monkey and humanized mouse animal models, led to growing evidence that macrophages play important direct and indirect roles as HIV-1 target cells and in pathogenesis. It has been recently proposed that macrophages are likely involved in all stages of HIV-1 pathogenesis, including virus transmission and dissemination, but above all, in viral persistence through the establishment, together with latently infected CD4+ T cells, of virus reservoirs in many host tissues, the major obstacle to virus eradication in people living with HIV. Infected macrophages are indeed found, very often as multinucleated giant cells expressing viral antigens, in almost all lymphoid and non-lymphoid tissues of HIV-1-infected patients, where they can probably persist for long period of time. In addition, macrophages also likely participate, directly as HIV-1 targets or indirectly as key regulators of innate immunity and inflammation, in the chronic inflammation and associated clinical disorders observed in people living with HIV, even in patients receiving effective antiretroviral therapy. The main objective of this review is therefore to summarize the recent findings, and also to revisit older data, regarding the critical functions of tissue macrophages in the pathophysiology of HIV-1 infection, both as major HIV-1-infected target cells likely found in almost all tissues, as well as regulators of innate immunity and inflammation during the different stages of HIV-1 pathogenesis.

Risk Stratification of Advanced Fibrosis in Patients With Human Immunodeficiency Virus and Hepatic Steatosis Using the Fibrosis-4, Nonalcoholic Fatty Liver Disease Fibrosis, and BARD Scores

Background

Nonalcoholic fatty liver disease (NAFLD) and subsequent progression to fibrosis is increasingly prevalent in people with HIV (PWH). We used noninvasive methods to stratify risk and identify associated factors of advanced fibrosis in PWH with NAFLD.

Methods

We conducted a retrospective study of PWH in our clinic from 2005 to 2022. We used liver imaging or biopsy reports to identify cases of hepatic steatosis after excluding specified etiologies. We used the Fibrosis-4 (FIB-4), NAFLD Fibrosis (NFS), and body mass index, aspartate transaminase/alanine transaminase ratio, and diabetes score scores to stratify fibrosis. We used logistic regression to identify factors associated with advanced fibrosis.

Results

Among 3959 PWH in care, 1201 had available imaging or liver biopsies. After exclusions, 114 of 783 PWH had evidence of hepatic steatosis (14.6%). Most were male (71.1%), with a median age of 47 years, and median body mass index of 30.1 kg/m2. Approximately 24% had lean NAFLD (ie, body mass index < 25 kg/m2). Based on the FIB-4 and NFS, 34 (29.8%) and 36 (31.6%) had advanced fibrosis, whereas 1 in 4 had low risk of fibrosis based on FIB-4, NFS, and BARD scores. In adjusted analysis using FIB-4, advanced fibrosis was associated with age > 45 years (adjusted odds ratio, 6.29; 95% confidence interval, 1.93-20.50) and hypoalbuminemia (adjusted odds ratio, 9.45; 95% confidence interval, 2.45-32.52) in addition to elevated transaminases and thrombocytopenia, whereas using the NFS did not identify associations with advanced fibrosis.

Conclusions

We found 14.6% of PWH had NAFLD, with 1 in 3 having advanced fibrosis. Our study provides practical insights into fibrosis risk stratification in HIV primary care settings.

Risk Stratification of Advanced Fibrosis in HIV Patients With Hepatic Steatosis Using the NAFLD Fibrosis and BARD Scores

Background

Nonalcoholic fatty liver disease (NAFLD) is increasingly prevalent in people with HIV (PWH), yet the risk factors for disease progression are poorly understood, due to inadequate surveillance. We employed non-invasive methods to estimate the prevalence and associated factors of advanced NAFLD in PWH.

Methods

We conducted a retrospective study of PWH enrolled in our clinic from 2005 to 2022. We employed imaging (ultrasound, computer tomography, magnetic resonance imaging, and transient elastography) or biopsy reports to identify cases of hepatic steatosis. We excluded patients with harmful alcohol use, hepatitis B or C infection, and other specified etiologies. We used the NAFLD Fibrosis Score (NFS), BARD Score, AST to Platelet Index (APRI), and Fibrosis-4 (FIB-4) Score to stratify fibrosis. We used logistic regression to identify predictors of advanced fibrosis.

Results

Among 3959 PWH in care, 1201 had available imaging or liver biopsies. After exclusions, 114 of the remaining 783 had evidence of hepatic steatosis (prevalence 14.6%). The majority were male (71.1%), with mean age 46.1 years, and mean body mass index (BMI) 31.4 ± 8.1 kg/m2. About 24% had lean NAFLD (BMI < 25 kg/m2). Based on the NFS, 27.2% had advanced fibrosis, which was corroborated by estimates from the other scores. In adjusted regression analysis, advanced fibrosis was associated with BMI > 35 kg/m2 (4.43, 1.27-15.48), thrombocytopenia (4.85, 1.27-18.62) and hypoalbuminemia (9.01, 2.39-33.91).

Conclusion

We found a NAFLD prevalence of 14.6%, with 27.2% of cases having advanced fibrosis. Our study provides practical insights into the surveillance of NAFLD in PWH.

Enteropathy and gut dysbiosis as obstacles to achieve immune recovery in undetectable people with HIV: a clinical view of evidence, successes, and projections

Immune performance following antiretroviral therapy initiation varies among patients. Despite achieving viral undetectability, a subgroup of patients fails to restore CD4+ T-cell counts during follow-up, which exposes them to non-AIDS defining comorbidities and increased mortality. Unfortunately, its mechanisms are incompletely understood, and no specific treatment is available. In this review, we address some of the pathophysiological aspects of the poor immune response from a translational perspective, with emphasis in the interaction between gut microbiome, intestinal epithelial dysfunction, and immune system, and we also discuss some studies attempting to improve immune performance by intervening in this vicious cycle.

HIV DNA persists in hepatocytes in people with HIV-hepatitis B co-infection on antiretroviral therapy

BACKGROUND

HIV can infect multiple cells in the liver including hepatocytes, Kupffer cells and infiltrating T cells, but whether HIV can persist in the liver in people with HIV (PWH) on suppressive antiretroviral therapy (ART) remains unknown.

METHODS

In a prospective longitudinal cohort of PWH and hepatitis B virus (HBV) co-infection living in Bangkok, Thailand, we collected blood and liver biopsies from 18 participants prior to and following ART and quantified HIV and HBV persistence using quantitative (q)PCR and RNA/DNAscope. Antiretroviral (ARV) drug levels were quantified using mass spectroscopy.

FINDINGS

In liver biopsies taken prior to ART, HIV DNA and HIV RNA were detected by qPCR in 53% (9/17) and 47% (8/17) of participants respectively. Following a median ART duration of 3.4 years, HIV DNA was detected in liver in 61% (11/18) of participants by either qPCR, DNAscope or both, but only at very low and non-quantifiable levels. Using immunohistochemistry, HIV DNA was observed in both hepatocytes and liver infiltrating CD4+ T cells on ART. HIV RNA was not detected in liver biopsies collected on ART, by either qPCR or RNAscope. All ARVs were clearly detected in liver tissue.

INTERPRETATION

Persistence of HIV DNA in liver in PWH on ART represents an additional reservoir that warrants further investigation.

FUNDING

National Health and Medical Research Council of Australia (Project Grant APP1101836, 1149990, and 1135851); This project has been funded in part with federal funds from the National Cancer Institute, National Institutes of Health, under Contract No. 75N91019D00024.

Causes and outcomes of hepatic fibrosis in persons living with HIV

PURPOSE OF REVIEW

The epidemiology of liver disease in people living with HIV has evolved since the arrival of effective hepatitis C virus (HCV) treatment. Nonalcoholic fatty liver disease (NAFLD) in HIV patients is highly prevalent while hepatitis D, hepatitis E, and occult hepatitis B remain underappreciated. We discuss mechanisms of fibrosis in HIV and review clinical outcomes of HIV-associated liver diseases.

RECENT FINDINGS

HIV-HCV co-infection is receding as a cause of progressive liver disease, but fibrosis biomarkers after HCV treatment remain elevated. Antiretroviral therapy (ART) with anti-hepatitis B virus (HBV) activity promotes stable liver disease, but oversimplifying ART regimens in unrecognized suppressed HBV may lead to activation of HBV. A high prevalence of fibrosis and rapid progression of fibrosis are seen in HIV-associated NAFLD, with visceral fat as a major risk factor. Newer ART such as integrase strand inhibitors may have limited intrinsic hepatoxicity but do increase weight, which may secondarily lead to hepatic steatosis. Promising therapies for HIV-associated NAFLD include tesamorelin and CCR5 blockade agents.

SUMMARY

Our understanding of the natural history and pathogenesis of liver diseases in HIV has advanced and adapted to the changing landscape of liver disease in this population. Future research should evaluate long-term clinical and histological outcomes, prevention strategies, and treatment options to improve morbidity and mortality in HIV-related liver diseases.

Improvement of liver metabolic activity in people with advanced HIV after antiretroviral therapy initiation

OBJECTIVE

Evaluating hepatic metabolic changes in people with HIV (PWH) with advanced disease, before and after antiretroviral therapy (ART) initiation, using [ 18 F]-fluorodeoxyglucose (FDG) PET-computed tomography (PET/CT). FDG PET/CT noninvasively quantifies glucose metabolism in organs.

DESIGN/METHODS

Forty-eight viremic PWH (CD4 + cell counts <100 cells/μl) underwent FDG PET/CT at baseline and approximately 6 weeks after ART initiation (short-term). Twenty-seven PWH participants underwent follow-up scans 2 years after treatment (long-term). FDG PET/CT scans from 20 healthy controls were used for comparison. Liver FDG uptake was quantified from the PET/CT scans. Imaging findings as well as clinical, laboratory, and immune markers were compared longitudinally and cross-sectionally to healthy controls.

RESULTS

Liver FDG uptake was lower at baseline and short-term in PWH compared with controls ( P  < 0.0001). At the long-term scan, liver FDG uptake of PWH increased relative to baseline and short-term ( P  = 0.0083 and 0.0052) but remained lower than controls' values ( P  = 0.004). Changes in FDG uptake correlated negatively with levels of glucagon, myeloperoxidase, sCD14, and MCP-1 and positively with markers of recovery (BMI, albumin, and CD4 + cell counts) ( P  < 0.01). In multivariable analyses of PWH values across timepoints, BMI and glucagon were the best set of predictors for liver FDG uptake ( P  < 0.0001).

CONCLUSION

Using FDG PET/CT, we found decreased liver glucose metabolism in PWH that could reflect hepatocytes/lymphocytes/myeloid cell loss and metabolic dysfunction because of inflammation. Although long-term ART seems to reverse many hepatic abnormalities, residual liver injury may still exist within 2 years of treatment initiation, especially in PWH who present with low nadir CD4 + cell counts.

Type I interferons and TGF-β cooperate to induce liver fibrosis during HIV-1 infection under antiretroviral therapy

Liver diseases have become a major comorbidity health concern for people living with HIV-1 (PLWH) treated with combination antiretroviral therapy (cART). To investigate if HIV-1 infection and cART interact to lead to liver diseases, humanized mice reconstituted with progenitor cells from human fetal livers were infected with HIV-1 and treated with cART. We report here that chronic HIV-1 infection with cART induced hepatitis and liver fibrosis in humanized mice, associated with accumulation of M2-like macrophages (M2LMs), elevated TGF-β, and IFN signaling in the liver. Interestingly, IFN-I and TGF-β cooperatively activated human hepatic stellate cells (HepSCs) in vitro. Mechanistically, IFN-I enhanced TGF-β–induced SMAD2/3 activation in HepSCs. Finally, blockade of IFN-I signaling reversed HIV/cART-induced liver diseases in humanized mice. Consistent with the findings in humanized mice with HIV-1 and cART, we detected elevated markers of liver injury, M2LMs, and of IFN signaling in blood specimens from PLWH compared with those of healthy individuals. These findings identify the IFN-I/M2LM/HepSC axis in HIV/cART-induced liver diseases and suggest that inhibiting IFN-I signaling or M2LM may provide a novel therapeutic strategy for treating HIV/cART-associated liver diseases in PLWH treated with antiretroviral therapy.

HIV-1 cell-to-cell spread overcomes the virus entry block of non-macrophage-tropic strains in macrophages

Macrophages (MΦ) are increasingly recognized as HIV-1 target cells involved in the pathogenesis and persistence of infection. Paradoxically, in vitro infection assays suggest that virus isolates are mostly T-cell-tropic and rarely MΦ-tropic. The latter are assumed to emerge under CD4+ T-cell paucity in tissues such as the brain or at late stage when the CD4 T-cell count declines. However, assays to qualify HIV-1 tropism use cell-free viral particles and may not fully reflect the conditions of in vivo MΦ infection through cell-to-cell viral transfer. Here, we investigated the capacity of viruses expressing primary envelope glycoproteins (Envs) with CCR5 and/or CXCR4 usage from different stages of infection, including transmitted/founder Envs, to infect MΦ by a cell-free mode and through cell-to-cell transfer from infected CD4+ T cells. The results show that most viruses were unable to enter MΦ as cell-free particles, in agreement with the current view that non-M-tropic viruses inefficiently use CD4 and/or CCR5 or CXCR4 entry receptors on MΦ. In contrast, all viruses could be effectively cell-to-cell transferred to MΦ from infected CD4+ T cells. We further showed that viral transfer proceeded through Env-dependent cell-cell fusion of infected T cells with MΦ targets, leading to the formation of productively infected multinucleated giant cells. Compared to cell-free infection, infected T-cell/MΦ contacts showed enhanced interactions of R5 M- and non-M-tropic Envs with CD4 and CCR5, resulting in a reduced dependence on receptor expression levels on MΦ for viral entry. Altogether, our results show that virus cell-to-cell transfer overcomes the entry block of isolates initially defined as non-macrophage-tropic, indicating that HIV-1 has a more prevalent tropism for MΦ than initially suggested. This sheds light into the role of this route of virus cell-to-cell transfer to MΦ in CD4+ T cell rich tissues for HIV-1 transmission, dissemination and formation of tissue viral reservoirs.

Microbiota-Meditated Immunity Abnormalities Facilitate Hepatitis B Virus Co-Infection in People Living With HIV: A Review

Hepatitis B virus (HBV) co-infection is fairly common in people living with HIV (PLWH) and affects millions of people worldwide. Identical transmission routes and HIV-induced immune suppression have been assumed to be the main factors contributing to this phenomenon. Moreover, convergent evidence has shown that people co-infected with HIV and HBV are more likely to have long-term serious medical problems, suffer more from liver-related diseases, and have higher mortality rates, compared to individuals infected exclusively by either HIV or HBV. However, the precise mechanisms underlying the comorbid infection of HIV and HBV have not been fully elucidated. In recent times, the human gastrointestinal microbiome is progressively being recognized as playing a pivotal role in modulating immune function, and is likely to also contribute significantly to critical processes involving systemic inflammation. Both antiretroviral therapy (ART)-naïve HIV-infected subjects and ART-treated individuals are now known to be characterized by having gut microbiomic dysbiosis, which is associated with a damaged intestinal barrier, impaired mucosal immunological functioning, increased microbial translocation, and long-term immune activation. Altered microbiota-related products in PLWH, such as lipopolysaccharide (LPS) and short-chain fatty acids (SCFA), have been associated with the development of leaky gut syndrome, favoring microbial translocation, which in turn has been associated with a chronically activated underlying host immune response and hence the facilitated pathogenesis of HBV infection. Herein, we critically review the interplay among gut microbiota, immunity, and HIV and HBV infection, thus laying down the groundwork with respect to the future development of effective strategies to efficiently restore normally diversified gut microbiota in PLWH with a dysregulated gut microbiome, and thus potentially reduce the prevalence of HBV infection in this population.

Non-Alcoholic Fatty Liver Disease in HIV/HBV Patients - a Metabolic Imbalance Aggravated by Antiretroviral Therapy and Perpetuated by the Hepatokine/Adipokine Axis Breakdown

Non-alcoholic fatty liver disease (NAFLD) is strongly associated with the metabolic syndrome and is one of the most prevalent comorbidities in HIV and HBV infected patients. HIV plays an early and direct role in the development of metabolic syndrome by disrupting the mechanism of adipogenesis and synthesis of adipokines. Adipokines, molecules that regulate the lipid metabolism, also contribute to the progression of NAFLD either directly or via hepatic organokines (hepatokines). Most hepatokines play a direct role in lipid homeostasis and liver inflammation but their role in the evolution of NAFLD is not well defined. The role of HBV in the pathogenesis of NAFLD is controversial. HBV has been previously associated with a decreased level of triglycerides and with a protective role against the development of steatosis and metabolic syndrome. At the same time HBV displays a high fibrogenetic and oncogenetic potential. In the HIV/HBV co-infection, the metabolic changes are initiated by mitochondrial dysfunction as well as by the fatty overload of the liver, two interconnected mechanisms. The evolution of NAFLD is further perpetuated by the inflammatory response to these viral agents and by the variable toxicity of the antiretroviral therapy. The current article discusses the pathogenic changes and the contribution of the hepatokine/adipokine axis in the development of NAFLD as well as the implications of HIV and HBV infection in the breakdown of the hepatokine/adipokine axis and NAFLD progression.

A Tale of Two Viruses: Immunological Insights Into HCV/HIV Coinfection

Nearly 2.3 million individuals worldwide are coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Odds of HCV infection are six times higher in people living with HIV (PLWH) compared to their HIV-negative counterparts, with the highest prevalence among people who inject drugs (PWID) and men who have sex with men (MSM). HIV coinfection has a detrimental impact on the natural history of HCV, including higher rates of HCV persistence following acute infection, higher viral loads, and accelerated progression of liver fibrosis and development of end-stage liver disease compared to HCV monoinfection. Similarly, it has been reported that HCV coinfection impacts HIV disease progression in PLWH receiving anti-retroviral therapies (ART) where HCV coinfection negatively affects the homeostasis of CD4⁺ T cell counts and facilitates HIV replication and viral reservoir persistence. While ART does not cure HIV, direct acting antivirals (DAA) can now achieve HCV cure in nearly 95% of coinfected individuals. However, little is known about how HCV cure and the subsequent resolution of liver inflammation influence systemic immune activation, immune reconstitution and the latent HIV reservoir. In this review, we will summarize the current knowledge regarding the pathogenesis of HIV/HCV coinfection, the effects of HCV coinfection on HIV disease progression in the context of ART, the impact of HIV on HCV-associated liver morbidity, and the consequences of DAA-mediated HCV cure on immune reconstitution and HIV reservoir persistence in coinfected patients.

Infections at the nexus of metabolic-associated fatty liver disease

Metabolic-associated fatty liver disease (MAFLD) is a chronic liver disease that affects about a quarter of the world population. MAFLD encompasses different disease stadia ranging from isolated liver steatosis to non-alcoholic steatohepatitis (NASH), fibrosis, cirrhosis and hepatocellular carcinoma. Although MAFLD is considered as the hepatic manifestation of the metabolic syndrome, multiple concomitant disease-potentiating factors can accelerate disease progression. Among these risk factors are diet, lifestyle, genetic traits, intake of steatogenic drugs, male gender and particular infections. Although infections often outweigh the development of fatty liver disease, pre-existing MAFLD could be triggered to progress towards more severe disease stadia. These combined disease cases might be underreported because of the high prevalence of both MAFLD and infectious diseases that can promote or exacerbate fatty liver disease development. In this review, we portray the molecular and cellular mechanisms by which the most relevant viral, bacterial and parasitic infections influence the progression of fatty liver disease and steatohepatitis. We focus in particular on how infectious diseases, including coronavirus disease-19, hepatitis C, acquired immunodeficiency syndrome, peptic ulcer and periodontitis, exacerbate MAFLD. We specifically underscore the synergistic effects of these infections with other MAFLD-promoting factors.

Interactions with Commensal and Pathogenic Bacteria Induce HIV-1 Latency in Macrophages through Altered Transcription Factor Recruitment to the LTR

Macrophages are infected by HIV-1 in vivo and contribute to both viral spread and pathogenesis. Recent human and animal studies suggest that HIV-1-infected macrophages serve as a reservoir that contributes to HIV-1 persistence during anti-retroviral therapy. The ability of macrophages to serve as persistent viral reservoirs is likely influenced by the local tissue microenvironment, including interactions with pathogenic and commensal microbes. Here we show that the sexually transmitted pathogen Neisseria gonorrhoeae (GC) and the gut-associated microbe Escherichia coli (E. coli), which encode ligands for both Toll-like receptor 2 (TLR2) and TLR4, repressed HIV-1 replication in macrophages and thereby induced a state reminiscent of viral latency. This repression was mediated by signaling through TLR4 and the adaptor protein TRIF and was associated with increased production of type I interferons. Inhibiting TLR4 signaling, blocking type 1 interferon, or knocking-down TRIF reversed LPS- and GC-mediated repression of HIV-1. Finally, the repression of HIV-1 in macrophages was associated with the recruitment of interferon regulatory factor 8 (IRF8) to the interferon stimulated response element (ISRE) downstream of the 5' HIV-1 long terminal repeat (LTR). Our data indicate that IRF8 is responsible for repression of HIV-1 replication in macrophages in response to TRIF-dependent signaling during GC and E. coli co-infection. These findings highlight the potential role of macrophages as HIV-1 reservoirs as well as the role of the tissue microenvironment and co-infections as modulators of HIV-1 persistence.IMPORTANCE The major barrier toward the eradication of HIV-1 infection is the presence of a small reservoir of latently infected cells, which include CD4+ T cells and macrophages that escape immune-mediated clearance and the effects of anti-retroviral therapy. There remain crucial gaps in our understanding of the molecular mechanisms that lead to transcriptionally silent or latent HIV-1 infection of macrophages. The significance of our research is in identifying microenvironmental factors, such as commensal and pathogenic microbes, that can contribute to the establishment and maintenance of latent HIV-1 infection in macrophages. It is hoped that identifying key processes contributing to HIV-1 persistence in macrophages may ultimately lead to novel therapeutics to eliminate latent HIV-1 reservoirs in vivo.

Altered expression of fractalkine in HIV-1-infected astrocytes and consequences for the virus-related neurotoxicity

HIV-1 infection in the central nervous system (CNS) causes the release of neurotoxic products from infected cells which trigger extensive neuronal loss. Clinically, this results in HIV-1-associated neurocognitive disorders (HAND). However, the effects on neuroprotective factors in the brain remain poorly understood and understudied in this situation. HAND is a multifactorial process involving several players, and the complex cellular mechanisms have not been fully elucidated yet. In this study, we reported that HIV-1 infection of astrocytes limits their potential to express the protective chemokine fractalkine in response to an inflammatory environment. We next confirmed that this effect was not due to a default in its shedding from the cell surface. We then investigated the biological mechanism responsible for this reduced fractalkine expression and found that HIV-1 infection specifically blocks the interaction of transcription factor NF-κB on its promoter with no effect on other cytokines. Moreover, we demonstrated that fractalkine production in astrocytes is regulated in response to immune factors secreted by infected/activated microglia and macrophages. In contrast, we observed that conditioned media from these infected cells also trigger neuronal apoptosis. At last, we demonstrated a strong neuroprotective action of fractalkine on human neurons by reducing neuronal damages. Taken together, our results indicate new relevant interactions between HIV-1 and fractalkine signaling in the CNS. This study provides new information to broaden the understanding of HAND and possibly foresee new therapeutic strategies. Considering its neuro-protective functions, reducing its production from astrocytes could have important outcomes in chronic neuroinflammation and in HIV-1 neuropathogenesis.

Oncogenic Effects of HIV-1 Proteins, Mechanisms Behind

People living with human immunodeficiency virus (HIV-1) are at increased risk of developing cancer, such as Kaposi sarcoma (KS), non-Hodgkin lymphoma (NHL), cervical cancer, and other cancers associated with chronic viral infections. Traditionally, this is linked to HIV-1-induced immune suppression with depletion of CD4+ T-helper cells, exhaustion of lymphopoiesis and lymphocyte dysfunction. However, the long-term successful implementation of antiretroviral therapy (ART) with an early start did not preclude the oncological complications, implying that HIV-1 and its antigens are directly involved in carcinogenesis and may exert their effects on the background of restored immune system even when present at extremely low levels. Experimental data indicate that HIV-1 virions and single viral antigens can enter a wide variety of cells, including epithelial. This review is focused on the effects of five viral proteins: envelope protein gp120, accessory protein negative factor Nef, matrix protein p17, transactivator of transcription Tat and reverse transcriptase RT. Gp120, Nef, p17, Tat, and RT cause oxidative stress, can be released from HIV-1-infected cells and are oncogenic. All five are in a position to affect "innocent" bystander cells, specifically, to cause the propagation of (pre)existing malignant and malignant transformation of normal epithelial cells, giving grounds to the direct carcinogenic effects of HIV-1.

Insights Into the Pathophysiology of Liver Disease in HCV/HIV: Does it End With HCV Cure?

HCV-HIV coinfected patients exhibit rapid progression of liver damage relative to HCV monoinfected patients. The availability of new directly acting antiviral agents has dramatically improved outcomes for coinfected patients as sustained virologic response rates now exceed 95% and fibrosis-related parameters are improved. Nevertheless, coinfected patients still have a higher mortality risk and more severe hepatocellular carcinoma compared to HCV monoinfected patients, implying the existence of pathways unique to people living with HIV that continue to promote accelerated liver disease. In this article, we review the pathobiology of liver disease in HCV-HIV coinfected patients in the directly acting antiviral era and explore the mechanisms through which HIV itself induces liver damage. Since liver disease is one of the leading causes of non-AIDS-related mortality in HIV-positive patients, enhancing our understanding of HIV-associated fibrotic pathways will remain important for new diagnostic and therapeutic strategies to slow or reverse liver disease progression, even after HCV cure.

HIV-1 Persistence and Chronic Induction of Innate Immune Responses in Macrophages

A hallmark of HIV-1 infection is chronic inflammation, which plays a significant role in disease pathogenesis. Acute HIV infection induces robust inflammatory responses, which are insufficient to prevent or eliminate virus in mucosal tissues. While establishment of viral set-point is coincident with downregulation of acute innate responses, systemic inflammatory responses persist during the course of chronic HIV infection. Since the introduction of combination antiviral therapy (cART), most HIV-1⁺ individuals can suppress viremia under detection levels for decades. However, chronic immune activation persists and has been postulated to cause HIV associated non-AIDS complications (HANA). Importantly, inflammatory cytokines and activation markers associated with macrophages are strongly and selectively correlated with the incidence of HIV-associated neurocognitive disorder (HAND), cardiovascular dysfunctions (CVD) and other HANA conditions. In this review, we discuss the roles of macrophages in facilitating viral persistence and contributing to generation of persistent inflammatory responses.

Role of Kupffer Cells in Driving Hepatic Inflammation and Fibrosis in HIV Infection

While the interactions between HIV and various liver cell populations have been explored, the relevance of these interactions when patients are well-controlled on ART is less clear. Therefore, we focus this perspective on HIV-related alterations that may drive hepatic inflammation and fibrosis in aviremic patients, with a focus on Kupffer cells and Hepatic Stellate Cells. Persistent CD4+ T cell depletion in the gut resulting in increased gut permeability has been postulated to play a role in systemic immune activation in HIV patients. The liver, with its unique location, remains the gatekeeper between the gut and the systemic circulation. The resident liver macrophage, Kupffer cell, is responsible for clearing and responding to these products. We propose that changes in Kupffer cell biology, in the context of HIV infection, creates a mileu that drives hepatic inflammation and fibrosis in response to microbial translocation. Targeting these pathways may be helpful in improving liver-related outcomes in HIV patients.

A minor population of macrophage-tropic HIV-1 variants is identified in recrudescing viremia following analytic treatment interruption

HIV-1 persists in cellular reservoirs that can reignite viremia if antiretroviral therapy (ART) is interrupted. Therefore, insight into the nature of those reservoirs may be revealed from the composition of recrudescing viremia following treatment cessation. A minor population of macrophage-tropic (M-tropic) viruses was identified in a library of recombinant viruses constructed with individual envelope genes that were obtained from plasma of six individuals undergoing analytic treatment interruption (ATI). M-tropic viruses could also be enriched from post-ATI plasma using macrophage-specific (CD14) but not CD4+ T cell-specific (CD3) antibodies, suggesting that M-tropic viruses had a macrophage origin. Molecular clock analysis indicated that the establishment of M-tropic HIV-1 variants predated ATI. Collectively, these data suggest that macrophages are a viral reservoir in HIV-1-infected individuals on effective ART and that M-tropic variants can appear in rebounding viremia when treatment is interrupted. These findings have implications for the design of curative strategies for HIV-1.

Up-regulation of miR-155 contributes to TNF-mediated hepatocyte apoptosis in acute liver failure

BACKGROUND/AIMS

Acute liver failure (ALF) is due to severe immune response, resulting in massive apoptosis/necrosis of hepatocytes. The precise mechanism has not been explored yet.

MATERIALS AND METHODS

The mouse with ALF model was induced by D-GalN/LPS; the hepatic miRNAs expression profile was evaluated by miRNA microarray and verified by RT-PCR. During the ALF in mice, the miR-155 expression was detected in the liver as well as in spleen. Then the correlation between miR-155 and inflammatory cytokines was evaluated. Furthermore, the miR-155 expression in activated Raw264.7 cells and apoptotic hepatocytes was also studied. Finally, the regulatory roles of miR-155 in TNF expression of apoptotic hepatocytes were shown.

RESULTS

It was shown that miRNAs changed in the mice with ALF relating to hepatocytes apoptosis/necrosis; the selected miRNAs were confirmed with RT-PCR. miR-155 was up-regulated, but miR-698, -720, and -329 were down-regulated. Moreover, hepatic miR-155 was up-regulated at all-time points in the liver, but only at 7 h in spleen of mice with ALF. A significant correlation was observed between hepatic miR-155 and TNF/IL-6 in mice with ALF, which was supported by the findings in vitro showing up-regulated miR-155 in Raw264.7 cells and Hepa1-6 cells under LPS or D-GalN+TNF induction, respectively. Moreover, a correlation was observed between miR155 and TNF levels in vivo and in vitro.

CONCLUSION

These data demonstrate that miR-155 regulates TNF-mediated hepatocyte apoptosis in ALF, which provides some useful information in both basic and clinical researches.

The Role of Macrophages in HIV-1 Persistence and Pathogenesis

Current antiretroviral therapy (ART) effectively suppresses Human Immunodeficiency Virus type 1 (HIV-1) in infected individuals. However, even long term ART does not eradicate HIV-1 infected cells and the virus persists in cellular reservoirs. Beside memory CD4⁺ T cells, cells of the myeloid lineage, especially macrophages, are believed to be an important sanctuary for HIV-1. Monocytes and macrophages are key players in the innate immune response to pathogens and are recruited to sites of infection and inflammation. Due to their long life span and ability to reside in virtually every tissue, macrophages have been proposed to play a critical role in the establishment and persistence of the HIV-1 reservoir. Current HIV-1 cure strategies mainly focus on the concept of “shock and kill” to purge the viral reservoir. This approach aims to reactivate viral protein production in latently infected cells, which subsequently are eliminated as a consequence of viral replication, or recognized and killed by the immune system. Macrophage susceptibility to HIV-1 infection is dependent on the local microenvironment, suggesting that molecular pathways directing differentiation and polarization are involved. Current latency reversing agents (LRA) are mainly designed to reactivate the HIV-1 provirus in CD4+ T cells, while their ability to abolish viral latency in macrophages is largely unknown. Moreover, the resistance of macrophages to HIV-1 mediated kill and the presence of infected macrophages in immune privileged regions including the central nervous system (CNS), may pose a barrier to elimination of infected cells by current “shock and kill” strategies. This review focusses on the role of monocytes/macrophages in HIV-1 persistence. We will discuss mechanisms of viral latency and persistence in monocytes/macrophages. Furthermore, the role of these cells in HIV-1 tissue distribution and pathogenesis will be discussed.

Individual liver plasmacytoid dendritic cells are capable of producing IFNα and multiple additional cytokines during chronic HCV infection

Plasmacytoid dendritic cells (pDCs) are "natural" interferon α (IFNα)-producing cells. Despite their importance to antiviral defense, autoimmunity, and ischemic liver graft injury, because DC subsets are rare and heterogeneous, basic questions about liver pDC function and capacity to make cytokines remain unanswered. Previous investigations failed to consistently detect IFNα mRNA in HCV-infected livers, suggesting that pDCs may be incapable of producing IFNα. We used a combination of molecular, biochemical, cytometric, and high-dimensional techniques to analyze DC frequencies/functions in liver and peripheral blood mononuclear cells (PBMCs) of hepatitis C virus (HCV)-infected patients, to examine correlations between DC function and gene expression of matched whole liver tissue and liver mononuclear cells (LMCs), and to determine if pDCs can produce multiple cytokines. T cells often produce multiple cytokines/chemokines but until recently technical limitations have precluded tests of polyfunctionality in individual pDCs. Mass cytometry (CyTOF) revealed that liver pDCs are the only LMC that produces detectable amounts of IFNα in response TLR-7/8 stimulation. Liver pDCs secreted large quantities of IFNα (~2 million molecules of IFNα/cell/hour) and produced more IFNα than PBMCs after stimulation, p = 0.0001. LMCs secreted >14-fold more IFNα than IFNλ in 4 hours. Liver pDC frequency positively correlated with whole liver expression of "IFNα-response" pathway (R2 = 0.58, p = 0.007) and "monocyte surface" signature (R2 = 0.54, p = 0.01). Mass cytometry revealed that IFNα-producing pDCs were highly polyfunctional; >90% also made 2-4 additional cytokines/chemokines of our test set of 10. Liver BDCA1 DCs, but not BDCA3 DCs, were similarly polyfunctional. pDCs from a healthy liver were also polyfunctional. Our data show that liver pDCs retain the ability to make abundant IFNα during chronic HCV infection and produce many other immune modulators. Polyfunctional liver pDCs are likely to be key drivers of inflammation and immune activation during chronic HCV infection.

HIV and HCV augments inflammatory responses through increased TREM-1 expression and signaling in Kupffer and Myeloid cells

Chronic infection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) affects an estimated 35 million and 75 million individuals worldwide, respectively. These viruses induce persistent inflammation which often drives the development or progression of organ-specific diseases and even cancer including Hepatocellular Carcinoma (HCC). In this study, we sought to examine inflammatory responses following HIV or HCV stimulation of macrophages or Kupffer cells (KCs), that may contribute to virus mediated inflammation and subsequent liver disease. KCs are liver-resident macrophages and reports have provided evidence that HIV can stimulate and infect them. In order to characterize HIV-intrinsic innate immune responses that may occur in the liver, we performed microarray analyses on KCs following HIV stimulation. Our data demonstrate that KCs upregulate several innate immune signaling pathways involved in inflammation, myeloid cell maturation, stellate cell activation, and Triggering Receptor Expressed on Myeloid cells 1 (TREM1) signaling. TREM1 is a member of the immunoglobulin superfamily of receptors and it is reported to be involved in systemic inflammatory responses due to its ability to amplify activation of host defense signaling pathways. Our data demonstrate that stimulation of KCs with HIV or HCV induces the upregulation of TREM1. Additionally, HIV viral proteins can upregulate expression of TREM1 mRNA through NF-кB signaling. Furthermore, activation of the TREM1 signaling pathway, with a targeted agonist, increased HIV or HCV-mediated inflammatory responses in macrophages due to enhanced activation of the ERK1/2 signaling cascade. Silencing TREM1 dampened inflammatory immune responses elicited by HIV or HCV stimulation. Finally, HIV and HCV infected patients exhibit higher expression and frequency of TREM1 and CD68 positive cells. Taken together, TREM1 induction by HIV contributes to chronic inflammation in the liver and targeting TREM1 signaling may be a therapeutic option to minimize HIV induced chronic inflammation.

Although HIV antiviral therapy has limited the progression to AIDS in infected patients, there is still significant morbidity and mortality from HIV-driven diseases due to sustained inflammation. In this study, we sought to elucidate how HIV and HCV could impact inflammation in the liver and cause progressive liver disease that can eventually lead to cirrhosis and liver cancer. We found that HIV upregulates the inflammatory response amplifier, TREM1, in primary Kupffer Cells (KCs) that are liver-resident macrophages. Enhanced TREM1 expression subsequently is involved in augmented immune responses triggered by HIV or HCV. Additionally, our data demonstrates that blocking TREM1 expression reduces inflammatory responses mediated by HIV or HCV stimulation. Ultimately, our understanding of this mechanism may yield additional therapeutic strategies to help infected patients and give insight into inflammation driven liver cancer.

HIV infection modulates IL-1β response to LPS stimulation through a TLR4-NLRP3 pathway in human liver macrophages

IL-1β is an important mediator of innate inflammatory responses and has been shown to contribute to liver injury in a number of etiologies. HIV patients have increased necroinflammation and more rapid fibrosis progression in chronic liver injury compared to non-HIV-infected patients. As the resident liver macrophage is critical to the IL-1β response to microbial translocation in chronic liver disease, we aim to examine the impact of HIV-1 and LPS stimulation on the IL-1β response of the resident hepatic macrophages. We isolated primary human liver macrophages from liver resection specimens, treated them with HIV-1_BaL and/or LPS ex vivo, examined the IL-1β response, and then studied underlying mechanisms. Furthermore, we examined IL-1β expression in liver tissues derived from HIV-1 patients compared to those with no underlying liver disease. HIV-1 up-regulated TLR4 and CD14 expression on isolated primary CD68+ human liver macrophages and contributed to the IL-1β response to LPS stimulation as evidenced by TLR4 blocking. Nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) was shown to be involved in the IL-1β response of liver macrophages to HIV-1 infection and NLRP3 blocking experiments in primary CD68+ liver macrophages confirmed the contribution of the NLRP3-caspase 1 inflammatory signaling pathway in the IL-1β response. High in situ IL-1β expression was found in CD68⁺ cells in human liver tissues from HIV-1-infected patients, suggesting a critical role of IL-1β responses in patients infected by HIV. HIV infection sensitizes the IL-1β response of liver macrophages to LPS through up-regulation of CD14 and TLR4 expression and downstream activation of the NLRP3-caspase 1 pathway. These findings have implications for enhanced immune activation in HIV⁺ patients and mechanisms for rapid fibrosis progression in patients with chronic liver injury.

Human immunodeficiency virus and hepatotropic viruses co-morbidities as the inducers of liver injury progression

Hepatotropic viruses induced hepatitis progresses much faster and causes more liver- related health problems in people co-infected with human immunodeficiency virus (HIV). Although treatment with antiretroviral therapy has extended the life expectancy of people with HIV, liver disease induced by hepatitis B virus (HBV) and hepatitis C virus (HCV) causes significant numbers of non-acquired immune deficiency syndrome (AIDS)-related deaths in co-infected patients. In recent years, new insights into the mechanisms of accelerated fibrosis and liver disease progression in HIV/HCV and HIV/HBV co-infections have been reported. In this paper, we review recent studies examining the natural history and pathogenesis of liver disease in HIV-HCV/HBV co-infection in the era of direct acting antivirals (DAA) and antiretroviral therapy (ART). We also review the novel therapeutics for management of HIV/HCV and HIV/HBV co-infected individuals.

The Role of Macrophages in HIV-1 Persistence and Pathogenesis

Current antiretroviral therapy (ART) effectively suppresses Human Immunodeficiency Virus type 1 (HIV-1) in infected individuals. However, even long term ART does not eradicate HIV-1 infected cells and the virus persists in cellular reservoirs. Beside memory CD4⁺ T cells, cells of the myeloid lineage, especially macrophages, are believed to be an important sanctuary for HIV-1. Monocytes and macrophages are key players in the innate immune response to pathogens and are recruited to sites of infection and inflammation. Due to their long life span and ability to reside in virtually every tissue, macrophages have been proposed to play a critical role in the establishment and persistence of the HIV-1 reservoir. Current HIV-1 cure strategies mainly focus on the concept of "shock and kill" to purge the viral reservoir. This approach aims to reactivate viral protein production in latently infected cells, which subsequently are eliminated as a consequence of viral replication, or recognized and killed by the immune system. Macrophage susceptibility to HIV-1 infection is dependent on the local microenvironment, suggesting that molecular pathways directing differentiation and polarization are involved. Current latency reversing agents (LRA) are mainly designed to reactivate the HIV-1 provirus in CD4+ T cells, while their ability to abolish viral latency in macrophages is largely unknown. Moreover, the resistance of macrophages to HIV-1 mediated kill and the presence of infected macrophages in immune privileged regions including the central nervous system (CNS), may pose a barrier to elimination of infected cells by current "shock and kill" strategies. This review focusses on the role of monocytes/macrophages in HIV-1 persistence. We will discuss mechanisms of viral latency and persistence in monocytes/macrophages. Furthermore, the role of these cells in HIV-1 tissue distribution and pathogenesis will be discussed.

HIV and the liver

Work during the past two decades has highlighted how HIV contributes to hepatic inflammation and fibrosis, leading to changes in the timing of antiretroviral therapy initiation and to improved diagnosis and management of liver disease in patients with HIV. As this population ages, clinician vigilance with early detection of emerging liver disease will be critical.

Host and Viral Factors Influencing Interplay between the Macrophage and HIV-1

HIV-1 persists in cellular reservoirs that cannot be eliminated by antiretroviral therapy (ART). The major reservoir in infected individuals on effective ART is composed of resting memory CD4+ T cells that harbor proviral cDNA, and undergo a state of latency in which viral gene expression is minimal to absent. The CD4+ T cell reservoir has been extensively characterized. However, other HIV-1-permissive cells may contribute to HIV-1 persistence. Lentiviruses have a long recognized association with macrophages. However, the role, if any, played by macrophages in HIV-1 persistence is not well understood. Macrophages are resistant to cell death upon HIV-1 infection, and can survive for long periods of time, making them ideal host cells in which the virus might persist. Studying macrophages is challenging, as these cells reside in nearly all tissues. Moreover, detecting viral DNA or RNA in macrophages does not necessarily indicate that these cells will produce replication-competent viral particles. Currently, the gold standard assay to detect cellular reservoirs is the ex vivo quantitative viral outgrowth assay (QVOA), which requires a patient blood draw. However, macrophages reside deep within tissues that are inaccessible in living subjects, such as the central nervous system (CNS). Therefore, tools other than QVOA must be developed to identify cellular reservoirs that reside in the tissues. In this review, we will focus on the main aspects involved in HIV-1 persistence, including the molecular mechanisms of viral evasion, the main cell types responsible for harboring persistent HIV-1 and the tissue compartments that are likely to be reservoirs for HIV-1.

HIV and the Macrophage: From Cell Reservoirs to Drug Delivery to Viral Eradication

Macrophages serve as host cells, inflammatory disease drivers and drug runners for human immunodeficiency virus infection and treatments. Low-level viral persistence continues in these cells in the absence of macrophage death. However, the cellular microenvironment changes as a consequence of viral infection with aberrant production of pro-inflammatory factors and promotion of oxidative stress. These herald viral spread from macrophages to neighboring CD4⁺ T cells and end organ damage. Virus replicates in tissue reservoir sites that include the nervous, pulmonary, cardiovascular, gut, and renal organs. However, each of these events are held in check by antiretroviral therapy. A hidden and often overlooked resource of the macrophage rests in its high cytoplasmic nuclear ratios that allow the cell to sense its environment and rid it of the cellular waste products and microbial pathogens it encounters. These phagocytic and intracellular killing sensing mechanisms can also be used in service as macrophages serve as cellular carriage depots for antiretroviral nanoparticles and are able to deliver medicines to infectious disease sites with improved therapeutic outcomes. These undiscovered cellular functions can lead to reductions in persistent infection and may potentially facilitate the eradication of residual virus to eliminate disease.

Plasma levels of lipopolysaccharide correlate with insulin resistance in HIV patients

BACKGROUND

In HIV patients using HAART insulin resistance is a central pathophysiological condition that can contribute to the development of diabetes and cardiovascular complications. To examine the role of adipocyte hormones and LPS in insulin resistance in HIV patients, we investigated the role of adiponectin, leptin, visfatin and LPS levels in the insulin resistance of HIV-infected patients treated with HAART.

METHODS

This study included 67 HIV positive individuals on HAART and ten healthy controls. All participants performed plasma or serum levels of glucose; insulin; lipids, visfatin, leptin, adiponectin, and LPS. The homeostasis model assessment (HOMA-IR), was used to estimate insulin resistance.

RESULTS

The levels of visfatin, leptin and adiponectin were similar between controls and HIV patients. However, circulating levels of LPS were higher in HIV patients on HAART than in controls. There was a positive correlation between LPS and TG (r = 0.49, p = 0.0001), between LPS and TG/HDL (r = 0.50, p = 0.0001), between LPS and insulin (r = 0.52, p = 0.0003), and between LPS and HOMA-IR (r = 0.52, p = 0.0005), in HIV patients.

CONCLUSIONS

Our results showed a clear correlation between plasma LPS and markers of insulin resistance, suggesting a relationship between LPS levels and metabolic alterations, particularly affecting lipids and insulin resistance in HIV patients.

Hepatitis C Virus, Inflammation, and Cellular Aging: Turning Back Time

There is evidence that hepatitis C virus (HCV) infection, like HIV infection, may be associated with chronic inflammation, immune activation, and immune senescence, which contribute to increased risks for cardiometabolic or other diseases outside the liver, as well as to ongoing damage in the liver. These effects may persist after a sustained virologic response (SVR) is achieved with HCV therapy. Such findings support initiation of treatment for HCV-infected individuals before damage to the liver is apparent and monitoring of individuals for complications even after an SVR is achieved. Fibrosis is not always reversible after SVR is achieved, and this should serve as an argument against waiting until fibrosis develops before initiating treatment for HCV-infected individuals. This article summarizes a presentation by Susanna Naggie, MD, MHS, at the IAS-USA continuing education program, Management of Hepatitis C Virus in the New Era: Small Molecules Bring Big Changes, in New York, New York, in September 2015.