Alterations of the NK cell pool in HIV/HCV co-infection

Unraveling the non-fitness status of NK cells: Examining the NKp30 receptor and its isoforms distribution in HIV/HCV coinfected patients

BACKGROUND

HIV/HCV coinfection is associated with a rapid progression to liver damage. Specifically, NK cell population dysregulation is of particular interest, as these cells have been shown to block HCV replication effectively and have an anti-fibrogenic activity. The NKp30 receptor is linked to tumor cell lysis and has a crucial role during viral infections. In the present study, we determined the subpopulations of NK cells based on CD56 and CD16 expression, NKp30 receptor expression, its isoforms A, B, and C, along with the cytotoxicity molecules in patients with HIV/HCV.

RESULTS

evidenced by the APRI and FIB-4 indices, the HCV-infected patients presented greater liver damage than the HIV and HIV/HCV groups. The HCV group presented a decreased expression of NKp30 isoform A, and NK cell frequency was not different between groups; however, CD56brigth subpopulation, NKp30 receptor, and CD247 adaptor chain were decreased in HIV/HCV patients; further, we described increased levels of soluble IL-8, IL-10, IL-12, and IL-23 in the serum of HIV/HCV patients.

CONCLUSIONS

HCV and HIV/HCV patients have multiple parameters of non-fitness status in NK cells; awareness of these dysfunctional immunological parameters in HIV/HCV and HCV patients can elucidate possible novel therapeutics directed towards the improvement of NK cell fitness status, in order to improve their function against liver damage.

Markers of Natural Killer Cell Exhaustion in HIV/HCV Coinfection and Their Dynamics After HCV Clearance Mediated by Direct-Acting Antivirals

Background

Liver fibrosis is a leading cause of morbimortality in people with HIV/hepatitis C virus (HCV). Natural killer (NK) cells are linked with amelioration of liver fibrosis; however, NK cells from individuals coinfected with HIV/HCV with cirrhosis display impaired functionality and high PD-1 expression. Here, we aimed to study PD-1, TIGIT, and Tim3 as potential exhaustion markers in NK cells from persons coinfected with HIV/HCV with mild and advanced liver fibrosis. We also evaluated the role of PD-1 expression on NK cells after HCV clearance by direct-acting antivirals (DAAs).

Methods

Peripheral blood mononuclear cells were isolated from individuals coinfected with HIV/HCV (N = 54; METAVIR F0/F1, n = 27; F4, evaluated by transient elastography, n = 27). In 26 participants, samples were collected before, at the end of, and 12 months after successful DAA treatment. The frequency, immunophenotype (PD-1, TIGIT, and Tim3 expression), and degranulation capacity (CD107a assay) of NK cells were determined by flow cytometry.

Results

Unlike PD-1, Tim3 and TIGIT were comparably expressed between persons with mild and advanced fibrosis. Degranulation capacity was diminished in NK/TIGIT+ cells in both fibrosis stages, while NK/PD-1+ cells showed a lower CD107a expression in cirrhotic cases. Twelve months after DAA treatment, those with advanced fibrosis showed an improved NK cell frequency and reduced NK/PD-1+ cell frequency but no changes in CD107a expression. In individuals with mild fibrosis, neither PD-1 nor NK cell frequency was modified, although the percentage of NK/CD107a+ cells was improved at 12 months posttreatment.

Conclusions

Although DAA improved exhaustion and frequency of NK cells in cirrhotic cases, functionality was reverted only in mild liver fibrosis, remarking the importance of an early DAA treatment.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.

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.

Antiretroviral therapy for HIV and intrahepatic hepatitis C virus replication

OBJECTIVE

HIV alters host responses to hepatitis C virus (HCV). However, the impact of antiretroviral therapy (ART) on HCV is rarely understood in relevant tissues and never before within individual hepatocytes.

DESIGN

HIV and HCV kinetics were studied before and after ART initiation among 19 HIV/HCV co-infected persons. From five persons with the largest decline in plasma HCV RNA, liver tissues collected before and during ART, when plasma HIV RNA was undetectable, were studied.

METHODS

We used single-cell laser capture microdissection and quantitative PCR to assess intrahepatic HCV. Immunohistochemistry was performed to characterize intrahepatic immune cell populations.

RESULTS

Plasma HCV RNA declined by 0.81 (0.52-1.60) log10 IU/ml from a median (range) 7.26 (6.05-7.29) log10 IU/ml and correlated with proportions of HCV-infected hepatocytes (r = 0.89, P = 2 × 10-5), which declined from median (range) of 37% (6-49%) to 23% (0.5-52%) after plasma HIV clearance. Median (range) HCV RNA abundance within cells was unchanged in four of five participants. Liver T-cell abundance unexpectedly decreased, whereas natural killer (NK) and NK T-cell infiltration increased, correlating with changes in proportions of HCV-infected hepatocytes (r = -0.82 and r = -0.73, respectively). Hepatocyte expression of HLA-E, an NK cell restriction marker, correlated with proportions of HCV-infected hepatocytes (r = 0.79).

CONCLUSION

These are the first data to show that ART control of HIV reduces the intrahepatic burden of HCV. Furthermore, our data suggest that HIV affects the pathogenesis of HCV infection by an NK/NK T-cell-mediated mechanism that may involve HLA-E and can be rescued, at least in part, by ART.

Influence of HLA-C environment on the spontaneous clearance of hepatitis C in European HIV-HCV co-infected individuals

Natural killer (NK) cell functions are regulated by diverse inhibitory and activating receptors, including killer cell immunoglobulin-like receptors (KIR), which interact with human leukocyte antigen (HLA) class I molecules. Some KIR/HLA genetic combinations were reported associated with spontaneous clearance (SC) of hepatitis C virus (HCV) but with discordant results, possibly reflecting KIR and/or HLA gene polymorphism according to populations. KIR/HLA genetic combinations associated with both an exhaustive NK and T cell repertoire were investigated in a cohort of HIV-HCV co-infected individuals with either SC (n = 68) or chronic infection (CI, n = 163) compared to uninfected blood donors [controls (Ctrl), n = 100]. Multivariate analysis showed that the HLA C2C2 environment was associated with SC only in European HIV-HCV co-infected individuals [odds ratio (OR) = 4·30, 95% confidence interval = 1·57-12·25, P = 0·005]. KIR2D⁺ NK cell repertoire and potential of degranulation of KIR2DL1/S1⁺ NK cells were similar in the SC European cohort compared to uninfected individuals. In contrast, decreased frequencies of KIR2DS1⁺ and KIR2DL2⁺ NK cells were detected in the CI group of Europeans compared to SC and a decreased frequency of KIR2DL1/S1⁺ NK cells compared to controls. Regarding T cells, higher frequencies of DNAX accessory molecule-1 (DNAM-1)⁺ and CD57⁺ T cells were observed in SC in comparison to controls. Interestingly, SC subjects emphasized increased frequencies of KIR2DL2/L3/S2⁺ T cells compared to CI subjects. Our study underlines that the C2 environment may activate efficient KIR2DL1⁺ NK cells in a viral context and maintain a KIR2DL2/L3/S2⁺ mature T cell response in the absence of KIR2DL2 engagement with its cognate ligands in SC group of HCV-HIV co-infected European patients.

The DARC-null trait is associated with moderate modulation of NK cell profiles and unaltered cytolytic T cell profiles in black South Africans

The Duffy Antigen Receptor for Chemokines (DARC)-null trait, common among persons of African descent and associated with lower absolute neutrophil counts (ANCs), may be linked to increased risk to certain infections including HIV-1 but the underlying causes are poorly understood. We hypothesized that DARC-null-linked neutropenia may negatively impact neutrophil immunoregulatory modulation of other immune cells such as natural killer (NK) and CD8+ T cells leading to altered phenotype, functionality and homeostatic activity of these immune cells. HIV-1 uninfected (n = 20) and HIV-1 chronically infected (n = 19) participants were assessed using multi-parametric flow cytometry to determine NK and CD8+ T cell counts, phenotypic profiles, and cytokine production and degranulation. Annexin V and carboxyfluorescein succinimidyl ester (CFSE) staining were used to examine NK cell survival and NK cell and CD8+ T cell proliferation respectively. Participants were genotyped for the DARC-null polymorphism using allelic discrimination assays and ANCs were measured by full blood count. In HIV uninfected individuals, a reduction of total NK cell counts was noted in the absence of DARC and this correlated with lower ANCs. HIV uninfected DARC-null subjects displayed a less mature NK cell phenotype. However, this did not translate to differences in NK cell activation or effector functionality by DARC state. Whilst HIV-1 infected subjects displayed NK cell profiling that is typical of HIV infection, no differences were noted upon DARC stratification. Similarly, CD8+ T cells from HIV infected individuals displayed phenotypic and functional modulation that is characteristic of HIV infection, but profiling was unaffected by the DARC-null variant irrespective of HIV status. Overall, the data suggests that the DARC-null polymorphism and lower ANCs does not impede downstream cytolytic cell priming and functionality.

Progressive multifocal leukoencephalopathy despite immune recovery in a HIV/HCV co-infected patient

In HIV patients, HCV co-infection has been associated with an increased risk of progressive multifocal leukoencephalopathy (PML). Furthermore, PML has also been described in patients with cirrhosis, whether related to HCV infection or not. We describe here the case of a HIV/HCV co-infected patient with cirrhosis who developed PML despite HIV suppression and CD4 cell count above 250/mm³ for 2 years. Immunological studies performed at onset of PML and before HCV therapy showed a decrease in naïve CD4 cells (CD45RA+CCR7⁺CD27⁺ CD4⁺ T cells - 23% cells, i.e. 75/mm³) and NK lymphopenia with abnormal and activated NK cells (CD3^- CD16⁺ and/or CD56⁺) (5% lymphocytes, i.e. 58/mm³, CD69 91%, NKp30 26%). This impaired immunity, possibly related to HIV infection, or HCV infection or cirrhosis, or a combination thereof, could have led to the development of PML.

Liver cirrhosis in HIV/HCV-coinfected individuals is related to NK cell dysfunction and exhaustion, but not to an impaired NK cell modulation by CD4+ T-cells

INTRODUCTION

HIV worsens HCV-related liver disease by accelerating fibrosis progression; however, progression rates are extremely variable among HIV/HCV-coinfected individuals. NK cells are associated with modulation of liver fibrosis and are profoundly altered during HCV and HIV infections. CD4+ T-cells modulate NK cell function, and are also affected by HIV infection. Here, we aim to characterize the association of hepatic fibrosis with both the phenotype and function of peripheral NK cells and their regulation by CD4+ T-cells, in HIV/HCV-coinfected individuals.

METHODS

Thirty-four HIV/HCV-coinfected individuals with minimal (n = 16) and advanced (n = 18) fibrosis (METAVIR F0/F1 and F4 scores respectively) and 20 healthy volunteers were enrolled. PBMC were obtained from peripheral blood samples and NK and CD4+ T-cells were isolated and analysed. NK cell phenotype (CD25, CD69, Nkp46, NKG2D, PD-1), degranulation (CD107a) and IFN-γ and TNF-α production, as well as CD4+ T-cell activation (CD69, CD25 and CD38) were measured by flow cytometry. CD4+ T-cell conditioned medium (CM) derived from F0/F1 or F4 individuals was assessed for IL-2 levels by ELISA. Modulation of NK cell functionality by these CMs was also analysed.

RESULTS

When comparing to NK cells from individuals with minimal fibrosis, degranulation and cytokine secretion by NK cells from subjects with F4 scores was significantly impaired, while PD-1 expression was augmented. On the one hand, neither the expression of activation markers nor IL-2 secretion was distinctly induced in CD4+ T-cells from subjects with F0/F1 or F4 METAVIR scores. Finally, NK cell degranulation and cytokine secretion were not differentially modulated by CD4+ T-cell CM, whether CD4+ T-cells derived from subjects with minimal or advanced fibrosis.

CONCLUSIONS

Low levels of NK and CD4+ T-cells in HIV/HCV-coinfected individuals with advanced liver fibrosis have been previously described. Here, we show that advanced liver fibrosis in coinfected individuals is associated to a defective function of NK cells and an increased expression of the exhaustion/senescence marker PD-1. This NK signature could not be attributed to changes in the ability of CD4+ T-cells to modulate NK cell function.

HIV and the liver

Among individuals with HIV infection, liver disease remains an important cause of morbidity and mortality, even with the availability of agents that cure hepatitis C infection and suppress hepatitis B replication. The causes of liver disease are multifaceted and continue to evolve as the population ages and new etiologies arise. Nonalcoholic fatty liver disease and nonalcoholic steatohepatitis and hepatitis viruses such as A, D, and E have emerged even as hepatitis C has receded. Newer antiretroviral agents may increase risk of weight gain and subsequent fatty infiltration, and prior use of nucleotide-based therapies may continue to impact liver health. Several barriers including economics, social stigma, and psychiatric disease impact identification of liver disease, as well as management and treatment interventions. Hepatocellular carcinoma is emerging as a more common and late-diagnosed complication in those with HIV infection and liver disease.

Hepatitis C virus direct-acting antivirals therapy impacts on extracellular vesicles microRNAs content and on their immunomodulating properties

BACKGROUND & AIMS

Hepatitis C virus (HCV) infection is known to cause major alterations in the cross-talk between hepatic and immune cells thus contributing to the liver disease pathogenesis. Extracellular vesicles have been proved to act as major players in cell-cell communication, and their cargo changes in relation to pathophysiological states. The aim of this study was to evaluate the effects of chronic HCV infection and direct-acting antivirals (DAA) on exosome-delivered microRNAs and on their ability to modulate the innate immune response.

METHODS

Exosomes isolated from the plasma of healthy donors and naïve, viremic HCV patients before and after DAA treatment have been compared for their microRNAs cargo by quantitative polymerase chain reaction. Functional assays with peripheral blood cells from healthy donors were performed to assess exosome-mediated immune responses.

RESULTS

MicroRNAs associated with HCV-related immunopathogenesis which were found to be enriched in exosomes of HCV viremic patients (in particular, miR-122-5p, miR-222-3p, miR-146a, miR-150-5p, miR-30c, miR-378a-3p and miR-20a-5p) were markedly reduced by DAA therapy. This exosome-microRNA cargo modulation parallels changes in their immunomodulatory properties in ex vivo experiments. Exosomes from HCV patients inhibit NK degranulation activity and this effect correlates with miR-122-5p or miR-222-3p levels.

CONCLUSIONS

Enrichment of immunomodulatory microRNAs in exosomes of HCV patients was correlated with their inhibitory activity on innate immune cells function. Direct-acting antivirals (DAA) treatment was observed to revert both microRNA content and functional profiles of systemic exosomes towards those of healthy donors. Exosome-associated microRNAs may provide valuable biomarkers to monitor immune response recovery.

When do co-infections matter?

PURPOSE OF REVIEW

Advances in diagnostic methods mean that co-infections are increasingly being detected in clinical practice, yet their significance is not always obvious. In parallel, basic science studies are increasingly investigating interactions between pathogens to try to explain real-life observations and elucidate biological mechanisms.

RECENT FINDINGS

Co-infections may be insignificant, detrimental, or even beneficial, and these outcomes can occur through multiple levels of interactions which include modulation of the host response, altering the performance of diagnostic tests, and drug-drug interactions during treatment. The harmful effects of chronic co-infections such as tuberculosis or Hepatitis B and C in association with HIV are well established, and recent studies have focussed on strategies to mitigate these effects. However, consequences of many acute co-infections are much less certain, and recent conflicting findings simply highlight many of the challenges of studying naturally acquired infections in humans.

SUMMARY

Tackling these challenges, using animal models, or careful prospective studies in humans may prove to be worthwhile. There are already tantalizing examples where identification and treatment of relevant co-infections seems to hold promise for improved health outcomes.

Consequence of HIV and HCV co-infection on host immune response, persistence and current treatment options

Hepatitis C virus (HCV) is a common opportunistic pathogen especially among Human immunodeficiency virus (HIV) infected patients. Due to incongruous studies, the pathological effect of HCV on HIV induced disease are still not fully understood. While some studies have showed no effect of HCV on HIV infection, others reported a defined role of HCV in aggravating the rates of AIDS-related illnesses and mortality. The explanation of such variances may be due to the host immune response, viral genotypes, sub-type and quasi-species distribution. The factors that complicate the management of HIV/HCV patients are: (1) reduced HCV antibody production, (2) drug interactions, (3) liver disease and (4) different epidemiologic characteristics. However, it is abundantly clear that the morbidity and mortality caused by HCV have increased since the introduction of highly active antiretroviral therapy (HAART) against HIV. In this review, the consequence of HIV/HCV co-infection on host immune response, viral replication, disease progression, mortality and morbidity, viral load, persistence and current treatment options have been discussed. Based on the clinical studies, it is necessary to evaluate the effect of HCV therapy on HIV progression and to provide a fully active HCV treatment for patients receiving HIV treatment. In conclusion, it is recommended to provide fully active HAART therapy in combination with a known HCV therapy.