Dendritic cell maturation in HCV infection: altered regulation of MHC class I antigen processing-presenting machinery

Exosome and virus infection

Exosomes are messengers of intercellular communication in monolayer vesicles derived from cells. It affects the pathophysiological process of the body in various diseases, such as tumors, inflammation, and infection. It has been confirmed that exosomes are similar to viruses in biogenesis, and exosome cargo is widely involved in many viruses’ replication, transmission, and infection. Simultaneously, virus-associated exosomes can promote immune escape and activate the antiviral immune response of the body, which bidirectionally modulates the immune response. This review focuses on the role of exosomes in HIV, HBV, HCV, and SARS-CoV-2 infection and explores the prospects of exosome development. These insights may be translated into therapeutic measures for viral infections and reduce the disease burden.

Proteasome Subunit Beta Type-8 (PSMB8) Gene Polymorphisms in Vitiligo: A Possible Predictor of Auditory Involvement

INTRODUCTION

Proteasome subunit beta type-8 (PSMB8) is a protein that contributes to the complete assembly of 20S proteasome complexes, which play a role in the pathogenesis of vitiligo.

OBJECTIVE

The study aimed to evaluate the association between PSMB8 gene polymorphisms with vitiligo to assess its clinical significance among a sample of Egyptian patients with vitiligo.

METHODS

Genomic DNA was isolated from blood samples of 100 patients with vitiligo and 100 control subjects, and detection of PSMB8 polymorphisms was done by real-time PCR. Data analysis was carried out for the entire cohort. Statistics were performed using software. Audiological evaluation was performed, including pure-tone audiometry, extended high-frequency audiometry, transient evoked otoacoustic emissions, and auditory brainstem response.

RESULTS

There was a significant difference between PSMB8 genotypes and alleles distribution in patients and control groups. Ten percent of the study sample had sensorineural hearing loss. The patients with hearing loss were significantly older (P=0.0002), had significantly later age of onset (P=0.0007), longer duration (P=0.0021), higher body mass index (BMI) (P=0.045), and higher vitiligo area scoring index (VASI) scores (P=0.0015). All patients had extensive forms of vitiligo (generalized and universal). Regarding the VIT rs2071543 polymorphism, all of the patients with hearing loss were carrying the CA and AA genotypes. None of the patients carried the reference genotype, CC. The A allele of VIT rs2071543 was significantly associated with hearing affection (P=0.024).

CONCLUSION

In our study, PSMB8 polymorphism was associated with the susceptibility to develop vitiligo and appeared to have clinical significance among the studied group of patients. Factors predicting auditory abnormalities should be further studied for early detection and management.

Humanized Mouse Models for the Study of Hepatitis C and Host Interactions

Hepatitis C virus (HCV) infection is commonly attributed as a major cause of chronic hepatotropic diseases, such as, steatosis, cirrhosis and hepatocellular carcinoma. As HCV infects only humans and primates, its narrow host tropism hampers in vivo studies of HCV-mammalian host interactions and the development of effective therapeutics and vaccines. In this context, we will focus our discussion on humanized mice in HCV research. Here, these humanized mice are defined as animal models that encompass either only human hepatocytes or both human liver and immune cells. Aspects related to immunopathogenesis, anti-viral interventions, drug testing and perspectives of these models for future HCV research will be discussed.

Maturation of dendritic cells in vitro and immunological enhancement of mice in vivo by pachyman- and/or OVA-encapsulated poly(d,l-lactic acid) nanospheres

Background

Poly lactide (PLA) was proved in the last years to be good for use in sustained drug delivery and as carriers for vaccine antigens. In our previous research, pachyman (PHY)-encapsulated PLA (PHYP) nanospheres were synthesized and their function of controlling drug release was demonstrated.

Purpose

In order to modify the fast drug-release rate of PHY when inoculated alone, the maturation of bone marrow dendritic cells (BMDCs) in vitro and their immunological enhancement in vivo were explored using PHYP nanospheres.

Methods

The maturation and antigen uptake of BMDCs were evaluated, both alone and with formulated antigen PHYP nanospheres, ie, ovalbumin (OVA)-loaded PHYP nanospheres, as an antigen delivery system, to investigate antigen-specific humoral and cellular immune responses.

Results

The results indicated that, when stimulated by PHYP, the BMDCs matured as a result of upregulated expression of co-stimulatory molecules; the mechanism was elucidated by tracing fluorescently labeled antigens in confocal laser scanning microscopy images and observing the uptake of nanospheres by transmission electron microscopy. It was further revealed that mice inoculated with OVA-PHYP had augmented antigen-specific IgG antibodies, increased cytokine secretion by splenocytes, increased splenocyte proliferation, and activation of cluster of differentiation (CD)4⁺ and CD8⁺ T cells in vivo. Elevated immune responses were produced by OVA-PHYP, possibly owing to the activation and maturation of dendritic cells (in draining lymph nodes).

Conclusion

It was corroborated that PHY- and/or OVA-encapsulated PLA nanospheres elicited prominent antigen-presenting effects on BMDCs and heightened humoral and cellular immune responses compared with other formulations.

Dendritic cells in hepatitis and liver transplantation

Dendritic cells (DCs) play a key role in innate immune responses and are also the most effective cells for the activation of T cell immunity. They acquire antigen and process it; then they display it on the cell surface bound in a noncovalent complex with human leukocyte antigen molecules of class I (human leukocyte antigens A, B, and C) and class II (human leukocyte antigen DR). These cells are subdivided into 3 main subsets: 2 called myeloid dendritic cells (mDC) or classical DCs of types 1 and 2, and 1 called plasmacytoid dendritic cells (pDCs). The mDCs process and present antigen while the pDCs also strongly respond to viral signals by secreting type 1 interferon. In the liver, all of these subsets are present. However, their relative abundance is different from the peripheral blood, and it is further modified by liver disease. It appears that in relation to T cell tolerance, both mDCs and pDCs are influenced by the liver milieu and promote T cell inactivation. However, in antiviral responses and in ischemia/reperfusion injury, where innate immune functions are more important, mDCs and pDCs have distinct roles. Liver Transplantation 23 1433-1439 2017 AASLD.

Immune Evasion Strategies during Chronic Hepatitis B and C Virus Infection

Both hepatitis B virus (HBV) and hepatitis C virus (HCV) infections are a major global healthcare problem with more than 240 million and 70 million infected, respectively. Both viruses persist within the liver and result in progressive liver disease, resulting in liver fibrosis, cirrhosis and hepatocellular carcinoma. Strikingly, this pathogenesis is largely driven by immune responses, unable to clear an established infection, rather than by the viral pathogens themselves. Even though disease progression is very similar in both infections, HBV and HCV have evolved distinct mechanisms, by which they ensure persistence within the host. Whereas HCV utilizes a cloak-and-dagger approach, disguising itself as a lipid-like particle and immediately crippling essential pattern-recognition pathways, HBV has long been considered a "stealth" virus, due to the complete absence of innate immune responses during infection. Recent developments and access to improved model systems, however, revealed that even though it is among the smallest human-tropic viruses, HBV may, in addition to evading host responses, employ subtle immune evasion mechanisms directed at ensuring viral persistence in the absence of host responses. In this review, we compare the different strategies of both viruses to ensure viral persistence by actively interfering with viral recognition and innate immune responses.

M1-/M2-macrophage polarization in pseudolobules consisting of adipohilin-rich hepatocytes in thioacetamide (TAA)-induced rat hepatic cirrhosis

INTRODUCTION

Liver steatosis is the most frequent liver disease and may further develop into non-alcoholic steatohepatitis (NASH), liver cirrhosis, and finally hepatocellular carcinoma. Adipophilin (Adp) is localized on lipid droplet membrane in cytoplasm, and its increased expression is related to development of steatosis and NASH. The relationship between M1-/M2-macrophage polarization and Adp-rich hepatocyte-consisting pseudolobules (PLs) was investigated in thioacetamide (TAA)-induced rat cirrhosis.

MATERIALS AND METHOD

F344 rats were injected twice weekly with TAA (100mg/kg bodyweight) and sacrificed at post-first injection (PFI) weeks 5, 10, 15, 20, 25 and 32. Macrophage immunophenotypes and Adp-containing hepatocytes were analyzed by single immunolabeling. Adp and M1-/M2-related factors were analyzed by real -time RT-PCR.

RESULTS

PLs consisting exclusively of Adp-containing hepatocytes (Adp-positive) and PLs consisting of few Adp-containing hepatocytes (Adp-negative) were clearly distinguishable at PFI week 20 onwards. The numbers of M1-macrophages (reacting to CD68 and Iba1) and M2- macrophages (reacting to CD163, CD204 and Gal-3) were considerably greater in Adp-positive PLs. Expressions for both M1 (TNF-α, MCP-1, and Iba1)- and M2 (IL-4, TGF-β1, Gal-3, and Hsp25)-related factors were markedly higher in Adp-positive PLs at PFI week 25. Interestingly, MHC class II-positive macrophages/dendritic cells were increased in Adp-positive clusters/foci at the early stages at PFI weeks 5 and 10, and the level was gradually decreased thereafter.

CONCLUSIONS

M1-/M2-macrophages may simultaneously participate in the pathogenesis of steatosis in TAA-induced cirrhosis through M1- and M2-related factors. MHC class II cells may be responsible for steatosis at early stages, suggesting different functions from the above M1-/M2-macropahges.

Immunopathogenesis of Hepatitis C Virus Infection

Despite advances in therapy, hepatitis C virus infection remains a major global health issue with 3 to 4 million incident cases and 170 million prevalent chronic infections. Complex, partially understood, host-virus interactions determine whether an acute infection with hepatitis C resolves, as occurs in approximately 30% of cases, or generates a persistent hepatic infection, as occurs in the remainder. Once chronic infection is established, the velocity of hepatocyte injury and resultant fibrosis is significantly modulated by immunologic as well as environmental factors. Immunomodulation has been the backbone of antiviral therapy despite poor understanding of its mechanism of action.

New Insights into the Function of the Immunoproteasome in Immune and Nonimmune Cells

The immunoproteasome is a highly efficient proteolytic machinery derived from the constitutive proteasome and is abundantly expressed in immune cells. The immunoproteasome plays a critical role in the immune system because it degrades intracellular proteins, for example, those of viral origin, into small proteins. They are further digested into short peptides to be presented by major histocompatibility complex (MHC) class I molecules. In addition, the immunoproteasome influences inflammatory disease pathogenesis through its ability to regulate T cell polarization. The immunoproteasome is also expressed in nonimmune cell types during inflammation or neoplastic transformation, supporting a role in the pathogenesis of autoimmune diseases and neoplasms. Following the success of inhibitors of the constitutive proteasome, which is now an established treatment modality for multiple myeloma, compounds that selectively inhibit the immunoproteasome are currently under active investigation. This paper will review the functions of the immunoproteasome, highlighting areas where novel pharmacological treatments that regulate immunoproteasome activity could be developed.

Activity-based profiling of the proteasome pathway during hepatitis C virus infection

Hepatitis C virus (HCV) infection often leads to chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. The stability of the HCV proteins is controlled by ubiquitin-dependent and ubiquitin-independent proteasome pathways. Many viruses modulate proteasome function for their propagation. To examine the interrelationship between HCV and the proteasome pathways we employed a quantitative activity-based protein profiling method. Using this approach we were able to quantify the changes in the activity of several proteasome subunits and found that proteasome activity is drastically reduced by HCV replication. The results imply a link between the direct downregulation of the activity of this pathway and chronic HCV infection.

Proteasome- and ethanol-dependent regulation of HCV-infection pathogenesis

This paper reviews the role of the catabolism of HCV and signaling proteins in HCV protection and the involvement of ethanol in HCV-proteasome interactions. HCV specifically infects hepatocytes, and intracellularly expressed HCV proteins generate oxidative stress, which is further exacerbated by heavy drinking. The proteasome is the principal proteolytic system in cells, and its activity is sensitive to the level of cellular oxidative stress. Not only host proteins, but some HCV proteins are degraded by the proteasome, which, in turn, controls HCV propagation and is crucial for the elimination of the virus. Ubiquitylation of HCV proteins usually leads to the prevention of HCV propagation, while accumulation of undegraded viral proteins in the nuclear compartment exacerbates infection pathogenesis. Proteasome activity also regulates both innate and adaptive immunity in HCV-infected cells. In addition, the proteasome/immunoproteasome is activated by interferons, which also induce "early" and "late" interferon-sensitive genes (ISGs) with anti-viral properties. Cleaving viral proteins to peptides in professional immune antigen presenting cells and infected ("target") hepatocytes that express the MHC class I-antigenic peptide complex, the proteasome regulates the clearance of infected hepatocytes by the immune system. Alcohol exposure prevents peptide cleavage by generating metabolites that impair proteasome activity, thereby providing escape mechanisms that interfere with efficient viral clearance to promote the persistence of HCV-infection.