Reduced expression of TRIF in chronic HBV infected Iranian patients

TRIF-dependent signaling and its role in liver diseases

TIR domain-containing adaptor inducing IFN-β (TRIF) is a crucial adaptor molecule downstream of toll-like receptors 3 (TLR3) and 4 (TLR4). TRIF directly binds to TLR3 through its TIR domain, while it associates with TLR4 indirectly through the bridge adaptor molecule TRIF-related adaptor molecule (TRAM). TRIF plays a pivotal role in regulating interferon beta 1 (IFN-β) response, nuclear factor kappa B (NF-κB) signaling, apoptosis, and necroptosis signaling mediated by TLR3 and TLR4. It accomplishes these by recruiting and activating various kinases or transcription factors via its distinct domains. In this review, we comprehensively summarize the TRIF-dependent signaling pathways mediated by TLR3 and TLR4, elucidating key target molecules and downstream pathways. Furthermore, we provide an overview of TRIF's impact on several liver disorders, including drug-induced liver injury, ischemia-reperfusion liver injury, autoimmune hepatitis, viral hepatitis, alcohol-associated liver disease (ALD), metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). We also explore its effects on liver steatosis, inflammation, fibrosis, and carcinogenesis. A comprehensive understanding of the TRIF-dependent signaling pathways, as well as the intricate relationship between TRIF and liver diseases, can facilitate the identification of potential drug targets and the development of novel and effective therapeutics against hepatic disorders.

Natural killer cells and their exosomes in viral infections and related therapeutic approaches: where are we?

Innate immunity is the first line of the host immune system to fight against infections. Natural killer cells are the innate immunity lymphocytes responsible for fighting against virus-infected and cancerous cells. They have various mechanisms to suppress viral infections. On the other hand, viruses have evolved to utilize different ways to evade NK cell-mediated responses. Viruses can balance the response by regulating the cytokine release pattern and changing the proportion of activating and inhibitory receptors on the surface of NK cells. Exosomes are a subtype of extracellular vesicles that are involved in intercellular communication. Most cell populations can release these nano-sized vesicles, and it was shown that these vesicles produce identical outcomes to the originating cell from which they are released. In recent years, the role of NK cell-derived exosomes in various diseases including viral infections has been highlighted, drawing attention to utilizing the therapeutic potential of these nanoparticles. In this article, the role of NK cells in various viral infections and the mechanisms used by viruses to evade these important immune system cells are initially examined. Subsequently, the role of NK cell exosomes in controlling various viral infections is discussed. Finally, the current position of these cells in the treatment of viral infections and the therapeutic potential of their exosomes are reviewed. Video Abstract.

Host Innate Immunity Against Hepatitis Viruses and Viral Immune Evasion

Hepatitis viruses are primary causative agents of hepatitis and represent a major source of public health problems in the world. The host innate immune system forms the first line of defense against hepatitis viruses. Hepatitis viruses are sensed by specific pathogen recognition receptors (PRRs) that subsequently trigger the innate immune response and interferon (IFN) production. However, hepatitis viruses evade host immune surveillance via multiple strategies, which help compromise the innate immune response and create a favorable environment for viral replication. Therefore, this article reviews published findings regarding host innate immune sensing and response against hepatitis viruses. Furthermore, we also focus on how hepatitis viruses abrogate the antiviral effects of the host innate immune system.

The effect of IFN-β 1a on expression of MDA5 and RIG-1 in multiple sclerosis patients

The aims of this study were to compare mRNA levels of melanoma differentiation-associated protein 5 (MDA5) and retinoic acid-inducible gene 1 (RIG-1) in multiple sclerosis (MS) patients in comparison to the healthy controls as well as investigating the effects of IFN-β 1a on the expression of these molecules. In this study, mRNA levels of MDA5 and RIG-1 in peripheral leukocytes of 30 new cases of MS patients and 35 healthy controls were evaluated using the real-time-PCR method. mRNA levels of MDA5 and RIG-1 were determined in the MS patients 6 months after treatment with standard doses of IFN-β 1a. mRNA levels of MDA5 and RIG-1 were significantly decreased in the MS patients in comparison to the healthy controls. The analysis also revealed that IFN-β 1a therapy leads to the upregulation of RIG-1, but not MDA5, in the total MS patients and the female group. MS patients suffer from insufficient expression of MDA5 and RIG-1, and IFN-β 1a therapy results in the upregulation of RIG-1 in the patients, especially in the female patients. Thus, it seems that IFN-β 1a not only decreased pathogenic inflammatory responses but also modulated the expression of RIG-1 to protect the patients from infectious diseases and upregulation of IFN-I in a positive feedback.

Up-regulation of RIP1 and IPS-1 in chronic HBV infected patients

IPS-1 and RIP1 are the main downstream molecules of RIG1 and MDA5, as intracytoplasmic receptors, which are the main receptors involved in recognition of internal and external viral double-stranded RNA. In this project, mRNA levels of IPS-1 and RIP1 were investigated in the peripheral blood immune cells of chronic hepatitis B (CHB) patients. IPS-1 and RIP1 mRNA levels were measured in 60 CHB patients and 120 healthy subjects, using RT-qPCR technique. A significant increase in expression levels of IPS-1 and RIP1 was found in patients when compared to healthy individuals. There was no correlation between IPS-1 and RIP1expression levels with the serum levels of hepatitis B e-Antigen (HBeAg) and liver enzymes in patients. Based on the results, it seems that IPS-1 and RIP1 can participate in the induction of low chronic inflammation, which is a main cause of liver cirrhosis and hepatocellular carcinoma.

Clinical significance of expression of TLR3 and TLR4 in liver tissue of patients with chronic hepatitis B

AIM

To investigate the correlation of the expression of Toll-like receptors 3 and 4 (TLR3, TLR4) with liver inflammation and liver fibrosis degree in the liver tissue of patients with chronic hepatitis B (CHB).

METHODS

One hundred and fifty-six CHB liver tissues obtained by liver biopsy were subjected to immunohistochemical staining for TLR3 and TLR4. Ten normal liver tissues served as controls. Then, immunohistochemical staining was quantified, and its correlation liver inflammatory activity and liver fibrosis degree was analyzed statistically.

RESULTS

TLR3 was strongly expressed in liver tissue of patients with CHB, mainly in the cytoplasm of liver cells and occasionally in the nucleus. The expression of TLR3 in liver tissue had a significant positive correlation with inflammation grade (r_s = 0.528, P < 0.01), and there was a significant linear relationship between them (χ² = 16.679, P < 0.01). The expression of TLR3 was also correlated with liver fibrosis degree (r_s = 0.510, P < 0.01), and there was a significant linear relationship between them (χ² = 16.654, P < 0.01). TLR4 was obviously expressed in liver cells, mainly in the cytoplasm and occasionally on cell membrane The expression of TLR4 had a significant positive correlation of liver fibrosis degree (r_s = 0.354, P < 0.01), and there was a significant linear relationship between them (χ² = 10.124, P < 0.05).

CONCLUSION

High expression of TLR3 and TRL4 is positively correlated with liver inflammation and liver fibrosis degree in CHB patients, suggesting that they might participate in the pathogenesis of CHB.

Differential expression of innate immune response genes in clinical phases of chronic hepatitis B infection

We investigated innate immune gene expression in clinical phases of chronic hepatitis B infection, including immune tolerant (IT), immune active (IA), inactive carrier (IC) and hepatitis B e antigen (HBeAg)-negative phases, as well as healthy controls. Expression levels of interferon types I, II and III, their receptor subunits, IRFs, TLRs and other IFN-induced genes in peripheral blood mononuclear cells were compared. Forty HBsAg-positive treatment-naïve subjects without co-infection with HIV, HCV or HDV were enrolled. To complement the viral load, the expression levels of 37 innate immune genes were measured by qPCR. The highest response of the innate immune system was observed in the IT and HBeAg-negative phases, and the IC phase had the lowest response; 31 of the 37 studied genes reached their maximum mRNA expression levels in the IT and HBeAg-negative phases, and the minimum expression levels of 23 genes were found in the IC phase. The highest mRNA expression levels of IFNs, IFN receptor subunits, IRFs and TLRs genes in all clinical phases were IFN-λ2 and 3, IFN-γR2, IRF7 and TLR7, and the lowest levels of mRNA expression were observed for IFN-α, IFN-λR1, IRF8 and TLR2. We conclude that innate immune response genes are expressed differentially among chronic HBV phases, and this difference may help to develop new precise and noninvasive methods to determine the progression of disease in chronic HBV patients.

Association of S100 calcium-binding protein A12, receptor for advanced glycation endproducts, and nuclear factor-κB expression with inflammation in pulp tissues from tooth caries

AIM

S100 calcium-binding protein A1 (S100A12) is a pro-inflammatory molecule which is secreted during inflammation and induces chemotaxis and the production of pro-inflammatory cytokines via interaction with receptor for advanced glycation endproducts (RAGE) and subsequent, activation of nuclear factor-κB (NF-κB). The present study was designed to determine the expression levels of S100A12, RAGE, and NF-κB in the inflamed pulp of carried teeth.

METHODS

In the present study, mRNA from 50 inflamed pulp and 50 healthy pulp were used for expression studies using real-time polymerase chain reaction. The expression levels of S100A12, RAGE, and NF-κB were compared between inflamed and healthy tissues.

RESULTS

The results revealed that the expression of S100A12, but not of RAGE or NF-κB, was significantly decreased in inflamed pulp when compared to healthy pulp. mRNA levels of RAGE were also increased in the inflamed pulp taken from men when compared with women.

CONCLUSION

The results suggest that S100A12 does not participate in the induction of inflammation in dental pulp. However, RAGE can participate in the inflammation in the pulp of males.

Innate immunity related pathogen recognition receptors and chronic hepatitis B infection

Innate immunity consists of several kinds of pathogen recognition receptors (PRRs), which participate in the recognition of pathogens and consequently activation of innate immune system against pathogens. Recently, several investigations reported that PRRs may also play key roles in the induction/stimulation of immune system related complications in microbial infections. Hepatitis B virus (HBV), as the main cause of viral hepatitis in human, can induce several clinical forms of hepatitis B and also might be associated with hepatic complications such as cirrhosis and hepatocellular carcinoma (HCC). Based on the important roles of PRRs in the eradication of microbial infections including viral infections and their related complications, it appears that the molecules may be a main part of immune responses against viral infections including HBV and participate in the HBV related complications. Thus, this review article has brought together information regarding the roles of PRRs in immunity against HBV and its complications.

Evaluation of NLRC4, NLRP1, and NLRP3, as Components of Inflammasomes, in Chronic Hepatitis B Virus-Infected Patients

Nucleotide-binding domain leucine repeats (NLRs) are required for the recognition of various molecules that are expressed within microbes and are able to actuate appropriate immune responses via activation of cytokines. The current study evaluates the expression levels of NLRP1 and NLRC4, which are components of inflammasomes, in chronic hepatitis B (CHB) virus-infected patients. This study recruited two series of CHB patients (each contained 60 patients) and 60 healthy controls. Real-time polymerase chain reaction (PCR) was employed to evaluate mRNA expression levels of NLRP1, NLRP3, and NLRC4 as well as hepatitis B virus (HBV)-DNA copy number. Serum levels of liver markers were also used to evaluate the patients. Hepatitis B envelope antigen (HBeAg) and hepatitis B surface antigen (HBsAg) were also examined in all patients to evaluate infection. The data showed that expression levels of NLRC4 and NLRP1 were not significantly different in circulating monocytes of CHB patients when compared with those of healthy controls. Furthermore, the data indicate that mRNA levels of NLRP1, NLRP3, and NLRC4 were also not altered in CHB patients regardless of HBV-DNA copy numbers/mL and HBeAg status. The data revealed that mRNA expression levels of NLRP1 and NLRC4 were not altered in CHB patients, suggesting that these genes are not responsible for the impaired immune responses against HBV observed in these patients.

The link between TLR7 signaling and hepatitis B virus infection

Toll-Like Receptors (TLRs) play crucial roles in recognition and induction of appropriate immune responses against viral infections, including hepatitis B. TLR7 detects intracellular viral single strand RNA which leads to the activation of several pro-inflammatory transcription factors via the MYD88 dependent pathway. Patients with prolonged infectious forms of hepatitis B, including active and inactive chronic forms, are unable to clear HBV from hepatocytes completely. It is believed that the differences in genetic and immunological parameters of the patients and clearance subjects, who successfully clear HBV infections, are the main factors responsible for allowing the long term infections to persist. It appears that defective expression of TLR7 may result in impaired immune responses against HBV. The aim of this review is to address the recent information regarding the crucial roles played by TLR7 in hepatitis B infection and also the main mechanisms used by HBV to escape from recognition by TLR7 in prolonged HBV infected patients. Considering that chronic hepatitis B infection is not yet curable, it could be possible to activate TLR7-related immunological pathways as a therapy directed towards persistent HBV infection. Hence, another aim of this study is to present recent developments of TLR7 agonists as a therapeutic strategy for chronic hepatitis B.

Innate immune targets of hepatitis B virus infection

Approximately 400 million people are chronically infected with hepatitis B virus (HBV) globally despite the widespread immunization of HBV vaccine and the development of antiviral therapies. The immunopathogenesis of HBV infection is initiated and driven by complexed interactions between the host immune system and the virus. Host immune responses to viral particles and proteins are regarded as the main determinants of viral clearance or persistent infection and hepatocyte injury. Innate immune system is the first defending line of host preventing from virus invasion. It is acknowledged that HBV has developed active tactics to escape innate immune recognition or actively interfere with innate immune signaling pathways and induce immunosuppression, which favor their replication. HBV reduces the expression of pattern-recognition receptors in the innate immune cells in humans. Also, HBV may interrupt different parts of antiviral signaling pathways, leading to the reduced production of antiviral cytokines such as interferons that contribute to HBV immunopathogenesis. A full comprehension of the mechanisms as to how HBV inactivates various elements of the innate immune response to initiate and maintain a persistent infection can be helpful in designing new immunotherapeutic methods for preventing and eradicating the virus. In this review, we aimed to summarize different branches the innate immune targeted by HBV infection. The review paper provides evidence that multiple components of immune responses should be activated in combination with antiviral therapy to disrupt the tolerance to HBV for eliminating HBV infection.

Intrahepatic Toll-Like Receptor 3 in Chronic HBV Infection Subjects: Asymptomatic Carriers, Active Chronic Hepatitis, Cirrhosis, and Hepatocellular Carcinoma

BACKGROUND

The entire disease spectrum of chronic HBV infection (CHB) includes asymptomatic carriers (AC), active chronic hepatitis (ACH), cirrhosis (Cir), and hepatocellular carcinoma (HCC). Previous study have demonstrated that the costimulation profiles from the livers of patients influenced immune responses and played various immunological roles in AC, ACH, Cir, and HCC. In addition, activation of TLR3 signaling in the liver may contribute to HBV clearance, although some HBV components are able to block TLR3 signaling and counteract HBV clearance through positive or negative feedback loops. Previous clinical studies have demonstrated that different TLR3 expressions are present in ACH patients, but no studies investigated the expression of TLR3 proteins in the livers of patients with AC, Cir, or HCC.

OBJECTIVES

This study investigated intrahepatic TLR3 expression throughout the entire disease spectrum of CHB patients and assessed the interrelations between TLR3 and costimulation proteins.

PATIENTS AND METHODS

Patients with ACH, Cir, HCC, and AC and healthy donors (HD) were recruited. TLR3 expression in the livers of patients were investigated using western blot analysis and immunohistochemistry. Correlations between TLR3 and costimulation proteins, including CD80, CD86, CD83, CD28, CTLA-4, CD40, and ICAM-1, were assessed.

RESULTS

The TLR3 protein in the ACH group tended toward reduction although the P Value of the comparison between the ACH group and HD group was not statistically significant. The TLR3 levels in the HCC, AC, and Cir groups were higher than those in the HD and ACH groups. TLR3 was not interrelated with all costimulation proteins in the DCs and T cells in all five groups. No group presented any interrelation between TLR3 and CD40, except the AC group.

CONCLUSIONS

The AC, HCC, and Cir patients displayed increased levels of the intrahepatic TLR3 protein compared to the HD and AC patients. Both activation of TLR3/INF-β signaling and inhibition of TLR3/INF-β signaling by HBV components influenced TLR3 expression in the AC, ACH, Cir, and HCC subjects. However, TLR3 signaling did not influence the expression of costimulatory protein in the ACH, Cir, or HCC patients. TLR3/ IFN-β signaling did influence immune responses in the livers of CHB patients.

TRIF-dependent TLR signaling, its functions in host defense and inflammation, and its potential as a therapeutic target

Toll/IL-1R domain-containing adaptor-inducing IFN-β (TRIF)-dependent signaling is required for TLR-mediated production of type-I IFN and several other proinflammatory mediators. Various pathogens target the signaling molecules and transcriptional regulators acting in the TRIF pathway, thus demonstrating the importance of this pathway in host defense. Indeed, the TRIF pathway contributes to control of both viral and bacterial pathogens through promotion of inflammatory mediators and activation of antimicrobial responses. TRIF signaling also has both protective and pathologic roles in several chronic inflammatory disease conditions, as well as an essential function in wound-repair processes. Here, we review our current understanding of the regulatory mechanisms that control TRIF-dependent TLR signaling, the role of the TRIF pathway in different infectious and noninfectious pathologic states, and the potential for manipulating TRIF-dependent TLR signaling for therapeutic benefit.

Are RIG-1 and MDA5 Expressions Associated with Chronic HBV Infection?

Melanoma differentiation-associated protein 5 (MDA5) and retinoic acid-inducible gene 1 (RIG-1) as the pattern recognition receptors play important roles in viral mRNA recognition. Chronic HBV-infected (CHB) patients are unable to properly respond to hepatitis B virus (HBV). Therefore, the aim of the present study was to evaluate the mRNA levels of MDA5 and RIG-1 in the peripheral blood immune cells of CHB patients in comparison to healthy controls. In this cross-sectional study, the mRNA levels of MDA5 and RIG-1 were examined in 60 CHB patients and 60 healthy controls using the real-time polymerase chain reaction (PCR) technique. Our results showed that mRNA levels of MDA5 and RIG-1 were significantly decreased and increased, respectively, in CHB patients when compared to healthy controls. Our results also revealed that mRNA levels of MDA5 and RIG-1 were not altered among CHB patients with various states of e-antigen of hepatitis B and HBV-DNA viral loads. According to the results presented here, it may be concluded that downregulation of MDA5 may be a responsible mechanism from several reasons, which leads to HBV persistence in CHB patients.

Innate immune evasion by hepatitis B virus-mediated downregulation of TRIF

Hepatocytes are the target host cells during hepatitis B virus (HBV) infection. Recent studies indicate that the innate immune response of hepatocytes plays an important role in inhibiting HBV replication. TIR-domain-containing adaptor inducing interferon-beta (TRIF) is a key component in innate immune signaling pathways. In this study, we found that the TRIF protein was downregulated in human hepatoma cell lines and liver tissue samples harboring HBV. Hepatitis B virus X protein (HBX) reduced TRIF protein expression in a dose-dependent manner via the proteasomal pathway. HBX appeared to not directly interact with TRIF as these proteins failed to co-immunoprecipitate when overexpressed in hepatoma cells. TRIF upregulation in hepatoma cell lines dramatically inhibited HBV transcription and expression of its viral proteins. Cellular apoptosis induced by TRIF was also confirmed in hepatoma cell lines. Taken together, these findings reveal a new mechanism for HBV evasion of the cellular innate immunity by HBX-mediated degradation of TRIF protein in hepatocytes.

TLR9: an important molecule in the fight against hepatitis B virus

Hepatitis B virus (HBV) is the most prevalent infectious agent that can induce severe liver disease. Patients infected with long-term HBV, including chronic, asymptomatic and occult forms, cannot clear HBV from infected hepatocytes completely. It is not clear why some people can clear the infection while others cannot. Furthermore, the main mechanisms responsible for progression of the infections are not fully understood. It has been hypothesised that differences in genetic and immunological parameters between patients and subjects who successfully clear HBV infections are responsible for inducing the long-term forms of the infection. Previous investigations showed that Toll-like receptors (TLRs) play important roles in immune responses, especially innate immunity, against viral infections, including hepatitis B. TLR9 detects intracellular viral dsDNA, which results in the activation of an immune response against HBV. However, defects in this system may result in an attenuated response ultimately leading to long-term HBV infections. Targeting the defects in TLR9 or reactivating the downstream pathways that are normally switched on by TLR9 in response to HBV infection is a new approach to the treatment of long-term HBV infection. However, the pathways and defects seen in patients with long-term HBV need to be thoroughly explored before therapeutics can be applied in the clinical setting. Furthermore, the apparently multigenic nature of long-term HBV infection suggests that treatment of patients may need to be personalised.

Toll-like receptor 4 and hepatitis B infection: molecular mechanisms and pathogenesis

Hepatitis B virus (HBV) infection mainly causes liver disease, including inflammation, cirrhosis, and hepatocellular carcinoma (HCC). It has been documented that prolonged hepatitis B-infected patients are unable to clear HBV from hepatocytes completely. Previous investigations have suggested that various genetic and immunologic parameters may be responsible for the induction of prolonged infection forms. Toll-like receptors (TLRs), as members of pathogen recognition receptors (PRRs), play critical roles in the recognition of viruses and the induction of appropriate immune responses. Thus, TLRs may be considered as essential sensors for the recognition of HBV and the induction of immune responses against this virus. It has been documented that TLR4 plays key roles in the detection of several microbial pathogen-associated molecular pattern molecules, including bacterial lipopolysaccharide (LPS), as well as endogenous ligands (damage-associated molecular pattern molecules) and subsequently activates pro-inflammatory transcription factors in either MYD88 or TRIF dependent pathways. Previous investigations have proposed that TLR4 might be involved in appropriate immune responses against HBV. Therefore, the aim of this review is to present the recent data regarding the important roles of TLR4 in HBV recognition and regulation of immune responses against this virus, and also its roles in the pathogenesis of cirrhosis and HCC as complications of prolonged hepatitis B infections.

Can Toll-Like Receptor (TLR) 2 be considered as a new target for immunotherapy against hepatitis B infection?

The current literature describes pivotal mechanisms in which hepatitis B virus (HBV) induces liver diseases including inflammation, cirrhosis and hepatocellular carcinoma (HCC). It appears that differences in genetic and immunological parameters between patients and controls may be responsible for inducing the prolonged forms of the infection. Previous studies demonstrated that Toll-Like Receptors (TLRs) play key roles in viral recognition and inducing appropriate immune responses. Therefore, TLRs can be considered as key sensors for HBV recognition and subsequent induction of immune responses against this virus. It has also been shown that the TLR2 detects several microbial PAMPs either in its homodimer form or in a heterodimer with TLR1 or TLR6 and subsequently activates NF-κB in a MYD88 dependent manner. Therefore, defective TLR2 expression may result in impaired immune responses against HBV which is reported in long-term forms of hepatitis B. This review presents the recent data regarding the status and important roles played by TLR2 in HBV recognition and induction or suppression of immune responses against HBV as well as its roles in the pathogenesis of cirrhosis and HCC in prolonged hepatitis B forms.