Impaired antigen processing and presentation machinery is associated with immunotolerant state in chronic hepatitis B virus infection

TLR agonists as vaccine adjuvants in the prevention of viral infections: an overview

Tol-like receptor (TLR) agonists, as potent adjuvants, have gained attention in vaccine research for their ability to enhance immune responses. This study focuses on their application in improving vaccine efficacy against key viral infections, including hepatitis B virus (HBV), hepatitis C virus (HCV), human immunodeficiency virus (HIV), SARS-CoV-2, influenza virus, and flaviviruses, including West Nile virus, dengue virus, and chikungunya virus. Vaccines are crucial in preventing microbial infections, including viruses, and adjuvants play a vital role in modulating immune responses. However, there are still many diseases for which effective vaccines are lacking or have limited immune response, posing significant threats to human health. The use of TLR agonists as adjuvants in viral vaccine formulations holds promise in improving vaccine effectiveness. By tailoring adjuvants to specific pathogens, such as HBV, HCV, HIV, SARS-CoV-2, influenza virus, and flavivirus, protective immunity against chronic and emerging infectious disease can be elicited.

To the Skin and Beyond: The Immune Response to African Trypanosomes as They Enter and Exit the Vertebrate Host

African trypanosomes are single-celled extracellular protozoan parasites transmitted by tsetse fly vectors across sub-Saharan Africa, causing serious disease in both humans and animals. Mammalian infections begin when the tsetse fly penetrates the skin in order to take a blood meal, depositing trypanosomes into the dermal layer. Similarly, onward transmission occurs when differentiated and insect pre-adapted forms are ingested by the fly during a blood meal. Between these transmission steps, trypanosomes access the systemic circulation of the vertebrate host via the skin-draining lymph nodes, disseminating into multiple tissues and organs, and establishing chronic, and long-lasting infections. However, most studies of the immunobiology of African trypanosomes have been conducted under experimental conditions that bypass the skin as a route for systemic dissemination (typically via intraperitoneal or intravenous routes). Therefore, the importance of these initial interactions between trypanosomes and the skin at the site of initial infection, and the implications for these processes in infection establishment, have largely been overlooked. Recent studies have also demonstrated active and complex interactions between the mammalian host and trypanosomes in the skin during initial infection and revealed the skin as an overlooked anatomical reservoir for transmission. This highlights the importance of this organ when investigating the biology of trypanosome infections and the associated immune responses at the initial site of infection. Here, we review the mechanisms involved in establishing African trypanosome infections and potential of the skin as a reservoir, the role of innate immune cells in the skin during initial infection, and the subsequent immune interactions as the parasites migrate from the skin. We suggest that a thorough identification of the mechanisms involved in establishing African trypanosome infections in the skin and their progression through the host is essential for the development of novel approaches to interrupt disease transmission and control these important diseases.

CON: All Patients With Immune-Tolerated Hepatitis B Virus Do Not Need to Be Treated

http://aasldpubs.onlinelibrary.wiley.com/hub/journal/10.1002/(ISSN)2046-2484/video/15-1-reading-attar a video presentation of this article.

Immune Ecosystem of Virus-Infected Host Tissues

Virus infected host cells serve as a central immune ecological niche during viral infection and replication and stimulate the host immune response via molecular signaling. The viral infection and multiplication process involves complex intracellular molecular interactions between viral components and the host factors. Various types of host cells are also involved to modulate immune factors in delicate and dynamic equilibrium to maintain a balanced immune ecosystem in an infected host tissue. Antiviral host arsenals are equipped to combat or eliminate viral invasion. However, viruses have evolved with strategies to counter against antiviral immunity or hijack cellular machinery to survive inside host tissue for their multiplication. However, host immune systems have also evolved to neutralize the infection; which, in turn, either clears the virus from the infected host or causes immune-mediated host tissue injury. A complex relationship between viral pathogenesis and host antiviral defense could define the immune ecosystem of virus-infected host tissues. Understanding of the molecular mechanism underlying this ecosystem would uncover strategies to modulate host immune function for antiviral therapeutics. This review presents past and present updates of immune-ecological components of virus infected host tissue and explains how viruses subvert the host immune surveillances.

Immune balance in Hepatitis B Infection: Present and Future Therapies

Chronic hepatitis B virus (HBV) infection affects millions of people worldwide and about half a million people die every year. India represents the second largest pool of chronic HBV infections with an estimated 40 million chronically infected patients. Persistence or clearance of HBV infection mainly depends upon host immune responses. Chronically infected individuals remain in immune tolerant phase unless HBV flares and leads to the development of chronic active hepatitis or acute-on-chronic liver failure. Strategies based on inhibition of viral replication (nucleoside analogues) or immune modulation (interferons) as monotherapy, or in combination in sequential therapies, are currently being used globally for reducing HBV viral load and mediating HBsAg clearance. However, the immune status and current therapies for promoting sustained virological responses in HBV-infected patients remain suboptimal. Elimination of cccDNA is major challenge for future therapies, and new molecules such as NTCP, Toll-like receptor (TLR)7 agonist (GS9620) and cyclophilin have emerged as potential targets for preventing HBV entry and replication. Other than these, HBV cccDNA elimination is the major target for future therapies.

A novel mutation in TAP1 gene leading to MHC class I deficiency: Report of two cases and review of the literature

Major histocompatibility complex (MHC) class I deficiency syndrome is a rare primary immunodeficiency caused by mutations in the peptide transporter complex associated with antigen presentation (TAP) gene which plays a crucial role in intracellular peptide antigen presentation. A few cases have been reported to date. Recurrent sinopulmonary infections and skin ulcers are the main characteristics of the syndrome. Here we report two siblings diagnosed with TAP1 deficiency syndrome associated only with recurrent sinopulmonary infections with the description of a novel mutation leading to a premature stop codon in TAP1 gene and review of the relevant literature. Both of the siblings had recurrent sinopulmonary infections since childhood, responded to antibiotherapy well, neither of them had hospitalization history because of infections. One had chronic hepatitis B infection which may possibly be related to TAP1 gene defect.

HBV: Do I treat my immunotolerant patients?

Immunotolerant patients with chronic hepatitis B virus (HBV) infection are characterized by positive HBeAg, high viral replication, persistently normal ALT and no or minimal liver damage. Since the risk of the progression of liver disease and the chance of a sustained response with existing anti-HBV agents are low, current guidelines do not recommend treatment but close monitoring with serial alanine aminotransferase (ALT) and HBV DNA measurements instead. However, not treating all these patients is a concern because advanced histological lesions have been reported in certain cases who are usually older (>30-40 years old), and continued high HBV replication could increase the risk of hepatocellular carcinoma (HCC). Thus, the optimal management of immunotolerant patients is often individualised according to age, which is associated with histological severity and patient outcome. In particular, immunotolerant patients <30 years old can be monitored for ALT and HBV DNA, while treatment is often recommended in the few patients over 40. A liver biopsy and/or non-invasive assessment of fibrosis may be helpful to determine the therapeutic strategy in patients between 30 and 40 years old. Moreover, there are three specific subgroups of immunotolerant patients who often require treatment with oral anti-HBV agents: patients who will receive immunosuppressive treatment or chemotherapy, women with serum HBV DNA >10(6-7) IU/ml during the last trimester of pregnancy and certain healthcare professionals with high viraemia levels. More studies are needed to further clarify the natural history for the optimal timing of treatment in this setting.

Natural killer cells in hepatitis B virus infection

Natural killer cells are a unique type of lymphocytes with cytotoxic capacity, and play important roles against tumors and infections. Recently, natural killer cells have been increasingly valued in their effects in hepatitis B virus infection. Since hepatitis B virus is not cytopathic, the subsequent antiviral immune responses of the host are responsible for sustaining the liver injury, which may result in cirrhosis and even hepatocellular carcinoma. Many studies have confirmed that natural killer cells participate in anti-hepatitis B virus responses both in the early phase after infection and in the chronic phase via cytolysis, degranulation, and cytokine secretion. However, natural killer cells play dichotomic roles: they exert antiviral and immunoregulatory functions whilst contribute to the pathogenesis of liver injury. Here, we review the roles of natural killer cells in hepatitis B virus infection, introducing novel therapeutic strategies for controlling hepatitis B virus infection via the modulation of natural killer cells.

Role of natural kill cells in hepatitis B virus infection

Natural killer (NK) cells are a unique group of lymphocytes with cytotoxicity, playing an important role in anti-tumor and anti-infection activities. Recently, NK cells are increasingly recognized to play a role during hepatitis B virus (HBV) infection. Studies have confirmed NK cells participate in anti-HBV responses by secreting cytokines, mediating apoptosis and killing target cells, indicating a potential strategy for controlling HBV infection via regulation of NK cell functions. This review discusses the contribution of NK cells to HBV elimination, liver injury, and other parts of immune system and the formulation of new therapeutic strategies.

New insights into how HBV manipulates the innate immune response to establish acute and persistent infection

The mechanisms by which HBV establishes and maintains chronic infection are poorly understood. Although adult acquired HBV is generally cleared by a robust immune response, most individuals infected at childbirth or in very early childhood develop lifelong chronic infection. In addition, acute infections are unresolved in approximately 5% of individuals infected in adulthood. The host cell mechanisms that ensure establishment and resolution of acute infection and persistent infection remain unclear. Currently, two schools of thought suggest that either HBV is a 'stealth' virus, which initially establishes infection by avoiding host innate immune responses, or that HBV facilitates initial infection and progression to persistence by actively manipulating the host innate immune response to its advantage. There is increasing evidence that activation of innate host cell signalling pathways plays a major role in limiting adult acquired HBV infection and that, in turn, HBV has evolved numerous strategies to counteract these defence mechanisms. In this review, we summarize current knowledge regarding innate immune responses to HBV infection and discuss how HBV regulates cell signalling pathways to its advantage, particularly in the setting of chronic HBV infection. In turn, we show how an intimate knowledge of innate immune responses is driving development of novel therapeutic agents to treat chronic HBV infection.

A systematic analysis of the predicted human La protein targets identified a hepatitis B virus infection signature

The human La (hLa) protein functions in RNA metabolism and is activated by casein kinase 2 (CK2) phosphorylation. Hepatitis B virus (HBV) can exploit hLa to stabilize its RNA and promote its pathogenesis. To enhance our knowledge of host molecular pathways involved in HBV pathogenesis, a bioinformatic approach was used to generate an expression profile of all predicted target genes of CK2-activated hLa in HBV-infected cells. A computerized literature search was performed to identify English language studies of HBV-, hLa- and CK2-related molecules. The data were pooled and the genes were classified in three functional groups by gene ontology (GO) analysis. HBV, hLa and CK2 targets were predicted, respectively, by a computational method, followed by screening for matching gene symbols in the NCBI human sequences, GO, pathway and network analyses. hLa targets and respective networks in the viral mechanisms of HBV were obtained by the final integrative analysis. Thirty-seven hub genes were identified by overlap calculation, suggesting that hLa may play an important role in the development and progression of HBV through cytokine-cytokine receptor interaction, hematopoietic cell lineage, cell adhesion molecules (CAMs), antigen processing and presentation, Jak-STAT signalling pathway, natural killer cell-mediated cytotoxicity, apoptosis, T-cell receptor signalling pathway, complement and coagulation cascades, protein export and other pathways. Our data may help researchers to predict the molecular mechanisms of hLa in the development and progression of HBV through CK2 comprehensively. Moreover, the present data indicate that hLa targets may be a series of promising candidates for HBV.

Association of TAP1 and TAP2 polymorphisms with the outcome of persistent HBV infection in a northeast Han Chinese population

OBJECTIVE

Transporter associated with antigen processing (TAP) plays a central role in a cellular immune response against HBV. Polymorphisms exist at the coding region of TAP and alter its structure and function. The aim of this study was to evaluate the potential relationship between polymorphisms of TAP and different outcomes of persistent HBV infection in a Han population in northeastern China.

MATERIAL AND METHODS

189 HBV spontaneously recovered (SR) subjects, 571 HBV-infected patients including 180 chronic hepatitis B (CHB), 196 liver cirrhosis (LC) and 195 hepatocellular carcinoma (HCC) individuals were included in this study. TAP1-333 Ile/Val and -637 Asp/Gly, TAP2-651 Arg/Cys and -687 Stop/Gln were genotyped in all the samples by using a PCR-RFLP method.

RESULTS

The frequency of TAP1-637-Gly (allele G) was significantly higher in persistently HBV-infected individuals (CHB and LC) than that of SR subjects (OR = 1.58, 95% CI 1.12-2.45, p = 0.024; OR = 1.78, 95% CI 1.27-2.68, p = 0.002) by a logistic regression analysis. In addition, the statistically significant difference in the distribution of TAP2-651-Cys (allele T) was observed between HCC cases and SR controls (OR = 2.30, 95% CI 1.51-3.72, p < 0.001), and TAP2-687-Gln (allele C) in CHB patients was more common than that in SR subjects (OR = 1.41, 95% CI 1.13-1.97, p = 0.021). The data also revealed that haplotype 687 Gln-651 Cys-637 Gly-333 Ile was strongly associated with persistent HBV infection (CHB, LC and HCC) (p < 0.001, < 0.05 and < 0.001, respectively).

CONCLUSION

These results suggested that TAP variants were likely to play a substantial role in different outcomes of persistent HBV infection in the studied population.

Naturally occurring core immune-escape and carboxy-terminal mutations\truncations in patients with e antigen negative chronic hepatitis B

INTRODUCTION

Hepatocellular injury is often progressive in patients with hepatitis B e antigen negative chronic hepatitis B (HBeAg -ve CHB). There is scant data on association of core mutations occurring in patients with HBeAg -ve CHB with severity of liver disease.

MATERIALS AND METHODS

Hundred and eighteen patients with chronic infection who were HBeAg negative, anti-HBe, and HBV DNA positive were enrolled. Precore and core regions were amplified, sequenced, and analyzed for precore, T helper, cytotoxic T lymphocytes (CTLs), B-cell epitope, and core carboxy-terminal region mutations.

RESULTS

Majority of patients were infected with HBV genotype D: 96 (81%) [D1: 16, D2: 55 and D5: 25] followed by genotype A1: 15 (13%) and genotype C: 7 (6%) [C1: 5 and unidentified subgenotype C: 2]. Classical (A1896) as well as nonclassical precore region mutations were detected in 30 (25%) and in 9 (7.6%) patients, respectively. Core immune escape, core carboxy-terminal mutations and truncations were detected in 61 (52%), 11 (9.3%), and 14 (12%) patients, respectively. Three core immune escape mutations were significantly higher in patients with coexisting precore stop codon compared with patients without precore stop codon mutation, cT12S (43 vs. 8%, p < 0.001), cS21T (16 vs. 3.4%, p < 0.026), and cE77D (30 vs. 4.5%, p < 0.002). When frequency of core immune escape mutations was compared among CHB and decompensated patients, and cT12S: (27 vs. 10%, p < 0.05), cS21T (16 vs. 1.35%, p < 0.01), cT67P/N: (20 vs. 4%, p < 0.001), cE113D (11.37 vs. 1.35%, p < 0.05), and cP130T/Q (7 vs. 0%, p < 0.001) mutations were found to be significantly higher in decompensated patients.

CONCLUSION

Core immune-escape mutations cT12S, cS21T, cT67P, cE113D, and cP130T/Q are significantly higher in decompensated liver disease patients and could influence the severity of liver disease in HBeAg -ve CHB patients.

Hepatitis B virus limits response of human hepatocytes to interferon-α in chimeric mice

BACKGROUND & AIMS

Interferon (IFN)-α therapy is not effective for most patients with chronic hepatitis B virus (HBV) infection for reasons that are not clear. We investigated whether HBV infection reduced IFN-α-mediated induction of antiviral defense mechanisms in human hepatocytes.

METHODS

Human hepatocytes were injected into severe combined immune-deficient mice (SCID/beige) that expressed transgenic urokinase plasminogen activator under control of the albumin promoter. Some mice were infected with HBV; infected and uninfected mice were given injections of human IFN-α. Changes in viral DNA and expression of human interferon-stimulated genes (ISGs) were measured by real-time polymerase chain reaction, using human-specific primers, and by immunohistochemistry.

RESULTS

Median HBV viremia (0.8log) and intrahepatic loads of HBV RNA decreased 3-fold by 8 or 12 hours after each injection of IFN-α, but increased within 24 hours. IFN-α activated expression of human ISGs and nuclear translocation of signal transducers and activators of transcription-1 (STAT1) in human hepatocytes that repopulated the livers of uninfected mice. Although baseline levels of human ISGs were slightly increased in HBV-infected mice, compared with uninfected mice, IFN-α failed to increase expression of the ISGs OAS-1, MxA, MyD88, and TAP-1 (which regulates antigen presentation) in HBV-infected mice. IFN-α did not induce nuclear translocation of STAT1 in HBV-infected human hepatocytes. Administration of the nucleoside analogue entecavir (for 20 days) suppressed HBV replication but did not restore responsiveness to IFN-α.

CONCLUSIONS

HBV prevents induction of IFN-α signaling by inhibiting nuclear translocation of STAT1; this can interfere with transcription of ISGs in human hepatocytes. These effects of HBV might contribute to the limited effectiveness of endogenous and therapeutic IFN-α in patients and promote viral persistence.