Liver-derived cytotoxic T cells in hepatitis A virus infection

Sex differences in hepatitis A incidence rates-a multi-year pooled-analysis based on national data from nine high-income countries

BACKGROUND

Possible sex differences in hepatitis A virus (HAV) incidence rates in different age groups are not well documented. We aimed to obtain stable pooled estimates of such differences based on data from a number of high-income countries.

METHODS

We obtained data on incident cases of HAV by sex and age group over a period of 6-25 years from nine countries: Australia, Canada, Czech Republic, Finland, Germany, Israel, Netherland, New Zealand and Spain. Male to female incidence rate ratios (IRR) were computed for each year, by country and age group. For each age group, we used meta-analytic methods to combine the IRRs. Meta-regression was conducted to estimate the effects of age, country, and time period on the IRR.

RESULTS

A male excess in incidence rates was consistently observed in all age groups, although in the youngest and oldest age groups, where the numbers tended to be lower, the lower bounds of the 95% confidence intervals for the IRRs were less than one. In the age groups <1, 1-4, 5-9, 10-14, 15-44, 45-64 and 65+, the pooled IRRs (with 95% CI) over countries and time periods were 1.18 (0.94,1.48), 1.22 (1.16,1.29), 1.07 (1.03,1.11), 1.09 (1.04,1.14), 1.46 (1.30,1.64), 1.32 (1.15,1.51) and 1.10 (0.99,1.23) respectively.

CONCLUSIONS

The excess HAV incidence rates in young males, pooled over a number of countries, suggest that the sex differences are likely to be due at least in part to physiological and biological differences and not just behavioral factors. At older ages, differential exposure plays an important role. These findings, seen in the context of the excess incidence rates in young males for many other infectious diseases, can provide further keys to the mechanisms of the infection.

Macrophage Depletion Reactivates Fecal Virus Shedding following Resolution of Acute Hepatitis A in Ifnar1-/- Mice

Although hepatitis A virus (HAV) is associated only with acute hepatitis in humans, HAV RNA persists within the liver for months following resolution of liver inflammation and cessation of fecal virus shedding in chimpanzees and murine models of hepatitis A. Here, we confirm striking differences in the kinetics of HAV RNA clearance from liver versus serum and feces in infected Ifnar1-/- mice and investigate the nature of viral RNA persisting in the liver following normalization of serum alanine aminotransferase (ALT) levels. Fecal shedding of virus produced in hepatocytes declined >3,000-fold between its peak at day 14 and day 126, whereas intrahepatic HAV RNA declined only 32-fold by day 154. Viral RNA was identified within hepatocytes 3 to 4 months after inoculation and was associated with membranes, banding between 1.07 and 1.14 g/cm3 in isopycnic iodixanol gradients. Gradient fractions containing HAV RNA demonstrated no infectivity when inoculated into naive mice but contained neutralizing anti-HAV antibody. Depleting CD4+ or CD8+ T cells at this late point in infection had no effect on viral RNA abundance in the liver, whereas clodronate-liposome depletion of macrophages between days 110 and 120 postinoculation resulted in a striking recrudescence of fecal virus shedding and the reappearance of viral RNA in serum coupled with reductions in intra-hepatic Ifnγ, Tnfα, Ccl5, and other chemokine transcripts. Our data suggest that replication-competent HAV RNA persists for months within the liver in the presence of neutralizing antibody following resolution of acute hepatitis in Ifnar1-/- mice and that macrophages play a key role in viral control late in infection. IMPORTANCE HAV RNA persists in the liver of infected chimpanzees and interferon receptor-deficient Ifnar1-/- mice for many months after neutralizing antibodies appear, virus has been cleared from the blood, and fecal virus shedding has terminated. Here, we show this viral RNA is located within hepatocytes and that the depletion of macrophages months after the resolution of hepatic inflammation restores fecal virus shedding and circulating viral RNA. Our study identifies an important role for macrophages in virus control following resolution of acute hepatitis A in Ifnar1-/- mice and may have relevance to relapsing hepatitis A in humans.

T cells protect against hepatitis A virus infection and limit infection-induced liver injury

BACKGROUND & AIMS

Hepatitis A virus (HAV) is a common cause of enterically transmitted viral hepatitis. In non-immune individuals, infection results in typically transient but occasionally fulminant and fatal inflammatory liver injury. Virus-specific T cell frequencies peak when liver damage is at its zenith, leading to the prevalent notion that T cells exacerbate liver disease, as suspected for other hepatotropic virus infections. However, the overall contribution of T cells to the control of HAV and the pathogenesis of hepatitis A is unclear and has been impeded by a historic lack of small animal models.

METHODS

Ifnar1^-/- mice are highly permissive for HAV and develop pathogenesis that recapitulates many features of hepatitis A. Using this model, we identified HAV-specific CD8+ and CD4+ T cells by epitope mapping, and then used tetramers and functional assays to quantify T cells in the liver at multiple times after infection. We assessed the relationships between HAV-specific T cell frequency, viral RNA amounts, and liver pathogenesis.

RESULTS

A large population of virus-specific T cells accumulated within the livers of Ifnar1^-/- mice during the first 1-2 weeks of infection and persisted over time. HAV replication was enhanced and liver disease exacerbated when mice were depleted of T cells. Conversely, immunization with a peptide vaccine increased virus-specific CD8+ T cell frequencies in the liver, reduced viral RNA abundance, and lessened liver injury.

CONCLUSION

These data show that T cells protect against HAV-mediated liver injury and can be targeted to improve liver health.

LAY SUMMARY

Hepatitis A virus is a leading cause of acute viral hepatitis worldwide. T cells were thought to contribute to liver injury during acute infection. We now show that virus-specific T cells protect against infection and limit liver injury.

Prolonged Gut Dysbiosis and Fecal Excretion of Hepatitis A Virus in Patients Infected with Human Immunodeficiency Virus

Hepatitis A virus (HAV) causes transient acute infection, and little is known of viral shedding via the duodenum and into the intestinal environment, including the gut microbiome, from the period of infection until after the recovery of symptoms. Therefore, in this study, we aimed to comprehensively observe the amount of virus excreted into the intestinal tract, the changes in the intestinal microbiome, and the level of inflammation during the healing process. We used blood and stool specimens from patients with human immunodeficiency virus who were infected with HAV during the HAV outbreak in Japan in 2018. Moreover, we observed changes in fecal HAV RNA and quantified the plasma cytokine level and gut microbiome by 16S rRNA analysis from clinical onset to at least 6 months after healing. HAV was detected from clinical onset up to a period of more than 150 days. Immediately after infection, many pro-inflammatory cytokines were elicited, and some cytokines showed different behaviors. The intestinal microbiome changed significantly after infection (dysbiosis), and the dysbiosis continued for a long time after healing. These observations suggest that the immunocompromised state is associated with prolonged viral shedding into the intestinal tract and delayed recovery of the intestinal environment.

IRF3-mediated pathogenicity in a murine model of human hepatitis A

HAV-infected Ifnar1^-/- mice recapitulate many of the cardinal features of hepatitis A in humans, including serum alanine aminotransferase (ALT) elevation, hepatocellular apoptosis, and liver inflammation. Previous studies implicate MAVS-IRF3 signaling in pathogenesis, but leave unresolved the role of IRF3-mediated transcription versus the non-transcriptional, pro-apoptotic activity of ubiquitylated IRF3. Here, we compare the intrahepatic transcriptomes of infected versus naïve Mavs^-/- and Ifnar1^-/- mice using high-throughput sequencing, and identify IRF3-mediated transcriptional responses associated with hepatocyte apoptosis and liver inflammation. Infection was transcriptionally silent in Mavs^-/- mice, in which HAV replicates robustly within the liver without inducing inflammation or hepatocellular apoptosis. By contrast, infection resulted in the upregulation of hundreds of genes in Ifnar1^-/- mice that develop acute hepatitis closely modeling human disease. Upregulated genes included pattern recognition receptors, interferons, chemokines, cytokines and other interferon-stimulated genes. Compared with Ifnar1^-/- mice, HAV-induced inflammation was markedly attenuated and there were few apoptotic hepatocytes in livers of infected Irf3^S1/S1Ifnar1^-/- mice in which IRF3 is transcriptionally-inactive due to alanine substitutions at Ser-388 and Ser-390. Although transcriptome profiling revealed remarkably similar sets of genes induced in Irf3^S1/S1Ifnar1^-/- and Ifnar1^-/- mice, a subset of genes was differentially expressed in relation to the severity of the liver injury. Prominent among these were both type 1 and type III interferons and interferon-responsive genes associated previously with apoptosis, including multiple members of the ISG12 and 2’-5’ oligoadenylate synthetase families. Ifnl3 and Ifnl2 transcript abundance correlated strongly with disease severity, but mice with dual type 1 and type III interferon receptor deficiency remained fully susceptible to liver injury. Collectively, our data show that IRF3-mediated transcription is required for HAV-induced liver injury in mice and identify key IRF3-responsive genes associated with pathogenicity, providing a clear distinction from the transcription-independent role of IRF3 in liver injury following binge exposure to alcohol.

Hepatitis A is a common and potentially serious disease involving inflammation and liver cell death resulting from infection with the picornavirus, hepatitis A virus (HAV). The pathogenesis of the disease is incompletely understood. Here, we have profiled changes in the RNA transcriptome of livers from mice with various genetic deficiencies in the innate immune response to HAV. We show that the liver injury associated with HAV infection in these mice results from the induction of genes under transcriptional control of interferon regulatory factor 3 (IRF3). We use high-throughput RNA sequencing to identify sets of genes induced in mice with wild-type versus transcriptionally-incompetent IRF3, rule out roles for type III interferons and IFIT proteins in disease pathogenesis, and identify genes with intrahepatic expression correlating closely with HAV-mediated liver pathology.

Mechanisms of Hepatocellular Injury in Hepatitis A

Hepatitis A virus (HAV) infection is a common cause of acute viral hepatitis worldwide. Despite decades of research, the pathogenic mechanisms of hepatitis A remain incompletely understood. As the replication of HAV is noncytopathic in vitro, a widely accepted concept has been that virus-specific cytotoxic T cells are responsible for liver injury. However, accumulating evidence suggests that natural killer (NK) cells, NKT cells, and even non-HAV-specific CD8⁺ T cells contribute to liver damage during HAV infection. In addition, intrinsic death of virus-infected hepatocytes has been implicated as a cause of liver injury in a murine model of hepatitis A. Furthermore, genetic variations in host factors such as T cell immunoglobulin-1 (TIM1) and IL-18 binding protein (IL-18BP) have been linked to hepatitis A severity. This review summarizes the current knowledge of the mechanisms of hepatocellular injury in hepatitis A. Different mechanisms may be involved under different conditions and they are not necessarily mutually exclusive. A better understanding of these mechanisms would aid in diagnosis and treatment of diseases associated with HAV infection.

The Serum Mac-2-binding Protein Glycosylation Isomer Dynamics in Acute Liver Injury

Objective We aimed to examine the dynamics of serum Wisteria floribunda agglutinin-positive human Mac-2-binding protein glycosylation isomer (M2BPGi) in patients with acute liver injury. Methods Serum M2BPGi levels at the time of the diagnosis (n=77) and normalization of the serum alanine aminotransferase (ALT) level (n=26) were examined retrospectively. The difference in the serum M2BPGi level according to the etiology, and the correlations with other laboratory parameters were evaluated. Results The serum M2BPGi level at the time of the diagnosis was increased in 59 of 77 patients [2.3 cutoff index (COI); range, 0.31-11.1 COI] and was significantly decreased at the time of serum ALT normalization (0.68 COI; range, 0.15-1.87 COI; p<0.0001). The serum M2BPGi level was positively correlated with the duration for which serum ALT normalization was achieved (n=46, Spearman rho=0.53, p<0.0001). A multivariate analysis identified total bilirubin (T-bil), albumin, ALT, alkaline phosphatase, and etiology (e.g., drug-induced liver injury or etiology unknown) as independent factors for increased serum M2BPGi. In patients with infectious mononucleosis, the serum M2BPGi level was higher relative to the degree of increase of serum ALT or T-bil levels in comparison to other etiologies. Conclusion The serum M2BPGi level in patients with acute liver injury reflects the magnitude and duration of liver injury. However, it should be noted that the degree of increase of serum M2BPGi in patients with acute liver injury may differ according to the etiology.

Hepatitis A in a human immunodeficiency virus-infected patient: Impending risk during the Tokyo Olympic Games in 2020

Acute hepatitis A is caused by hepatitis A virus (HAV), which spreads through contaminated food or water or person-to-person contact, and has been epidemic among men who have sex with men (MSM) since 2018 in Tokyo. The majority of these patients have been found to be seropositive for human immunodeficiency virus (HIV) and contracted hepatitis A through sexual contact. We cared for an HIV-positive patient with fulminant hepatitis A while on antiretroviral therapy at our hospital. Hepatitis A vaccine should be aggressively promoted for HIV-positive MSM.

Hepatitis A immunisation in persons not previously exposed to hepatitis A

This review is withdrawn because it is outdated. A new review is to be published by the end of 2019.

Less Severe but Prolonged Course of Acute Hepatitis A in Human Immunodeficiency Virus (HIV)-Infected Patients Compared With HIV-Uninfected Patients During an Outbreak: A Multicenter Observational Study

Background

This multicenter retrospective cohort study aimed to compare the clinical presentations and evolution of acute hepatitis A (AHA) between human immunodeficiency virus (HIV)-infected patients and HIV-uninfected counterparts during the AHA outbreak.

Methods

Clinical and laboratory data were collected from the medical records of the patients with AHA at the 14 hospitals around Taiwan between May 2015 and May 2017.

Results

A total of 297 adult patients with AHA were included during the study period. Their mean age was 31.4 years (range, 19.0-76.1 years); 93.4% were men and 58.6% were men who have sex with men. Of 265 patients with known HIV serostatus, 166 (62.6%) were HIV infected. Compared with HIV-uninfected patients, HIV-infected patients had a lower peak alanine aminotransferase (ALT) level (median, 1312 vs 2014 IU/L, P = .003), less coagulopathy (6.0% vs 16.2%, P = .007), and less hepatomegaly or splenomegaly on imaging studies, but a higher rate of delayed resolution of hepatitis (38.8% vs 21.3%, P = .009). HIV-infected patients with plasma RNA load <1000 copies/mL while receiving combination antiretroviral therapy (cART) had a higher peak ALT level (median, 1420 vs 978 IU/L, P = .006) and less delay in resolution of hepatitis (30.6% vs 48.8%, P = .047) than patients without cART or with plasma RNA load ≥1000 copies/mL.

Conclusions

During an AHA outbreak, HIV-infected patients had a lower severity, but delayed resolution, of AHA than HIV-uninfected patients. Better viral suppression by cART alleviated the impact of HIV infection on the disease course of AHA in HIV-infected patients.

Adaptive Immune Responses in Hepatitis A Virus and Hepatitis E Virus Infections

Both hepatitis A virus (HAV) and hepatitis E virus (HEV) cause self-limited infections in humans that are preventable by vaccination. Progress in characterizing adaptive immune responses against these enteric hepatitis viruses, and how they contribute to resolution of infection or liver injury, has therefore remained largely frozen for the past two decades. How HAV and HEV infections are so effectively controlled by B- and T-cell immunity, and why they do not have the same propensity to persist as HBV and HCV infections, cannot yet be adequately explained. The objective of this review is to summarize our understanding of the relationship between patterns of virus replication, adaptive immune responses, and acute liver injury in HAV and HEV infections. Gaps in knowledge, and recent studies that challenge long-held concepts of how antibodies and T cells contribute to control and pathogenesis of HAV and HEV infections, are highlighted.

Natural History, Clinical Manifestations, and Pathogenesis of Hepatitis A

Hepatitis A virus (HAV) is transmitted by the fecal-oral route and is a major cause of acute viral hepatitis. The clinical manifestations of HAV infection range from asymptomatic infection to acute liver failure (ALF), but do not include progression to chronic hepatitis. Risk factors for severe acute hepatitis A are older age (>40 years) and preexisting liver disease. Some patients may show atypical clinical features such as relapsing hepatitis, prolonged cholestasis, or extrahepatic manifestations. Almost all hepatitis A patients spontaneously recover with supportive care. However, in the case of ALF (<1%), intensive care and urgent decision on liver transplantation are required. Liver injury during hepatitis A is not directly caused by HAV but is known to be caused by immune-mediated mechanisms. In this review, the natural history and clinical manifestations of hepatitis A are described. In addition, mechanisms of immunopathogenesis in hepatitis A are discussed.

Atypical manifestations of hepatitis A virus infection

Acute hepatitis due to the hepatitis A virus usually has a short, benign and self-limited course, without causing chronic hepatitis. However, some cases have an atypical presentation, such as relapsing hepatitis, prolonged or persistent cholestasis, fulminant hepatic failure, or liver failure associated with autoimmune hepatitis. The typical clinical course of acute hepatitis A virus infection is spontaneous remission in 90% of the cases, but atypical cases have a prevalence that varies from less than 1 to 20%, depending on the manifestation (overall prevalence ∼7%). There is little information on the atypical clinical courses of hepatitis A virus infection and the lack of recognizing those presentations in clinical practice often results in carrying out numerous studies and treatments that not only are unnecessary, but can also be harmful. The aim of the present article was to describe 3 clinical cases of atypical hepatitis A infection and provide a literature review of such cases.

Type A viral hepatitis: A summary and update on the molecular virology, epidemiology, pathogenesis and prevention

Although epidemic jaundice was well known to physicians of antiquity, it is only in recent years that medical science has begun to unravel the origins of hepatitis A virus (HAV) and the unique pathobiology underlying acute hepatitis A in humans. Improvements in sanitation and the successful development of highly efficacious vaccines have markedly reduced the worldwide prevalence and incidence of this enterically-transmitted infection over the past quarter century, yet the virus persists in vulnerable populations and remains a common cause of food-borne disease outbreaks in economically-advantaged societies. Reductions in the prevalence of HAV have led to increases in the median age at which infection occurs, often resulting in more severe disease in affected persons and paradoxical increases in disease burden in some developing nations. Here, we summarize recent advances in the molecular virology of HAV, an atypical member of the Picornaviridae family, survey what is known of the pathogenesis of hepatitis A in humans and the host-pathogen interactions that typify the infection, and review medical and public health aspects of immunisation and disease prevention.

Toxicant-Induced Hepatic Injury

The sudden failure of a previously healthy and functioning liver is a dramatic and devastating event. Acute liver failure is the common final pathway of a multitude of conditions and insults, all of which result in massive hepatic necrosis or loss of normal hepatic function. The ensuing multiorgan system failure frequently has a fatal outcome, with mortality rates in most series ranging from approximately 55% to 95% [1]. Acute liver failure (ALF, previously often referred to as fulminant hepatic failure (FHF)) knows no age boundaries, with many cases occurring in those younger than 30 years. Short of excellent intensive care unit (ICU) support and liver transplantation in selected cases, few viable treatment options are available. Over the past few decades, however, survival has been improved by anticipation, recognition, and early treatment of associated complications, as well as the application of prognostic criteria for early identification of patients requiring liver transplantation (along with improvement in the techniques and science of transplantation itself). The etiology of ALF varies from country to country and the incidence change over time. Paracetamol (acetaminophen) has now replaced viral hepatitis as the leading cause of ALF [2]. In a study from London including 310 patients with ALF in the period 1994–2004, 42% of the cases were caused by paracetamol [3], whereas this was only the cause in 2% of 267 patients in Spain from 1992 to 2000 [4]. However, less than 10% of all liver transplants are performed in patients with ALF [5, 6].

Does chronic hepatitis B infection affect the clinical course of acute hepatitis A?

The impact of chronic hepatitis B on the clinical outcome of acute hepatitis A remains controversial. The aim of present study was to evaluate the clinical characteristics of acute hepatitis A in cases with underlying chronic hepatitis B compared to cases of acute hepatitis A alone. Data on 758 patients with acute hepatitis A admitted at two university-affiliated hospitals were reviewed. Patients were classified into three groups: group A, patients with both acute hepatitis A and underlying chronic hepatitis B (n = 27); group B, patients infected by acute hepatitis A alone whose sexes and ages were matched with patients in group A (n  = 54); and group C, patients with acute hepatitis A alone (n = 731). None of the demographic features of group A were significantly different from those of group B or C, except for the proportion of males and body weight, which differed from group C. When comparing to group B, clinical symptoms were more frequent, and higher total bilirubin and lower albumin levels were observed in group A. When comparing to group C, the albumin levels were lower in group A. There were no differences in the duration of hospital stay, occurrence of acute kidney injury, acute liver failure, prolonged cholestasis, or relapsing hepatitis. This study revealed that clinical symptoms and laboratory findings were less favorable for patients with acute hepatitis A and chronic hepatitis B compared to those with acute hepatitis A alone. However, there were no differences in fatal outcomes or serious complications.

Hepatitis A immunisation in persons not previously exposed to hepatitis A

BACKGROUND

In many parts of the world, hepatitis A infection represents a significant cause of morbidity and socio-economic loss. Whilst hepatitis A vaccines have the potential to prevent disease, the degree of protection afforded against clinical outcomes and within different populations remains uncertain. There are two types of hepatitis A virus (HAV) vaccine, inactivated and live attenuated. It is important to determine the efficacy and safety for both vaccine types.

OBJECTIVES

To determine the clinical protective efficacy, sero-protective efficacy, and safety and harms of hepatitis A vaccination in persons not previously exposed to hepatitis A.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, The Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library, MEDLINE, EMBASE, Science Citation Index Expanded, and China National Knowledge Infrastructure (CNKI) up to November 2011.

SELECTION CRITERIA

Randomised clinical trials comparing HAV vaccine with placebo, no intervention, or appropriate control vaccines in participants of all ages.

DATA COLLECTION AND ANALYSIS

Data extraction and risk of bias assessment were undertaken by two authors and verified by a third author. Where required, authors contacted investigators to obtain missing data. The primary outcome was the occurrence of clinically apparent hepatitis A (infectious hepatitis). The secondary outcomes were lack of sero-protective anti-HAV immunoglobulin G (IgG), and number and types of adverse events. Results were presented as relative risks (RR) with 95% confidence intervals (CI). Dichotomous outcomes were reported as risk ratio (RR) with 95% confidence interval (CI), using intention-to-treat analysis. We conducted assessment of risk of bias to evaluate the risk of systematic errors (bias) and trial sequential analyses to estimate the risk of random errors (the play of chance).

MAIN RESULTS

We included a total of 11 clinical studies, of which only three were considered to have low risk of bias; two were quasi-randomised studies in which we only addressed harms. Nine randomised trials with 732,380 participants addressed the primary outcome of clinically confirmed hepatitis A. Of these, four trials assessed the inactivated hepatitis A vaccine (41,690 participants) and five trials assessed the live attenuated hepatitis A vaccine (690,690 participants). In the three randomised trials with low risk of bias (all assessing inactivated vaccine), clinically apparent hepatitis A occurred in 9/20,684 (0.04%) versus 92/20,746 (0.44%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.03 to 0.30). In all nine randomised trials, clinically apparent hepatitis A occurred in 31/375,726 (0.01%) versus 505/356,654 (0.18%) participants in the HAV vaccine and control groups respectively (RR 0.09, 95% CI 0.05 to 0.17). These results were supported by trial sequential analyses. Subgroup analyses confirmed the clinical effectiveness of both inactivated hepatitis A vaccines (RR 0.09, 95% CI 0.03 to 0.30) and live attenuated hepatitis A vaccines (RR 0.07, 95% CI 0.03 to 0.17) on clinically confirmed hepatitis A. Inactivated hepatitis A vaccines had a significant effect on reducing the lack of sero-protection (less than 20 mIU/L) (RR 0.01, 95% CI 0.00 to 0.03). No trial reported on a sero-protective threshold less than 10 mIU/L. The risk of both non-serious local and systemic adverse events was comparable to placebo for the inactivated HAV vaccines. There were insufficient data to draw conclusions on adverse events for the live attenuated HAV vaccine.

AUTHORS' CONCLUSIONS

Hepatitis A vaccines are effective for pre-exposure prophylaxis of hepatitis A in susceptible individuals. This review demonstrated significant protection for at least two years with the inactivated HAV vaccine and at least five years with the live attenuated HAV vaccine. There was evidence to support the safety of the inactivated hepatitis A vaccine. More high quality evidence is required to determine the safety of live attenuated vaccines.

Dominance of the CD4(+) T helper cell response during acute resolving hepatitis A virus infection

Hepatitis A virus (HAV) infection typically resolves within 4-7 wk but symptomatic relapse occurs in up to 20% of cases. Immune mechanisms that terminate acute HAV infection, and prevent a relapse of virus replication and liver disease, are unknown. Here, patterns of T cell immunity, virus replication, and hepatocellular injury were studied in two HAV-infected chimpanzees. HAV-specific CD8(+) T cells were either not detected in the blood or failed to display effector function until after viremia and hepatitis began to subside. The function of CD8(+) T cells improved slowly as the cells acquired a memory phenotype but was largely restricted to production of IFN-γ. In contrast, CD4(+) T cells produced multiple cytokines when viremia first declined. Moreover, only CD4(+) T cells responded during a transient resurgence of fecal HAV shedding. This helper response then contracted slowly over several months as HAV genomes were eliminated from liver. The findings indicate a dominant role for CD4(+) T cells in the termination of HAV infection and, possibly, surveillance of an intrahepatic reservoir of HAV genomes that decays slowly. Rapid contraction or failure to sustain such a CD4(+) T cell response after resolution of symptoms could increase the risk of relapsing hepatitis A.

Innate and adaptive immune responses against picornaviruses and their counteractions: An overview

Picornaviruses, small positive-stranded RNA viruses, cause a wide range of diseases which is based on their differential tissue and cell type tropisms. This diversity is reflected by the immune responses, both innate and adaptive, induced after infection, and the subsequent interactions of the viruses with the immune system. The defense mechanisms of the host and the countermeasures of the virus significantly contribute to the pathogenesis of the infections. Important human pathogens are poliovirus, coxsackievirus, human rhinovirus and hepatitis A virus. These viruses are the best-studied members of the family, and in this review we want to present the major aspects of the reciprocal effects between the immune system and these viruses.

The role of immunoglobulin A in prolonged and relapsing hepatitis A virus infections

Hepatitis A virus (HAV) infections result in different courses of the disease, varying between normal, prolonged and relapsing. However, the reason for these heterogeneous clinical appearances is not understood. As HAV-anti-HAV IgA immunocomplexes (HAV-IgA) infect hepatocytes, IgA was postulated as a carrier supporting hepatotropic transport of HAV, and it was speculated that this carrier mechanism contributes to the various clinical outcomes. In this study, the IgA-carrier mechanism was investigated in a mouse model. We show that HAV-IgA immunocomplexes efficiently reached the liver not only in HAV-seronegative mice, but also, and this is in contrast to free-HAV particles, in immunized HAV-seropositive animals. This IgA-mediated transport of HAV to the liver in the presence of immunity depended on the stage of development of the immune response. We conclude that over a period of several weeks after infection, anti-HAV IgA is able to promote an enterohepatic cycling of HAV, resulting in continuous endogenous reinfections of the liver. Our experiments indicate that highly avid IgG antibodies, which are present at later times of the infection, can terminate the reinfections. However, the endogenous reinfections in the presence of a developing neutralizing immunity might contribute to prolonged as well as to relapsing courses of HAV infections. Furthermore, the results show that serum IgA may act as an infection protracting factor.

Comparison of the Clinical Features of Hepatitis A between HBsAg-Positive and HBsAg-Negative Patients

BACKGROUND/AIMS

The notion that acute hepatitis A superimposed on chronic hepatitis B infection leads to a worse outcome than acute hepatitis A alone remains controversial. The aim of this study was to determine the influence of the presence of hepatitis B surface antigen (HBsAg) on the severity of acute hepatitis A.

METHODS

We retrospectively analyzed 449 patients hospitalized for acute hepatitis A from January 2000 to February 2010 and compared clinical outcomes based on the presence of HBsAg.

RESULTS

Of the 449 patients, 30 patients were in the HBsAg-positive group and 419 in the HBsAg-negative group. The HBsAg-positive group was older than the HBsAg-negative group (36.1±8.3 vs 31.8±8.5 years, p=0.004); however, other baseline characteristics were similar between the 2 groups. Mean peak values of prothrombin time, serum total bilirubin, and serum creatinine at admission were significantly higher in the HBsAg-positive group. When comparing clinical outcomes between the 2 groups, gastrointestinal bleeding, acute renal failure, and acute liver failure were more frequently observed in the HBsAg-positive group. In particular, the incidence of acute liver failure was approximately 9-fold higher in the HBsAg-positive group than in the HBsAg-negative group (23.3% vs 3.3%; odds ratio [OR], 8.80; p<0.001). Multivariate analysis showed that HBsAg (OR, 7.43; 95% confidence interval [CI], 2.56 to 21.57) and age (OR, 1.07; 95% CI, 1.02 to 1.13) were independent risk factors for the occurrence of acute liver failure.

CONCLUSIONS

In patients with chronic hepatitis B infection, acute hepatitis A is associated with more severe clinical outcomes, including acute liver failure, compared with patients with acute hepatitis A alone.

[A case of autoimmune hepatitis following acute hepatitis A]

The pathogenesis of autoimmune hepatitis (AIH) is unclear, but viral infections have been proposed as a potential trigger in patients with genetic predisposition. We report a case of AIH following acute hepatitis A (AHA). A 57-year-old woman presented with fatigue and pitting edema for last 3 months. She had been diagnosed as an AHA 15 months ago based on clinical features, biochemical tests and positive HAV IgM antibody at a local clinic. Her biochemical tests was normalized one month after AHA diagnosis, but the serum levels of aminotransferase started to rise four months after AHA diagnosis. Antinuclear antibody was positive at a titer of 1:40, and anti-smooth muscle antibody was also positive. Hypergammaglobulinemia and liver pathology were typical for AIH. The patients had a score of 17 according to the International Autoimmune Hepatitis Group's system. She was given prednisolone and azathioprine and showed complete response to immunosuppressive therapy. The present case is the first report on AIH triggered by AHA in Korea.

A polymorphism in TIM1 is associated with susceptibility to severe hepatitis A virus infection in humans

During infection with the hepatitis A virus (HAV), most patients develop mild or asymptomatic disease. However, a small number of patients develop serious, life-threatening hepatitis. We investigated this variability in disease severity by examining 30 Argentinean patients with HAV-induced acute liver failure in a case-control, cross-sectional, observational study. We found that HAV-induced severe liver disease was associated with a 6-amino-acid insertion in TIM1/HAVCR1 (157insMTTTVP), the gene encoding the HAV receptor. This polymorphism was previously shown to be associated with protection against asthma and allergic diseases and with HIV progression. In binding assays, the TIM-1 protein containing the 157insMTTTVP insertion polymorphism bound HAV more efficiently. When expressed by human natural killer T (NKT) cells, this long form resulted in greater NKT cell cytolytic activity against HAV-infected liver cells, compared with the shorter TIM-1 protein without the polymorphism. To our knowledge, the 157insMTTTVP polymorphism in TIM1 is the first genetic susceptibility factor shown to predispose to HAV-induced acute liver failure. Furthermore, these results suggest that HAV infection has driven the natural selection of shorter forms of the TIM-1 protein, which binds HAV less efficiently, thereby protecting against severe HAV-induced disease, but which may predispose toward inflammation associated with asthma and allergy.

Characterization of CD8+ T-cell response in acute and resolved hepatitis A virus infection

BACKGROUND & AIMS

In contrast to the infection with other hepatotropic viruses, hepatitis A virus (HAV) always causes acute self-limited hepatitis, although the role for virus-specific CD8 T cells in viral containment is unclear. Herein, we analyzed the T cell response in patients with acute hepatitis by utilizing a set of overlapping peptides and predicted HLA-A2 binders from the polyprotein.

METHODS

A set of 11 predicted peptides from the HAV polyprotein, identified as potential binders, were synthesized. Peripheral blood mononuclear cells (PBMCs) from patients were tested for IFNγ secretion after stimulation with these peptides and ex vivo with HLA-A2 tetramers. Phenotyping was carried out by staining with the activation marker CD38 and the memory marker CD127.

RESULTS

Eight out of 11 predicted HLA-A2 binders showed a high binding affinity and five of them were recognized by CD8+ T cells from patients with hepatitis A. There were significant differences in the magnitude of the responses to these five peptides. One was reproducibly immunodominant and the only one detectable ex vivo by tetramer staining of CD8+ T cells. These cells have an activated phenotype (CD38hi CD127lo) during acute infection. Three additional epitopes were identified in HLA-A2 negative patients, most likely representing epitopes restricted by other HLA-class I-alleles (HLA-A11, B35, B40).

CONCLUSIONS

Patients with acute hepatitis A have a strong multi-specific T cell response detected by ICS. With the tetramer carrying the dominant HLA-A2 epitope, HAV-specific and activated CD8+ T cells could be detected ex vivo. This first description of the HAV specific CTL-epitopes will allow future studies on strength, breadth, and kinetics of the T-cell response in hepatitis A.

Concurrent reactivation of latent EBV with hepatitis A can affect clinical feature of childhood hepatitis

AIMS

Some children with acute hepatitis A virus (HAV) infection have concurrent Epstein-Barr virus (EBV) reactivation serologically. We studied the frequency of EBV reactivation during HAV infection and determined whether simultaneous occurrence of EBV reactivation and HAV infection affected the clinical features of HAV infection.

METHODS

The medical records of patients under 19 years of age diagnosed with acute hepatitis A between January 1996 and June 2009 were reviewed.

RESULTS

Among 72 patients with acute hepatitis A, 22 patients (30.6%) had EBV reactivation. A markedly prolonged duration of full recovery from hepatitis was observed in reactivated group. The peak levels of AST and ALT in reactivated group were higher than non-reactivated group (p = 0.012 and p < 0.001, respectively). Higher peak levels of AST and ALT in reactivated subgroups over 10 years old were observed compared to non-reactivated subgroup (p = 0.027 and p = 0.001, respectively). Duration of recovery showed significant differences between two subgroups.

CONCLUSIONS

Concurrent reactivation of latent EBV and HAV infections is common. EBV reactivation with HAV infection adversely affects the clinical feature of hepatitis. Therefore, we should keep in mind that the concurrence especially in older children may cause worse injury to the liver.

Nucleotide variability and translation efficiency of the 5' untranslated region of hepatitis A virus: update from clinical isolates associated with mild and severe hepatitis

Mutations in the internal ribosome entry site (IRES) of hepatitis A virus (HAV) have been associated with enhanced in vitro replication and viral attenuation in animal models. To address the possible role of IRES variability in clinical presentation, IRES sequences were obtained from HAV isolates associated with benign (n = 8) or severe (n = 4) hepatitis. IRES activity was assessed using a bicistronic dual-luciferase expression system in adenocarcinoma (HeLa) and hepatoma (HuH7) cell lines. Activity was higher in HuH7 than in HeLa cells, except for an infrequently isolated genotype IIA strain. Though globally low, significant variation in IRES-dependent translation efficiency was observed between field isolates, reflecting the low but significant genetic variability of this region (94.2% +/- 0.5% nucleotide identity). No mutation was exclusive of benign or severe hepatitis, and variations in IRES activity were not associated with a clinical phenotype, indirectly supporting the preponderance of host factors in determining the clinical presentation.

Hepatitis A virus: serology and molecular diagnostics

The diagnosis of hepatitis A virus (HAV) infection is based on the detection of anti-HAV IgM. Shortcomings of this serological approach include the persistence of IgM after normalization of liver enzymes or its detection during polyclonal activation of the immune system due to unrelated viral infection or autoimmune diseases. Molecular diagnosis of HAV along with anti-HAV IgG avidity measurement are helpful in case of positive IgM where laboratory evidence of acute hepatitis is absent and there is no epidemiologic link to other cases. Molecular epidemiology allows us to determine whether viruses from different locations are related to each other and provides further understanding of viral epidemiology by identifying sources and transmission modes. It has been demonstrated that the rapid turnover of HAV strains in low-endemicity countries is caused by their introduction by travelers. Growing sequence databases allow for the identification of geographic origin of viral strains. Collaboration between surveillance laboratories, including database sharing, should be promoted for deeper investigation of outbreaks and improved prevention approaches.

The regulatory T-cell response during acute retroviral infection is locally defined and controls the magnitude and duration of the virus-specific cytotoxic T-cell response

Cytotoxic CD8(+) T cells control acute viremia in many viral infections. However, most viruses that establish chronic infections evade destruction by CD8(+) T cells, and regulatory T cells (Treg) are thought to be involved in this immune evasion. We have infected transgenic mice, in which Treg can be selectively depleted, with Friend retrovirus (FV) to investigate the influence of Treg on pathogen-specific CD8(+) T-cell responses in vivo. We observed that Treg expansion during acute infection was locally defined to organs with high viral loads and massive activation of virus-specific effector CD8(+) T cells. Experimental ablation of Treg resulted in a significant increase of peak cytotoxic CD8(+) T-cell responses against FV. In addition, it prevented the development of functional exhaustion of CD8(+) T cells and significantly reduced FV loads in lymphatic organs. Surprisingly, despite the massive virus-specific CD8(+) T-cell response after temporary Treg depletion, no evidence of immunopathology was found. These results demonstrate the important role of Treg in controlling acute retrovirus-specific CD8(+) T-cell responses, and suggest that temporary manipulation of Treg might be a possible therapeutic approach in chronic infectious diseases.

Fatal outcome of hepatitis A virus (HAV) infection in a traveler with incomplete HAV vaccination and evidence of Rift Valley Fever virus infection

Hepatitis A virus (HAV) infection is rarely fatal except in patients with chronic liver disease. In the case reported here, an elderly women died of HAV infection 12 years after incomplete HAV vaccination. The possible role of a concordant Rift Valley fever virus infection acquired in Kenya is discussed.

Hepatitis A virus protein 2B suppresses beta interferon (IFN) gene transcription by interfering with IFN regulatory factor 3 activation

Hepatitis A virus (HAV) antagonizes the innate immune response by inhibition of retinoic acid-inducible gene I-mediated and melanoma differentiation-associated gene 5-mediated beta interferon (IFN-beta) gene expression. This study showed that this is due to an interaction of HAV with mitochondrial antiviral signalling protein (MAVS)-dependent signalling, in which the viral non-structural protein 2B and the protein intermediate 3ABC recently suggested in this context seem to be involved, cooperatively affecting the activities of MAVS and the kinases TANK-binding kinase 1 (TBK1) and the inhibitor of NF-kappaB kinase epsilon (IKKepsilon). In consequence, interferon regulatory factor 3 (IRF-3) is not activated. As IRF-3 is necessary for IFN-beta transcription, inhibition of this factor results in efficient suppression of IFN-beta synthesis. This ability might be of vital importance for HAV, which is an exceptionally slow growing virus sensitive to IFN-beta, as it allows the virus to establish infection and maintain virus replication for a longer period of time.

Experiences with acute kidney injury complicating non-fulminant hepatitis A

AIM

To describe the clinical features and to identify factors related to development of acute kidney injury in acute hepatitis A patients.

METHODS

The study and control groups consisted of 21 and 425 patients who did or did not develop acute kidney injury, respectively, after acute hepatitis A from January 1997 to May 2007.

RESULTS

There were 13 men and eight women; their mean age at diagnosis was 28.8 +/- 8.2 years in the study group. Peak values for renal and liver function impairment consisted of a median serum creatinine of 4.6 mg/dL (range, 1.5-15.3 mg/dL) on day 6 (range, days 1-20) and a median total bilirubin of 10.7 mg/dL (range, 2.6-57.5 mg/dL) on day 8 (range, day 1-19). Serum creatinine concentrations returned to baseline level by a median of 16 days and total bilirubin levels returned to normal by a median of 62 days. Six of 21 (29%) patient underwent haemodialysis. Renal biopsies performed in two patients showed acute tubular necrosis and interstitial nephritis, respectively. Logistic regression analysis showed that a lower haematocrit, the presence of coagulopathy and high C-reactive protein concentration on admission, and higher peak bilirubin value during the illness were associated with development of acute kidney injury.

CONCLUSION

Acute hepatitis A should be considered in the differential diagnosis of patients with acute kidney injury, even without fulminant hepatic failure. A lower haematocrit, the presence of coagulopathy and high C-reactive protein level at presentation, and higher peak bilirubin level during the illness were associated with development of acute kidney injury in acute hepatitis A patients.

Virological course of hepatitis A virus as determined by real time RT-PCR: Correlation with biochemical, immunological and genotypic profiles

AIM: To undertake analysis of hepatitis A viral load, alanine aminotransferase (ALT), and viral genotypes with duration of viremia, and to correlate these parameters with CD4⁺/ CD8⁺ lymphocyte populations that control cell-mediated immunity.

METHODS: Cell counts were carried out using fresh whole blood collected in EDTA vials using a fluorescence activated cell sorter. Hepatitis A virus (HAV) RNA was extracted from blood serum, reverse transcribed into cDNA and quantified by Real-Time polymerase chain reaction and was genotyped.

RESULTS: Among 11 patients, 10 could be analyzed completely. Of these, 3 had severe acute hepatitis (s-AH) and the remainder had a self-limited acute hepatitis A (AHA), with one patient with fulminant disease (encephalopathy Grade IV) dying on the 4^th d. The ALT level was significantly higher both in AHA (1070.9 ± 894.3; P = 0.0014) and s-AH (1713.9 ± 886.3; P = 0.001) compared to normal controls (23.6 ± 7.2). The prothrombin time in s-AH patients (21.0 ± 2.0; P = 0.02) was significantly higher than in AHA (14.3 ± 1.1; P = 0.44). The CD4⁺/CD8⁺ ratio in AHA patients (1.17 ± 0.11; P = 0.22) and s-AH (0.83 ± 0.12; P = 0.0002) were lower than seen in normal healthy controls (1.52). Self-limited cases had peak viral load at the beginning of analysis while in s-AH patients this occurred at the 15^th or 30^th d. In acute and severe groups, one patient each belonged to genotype IA, with the remaining 8 cases belonging to genotype IIIA. The only fulminant hepatic failure case belonged to genotype IA. HAV viral load and ALT values collected during the entire course of the self-limited infection were directly correlated but this was not the case for s-AH patients.

CONCLUSION: Based on a small-scale study, the persistently higher viral load of s-AH might be due to diminished cellular immunity and hemolysis. The duration of viremia was dependent on the host, as the viral genotype had no apparent role in clinical outcome of AVH and s-AH cases.

Cell mediated and antibody immune response to inactivated hepatitis A vaccine

The humoral and cellular immune response to inactivated hepatitis A vaccine was investigated dynamically in a time elapse study over 1 year. Fourty-five healthy volunteers, seronegative for anti-HAV, were vaccinated with 1440 enzyme-linked immunosorbent assay units (EU) of formalin-inactivated hepatitis A virus following a 0--6-month schedule. Serum anti-HAV levels and HAV-specific proliferation of peripheral blood mononuclear cells were measured at several time points over a 26- and 28-week period after the first and second injection, respectively. Distinct B and T cell responses were determined within 14 days after primary vaccination. The booster vaccination-induced immediate peak levels for the humoral (anti-HAV GMC=5376mIU/ml) as well as the cellular (median Deltacpm=14173cpm) response.

Hepatitis A virus suppresses RIG-I-mediated IRF-3 activation to block induction of beta interferon

Hepatitis A virus (HAV) antagonizes the innate immune response by inhibition of double-stranded RNA (dsRNA)-induced beta interferon (IFN-beta) gene expression. In this report, we show that this is due to an interaction of HAV with the intracellular dsRNA-induced retinoic acid-inducible gene I (RIG-I)-mediated signaling pathway upstream of the kinases responsible for interferon regulatory factor 3 (IRF-3) phosphorylation (TBK1 and IKKepsilon). In consequence, IRF-3 is not activated for nuclear translocation and gene induction. In addition, we found that HAV reduces TRIF (TIR domain-containing adaptor inducing IFN-beta)-mediated IRF-3 activation, which is part of the Toll-like receptor 3 signaling pathway. As IRF-3 is necessary for IFN-beta transcription, inhibition of this factor results in efficient suppression of IFN-beta synthesis. This ability of HAV seems to be of considerable importance for HAV replication, as HAV is not resistant to IFN-beta, and it may allow the virus to establish infection and preserve the sites of virus production in later stages of the infection.

Apoptosis induced by a cytopathic hepatitis A virus is dependent on caspase activation following ribosomal RNA degradation but occurs in the absence of 2'-5' oligoadenylate synthetase

We have presented previously evidence that the cytopathogenic 18f strain of hepatitis A virus (HAV) induced degradation of ribosomal RNA (rRNA) in infected cells [Arch. Virol. 148 (2003) 1275–1300]. In contrast, the non-cytopathogenic parent virus HM175 clone 1 had no effect on rRNA integrity. We present here data showing that rRNA degradation is followed by apoptosis accompanied by characteristic DNA laddering in the cytoplasm of 18f infected cells. The DNA laddering coincided with the detection of caspase 3 and PARP-1 cleavage and was dependent upon activation of the caspase pathway, since treatment with Z-VAD-FMK, a pan-caspase inhibitor, inhibited both events. RNase L mRNA was present in both virus-infected and uninfected cells. Messenger RNA for the interferon inducible enzyme 2′–5′ oligoadenylate synthetase (2′–5′ OAS), which polymerizes ATP into 2′–5′ oligo adenylate (2–5A, the activator of RNase L) in the presence of double-stranded RNA, was not detected following virus infection. 2′–5′ OAS mRNA was induced by treatment of the cells with interferon-β (IFN-β). IFN-β mRNA was marginally induced following infection. However, phosphorylated STAT 1, a key regulator of interferon-stimulated gene transcription was not detected in virus infected cells. STAT 1 phosphorylation in response to IFN treatment was lower in virus-infected cells, compared to uninfected cells treated with interferon, suggesting that 18f virus infection interferes with interferon signaling. The results suggest that 18f infection causes the induction of a 2–5A independent RNase L like activity.

Is there a role for viruses in triggering autoimmune hepatitis?

A role for viruses in autoimmune hepatitis (AH) has been repeatedly proposed but convincing evidence links only two viruses, hepatitis A and Epstein-Barr virus, to the type 1 form of the disease, and only in those rare cases where a genetic predisposition exists and the viral infection occurs at the right time, i.e. when other unknown factors are cooperating. In spite of an impressive amount of information conclusively showing molecular mimicry between cytochrome P450IID6 (the target autoantigen of autoantibodies characteristic of AH type 2) sequences and viral (hepatitis C virus, herpes simplex virus 1, cytomegalovirus, human T lymphotropic viruses 1 and 2) or bacterial (Salmonella typhimurium) antigens, no infectious agent is clearly able to induce this second form of the disease. In conclusion, the molecular mimicry theory has so far found little clinical evidence in its support and many more clinical observations are needed in order to unreveal possible links between viruses and AH.

Time course of hepatitis A viremia and viral load in the blood of human hepatitis A patients

The hepatitis A virus (HAV) is the most common etiological cause of acute hepatitis infections in humans in industrialized countries. Investigations into the viral load during HAV viremia, however, are rare. Therefore, correlation studies between viral load, biochemical, and specific serological markers have been undertaken. The group of sera comprised a series of multiple consecutive blood samples drawn from 11 patients at different times after onset of the disease. During the period up to 70 days after the onset of icterus, the individual range was at 1 x 10(3) to 3 x 10(4) HAV genome equivalents/ml. From day 75 until 120 after onset of the disease, the levels traced were at 10(3). In one case, it was possible to trace 1.25 x 10(4) genome equivalents/ml up to 180 days after onset of icterus and in two cases even up to 408 and 490 days viral load levels of 5 x 10(3) and 4 x 10(4) were detected, respectively. The same sera were used to measure IgM class antibodies to hepatitis A virus and the total anti-HAV. The results demonstrate that a direct correlation to peak levels of viral load exists with peak serum transaminase levels, but neither with peak anti-HAV IgM levels nor with total anti-HAV. Decreasing amounts of anti-HAV IgM tend to occur with decreasing amounts of HAV genome equivalents; and, vice versa, increasing amounts of total anti-HAV are accompanied by decreasing amounts of HAV genome equivalents. The longest duration of viremia was found in patients infected with HAV genotype IA.

HAV replication in acute hepatitis with typical and atypical clinical course

The correlation between the length of viremia as detected by reverse transcriptase-polymerase chain reaction (RT-PCR) and the clinical course of hepatitis A virus (HAV) infection was studied. Sixty-six consecutive patients with acute hepatitis A who were admitted to hospital in two infectious disease units in southern Italy were enrolled: 57 had a self-limited course of the disease (typical course), 4 a prolonged course, and 5 relapsing hepatitis. Plasma HAV RNA was sought by RT-PCR, using primers made at 5'-NTR of HAV, designed to amplify a 273-bp fragment and detected by 2% agarose gel and by hybridization with a specific biotinylated probe. In four patients with prolonged acute hepatitis A, the plasma HAV RNA, which was positive on the day of admission to hospital, was found to be negative from day 62, 46, 84, and 105, respectively, after the onset of the symptoms. In patients with relapsing hepatitis, HAV viremia paralleled the clinical and biochemical course of disease. In all patients with a typical self-limiting course, clearance of plasma HAV RNA was observed within 20 days of the onset of symptoms. In most patients, plasma HAV viremia became undetectable before the normalization of serum aminotransferases, underlining the importance of the immune reaction in the pathogenesis of acute hepatitis A. The data also suggest that the detection of plasma HAV RNA after 20 days of illness may predict a prolonged course of the disease, but relapsing hepatitis remains unpredictable on the basis of plasma HAV determination.

Viral and clinical factors associated with the fulminant course of hepatitis A infection

Fulminant hepatitis is a severe complication of hepatitis A virus infection. Its mechanism is unknown. Liver transplantation can be necessary, but spontaneous recovery is frequent. There are no data on the level of viral replication according to the clinical form of hepatitis A. We reviewed the files of 50 patients with acute hepatitis A. Nineteen patients had fulminant hepatitis (defined by encephalopathy and factor V <50%), and, from them, 10 patients underwent transplantation. Hepatitis A virus (HAV) RNA was quantified by real-time PCR on sera obtained at admission. The genotype was determined by phylogenetic analysis of HAV RNA. HAV RNA was detected in serum by RT-PCR in 39 out of 50 patients. Encephalopathy and low factor V level were significantly related to female gender, HAV PCR negativity (9/19 vs. 5/31, respectively; P =.03), a low serum HAV RNA level (log, 3.6 +/- 0.6 vs. 4.4 +/- 0.9, respectively; P =.02), genotypes other than IA, and acetaminophen intake. In multivariate analysis, low or undetectable HAV viral load and a high bilirubin level were independently associated with both low factor V levels and fulminant hepatitis and also with death or transplantation. In conclusion, HAV-related liver failure is due to an excessive host response associated with a marked reduction in viral load. Serum HAV RNA assay could be of help in the management of severe hepatitis A.

Hepatitis A virus inhibits cellular antiviral defense mechanisms induced by double-stranded RNA

The consequences of a hepatitis A virus (HAV) infection on cell-based antiviral responses and the interactions between virus and host cells resulting in persistent infections are poorly understood. In this report, we show that HAV does inhibit double-stranded (dsRNA)-induced beta interferon (IFN-beta) gene expression by influencing the IFN-beta enhanceosome, as well as dsRNA-induced apoptosis, which suggests that both effects may be connected by shared viral and/or cellular factors. This ability of HAV, which preserves the sites of virus production for a longer time, may allow the virus to establish an infection and may be the presupposition for setting up persistent infections. Our results suggest that the inhibitory effect of HAV on the cellular defense mechanisms might not be sufficient to completely prevent the antiviral reactions, which may be induced by accumulating viral dsRNA, at a later stage of infection. However, HAV seems to counteract this situation by downregulation of viral replication and in the following production of viral dsRNA. This ability of noncytopathogenic HAV acts dominantly on cytopathogenic HAV in trans. The downregulation might ensure the moderate replication which seems necessary for inhibition of the antiviral mechanisms by HAV and therefore for the persistent state of the HAV infection.

Influence of human immunodeficiency virus type 1 infection on acute hepatitis A virus infection

To assess the possible influence of human immunodeficiency virus type 1 (HIV-1) infection on the clinical course of acute hepatitis A virus (HAV) infection, 15 HIV-1-infected homosexual men and 15 non-HIV-infected age-matched subjects were compared. HAV load was higher in HIV-1-infected than in non-HIV-infected patients (P<.001). Duration of viremia in HIV-1-infected patients (median, 53 days) was significantly (P<.05) longer than in non-HIV-infected patients (median, 22 days). HIV-1-infected patients had lower elevations in alanine aminotransferase levels than did non-HIV-infected patients (P<.01) but had higher elevations in alkaline phosphatase levels than did non-HIV-infected patients (P<.001). Some HIV-1-infected patients still had HAV viremia when clinical symptoms had disappeared and alanine aminotransferase levels had returned to normal (60-90 days after the onset of symptoms). HIV-1 infection was associated with prolongation of HAV viremia, which might cause a long-lasting outbreak of HAV infection in HIV-1-infected homosexual men.

Experimental hepatitis A virus infection in guinea pigs

Although many of the properties of hepatitis A virus (HAV) are known, several aspects of HAV pathogenesis are still not understood, such as the mechanism underlying the hepatotropism or HAV replication in extrahepatic sites. Detailed studies of these aspects were hampered mostly by the lack of accessible animal models, since only nonhuman primates are susceptible to experimental infections. An alternative animal model would also be of interest to assess the primary replication site and for the evaluation of the safety and efficacy of vaccines. A study was undertaken to determine whether HAV can infect guinea pigs and whether they are useful as a model for studying aspects of HAV pathogenesis and for the evaluation of vaccines. HAV variants adapted to primate or guinea pig tissue culture were used to inoculate guinea pigs intraperitoneally and by the oral route. The animals were observed for clinical disease, shedding of HAV in stools, viremia, seroconversion, evidence for liver damage by biochemical liver function tests, virus presence in the liver, development of hepatic histopathological changes, and occurrence of HAV in extrahepatic organs. The animals developed an active, clinically inapparent infection with specific histopathological changes in the liver. Although virus replication occurred, as shown by RT-PCR and isolation of infectious virus from feces and serum, it seems unlikely that guinea pigs are suitable for studying the clinical features of hepatitis A, because the clinical and laboratory parameters remained normal. However, guinea pigs appear useful for studying some aspects of HAV pathogenesis and for testing the safety of vaccines.

Allogenic bone marrow transplantation with a donor presenting with an acute hepatitis A

We report the unique occurrence of an allogenic bone marrow transplantation performed as the donor was suffering from an acute hepatitis A. The bone marrow was contaminated at the time of collection, as demonstrated by hepatitis A virus (HAV) RNA detected by RT-PCR. Hepatitis A virus infection in such a situation could have resulted in a severe liver disease in the recipient. However, although we could demonstrate that the recipient had been infected, he did not develop a symptomatic hepatitis A but only minor disturbances of liver function tests between days 35 and 55. Both the postponement of the transplantation and the use of intravenous polyvalent immunoglobulins have probably played a key role in decreasing the viral load and allowing a rapid clearance of the virus. A possible role of the grafted immune system might also be envisaged, as suggested by the de novo synthesis of IgM in the recipient.

Suppression of hepatitis B virus replication mediated by hepatitis A-induced cytokine production

BACKGROUND

Acute hepatitis A virus (HAV) infection can cause severe hepatitis especially in patients with underlying chronic liver disease. In patients with pre-existing chronic hepatitis B (HBV) acute HAV infection can suppress HBV replication. The exact mechanism of HBV suppression during acute HAV infection is still a subject of debate. One mechanism may be the production of HAV infection-induced cytokines leading to suppression of HBV replication and viral clearance.

AIM

To evaluate cytokine production and HBV-specific lympho-proliferative responses (LPR) during acute HAV infection in a patient with chronic HBV infection-clearing markers of active HBV replication.

DESIGN

Early detection of a case of acute HAV infection in an HBeAg-positive, HBV DNA-positive chronic HBV patient treated with lamivudine.

RESULTS

At the time of HAV infection a sharp peak in the gamma-interferon (IFN-gamma) level occurred just before the rise in serum transaminase activity. This was subsequently followed by a decrease in HBV DNA and HBeAg below the limit of detection of the assay. However the HBV-specific T-cell response was not modified. After resolution of the acute HAV infection and withdrawal of antiviral therapy HBV replication relapsed.

CONCLUSION

The sharp rise in IFN-gamma production mediated by the acute HAV infection may be pivotal in the suppression of HBV replication in chronic hepatitis B.

Hepatitis A virus-specific immunoglobulin A mediates infection of hepatocytes with hepatitis A virus via the asialoglycoprotein receptor

The mechanisms underlying the hepatotropism of hepatitis A virus (HAV) and the relapsing courses of HAV infections are unknown. In this report, we show for a mouse hepatocyte model that HAV-specific immunoglobulin A (IgA) mediates infection of hepatocytes with HAV via the asialoglycoprotein receptor, which binds and internalizes IgA molecules. Proof of HAV infection was obtained by detection of HAV minus-strand RNA, which is indicative for virus replication, and quantification of infectious virions. We demonstrate that human hepatocytes also ingest HAV-anti-HAV IgA complexes by the same mechanism, resulting in infection of the cells, by using the HepG2 cell line and primary hepatocytes. The relevance of this surrogate receptor mechanism in HAV pathogenesis lies in the fact that HAV, IgA, and antigen-IgA complexes use the same pathway within the organism, leading from the gastrointestinal tract to the liver via blood and back to the gastrointestinal tract via bile fluid. Therefore, HAV-specific IgA antibodies produced by gastrointestinal mucosa-associated lymphoid tissue may serve as carrier and targeting molecules, enabling and supporting HAV infection of IgA receptor-positive hepatocytes and, in the case of relapsing courses, allowing reinfection of the liver in the presence of otherwise neutralizing antibodies, resulting in exacerbation of liver disease.

Hepatitis A

Hepatitis A remains an important cause of community-acquired hepatitis in the United States and in the world. In recent years, improvements in personal hygiene and environmental sanitation have led to declines in overall hepatitis A infection rates in developed countries, although sporadic outbreaks still occur with similar rates of hospitalization and loss of work. Therapy remains supportive and prevention holds the key to elimination of widespread infection. Acute infection can be prevented or attenuated with IG or with inactivated, highly immunogenic vaccines. Elderly persons and those with advanced liver disease are at higher risk of the consequences of acute HAV, and they represent target populations for immediate vaccination. Challenges for the future include strategies for broad-based population vaccination, including cost-effective approaches.