Retrovirus infection as a trigger for primary biliary cirrhosis?

Pathogen infections and primary biliary cholangitis

Primary biliary cholangitis (PBC) is a multi-factorial disease caused by the interaction of both genetic predisposition and environmental triggers. Bacterial infection has been investigated most intensively, both epidemiologically and experimentally, as a prime environmental aetiology in PBC. The association of recurrent history of urinary tract infection (UTI) with PBC has been frequently confirmed by several large-scale, case-control studies, despite variation in geographic area or case-finding methods. Escherichia coli is a predominant pathogen in most cases with UTI. Animal studies and molecular mimicry analysis between the human and E. coli E2 subunit of the 2-oxo-acid dehydrogenase complexes demonstrated that E. coli infection is a key factor in breaking immunological tolerance against the mitochondria, resulting in the production of anti-mitochondrial autoantibodies (AMA), the disease-specific autoantibodies of PBC. Novosphingobium aromaticivorans, a ubiquitous xenobiotic-metabolizing bacterium, is another candidate which may be involved in the aetiology of PBC. Meanwhile, improved environmental hygiene and increased prevalence of PBC, especially in males, may argue against the aetiological role of bacterial infection in PBC. Multiple mechanisms can result in the loss of tolerance to mitochondrial autoantigens in PBC; nonetheless, bacterial infection is probably one of the dominant pathways, especially in female patients. Notably, there is a rising prevalence of male patients with PBC. With increasing exposure to environmental xenobiotics in both genders, studies directed towards identifying the environmental culprit with systematically designed case-control studies are much needed to further determine the environmental factors and role of bacterial infections in PBC.

A case of severe osteomalacia caused by Tubulointerstitial nephritis with Fanconi syndrome in asymptomotic primary biliary cirrhosis

Background

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease, characterized by increased concentrations of serum IgM and the presence of circulating anti-mitochondrial antibodies. Although bone diseases such as osteoporosis or osteodystrophy are commonly associated with PBC, osteomalacia which is caused by abnormal vitamin D metabolism, mineralization defects, and phosphate deficiency has not been recognized as a complication of PBC.

Case presentation

We report the case of a 49-year-old Japanese woman who complained of multiple fractures. Hypophosphatemic osteomalacia was diagnosed from a low serum phosphorus level, 1,25-dihydroxyvitamin D₃ level_, high levels of bone specific alkaline phosphatase and the findings of bone scintigraphy, although a bone biopsy was not performed. Twenty four hour urine demonstrated a low renal fractional tubular reabsorption of phosphate, increased fractional excretion of uric acid and generalized aminoaciduria. An intravenous bicarbonate loading test suggested the presence of proximal renal tubular acidosis (RTA). These biochemical data indicated Fanconi syndrome with proximal RTA. A kidney biopsy demonstrated the features of tubulointerstitial nephritis (TIN).

The patient was also suspected as having primary biliary cirrhosis (PBC) because of high levels of alkaline phosphatase, IgM and the presence of anti-mitochondrial M2 antibody, though biochemical liver function was normal. Sequential liver biopsy was compatible with PBC and the diagnosis of PBC was definite. After administration of 1,25 dihydroxyvitamin D_3, neutral potassium phosphate, sodium bicarbonate for osteomalacia and subsequent predonizolone for TIN, symptoms of fractures were relieved and renal function including Fanconi syndrome was ameliorated.

Conclusion

In this case, asymptomatic PBC was shown to induce TIN with Fanconi syndrome with dysregulation of electrolytes and vitamin D metabolism, which in turn led to osteomalacia with multiple fractures. Osteomalacia has not been recognized as a result of the renal involvement of PBC. PBC and its rare complication of TIN with Fanconi syndrome should be considered in adult patients with unexplained osteomalacia even in the absence of liver dysfunction.

Sex differences associated with primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a cholestatic liver disease of autoimmune origin, characterised by the destruction of small intrahepatic bile ducts. The disease has an unpredictable clinical course but may progress to fibrosis and cirrhosis. The diagnostic hallmark of PBC is the presence of disease-specific antimitochondrial antibodies (AMA), which are pathognomonic for the development of PBC. The disease overwhelmingly affects females, with some cases of male PBC being reported. The reasons underlying the low incidence of males with PBC are largely unknown. Epidemiological studies estimate that approximately 7–11% of PBC patients are males. There does not appear to be any histological, serological, or biochemical differences between male and female PBC, although the symptomatology may differ, with males being at higher risk of life-threatening complications such as gastrointestinal bleeding and hepatoma. Studies on X chromosome and sex hormones are of interest when studying the low preponderance of PBC in males; however, these studies are far from conclusive. This paper will critically analyze the literature surrounding PBC in males.

Urinary tract infection as a risk factor for autoimmune liver disease: from bench to bedside

Autoimmune liver diseases include autoimmune hepatitis (AIH), primary biliary cirrhosis (PBC), and primary sclerosing cholangitis. A variety of environmental and genetic risk factors have been associated with these conditions. Recurrent urinary tract infections (rUTI) have been strongly associated with PBC, and to a lesser extent with AIH. These observations were initially based on the observation of significant bacteriuria in female patients with PBC. Larger epidemiological studies demonstrated that there was indeed a strong correlation between recurrent UTI and PBC. AIH has not been linked to recurrent UTI in epidemiological studies; however treatment of UTI with nitrofurantoin can induce AIH. As Escherichia coli is the most prevalent organism isolated in women with UTI, it has been suggested that molecular mimicry between microbial and human PDC-E2 (the main autoantigenic target in PBC) epitopes may explain the link between UTI and PBC. Multiple studies have demonstrated molecular mimicry and immunological cross-reactivity involving microbial and self-antigen mimics. This review will examine the literature surrounding UTI and autoimmune liver disease. This will include case reports and epidemiological studies, as well as experimental data.

Linking human beta retrovirus infection with primary biliary cirrhosis

Several environmental agents have been linked with primary biliary cirrhosis (PBC) that include bacteria, xenobiotics and viruses. A human beta retrovirus (HBRV) related to mouse mammary tumor virus has been cloned and characterized from patients with PBC. This agent can be detected in the majority of patients' perihepatic lymph nodes by immunochemistry and RT-PCR. The HBRV has recently been isolated in culture and integration sites have been identified in the genome of patients to provide convincing evidence of beta retrovirus infection in patients. Three lines of evidence support a role for the virus in PBC. First, the beta retrovirus is linked with aberrant expression of mitochondrial protein(s) on the biliary epithelium cell (BEC) surface, a disease specific phenotype. Second, the related agent, mouse mammary tumor virus has been linked with autoimmune biliary disease in the NOD.c3c4 mouse model for PBC. In this mouse model, the virus is localized to diseased biliary epithelium that also display aberrant expression of the mitochondrial autoantigens. In translational studies, both patients with PBC and NOD.c3c4 mice demonstrate significant improvement in biliary disease with combination antiviral therapy. An overview of the biological relevance of the beta retrovirus infection in PBC will be discussed in this review.

Primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is an immune-mediated chronic cholestatic liver disease with a slowly progressive course. Without treatment, most patients eventually develop fibrosis and cirrhosis of the liver and may need liver transplantation in the late stage of disease. PBC primarily affects women (female preponderance 9–10:1) with a prevalence of up to 1 in 1,000 women over 40 years of age. Common symptoms of the disease are fatigue and pruritus, but most patients are asymptomatic at first presentation. The diagnosis is based on sustained elevation of serum markers of cholestasis, i.e., alkaline phosphatase and gamma-glutamyl transferase, and the presence of serum antimitochondrial antibodies directed against the E2 subunit of the pyruvate dehydrogenase complex. Histologically, PBC is characterized by florid bile duct lesions with damage to biliary epithelial cells, an often dense portal inflammatory infiltrate and progressive loss of small intrahepatic bile ducts. Although the insight into pathogenetic aspects of PBC has grown enormously during the recent decade and numerous genetic, environmental, and infectious factors have been disclosed which may contribute to the development of PBC, the precise pathogenesis remains enigmatic. Ursodeoxycholic acid (UDCA) is currently the only FDA-approved medical treatment for PBC. When administered at adequate doses of 13–15 mg/kg/day, up to two out of three patients with PBC may have a normal life expectancy without additional therapeutic measures. The mode of action of UDCA is still under discussion, but stimulation of impaired hepatocellular and cholangiocellular secretion, detoxification of bile, and antiapoptotic effects may represent key mechanisms. One out of three patients does not adequately respond to UDCA therapy and may need additional medical therapy and/or liver transplantation. This review summarizes current knowledge on the clinical, diagnostic, pathogenetic, and therapeutic aspects of PBC.

Clinical trial: randomized controlled study of zidovudine and lamivudine for patients with primary biliary cirrhosis stabilized on ursodiol

BACKGROUND

A human betaretrovirus has been characterized in patients with primary biliary cirrhosis (PBC). Uncontrolled studies using combination anti-retroviral therapy have reported significant biochemical and histological improvement.

AIM

To conduct a double blind, randomized controlled trial as a proof of principal to link infection with PBC.

METHODS

Fifty-nine patients with an alkaline phosphatase level>1.5 upper limits of normal stabilized on ursodeoxycholic acid therapy were randomized to either 300 mg zidovudine and 150 mg lamivudine B.I.D. or placebo for 6 months.

RESULTS

None of the patients normalized alkaline phosphatase and no significant differences were observed in normalizing serum aminotransferase levels. Significant differences were observed in the antiviral versus placebo arms with improvements in serial alkaline phosphatase (p<0.04), ALT (p<0.03) and AST (p<0.04) as well as clinical score (p<0.02). After 6 months, 25% of patients in the placebo arm and 4% in the antiviral arm had evidence of virus in serum.

CONCLUSIONS

The study endpoints for normalizing hepatic biochemistry were too stringent to show efficacy for zidovudine and lamivudine therapy despite the demonstrable impact on clinical and biochemical improvement. Accordingly, more potent anti-viral regimens will be required to confirm the efficacy of antiviral therapy in PBC patients with human betaretrovirus infection.

Other potential medical therapies: the use of antiviral agents to investigate and treat primary ciliary cirrhosis

A human betaretrovirus has been characterized in patients with primary biliary cirrhosis (PBC) and the related mouse mammary tumor virus linked with autoimmune biliary disease in the NOD.c3c4 mouse model. Translational studies have been performed in patients who have PBC to investigate the role of viral infection in disease. Patients treated with Combivir experienced significant improvements in hepatic biochemistry, clinical symptoms, and histology with evidence of reversal of ductopenia. Preliminary studies suggest that the NOD.c3c4 mouse model of PBC provides a good model to test safer and more potent drug regimens for future use in trials for patients who have PBC.

Human thyroid autoantigens and proteins of Yersinia and Borrelia share amino acid sequence homology that includes binding motifs to HLA-DR molecules and T-cell receptor

We previously reported that the spirochete Borrelia burgdorferi could trigger autoimmune thyroid diseases (AITD). Subsequently, we showed local amino acid sequence homology between all human thyroid autoantigens (human thyrotropin receptor [hTSH-R], human thyroglobulin [hTg], human thyroperoxidase [hTPO], human sodium iodide symporter [hNIS]) and Borrelia proteins (n = 6,606), and between hTSH-R and Yersinia enterocolitica (n = 1,153). We have now updated our search of homology with Borrelia (n = 11,198 proteins) and extended our search on Yersinia to the entire species (n = 40,964 proteins). We also searched the homologous human and microbial sequences for peptide-binding motifs of HLA-DR molecules, because a number of these class II major histocompatibility complex (MHC) molecules (DR3, DR4, DR5, DR8, and DR9) are associated with AITD. Significant homologies were found for only 16 Borrelia proteins (5 with hTSH-R, 2 with hTg, 3 with hTPO, and 6 with hNIS) and only 19 Yersinia proteins (4 with hTSH-R, 2 with hTg, 2 with hTPO, and 11 with hNIS). Noteworthy, segments of thyroid autoantigens homologous to these microbial proteins are known to be autoantigenic. Also, the hTSH-R homologous region of one Borrelia protein (OspA) contains an immunodominant epitope that others have found to be homologous to hLFA-1. This is of interest, as the hLFA-1/ICAM-1 ligand/receptor pair is aberrantly expressed in the follicular cells of thyroids affected by Hashimoto's thyroiditis. A computer-assisted search detected antigenic peptide binding motifs to the DR molecules implicated in AITD. In conclusion, our in silico data do not directly demonstrate that Borrelia and Yersinia proteins trigger AITD but suggest that a restricted number of them might have the potential to, at least in persons with certain HLA-DR alleles.

Tubulointerstitial nephritis and Fanconi syndrome in primary biliary cirrhosis

Primary biliary cirrhosis is a chronic cholestatic liver disease of unknown cause that predominantly affects middle-aged women. Distal tubular acidosis is the main renal complication of primary biliary cirrhosis. Tubulointerstitial nephritis and Fanconi syndrome have been reported more rarely. We report on 2 patients with primary biliary cirrhosis who presented with tubulointerstitial nephritis and Fanconi syndrome and review similar cases published previously. Serum from 1 patient exerted an inhibitory effect on pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, 2 mitochondrial enzymes that are the main targets of antimitochondrial antibodies in primary biliary cirrhosis. Antimitochondrial antibodies may have a role in the genesis of tubulointerstitial nephritis and Fanconi syndrome, 2 typical renal features of mitochondrial cytopathies. Tubulointerstitial nephritis and Fanconi syndrome have to be added to the spectrum of renal diseases associated with primary biliary cirrhosis.

Primary biliary cirrhosis after aortoiliac reconstruction surgery using a Y-graft: A case report

Primary biliary cirrhosis (PBC) is an autoimmune disease characterized by anti-mitochondrial antibodies and destruction of intra-hepatic bile ducts. Though little is known about the etiology of PBC, some reports suggest that xenobiotics and viral infections may induce PBC. We describe a case of PBC after the aortoiliac reconstruction surgery using a Y-graft.

Pilot studies of single and combination antiretroviral therapy in patients with primary biliary cirrhosis

OBJECTIVE

Preliminary reports suggest that patients with primary biliary cirrhosis (PBC) have evidence of human betaretrovirus infection. The aim of this study was to determine whether antiviral therapy impacts on the disease process.

METHODS

We conducted two consecutive open-labeled, nonrandomized, 1-yr pilot studies; the first with lamivudine 150 mg/day and the second with Combivir combination therapy using lamivudine 150 mg and zidovudine 300 mg twice a day. Eleven PBC patients enrolled in each study, seven patients were entered into both studies, and one patient was withdrawn from each study due to side effects.

RESULTS

Evaluation of liver biopsies before and after lamivudine therapy showed a 4-5 increase in necroinflammatory score, a 1-1.5 elevation in bile duct injury, with little change in the percentage of portal tracts with bile ducts (50-52%). None of the patients in the lamivudine study normalized alkaline phosphatase. Histological assessment following Combivir therapy revealed a 6 to 4 improvement in necroinflammatory score (p < 0.03, 95% CI: 0.53-2.33), a 3 to 1 reduction in bile duct injury (p < 0.02, 95% CI: 1.08-2.07), and a 45-75% increase in portal tracts with bile ducts (p < 0.05, 95% CI: 0.02-0.29). In the Combivir cohort, five patients normalized alkaline phosphatase and four developed normal AST, ALT, and alkaline phosphatase.

CONCLUSIONS

Histological and biochemical endpoints were achieved in the Combivir pilot study suggesting a larger placebo-controlled trial is required as a proof of principle to assess whether antiviral therapy impacts the PBC disease process.