Secretory autoantibodies in primary biliary cirrhosis (PBC)

New Frontiers in Autoimmune Diagnostics: A Systematic Review on Saliva Testing

(1) Background: Immunological laboratory testing is known to be complex, and it is usually performed in tertiary referral centers. Many criticalities affect diagnostic immunological testing, such as limited availability, the need for specifically trained laboratory staff, and potential difficulties in collecting blood samples, especially in the most vulnerable patients, i.e., the elderly and children. For this reason, the identification of a new feasible and reliable methodology for autoantibody detection is urgently needed. (2) Methods: We designed a systematic review to investigate the available literature on the utilization of saliva samples for immunological testing. (3) Results: A total of 170 articles were identified. Eighteen studies met the inclusion criteria, accounting for 1059 patients and 671 controls. The saliva collection method was mostly represented by passive drooling (11/18, 61%), and the most frequently described methodology for antibody detection was ELISA (12/18, 67%). The analysis included 392 patients with rheumatoid arthritis, 161 with systemic lupus erythematosus, 131 with type 1 diabetes mellitus, 116 with primary biliary cholangitis, 100 with pemphigus vulgaris, 50 with bullous pemphigoids, 49 with Sjogren syndrome, 39 with celiac disease, 10 with primary antiphospholipid syndromes, 8 with undifferentiated connective tissue disease, 2 with systemic sclerosis, and 1 with autoimmune thyroiditis. The majority of the reviewed studies involved adequate controls, and saliva testing allowed for a clear distinction of patients (10/12 studies, 83%). More than half of the papers showed a correlation between saliva and serum results (10/18, 55%) for autoantibody detection, with varying rates of correlation, sensitivity, and specificity. Interestingly, many papers showed a correlation between saliva antibody results and clinical manifestations. (4) Conclusions: Saliva testing might represent an appealing alternative to serum-based testing for autoantibody detection, considering the correspondence with serum testing results and the correlation with clinical manifestations. Nonetheless, standardization of sample collection processing, maintenance, and detection methodology has yet to be fully addressed.

Metabolic Dysfunction in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Not Due to Anti-mitochondrial Antibodies

Metabolic profiling studies have recently indicated dysfunctional mitochondria in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This includes an impaired function of pyruvate dehydrogenase complex (PDC), possibly driven by serum factor(s), which leads to inadequate adenosine triphosphate generation and excessive lactate accumulation. A reminiscent energy blockade is likely to occur in primary biliary cholangitis (PBC), caused by anti-PDC autoantibodies, as recently proposed. PBC is associated with fatigue and post-exertional malaise, also signifying ME/CFS. We herein have investigated whether ME/CFS patients have autoreactive antibodies that could interfere with mitochondrial function. We found that only 1 of 161 examined ME/CFS patients was positive for anti-PDC, while all PBC patients (15/15) presented significant IgM, IgG, and IgA anti-PDC reactivity, as previously shown. None of fibromyalgia patients (0/14), multiple sclerosis patients (0/29), and healthy blood donors (0/44) controls showed reactivities. Anti-mitochondrial autoantibodies (inner and outer membrane) were negative in ME/CFS cohort. Anti-cardiolipin antibody levels in patients did not differ significantly from healthy blood donors. In conclusion, the impaired mitochondrial/metabolic dysfunction, observed in ME/CFS, cannot be explained by presence of circulating autoantibodies against the tested mitochondrial epitopes.

The coexistence of Sjögren's syndrome and primary biliary cirrhosis: a comprehensive review

Organ-specific and systemic autoimmune diseases share numerous features and often coexist in the same patient. Autoimmune cholangitis/primary biliary cirrhosis and Sjogren syndrome represent paradigmatic examples of the common grounds of different autoimmunity phenotypes based on similarities in clinical manifestations and immunopathogenesis. In fact, primary biliary cirrhosis and Sjogren's syndrome have both been coined as an autoimmune epithelitis in which apoptosis may be in both cases the key element to explain the organ-specific immune-mediated injury against the biliary and exocrine gland epithelia, respectively. Further, growing evidence supports in both diseases the view that B cells, T cytotoxic cells, and T helper cells are involved in chronic inflammation, likely via the altered expression of pro-inflammatory cytokines. The presence of estrogen receptors on the biliary and exocrine gland epithelia has been advocated as a key to the female predominance encountered in primary biliary cirrhosis and Sjogren's syndrome. Sadly, despite available data, therapeutic approaches remain largely unsatisfactory and recent studies with mechanistic approaches (as in the case of B cell depletion with rituximab) have been of partial benefit only. Future studies should focus on new molecular tools (single-cell transcriptomics, microRNA, epigenetics) to provide unique insights into common mechanisms.

Peri-nuclear antibodies correlate with survival in Greek primary biliary cirrhosis patients

AIM: To investigate possible associations of anti-nuclear envelope antibody (ANEA) with disease severity and survival in Greek primary biliary cirrhosis (PBC) patients.

METHODS: Serum samples were collected at diagnosis from 147 PBC patients (85% female), who were followed-up for a median 89.5 mo (range 1-240). ANEA were detected with indirect immunofluorescence on 1% formaldehyde fixed Hep2 cells, and anti-gp210 antibodies were detected using an enzyme linked immunosorbent assay. Findings were correlated with clinical data, histology, and survival.

RESULTS: ANEA were detected in 69/147 (46.9%) patients and 31/147 (21%) were also anti-gp210 positive. The ANEA positive patients were at a more advanced histological stage (I-II/III-IV 56.5%/43.5% vs 74.4%/25.6%, P = 0.005) compared to the ANEA negative ones. They had a higher antimitochondrial antibodies (AMA) titer (≤ 1:160/> 1:160 50.7%/49.3% vs 71.8%/28.2%, P = 0.001) and a lower survival time (91.7 ± 50.7 mo vs 101.8 ± 55 mo, P = 0.043). Moreover, they had more advanced fibrosis, portal inflammation, interface hepatitis, and proliferation of bile ductules (P = 0.008, P = 0.008, P = 0.019, and P = 0.027, respectively). They also died more frequently of hepatic failure and/or hepatocellular carcinoma (P = 0.016). ANEA positive, anti-gp210 positive patients had a difference in stage (I-II/III-IV 54.8%/45.2% vs 74.4%/25.6%, P = 0.006), AMA titer (≤ 1:160/> 1:160 51.6%/48.4% vs 71.8%/28.2%, P = 0.009), survival (91.1 ± 52.9 mo vs 101.8 ± 55 mo, P = 0.009), and Mayo risk score (5.5 ± 1.9 vs 5.04 ± 1.3, P = 0.04) compared to the ANEA negative patients. ANEA positive, anti-gp210 negative patients had a difference in AMA titer (≤ 1:160/> 1:160 50%/50% vs 71.8%/28.2%, P = 0.002), stage (I-II/III-IV 57.9%/42.1% vs 74.4%/25.6%, P = 0.033), fibrosis (P = 0.009), portal inflammation (P = 0.018), interface hepatitis (P = 0.032), and proliferation of bile ductules (P = 0.031). Anti-gp210 positive patients had a worse Mayo risk score (5.5 ± 1.9 vs 4.9 ± 1.7, P = 0.038) than the anti-gp210 negative ones.

CONCLUSION: The presence of ANEA and anti-gp210 identifies a subgroup of PBC patients with advanced disease severity and poor prognosis.

Autoantibodies to muscarinic acetylcholine receptors found in patients with primary biliary cirrhosis

Background

Autoantibodies to the human muscarinic acetylcholine receptor of the M3 type (hmAchR M3) have been suggested to play an etiopathogenic role in Sjögren's syndrome. Primary biliary cirrhosis (PBC) often is associated with this syndrome. Therefore, we studied the co-presence of hmAchR M3 autoantibodies in patients with PBC.

Methods

Frequency of hmAchR M3 autoantibodies was assessed by Western blotting analysis as well as by an ELISA using a 25-mer peptide of the 2^nd extracellular loop of hmAchR M3. Co-localization of hmAchR M3/PBC-specific autoantibodies was studied by confocal laser scanning microscopy. Finally, sera from patients with PBC as well as from healthy controls were tested.

Results

Western blotting analysis as well as results from ELISA testing revealed a significantly enhanced IgG reactivity in PBC patients in contrast to healthy controls. Co-localization of autoantibodies with the hmAchR M3 receptor-specific autoantibodies was observed in 10 out of 12 PBC-patients but none of the 5 healthy controls. Antibodies of the IgM type were not found to be affected.

Conclusions

For the first time, our data demonstrate the presence of autoantibodies to the hmAchR M3 in PBC patients. These findings might contribute to the understanding of the pathogenesis of this disease. Further studies have to focus on the functionality of hmAchR M3 autoantibodies in PBC patients.

Lipoteichoic acid may affect the pathogenesis of bile duct damage in primary biliary cirrhosis

AIM

Intrahepatic bile ducts are the targets for inflammation in primary biliary cirrhosis (PBC), but their pathogenesis is not known. Gram-positive bacterial DNA was detected recently in gallbladder bile of PBC patients. In the present study, we assessed the possible pathological role of lipoteichoic acid (LTA), the gram-positive bacterial cell wall component, in PBC.

METHODS

Liver samples, obtained from 20 patients with PBC (stage 1-2 with CNSDC: stage 3-4 with loss of bile ducts = 10:10) and from 13 patients with chronic hepatitis due to hepatitis C virus (CH-C) with lymphocytic cholangitis, were subjected to immunohistochemical staining with polyclonal rabbit anti-LTA as the primary antibody. Serum reactivities to LTA were studied by ELISA. After 1 microg of purified LTA was placed in a 96-well microplate as an antigen, an antibody capture assay was carried out using serum samples from PBC (n = 20), CH-C (n = 13) and healthy subjects (n = 11).

RESULTS

LTA was localized around the sites of chronic non-suppurative destructive cholangitis (CNSDC) in the portal area in stage 1-2 PBC but was not detected in the portal area in CH-C. In stage 3-4 PBC, LTA was localized around sites of ductular proliferation at the periphery of portal tracts. IgM class anti-LTA serum titers were significantly higher in PBC than in CH-C. IgA class anti-LTA serum titers were significantly higher in PBC than in healthy subjects.

CONCLUSIONS

In the PBC livers, the profile of immunoreactivity to LTA changed markedly as the disease progressed. Sera from PBC showed higher levels of anti-LTA titers than CH-C (IgM) or from healthy subjects (IgA). The LTA-mediated immune system might affect the initiation and/or progression of PBC.

Bacterial motif DNA as an adjuvant for the breakdown of immune self-tolerance to pyruvate dehydrogenase complex

Bacterial DNA containing unmethylated CpG dinucleotide motifs is immunostimulatory to mammals, skewing CD4(+) T-cell responses toward the Th1 phenotype. Autoreactive T-cell responses seen in primary biliary cirrhosis (PBC) are typically of the Th1 phenotype, raising the possibility that bacterial DNA might play a role in the generation of pathologic autoimmunity. We therefore studied the effects of CpG motif-containing oligodeoxynucleotides (ODN) on responses to pyruvate dehydrogenase complex (PDC, the autoantigen in PBC) in a murine model. Sensitization of SJL/J mice with non-self-PDC has been shown to result in induction of autoreactive T-cell responses to PDC sharing characteristics with those seen in patients with PBC. Administration of CpG ODN to SJL/J mice at the time of sensitization with PDC resulted in a significant skewing of splenic T-cell response to self-PDC, with significant augmentation of the Th1 cytokine response (interleukin [IL] 2 and interferon [IFN] gamma) and reduction of the Th2 response (IL-4 and IL-10). In fact, CpG ODN seemed to be more effective at biasing the response phenotype and as effective at inducing liver histologic change as complete Freund's adjuvant (CFA), the standard adjuvant used for induction of Th1 responses in murine autoimmune and infectious immunity models. In conclusion, our findings raise the possibility that bacteria play a role in the development of autoimmunity (in PBC at least) through the potential of their DNA to shift the T-cell responses toward the phenotype associated with autoimmune damage. Moreover, this study suggests caution in the therapeutic use of CpG ODN as vaccine adjuvants.

The immunology of primary biliary cirrhosis: the end of the beginning?

The chronic liver disease primary biliary cirrhosis (PBC) is characterised by autoreactive B-cell and T-cell responses directed against mitochondrial antigens. In recent years these responses have been extensively characterised and the principal PBC associated autoantigen identified as pyruvate dehydrogenase complex (PDC). The identification of anti-PDC responses (present in over 95% of PDC patients) has given rise to important questions pertinent to our understanding of the pathogenesis of PBC. What specific role to anti-PDC responses play in target cell damage? How and why does immune tolerance break down to as highly conserved and ubiquitously expressed self-antigen as PDC? Why does breakdown in tolerance to an antigen present in all nucleated cells result in damage restricted to the intra-hepatic bile ducts? In attempting to answer these key questions we have, in this review, proposed a unifying hypothesis for the pathogenesis of PBC.

Antimitochondrial autoantibodies in saliva and sera from patients with primary biliary cirrhosis

BACKGROUND AND AIMS

Primary biliary cirrhosis (PBC) is a cholestatic autoimmune liver disease characterized by antimitochondrial autoantibodies (AMA) in serum, for which the reactants are E2 subunits of the three 2-oxoacid dehydrogenase (2-OAD) enzymes, particularly pyruvate dehydrogenase complex (PDC-E2). Some 70% of patients with PBC have a coexisting autoimmune disease including Sjögren's syndrome. We aimed to ascertain the frequency and isotype of AMA in saliva in PBC.

METHODS

Serum and saliva from 12 patients with PBC were tested for AMA by immunoblotting on bovine heart mitochondria, and by an automated microassay based on inhibition of the enzymatic activity of PDC.

RESULTS

Autoantibodies of the immunoglobulin (Ig)G, IgM, and IgA immunoglobulin isotypes against the E2 subunits of 2-OAD enzymes were demonstrable in PBC in serum (12 of 12 cases) and saliva (nine of 12 cases). Salivary autoantibodies, like serum autoantibodies, were predominantly reactive with PDC and of the IgG isotype. Results for serum and saliva corresponded closely with regard to reactivity with individual enzymes of the 2-OAD enzyme family, and to the autoantibody isotype that was predominantly expressed, and also in the capacity to inhibit the enzymatic activity of PDC.

CONCLUSIONS

The presence of AMA in saliva to 2-OAD enzymes indicates that salivary glands could participate in the pathogenetic process of PBC. The detection of salivary AMA by a semi-automated enzyme inhibition assay offers possibilities for rapid population screening for detection of preclinical PBC among at-risk individuals, middle-aged to older women.