Patch testing with the Japanese baseline series 2015: A 4-year experience.

BACKGROUND: The Japanese baseline series (JBS), established in 1994, was updated in 2008 and 2015. The JBS 2015 is a modification of the thin-layer rapid-use epicutaneous (TRUE) test (SmartPractice Denmark, Hillerød, Denmark). No nationwide studies concerning the TRUE test have previously been reported. OBJECTIVES: To determine the prevalence of sensitizations to JBS 2015 allergens from 2015 to 2018. METHODS: We investigated JBS 2015 patch test results using the web-registered Skin Safety Care Information Network (SSCI-Net) from April 2015 to March 2019. RESULTS: Patch test results of 5865 patients were registered from 63 facilities. The five allergens with the highest positivity rates were gold sodium thiosulfate (GST; 25.7%), nickel sulfate (24.5%), urushiol (9.1%), p-phenylenediamine (PPD; 8.9%), and cobalt chloride (8.4%). The five allergens with the lowest positivity rates were mercaptobenzothiazole (0.8%), formaldehyde (0.9%), paraben mix (1.1%), mercapto mix (1.1%), and PPD black rubber mix (1.4%). CONCLUSIONS: Nickel sulfate and GST had the highest positivity rates. The JBS 2015, including a modified TRUE test, is suitable for baseline series patch testing.

Multicenter 1-month follow-up study of the patch-test reaction to the gold sodium thiosulfate of the TRUE Test and its association with piercings and dental metal history.

BACKGROUND: There is controversy over late and long-lasting reactions to gold sodium thiosulfate (GST). OBJECTIVES: To study the GST patch-test reaction by observing the application site after 1 month, and to clarify the relevance of GST sensitization by piercings and dental metals. PATIENTS: A retrospective analysis was performed on 746 patients (143 male; 603 female) who were patch tested using GST of the TRUE Test. We conducted a questionnaire on the presence of piercings or dental metals in these patients. RESULTS: The GST positive rate was 27.9% at day (D)3 and/or D7 and 40.3% up to the 1-month reading. The positive rate was significantly higher in female patients and increased with age. Sixty-two percent of cases with a positive reaction at D7 continued to show a positive reaction after 1 month. Eleven percent of cases with a negative reaction at D3 and D7 showed a late reaction. Both piercings and dental metals were related to gold sensitization. CONCLUSIONS: The GST of the TRUE Test had a high positive and low false-negative rate. The 1-month reading after the patch test was important for identifying late reactions. Piercing history and dental metal were associated with gold sensitization.

HLA-DQ and RBFOX1 as susceptibility genes for an outbreak of hydrolyzed wheat allergy.

BACKGROUND: Food allergy is a growing health problem worldwide because of its increasing prevalence, life-threatening potential, and shortage of effective preventive treatments. In an outbreak of wheat allergy in Japan, thousands of patients had allergic reactions to wheat after using soap containing hydrolyzed wheat protein (HWP). OBJECTIVES: The aim of the present study was to investigate genetic variation that can contribute to susceptibility to HWP allergy. METHODS: We conducted a genome-wide association study of HWP allergy in 452 cases and 2700 control subjects using 6.6 million genotyped or imputed single nucleotide polymorphisms. Replication was assessed by genotyping single nucleotide polymorphisms in independent samples comprising 45 patients with HWP allergy and 326 control subjects. RESULTS: Through the genome-wide association study, we identified significant associations with the class II HLA region on 6p21 (P = 2.16 × 10-24 for rs9271588 and P = 2.96 × 10-24 for HLA-DQα1 amino acid position 34) and with the RBFOX1 locus at 16p13 (rs74575857, P = 8.4 × 10-9). The associations were also confirmed in the replication data set. Both amino acid polymorphisms (HLA-DQß1 amino acid positions 13 and 26) located in the P4 binding pockets on the HLA-DQ molecule achieved the genome-wide significance level (P < 5.0 × 10-8). CONCLUSIONS: Our data provide the first demonstration of genetic risk for HWP allergy and show that this genetic risk is mainly represented by multiple combinations of HLA variants.

Positive reactions to gold sodium thiosulfate in patch test panels (TRUE Test) in Japan: A multicentre study.

BACKGROUND: The proportion of positive test results with gold sodium thiosulfate included in a patch test panel (P-GST) had been found to be greater than that with gold sodium thiosulfate 0.5% pet. by allergEAZE (A-GST). OBJECTIVES: To compare positive reactions to P-GST and A-GST, and to evaluate late reactions after the day (D) 7 reading. METHODS: A retrospective analysis was performed of 588 patients at participating departments (119 males; 469 females) who were patch tested with P-GST and A-GST in May 2015 to March 2016. RESULTS: Positive test reactions to P-GST and A-GST were observed in 15% and 6% of patients, respectively. Three patients reported a positive reaction occurring after the D7 reading. CONCLUSIONS: Gold sodium thiosulfate often gives a positive reaction after 2 to 3 weeks, and, in such cases, the positive reaction may be sustained, so it is recommended to assess the reaction for up to 1 month after application.

A multi-institutional joint study of contact dermatitis related to hair colouring and perming agents in Japan.

BACKGROUND: In Japan, allergic contact dermatitis caused by hair colouring agents is a considerable problem for those occupationally exposed and also for consumers. Over the last 20 years, p-phenylenediamine (PPD) has been a common allergen, with ∼7% positive patch test reactions. OBJECTIVES: To investigate which ingredients caused allergic contact dermatitis related to hair dye and perming solutions in Japan, to assess whether PPD is suitable for screening for hair dye allergy, and to propose allergens for a Japanese hairdresser series. METHODS: We selected 19 hair cosmetic allergens, including PPD, Bandrowski's base, cysteamine HCl, and ammonium thioglycolate. Altogether 203 patients (26 males and 177 females) with suspected contact allergy to hair colouring or perming solutions at 14 hospitals in Japan were included. RESULTS: The highest prevalence of positive reactions (35.1%) was for PPD. p-Methylaminophenol and o-aminophenol were often positive, both in the PPD-positive and in the PPD-negative patients. Moreover, cysteamine HCl often yielded positive test reactions. CONCLUSIONS: PPD is insufficient to diagnose contact allergy caused by to hair dyes. We recommend 13 allergens to be included in a Japanese hairdresser series.

Gefitinib or chemotherapy for non-small-cell lung cancer with mutated EGFR.

BACKGROUND: Non-small-cell lung cancer with sensitive mutations of the epidermal growth factor receptor (EGFR) is highly responsive to EGFR tyrosine kinase inhibitors such as gefitinib, but little is known about how its efficacy and safety profile compares with that of standard chemotherapy. METHODS: We randomly assigned 230 patients with metastatic, non-small-cell lung cancer and EGFR mutations who had not previously received chemotherapy to receive gefitinib or carboplatin-paclitaxel. The primary end point was progression-free survival; secondary end points included overall survival, response rate, and toxic effects. RESULTS: In the planned interim analysis of data for the first 200 patients, progression-free survival was significantly longer in the gefitinib group than in the standard-chemotherapy group (hazard ratio for death or disease progression with gefitinib, 0.36; P<0.001), resulting in early termination of the study. The gefitinib group had a significantly longer median progression-free survival (10.8 months, vs. 5.4 months in the chemotherapy group; hazard ratio, 0.30; 95% confidence interval, 0.22 to 0.41; P<0.001), as well as a higher response rate (73.7% vs. 30.7%, P<0.001). The median overall survival was 30.5 months in the gefitinib group and 23.6 months in the chemotherapy group (P=0.31). The most common adverse events in the gefitinib group were rash (71.1%) and elevated aminotransferase levels (55.3%), and in the chemotherapy group, neutropenia (77.0%), anemia (64.6%), appetite loss (56.6%), and sensory neuropathy (54.9%). One patient receiving gefitinib died from interstitial lung disease. CONCLUSIONS: First-line gefitinib for patients with advanced non-small-cell lung cancer who were selected on the basis of EGFR mutations improved progression-free survival, with acceptable toxicity, as compared with standard chemotherapy. (UMIN-CTR number, C000000376.)

Enhancer of zeste homolog 2 is a novel prognostic biomarker in nonsmall cell lung cancer.

BACKGROUND: Enhancer of zeste homolog 2 (EZH2) epigenetically silences many genes through the trimethylation of histone H3 lysine 27 and is implicated in tumor growth, invasion, and metastasis. However, its role in lung cancer has not been well characterized. The objective of the current study was to elucidate the role of EZH2 in nonsmall cell lung cancer (NSCLC) by investigating both clinical samples and cell lines. METHODS: An immunohistochemical analysis of EZH2 expression was performed in samples from patients with stage I NSCLC to investigate the association of EZH2 expression levels with clinicopathologic variables. An in vitro cell growth assay and a Matrigel invasion assay also were conducted in the EZH2-expressing NSCLC cell lines A549 and H1299 after knocking down EZH2 expression by using an EZH2-specific short-hairpin RNA. RESULTS: The immunohistochemical analysis classified stage I NSCLC samples (n = 106) into a negative EZH2 expression group (n = 40; 37.7%) and a positive EZH2 expression group (n = 66; 62.3%). Positive EZH2 expression was associated significantly with larger tumor size (P = .014). Kaplan-Meier survival analyses and log-rank tests demonstrated that patients whose samples were classified into the positive EZH2 expression group had a significantly shorter overall survival (P = .015). Experiments in the NSCLC cell lines revealed that the knockdown of EZH2 expression reduced the tumor growth rate and invasive activity. CONCLUSIONS: The current results indicated that EZH2 promotes progression and invasion of NSCLC, and its expression is a novel prognostic biomarker in NSCLC.

Possible association of high-density lipoprotein cholesterol levels with trunk muscle deficits and decrease in energy expenditure in patients with or at risk for COPD: A pilot study.

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with low muscle mass and function caused by malnutrition and physical inactivity. We aimed to investigate possible associations between serum biomarkers and clinical traits including computed tomography-derived muscle measurements and energy expenditure indices in COPD. METHODS: Total energy expenditure (TEE) was measured by the doubly labeled water method, while physical activity level (PAL) was calculated as TEE/basal metabolic rate. Cross-sections and densities of pectoralis, rectus abdominis, and erector spinae muscles were measured. Serum biomarkers included adiponectin, insulin-like growth factor-1, and high-density lipoprotein (HDL)- and low-density lipoprotein (LDL)-cholesterol (C). RESULTS: HDL-C levels were significantly correlated with all muscle areas, densities, and TEE. Only LDL-C levels were correlated with PAL. CONCLUSIONS: HDL-C level was a potential biomarker for trunk muscle volumes and functions, as well as total energy expenditure in COPD.

Frequency of and variables associated with the EGFR mutation and its subtypes.

Mutation in the epidermal growth factor receptor (EGFR) is frequently seen in non-small cell lung cancers (NSCLCs), especially in Asian females with adenocarcinoma. The frequency of mutation and the factors associated requires to be elucidated by analyzing a large number of consecutive clinical samples. We summarized the result of the EGFR mutation analysis for 1,176 patients performed at the time of diagnosis or relapse. The PNA-LNA PCR clamp, a highly sensitive detection method for the EGFR mutation, was employed. For fresh cases a portion of samples isolated to establish the diagnosis of lung cancer was used. For cases with a relapsed disease archival tissue were tested. The variables associated with the EGFR mutation after removing the confound factors were investigated by the logistic analysis using the samples collected in our university (n = 308) where detailed information on patients were available. The frequency of the EGFR mutation and its subtypes were investigated using all samples (n = 1,176). The EGFR mutation was significantly associated with adenocarcinoma (p = 0.006) and light-smoking (p < 0.0001), but not gender. The deletions in exon 19 were more frequently associated with male gender while exon 21 deletions were with female gender (p = 0.0011). The overall frequency of the EGFR mutation was 31%. Our result suggests that the female predominance in the EGFR mutation rate is a reflection of a higher frequency of adenocarcinoma in females. The gender difference in the mutation subtypes may provide a clue for the mechanism of the occurrence of the EGFR mutation.

Peptide nucleic acid-locked nucleic acid polymerase chain reaction clamp-based detection test for gefitinib-refractory T790M epidermal growth factor receptor mutation.

Mutations in the epidermal growth factor receptor (EGFR) are observed in a fraction of non-small-cell lung cancers (NSCLS). EGFR mutation-positive NSCLS responds to gefitinib. Secondary T790M mutation confers gefitinib resistance to NSCLS. A detection test for the T790M mutation was designed based on the peptide nucleic acid-locked nucleic acid polymerase chain reaction clamp method. The specificity and sensitivity of the test were both greater than 0.99. The test revealed that only a small population of the PC-13 cells carried the T790M mutation. The test also revealed that the T790M mutation was found in none of 151 NSCLC specimens obtained before gefitinib treatment, whereas it was found in four of four specimens obtained from NSCLS that had become refractory to gefitinib. In one patient in whom the L858R-positive EGFR allele was amplified to multiple copies, an L858R-T790M double-mutant allele emerged during the gefitinib therapy. This allele was expressed highly. The T790M mutation detection test based on the peptide nucleic acid-locked nucleic acid polymerase chain reaction clamp method is sensitive and specific, and is applicable to clinical practice. It detects T790M-positive cells in the course of gefitinib treatment, and thus will help to devise therapies effective for T790M-positive NSCLS.

E-cadherin expression and epidermal growth factor receptor mutation status predict outcome in non-small cell lung cancer patients treated with gefitinib.

It is known that an epidermal growth factor receptor (EGFR) gene mutation(s) is present in a percentage of non-small cell lung cancers (NSCLCs). Gefitinib, an inhibitor of the tyrosine kinase activity of EGFR, is effective on most of them. The EGFR mutation status alone cannot fully predict the response to gefitinib and the prognosis for the patients. We hypothesized that information on the expression levels of phosphorylated-EGFR and -Akt, and E-cadherin, alone or in combination with information on the EGFR mutation, may refine our ability of prediction. We investigated 24 NSCLCs that had recurred after surgery and were treated with gefitinib. Specimens resected by surgery were subjected to the peptide nucleic acid-locked nucleic acid polymerase chain reaction clamp reaction to determine the EGFR mutation status, and to immunohistochemical staining of phosphorylated-EGFR and -Akt, and E-cadherin to determine their expression levels. The EGFR mutation status was predictive of responsive disease (complete response: CR + partial response: PR) and controlled disease (CR + PR + stable disease: SD). Positive E-cadherin staining was predictive of longer time to progression (12.4 vs. 5.9 months, p<0.05) and overall survival (OS) (18.4 vs. 13.0 months, p<0.05). Together the patients with an EGFR mutation and the patients with positive E-cadherin staining defined a patient group with a median OS of 18.4 months and excluded the patient group with the median OS of 3.7 months. Neither p-Akt nor p-EGFR staining was associated with the response and survival. In patients with surgically resected NSCLC tumors, the EGFR mutation status and E-cadherin staining can select patients who will benefit from gefitinib therapy.

Genetic heterogeneity of the epidermal growth factor receptor in non-small cell lung cancer cell lines revealed by a rapid and sensitive detection system, the peptide nucleic acid-locked nucleic acid PCR clamp.

Lung cancer is one of the leading causes of the cancer death worldwide. Gefitinib is an inhibitor of the tyrosine kinase activity of the epidermal growth factor receptor (EGFR) and has been introduced in the treatment of advanced lung cancers. The responsiveness to gefitinib has been linked to the presence of EGFR mutations. Clinical samples contain many normal cells in addition to cancer cells. A method capable of detecting EGFR mutations in a large background of wild-type EGFR genes could provide a superior clinical test. We developed a rapid and sensitive detection system for EGFR mutations named the peptide nucleic acid-locked nucleic acid (PNA-LNA) PCR clamp that can detect EGFR mutations in the presence of 100-to 1,000-fold background of wild-type EGFR. We used this method to screen 30 non-small cell lung cancer cell lines established from Japanese patients. In addition to 11 cell lines that have mutations, we found 12 cell lines in which specific mutations are observed only in the subpopulation(s) of the cells. Genetic heterogeneity of EGFR suggests that the EGFR gene is unstable in established cancers and the heterogeneity may explain variable clinical responses of lung cancers to gefitinib.

A highly specific and sensitive massive parallel sequencer-based test for somatic mutations in non-small cell lung cancer.

Molecular targeting therapy for non-small cell lung cancer (NSCLC) has clarified the importance of mutation testing when selecting treatment regimens. As a result, multiple-gene mutation tests are urgently needed. We developed a next-generation sequencer (NGS)-based, multi-gene test named the MINtS for investigating driver mutations in both cytological specimens and snap-frozen tissue samples. The MINtS was used to investigate the EGFR, KRAS, BRAF genes from DNA, and the ERBB2, and the ALK, ROS1, and RET fusion genes from RNA. We focused on high specificity and sensitivity (≥0.99) and even included samples with a cancer cell content of 1%. The MINtS enables testing of more than 100 samples in a single run, making it possible to process a large number of samples submitted to a central laboratory, and reducing the cost for a single sample. We investigated 96 cytological samples and 190 surgically resected tissues, both of which are isolated in daily clinical practice. With the cytological samples, we compared the results for the EGFR mutation between the MINtS and the PNA-LNA PCR clamp test, and their results were 99% consistent. In the snap-frozen tissue samples, 188/190 (99%) samples were successfully analyzed for all genes investigated using both DNA and RNA. Then, we used 200 cytological samples that were serially isolated in clinical practice to assess RNA quality. Using our procedure, 196 samples (98%) provided high-quality RNA suitable for analysis with the MINtS. We concluded that the MINtS test system is feasible for analyzing "druggable" genes using cytological samples and snap-frozen tissue samples. The MINtS will fill a needs for patients for whom only cytological specimens are available for genetic testing.

A prospective PCR-based screening for the EML4-ALK oncogene in non-small cell lung cancer.

PURPOSE: EML4-ALK is a lung cancer oncogene, and ALK inhibitors show marked therapeutic efficacy for tumors harboring this fusion gene. It remains unsettled, however, how the fusion gene should be detected in specimens other than formalin-fixed, paraffin-embedded tissue. We here tested whether reverse transcription PCR (RT-PCR)-based detection of EML4-ALK is a sensitive and reliable approach. EXPERIMENTAL DESIGN: We developed a multiplex RT-PCR system to capture ALK fusion transcripts and applied this technique to our prospective, nationwide cohort of non-small cell lung cancer (NSCLC) in Japan. RESULTS: During February to December 2009, we collected 916 specimens from 853 patients, quality filtering of which yielded 808 specimens of primary NSCLC from 754 individuals. Screening for EML4-ALK and KIF5B-ALK with our RT-PCR system identified EML4-ALK transcripts in 36 samples (4.46%) from 32 individuals (4.24%). The RT-PCR products were detected in specimens including bronchial washing fluid (n = 11), tumor biopsy (n = 8), resected tumor (n = 7), pleural effusion (n = 5), sputum (n = 4), and metastatic lymph node (n = 1). The results of RT-PCR were concordant with those of sensitive immunohistochemistry with ALK antibodies. CONCLUSIONS: Multiplex RT-PCR was confirmed to be a reliable technique for detection of ALK fusion transcripts. We propose that diagnostic tools for EML4-ALK should be selected in a manner dependent on the available specimen types. FISH and sensitive immunohistochemistry should be applied to formalin-fixed, paraffin-embedded tissue, but multiplex RT-PCR is appropriate for other specimen types.

Homozygosity mapping on homozygosity haplotype analysis to detect recessive disease-causing genes from a small number of unrelated, outbred patients.

Genes involved in disease that are not common are often difficult to identify; a method that pinpoints them from a small number of unrelated patients will be of great help. In order to establish such a method that detects recessive genes identical-by-descent, we modified homozygosity mapping (HM) so that it is constructed on the basis of homozygosity haplotype (HM on HH) analysis. An analysis using 6 unrelated patients with Siiyama-type α1-antitrypsin deficiency, a disease caused by a founder gene, the correct gene locus was pinpointed from data of any 2 patients (length: 1.2-21.8 centimorgans, median: 1.6 centimorgans). For a test population in which these 6 patients and 54 healthy subjects were scrambled, the approach accurately identified these 6 patients and pinpointed the locus to a 1.4-centimorgan fragment. Analyses using synthetic data revealed that the analysis works well for IBD fragment derived from a most recent common ancestor (MRCA) who existed less than 60 generations ago. The analysis is unsuitable for the genes with a frequency in general population more than 0.1. Thus, HM on HH analysis is a powerful technique, applicable to a small number of patients not known to be related, and will accelerate the identification of disease-causing genes for recessive conditions.

Prediction of the pathogens that are the cause of pneumonia by the battlefield hypothesis.

Commensal organisms are frequent causes of pneumonia. However, the detection of these organisms in the airway does not mean that they are the causative pathogens; they may exist merely as colonizers. In up to 50% cases of pneumonia, the causative pathogens remain unidentified, thereby hampering targeting therapies. In speculating on the role of a commensal organism in pneumonia, we devised the battlefield hypothesis. In the "pneumonia battlefield," the organism-to-human cell number ratio may be an index for the pathogenic role of the organism. Using real-time PCR reactions for sputum samples, we tested whether the hypothesis predicts the results of bacteriological clinical tests for 4 representative commensal organisms: Streptococcus pneumoniae, Haemophilus influenzae, Pseudomonas spp., and Moraxella catarrhalis. The cutoff value for the organism-to-human cell number ratio, above which the pathogenic role of the organism was suspected, was set up for each organism using 224 sputum samples. The validity of the cutoff value was then tested in a prospective study that included 153 samples; the samples were classified into 3 groups, and each group contained 93%, 7%, and 0% of the samples from pneumonia, in which the pathogenic role of Streptococcus pneumoniae was suggested by the clinical tests. The results for Haemophilus influenzae, Pseudomonas spp., and Moraxella catarrhalis were 100%, 0%, and 0%, respectively. The battlefield hypothesis enabled legitimate interpretation of the PCR results and predicted pneumonia in which the pathogenic role of the organism was suggested by the clinical test. The PCR reactions based on the battlefield hypothesis may help to promote targeted therapies for pneumonia. The prospective observatory study described in the current report had been registered to the University Hospital Medical Information Network (UMIN) registry before its initiation, where the UMIN is a registry approved by the International Committee of Medical Journal Editors (ICMJE). The UMIN registry number was UMIN000001118: A prospective study for the investigation of the validity of cutoff values established for the HIRA-TAN system (April 9, 2008).

First-line gefitinib for patients with advanced non-small-cell lung cancer harboring epidermal growth factor receptor mutations without indication for chemotherapy.

PURPOSE: This multicenter phase II study was undertaken to investigate the efficacy and feasibility of gefitinib for patients with advanced non-small-cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations without indication for chemotherapy as a result of poor performance status (PS). PATIENTS AND METHODS: Chemotherapy-naïve patients with poor PS (patients 20 to 74 years of age with Eastern Cooperative Oncology Group PS 3 to 4, 75 to 79 years of age with PS 2 to 4, and >or= 80 years of age with PS 1 to 4) who had EGFR mutations examined by the peptide nucleic acid-locked nucleic acid polymerase chain reaction clamp method were enrolled and received gefitinib (250 mg/d) alone. RESULTS: Between February 2006 and May 2007, 30 patients with NSCLC and poor PS, including 22 patients with PS 3 to 4, were enrolled. The overall response rate was 66% (90% CI, 51% to 80%), and the disease control rate was 90%. PS improvement rate was 79% (P < .00005); in particular, 68% of the 22 patients improved from >or= PS 3 at baseline to

Homozygosity haplotype allows a genomewide search for the autosomal segments shared among patients.

A promising strategy for identifying disease susceptibility genes for both single- and multiple-gene diseases is to search patients' autosomes for shared chromosomal segments derived from a common ancestor. Such segments are characterized by the distinct identity of their haplotype. The methods and algorithms currently available have only a limited capability for determining a high-resolution haplotype genomewide. We herein introduce the homozygosity haplotype (HH), a haplotype described by the homozygous SNPs that are easily obtained from high-density SNP genotyping data. The HH represents haplotypes of both copies of homologous autosomes, allowing for direct comparisons of the autosomes among multiple patients and enabling the identification of the shared segments. The HH successfully detected the shared segments from members of a large family with Marfan syndrome, which is an autosomal dominant, single-gene disease. It also detected the shared segments from patients with model multigene diseases originating with common ancestors who lived 10-25 generations ago. The HH is therefore considered to be useful for the identification of disease susceptibility genes in both single- and multiple-gene diseases.

Autoantibody response to microsomal epoxide hydrolase in hepatitis C and A.

Autoimmune responses were observed in a large proportion of hepatitis C cases and are suspected to be part of viral pathogenesis. The AN6520 antigen (AN-Ag) is a normal cellular protein mainly expressed in liver that was found associated with non-A, non-B hepatitis. To elucidate its pathogenic role in hepatitis C, we developed an IgM capture assay using purified AN-Ag and confirmed that the antibody response to AN-Ag is associated almost exclusively with hepatitis C cases (29%). Screening of a human liver expression library revealed that AN-Ag is mainly the microsomal epoxide hydrolase (mEH), a drug-metabolizing enzyme that plays an important role in the metabolism of some mutagenic and carcinogenic epoxides. Using the purified recombinant human mEH as an antigen, we now found that antibodies against this protein are associated with nearly 82% of hepatitis C virus infections and surprisingly with 46% of patients with hepatitis A. The appearance of AN-Ag/mEH in the incubation period of hepatitis C as previously reported and the antibody responses shown here indicate that this enzyme may be a marker for or even a cause of some of the pathology associated with hepatitis C and A.