One fits all: a highly sensitive combined ddPCR/pyrosequencing system for the quantification of microchimerism after hematopoietic and solid organ transplantation.

OBJECTIVES: A combined digital droplet PCR (ddPCR)/pyrosequencing assay system was developed that demonstrated advantages applicable to multiple qualitative and quantitative molecular genetic diagnostic applications. Data for characterizing this combined approach for hematologic stem cell transplantation (HSCT) and allele quantification from graft-derived cell-free (cf) DNA in solid organ transplantation (SOT) is presented. METHODS: ddPCR and pyrosequencing assays targeting 32 SNPs/markers were established. ddPCR results from 72 gDNAs of 55 patients after allogeneic HSCT and 107 plasma-cfDNAs of 25 liver transplant recipients were compared with established methods/markers, i.e. short-tandem-repeat PCR and ALT, respectively. RESULTS: The ddPCR results were in good agreement with the established marker. The limit of detection was 0.02 % minor allele fraction. The relationship between ddPCR and STR-PCR was linear with R2=0.98 allowing to transfer previously established clinical STR-PCR cut-offs to ddPCR; 50-fold higher sensitivity and a variation coefficient of <2 % enable the use of low DNA concentrations (e.g. pre-sorted cells). ddPCR detected liver allograft injury at least as sensitive as ALT suggesting that ddPCR is a reliable method to monitor the transplant integrity, especially when other biomarkers are lacking (e.g. kidney). CONCLUSIONS: Combining pyrosequencing for genotyping and ddPCR for minor allele quantification enhances sensitivity and precision for the patient after HSCT and SOT. The assay is designed for maximum flexibility. It is expected to be suitable for other applications (sample tracking, prenatal diagnostics, etc.).

Hereditary Spherocytosis: Can Next-Generation Sequencing of the Five Most Frequently Affected Genes Replace Time-Consuming Functional Investigations?

Congenital defects of the erythrocyte membrane are common in northern Europe and all over the world. The resulting diseases, for example, hereditary spherocytosis (HS), are often underdiagnosed, partly due to their sometimes mild and asymptomatic courses. In addition to a broad clinical spectrum, this is also due to the occasionally complex diagnostics that are not available to every patient. To test whether next-generation sequencing (NGS) could replace time-consuming spherocytosis-specific functional tests, 22 consecutive patients with suspected red cell membranopathy underwent functional blood tests. We were able to identify the causative genetic defect in all patients with suspected HS who underwent genetic testing (n = 17). The sensitivity of the NGS approach, which tests five genes (ANK1 (gene product: ankyrin1), EPB42 (erythrocyte membrane protein band4.2), SLC4A1 (band3), SPTA1 (α-spectrin), and SPTB (ß-spectrin)), was 100% (95% confidence interval: 81.5-100.0%). The major advantage of genetic testing in the paediatric setting is the small amount of blood required (<200 µL), and compared to functional assays, sample stability is not an issue. The combination of medical history, basic laboratory parameters, and an NGS panel with five genes is sufficient for diagnosis in most cases. Only in rare cases, a more comprehensive functional screening is required.

Incidence of HAV and HBV infections and vaccination rates in patients with autoimmune liver diseases.

OBJECTIVES: Hepatitis A virus (HAV) or hepatitis B virus (HBV) superinfection is associated with an increased mortality in patients with chronic liver diseases (CLD). Despite official recommendations, it was reported that the vaccination rate against HAV is low in patients with chronic hepatitis C infection. To evaluate the situation in patients with autoimmune liver diseases, we conducted a retrospective cohort study. METHODS: Susceptibility to HAV and HBV infections, course of HAV and HBV infections, vaccination rates against HAV and HBV, and efficacy of hepatitis A/B vaccines were evaluated by antibody testing in 225 patients with autoimmune liver diseases during 1,677 person-years. RESULTS: Susceptibility to HAV/HBV infection was 51/86%. Incidence of HAV/HBV infection was 1.3/1.4 per 1,000 person-years. One HAV infection occurred, but the patient recovered spontaneously. Two patients were HBV-infected after receiving an anti-HBc-positive (antibody to hepatitis B core antigen) donor graft during orthotopic liver transplantation, and one of them developed chronic HBV infection. Vaccination rates were 11% (HBV) and 13% (HAV), respectively. Seventy-six percent of the vaccinated patients (HBV vaccine) developed anti-HBs (antibody to hepatitis surface antigen) >or=10 UI/L. Ten out of 13 vaccinated patients, showing a low or nonresponse to hepatitis B vaccine, had concomitant immunosuppressive therapy. Anti-HAV was detectable in all patients after administration of HAV vaccine. CONCLUSIONS: Patients with autoimmune liver diseases have a high susceptibility to HAV and HBV infections. Vaccination rates are low in this patient cohort and efficacy of hepatitis B vaccine is reduced due to immunosuppressive therapy. Improving adherence to vaccine recommendations is essential to prevent HAV and HBV infections in patients with autoimmune liver diseases.