Comparison of Single Nucleotide Polymorphism genotyping of CYP2C19 by Loop-mediated isothermal amplification and real-time PCR melting curve analysis.

BACKGROUND: CYP2C19, a member of cytochrome P450 enzymes, is involved in various drug metabolisms, such as Clopidogrel. Common Single Nucleotide Polymorphisms (SNPs) of CYP2C19 gene, CYP2C19*2 and CYP2C19*3, are liable for the poor metabolism of Clopidogrel. It is crucial to identify poor metabolizers for alternative treatment as poor metabolism of Clopidogrel has been shown to correlate with worse clinical outcome in acute coronary syndrome (ACS) patients. METHOD: A genotyping method, Loop-mediated isothermal amplification (LAMP) was employed in this study. CYP2C19*2 and CYP2C19*3 were adapted from Iwasaki M. et al. with modifications in the reaction mixtures and end-point detection method where simpler visual detection using SYBR® Safe was employed instead of a more technical and equipment demanding real-time PCR. Real-time PCR melting curve analysis is a common method for SNPs analysis and hence chosen as a reference for results obtained from the LAMP assay. RESULTS: The CYP2C19-LAMP assay successfully detected CYP2C19*2 and CYPC19*3 mutants. The typing results of CYP2C19-LAMP assay, performed in triplicates, were concordant with the real-time PCR melting curve analysis results. CONCLUSION: CYP2C19-LAMP assay using SYBR® Safe dye for visual detection of end-point result is a simple, rapid and cost-effective method for CYP2C19 genotyping.

Detection of HLA-B*58:01, the susceptible allele for allopurinol-induced hypersensitivity, by loop-mediated isothermal amplification.

BACKGROUND: Allopurinol, a common medication for gout treatment, can cause rare but life-threatening severe cutaneous adverse reactions. A strong pharmacogenetic association of human leucocyte antigen (HLA)-B*58:01 with allopurinol-induced drug hypersensitivity has been reported, especially in the Han Chinese population. OBJECTIVES: To develop a rapid and simple loop-mediated isothermal amplification (LAMP) assay of HLA-B*58:01 and evaluate its feasibility in predicting allopurinol-induced drug hypersensitivity. METHODS: Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 were designed. DNA extracted from 20 clinical blood samples of patients with gout was used to evaluate the effectiveness of the two LAMP primer sets for the detection of HLA-B*58:01. RESULTS: The results were compared with routine clinical genotyping methods. All extracted DNA samples tested with the HLA-B*58:01 LAMP assay showed agreement with the routine genotyping results. No amplifications were observed when unextracted blood samples were tested. CONCLUSIONS: The HLA-B*58:01 LAMP assay was confirmed to be simple, rapid and specific for the detection of HLA-B*58:01, and therefore of potential value in the diagnosis of allopurinol-induced hypersensitivity.

Loop-mediated isothermal amplification for detection of HLA-B*58:01 allele.

Strong association of human leukocyte antigen (HLA)-B*58:01 allele with allopurinol-induced hypersensitivity was found worldwide, especially in the Han Chinese populations. This study aims to develop and evaluate a loop-mediated isothermal amplification (LAMP) assay for rapid detection of HLA-B*58:01. Two sets of LAMP primers targeting exons 2 and 3 of HLA-B*58:01 allele were designed and their annealing temperatures were optimized accordingly. The heating devices for LAMP assay were tested. The analytical sensitivities of the two sets of LAMP primers were determined by 1:10 serial dilution of a positive control with homozygous HLA-B*58:01 allele from 100 ng down to 1 fg. The analytical specificities of the LAMP primers were evaluated by 30 selected University of California, Los Angeles (UCLA) DNA Exchange Program samples with known HLA-B loci typings previously typed by sequencing. Both sets of LAMP primers targeting exons 2 and 3 amplified optimally at 67°C. Thermal cycler is essential in achieving a more precise and specific LAMP result. The sensitivity of the exon 2 LAMP primer set was found to be 1 pg, whereas it was 10 ng for the exon 3 primer set in a 60-min amplification. The LAMP primers were highly specific because LAMP results were perfectly concordant to the sequencing results. The HLA-B*58:01 LAMP assay has compatible sensitivity and specificity to routine genotyping assays, and it is potentially an alternative screening test for the detection of HLA-B*58:01 and ultimately allopurinol-induced hypersensitivity.

Determination of mismatched donor HLA in kidney transplant recipients with unknown donor HLA phenotypes.

OBJECTIVE: To determine donor human leukocyte antigen (HLA) from renal allograft biopsies in transplant recipients whose donor HLA phenotype is not known. METHODS: Renal allograft biopsies were obtained from seven renal transplant recipients when indicated for allograft dysfunction or proteinuria. DNA was extracted fresh from allograft specimens, and HLA typing was performed with polymerase chain reaction-specific sequence primers (PCR-SSP) and polymerase chain reaction-sequence-specific oligonucleotides (PCR-SSO). RESULTS: HLA typing of the seven renal allograft biopsies was composed of both recipient and donor HLA phenotypes, allowing the determination of the donor HLA and the degree of HLA mismatching. CONCLUSIONS: Deducing mismatched donor HLA antigens in renal allograft recipients enables detection of donor-specific antibodies, and the management of humoral rejection, and enables more appropriate selection of a donor organ should future retransplantation be required.

Nanoindentation hardness of particles used in magnetorheological finishing (MRF).

Knowledge of the hardness of abrasive particles that are used in polishing is a key to the fundamental understanding of the mechanisms of material removal. The magnetorheological-finishing process uses both magnetic and nonmagnetic abrasive particles during polishing. The nanohardnesses of the micrometer-sized magnetic carbonyl iron and nonmagnetic abrasive particles have been measured successfully by use of novel, to our knowledge, sample-preparation and nanoindentation techniques. Some of the results reported compare favorably with existing microhardness data found in the literature, whereas other results are new.