Detection of four beta-thalassemia point mutations in Iranians using a PCR-ELISA genotyping system.

Development of molecular techniques with analytical capability of mutation detection can realize the medical diagnosis of diseases and improve people's health. beta-Thalassemia is one of the most prevalent genetic disorders in Iran and using a simple and rapid test in laboratories for the mass screening and prenatal diagnosis is essential. Here, we described a simple method for rapid detection of four common beta-thalassemia point mutations in Iranians (IVS-II-1 (G-->A), IVS-I-5 (G-->C), FSC 8/9 (+G), IVS-I-110 (G-->A)) using a PCR-ELISA genotyping system. After DNA isolation from whole blood, a segment of beta-globin gene was amplified by DIG-labeling PCR. The DIG-labeled PCR amplicons were denatured and added to biotinylated normal probe (for normal gene allele) and mutant probe (for mutant gene allele). The hybrids were detected by colorimetric ELISA method. The optical densities obtained using normal and mutant probes with heterozygous PCR products were very similar. The optical densities obtained using mutant probes were higher than normal probes with homozygous PCR products. In vice versa, the optical densities obtained using normal probes were higher than mutant probes with normal PCR products. All the results demonstrated that the PCR-ELISA has similar specificity in comparison to the amplification refractory mutation system.

Enzyme-linked immunosorbent assay of nucleic acid sequence-based amplification for molecular detection of M. tuberculosis.

An enzyme-linked immunosorbent assay of nucleic acid sequence-based amplification (NASBA-ELISA) was developed for molecular detection of Mycobacterium tuberculosis. The primers targeting 16S rRNA were used for the amplification of bacterial RNA by the isothermal digoxigenin (DIG)-labeling NASBA process, resulting in the accumulation of DIG-labeled RNA amplicons. The amplicons were hybridized with a specific biotinylated DNA probe which was non-covalently immobilized on streptavidin-coated microtiter plate. The RNA-DNA hybrids were colorimetrically detected by the addition of an anti-DIG antibody HRP conjugate and 2,2-azino-di-(3-ethylbenzthiazolinsulfonate) substrate. Using this method, as little as 1 x 10(2) CFU ml(-1) of M. tuberculosis was detected within less than 5h. Results obtained from the clinical specimens showed 85.7% and 96% sensitivity and specificity, respectively. No interference was encountered in the amplification and detection of M. tuberculosis in the presence of non-target bacteria, confirming the specificity of the method.