Characteristics and applications of nucleic acid sequence-based amplification (NASBA)

Nucleic acid sequence-based amplification (NASBA) is a sensitive, isothermal, transcription-based amplification system specifically designed for the detection of RNA targets. In some NASBA systems, DNA is also amplified though very inefficiently and only in the absence of the corresponding RNA target or in case of an excess (>1,000-fold) of target DNA over RNA. As NASBA is primer-dependent and amplicon detection is based on probe binding, primer and probe design rules are included. An overview of various target nucleic acids that have been amplified successfully using NASBA is presented. For the isolation of nucleic acids prior to NASBA, the "Boom" method, based on the denaturing properties of guanidine isothiocyanate and binding of nucleic acid to silica particles, is preferred. Currently, electro-chemiluminescence (ECL) is recommended for the detection of the amplicon at the end of amplification. In the near future, molecular beacons will be introduced enabling "real-time detection," i.e., amplicon detection during amplification. Quantitative HIV-1 NASBA and detection of up to 48 samples can then be performed in only 90 min.