Nucleic acid sequence-based amplification NASBA

Both target and signal amplification systems have been successfully employed to detect and quantitate specific nucleic acid sequences in clinical specimens. Polymerase chain reaction (PCR), nucleic acid sequence-based amplification (NASBA), transcription-mediated amplification (TMA), strand displacement amplification (SDA), and ligase chain reaction (LCR) are all examples of enzyme-mediated, target amplification strategies that are capable of producing billions of... 

Amplification of nucleic acids also include RNA amplifications. For instance, the heat-shock mRNA (103-mer) in viable Cryptosporidium parvum in water treatment plants was detected after amplification by nucleic acid sequence-based amplification (NASBA). After amplification, a sandwich hybridization assay was subsequently conducted within a PDMS channel [955]. 

Transcription-based amplification methods are modeled after the replication of retroviruses. These methods are known by various names including nucleic acid sequence-based amplification (NASBA), transcription-mediated amplification (TMA)/ and self-sustained sequence repfi-cation (3SR) assays. Isothermal target amplification, using the collective activities of reverse transcriptase, RNase H, and RNA polymerase, is common to these methods. As illustrated in Figure 37-6, the method may be applied to... 

Figure 37-6 Schematic diagram of the nucleic acid sequence-based amplification (NASBA) method applied to single-stranded RNA and double-stranded (ds)DNA.The method is based on an extension of primer I (containing aT7 promoter) by reverse transcriptase (RT), degradation of the RNA strand by RNase H (or heat denaturation for double-stranded DNA), synthesis of the second strand of DNA by reverse transcriptase, and RNA synthesis byT7 RNA polymerase (pol). With RNA synthesis, the system enters the cyclic phase. Solid lines, DNA dashed lines, newly synthesized DNA wavy lines, RNA. (Reprinted by perm/ssion of the publisher from vanGemen B, Kievits T, Nara P, et al. Qualitative and quantitative detection of HIV-1 RNA by nucleic acid sequence-based amplification. AIDS, 7 Suppl 2 SI07-SI 10, 1993. 1993 Rapid Science Publishers.)...

Fox JD, Han S, Samuelson A, Zhang Y, Neale ML, Westmoreland D. Development and evaluation of nucleic acid sequence based amplification (NASBA) for diagnosis of enterovirus infections using the NuchSens Basic Kit. J Chn Virol 2002 24 117-30. 

Deiman, B., van Aarle, P, and Sillekens, P. (2002) Characteristics and applications of nucleic acid sequence-based amplification (NASBA). Mol Biotechnol. 20, 163-179... 

Ch. 36. Nucleic Acid Sequence-Based Amplification (NASBA ),... 

In addition to PCR, there are many other technologies to amplify nucleic acids. For example, ligation-based amplification or ligase chain reaction uses sequence-directed oligonucleotide primers and thermostable DNA ligase to assay point mutations, deletions, or insertions in DNA. Strand-displacement amplification uses the inherent strand-displacement activity of DNA polymerases to conduct DNA amplification at a constant temperature. Transcription-based methods such as nucleic acid sequence-based amplification (NASBA) involve in vitro RNA transcription. NASBA and most other transcription-based... 

NASBA nucleic acid sequence-based amplification... 

RT-PCR, Reverse transcription-polymerase chain reaction NASBA, nucleic acid sequence based amplification. For current FDA listings, see http //www.accessdata.fda.gov/scripts/cdrli/cfdocs/cERL/lLsting.cfiii. 

An isothermal nncleic acid sequence-based amplification (NASBA) assay was optimized to amplify viral RNA of all four dengue virus serotypes by a set of universal primers and to type the amplified products by serotype-specific capture probes. The NASBA assay involved the use of silica to extract viral nucleic acid, which was amplified without thermocycling (Wu et al. 2001a). The main advantage of this assay over a PCR technique is that it is entirely isothermal and is conducted at 41°C. Thus, it would be suitable for epidemiological studies in the field (Wu et al. 2001a). 

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