Method Description

Viral DNA is extracted from 0.2 mL of specimen by the MagNA Pure automated instrument (Roche Applied Science). LightCycler polymerase chain reaction (PCR) primers and probes detect target B19 DNA (nonstructural protein). The LightCycler instrument amplifies and monitors by fluorescence the development of target nucleic acid sequences after the annealing step during PCR cycling. This automated PCR system can rapidly detect (30-40 minutes) amplicon development through stringent air-controlled temperature cycling in capillary cuvettes. The detection of amplified products is based on the fluorescence resonance energy transfer (FRET) principle. For FRET product detection, a hybridization probe with a donor fluorophore, fluorescein, on the 3' end is excited by an external light source and emits light that is absorbed by a second hybridization probe with an acceptor fluorophore, LC-Red 640, at the 5' end. The acceptor fluorophore then emits a light of a different wavelength that can be measured with a signal that is proportional to the amount of specific PCR product. Melting curve analysis is performed following PCR amplification. Starting at 45° C, the temperature in the thermal chamber is slowly raised to 80° C and the fluorescence is measured at frequent intervals. Analysis of the PCR amplification and the probe melting curves is accomplished through the use of LightCycler software.(Soares RM, Durigon El, Bersano JG, Richtzenhain LG: Detection of porcine parvovirus DNA by the polymerase chain reaction assay using primers to the highly conserved nonstructural protein gene, NS-1. J Virol Methods. 1999 Mar;78(1-2):191-198)