Other methods for the detection of ligase chain

Other methods for the detection of ligase chain reaction
products in microtiter plates are been also used. LCR assays
have been developed for the detection of viruses such as
HPV, HSV and HIV.
Cycling Probe Technology
Cycling probe technology is a method for detection and
quantification of low amounts of target DNA. The reaction is
carried out at a temperature that allows the chimeric probe to
anneal to the single-stranded target DNA. RNase H, an
enzyme that specifically degrades the RNA portion of the
DNA-RNA hybrids, cuts within the RNA portion of the
chimeric probe, and the shorter probe fragments dissociate
from the target, regenerating the target for further cycling.
The resulting accumulation of probe fragments can be
detected. Since the target DNA is not amplified, this
technique shows low background. Moreover, cycling probe
technology is fast, linear, isothermal and simple compared
with other DNA detection methods.
NEW MOLECULAR TESTS FOR VIROLOGICAL
DIAGNOSIS
Microarrays
A DNA array (or DNA chip) is a collection of spots
attached to a solid support where each spot contains one or
more single-stranded DNA oligonucleotide fragment [26].
High density arrays, that permit attaching hundred or
thousands of oligonucleotides, are referred to as microarrays.
A labeled amplification product is hybridized to the probes,
and hybridization signals are mapped to several positions
within the array. The pattern of hybridization can identify the
sequence of PCR, if the number of probes is sufficiently
large. The results of hybridization between the bound probe
and labeled sequences in the sample applied and tested are
revealed by scanning or imaging the array surface. Confocal
microscopy is used to scan the chip, detecting fluorescent
signals that reveal hybridization at precise locations on the
chip. As many DNA sequences can be present on a slide, it is
possible for microarray analysis to test for multiple viruses
simultaneously.
The first application in diagnostic virology has been for
rapid sequencing to detect HIV mutations associated with
resistance to antiretroviral drugs [27]. Since then, some
research groups have developed microarrays that detect
several viruses such as respiratory viruses [28], hepatitis C
virus [29] and virus causing CNS infection [30].
Multiplexed Microsphere-Based Array
Microsphere-based suspension array technologies, such
as the Luminex
®
xMAP
TM
system, offer a platform for
nucleic acid detection that have some advantages including
rapid data acquisition, excellent sensitivity and specificity
and multiplexed analysis capability [31]. As compared to
planar microarrays, suspension arrays have the advantages of
ease of use, low cost, statistical superiority, faster
hybridization kinetics and more flexibility in array
preparation [31].