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Friday, October 23, 2015

Rapid, sensitive test for HIV mutations

Tests that can distinguish whether HIV-positive people are infected with a drug-resistant strain or a non-resistant strain allow patients to get the most effective treatment as quickly as possible.
Published in the Journal of Molecular Diagnostics, researchers describes a new method that works faster and more sensitively in lab testing than the current standard technologies.
The main advance enabling that improved performance is that the system operates directly on the virus' more readily available RNA rather than requiring extra, potentially error-prone steps to examine DNA derived from RNA. In a single tube, the system can first combine two engineered probes (ligation) if a mutation is present and then make many copies of those combined probes (amplification) for detection.
The experiments reported in the paper show that the LRA (ligation on RNA amplification) test was sensitive enough to find a commonly sought K103N mutation in concentrations as low as one mutant per 10,000 strands of "normal" viral RNA. The LRA detection worked within two hours, while alternative technologies such as ASPCR or pyrosequencing, can take as long as eight.
LRA works by sending in many copies of a pair of short engineered probes of genetic material to complement the RNA in the HIV sample. Under optimized conditions, those pairs that perfectly match the target HIV RNA containing a mutation that causes drug resistance can rapidly become fused together, or ligated, by an enzyme. If there is a single nucleotide difference, the pair won't fuse…