Assay Detects Drug-Resistant Strains of HIV

A highly sensitive assay has been developed for the detection of drug-resistant human immunodeficiency virus (HIV) strains.

The parallel allele-specific sequencing (PASS) assay simultaneously analyzes a large number of viral genomes and detects minor drug-resistant populations, between 0.1 and 0.01% of the total population.

The PASS assay applies the polymerase colony (polony) technique, which involves pouring a small amount of sample onto a slide so that the individual DNA samples are separated. The new technique uses a slide that has one polymerase chain reaction (PCR) primer covalently linked to the gel matrix. This means that the PCR products accumulate around individual DNA templates and form distinct spots (polonies) at the amplification sites.

After the amplification the solid phase negative DNA, strands are hybridized to sequencing primers. Single-base extension of these primers with fluorescence-labeled nucleotides allows imaging with a microarray scanner to distinguish between wild type and mutated populations.

The test was so successful that it could identify a single mutated drug resistant virus out of a sample of 10,000 non-mutated viruses.

The assay, developed by scientists from Duke University (Durham, NC, USA), identifies drug-resistant strains of HIV and provides a new way to study the effectiveness of antiviral therapies and predict patient drug response. The implementation of the assay could provide the 40 million worldwide sufferers of HIV new hope of more effective therapies and treatment regimes.

The HIV virus not only reproduces very rapidly, it also mutates very easily. This leads to infected people having many different forms of the virus in their body and a few of these mutations can lead to drug resistance. Feng Gao, M.D. associate professor of medicine at Duke University said, "The test identifies drug-resistant strains of HIV in patients blood systems and could allow clinicians to choose the right drugs to help delay resistance.”

Dr. Gao envisages that is may be possible to turn this into a device for both clinical and research use. The researchers are currently exploring the technique with other pathogens that can develop drug resistance such as in hepatitis B and tuberculosis. "It may also help scientists understand how the constantly evolving virus develops drug resistance,” he said.



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