Testing times

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By Cheaper and more sensitive tests to detect HIV may soon be available, says T.V. Jayan
  • Published 29.10.12

Like in the case of many other diseases, delayed diagnosis can be fatal for those who suffer from the devastating human immunodeficiency virus (HIV). And studies in the past have shown that valuable opportunities for intervention are often missed because the infection stays undetected.

In January 2009, a team of experts from the World Health Organisation (WHO) suggested a voluntary system of annual HIV testing for all adults — followed by antiretroviral treatment for those testing positive — as a strategy to drive the deadly virus into an elimination phase. But this idea of universal HIV testing failed to catch on, probably because of the humongous cost involved.

Today, there are 40 million confirmed HIV cases and an additional 4.3 million cases are added every year. More importantly, many more people are living with and dying of HIV because they were never tested for the infection. One reason for this is that a reliable HIV test costs anywhere between Rs 500 and Rs 750, and a large majority cannot afford them.

The situation may now improve as researchers are developing cheaper and better detection technologies, which are also easier to use, despite being more sophisticated.

For instance, a team of researchers at the Imperial College London, reported yesterday in the journal Nature Nanotechnology that they have developed an ultra-sensitive sensor that would enable doctors to detect the disease in the early stages with the naked eye. The revolutionary sensor technology is 10 times more sensitive than the diagnostic methods currently used for detecting HIV biomarkers. The technology will be particularly beneficial for resource-poor countries where sophisticated equipment for HIV screening is scarce.

“It is vital that patients get periodically tested in order to assess the success of retroviral therapies and check for new cases of infection. Unfortunately, the existing gold standard detection methods can be too expensive to be implemented in parts of the world where resources are scarce,” says Molly Stevens, a materials and bioengineering scientist at Imperial College. She claims that their test is more sensitive, does not require sophisticated instrumentation and is 10 times cheaper, which could allow more tests for better screening.

The sensor detects a biomarker called p24 in blood samples, which indicates HIV infection. The researchers used the same technology for early detection of prostate cancer, indicating it could be harnessed for diagnosing other diseases for which specific biomarkers are known.

The sensor works by analysing blood serum. If the result is positive for p24, there is a reaction that generates irregular clumps of gold nanoparticles, which give off a distinctive blue hue. If the results are negative the nanoparticles separate into ball-like shapes, creating a reddish hue. Both reactions can be easily seen by the naked eye.

More importantly, the sensor is so sensitive that it is able to detect minute levels of the biomarker in samples taken from patients with low viral loads, which are not picked up by existing tests such as the Enzyme-linked Immunosorbent Assay (Elisa) test and the gold standard nucleic acid based test. The new test will enable previously undetectable HIV infections to be picked up, which would mean people could be treated sooner, says Roberto de la Rica, a co-author of the study.

Closer home, a team of Indian researchers has also claimed that it has developed a better HIV screening test which is cheaper and more sensitive, but independent experts are not yet convinced.

The new HIV screening test, developed by researchers led by Prakash P. Bisen, who recently retired as emeritus professor at the Defence Research Development Establishment in Gwalior, uses a cocktail of different HIV biomarkers to improve the sensitivity and specificity of the test. The antigenic cocktail also contains a biomarker specific to a HIV strain found in India. “Inclusion of V3I peptide exclusively extracted from Indian HIV isolates in the cocktail makes the test more sensitive,” says Ram Pramod Tiwari, research scientist at Avantor Performance Materials Limited in New Delhi, and a co-author of the study which appeared in the Journal of Immunological Methods.

However, Udaykumar Ranga, a scientist at the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bangalore, questions the claim saying that the V3 part of the HIV virus that they used as one of the biomarkers is highly problematic as its components mutate fast. “Nearly a third of amino acids present in the V3 loop can differ between strains of HIV, rendering the V3 loop unsuitable as a biomarker,” Ranga argues.