New HIV test delivers accurate results in minutes

A team of Northwestern scientists spanning disciplines have developed new technology that could lead to the creation of a rapid point-of-care test for HIV infection competitive with traditional lab-based HIV testing in a fraction of the time and without the need for a stressful wait while results are processed or confirmed in a clinical laboratory.

The background

HIV-diagnostic technology traditionally relied on the detection of HIV-specific antibodies that form several weeks after infection. This has limited their use in early detection, complicating patient care and HIV prevention efforts. Newer tests that detect both HIV antibodies and the p24 antigen (an earlier marker of HIV infection) are now the gold standard for diagnosis, but require clinical labs to run results, contributing to longer processing times, higher costs and the need for multiple patient visits.

The new test

The technology, described in a study in the journal Biosensors and Bioelectronics, uses a nanomechanical platform and tiny cantilevers to detect multiple HIV antigens at high sensitivity in a matter of minutes. These silicon cantilevers are cheap and easy to mass produce and can be readily equipped with a digital readout. Built into a solar-powered device, this technology could be taken to hard-to-reach parts of the world where early detection remains a challenge to deliver fast interventions to vulnerable populations without waiting for a lab.

“We hope this technology will lead to the development of new point-of-care diagnostics for HIV to improve patient health and help bring an end to this epidemic,” said Northwestern virologist and co-author of the study, Judd F. Hultquist.

After proving its efficacy in testing for both the SARS-CoV-2 virus that causes COVID-19, and now HIV, the team is confident that the biosensor will continue to prove effective when testing for additional diseases. A potential next target, they say, could be measles, another infection in desperate need of point-of-care interventions as cases rise across multiple U.S. states.

The team was led by co-corresponding authors Vinayak Dravid, a materials engineer, Hultquist, a virologist, and co-author Gajendra Shekhawat, a micro- and nanofabrication expert in the Dravid Lab.

How it works

Adapting the biosensor to detect HIV was a unique challenge.

“When we first developed the microcantilever technology 20 years ago, I realized that this technology is so generally applicable,” Dravid said. “It is a very powerful tool that depends on three basic things: sensitivity, antigen-antibody affinity and specificity. This is where HIV comes in, because HIV is so pernicious that it mutates so there is no unique antibody. We had to figure out how to overcome that challenge.”

Beginning with pure samples of the p24 antigen, the team applied layers of antibodies onto each “finger” of the gold-coated microcantilever to measure how strongly p24 bonded to the surface, which would cause the cantilever to bend a measurable and quantifiable amount.

After this proof-of-concept, the team introduced human blood samples, which are much more complex than purified samples. The sensor continued to bend only in samples where p24 was present, demonstrating high specificity.

Finally, the scientists added two antibodies (ANT-152 and C65690M) to different “fingers” of the microcantilever to more broadly cover all HIV subtypes.

“This allowed accurate detection across diverse HIV-1 subtypes, ensuring reliability in global settings.” Shekhawat said.

Even in very low concentrations, the test accurately responded when antigens specific to HIV were introduced.

Future paths

To streamline diagnostics and enable immediate medical care, the team envisions developing a point-of-care test simultaneously detecting HIV, hepatitis B and hepatitis C antigens, acknowledging the higher prevalence of hepatitis co-infections in people living with HIV that can lead to severe liver complications if left untreated.