CURRENT TEST REGIMEN
Oral fluid testing for HIV is often preferred due to its non-invasiveness, or even required in settings where needles are unavailable or impractical. Unfortunately, current saliva tests take too long after exposure to correctly diagnose new infections. With Stanford and the Alameda County Public Health department, Enable Biosciences is developing a new and more sensitive test for HIV, allowing for earlier detection and treatment of HIV cases to reduce the spread of new infections.
- HIV is most easily transmitted during the early stage
- Oral fluid tests are generally preferred for convenience, but have poor performance in the early stages of infection
- Enable Biosciences’ ADAP technology improves oral fluid testing during early stages of disease
Enable's HIV test is changing the paradigm. Enable, in collaboration with the Alameda County Public Health Laboratory, has developed a test combining the convenience of spitting in a cup with the reliability of blood tests.
It is difficult to detect the small amounts of antibodies present in the saliva of someone with HIV. To accomplish that, the team at Enable took an indirect approach. Instead of looking for the antibodies themselves, they took advantage of what antibodies can do.
The team took advantage of a key feature of antibodies – they have two arms, each of which easily latches onto a virus like HIV. They took bits of HIV and attached them to one or the other half of a piece of DNA. They then added the modified HIV bits into the saliva sample. If the sample contained HIV antibodies, their two arms would grab hold of the tagged HIV, bringing the two halves of the DNA together into a continuous strand. Once the DNA piece is made whole it is easy to detect using standard lab techniques.
That can all be done without requiring a blood sample or much technology to process the samples that are taken. “It’s purposefully low tech,” Bertozzi said.
Although the researchers say it will take more studies to confirm the results, the first experiments show that it works well: the test correctly diagnosed 22 people who took part in an Alameda County screening effort, each of whom had tested positive for HIV using other methods. Importantly the test did not falsely detect HIV in the 22 additional HIV-negative participants.
It may also work earlier compared to other saliva tests, although not earlier than existing blood tests. In a set of eight samples that had produced mixed results with the current standard saliva test, six turned up positive with the new HIV test, and one of those was confirmed using a blood test. Although those results are preliminary, they suggest that the new test is more sensitive and could pick up HIV infection sooner than others.