Nav: Home

A better HIV test

January 22, 2018

Public health officials have a tough choice to make when it comes to screening people for HIV: administer a reliable blood test that can detect infections early on, but that few people will volunteer for, or give people a convenient test using saliva that is less reliable during the first stages of infection.

A new test could change that. Developed by Stanford chemists in collaboration with the Alameda County Public Health Laboratory, the test combines the convenience of spitting in a cup with the reliability of blood tests, they report in the January 22 edition of the Proceedings of the National Academy of Sciences.

"The earlier you can detect, the better, because people can infect other people," said Carolyn Bertozzi, the Anne T. and Robert M. Bass Professor in the School of Humanities and Sciences and a professor of chemistry. "Every day that goes by that a person's behavior is not modified based on their HIV status is a day that they could be infecting other people, especially for young people," said Bertozzi, who is also a faculty fellow of Stanford ChEM-H and a member of Stanford Bio-X.

A brief history of HIV testing

By far the most common way to test for HIV infection is to look in a blood sample for antibodies, proteins that the immune system custom-builds to attack the virus and fight back against infection. That test is far more convenient than a direct search for the virus, in part because antibodies are relatively abundant in the bloodstream after the early stages of infection.

Yet there is a major drawback, especially for public health officials and researchers who want - sometimes need - to get a lot of people tested quickly to help contain the spread of the disease: needles.

"There's a lot of populations you just can't reach out to by blood tests," said Cheng-ting "Jason" Tsai, the lead author on the new paper and a graduate student in Bertozzi's lab. "But if you were to do oral fluid, then all of sudden you open up a brand new population that was not otherwise accessible to you."

But oral fluid tests have their own problems. While there are HIV antibodies in saliva, they do not accumulate at the levels they do in blood, or at the same speed - meaning that there just aren't that many present, especially early on.

By the time oral fluid tests can reliably detect HIV, Bertozzi said, "you've waited a long time" - and in that time, the infection could spread.

Translating HIV

The team's job, then, was to figure out how to make it easier to detect the small amount of antibodies present in the saliva of someone with HIV. To do that, they took an indirect approach. Instead of looking for the antibodies themselves, they looked for what antibodies could 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.

"Our hope is that we can get an earlier read than the present oral test because the sensitivity is better," Bertozzi said. Beyond HIV, she and Tsai said, the same principles may be useful for allergy testing and screening for typhoid and tuberculosis infection. The team is also investigating the method as a way to test the efficacy of measles vaccination efforts, Bertozzi said.
-end-
Bertozzi is also a member of the Child Health Research Institute, the Stanford Cancer Institute and the Stanford Neurosciences Institute. The research was supported by grants from the Stanford Predictive and Diagnostics Accelerator, the National Science Foundation and the National Institutes of Health.

Stanford University

Related Hiv Articles:

The Lancet HIV: Study suggests a second patient has been cured of HIV
A study of the second HIV patient to undergo successful stem cell transplantation from donors with a HIV-resistant gene, finds that there was no active viral infection in the patient's blood 30 months after they stopped anti-retroviral therapy, according to a case report published in The Lancet HIV journal and presented at CROI (Conference on Retroviruses and Opportunistic Infections).
Children with HIV score below HIV-negative peers in cognitive, motor function tests
Children who acquired HIV in utero or during birth or breastfeeding did not perform as well as their peers who do not have HIV on tests measuring cognitive ability, motor function and attention, according to a report published online today in Clinical Infectious Diseases.
Efforts to end the HIV epidemic must not ignore people already living with HIV
Efforts to prevent new HIV transmissions in the US must be accompanied by addressing HIV-associated comorbidities to improve the health of people already living with HIV, NIH experts assert in the third of a series of JAMA commentaries.
The Lancet HIV: Severe anti-LGBT legislations associated with lower testing and awareness of HIV in African countries
This first systematic review to investigate HIV testing, treatment and viral suppression in men who have sex with men in Africa finds that among the most recent studies (conducted after 2011) only half of men have been tested for HIV in the past 12 months.
The Lancet HIV: Tenfold increase in number of adolescents on HIV treatment in South Africa since 2010, but many still untreated
A new study of more than 700,000 one to 19-year olds being treated for HIV infection suggests a ten-fold increase in the number of adolescents aged 15 to 19 receiving HIV treatment in South Africa, according to results published in The Lancet HIV journal.
Starting HIV treatment in ERs may be key to ending HIV spread worldwide
In a follow-up study conducted in South Africa, Johns Hopkins Medicine researchers say they have evidence that hospital emergency departments (EDs) worldwide may be key strategic settings for curbing the spread of HIV infections in hard-to-reach populations if the EDs jump-start treatment and case management as well as diagnosis of the disease.
NIH HIV experts prioritize research to achieve sustained ART-free HIV remission
Achieving sustained remission of HIV without life-long antiretroviral therapy (ART) is a top HIV research priority, according to a new commentary in JAMA by experts at the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health.
First ever living donor HIV-to-HIV kidney transplant
For the first time, a person living with HIV has donated a kidney to a transplant recipient also living with HIV.
The Lancet HIV: PrEP implementation is associated with a rapid decline in new HIV infections
Study from Australia is the first to evaluate a population-level roll-out of pre-exposure prophylaxis (PrEP) in men who have sex with men.
Researchers date 'hibernating' HIV strains, advancing BC's leadership in HIV cure research
Researchers have developed a novel way for dating 'hibernating' HIV strains, in an advancement for HIV cure research.
More HIV News and HIV Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Listen Again: Reinvention
Change is hard, but it's also an opportunity to discover and reimagine what you thought you knew. From our economy, to music, to even ourselves–this hour TED speakers explore the power of reinvention. Guests include OK Go lead singer Damian Kulash Jr., former college gymnastics coach Valorie Kondos Field, Stockton Mayor Michael Tubbs, and entrepreneur Nick Hanauer.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.