New saliva-based antibody test for SARS-CoV-2 highly accurate in initial study

November 13, 2020

A new saliva-based test developed by a team at Johns Hopkins Bloomberg School of Public Health has been found to accurately detect the presence of antibodies to SARS-CoV-2, the virus that causes COVID-19, from small samples of saliva, according to a study led by Bloomberg School researchers. Such tests, the results of which can be obtained in a matter of hours, are seen as potential alternatives to blood-sample antibody tests for research and clinical use.

The test is based on multiple fragments, or "antigens," from the SARS-CoV-2 coronavirus, mostly from its outer spike and nucleocapsid proteins. In the study, the researchers found that their test detected antibodies to several of these antigens in saliva samples from all 24 participants who had confirmed SARS-CoV-2 exposure and whose symptoms had begun more than two weeks prior to the test. The test also reliably yielded negative results for saliva samples that had been collected from people prior to the COVID-19 pandemic.

The study appears online in the Journal of Clinical Microbiology.

"If our saliva-based assay's accuracy is borne out in larger studies, this noninvasive approach could make it easier to identify, at a population level, who has already had a SARS-CoV-2 infection and where gaps in seropositivity remain heading into the winter and beyond," says study senior author Christopher D. Heaney, PhD, MS, an associate professor with appointments in the departments of Environmental Health and Engineering, Epidemiology, and International Health at the Bloomberg School. "This could inform targeted vaccination efforts and, after vaccines start to roll out, help figure out how long vaccine-induced antibodies last--all without repeated, invasive blood draws," Heaney says.

The pandemic spread of SARS-CoV-2 has officially caused over 40 million infections and more than 1 million deaths worldwide. Many epidemiologists suspect that the actual spread of the virus has been much more extensive, but that and many other questions about the pandemic's extent and dynamics have so far been difficult or impossible to answer specifically. A relatively quick, inexpensive, noninvasive, and highly accurate antibody test could make such research much easier, however.

Heaney and colleagues previously have invented accurate saliva-based antibody tests for other disease-causing viruses including the enteric pathogen norovirus and liver-infecting hepatitis E virus.

Early in the pandemic, the research team developed a saliva-based test for SARS-CoV-2 antibodies, using a panel of 12 known viral antigens that are already used for blood-based antibody tests. Saliva samples for the test are collected by rubbing a sponge between people's teeth and gums, where saliva is known to be particularly enriched with antibodies.

That the test detected antibodies to several SARS-CoV-2 antigens in saliva samples from all 24 people who had confirmed SARS-CoV-2 exposure and whose symptoms had arisen more than two weeks before the test showed that the test could be very sensitive--that is, capable of identifying positive results.

The experiments also showed that the test could be highly specific--that is, capable of identifying those without the antibodies with a low rate of "false positives." In a set of 134 saliva samples that had been collected from people long before the COVID-19 pandemic--and thus presumed to be free of SARS-CoV-2 antibodies--several antigens in the test gave negative results in all but a few cases. Antibodies to one viral antigen seemed particularly specific: The scientists found negative results for it in all 134 of the pre-COVID-19 samples.

Saliva-based testing for immunoglobulin G antibodies to SARS-CoV-2 appeared to be just as sensitive and specific as blood-based serological testing. After SARS-CoV-2 infection, IgG antibodies typically elevate around day 10 after symptom onset, and these antibodies spill over from the blood into saliva.

The experiments on the whole have suggested that people who become infected with SARS-CoV-2 develop detectable antibodies in saliva at roughly the same time as they do in blood, about 10 days after COVID-19 symptom onset. The researchers expect that with an optimal algorithm that integrates results for just a few especially sensitive and specific antigens, their saliva-based test may be able to reliably detect SARS-CoV-2 antibodies starting around that same 10-day mark, but not earlier.

Since submitting their paper several months ago, Heaney and colleagues have been refining the test with experiments on thousands more saliva samples. They expect that their saliva-based test will be useful for future research applications, especially large-scale or longitudinal studies for which invasive and potentially painful blood-based tests could be problematic. For example:The researchers also believe that their test is sensitive and specific enough to have potential use in clinical settings, such as screening individuals for prior SARS-CoV-2 exposures before they receive a vaccine or undergo some other medical procedure.

For clinical applications, the test would need Food and Drug Administration approval--at least emergency-use authorization--and Heaney says that with this goal in mind he and his colleagues are initiating discussions with the agency.
"COVID-19 serology at population scale: SARS-CoV-2-specific antibody responses in saliva" was authored by Nora Pisanic, Pranay Randad, Kate Kruczynski, Yukari C. Manabe, David L. Thomas, Andrew Pekosz, Sabra L. Klein, Michael J. Betenbaugh, William A. Clarke, Oliver Laeyendecker, Patrizio P. Caturegli, Benjamin Larman, Barbara Detrick, Jessica Fairley, Amy Sherman, Nadine Rouphael, Srilatha Edupuganti, Douglas Granger, Steve Granger, Matthew Collins, and Christopher D. Heaney.Support for the research was provided by the Johns Hopkins COVID-19 Research Response Program, the FIA Foundation, the GRACE Communications Foundation, the National Institute of Allergy and Infectious Diseases (R21AI139784, R43AI141265, R01AI130066, HHS N2772201400007C), the National Institute of Environmental Health Sciences (R01ES026973), and the National Institutes of Health (U24OD023382).

Johns Hopkins University Bloomberg School of Public Health

Related Public Health Articles from Brightsurf:

COVID-19 and the decolonization of Indigenous public health
Indigenous self-determination, leadership and knowledge have helped protect Indigenous communities in Canada during the coronavirus disease 2019 (COVID-19) pandemic, and these principles should be incorporated into public health in future, argue the authors of a commentary in CMAJ (Canadian Medical Association Journal)

Public health consequences of policing homelessness
In a new study examining homelessness, researchers find that policy such a lifestyle has massive public health implications, making sleeping on the street even MORE unhealthy.

Electronic health information exchange improves public health disease reporting
Disease tracking is an important area of focus for health departments in the midst of the COVID-19 pandemic.

Pandemic likely to cause long-term health problems, Yale School of Public Health finds
The coronavirus pandemic's life-altering effects are likely to result in lasting physical and mental health consequences for many people--particularly those from vulnerable populations--a new study led by the Yale School of Public Health finds.

The Lancet Public Health: US modelling study estimates impact of school closures for COVID-19 on US health-care workforce and associated mortality
US policymakers considering physical distancing measures to slow the spread of COVID-19 face a difficult trade-off between closing schools to reduce transmission and new cases, and potential health-care worker absenteeism due to additional childcare needs that could ultimately increase mortality from COVID-19, according to new modelling research published in The Lancet Public Health journal.

The Lancet Public Health: Access to identification documents reflecting gender identity may improve trans mental health
Results from a survey of over 20,000 American trans adults suggest that having access to identification documents which reflect their identified gender helps to improve their mental health and may reduce suicidal thoughts, according to a study published in The Lancet Public Health journal.

The Lancet Public Health: Study estimates mental health impact of welfare reform, Universal Credit, in Great Britain
The 2013 Universal Credit welfare reform appears to have led to an increase in the prevalence of psychological distress among unemployed recipients, according to a nationally representative study following more than 52,000 working-age individuals from England, Wales, and Scotland over nine years between 2009-2018, published as part of an issue of The Lancet Public Health journal on income and health.

BU researchers: Pornography is not a 'public health crisis'
Researchers from the Boston University School of Public Health (BUSPH) have written an editorial in the American Journal of Public Health special February issue arguing against the claim that pornography is a public health crisis, and explaining why such a claim actually endangers the health of the public.

The Lancet Public Health: Ageism linked to poorer health in older people in England
Ageism may be linked with poorer health in older people in England, according to an observational study of over 7,500 people aged over 50 published in The Lancet Public Health journal.

Study: Public transportation use linked to better public health
Promoting robust public transportation systems may come with a bonus for public health -- lower obesity rates.

Read More: Public Health News and Public Health Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to