Saliva May Be a Reliable Alternative to Blood for HIV Antibody Testing

HIV-specific antibodies of 3 immunoglobulin (Ig) isotypes are readily found in human saliva, providing a potential second reliable method of detecting the virus that may be used as an painless alternative to a blood draw, according to study results in a recent issue of Journal of Family Medicine and Primary Care. The 3 immunoglobulins are IgA, IgG, and IgM, and their levels are lower in saliva than they are in blood.

In India, in 2017, there was an 11.2% increase (from 62,000 to 69,000) in AIDS-related deaths and a 10.0% increase in new HIV infections, so “HIV infection is still a major health concern,” the authors noted. This study from India comprised 200 patients: 100 patient subjects were in each of the 2 study cohorts, seropositive individuals (57 men, 43 women) and age- and sex-matched HIV-negative healthy controls (55 men, 45 women), and everyone provided saliva and serum samples.

To detect HIV antibodies, the investigators used the enzyme-linked immunosorbent assay (ELISA). Despite the authors pointing out that human saliva is known to inhibit HIV infectivity in vitro, there is a lack of information on oral secretion HIV transmission because the rate of such transmission is so low.

For the saliva samples of the study group, ELISA results were 99% sensitive and 100% specific for HIV antibodies—there was 1 false positive—while for the serum samples, they were 100% for both measures. The mean (SD) patient ages for the study and control groups were 34.14 (11.51) and 31.02 (7.15) years, respectively.

An independent t test that was performed on all of the saliva and serum samples that showed the results were highly significant (P < .05).

The most common modes of HIV acquisition in the study group were unprotected sex (70%), followed by blood transfusion (18%), vertical transmission (9%), and intravenous drug use (3%). Eight-four percent of the women in the study got HIV from their husbands.

“Saliva can be used as alternative to blood for detection of HIV antibodies as saliva collection is painless, non‑invasive, inexpensive, simple, and rapid,” the authors concluded. “Salivary antibody testing may provide better access to epidemic outbreaks, children, large populations, hard‑to‑reach risk groups and may thus play a major role in the surveillance and control of highly infectious diseases.”

For future progress in incorporating saliva as an alternative testing method for HIV antibodies, the authors note the importance of future studies in the area. An important area of study is the salivary leukocyte protease inhibitor enzyme present in saliva, because it prevents HIV from being able to replicate.

More specialized, accurate ELISA tests also need to be developed due to the low viral load present in human saliva and to avoid future inaccurate test results.

Reference

Vohra P, Belkhode V, Nimonkar S, et al. Evaluation and diagnostic usefulness of saliva for detection of HIV antibodies: a cross‑sectional study. J Family Med Prim Care. Published online May 31, 2020. doi:10.4103/jfmpc.jfmpc_138_20