Proteins in saliva offer clues about Zika

Crystal Mackay // Western NewsResearch by Dentistry professor Dr. Walter Siqueira, a dental clinician-scientist at the Schulich School of Medicine & Dentistry, is exploring the use of saliva in detecting a person’s exposure to Zika virus.

Western researchers are examining proteins and peptides in saliva in order to detect a person’s exposure to Zika virus. With 70 countries and territories reporting evidence of mosquito-borne Zika virus transmission, there is an increased need for a rapid and effective test for the virus.

By analyzing the saliva of a pregnant mother infected with Zika, and her twins – one born with microcephaly and one without – researchers were able to pinpoint the specific protein signature for Zika that is present in saliva. This signature can then be an effective way to screen for exposure. The researchers have received a provisional U.S. patent to develop a simple device that can be used to identify Zika virus peptides in saliva outside of the laboratory.

They also discovered important clues about how the virus passes from mother to baby, and its role in the development of microcephaly, a birth defect in which a baby’s head and brain are smaller than expected.

“Three months after the babies were born, we collected saliva from the mother and the babies, and the Zika virus peptides were present in the saliva of all three,” said Dentistry professor Dr. Walter Siqueira, a dental clinician-scientist at the Schulich School of Medicine & Dentistry. “This is important because we are the first to identify Zika virus in saliva using proteomics.”

“Discovery of Zika virus in saliva, months after exposure, is quite amazing for our understanding of this infection, but also disconcerting for our public health approach in controlling Zika outbreaks. We need to have better, rapid, and cost effective diagnostic test for screening,” said study co-author Eric Arts, Chair and professor of the Department of Microbiology and Immunology.

The current diagnostic test used by the Centres for Disease Control and Prevention uses blood tests to look for changes to RNA. The drawback to this method is that it is able to detect the virus only up to one week after exposure. Siqueira points out that because proteins are more stable than RNA, saliva proteomics can detect the virus far longer after exposure than with the traditional method.

“Our paper opened the window of detection to more than 20 days, and in this particular case, nine months after exposure,” Siqueira said. “This is possible because we are identifying the proteins and the peptides that come directly from the virus and these are more stable and stay longer in the body than RNA.”

The study, published online last month in the Journal of Dental Research, also suggests a vertical transmission of the virus between mother and baby. It also showed mutations in the amino acid sequence of the peptides that were different for each twin, suggesting that these mutations may play a role in whether or not a baby will develop microcephaly.