Human Saliva as a Liquid Biopsy for Detecting the SARS-CoV-2

This invited perspective is being shared as a joint venture from a dental clinician cum researcher and a demanding clinical specialty , as our perspective to collaborate and promote the culture of teamwork. On 31st December 2019, a case of an unknown type of Pneumonia from Wuhan, a city of China, was reported to the World Health Organization (WHO) head office. The cause of this Pneumonia was identified and spread in the whole city within a few days. On 7th Jan 2020, the virus was isolated by a Chinese group of researchers and the virus was named as “Severe Acute Respiratory Syndrome coronavirus 2 (SARS-CoV-2)”, and the illness caused by it is known as “Coronavirus Disease 2019 (COVID-19)”, the digit 19, signifies its year of discovery as 2019. In the meantime, this virus was globally spread by travellers to other parts of the world, and the transmission was confirmed as “human-to-human”. In figure-1, illustration representing the structure of 2019-nCoV, this illustration was created at the Centers for Disease Control and Prevention (CDC), revealing its ultrastructural morphology exhibited by coronaviruses.

Figure 1: Illustration representing SARS-CoV-2 ultrastructural morphology (Courtesy to CDC, image library).

The clinical features of the infected COVID-19 patients include fever, cough, and shortness of breath, headache, nausea, vomiting, and chest pain.1 Only early detection can control this pandemic situation. For that, rapid diagnostic technology was started and reported by taking samples from blood, urine, oral swabs, oropharyngeal swab, and nasopharyngeal swab as well, as its exact source was uncertain.2-4 All sampling is giving good sensitivity toward virus detection in infected patients but not promising for asymptomatic patients. A recently immunological diagnostic method reported detecting COVID-19 from Nasopharyngeal Swab Specimens Using Field-Effect Transistor-Based Biosensor without the pretreatment and labelling.5
All mentioned sampling is invasive or scary to the patients. This needed lot of fresh disposable safety gloves for each patient and personal protective equipment (PPE) for the entire health care professional team involved establishing detection. On 12th F ebruary 2020, a breakthrough was reported from Hong Kong on the detection of SAR-CoV-2 from human saliva.6
In this study, they found a live virus load in the saliva of 12 confirmed infected COVID-19 patients, whereas other samples collected showed insignificant results. This study finding brought a revolution in the field of rapid detection for prevention and controlling the spread of the disease.
After that, many studies reported on the human saliva collection for SARS-CoV-2, show detection in the early stages, so the load on the hospitals and quarantine center will reduce. In the USA, Prof Andrew Brooks from Rutgers University got emergency FDA approval for the saliva testing for SARS-CoV-2. This method is non-invasive, technique – simple, secure, cost-effective and does not require a lot of fresh gloves or PPE for all the healthcare professionals.7
There are a lot of salivary biomarkers reported in the past for the detection and management of oral and systematic diseases such as cardiovascular diseases, arthritis, pulmonary disorders, diabetics, oral cancer, lung cancer, breast cancer, oral lichen planus, dental caries, and periodontal diseases.8-10 Human saliva contains proteins and peptides such as defensins11, cathelicidins12 , histatins13, and many
more for helping as biomarkers for early disease detection.8 By optimizing salivary biomarkers and immunoglobulins on the microfluidic chip technology, and biosensor will help

1. Lecturer and Course Coodinator, Department of Prosthodontics and Dental Implantology, College of Dentistry, King Faisal University.
2. Dean of Dentistry and Professor of Oral & Maxillofacial Surgery, Dow University of Health Sciences DUHS.
   Corresponding author: “Dr. Zohaib Khurshid” < drzohaibkhurshid@gmail.com >