Fast detection of SARS-CoV-2 in saliva samples – SALFastCov

In view of the growing number of people infected with SARS-CoV-2 around the world and the health impact caused by the Covid-19 pandemic, it is crucial to develop ways to slow down the virus spreading. One of the main weapons to keep the pandemic under control is the use of an efficient and fast method of SARS-CoV-2 detection allowing the isolation of infected people and thus, breaking transmission chains. A high number of tests must be performed and, to reach this goal, the detection method must combine several criteria: reliability, sensitivity, speed and must be performed easily. Thanks to the establishment of a partnership between our laboratory (ENS-Paris-Saclay), the Hospital Bichat-Claude Bernard and the company BIOTEM, we have developed a new fast, sensitive and reliable test for the detection of SARS-CoV-2 viral genome in nasopharyngeal samples. This test is based on an innovative technology using a high-performance lysis buffer associated with amplification of the viral RNA by the LAMP technology. Results are revealed on lateral flow strips, are unambiguous and easy to analyze. The entire test, from sample handling to result analysis , is performed in 40 minutes. In order to offer solutions to increase testing capacity for Covid-19, the first aim of our project is to adapt our test to the detection of viruses in saliva samples. Indeed, saliva tests are not yet very developed but represent a great advantage since sample is easier to perform compared to nasopharyngeal swab. However, the correlation between the viral load in nasopharyngeal swabs and the viral load in saliva is not well known. Our second objective is to determine whether a correlation exists between the viral load in nasopharyngeal and saliva samples in symptomatic and asymptomatic patients.
In conclusion, this project will provide new epidemiological and clinical data by comparing viral loads contained in nasopharyngeal and salivary samples. It will also lead to the development of a new saliva test. Our preliminary results show that the adjustment of the protocol used in our nasopharyngeal test allows the detection of viruses in saliva samples but with reduced sensitivity. Therefore, additional studies, that are planned in this project, must be performed to improve this sensitivity.