A stunning paper by a group of French researchers published in the preprint journal bioRxiv in April 2020 suggests that the unique coronavirus can surviving at high temperatures. This might indicate that laboratory technicians dealing with the infection are at threat of infection.
How was the research study done?
The group led by Teacher Remi Charrel at the Aix-Marseille University in southern France aimed to discover at what temperature the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) might endure. They subjected the viral culture within the host cells, from an African green monkey kidney, to slow heating for an hour, reaching a temperature level of 60 degrees Celsius. The cells used for culture are standard for viral activity. The viral pressure utilized originated from a client with COVID-19 in Berlin, Germany.
Unique Coronavirus SARS-CoV-2: This scanning electron microscope image shows SARS-CoV-2 (round gold objects) emerging from the surface of cells cultured in the laboratory. SARS-CoV-2, likewise known as 2019- nCoV, is the infection that triggers COVID-19 The virus shown was isolated from a patient in the U.S. Credit: NIAID-RML
The research study consisted of 10 protocols for infection inactivation, consisting of 3 lysis buffers and 6 heat inactivation procedures on the supernatant of SARS-CoV-2 cultures.
The contaminated cells were then placed within 2 different types of tubes, to simulate direct exposure to clean and dirty environments in reality. The ‘filthy’ tube contained animal protein pollutants, the aim being to produce a setting somewhat like that discovered in the real world, where an oral swab, for example, may consist of traces of other proteins.
When they tested the residual culture product for any making it through infection, they discovered that the infectivity was markedly reduced, however some pressures might still replicate– adequate to begin another round of infection. While the stress in the clean environment revealed no survival, some strains in the dirty environments endured.
They then went on to warm the culture to nearly 100 degrees Celsius prior to they might validate that the virus had been killed.
Why is this study crucial?
Checking for COVID-19 infection is taking place the world over on a grand scale, due to the rapid spread of the pandemic.
SARS-CoV-2 direct medical diagnosis is based on RNA detection by RT-qPCR. The methods for nucleic acid (NA) extraction use buffers, which formulation plans to obtain high-quality NAs.
Previous studies have dealt with the ability of lysis buffers contributed to the samples in the preliminary action of NA extraction to act as inactivation agents of a number of pathogenic viruses (including coronaviruses). However, discrepant results observed with dissimilar procedures led to questionable conclusions.
Very soon, extensive antibody testing will be utilized to identify if people have already been contaminated. This screening will require using blood samples, which once again indicates that complete viral inactivation needs to be first accomplished.
The most common protocol for infection deactivation is the one-hour 60- degree Celsius heating strategy. In mix with the use of Triton X-100, it has actually been suggested by the Centers for Disease Control and Avoidance (CDC), and used in many laboratories to inactivate viruses with high case casualty ratios, like the Ebola infection.
However, the brand-new study shows that this may be insufficient to eliminate all the virus particles in samples with a high viral load, the researchers say. If just a percentage of the virus exists, though, this protocol will kill a high percentage of the stress, causing nearly complete inactivation.
The investigators discovered that when they warmed the samples to greater temperatures, particularly, 92 degrees Celsius for 15 minutes, viruses were denatured totally, and the sample became non-infectious. This is not a feasible option due to the fact that, at such temperatures, the viral RNA ends up being fragmented, triggering the number of false negatives to increase.
A better way is to combine the more extended lower-heat protocol with chemical sterilization to enhance lab safety while preserving the optimal efficiency of infection detection. The scientists advise using buffers with the chemicals sodium-dodecyl-sulfate and Triton-X100 to get a practically complete reduction in the transmittable virus load. This is equivalent to a less than 6-log drop in the viral load even with big amounts of the infection.
In the words of the authors, “The outcomes provided in this study must help to pick the best-suited protocol for inactivation in order to avoid exposure of laboratory workers in charge of direct and indirect detection of Sars-CoV-2 for diagnostic function.”
Assessment of heating and chemical protocols for inactivating SARS-CoV-2, Boris Pastorino, Franck Touret, Magali Gilles, Xavier de Lamballerie, Remi N. Charrel, bioRxiv 2020.0411036855; doi: https://doi.org/101101/20200411036855