Heat Inactivation of Different Types of SARS-CoV-2 Samples: What Protocols for Biosafety, Molecular Detection and Serological Diagnostics?

Abstract

<jats:p>Standard precautions to minimize the risk of SARS-CoV-2 transmission implies that infected cell cultures and clinical specimens may undergo some sort of inactivation to reduce or abolish infectivity. We evaluated three heat inactivation protocols (56 °C-30 min, 60 °C-60 min and 92 °C-15 min) on SARS-CoV-2 using (i) infected cell culture supernatant, (ii) virus-spiked human sera (iii) and nasopharyngeal samples according to the recommendations of the European norm NF EN 14476-A2. Regardless of the protocol and the type of samples, a 4 Log10 TCID50 reduction was observed. However, samples containing viral loads &gt; 6 Log10 TCID50 were still infectious after 56 °C-30 min and 60 °C-60 min, although infectivity was &lt; 10 TCID50. The protocols 56 °C-30 min and 60 °C-60 min had little influence on the RNA copies detection, whereas 92 °C-15 min drastically reduced the limit of detection, which suggests that this protocol should be avoided for inactivation ahead of molecular diagnostics. Lastly, 56 °C-30 min treatment of serum specimens had a negligible influence on the results of IgG detection using a commercial ELISA test, whereas a drastic decrease in neutralizing titers was observed.</jats:p>

Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators

“…For SARS-CoV-2, after 30 min at 56 °C, the magnitude of the virus titre reduction was 3.0 log 10 [ 33 ], ≥4.6 log 10 [ 37 ], ≥5.0 log 10 [ 66 ], ≥5.9 log 10 [ 67 ], 5.0–6.0 log 10 [ 69 ], and 7.0 log 10 [ 70 ]. At 60 °C, there was a 7.0 log 10 reduction after 15 min [ 70 ], and a 5.0–6.0 log 10 reduction (complete inactivation) in clinical samples after 60 min [ 69 ] ( Table 5 ). According to an unpublished study [ 67 ], at 65 °C, SARS-CoV-2 was inactivated (≥5.5 log 10 reduction) in cell culture, nasopharyngeal samples, and serum after 15, 10, and 10 min, respectively ( Table 5 ).…”

“…According to an unpublished study [ 67 ], at 65 °C, SARS-CoV-2 was inactivated (≥5.5 log 10 reduction) in cell culture, nasopharyngeal samples, and serum after 15, 10, and 10 min, respectively ( Table 5 ). The efficacy of heat treatment against SARS-CoV-2 was also evaluated at other temperatures that varied among studies, including 70 °C [ 37 , 39 , 68 ], 92 °C [ 69 ], 95 °C [ 67 ], and 98 °C [ 66 ] ( Table 5 ).…”

“…Overall, heat treatment at 60 °C for 60 min would lead to SARS-CoV-1 inactivation according to six studies [ 31 , 34 , 35 , 45 , 50 , 65 ] (~3.5–8.0 log 10 reductions in a variety of media), and to SARS-CoV-2 inactivation as per six studies [ 33 , 37 , 66 , 67 , 69 , 70 ] (~4.6–7.0 log 10 reduction) ( Table 5 ). However, one study showed residual SARS-CoV-1 infectivity until 90 min at 65 °C [ 46 ].…”

Analysis of Inactivation of SARS-CoV-2 by Specimen Transport Media, Nucleic Acid Extraction Reagents, Detergents, and Fixatives

“…Furthermore, the precise composition of many commercial reagents is proprietary, preventing ingredient-based inference of inactivation efficacy between reagents. Some limited preliminary data on SARS-CoV-2 inactivation by heat (14,15) or chemical (16)(17)(18)(19)(20)(21) Vero E6 cells at a multiplicity of infection (MOI) of 0.001, in the presence of 5% FCS. Cell culture supernatants were collected 72 hours post infection, clarified for 10 mins at 3000 × g, aliquoted and stored at -80°C until required.…”

Decontamination of SARS-CoV-2 and Other RNA Viruses from N95 Level Meltblown Polypropylene Fabric Using Heat under Different Humidities

“… 24 Heating influenza virus at 60 °C for 15 min at 25% relative humidity (RH) resulted in a decrease of 1 log 10 -fold in viral titers, whereas the same heating process at 50% RH reduced viral titers by a factor of 4 log 10 -fold. 24 Although SARS-CoV-2 has been shown to be efficiently inactivated by heat in solution, 25 a comparison of inactivation by dry or moist heat when the virus is dried on surfaces has not been carried out, although one study found that stability of SARS-CoV-2 is lower in high humidity at common environmental temperatures (≤38 °C). 26 …”