Scientific Reports · 8 authors, 2 centres
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This study compared the efficiency of culturing live SARS-CoV-2 from clinical specimens, finding that the virus was isolated significantly less often from saliva than from nasal/nasopharyngeal swabs, even with similar viral genome levels. The lower efficiency from saliva was linked to inhibitory substances like lactoferrin and amylase.
The study evaluated the efficiency of isolating viable SARS-CoV-2 from nasal/nasopharyngeal swab and saliva specimens using cell culture. The primary result was that viral isolation efficiency was significantly lower from saliva specimens compared to nasal/nasopharyngeal swabs, particularly when the PCR cycle threshold (Ct) value was 30 or less. This difference was observed for Wuhan, Delta, and Omicron variants, but not for the Alpha variant. Using simulated specimens, the authors confirmed that saliva itself, not prior immunity, reduced virus recovery. Mechanistic experiments with pseudotyped viruses identified lactoferrin and amylase as saliva components that inhibit SARS-CoV-2 infection in vitro. Limitations include the relatively small number of specimens for some variant and Ct value groups, and the need for further verification. The findings suggest that infectious viral particles may be more abundant in the upper respiratory tract than in saliva, and that saliva contains factors with anti-SARS-CoV-2 activity.
