| Summary: | Background & objectives: Polio, measles, rubella, influenza and rotavirus surveillance programmes are of great public health importance globally. Virus isolation using cell culture is an integral part of such programmes. Possibility of unintended isolation of SARS-CoV-2 from clinical specimens processed in biosafety level-2 (BSL-2) laboratories during the above-mentioned surveillance programmes, cannot be ruled out. The present study was conducted to assess the susceptibility of different cell lines to SARS-CoV-2 used in these programmes.
Methods: Replication of SARS-CoV-2 was studied in RD and L20B, Vero/hSLAM, MA-104 and Madin–Darby Canine Kidney (MDCK) cell lines, used for the isolation of polio, measles, rubella, rotavirus and influenza viruses, respectively. SARS-CoV-2 at 0.01 multiplicity of infection was inoculated and the viral growth was assessed by observation of cytopathic effects followed by real-time reverse transcription–polymerase chain reaction (qRT-PCR). Vero CCL-81 cell line was used as a positive control.
Results: SARS-CoV-2 replicated in Vero/hSLAM, and MA-104 cells, whereas it did not replicate in L20B, RD and MDCK cells. Vero/hSLAM, and Vero CCL-81 showed rounding, degeneration and detachment of cells; MA-104 cells also showed syncytia formation. In qRT-PCR, Vero/hSLAM and MA-104 showed 106 and Vero CCL-81 showed 107 viral RNA copies per μl. The 50 per cent tissue culture infectious dose titres of Vero/hSLAM, MA-104 and Vero CCL-81 were 105.54, 105.29 and 106.45/ml, respectively.
Interpretation & conclusions: Replication of SARS-CoV-2 in Vero/hSLAM and MA-104 underscores the possibility of its unintended isolation during surveillance procedures aiming to isolate measles, rubella and rotavirus. This could result in accidental exposure to high titres of SARS-CoV-2, which can result in laboratory acquired infections and community risk, highlighting the need for revisiting biosafety measures in public health laboratories.
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