SARS-associated coronavirus replication in cell lines

Abstract

Given the potential for laboratory-associated severe acute respiratory syndrome-associated coronavirus (SARS-CoV) infections, we must know which cell lines are susceptible to the virus. We investigated 21 cell lines routinely used for virus isolation or research. After infection with SARS-CoV, cells were observed for cytopathic effects, and quantitative real-time polymerase chain reaction was used to measure ongoing viral replication. An indirect immunofluorescence assay was also used as a confirmatory test. The study identified 10 new cell lines capable of supporting the replication of SARS-CoV and confirmed the susceptibility of 4 cell lines previously reported. This study shows that SARS-CoV can be isolated in several cell lines commonly used for diagnostic or research purposes. It also shows that SARS-CoV can achieve high titers in several cell lines, sometimes in the absence of specific cytopathic effects.

Figure 1

Cytopathology of uninfected cells (left column) and the same cells infected in vitro with severe acute respiratory syndrome–associated coronavirus (right column). A) Vero cells day 4 after infection. B) MA-104 cells day 4 after infection. C) Huh-7 cells day 11 after infection. D) pCMK cells day 11 after infection. E) COS cells day 11 after infection. F) MEK cells day 11 after infection.

Figure 2

Cycle threshold (Ct) changes measured by real-time polymerase chain reaction versus days after infection of the indicated cell lines. The cell-free sample had an initial Ct of 31, which rose to 40 by day 11. Reductions in the Ct or flat-line Ct values (e.g., COS cells) indicate replication of the virus. Continued increases in Ct above the initial value of 31 by days 7 and 11 indicate failure to replicate.