This study provides quantitative data on the comparative replication capacity and immune activation of SARS-CoV-2 versus SARS-CoV infection in human lung tissue, providing insight on why it is more infections, bur provokes less of a response in patients.

COVID-19 spreads easily, but we don’t completely understand the underlying mechanism confers its high transmissibility and asymptomatic infections. Researchers investigated the replication, cell tropism, and immune activation profile of SARS-CoV-2 infection in human lung tissues compared to SARS-CoV.

They found that SARS-CoV-2 both infected and replicated in human lung tissue more efficiently than SARS-CoV. In 48 hours, SARS-CoV-2 generated more than three times the infectious virus particles than SARS-CoV. However, despite its more efficient replication, SARS-CoV-2 did not significantly induce types I, II, or III interferons in the infected human lung tissue. Further, SARS-CoV upregulated the expression of 85% of representative pro-inflammatory cytokines/chemokines, while SARS-CoV-2 only upregulated 38% of them.