Producing COVID-19 Virus Spike Proteins in TunaCHO

Various versions of COVID-19 Spike proteins were produced in TunaCHO 7-day process and purified. Data shown below are SDS-PAGE images after initial purification. The COVID-19 constructs expressed around 100 mg/L in TunaCHO and formed trimers based on SEC-HPLC, as expected.The furin cleavage site is functional, therefore the S protein is cut into two fragments: S1 and S2. Interestingly enough S1 and S2 appear to still associate after furin cleavage. 

Wild type with furin site removed  (46327)

Prefusion conformation with furin site intact  (46026)

Prefusion conformation with furin site removed  (46328)