Human coronavirus NL63 also known as HCoV-NL63 is a type of coronavirus that was identified in 2004. Among the associated diseases are mild to moderate upper respiratory tract infections, bronchiolitis, severe lower respiratory tract infection and croup. Coronavirus NL63 appears mainly in young children, the elderly and immunocompromised patients with acute respiratory illness. Coronavirus NL63 has a seasonal association in temperate climates. Coronavirus NL63 is not an emerging virus, but rather one that continually circulates the human population. Transmission of HCoV-NL63 is likely through droplet expulsion from the respiratory tract, which may be cottages when close personal contact occurs. Coronavirus NL63 is able to endure for up to7 days in respiratory secretions and remains infective at room temperature. Once the virus has entered the host it binds to cellular receptors using spike proteins, similar to those found in HIV-1. Coronavirus NL63 is able to use Angiotensin-converting enzyme 2 (ACE2) as an entry receptor to target cells. Since coronavirus NL63 is a positive single-stranded RNA virus, the processes of replication via transcription and translation can be carried out in the cytoplasm of the infected cell.
Recombinant Coronavirus NL63 c-terminal nucleoprotein produced in E. coli contains 221-340 amino acids and fused to a 6 a.a. His tag a c-terminal having a total of 130 a.a..