SIGLEC1 and infection: We detected increasing levels of total SARS-CoV-2 N transcripts at early time points (2–6 hpi) in THP1/PMA macrophages expressing CD169, ACE2, or both CD169 and ACE2, whereas parental THP1/PMA macrophages showed no significant increase in viral N RNA levels compared to mock infection controls (Fig 4D).