A549-hACE2+TMPRSS2 cells, challenged with SARS-CoV-2 lentiviral pseudoparticles that were pre-treated with C1q or C4BP, reduced viral infection by ~60% (Figure 2A) and ~17% (Figure 2B), respectively, compared to the control (A549-hACE2+TMPRSS2 cells + SARS-CoV-2 pseudoparticles). Here, TMPRSS2 is linked to viral infectious disease.