SP-D can neutralize influenza virus through occupying the HA binding site (43). SP-D limits RSV infection by interacting with virus through attachment to the F and G proteins (44). SP-D limits coronavirus infection by binding HCoV-229E virions (40). SP-D limits SARS coronavirus by binding to the heavily glycosylated S protein (45). SP-D can neutralize SARS-CoV-2 through interaction with the S protein (41). rfhSP-D can compete with ACE-2 for binding to the S1 spike protein subunit of SARS-CoV-2 (16). SP-A can restrict HIV infection via binding to glycoprotein (gp)120 (46). This evidence concerns the gene ACE2 and HIV infectious disease.