Salivary agglutinin and lung scavenger receptor cysteine-rich glycoprotein 340 have broad anti-influenza activities and interactions with surfactant protein D that vary according to donor source and sialylation.

We previously found that scavenger receptor cysteine-rich gp-340 (glycoprotein-340), isolated from lung or saliva, directly inhibits human IAVs (influenza A viruses). We now show that salivary gp-340 has broad antiviral activity against human, equine and porcine IAV strains. Although lung and salivary gp-340 are identical in protein sequence, salivary gp-340 from one donor had significantly greater antiviral activity against avian-like IAV strains which preferentially bind sialic acids in alpha(2,3) linkage.

Cooperative anti-influenza activities of respiratory innate immune proteins and neuraminidase inhibitor.

The surfactant collectins, surfactant proteins A and D (SP-A and D), and scavenger receptor-rich glycoprotein 340 (gp340) inhibit influenza A virus (IAV) in the following order of potency: SP-D>gp340>SP-A. SP-D binds in a calcium-dependent manner to carbohydrate attachments on the viral hemagglutinin (HA) and neuraminidase (NA). By contrast, gp340 and SP-A act like mucins in that they provide sialic acid ligands that bind to the viral HA.