title: Enhancement of antiviral activity of collectin trimers through cross-linking and mutagenesis of the carbohydrate recognition domain.
abstract: Surfactant protein D (SP-D) plays important roles in innate defense against respiratory viruses [including influenza A viruses (IAVs)]. Truncated trimers composed of its neck and carbohydrate recognition domains (NCRDs) bind various ligands; however, they have minimal inhibitory activity for IAV. We have sought to find ways to increase the antiviral activity of collectin NCRDs. Cross-linking of the SP-D NCRD with nonblocking monoclonal antibodies (mAbs) markedly potentiates antiviral activity. In the present report, we demonstrate that F(ab')2 [but not F(ab')1] fragments of a cross-linking mAb have similar effects. Hence, cross-linking activity, but not the Fc domain of the mAb, is needed for increased antiviral activity. In contrast, the Fc domain of the mAb was important for increasing viral uptake or respiratory burst responses of human neutrophils. Our NCRD constructs contain an S protein binding site. Herein, we show that a multivalent S protein complex caused cross-linking and also increased the antiviral activity of NCRDs. NCRDs of conglutinin and CL43 had greater intrinsic antiviral activity than those of SP-D or mannose-binding lectin. Based on motifs found in these serum collectins, we have constructed mutant versions of the human SP-D NCRD that have increased antiviral activity. These mutant NCRDs also had potentiated activity after cross-linking with F(ab')2 fragments or S protein complexes. Hence, the antiviral activity of NCRDs can be increased by 2 distinct, complementary strategies, namely cross-linking of NCRDs through various means and mutagenesis of CRD residues to increase viral binding. These findings may be relevant for antiviral therapy.
authors.affiliation: Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA.
authors.forename: Mitchell R
authors.initials: MR
authors.lastname: White
authors.forename: Patrick
authors.initials: P
authors.lastname: Boland
authors.forename: Tesfaldet
authors.initials: T
authors.lastname: Tecle
authors.forename: Donald
authors.initials: D
authors.lastname: Gantz
authors.forename: Grith
authors.initials: G
authors.lastname: Sorenson
authors.forename: Ida
authors.initials: I
authors.lastname: Tornoe
authors.forename: Uffe
authors.initials: U
authors.lastname: Holmskov
authors.forename: Barbara
authors.initials: B
authors.lastname: McDonald
authors.forename: Erika C
authors.initials: EC
authors.lastname: Crouch
authors.forename: Kevan L
authors.initials: KL
authors.lastname: Hartshorn
mesh_terms: D000911:Antibodies, Monoclonal / Q000378:metabolism; D000998:Antiviral Agents / Q000276:immunology; D037222:Collectins / Q000276:immunology / Q000378:metabolism*; D003432:Cross-Linking Reagents / Q000378:metabolism; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007113:Immunity, Innate; D007128:Immunoglobulin Fragments / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009980:Influenza A virus / Q000276:immunology* / Q000472:pathogenicity; D007251:Influenza, Human / Q000235:genetics / Q000276:immunology* / Q000378:metabolism / Q000635:transmission; D008264:Macrophages / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000821:virology; D016297:Mutagenesis, Site-Directed; D009504:Neutrophils / Q000276:immunology / Q000378:metabolism / Q000473:pathology / Q000821:virology; D015202:Protein Engineering; D054730:Protein Interaction Domains and Motifs / Q000235:genetics; D055503:Protein Multimerization / Q000276:immunology; D037663:Pulmonary Surfactant-Associated Protein D / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000235:genetics
chemical_list: D000911:Antibodies, Monoclonal; D000998:Antiviral Agents; D037222:Collectins; D003432:Cross-Linking Reagents; D019267:Hemagglutinin Glycoproteins, Influenza Virus; D007128:Immunoglobulin Fragments; D037663:Pulmonary Surfactant-Associated Protein D; D011993:Recombinant Fusion Proteins