title: Immunization against proprotein convertase subtilisin-like/kexin type 9 lowers plasma LDL-cholesterol levels in mice.
abstract: Successful development of drugs against novel targets crucially depends on reliable identification of the activity of the target gene product in vivo and a clear demonstration of its specific functional role for disease development. Here, we describe an immunological knockdown (IKD) method, a novel approach for the in vivo validation and functional study of endogenous gene products. This method relies on the ability to elicit a transient humoral response against the selected endogenous target protein. Anti-target antibodies specifically bind to the target protein and a fraction of them effectively neutralize its activity. We applied the IKD method to the in vivo validation of plasma PCSK9 as a potential target for the treatment of elevated levels of plasma LDL-cholesterol. We show that immunization with human-PCSK9 in mice is able to raise antibodies that cross-react and neutralize circulating mouse-PCSK9 protein thus resulting in increased liver LDL receptor levels and plasma cholesterol uptake. These findings closely resemble those described in PCSK9 knockout mice or in mice treated with antibodies that inhibit PCSK9 by preventing the PCSK9/LDLR interaction. Our data support the IKD approach as an effective method to the rapid validation of new target proteins.
authors.affiliation: Biotechnology Department, Istituto di Ricerche di Biologia Molecolare P. Angeletti, I-00040 Pomezia (Roma), Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Fattori
authors.forename: Manuela
authors.initials: M
authors.lastname: Cappelletti
authors.forename: Paola
authors.initials: P
authors.lastname: Lo Surdo
authors.forename: Alessandra
authors.initials: A
authors.lastname: Calzetta
authors.forename: Claus
authors.initials: C
authors.lastname: Bendtsen
authors.forename: Yan G
authors.initials: YG
authors.lastname: Ni
authors.forename: Shilpa
authors.initials: S
authors.lastname: Pandit
authors.forename: Ayesha
authors.initials: A
authors.lastname: Sitlani
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mesiti
authors.forename: Andrea
authors.initials: A
authors.lastname: Carfí
authors.forename: Paolo
authors.initials: P
authors.lastname: Monaci
mesh_terms: D000818:Animals; D000906:Antibodies / Q000276:immunology; D008078:Cholesterol, LDL / Q000097:blood*; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007114:Immunization; D008099:Liver / Q000378:metabolism; D051379:Mice; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases / Q000276:immunology* / Q000378:metabolism; D011973:Receptors, LDL / Q000378:metabolism; D012697:Serine Endopeptidases / Q000276:immunology* / Q000378:metabolism
chemical_list: D000906:Antibodies; D008078:Cholesterol, LDL; D011973:Receptors, LDL; C472126:Pcsk9 protein, mouse; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases