title: Antibodies against West Nile Virus nonstructural protein NS1 prevent lethal infection through Fc gamma receptor-dependent and -independent mechanisms.
abstract: The flavivirus nonstructural protein NS1 is a highly conserved secreted glycoprotein that does not package with the virion. Immunization with NS1 elicits a protective immune response against yellow fever, dengue, and tick-borne encephalitis flaviviruses through poorly defined mechanisms. In this study, we purified a recombinant, secreted form of West Nile virus (WNV) NS1 glycoprotein from baculovirus-infected insect cells and generated 22 new NS1-specific monoclonal antibodies (MAbs). By performing competitive binding assays and expressing truncated NS1 proteins on the surface of yeast (Saccharomyces cerevisiae) and in bacteria, we mapped 21 of the newly generated MAbs to three NS1 fragments. Prophylaxis of C57BL/6 mice with any of four MAbs (10NS1, 14NS1, 16NS1, and 17NS1) strongly protected against lethal WNV infection (75 to 95% survival, respectively) compared to saline-treated controls (17% survival). In contrast, other anti-NS1 MAbs of the same isotype provided no significant protection. Notably, 14NS1 and 16NS1 also demonstrated marked efficacy as postexposure therapy, even when administered as a single dose 4 days after infection. Virologic analysis showed that 17NS1 protects at an early stage in infection through a C1q-independent and Fc gamma receptor-dependent pathway. Interestingly, 14NS1, which maps to a distinct region on NS1, protected through a C1q- and Fc gamma receptor-independent mechanism. Overall, our data suggest that distinct regions of NS1 can elicit protective humoral immunity against WNV through different mechanisms.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, Campus Box 8051, 660 S. Euclid Avenue, St. Louis, MO 63110, USA.
authors.forename: Kyung Min
authors.initials: KM
authors.lastname: Chung
authors.forename: Grant E
authors.initials: GE
authors.lastname: Nybakken
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Thompson
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Engle
authors.forename: Anantha
authors.initials: A
authors.lastname: Marri
authors.forename: Daved H
authors.initials: DH
authors.lastname: Fremont
authors.forename: Michael S
authors.initials: MS
authors.lastname: Diamond
mesh_terms: D000330:Aedes; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D000914:Antibodies, Viral / Q000008:administration & dosage*; D000956:Antigens, Viral / Q000235:genetics; D001483:Base Sequence; D002460:Cell Line; D006224:Cricetinae; D004279:DNA, Viral / Q000235:genetics; D018604:Epitope Mapping; D051379:Mice; D008810:Mice, Inbred C57BL; D017452:Receptors, IgG / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D017361:Viral Nonstructural Proteins / Q000235:genetics / Q000276:immunology*; D014901:West Nile Fever / Q000276:immunology* / Q000517:prevention & control* / Q000628:therapy; D014902:West Nile virus / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity*
chemical_list: D000911:Antibodies, Monoclonal; D000914:Antibodies, Viral; D000956:Antigens, Viral; D004279:DNA, Viral; C100315:NS1 protein, Flavivirus; D017452:Receptors, IgG; D011994:Recombinant Proteins; D017361:Viral Nonstructural Proteins