title: Potent neutralization of vaccinia virus by divergent murine antibodies targeting a common site of vulnerability in L1 protein.
abstract: Vaccinia virus (VACV) L1 is an important target for viral neutralization and has been included in multicomponent DNA or protein vaccines against orthopoxviruses. To further understand the protective mechanism of the anti-L1 antibodies, we generated five murine anti-L1 monoclonal antibodies (MAbs), which clustered into 3 distinct epitope groups. While two groups of anti-L1 failed to neutralize, one group of 3 MAbs potently neutralized VACV in an isotype- and complement-independent manner. This is in contrast to neutralizing antibodies against major VACV envelope proteins, such as H3, D8, or A27, which failed to completely neutralize VACV unless the antibodies are of complement-fixing isotypes and complement is present. Compared to nonneutralizing anti-L1 MAbs, the neutralization antibodies bound to the recombinant L1 protein with a significantly higher affinity and also could bind to virions. By using a variety of techniques, including the isolation of neutralization escape mutants, hydrogen/deuterium exchange mass spectrometry, and X-ray crystallography, the epitope of the neutralizing antibodies was mapped to a conformational epitope with Asp35 as the key residue. This epitope is similar to the epitope of 7D11, a previously described potent VACV neutralizing antibody. The epitope was recognized mainly by CDR1 and CDR2 of the heavy chain, which are highly conserved among antibodies recognizing the epitope. These antibodies, however, had divergent light-chain and heavy-chain CDR3 sequences. Our study demonstrates that the conformational L1 epitope with Asp35 is a common site of vulnerability for potent neutralization by a divergent group of antibodies.
  
  
  OBJECTIVE
  Vaccinia virus, the live vaccine for smallpox, is one of the most successful vaccines in human history, but it presents a level of risk that has become unacceptable for the current population. Studying the immune protection mechanism of smallpox vaccine is important for understanding the basic principle of successful vaccines and the development of next-generation, safer vaccines for highly pathogenic orthopoxviruses. We studied antibody targets in smallpox vaccine by developing potent neutralizing antibodies against vaccinia virus and comprehensively characterizing their epitopes. We found a site in vaccinia virus L1 protein as the target of a group of highly potent murine neutralizing antibodies. The analysis of antibody-antigen complex structure and the sequences of the antibody genes shed light on how these potent neutralizing antibodies are elicited from immunized mice.
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: Thomas
authors.initials: T
authors.lastname: Kaever
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA.
authors.forename: Xiangzhi
authors.initials: X
authors.lastname: Meng
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Matho
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Schlossman
authors.affiliation: Medicine and Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, California, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Li
authors.affiliation: The Goodman Faculty of Life Sciences, Nanotechnology Building, Bar Ilan University, Ramat Gan, Israel.
authors.forename: Inbal
authors.initials: I
authors.lastname: Sela-Culang
authors.affiliation: The Goodman Faculty of Life Sciences, Nanotechnology Building, Bar Ilan University, Ramat Gan, Israel.
authors.forename: Yanay
authors.initials: Y
authors.lastname: Ofran
authors.affiliation: Saint Louis University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Buller
authors.affiliation: Saint Louis University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Ryan W
authors.initials: RW
authors.lastname: Crump
authors.affiliation: Saint Louis University School of Medicine, St. Louis, Missouri, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Parker
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: April
authors.initials: A
authors.lastname: Frazier
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: Shane
authors.initials: S
authors.lastname: Crotty
authors.affiliation: Division of Cell Biology, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: Dirk M
authors.initials: DM
authors.lastname: Zajonc
authors.affiliation: Division of Vaccine Discovery, La Jolla Institute for Allergy and Immunology (LJI), La Jolla, California, USA.
authors.forename: Bjoern
authors.initials: B
authors.lastname: Peters
authors.affiliation: Department of Microbiology and Immunology, University of Texas Health Science Center at San Antonio, San Antonio, Texas, USA xiangy@uthscsa.edu.
authors.forename: Yan
authors.initials: Y
authors.lastname: Xiang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D057134:Antibodies, Neutralizing / Q000737:chemistry*; D000914:Antibodies, Viral / Q000737:chemistry*; D000956:Antigens, Viral; D000939:Epitopes / Q000737:chemistry / Q000276:immunology; D005260:Female; D051379:Mice; D008807:Mice, Inbred BALB C; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D054730:Protein Interaction Domains and Motifs; D016019:Survival Analysis; D014611:Vaccination; D014615:Vaccinia / Q000276:immunology* / Q000401:mortality / Q000517:prevention & control / Q000821:virology; D014616:Vaccinia virus / Q000737:chemistry / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000008:administration & dosage / Q000737:chemistry* / Q000276:immunology; D014771:Virion / Q000737:chemistry / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000956:Antigens, Viral; D000939:Epitopes; D014759:Viral Envelope Proteins