title: Cross-Neutralization Activity of Single-Chain Variable Fragment (scFv) Derived from Anti-V3 Monoclonal Antibodies Mediated by Post-Attachment Binding.
abstract: The V3 loop in the envelope (Env) of HIV-1 is one of the major targets of neutralizing antibodies. However, this antigen is hidden inside the Env trimer in most isolates and is fully exposed only during CD4-gp120 interaction. Thus, primary HIV-1 isolates are relatively resistant to anti-V3 antibodies because IgG is too large to access the V3 loop. To overcome this obstacle, we constructed single-chain variable fragments (scFvs) from anti-V3 monoclonal antibodies 0.5γ, 5G2, and 16G6. Enhanced neutralization by 0.5γ and 5G2 scFvs was observed in strains resistant to their IgG counterparts. Neutralization coverage by 0.5γ scFv reached up to 90% of the tested viruses (tier 2 and 3 classes). The temperature-regulated neutralization assay revealed that extensive cross-neutralization of 0.5γ scFv can be explained by post-attachment neutralization. Neutralization assay involving viruses carrying an inter-subunit disulfide bond (SOS virus) showed that the neutralization-susceptible timeframe after attachment was 60 to 120 min. These results indicate that the scFvs efficiently access the V3 loop and subsequently neutralize HIV-1, even after virus attachment to the target cells. Based on its broad and potent neutralizing activity, further development of anti-V3 scFv for therapeutic and preventive strategies is warranted.
authors.affiliation: Matsushita Project Laboratory, Center for AIDS Research, Kumamoto University.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Maruta
authors.forename: Takeo
authors.initials: T
authors.lastname: Kuwata
authors.forename: Kazuki
authors.initials: K
authors.lastname: Tanaka
authors.forename: Muntasir
authors.initials: M
authors.lastname: Alam
authors.forename: Kristel Paola Ramirez
authors.initials: KP
authors.lastname: Valdez
authors.forename: Yoshika
authors.initials: Y
authors.lastname: Egami
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Suwa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Morioka
authors.forename: Shuzo
authors.initials: S
authors.lastname: Matsushita
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology*; D057134:Antibodies, Neutralizing / Q000276:immunology*; D003429:Cross Reactions; D015483:HIV Antibodies / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D009500:Neutralization Tests; D057127:Single-Chain Antibodies / Q000276:immunology*; D054299:env Gene Products, Human Immunodeficiency Virus / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D015483:HIV Antibodies; D057127:Single-Chain Antibodies; D054299:env Gene Products, Human Immunodeficiency Virus