RESUMEN
The HIV-1 envelope (Env) spike is a trimer of gp120/gp41 heterodimers that mediates viral entry. Binding to CD4 on the host cell membrane is the first essential step for infection but disrupts the native antigenic state of Env, posing a key obstacle to vaccine development. We locked the HIV-1 Env trimer in a pre-fusion configuration, resulting in impaired CD4 binding and enhanced binding to broadly neutralizing antibodies. This design was achieved via structure-guided introduction of neo-disulfide bonds bridging the gp120 inner and outer domains and was successfully applied to soluble trimers and native gp160 from different HIV-1 clades. Crystallization illustrated the structural basis for CD4-binding impairment. Immunization of rabbits with locked trimers from two different clades elicited neutralizing antibodies against tier-2 viruses with a repaired glycan shield regardless of treatment with a functional CD4 mimic. Thus, interdomain stabilization provides a widely applicable template for the design of Env-based HIV-1 vaccines.
Asunto(s)
Antígenos CD4/inmunología , Antígenos CD4/metabolismo , VIH-1/inmunología , Unión Proteica/inmunología , Dominios Proteicos , Estabilidad Proteica , Productos del Gen env del Virus de la Inmunodeficiencia Humana/química , Productos del Gen env del Virus de la Inmunodeficiencia Humana/inmunología , Vacunas contra el SIDA/inmunología , Animales , Anticuerpos Neutralizantes/inmunología , Femenino , Células HEK293 , Anticuerpos Anti-VIH/inmunología , Antígenos VIH/química , Antígenos VIH/inmunología , Proteína gp120 de Envoltorio del VIH/química , Proteína gp120 de Envoltorio del VIH/genética , Proteína gp120 de Envoltorio del VIH/inmunología , Proteína gp120 de Envoltorio del VIH/metabolismo , Proteínas gp160 de Envoltorio del VIH/química , Proteínas gp160 de Envoltorio del VIH/inmunología , Proteínas gp160 de Envoltorio del VIH/metabolismo , VIH-1/genética , VIH-1/patogenicidad , Humanos , Inmunización , Modelos Moleculares , Conformación Proteica , Dominios Proteicos/inmunología , Conejos , Internalización del Virus , Productos del Gen env del Virus de la Inmunodeficiencia Humana/genéticaRESUMEN
Binding of the gp120 envelope (Env) glycoprotein to the CD4 receptor is the first step in the HIV-1 infectious cycle. Although the CD4-binding site has been extensively characterized, the initial receptor interaction has been difficult to study because of major CD4-induced structural rearrangements. Here we used cryogenic electron microscopy (cryo-EM) to visualize the initial contact of CD4 with the HIV-1 Env trimer at 6.8-Å resolution. A single CD4 molecule is embraced by a quaternary HIV-1-Env surface formed by coalescence of the previously defined CD4-contact region with a second CD4-binding site (CD4-BS2) in the inner domain of a neighboring gp120 protomer. Disruption of CD4-BS2 destabilized CD4-trimer interaction and abrogated HIV-1 infectivity by preventing the acquisition of coreceptor-binding competence. A corresponding reduction in HIV-1 infectivity occurred after the mutation of CD4 residues that interact with CD4-BS2. Our results document the critical role of quaternary interactions in the initial HIV-Env-receptor contact, with implications for treatment and vaccine design.
