Cross-Linking of a CD4-Mimetic Miniprotein with HIV-1 Env gp140 Alters Kinetics and Specificities of Antibody Responses against HIV-1 Env in Macaques

Abstract

Evaluation of the epitope specificities, locations (systemic or mucosal), and effector functions of antibodies elicited by novel HIV-1 immunogens engineered to improve exposure of specific epitopes is critical for HIV-1 vaccine development. Utilizing an array of humoral assays, we evaluated the magnitudes, epitope specificities, avidities, and functions of systemic and mucosal immune responses elicited by a vaccine regimen containing Env cross-linked to a CD4-mimetic miniprotein (gp140-M64U1) in rhesus macaques. Cross-linking of gp140 Env to M64U1 resulted in earlier increases of both the magnitude and avidity of the IgG binding response than those with Env protein alone. Notably, IgG binding responses at an early time point correlated with antibody-dependent cellular cytotoxicity (ADCC) function at the peak immunity time point, which was higher for the cross-linked Env group than for the Env group. In addition, the cross-linked Env group developed higher IgG responses against a linear epitope in the gp120 C1 region of the HIV-1 envelope glycoprotein. These data demonstrate that structural modification of the HIV-1 envelope immunogen by cross-linking of gp140 with the CD4-mimetic M64U1 elicited an earlier increase of binding antibody responses and altered the specificity of the IgG responses, correlating with the rise of subsequent antibody-mediated antiviral functions.IMPORTANCE The development of an efficacious HIV-1 vaccine remains a global priority to prevent new cases of HIV-1 infection. Of the six HIV-1 efficacy trials to date, only one has demonstrated partial efficacy, and immune correlate analysis of that trial revealed a role for binding antibodies and antibody Fc-mediated effector functions. New HIV-1 envelope immunogens are being engineered to selectively expose the most vulnerable and conserved sites on the HIV-1 envelope, with the goal of eliciting antiviral antibodies. Evaluation of the humoral responses elicited by these novel immunogen designs in nonhuman primates is critical for understanding how to improve upon immunogen design to inform further testing in human clinical trials. Our results demonstrate that structural modifications of Env that aim to mimic the CD4-bound conformation can result in earlier antibody elicitation, altered epitope specificity, and increased antiviral function postimmunization.

Increased, Durable B-Cell and ADCC Responses Associated with T-Helper Cell Responses to HIV-1 Envelope in Macaques Vaccinated with gp140 Occluded at the CD4 Receptor Binding Site

“…Importantly, we observed neutralizing responses against HIV-2 (Y720S) in the presence of sCD4 in the CD4-bound gp140 group, confirming that the CD4i epitopes were exposed, functional, and induced by this immunogen ( Fig. 7 ), and this was independently confirmed by Shen et al ( 27 ).…”

“…6 ). Given that globally the Env-neutralizing epitopes were otherwise identical in the CD4bs-blocked versus CD4bs-open gp140, this was not unexpected (with the exception of fine specificity differences of CD4i epitopes caused by CD4bs-M48U1 cross-linking [ 27 ]).…”

CCL19 and CCR7 Expression, Signaling Pathways, and Adjuvant Functions in Viral Infection and Prevention

“…In the context of viral neutralizing antibodies (nAbs), studies have shown that both monomeric gp120 and trimeric gp140 HIV-1 vaccines induce neutralizing antibody responses but still lack sufficient breadth to effectively protect against diverse HIV-1 isolates (García-Arriaza et al, 2017; Shen et al, 2017). HSV-2 gB or gD subunit vaccines could induce high levels of neutralizing Abs but could not efficiently protect mice against a viral challenge (Zhu et al, 2014).…”

Functional and Highly Crosslinkable HIV-1 Envelope Glycoproteins Enriched in a Pretriggered Conformation

“…Crosslinking of HIV-1 Env amino acid residues, in some cases combined with mass spectrometry, has been used to study Env conformations (37,73,(126)(127)(128)(129)(130)(131).…”