HIV Broadly Neutralizing Antibodies Expressed as IgG3 Preserve Neutralization Potency and Show Improved Fc Effector Function

Abstract

The ability of several broadly neutralizing antibodies (bNAbs) to protect against HIV infection is enhanced through Fc receptor binding. Antibody isotype modulates this effect, with IgG3 associated with improved HIV control and vaccine efficacy. We recently showed that an IgG3 variant of bNAb CAP256-VRC26.25 exhibited more potent neutralization and phagocytosis than its IgG1 counterpart. Here, we expanded this analysis to include additional bNAbs targeting all major epitopes. A total of 15 bNAbs were expressed as IgG1 or IgG3, and pairs were assessed for neutralization potency against the multi-subtype global panel of 11 HIV strains. Binding to the neonatal Fc receptor (FcRn) and Fcγ receptors were measured using ELISA and antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis were measured using infectious viruses and global panel Env SOSIP trimers, respectively. IgG3 bNAbs generally showed similar or increased (up to 60 fold) neutralization potency than IgG1 versions, though the effect was virus-specific. This improvement was statistically significant for CAP256-VRC26.25, 35022, PGT135 and CAP255.G3. IgG3 bNAbs also showed significantly improved binding to FcγRIIa which correlated with enhanced phagocytosis of all trimeric Env antigens. Differences in ADCC were epitope-specific, with IgG3 bNAbs to the MPER, CD4 binding site and gp120-gp41 interface showing increased ADCC. We also explored the pH dependence of IgG1 and IgG3 variants for FcRn binding, as this determines the half-life of antibodies. We observed reduced pH dependence, associated with shorter half-lives for IgG3 bNAbs, with κ-light chains. However, IgG3 bNAbs that use λ-light chains showed similar pH dependence to their IgG1 counterparts. This study supports the manipulation of the constant region to improve both the neutralizing and Fc effector activity of bNAbs, and suggests that IgG3 versions of bNAbs may be preferable for passive immunity given their polyfunctionality.

Patient-derived monoclonal antibody neutralizes SARS-CoV-2 Omicron variants and confers full protection in monkeys

“…Antibody Fc-mediated functional activity assays. ADCC and ADCP assays were performed as previously described with minor changes 40 . Cryopreserved peripheral blood mononuclear cells (PBMCs) from healthy patients were thawed and resuspended at 1 million ml −1 in RPMI medium (Gibco, Life Technologies) supplemented with 10% heat-inactivated fetal bovine serum (FBS), 100 IU ml −1 penicillin and 100 µg ml −1 streptomycin (BioConcept).…”

Challenges and Opportunities of Therapies Targeting Early Life Immunity for Pediatric HIV Cure

“…Numerous efforts are currently being developed to ensure consistent high levels of bNAbs in the circulation including various modifications to extend their half-lives (120,(136)(137)(138)(139) and expression of bNAbs using viral vectors (122,140,141). Additional strategies are currently being developed to enhance the ability of Fc effector functions, including antibody-mediated cell cytotoxicity (ADCC) and antibody-dependent cell phagocytosis (ADCP), to clear HIV-infected cells (121,122,(142)(143)(144). The Fc region enhancement can be accomplished by (i) altering the antibody isotype (142,143), (ii) modifying the antibody Fc domain amino acid sequences (139,144), and (iii) modifying the antibody Fc glycans (122,145).…”

“…Additional strategies are currently being developed to enhance the ability of Fc effector functions, including antibody-mediated cell cytotoxicity (ADCC) and antibody-dependent cell phagocytosis (ADCP), to clear HIV-infected cells (121,122,(142)(143)(144). The Fc region enhancement can be accomplished by (i) altering the antibody isotype (142,143), (ii) modifying the antibody Fc domain amino acid sequences (139,144), and (iii) modifying the antibody Fc glycans (122,145). These approaches modulate antiviral breadth and potency of bNAb therapy by increasing bNAbs affinity to cognate Fc receptors on host immune cells and host complement proteins for elimination of HIV-infected cells.…”

SARS-CoV-2 Omicron potently neutralized by a novel antibody with unique Spike binding properties

“…Antibody dependent cellular cytotoxicity (ADCC) and antibody dependent phagocytosis (ADCP) assays were performed as previously described with minor changes 37 . Cryopreserved peripheral blood mononuclear cells from healthy patient were thawed and resuspended at 1 million/ml in RPMI medium (Gibco, Life Technologies) supplemented with 10% heat-inactivated fetal bovine serum (FBS), 100 IU/ml penicillin and 100 μg/ml streptomycin (BioConcept).…”