A novel HIV triple broadly neutralizing antibody (bNAb) combination-based passive immunization of infant rhesus macaques achieves durable protective plasma neutralization levels and mediates anti-viral effector functions

Abstract

To eliminate vertical HIV transmission and achieve therapy-free viral suppression among children living with HIV, novel strategies beyond antiretroviral therapy (ART) are necessary. Our group previously identified a triple broadly neutralizing antibody (bNAb) combination comprising of 3BNC117, PGDM1400 and PGT151 that mediates robust in vitro neutralization and non-neutralizing effector functions against a cross-clade panel of simian human immunodeficiency viruses (SHIVs). In this study, we evaluated the safety, pharmacokinetics, and antiviral potency of this bNAb combination in infant rhesus macaques (RMs). We demonstrate that subcutaneous infusion of the triple bNAb regimen was well tolerated in pediatric monkeys and resulted in durable systemic and mucosal distribution. Plasma obtained from passively-immunized RMs demonstrated potent HIV-neutralizing and Fc-mediated antiviral effector functions. Finally, using the predicted serum neutralization 80% inhibitory dilution titer (PT80) biomarker threshold of >200, which was recently identified as a surrogate endpoint for evaluation of the preventative efficacy of bNAbs against mucosal viral acquisition in human clinical trials, we demonstrated that our regimen has PT80>200 against a large panel of plasma and breast milk-derived HIV strains and cross-clade SHIV variants. This data will guide the development of combination bNAbs for eliminating vertical HIV transmission and for achieving ART-free viral suppression among children living with HIV.

Fig 1. Passive immunization of a rhesusized (Rh)-triple bNAb combination in infant rhesus macaques (RM).

(A) Neutralization of SHIV.C.CH505.375H.dCT by the human (Hu) and rhesusized (Rh) versions of 3 bNAbs, 3BNC117, PGDM1400, PGT151 and their combination in vitro. Neutralizing IC₈₀s (μg/mL) of the antibodies are reported. (B) HIV CH505 T/F-specific ADCC response of the Hu and Rh versions of the 3 above-mentioned bNAbs. ADCC antibody titers in μg/mL are reported. (C) Three infant RMs passively immunized with a triple bNAb formulation consisting of Rh-3BNC117,—PGDM1400 and -PGT151, each antibody at a 40mg/kg dosage. Plasma, saliva, and rectal swab samples collected at indicated time points for experimental analysis. (D) Body weights of the infant RMs monitored over 76 days post-infusion. Each RM is indicated by a symbol and the median body weight over time is represented as bolded line. Pink arrow indicates the time of triple Rh-bNAb infusion.

Fig 2. Concentrations of infused Rh-bNAbs in plasma and development of anti-drug antibody (ADA) in infant RMs.

Plasma concentration of passively infused (A) Rh-3BNC117, (B) Rh-PGDM1400 and (C) Rh-PGT151 at indicated time points post-infusion, as determined by ELISA. ADA responses against (D) Rh-3BNC117, (E) Rh-PGDM1400, and (F) Rh-PGT151 at indicated time points, as measured by ELISA. Each monkey is denoted by a unique symbol. Pink arrow indicates the time of triple Rh-bNAb infusion.

Fig 3. Specificity, neutralizing and non-neutralizing antibody functions of plasma from passively-infused infant RMs.

(A) Magnitude and kinetics of HIV CH505-SOSIP-specific IgG antibodies in the plasma of triple Rh bNAb-infused infant RMs. (B) Plasma neutralization titer against a tier-2 clade C virus, SHIV.C.CH505.375H.dCT, at indicated time points. (C) Antibody-dependent cellular cytotoxicity (ADCC) Ab titers against HIV CH505 T/F infectious molecular clone-infected target cells and (D) HIV CH505 SOSIP-specific antibody-dependent cellular phagocytosis (ADCP) scores of plasma from combination Rh-bNAb-infused infant RMs. Each monkey is denoted by a color and a unique symbol. The dashed lines indicate the limit of detection (LOD) of ADCC and ADCP assays. LOD for ADCC assay is 100 and LOD for ADCP assay is defined as 3 times ADCP score of a non-HIV-specific antibody CH65 against HIV CH505 SOSIP.

Fig 4. PT₈₀ of the infused bNAb regimen against cross-clade SHIV and HIV variants.

(A) Correlation of the triple bNAb combination PT₈₀ and experimental plasma ID₈₀ against SHIV.C.CH505.375H.dCT for each RM over multiple time points. Each animal is represented by a single color and symbol. Kendal Tau’s correlation was performed to calculate the correlation coefficient and p-value. (B) Median PT₈₀ of the triple bNAb combination against 9 cross-clade SHIV variants, consisting of clade A, B, C and D pseudoviruses. Dashed line indicates PT₈₀>200. Neutralization IC₈₀ of the triple bNAb regimen against corresponding SHIVs are included in the figure key. (C) Heat map representing the number of days for which PT₈₀ of the triple bNAb combination remains above 200 for plasma and breast milk isolated HIV variants. (D) Percentage of HIV variants for which PT80>200 for 3 RMs at indicated time points. Each animal is denoted by a unique symbol. Shaded boxes indicate the range of days post-infusion for which PT₈₀>200 against a median of ≥90% (blue) and ≥40% (light grey) HIV variants are achieved.