Anti-viral efficacy of a next-generation CD4-binding site bNAb in SHIV-infected animals in the absence of anti-drug antibody responses

Abstract

Broadly neutralizing antibodies (bNAbs) against HIV-1 are promising immunotherapeutic agents for treatment of HIV-1 infection. bNAbs can be administered to SHIV-infected rhesus macaques to assess their anti-viral efficacy; however, their delivery into macaques often leads to rapid formation of anti-drug antibody (ADA) responses limiting such assessment. Here, we depleted B cells in five SHIV-infected rhesus macaques by pretreatment with a depleting anti-CD20 antibody prior to bNAb infusions to reduce ADA. Peripheral B cells were depleted following anti-CD20 infusions and remained depleted for at least 9 weeks after the 1^st anti-CD20 infusion. Plasma viremia dropped by more than 100-fold in viremic animals after the initial bNAb treatment. No significant humoral ADA responses were detected for as long as B cells remained depleted. Our results indicate that transient B cell depletion successfully inhibited emergence of ADA and improved the assessment of anti-viral efficacy of a bNAb in a SHIV-infected rhesus macaque model.

Keywords: Drugs; Immunology; Virology.

Graphical abstract

Figure 1

Study design and in vivo B cell depletion after anti-CD20 infusion (A) SHIV-infected rhesus macaques were treated with intravenous (IV) infusions of 50 mg/kg afucosylated rhesusized anti-CD20 (anti-CD20, black arrows) followed by 10 mg/kg of bNAb VRC01v23 (blue arrows). Blood was sampled at indicated timepoints over the course of the study. (B) Representative flow cytometry plots of whole blood CD20⁺ B cells and total CD3⁺ T cells at days -37, -30, -28, 40, 82, and 154 of VRC01v23 infusion in NHP 3. B cell counts determined by number of CD19⁺ and/or CD20⁺ events after gating on CD3⁻ leukocytes. Peripheral B cell depletion was already seen 2 days following first anti-CD20 infusion. (C) CD19⁺ and/or CD20⁺ B cell counts in whole blood obtained by flow cytometry for each macaque normalized to its CD19⁺ and/or CD20⁺ B cell count average from day –37 and day 30 of bNAb infusion, prior to CD20 depletion (black arrows/dotted lines = anti-CD20 infusions, blue arrows/dashed lines = VRC01v23 infusions). (D) Pharmacokinetics (PK) of anti-CD20 in macaque plasma following three 50 mg/kg IV infusions (LOD = 31 μg/mL). See also Figures S1 and S2.

Figure 2

VRC01v23 anti-viral efficacy and pharmacokinetics (A) Plasma viral load (LOD = 15 copies/mL) up to 76 days following the first VRC01v23 infusion (black arrows/dotted lines = anti-CD20 infusions, blue arrows/dashed lines = VRC01v23 infusions). (B) Pharmacokinetics (PK) of VRC01v23 (blue, solid shapes) represented by plasma concentration of the bNAb (LOD = 0.3 μg/mL) for up to 76 days following the first bNAb infusion. Plasma viral loads (red, hollow shapes) of each animal respectively shown for evaluation of VRC01v23 effect on viremia. Each point in the PK curves represent the mean of at least two replicates and the error bar represents the standard error. See also Figure S3.

Figure 3

Anti-drug antibody responses against VRC01v23 infusions and effect on pharmacokinetics (A) Plasma anti-drug antibody ELISA endpoint titers against the bNAb VRC01v23 (ADA, dashed lines) and bNAb pharmacokinetics (PK, solid lines) after one 10 mg/kg IV infusion (blue arrow) in naive animals which did not receive anti-CD20 (control). (B) ADA endpoint titers (dashed lines, LOD = 50) and VRC01v23 PK (solid lines) after three 10 mg/kg IV infusions (blue arrows) in SHIV-infected animals which received anti-CD20 (treatment). Each point in the PK curves represent the mean of at least two replicates and the error bar represents the standard error. See also Figure S4.

Figure 4

Reinfusions with VRC01v23 following viral rebound (A) IV infusion schedule of study animals that still had B cells depleted when viremia had rebounded and stabilized. Two weekly infusions of 10 mg/kg bNAb VRC01v23 (blue arrows) given 62 days after the last bNAb infusion from the original treatment schedule. Blood was sampled at indicated timepoints over the course of the study. (B) B cell counts in whole blood obtained by flow cytometry for each macaque normalized to its B cell count average of day −37 and day −30 of bNAb infusion, prior to CD20 depletion (blue arrows/dashed lines = VRC01v23 infusions). (C) VRC01v23 PK (solid lines) and ADA endpoint titers (dashed lines) after the two 10 mg/kg IV reinfusions. Each point in the PK curves represent the mean of at least two replicates and the error bar represents the standard error. (D) Plasma viral load baseline levels after initial rebound and response to reinfusion of VRC01v23.