Anti-Drug Antibodies in Pigtailed Macaques Receiving HIV Broadly Neutralising Antibody PGT121

Abstract

Broadly neutralising antibodies (bNAbs) may play an important role in future strategies for HIV control. The development of anti-drug antibody (ADA) responses can reduce the efficacy of passively transferred bNAbs but the impact of ADA is imperfectly understood. We previously showed that therapeutic administration of the anti-HIV bNAb PGT121 (either WT or LALA version) controlled viraemia in pigtailed macaques with ongoing SHIV infection. We now report on 23 macaques that had multiple treatments with PGT121. We found that an increasing number of intravenous doses of PGT121 or human IgG1 isotype control antibodies (2-4 doses) results in anti-PGT121 ADA induction and low plasma concentrations of PGT121. ADA was associated with poor or absent suppression of SHIV viremia. Notably, ADA within macaque plasma recognised another human bNAb 10E8 but did not bind to the variable domains of PGT121, suggesting that ADA were primarily directed against the constant regions of the human antibodies. These findings have implications for the development of preclinical studies examining multiple infusions of human bNAbs.

Keywords: HIV; PGT121; anti-drug antibodies (ADA); broadly neutralizing antibodies (bNAb); pigtailed macaque.

Figure 1

Anti-PGT121 antibodies develop in pigtailed macaques following exposure to human antibodies. Five pigtailed macaques were administered PGT121 or a human IgG1 isotype control antibody intravenously (1mg/kg) prior to challenge with cell-free or cell-associated SHIV. Macaques NM04 and NM05 were administered human seminal plasma either intrarectally or both intravaginally and intrarectally prior to intrarectal challenge with SHIV. Viraemic animals were then infused with PGT121 with either WT or LALA Fc. Macaque anti-PGT121 ADA are shown in the blue line (left y-axis) while SHIV viral loads are shown in the red line (right y-axis). Black arrows indicate antibody administration while red arrows indicate SHIV challenge. The red text indicates failed therapy with PGT121 WT or LALA.

Figure 2

Anti-PGT121 antibodies limit the plasma concentration of PGT121 and diminish the therapeutic efficacy of PGT121 against SHIV. The plasma concentration of PGT121 WT or LALA post-infusion (open circles, left y-axis) is plotted with the level of anti-PGT121 ADA (blue line, right y-axis) or SHIV viral loads (red line, right y-axis). Black arrows indicate antibody administration. The red text indicates failed therapy with PGT121 WT or LALA.

Figure 3

ADA at time of infusion negatively correlates with viral suppression by PGT121. Macaques with active SHIV infection were administered PGT121 WT or LALA. Plasma viral loads were measured by digital droplet PCR at 0, 24, 36, 48 and 72 hours after PGT121 infusion and the decay rate within 72 hours was calculated using linear regression. The correlation was performed using a non-parametric spearman test.

Figure 4

Anti-PGT121 ADA increases with the number of exposures to human antibodies. (A) The level of anti-PGT121 ADA in macaques before (closed circles) and 3-4 weeks after (open circles) exposure to human antibodies. (B) The level of anti-PGT121 ADA before and after exposure to different sources of human antibodies (intravenous administration of PGT121 WT, PGT121 LALA, eCD4-Ig and human IgG1 isotype control antibody or intrarectal/intravaginal administration of human seminal plasma).

Figure 5

The specificity of ADA responses in pigtailed macaques following multiple infusions of human antibodies. (A) Macaque anti-PGT121 and anti-10E8 ADA are shown in blue and red respectively. (B) The level of macaque ADA against full length PGT121 (closed circles) and PGT121 scFv (open circles). Black arrows indicate antibody administration.