Affinity maturation of a broadly neutralizing human monoclonal antibody that prevents acute hepatitis C virus infection in mice

Abstract

Direct acting antivirals (DAAs) have led to a high cure rate in treated patients with chronic hepatitis C virus (HCV) infection but this still leaves a large number of treatment failures secondary to the emergence of resistance-associated variants (RAVs). To increase the barrier to resistance, a complementary strategy is to employ neutralizing human monoclonal antibodies (HMAbs) to prevent acute infection. However, earlier efforts with the selected antibodies led to RAVs in animal and clinical studies. Therefore, we identified a HMAb that is less likely to elicit RAVs for affinity maturation to increase potency and, more importantly, breadth of protection. Selected matured antibodies show improved affinity and neutralization against a panel of diverse HCV isolates. Structural and modeling studies reveal that the affinity matured HMAb mediates virus neutralization in part by inducing conformational change to the targeted epitope and that the maturated light chain is responsible for the improved affinity and breadth of protection. A matured HMAb protected humanized mice when challenged with an infectious HCV human serum inoculum for a prolonged period. However, a single mouse experienced breakthrough infection after 63 days when the serum HMAb concentration dropped by several logs; sequence analysis revealed no viral escape mutation. Conclusions The findings suggest that a single broadly neutralizing antibody can prevent acute HCV infection without inducing RAVs and may complement DAAs to reduce the emergence of RAVs.

Synergistic anti-HCV broadly neutralizing human monoclonal antibodies with independent mechanisms

“…3A). This result may be explained, in part, by the presence in the HCVpp panel of four strains with leucine or isoleucine polymorphisms at the 442 locus in E2, which confer resistance to HC84.26 (16,22). HC84.26 resistance may be slightly exaggerated by this panel, since isoleucine (I) or leucine (L) polymorphisms at position 442 were present in 36% of isolates in this panel of 11 HCVpp, while they are present in only 17% of isolates in the reference panel of 634 genotype 1a and 1b sequences from GenBank.…”

“…We have chosen to focus on this genotype since it is most prevalent worldwide, and no bNAb isolated to date effectively neutralizes all genotype 1 HCV strains (9,22,23,43). While we have selected a panel of genotype 1 HCVpp that is genetically and phenotypically diverse, future studies are needed to confirm and extend these findings using larger panels of genotype 1 HCVpp, as well as HCV from other genotypes.…”

“…These bNAbs target overlapping but distinct epitopes on the HCV envelope proteins (E1 and E2) and neutralize diverse HCV strains (5-15). Combinations of bNAbs are protective against HCV challenge in animal models (9,10,16, 17), and spontaneous clearance of HCV without treatment in humans is associated with early development of bNAbs (18)(19)(20), suggesting that bNAbs may play a key role in immune-mediated control of human HCV infection.While some human bNAbs show impressive neutralizing breadth (5, 9, 20-22), HCV is an extraordinarily diverse virus, so no single bNAb neutralizes all viral strains (21-25). This resistance makes it less likely that vaccine induction of any single bNAb would provide adequate protection against a diverse HCV quasispecies challenge.…”

“…These bNAbs target overlapping but distinct epitopes on the HCV envelope proteins (E1 and E2) and neutralize diverse HCV strains (5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). Combinations of bNAbs are protective against HCV challenge in animal models (9,10,16,17), and spontaneous clearance of HCV without treatment in humans is associated with early development of bNAbs (18)(19)(20), suggesting that bNAbs may play a key role in immune-mediated control of human HCV infection.…”

Development and characterization of a human monoclonal antibody targeting the N-terminal region of hepatitis C virus envelope glycoprotein E1

“…Polyclonal antibodies from HCV-infected patients were able to protect animal models like humanized mice and chimpanzees from HCV challenge (Bukh et al, 2015; Meuleman et al, 2011; Vanwolleghem et al, 2008). We and others previously reported that neutralizing antibodies targeting the E2 protein could protect from HCV infection in vitro and in vivo (Desombere et al, 2016; Keck et al, 2016; Mesalam et al, 2016). In addition, administration of mAb MBL-HCV1, targeting E2, delayed viral rebound following liver transplantation, while complete protection was reported when combined with the polymerase inhibitor sofosbuvir (Chung et al, 2013; Smith et al, 2017).…”