Hepatitis C virus Broadly Neutralizing Monoclonal Antibodies Isolated 25 Years after Spontaneous Clearance

Abstract

Hepatitis C virus (HCV) is world-wide a major cause of liver related morbidity and mortality. No vaccine is available to prevent HCV infection. To design an effective vaccine, understanding immunity against HCV is necessary. The memory B cell repertoire was characterized from an intravenous drug user who spontaneously cleared HCV infection 25 years ago. CD27+IgG+ memory B cells were immortalized using BCL6 and Bcl-xL. These immortalized B cells were used to study antibody-mediated immunity against the HCV E1E2 glycoproteins. Five E1E2 broadly reactive antibodies were isolated: 3 antibodies showed potent neutralization of genotype 1 to 4 using HCV pseudotyped particles, whereas the other 2 antibodies neutralized genotype 1, 2 and 3 or 1 and 2 only. All antibodies recognized non-linear epitopes on E2. Finally, except for antibody AT12-011, which recognized an epitope consisting of antigenic domain C /AR2 and AR5, all other four antibodies recognized epitope II and domain B. These data show that a subject, who spontaneously cleared HCV infection 25 years ago, still has circulating memory B cells that are able to secrete broadly neutralizing antibodies. Presence of such memory B cells strengthens the argument for undertaking the development of an HCV vaccine.

Broadly neutralizing antibodies with few somatic mutations and hepatitis C virus clearance

“…Surprisingly, despite developing in two different individuals, HEPC3, HEPC43, and HEPC74 are each encoded by the same antibody heavy chain variable gene segment, V H 1-69 (Table 1). Of note, mAb AR3C, which was isolated from a subject with chronic HCV infection, also uses V H 1-69 (17), as do some other anti-HCV bNAbs (12,34). Together with the epitope mapping data, these results suggest that V H 1-69 encodes antibodies with capacity to form a public B cell clonotype that favors binding to an immunodominant broadly neutralizing HEPC3/AR3C epitope.…”

“…Multiple studies have now confirmed that several anti-HCV bNAbs are encoded by the V H 1-69 antibody gene segment (12,34). This study shows for the first time to our knowledge that V H 1-69 commonly encodes a public B cell clonotype that can lead to bNAb development after a relatively brief period of infection, producing an antibody with recognition of an entire autologous viral quasispecies, thus providing what we believe to be the first potential mechanistic link between this B cell clonotype and spontaneous clearance of HCV.…”

“…Broadly neutralizing human mAbs (bNAbs) capable of neutralizing diverse HCV strains have been isolated from HCV-infected individuals, proving that antibodies can target relatively conserved regions of the two HCV envelope glycoproteins (E1 and E2), despite the enormous genetic diversity of HCV (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). Infusion of bNAbs is protective against infection in animal models of HCV (17,18), and a recent study also showed that bNAbs could abrogate established HCV infection in a humanized transgenic mouse model (19).…”

Structure-based design of hepatitis C virus E2 glycoprotein improves serum binding and cross-neutralization

“…The designed substitution H445P, which was generated to preferentially adopt the bnAb-bound form in a portion of E2 antigenic domain D that exhibits structural variability (31), showed the greatest level of success, both with regard to improvements in serum binding to homologous and heterologous HCVpp, as well as HCVpp neutralization of heterologous HCVpp. This design lies within a supersite of E2 associated with many broadly neutralizing antibodies (5,6,44,45), and through biophysical characterization and molecular dynamics simulation experiments, others have found that this region is likely quite flexible (27,46), providing a rationale for stabilizing key residues to engage and elicit bNAbs. Interestingly, a residue adjacent to the site of this design appears to be functionally important, with the Q444R substitution restoring viral infectivity in the context of an HCVpp with a domain E "glycan shift" substitution, N417S (8).…”

Optimised cell systems for the investigation of hepatitis C virus E1E2 glycoproteins

“…3e). This experiment was conducted for a further four mAbs; (i) AR4A, which targets an epitope composed of both E1 and E2 residues, (ii) AT-12009 (CD81-bs), (iii) HC84.26 (domain D) and (iv) IgH505, which targets a discontinuous epitope in E1 (residues 313-327) (32,(39)(40)(41). We saw no significant difference in the infectivities of the panel against all 4 mAbs irrespective of the cell line of production ( Fig.…”