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

Abstract

There is an urgent need for a vaccine to combat the hepatitis C virus (HCV) pandemic, and induction of broadly neutralizing monoclonal antibodies (bNAbs) against HCV is a major goal of vaccine development. Even within HCV genotype 1, no single bNAb effectively neutralizes all viral strains, so induction of multiple neutralizing monoclonal antibodies (NAbs) targeting distinct epitopes may be necessary for protective immunity. Therefore, identification of optimal NAb combinations and characterization of NAb interactions can guide vaccine development. We analyzed neutralization profiles of 12 human NAbs across diverse HCV strains, assigning the NAbs to two functionally distinct clusters. We then measured neutralizing breadth of 35 NAb combinations against genotype 1 isolates, with each combination including one NAb from each neutralization cluster. Many NAbs displayed complementary neutralizing breadth, forming combinations with greater neutralization across diverse strains than any individual bNAb. Remarkably, one of the most broadly neutralizing combinations of two NAbs, designated HEPC74/HEPC98, also displayed enhanced potency, with interactions matching the Bliss independence model, suggesting that these NAbs inhibit HCV infection through independent mechanisms. Subsequent experiments showed that HEPC74 primarily blocks HCV envelope protein binding to CD81, while HEPC98 primarily blocks binding to scavenger receptor B1 and heparan sulfate. Together, these data identify a critical vulnerability resulting from the reliance of HCV on multiple cell surface receptors, suggesting that vaccine induction of multiple NAbs with distinct neutralization profiles is likely to enhance the breadth and potency of the humoral immune response against HCV.neutralizing antibody | hepatitis C virus | synergy | antagonism | neutralizing breadth D espite the development of highly effective direct-acting antivirals (DAAs) for treatment of hepatitis C virus (HCV) infection, a vaccine is still needed to combat the HCV pandemic. Most infected individuals are unaware of their status and may continue to expose others (1). Most infected persons do not have access to DAAs, and currently available treatments do not provide protection against reinfection after cure (2-4).One objective of HCV vaccine development is the induction of broadly neutralizing monoclonal antibodies (bNAbs) against the virus. Dozens of bNAbs have been isolated from infected humans. 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 st...

Building a mechanistic mathematical model of hepatitis C virus entry

“…This work demonstrates that entry occurs via a two-phase process, in the first of which HCV forms a tripartite receptor complex with SR-B1, CD81 and EGFR at the basolateral surface. Numerous other studies have assessed HCV entry kinetics using time of addition inhibitor studies; these experiments suggest that SR-B1 functions immediately after virus attachment, and likely precedes CD81 engagement [12,36,37]. Furthermore, multiple reports have been made of a minority fraction of infection that persists despite targeting of SR-B1 with CRISPR, siRNA or antibody blockade [35,37,48,49], supporting the notion of an SR-B1-independent mode of entry.…”

“…Whereas the CD81 binding site is composed of discontinuous protein domains that are bought together in the tertiary structure of E2 and interact with the large extracellular loop of CD81 [5,11]. Strain specific and broadly neutralising antibodies, which develop during natural infection, act by blocking E2-SR-B1/CD81 interactions [12][13][14][15]. A deeper understanding of E2 function and its interactions with SR-B1 and CD81 is likely to aid the design of candidate B-cell targeted vaccines.…”

B cell immunodominance in primary hepatitis C virus infection

“…The aim of a B cell-based vaccine is to induce responses that protect from multiple virus genotypes and subtypes. In this cohort, plasma samples with bNAb activity were enriched for multi-epitope responses, particularly directed towards AR2, AR3, AR4 and domain D. Interestingly, these combinations were recently shown by 2 independent reports to have synergistic activity in vitro, 11,32 which was superior to individual mAb activities. This supports a recent paper by Kinchen and colleagues, 33 who reported that the induction of AR3 or domain D targeting bNAbs may be important in developing an effective NAb response in combination with AR4-targeting bNAbs.…”

<p>Hepatocellular Carcinoma Mechanisms Associated with Chronic HCV Infection and the Impact of Direct-Acting Antiviral Treatment</p>

“…Increasing evidence suggests that neutralizing antibodies are associated with spontaneous clearance of HCV infection and reinfection. [264][265][266][267] HCV accounts for 85-95% of mixed cryoglobulinemia, a common extrahepatic manifestation of HCV. The cryoglobulinemia occurs by HCV antigen-driven B cell clonal proliferation leading to the deposition of circulating immune complexes in small vessels of the skin, nerves, kidney, liver, and joints.…”