Isolation of potent neutralizing antibodies from a survivor of the 2014 Ebola virus outbreak.

Antibodies targeting the Ebola virus surface glycoprotein (EBOV GP) are implicated in protection against lethal disease, but the characteristics of the human antibody response to EBOV GP remain poorly understood. We isolated and characterized 349 GP-specific monoclonal antibodies (mAbs) from the peripheral B cells of a convalescent donor who survived the 2014 EBOV Zaire outbreak. Remarkably, 77% of the mAbs neutralize live EBOV, and several mAbs exhibit unprecedented potency. Structures of selected mAbs in complex with GP reveal a site of vulnerability located in the GP stalk region proximal to the viral membrane. Neutralizing antibodies targeting this site show potent therapeutic efficacy against lethal EBOV challenge in mice. The results provide a framework for the design of new EBOV vaccine candidates and immunotherapies.

High-throughput sequencing analysis of post-liver transplantation HCV E2 glycoprotein evolution in the presence and absence of neutralizing monoclonal antibody.

Chronic hepatitis C virus (HCV) infection is the most common cause of end-stage liver disease, often leading to liver transplantation, in which case circulating virions typically infect the transplanted liver within hours and viral concentrations can quickly exceed pre-transplant levels. MBL-HCV1 is a fully human monoclonal antibody recognizing a linear epitope of the HCV E2 envelope glycoprotein (amino acids 412-423). The ability of MBL-HCV1 to prevent HCV recurrence after liver transplantation was investigated in a phase 2 randomized clinical trial evaluating six MBL-HCV1-treated subjects and five placebo-treated subjects. MBL-HCV1 treatment significantly delayed time to viral rebound compared with placebo treatment. Here we report results from high-throughput sequencing on the serum of each of the eleven enrolled subjects prior to liver transplantation and after viral rebound. We further sequenced the sera of the MBL-HCV1-treated subjects at various interim time points to study the evolution of antibody-resistant viral variants. We detected mutations at one of two positions within the antibody epitope--mutations of N at position 415 to D, K or S, or mutation of N at position 417 to S. It has been previously reported that N415 is not glycosylated in the wild-type E2 protein, but N417S can lead to glycosylation at position 415. Thus N415 is a key position for antibody recognition and the only routes we identified for viral escape, within the constraints of HCV fitness in vivo, involve mutating or glycosylating this position. Evaluation of mutations along the entire E1 and E2 proteins revealed additional positions that changed moderately before and after MBL-HCV1 treatment for subsets of the six subjects, yet underscored the relative importance of position 415 in MBL-HCV1 resistance.

Development of antigen-specific memory CD8+ T cells following live-attenuated chimeric West Nile virus vaccination.

ChimeriVax-WN02 is a novel live-attenuated West Nile virus (WNV) vaccine containing modified WNV premembrane (prM) and envelope (E) sequences inserted into the yellow fever 17D vaccine genome. We investigated the induction and evolution of CD8(+) T cell responses to a WNV envelope epitope, which is a dominant target in naturally infected HLA-A*02-positive individuals. WNV epitope-specific CD8(+) T cells were detected by HLA tetramer staining in 22 of 23 donors tested, with peak frequencies occurring between days 14 and 28. WNV epitope-specific T cells evolved from an effector phenotype to a long-lived memory phenotype. In the majority of donors, CD8(+) T cells were able to lyse targets expressing WNV envelope protein and produced macrophage inflammatory protein 1ß, interferon γ, and/or tumor necrosis factor α following envelope peptide stimulation. WNV E-specific CD8(+) T cell responses were detected for up to 1 year after vaccination. The evolution of this WNV-specific T cell response is similar to that observed in established, highly immunogenic vaccines.