Human immunoglobulin gene allelic variation impacts germline-targeting vaccine priming.

Vaccine priming immunogens that activate germline precursors for broadly neutralizing antibodies (bnAbs) have promise for development of precision vaccines against major human pathogens. In a clinical trial of the eOD-GT8 60mer germline-targeting immunogen, higher frequencies of vaccine-induced VRC01-class bnAb-precursor B cells were observed in the high dose compared to the low dose group. Through immunoglobulin heavy chain variable (IGHV) genotyping, statistical modeling, quantification of IGHV1-2 allele usage and B cell frequencies in the naive repertoire for each trial participant, and antibody affinity analyses, we found that the difference between dose groups in VRC01-class response frequency was best explained by IGHV1-2 genotype rather than dose and was most likely due to differences in IGHV1-2 B cell frequencies for different genotypes. The results demonstrate the need to define population-level immunoglobulin allelic variations when designing germline-targeting immunogens and evaluating them in clinical trials.

A first-in-human germline-targeting HIV nanoparticle vaccine induced broad and publicly targeted helper T cell responses.

The engineered outer domain germline targeting version 8 (eOD-GT8) 60-mer nanoparticle was designed to prime VRC01-class HIV-specific B cells that would need to be matured, through additional heterologous immunizations, into B cells that are able to produce broadly neutralizing antibodies. CD4 T cell help will be critical for the development of such high-affinity neutralizing antibody responses. Thus, we assessed the induction and epitope specificities of the vaccine-specific T cells from the IAVI G001 phase 1 clinical trial that tested immunization with eOD-GT8 60-mer adjuvanted with AS01B. Robust polyfunctional CD4 T cells specific for eOD-GT8 and the lumazine synthase (LumSyn) component of eOD-GT8 60-mer were induced after two vaccinations with either the 20- or 100-microgram dose. Antigen-specific CD4 T helper responses to eOD-GT8 and LumSyn were observed in 84 and 93% of vaccine recipients, respectively. CD4 helper T cell epitope "hotspots" preferentially targeted across participants were identified within both the eOD-GT8 and LumSyn proteins. CD4 T cell responses specific to one of these three LumSyn epitope hotspots were observed in 85% of vaccine recipients. Last, we found that induction of vaccine-specific peripheral CD4 T cells correlated with expansion of eOD-GT8-specific memory B cells. Our findings demonstrate strong human CD4 T cell responses to an HIV vaccine candidate priming immunogen and identify immunodominant CD4 T cell epitopes that might improve human immune responses either to heterologous boost immunogens after this prime vaccination or to other human vaccine immunogens.

Human immunoglobulin gene allelic variation impacts germline-targeting vaccine priming.

Vaccine priming immunogens that activate germline precursors for broadly neutralizing antibodies (bnAbs) have promise for development of precision vaccines against major human pathogens. In a clinical trial of the eOD-GT8 60mer germline-targeting immunogen, higher frequencies of vaccine-induced VRC01-class bnAb-precursor B cells were observed in the high dose compared to the low dose group. Through immunoglobulin heavy chain variable (IGHV) genotyping, statistical modeling, quantification of IGHV1-2 allele usage and B cell frequencies in the naive repertoire for each trial participant, and antibody affinity analyses, we found that the difference between dose groups in VRC01-class response frequency was best explained by IGHV1-2 genotype rather than dose and was most likely due to differences in IGHV1-2 B cell frequencies for different genotypes. The results demonstrate the need to define population-level immunoglobulin allelic variations when designing germline-targeting immunogens and evaluating them in clinical trials. One-Sentence Summary: Human genetic variation can modulate the strength of vaccine-induced broadly neutralizing antibody precursor B cell responses.

Vaccination induces HIV broadly neutralizing antibody precursors in humans.

Broadly neutralizing antibodies (bnAbs) can protect against HIV infection but have not been induced by human vaccination. A key barrier to bnAb induction is vaccine priming of rare bnAb-precursor B cells. In a randomized, double-blind, placebo-controlled phase 1 clinical trial, the HIV vaccine-priming candidate eOD-GT8 60mer adjuvanted with AS01B had a favorable safety profile and induced VRC01-class bnAb precursors in 97% of vaccine recipients with median frequencies reaching 0.1% among immunoglobulin G B cells in blood. bnAb precursors shared properties with bnAbs and gained somatic hypermutation and affinity with the boost. The results establish clinical proof of concept for germline-targeting vaccine priming, support development of boosting regimens to induce bnAbs, and encourage application of the germline-targeting strategy to other targets in HIV and other pathogens.

Isolation and characterization of cross-neutralizing coronavirus antibodies from COVID-19+ subjects.

SARS-CoV-2 is one of three coronaviruses that have crossed the animal-to-human barrier and caused widespread disease in the past two decades. The development of a universal human coronavirus vaccine could prevent future pandemics. We characterize 198 antibodies isolated from four COVID-19+ subjects and identify 14 SARS-CoV-2 neutralizing antibodies. One targets the N-terminal domain (NTD), one recognizes an epitope in S2, and 11 bind the receptor-binding domain (RBD). Three anti-RBD neutralizing antibodies cross-neutralize SARS-CoV-1 by effectively blocking binding of both the SARS-CoV-1 and SARS-CoV-2 RBDs to the ACE2 receptor. Using the K18-hACE transgenic mouse model, we demonstrate that the neutralization potency and antibody epitope specificity regulates the in vivo protective potential of anti-SARS-CoV-2 antibodies. All four cross-neutralizing antibodies neutralize the B.1.351 mutant strain. Thus, our study reveals that epitopes in S2 can serve as blueprints for the design of immunogens capable of eliciting cross-neutralizing coronavirus antibodies.

Isolation and Characterization of Cross-Neutralizing Coronavirus Antibodies from COVID-19+ Subjects.

SARS-CoV-2 is one of three coronaviruses that have crossed the animal-to-human barrier in the past two decades. The development of a universal human coronavirus vaccine could prevent future pandemics. We characterized 198 antibodies isolated from four COVID19+ subjects and identified 14 SARS-CoV-2 neutralizing antibodies. One targeted the NTD, one recognized an epitope in S2 and twelve bound the RBD. Three anti-RBD neutralizing antibodies cross-neutralized SARS-CoV-1 by effectively blocking binding of both the SARS-CoV-1 and SARS-CoV-2 RBDs to the ACE2 receptor. Using the K18-hACE transgenic mouse model, we demonstrate that the neutralization potency rather than the antibody epitope specificity regulates the in vivo protective potential of anti-SARS-CoV-2 antibodies. The anti-S2 antibody also neutralized SARS-CoV-1 and all four cross-neutralizing antibodies neutralized the B.1.351 mutant strain. Thus, our study reveals that epitopes in S2 can serve as blueprints for the design of immunogens capable of eliciting cross-neutralizing coronavirus antibodies.

Generation of a cost-effective cell line for support of high-throughput isolation of primary human B cells and monoclonal neutralizing antibodies.

The isolation of human monoclonal antibodies (mAbs) arising from natural infection with human pathogens has proven to be a powerful technology, facilitating the understanding of the host response to infection at a molecular level. mAbs can reveal sites of vulnerability on pathogens and illuminate the biological function of the antigenic targets. Moreover, mAbs have the potential to be used directly for therapeutic applications such as passive delivery to prevent infection in susceptible target populations, and as treatment of established infection. The isolation of antigen-specific B cells from vaccine trials can also assist in deciphering whether the desired B cells are being targeted by a given vaccine. Several different processes have been developed to isolate mAbs, but all are generally labor-intensive and result in varying degrees of efficiency. Here, we describe the development of a cost-effective feeder cell line that stably expresses CD40-ligand, interleukin-2 and interleukin-21. Sorting of single B cells onto a layer of irradiated feeder cells sustained antibody production that permits functional screening of secreted antibodies in a manner that enables subsequent recovery of B cells for recombinant antibody cloning. As a proof of concept, we show that this approach can be used to isolate B cells that secrete antibodies that neutralize human papilloma virus (HPV) from participants of an HPV vaccine study.

Analysis of a SARS-CoV-2-Infected Individual Reveals Development of Potent Neutralizing Antibodies with Limited Somatic Mutation.

Antibody responses develop following SARS-CoV-2 infection, but little is known about their epitope specificities, clonality, binding affinities, epitopes, and neutralizing activity. We isolated B cells specific for the SARS-CoV-2 envelope glycoprotein spike (S) from a COVID-19-infected subject 21 days after the onset of clinical disease. 45 S-specific monoclonal antibodies were generated. They had undergone minimal somatic mutation with limited clonal expansion, and three bound the receptor-binding domain (RBD). Two antibodies neutralized SARS-CoV-2. The most potent antibody bound the RBD and prevented binding to the ACE2 receptor, while the other bound outside the RBD. Thus, most anti-S antibodies that were generated in this patient during the first weeks of COVID-19 infection were non-neutralizing and target epitopes outside the RBD. Antibodies that disrupt the SARS-CoV-2 S-ACE2 interaction can potently neutralize the virus without undergoing extensive maturation. Such antibodies have potential preventive and/or therapeutic potential and can serve as templates for vaccine design.