Molecular evolution of broadly neutralizing Llama antibodies to the CD4-binding site of HIV-1.

Laura E Mccoy,Paul Kellam,Robin A Weiss,Willie Koh,Theo Verrips,Ariberto Fassati,Dan Frampton,Rachael Bashford-Rogers,Vanina Grippo,Michael S Seaman,Nika M Strokappe,Luke Granger,Ian Anderson,Lucy Rutten,Alexander Kliche,Gillian Dekkers,Ronald C Desrosiers

doi:10.1371/journal.ppat.1004552

Abstract

To date, no immunization of humans or animals has elicited broadly neutralizing sera able to prevent HIV-1 transmission; however, elicitation of broad and potent heavy chain only antibodies (HCAb) has previously been reported in llamas. In this study, the anti-HIV immune responses in immunized llamas were studied via deep sequencing analysis using broadly neutralizing monoclonal HCAbs as a guides. Distinct neutralizing antibody lineages were identified in each animal, including two defined by novel antibodies (as variable regions called VHH) identified by robotic screening of over 6000 clones. The combined application of five VHH against viruses from clades A, B, C and CRF_AG resulted in neutralization as potent as any of the VHH individually and a predicted 100% coverage with a median IC50 of 0.17 µg/ml for the panel of 60 viruses tested. Molecular analysis of the VHH repertoires of two sets of immunized animals showed that each neutralizing lineage was only observed following immunization, demonstrating that they were elicited de novo. Our results show that immunization can induce potent and broadly neutralizing antibodies in llamas with features similar to human antibodies and provide a framework to analyze the effectiveness of immunization protocols.

Highlights

HIV transmission remains a huge global public health problem
Recent major advances in identifying broad and potent HIV neutralizing monoclonal antibodies provide invaluable reagents for the development of these strategies to prevent HIV infection. It is well-established that passive infusion of neutralizing mAb can prevent SHIV infection [8,9,10,11,12,13] and recently it was shown that a mAb can treat infection in non-human primate (NHP) models [14]
We previously reported the heavy chain only antibody J3, which potently neutralizes more than 95% of HIV strains, and was induced by immunization

Summary

Introduction

HIV transmission remains a huge global public health problem (www.UNAIDS.org). To reduce spread of the virus new prevention methods are being developed based on recent advances in the molecular virology of HIV. Recent major advances in identifying broad and potent HIV neutralizing monoclonal antibodies (mAb) provide invaluable reagents for the development of these strategies to prevent HIV infection It is well-established that passive infusion of neutralizing mAb can prevent SHIV infection [8,9,10,11,12,13] and recently it was shown that a mAb can treat infection in non-human primate (NHP) models [14]. Recent in vitro work has shown increased neutralization coverage can be achieved by combining the newly identified broadly neutralizing mAb [19,20] These findings highlight the need to (a) induce multiple neutralizing antibody lineages for a protective antibody-based vaccine and (b) the potential need to use combinations of purified mAb in therapeutic or prophylactic settings

Results

Discussion

Conclusion