Receptor-based antibodies generated by templated insertions in the switch region

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Author
Date
2020Type
- Doctoral Thesis
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yes
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Abstract
We recently isolated, from malaria-exposed individuals, antibodies that carried a large DNA fragment encoding the LAIR1 extracellular domain inserted in between the VH and DJH or in the switch regions of the immunoglobulin gene locus. These genomic configurations result in the production of antibodies that display an LAIR1 extracellular domain at the tip of the HCDR3 or at the VH-CH1 junction. The LAIR1-containing antibodies recognize certain Plasmodium falciparum (P. falciparum) antigens, named RIFINs, which are expressed on the surface of infected erythrocytes. To investigate the general relevance of such receptor-based antibodies, we searched for antibodies containing LILRB1, an MHC-I binding inhibitory receptor that was suggested to bind to certain RIFINs. By screening the sera of malaria-exposed individuals, I discovered natural antibodies containing LILRB1 domains that bind to various malaria isolates. Analysis of the cDNA and gDNA revealed LILRB1 inserts in the switch region that, after appropriate splicing, led to the expression of domain 3 (D3) and D4 on the VH-CH1 elbow. Moreover, I found that these LILRB1-containing antibodies recognize a handful of RIFINs on P. falciparum-infected erythrocytes, which may serve as the potential candidates for the development of a malaria vaccine. The cryo-EM structure of RIFIN-V2 domain in complex with the LILRB1-containing antibody showed that the inserted domains open the VH elbow without interfering with VH-VL and CH1-CL pairing. The discovery of receptor-based antibodies inspired us to use this molecular platform for antibody engineering. I generated bispecific antibodies by inserting VHH or single-chain Fv domains between VH and the CH1 region of specific antibodies. The recombinant antibodies are well expressed, and their dual antigen specificities were validated by antigen binding analyses. This finding served as a proof of principle that insertion of additional domains in the elbows of conventional antibodies could be used to generate novel bispecific molecules for diagnostic or therapeutic purposes. Collectively, my work illustrates a general mechanism for the generation and selection of receptor-based antibodies, i.e. antibodies that incorporate the pathogen receptor thus effectively hijacking pathogen immune evasion. Show more
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https://doi.org/10.3929/ethz-b-000467490Publication status
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Contributors
Examiner: Sallusto, Federica
Examiner: Lanzavecchia, Antonio
Examiner: Kopf, Manfred
Examiner: Daubenberger, Claudia
Publisher
ETH ZurichSubject
antibody; Immunology and Microbiology Section; malaria; protein engineering; class switch recombinationOrganisational unit
09604 - Sallusto, Federica / Sallusto, Federica
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