Omorodion O, Wilson IA. Structural and Biochemical Characterization of Cysteinylation in
Broadly Neutralizing Antibodies to HIV-1.
J Mol Biol 2021;
433:167303. [PMID:
34666044 PMCID:
PMC8641059 DOI:
10.1016/j.jmb.2021.167303]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 10/05/2021] [Accepted: 10/06/2021] [Indexed: 11/17/2022]
Abstract
Cysteinylation is a little-studied post-translational modification in antibodies.
Cysteinylation was identified in a lineage of bnAbs to HIV-1.
The cysteinylation modification is clearly visualized in the crystal structures.
Cysteinylation does not impair binding to antigen, compared to previous studies.
These findings provide further perspectives on the role of antibody cysteinylation.
Antibodies with exceptional breadth and potency have been elicited in some individuals during natural HIV-1 infection. Elicitation and affinity maturation of broadly neutralizing antibodies (bnAbs) is therefore the central goal of HIV-1 vaccine development. The functional properties of bnAbs also make them attractive as immunotherapeutic agents, which has led to their production and optimization for passive immunotherapy. This process requires in vitro manufacturing and monitoring of any heterogeneous expression, especially when subpopulations of antibodies are produced with varying levels of biological activity. Post-translational modification (PTM) of antibodies can contribute to heterogeneity and is the focus of this study. Specifically, we have investigated cysteinylation in a bnAb lineage (PCDN family) targeting the N332-glycan supersite on the surface envelope glycoprotein (Env) of HIV-1. This PTM is defined by capping of unpaired cysteine residues with molecular cysteine. Through chromatography and mass spectrometry, we were able to characterize subpopulations of cysteinylated and non-cysteinylated antibodies when expressed in mammalian cells. The crystal structures of two PCDN antibodies represent the first structures of a cysteinylated antibody and reveal that the cysteinylation in this case is located in CDRH3. Biophysical studies indicate that cysteinylation of these HIV-1 antibodies does not interfere with antigen binding, which has been reported to occur in other cysteinylated antibodies. As such, these studies highlight the need for further investigation of cysteinylation in anti-HIV and other bnAbs.
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