Biology subjects

Bonnettaz, B.

Publications and source records attributed to Bonnettaz, B..

3 recordsLinked to original sources

bioRxiv2026

Clonotype specificity distinguishes epitope-tailored and permissive somatic hypermutation

Identifying antibody features that reliably encode epitope specificity poses a major barrier towards modeling antigen-antibody interactions. Affinity maturation offers a unique opportunity to probe the molecular basis of antigen-antibody interactions by revealing how individual somatic hypermutations (SHM) refine antibody binding. Using SARS-CoV-2 spike-specific germinal center B-cell repertoires, we show that antibodies harboring multiple SHMs that are restricted to their respective clonotypes (clonotype-restricted SHMs) preferentially recognize cryptic epitopes. We structurally characterized three such antibodies: two recognized a cryptic epitope on the receptor-binding domain whereas a third bound an N-terminal domain epitope that is almost entirely occluded in prefusion spike. In contrast, SHMs shared across multiple clonotypes using the same V gene recur across antibodies targeting diverse antigens but generally fail to enhance affinity when introduced into diverse antibody backgrounds. Together, these findings define a spectrum of SHM behavior, distinguishing epitope-tailored mutations from broadly recurrent but largely permissive substitutions.

immunology↗

bioRxiv2026

Universally conserved isoasparylation sustains ribosome biogenesis and function

All living beings use ribosomes to synthesize proteins from -amino acids. Inherited from our common ancestor, a few universally conserved ribosome biogenesis steps, introducing essential ribosomal RNA modifications, have survived to our days. However, it was unknown whether similar primordial core mechanisms could also target ribosomal proteins. Here we show that the assembly and the function of ribosomes depend on the installation of an unusual {beta}-amino acid, isoaspartate, within the ribosomal protein uS11. In bacteria, mitochondria, and plastids, this modification is catalyzed by the metzincin-like hydrolase YbeY, whereas in archaea and eukaryotes, it is introduced by the atypical kinase Fap7. The formation of this strategically positioned isoaspartate enables correct maturation of the small ribosomal subunit to support protein synthesis and normal cell physiology.

biochemistry↗

bioRxiv2026

Egyptian rousette bat humoral immunity to H9 influenza hemagglutinin

In mammals, antibodies are central to antiviral defense, but they can also impose selective pressure that drives viral evolution. The interplay between viral antigenic variation and host antibody diversification constitutes a molecular arms race that influences pathogenicity, transmission, and spillover risk. Bats are reservoirs for zoonotic viruses with pandemic potential yet they appear to tolerate infection without overt disease. Although distinctive features of bat innate immunity have been described, the role of adaptive immunity--particularly antibody-mediated responses--remains largely undefined. Moreover, how antibody evolutionary pressure operates in bats is unknown, in part because tools to interrogate bat B cell responses at the monoclonal level are limited. Here, we developed a yeast surface display library of bat antibodies derived from splenic RNA of wild-caught Egyptian rousette bats to interrogate humoral responses to the bat-derived H9 influenza hemagglutinin. We isolated monoclonal antibodies recognizing the hemagglutinin (HA) antigen and defined their gene usage, somatic hypermutation frequency, binding affinities, and breadth. We then used cryo-EM to structurally characterize three bat antibodies in complex with HA engaging distinct antigenic sites. Together, these data enable direct comparison with human anti-influenza antibodies highlighting similarities in humoral immunity across mammals and provides a tool to examine bat antibody responses to other potential zoonotic viruses.

immunology↗