Engaging an HIV vaccine target through the acquisition of low B cell affinity

Low affinity is common for germline B cell receptors (BCR) seeding development of broadly neutralizing antibodies (bnAbs) that engage hypervariable viruses, including HIV. Antibody affinity selection is also non-homogenizing, insuring the survival of low affinity B cell clones. To explore whether this provides a natural window for expanding human B cell lineages against conserved vaccine targets, we deploy transgenic mice mimicking human antibody diversity and somatic hypermutation (SHM) and immunize with simple monomeric HIV glycoprotein envelope immunogens. We report an immunization regimen that focuses B cell memory upon the conserved CD4 binding site (CD4bs) through both conventional affinity maturation and reproducible expansion of low affinity BCR clones with public patterns in SHM. In the latter instance, SHM facilitates target acquisition by decreasing binding strength. This suggests that permissive B cell selection enables the discovery of antibody epitopes, in this case an HIV bnAb site.

Automated summary

Low affinity is common for germline B cell receptors (BCR) that develop broadly neutralizing antibodies (bnAbs) against hypervariable viruses like HIV. The non-homogenizing antibody affinity selection ensures the survival of low affinity B cell clones. By using transgenic mice mimicking human antibody diversity and somatic hypermutation (SHM), researchers demonstrate an immunization regimen that focuses B cell memory on the conserved CD4 binding site (CD4bs) through both traditional affinity maturation and the expansion of low affinity BCR clones with shared SHM patterns. This suggests that permissive B cell selection enables the discovery of antibody epitopes, such as an HIV bnAb site.