Rescue of HIV-1 broad neutralizing antibody-expressing B cells in 2F5 VH× VL knockin mice reveals multiple tolerance controls

L Verkoczy, Y Chen, H Bouton-Verville… - The Journal of …, 2011 - journals.aai.org
L Verkoczy, Y Chen, H Bouton-Verville, J Zhang, M Diaz, J Hutchinson, YB Ouyang…
The Journal of Immunology, 2011journals.aai.org
The HIV-1 broadly neutralizing Ab (bnAb) 2F5 has been shown to be poly-/self-reactive in
vitro, and we previously demonstrated that targeted expression of its VDJ rearrangement
alone was sufficient to trigger a profound B cell developmental blockade in 2F5 VH knockin
(KI) mice, consistent with central deletion of 2F5 H chain-expressing B cells. In this study, we
generate a strain expressing the entire 2F5 bnAb specificity, 2F5 VH× VL KI mice, and find
an even higher degree of tolerance control than observed in the 2F5 VH KI strain. Although …
Abstract
The HIV-1 broadly neutralizing Ab (bnAb) 2F5 has been shown to be poly-/self-reactive in vitro, and we previously demonstrated that targeted expression of its VDJ rearrangement alone was sufficient to trigger a profound B cell developmental blockade in 2F5 V H knockin (KI) mice, consistent with central deletion of 2F5 H chain-expressing B cells. In this study, we generate a strain expressing the entire 2F5 bnAb specificity, 2F5 V H× V L KI mice, and find an even higher degree of tolerance control than observed in the 2F5 V H KI strain. Although B cell development was severely impaired in 2F5 V H× V L KI animals, we demonstrate rescue of their B cells when cultured in IL-7/BAFF. Intriguingly, even under these conditions, most rescued B cell hybridomas produced mAbs that lacked HIV-1 Envelope (Env) reactivity due to editing of the 2F5 L chain, and the majority of rescued B cells retained an anergic phenotype. Thus, when clonal deletion is circumvented, κ editing and anergy are additional safeguards preventing 2F5 V H/V L expression by immature/transitional B cells. Importantly, 7% of rescued B cells retained 2F5 V H/V L expression and secreted Env-specific mAbs with HIV-1–neutralizing activity. This partial rescue was further corroborated in vivo, as reflected by the anergic phenotype of most rescued B cells in 2F5 V H× V L KI× Eμ-Bcl-2 transgenic mice and significant (yet modest) enrichment of Env-specific B cells and serum Igs. The rescued 2F5 mAb-producing B cell clones in this study are the first examples, to our knowledge, of in vivo-derived bone marrow precursors specifying HIV-1 bnAbs and provide a starting point for design of strategies aimed at rescuing such B cells.
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