Background
HIV-1 infection alters the frequencies and functions of B cell subsets, which may be restored by combined antiretroviral therapy (cART). There is still a gap in our knowledge that limits our understanding of the maturation of autologous HIV-1 neutralizing antibodies (NAbs) during cART. Our goal was to interrogate the dynamics of B cell lineages pre- and post- cART in a chronic Simian-HIV infection model of juvenile rhesus macaques (RMs).
Methods
Nine RMs were infected at birth with a pathogenic SHIV and untreated for ~3-4 years. Six RMs were treated with daily cART for 13 months, while 3 RMs remained therapy-naïve because viremia <1000 RNA copies/ml. Purified IgG from plasma was tested for HIV-1 neutralization in TZM-bl cells, and structurally mapped on autologous HIV-1 envelope (Env) trimer via electron-microscopy-based polyclonal epitope mapping (EMPEM). We quantified peripheral blood (PBMC)-derived antigen-reactive B cells via FACS using autologous Env trimer. We generated B cell receptor (BCR) and transcriptome sequences of negatively-enriched single cells from PBMCs (10X Genomics) of SHIV-infected (N=9; ~270K B cells) and SHIV-naïve (N=3; ~16K B cells) RMs.
Results
Pre-cART plasma IgG in SHIV infection mapped to NAb epitopes on autologous Env, including V3-glycan and V2-apex broadly-NAbs (bNAbs), and post-cART IgG neutralized autologous SHIV with varied potencies indicative of NAb persistence during cART. In 6/9 SHIV-infected RMs, we detected HIV-1 Env-reactive memory B cells, even at 13 months post-cART in RMs on therapy. We identified computationally-inferred clonally-related BCRs in SHIV-infected RMs (+/- cART), including persisting IgG clones and strictly expanding IgG clones with increased numbers of cells post- versus pre- cART. Transcriptomics revealed 16 unique B cell clusters, including 3 clusters with memory B cell gene signatures that had predominantly cells from SHIV-infected RMs on cART and SHIV-naïve controls, compared to therapy-naïve SHIV-infected RMs, suggestive of cART-restored functional memory B cell subsets in infection. Ongoing transcriptomics will further delineate the nature and activation states of B cell clusters.
Conclusions
In this study, B cell clonal expansion underlies their maturation under cART, suggestive of a similar process in PLWH that may be driven by residual viremia within germinal centers. Future studies will evaluate the capacity of Abs in these B cell subsets to develop polyfunctional antiviral activities.
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