Background:
Broadly neutralizing antibodies (bNAbs) show potential as complementary immunotherapy to combination anti-retroviral therapies for HIV-1 treatment yet infusion of a single bNAb selects for resistant variants. We developed an ex vivo assay that predicts bNAbs potential to achieve in vivo virologic response in people with HIV and allows investigation of viral resistance signatures.
Methods:
The ex vivo assay used pre-infusion CD4+ T cells from VRC607/ACTG5378 patients, a phase I study of the CD4 binding site (CD4bs) bNAbs VRC01LS (n=7) or VRC07-523LS (n=9) antiviral efficacy. Cells were activated and treated with various CD4bs bNAbs. Viral titers were assessed by p24 ELISA, escape variant signatures were characterized by sequencing and neutralization assays.
Results:
In VRC607/ACGT5378, 2 patients infused with VRC01LS and 8 with VRC07-523LS showed viremia decrease > 1 log10. Ex vivo assays using samples from 9 patients whose viremia decreased after VRC01LS (n=2) or VRC07-523LS (n=7) infusion evidenced >10-fold reduction in viral replication by the corresponding bNAb relative to assay control. Four patients that did not show an in vivo response post-bNAb infusion did not show viral suppression ex vivo by the respective bNAb indicating ex vivoassays recapitulated virological outcome observed in vivo. We also assessed more potent and broader next generation CD4bs bNAbs: VRC01v23, 1-18 and N6 in this assay. We found that there were complementary suppression profiles for these 3 bNAbs with some assays showing suppression by 1 or 2 but not all 3 bNAbs dependent on the patient sample used. Further, most VRC01LS or VRC07-523LS escape strains were neutralized by 1-18, N6 or VRC01v23, supporting potential for combined therapy with these bNAbs. 1-18, N6 and VRC01v23 escape variants had charge changes, glycan loss or shifts in the ß23-V5. Resistant strains to 1-18 lacked R308 while N6 escape strains lacked glycan N276 or D279. Moreover, genetic signatures in ex vivo outgrowth viruses were also found in plasma viral sequences, suggesting that the ex vivo assay can identify circulating bNAb resistant variants in these patients.
Conclusions:
In vivo and ex vivo effect of HIV-1 bNAbs comparison suggest that the ex vivo assay shows potential to reliably predict bNAbs antiviral effect in clinical trials and contribute to analysis of resistant strains that could emerge in vivo. Our data indicate that optimal combinations of CD4bs bNAbs can be used to mitigate viral resistance to bNAb-based immunotherapies.
Comparative suppression profiles of VRC01LS, VRC07-523LS, VRC01v23, N6LS and 1-18LS treated conditions in ex vivo assay