Background
Despite the efficient suppression of HIV-1 replication with combined antiretroviral therapy, viral latency is a barrier to HIV cure. Bispecific antibodies against Env and CD3 have resulted in the ex vivo killing of HIV-containing cells from PLWH. However, the low level of Env expression on the cell surface and the sequence variation in the env protein highlight the need for alternative approaches. We previously generated bispecific TCR mimic (TCRm) reagents against CD3 and HIV-1 Pol region, capable of linking CTLs to infected cells and promoting target cell lysis. Based on this ex vivo killing capability, we investigated whether the TCR-mimic single-chain diabodies (ScDb) could reduce the provirus and delay viral rebound post ATI.
Methods
Novel BLT hu-mice generated from donors with the HLA-A*02:01 allele were infected with transmitted/ founder (T/F) virus HIVsuma. Viremia was suppressed on cART. ScDb HI12 against the Pol region and control ScDb H2 against a p53 epitope were used to treat the animals from 3 to 5 weeks post inoculation. ScDb in vivo kinetics were measured. HI12 or H2 were administered daily to animals with partially suppressed viremia. Weekly plasma viral load and proviral reservoir size by IPDA on cART and viral rebound after cART interruption were measured. CD4 depletion and T cell activation were also evaluated.
Results
With this HLA-A allele-specific BLT humanized mice, we found the in vivo half-life of TCRm ScDb post IP injection was 3.9 hrs, peaking at 2.4 ug/ml. TCRm ScDb was well tolerated in BLT hu-mice with stable bodyweight. TCRm ScDb HI12 added to early cART achieved suppression quicker than the H2 control group. CD38+HLA-DR+ double positive population was significantly elevated in CD4+ and CD8+ T cells during the HI12 treatment period. Intact (P=0.026), 3’ defective (p=0.002), and total (p=0.007) HIV proviruses in splenocytes were significantly decreased post HI12 treatment, whereas the 5’ (p=0.295) defective proviruses did not show a significant decrease. In an independent experiment, the viral rebound time was significantly delayed (p=0.0026) in HI12 treated animals over H2 control treated ones.
Conclusions
Using HLA-A matched BLT mice, the addition of TCRm ScDb targeting Pol epitope in corresponding HLA complexes during early ART increased T cell immune activation and reduced the intact provirus burden on ART resulting in a delay of viral rebound after cART interruption. The use of TCRm ScDb strategies warrants further clinical studies towards HIV cure.