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1861
HBsAg-redirected T cells have potent antiviral activity in
HBV-infected human liver chimeric mice
Robert Kruse1, Thomas Shum1, Zhongzhen Yi1, Mercedes Barzi1,
Xavier Legras1, Beatrice Bissig-Choisat1, Christina Whitten-Bauer2,
Urtzi Garaigorta2, Stephen Gottschalk1, Karl-Dimiter Bissig1; 1Center
for Cell and Gene Therapy, Baylor College of Medicine, Houston,
TX; 2The Scripps Research Institute, La Jolla, CA
Current drug regimens can only suppress chronic hepatitis B
virus (HBV) infection, and a need for a permanent cure for
this patient population remains. In patients who spontaneously
clear the virus, an effective T cell response infiltrates the liver,
but patients with chronic HBV infection have deficient antiviral
T cells. We sought to solve this problem by engineering T
cells with a chimeric antigen receptor (CAR) having specificity
toward the HBV surface antigen (HBsAg), which accumulates
on the surface of infected hepatocytes. A CAR links a single
chain variable fragment (scFv) to signaling domains, resulting
in T cell activation in the presence of target antigen. Previous
studies established that HBsAg targeting CAR-T cells were
efficacious at eliminating HBV positive cell lines and in clearing
covalently closed circular HBV DNA (cccDNA) in primary
human hepatocytes in cell culture. HBV CAR-T cells were also
tested in a transgenic HBV mouse model, exhibiting a modest
reduction in viral loads that was ultimately transient in vivo,
with levels rebounding and a lack of CAR-T cell persistence.
Since the clearance of HBV can’t be tested in the transgenic
model given HBV is integrated into the host genome, we sought
to test CAR-T cell therapy in a clinically relevant setting with
authentic virus. We employed human liver chimeric mice,
which can be infected with HBV and possess episomal cccDNA
genomes. In order to facilitate clinical development, we sought
to identify a human derived scFv against HBsAg that would not
be expected to provoke an immune response in patients, versus
using murine derived scFv’s. We identified an scFv that could
potently activate T cells in vitro, resulting in complete killing of
an HBV positive cell line at 1 week, while sparing an HBV neg-
ative HepG2 control. Furthermore, CAR-T cells produced high
levels of INF-gamma, IL-2, and TNF-alpha in response to both
soluble and cell-associated HBsAg. We then evaluated CAR-T
cells in HBV-infected human liver chimeric mice with serum HBV
levels of 10^7 – 10^8 copies/mL DNA and 10-50,000 ng/
mL HBsAg. We found that a single dose of CAR-T cells could
decrease HBsAg levels up to 2 logs, and decrease HBV DNA
levels up to 3 logs post infusion. CAR-T cells appeared to mediate
cytotoxic killing of a portion of infected hepatocytes in vivo
suggested by a surrogate decrease in human serum albumin
levels in the mice. Control CAR-T cells possessing an EGFRvIII
antigen specificity had no antiviral effects in HBV-infected
mice. In summary, HBsAg-specific CAR-T cells demonstrate an
encouraging antiviral response in humanized mice and should
be clinically explored as new line of therapy against HBV.
Disclosures:
Robert Kruse - Patent Held/Filed: Baylor College of Medicine, Celgene
Beatrice Bissig-Choisat - Patent Held/Filed: Baylor College of Medicine, Cellgene
Karl-Dimiter Bissig - Consulting: Galapagos ; Grant/Research Support: BASF;
Patent Held/Filed: Celgene, Baylor College of Medcine
The following people have nothing to disclose: Thomas Shum, Zhongzhen Yi,
Mercedes Barzi, Xavier Legras, Christina Whitten-Bauer, Urtzi Garaigorta, Stephen
Gottschalk
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发表于 2016-11-23 14:26