Development and Validation of a Novel Anti-Pathogenic Tau Conformation (TNT2) scFv Immuno-Gene Therapy - PROJECT SUMMARY
Tauopathies are a set of degenerative diseases that includes Alzheimer’s disease (AD) and AD-related
dementias. Several passive anti-tau immunotherapies are under development and/or in clinical trials. While hope
is high for therapeutic benefits, there is concern that they are not the right targets (e.g. bind total tau) and/or are
not delivered to the right place (i.e. not intraneuronal), which may significantly limit therapeutic benefit.
Alternatively, gene therapy delivery of antibody single chain fragment variables (scFvs), represents a more
robust approach to deliver pathological tau conformation-specific antibodies (right targets) within neurons
affected by tauopathy (right place). We developed a tau antibody that specifically recognize pathogenic tau
conformations directly connected to mechanisms of axonal and synaptic toxicity in neurons, called Tau N-
Terminal 2 (TNT2). This antibody binds tau when it undergoes modifications that cause conformation-dependent
display of an N-terminal motif called the phosphatase-activating domain (PAD). PAD exposure is an early
pathogenic change in human AD and other tauopathies linked with pathogenic modifications (e.g. oligomers or
phospho-tau) and toxicity. Thus, adapting TNT2 as a therapeutic agent has a potentially high impact. We will
use recombinant adeno-associated viruses (AAVs) to deliver the TNT2-scFv coupled to HaloTag protein and a
protein degradation signal (PDS) peptide to facilitate proteasomal breakdown of PAD exposed tau species.
Recent AAV advances, such as AAV CAP-B10 capsid, provide a novel non-invasive route to systemically deliver
AAVs that produce widespread CNS transduction further enhancing potential translatability of this approach. We
hypothesize that TNT2-scFv-Halo-PDS will effectively engage and degrade PAD exposed tau (Aim 1A) and
systemic delivery of AAV-TNT2-scFv-Halo-PDS will effectively deliver the scFv intraneuronally in the CNS and
subsequently rescue the phenotype of the PS19 mouse model of tauopathy (Aim 1B). In Aim 1A, we will develop
and validate the novel TNT2-scFv-Halo-PDS by testing heavy chain/light chain and light chain/heavy chain
configurations of the scFv and target engagement will be measured using a series of in-cell protein-protein
interaction assays in a HEK cell tauopathy model. In Aim 1B, we will deliver AAV-TNT2-scFv-Halo-PDS using
the AAV-CAP-B10 viral vector to allow non-invasive systemic delivery and widespread CNS expression in PS19
mice. First, we will test expression in the CNS and peripheral organs using wild-type mice. Then, we will perform
a disease prevention study (early AAV delivery) and a disease modifying study (mid-disease AAV delivery) in
PS19 mice. We will measure behavior/cognitive performance, scFv expression, target engagement, tau
neuropathology, neurodegeneration markers (neurons, synapses, etc.) and neuroinflammation markers.
Successful completion of this project will conclusively determine whether, or not, a highly novel immuno-gene
therapy for tauopathy (AAV-TNT2-scFv-Halo-PDS) holds promise as a potential therapy against tauopathy.
