Charting the ultrasound-facilitated voyage of a novel anti-tau antibody compared to a tau-targeted fusion protein into the brain using NanoSIMS

The blood-brain barrier is a major obstacle in treating brain diseases, including Alzheimer’s disease. Low-intensity scanning ultrasound in combination with intravenously injected microbubbles (SUS^+MB) is a new modality extensively explored by us to focally deliver drugs that either do not enter the brain or do so only at very low levels (Blackmore et al., Neuron 2023). A huge problem (in terms of costs and efficacy) is that only 1/1,000 of intravenously injected therapeutic antibodies, such as Aducanumab, arrive in the brain, which constitutes a huge waste of these injected antibodies. With SUS^+MB, we can achieve up to 12-fold increased antibody levels in the brain. However, the underlying mechanisms of drug (e.g. tau antibody) uptake by SUS^+MB and the drug’s ‘journey’ into the brain towards its target (e.g. intraneuronal tau) are not understood. Potential uptake mechanism in response to SUS^+MB are (i) paracellular transport (opened tight junctions), (ii) sonoporation (pores spanning endothelial cells) and (iii) transcytoplasmic transport (endocytosis by endothelial cells). An unsolved issue is drug degradation upon endolysosomal targeting.

We propose a project to comparatively investigate our lead anti-tau antibody RNJ1 (Cruz, Brain 2025) together with a newly generated cell-penetrant RNJ1 variant in N2A and brain endothelial cells. We will then deliver the antibodies with and without SUS^+MB in tau transgenic K3 mice. To control for the role of the Fc receptor (that these antibodies have) we will include a construct using a single chain variant of the antibody (that lacks the Fc portion) coupled with an intracellular receptor, TRIM21. We will label the antibodies and the third agent with three different stable isotopes or ASOs followed by Nanoscale Secondary Ion Mass Spectrometry (NanoSIMS, technique established, King, Chem Sci 2024), which enables visualisation of drug localisation and cellular passage at an unprecedented organelle level. Thereby, we will learn about the intracellular route and clearance of these drugs as they cross the blood-brain barrier and travel through the interstitial space to be taken up by target neurons. We will understand which of the three uptake routes are used and which of the three drugs get trapped in the brain endothelial cells (which constitute the blood-brain barrier) and are potentially shuttled back into the capillaries. Together, this insight will be used to further engineer the tau antibodies to increase their efficacy which will be explored in K3 mice by conducting proteomic, behavioural and functional analyses and assessing tau levels as well as potential reductions in pathological tau.

This scholarship is part of the MIND-AD CRE Scholarship program which will support three students across its advertised projects. Applicants will be required to submit an online application and attend an interview.