Development of Brain MRI Contrast Agents

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We have made substantial progress towards Aims 1-5, 7&8. Specifically: a) We have demonstrated that a mutant mouse transferrin receptor binding nanobody with strong pH dependent unbinding crosses the BBB in vivo approximately 500 times more effectively than a control nanobody. b) We have demonstrated that the mutant mouse transferrin receptor binding nanobody can carry other nanobodies as cargo across the mouse BBB. A tandem dimer of nanobodies that bind to the P2X7 receptor has been used as a model cargo. c) We have shown that cargo transported across the BBB can be detected in capillary depleted brain lysates and histochemically at their target sites between 1 and 16 hours after injection. d) We have demonstrated that there is a strong nonlinearity in the dose-response curve for the BBB crossing nanobodies. At doses greater than 30 nmol/kg injected intravenously, there is no greater brain accumulation of cargo. The maximum brain concentration achieved was 4.5 nM. This concentration is an order of magnitude too low for MRI detection of iron oxide nanoparticles. We therefore have decided to switch to PET imaging for further development molecular contrast imaging agents. e) We are developing methods to conjugate nanobodies to the positron emitting Copper-64 for PET scans. f) We have established a new collaboration with Dr. Dale Kiesewetter and his research group to perform PET scans in living mice at multiple time points after injection. g) We have initiated new collaborations with M Janoswki at U Maryland, D Sehlin and S. Syvanen at Uppsala U, and I Huggins at Ionis Pharmaceuticals to perform additional imaging studies using our BBB crossing nanobody constructs. h) We have established new collaborations with Dr F. Nugent at USUHS, Dr. N. Plesnila at U Munich, and Dr. F. Porreca at U Arizona to test our nanobody constructs for efficacy as BBB crossing P2X7 receptor blocking therapeutics in mouse models of TBI, stroke, and post-traumatic headache. i) Ongoing work by our collaborators at Washington University indicates that our SARS-CoV-2 nanobodies have potential for use in real time environmental surveillance of aerosols and for detection of SARS-CoV-2 in exhaled breath.