Fig. 1

Representative images of immunohistochemistry with PHF-1 antibody (panel a), [¹⁸F]-AV-1451 phosphor screen autoradiography (panel b), self-block (panel c), and [¹⁸F]-AV-1451 nuclear emulsion autoradiography followed by PHF-1 immunostaining in AD (positive control) and CTE brains (panels d and e). A strong [¹⁸F]-AV-1451 binding signal was observed in cortical regions containing tangles in AD (panels a and b arrows). No [¹⁸F]-AV-1451 binding was detected in CTE slices containing abundant tau aggregates (panel a arrowheads) with the exception of strong binding to the choroid plexus in case#1 and to leptomeninges in cases #1 and #3 (panel b red stars) corresponding to off-target to leptomeningeal melanocytes. A weaker signal was present in hippocampus of case #2 (panel b arrow) where scarce classic AD NFTs (panel a arrow) were present along with abundant CTE tau aggregates (panel a arrowhead). The signal was blocked by adding unlabeled AV-1451 (panel c). [¹⁸F]-AV-1451 nuclear emulsion autoradiography confirmed a strong accumulation of silver grains colocalizing with classic NFTs in AD (panel d), and with incidental classic NFTs in the hippocampus of CTE case #2 (panel e). No detectable accumulations of silver grains were observed in association with CTE tau aggregates (panel d). Strong accumulation of silver grains also colocalized with leptomeningeal melanocytes in CTE cases #1 and #3 (off-target binding) (panel e). Scale bars = 1 cm (panels a, b, c) and 20 μm (panels d and e)