NT4X-167; Novel N-terminal Aβ specific antibody, prevents in vitro and in vivo toxicity of highly toxic Aβ4-42 species

Objectives: The novel monoclonal antibody (NT4X-167) specifically reacts with N-truncated Aβ at position 4 of Aβ. It binds N-truncated Aβ under native and denaturing conditions but only rescues in vitro toxicity of Aβ4-42 and not that of pyroglutamate AβpE3–42. One objective was to determine whether the NT4X-167 antibody and its respective Fab fragment could prevent behavioral deficits (Y-Maze), caused by Aβ4-42 injection in wildtype mice. Another was to determine if the antibody and its respective Fab could rescue the in vivo toxicity of Aβ4-42 in the Tg4-42 mouse model, by using passive immunization. Methods: Cell toxicity assay, in vivo toxicity, Y-Maze, mAB antibody production, immunostaining, passive immunization. Results: The novel Aβ4-x immunoreactive antibody NT4X-167 detected high molecular weight aggregates derived from N-truncated Aβ species. Phenylalanine at position four of Aβ was imperative for antibody binding. Both full-length and the Fab fragment of the antibody were able to prevent the in vitro toxicity caused by Aβ4-42 in rat primary cortical neuron cultures. Aβ4-42 IntraCerebroVentricular injection into wildtype mice induced a behavioral deficit, shown as a reduction in alteration rate in a Y-Maze, which was prevented using the NT4X-167. The Fab fragment of the antibody, at a higher dosage, was also able to prevent the behavioral deficit in a replicate experiment. The passive immunization was able to rescue both spatial memory deficits and significantly mitigate neuron loss. Conclusions: NT4X-167 and Fab demonstrate binding and prevention of Aβ4-42 toxicity in vitro and in vivo. NT4X full length antibody and Fab prevent Aβ4-42 induced behavioral deficits in wildtype mice. Functionally, the full length antibody and its respective Fab fragment exhibit the same profile. It would thus be of great interest to study the structural binding characteristics of the NT4X-167, represented by its Fab fragment, to the highly toxic N-truncated Aβ4-x species.