Identification of β-amyloid species in canine cerebrospinal fluid by mass spectrometry

It is well known that several Aβ species, including Aβ40 and Aβ42, are present in cerebrospinal fluid (CSF). Experimental results suggest that these species could play a role in Alzheimer's disease and might also have diagnostic significance. In the present work, the canine CSF β-amyloid species profile has been identified by matrix-assisted laser desorption and ionization–time-of-flight/time of flight mass spectrometry (MALDI-TOF/TOF) analysis after immunoprecipitation with different Aβ-specific antibodies. The results show that species arising from combined β- and γ-secretase activities in humans, such as Aβ1–33, Aβ1–34, Aβ1–37, Aβ1–38, Aβ1–39, Aβ1–40, and Aβ1–42, are also present in dogs. Species arising from combined α- and β-secretase activities, as well as other Aβ-degrading enzymes, are also present in both human and canine CSF, with the exception of Aβ1–13, Aβ1–14, and Aβ1–18, which are not detected in dogs. A large number of species truncated at Glu-3 and Glu-11 have also been detected. To our knowledge, this work describes a most complete Aβ species profile from canine CSF. The similarities between the canine and human CSF Aβ profile reinforce the dog as a highly appropriate animal model for research in Alzheimer's disease.