Epitope alteration for detecting auto-antibodies of beta-amyloid in serum

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Alzheimer’s disease (AD) is an emerging public health crisis that poses a huge societal burden. The total payments in 2015 for all individuals with AD are estimated at $226 billion in US. To reduce the cost of AD care, inexpensive preliminary screening with a primary-care setting is one of the keys. However, currently available imaging diagnostic technologies, such as expensive PET imaging, are nearly prohibitive for this need. Clearly, fast, cheap, and reliable methods for preliminary screening of AD patients are urgently needed. Compared to non-invasive imaging such as PET imaging and MRI imaging, biomarker detection in biofluids is a very promising alternative for AD diagnosis. Currently, several methods, including immune- MS, ELISA, SIMOA, have been tested in clinical trials; however, these methods are associated with certain drawbacks. For example, immune-MS is tedious, while SIMOA has low accuracy and ELISA has large variations from different labs. Mounting evidence suggest that the adaptive and innate immune systems play essential roles in AD pathology. However, the exact roles of humoral immunity in AD pathology are still not clear. Accumulation and aggregation of Beta-Amyloid (Aβ) peptides are hallmarks of AD, and the regulation of Aβ levels has been one of the essential aspects for prevention and development of therapeutics. It is not surprising that human immunological repertoire naturally has such a regulatory system to control the Aβ levels. Naturally occurring autoantibodies (nAbs) against Aβ (nAbs-Aβ) are a part of the innate immune system with the functions of controlling the metabolism and clearance of Aβ species in brains and periphery systems. Over the past years, several studies have investigated nAbs-Aβ titers and their correlations with the stages of AD or severity of AD. However, the reported results are contradictory. In this R21 application, we provide a new angle to investigate nAbs-Aβ in human serum in hope of partially solving the inconsistence problem. We previously discovered that antibody-epitope interactions can be tuned to higher or lower affinities by small molecules for Aβ and tau proteins. Particularly, we found that CRANAD-Xs, a series of Aβ imaging probes developed by the PI group, could enhance, or weaken the binding between Aβ and its antibodies. In this application, we speculate that CRANAD-Xs have similar tuning function for Aβ auto-antibodies in serum, and this tuning capacity can be used to differentiate sera from AD patients and healthy controls. Our method is very straightforward, due to no modifications are needed for both the Aβ antigens and CRANAD-Xs.