A fast and cost-effective method for apolipoprotein E isotyping as an alternative to APOE genotyping for patient screening and stratification

Abstract

Apolipoprotein E (apoE) is a 34 kDa glycoprotein involved in lipid metabolism. The human APOE gene encodes for three different apoE protein isoforms: E2, E3 and E4. The interest in apoE isoforms is high for epidemiological research, patient stratification and identification of those at increased risk for clinical trials and prevention. The isoform apoE4 is associated with increased risk for coronary heart and Alzheimer’s diseases. This paper describes a method for specifically detecting the apoE4 isoform from biological fluids by taking advantage of the capacity of apoE to bind “specifically” to polystyrene surfaces as capture and a specific anti-apoE4 monoclonal antibody as reporter. Our results indicate that the apoE-polystyrene binding interaction is highly stable, resistant to detergents and acid and basic washes. The methodology here described is accurate, easily implementable, fast and cost-effective. Although at present, our technique is unable to discriminate homozygous APOE ε4/ε4 from APOE ε3/ε4 and ε2/ε4 heterozygous, it opens new avenues for the development of inexpensive, yet effective, tests for the detection of apoE4 for patients’ stratification. Preliminary results indicated that this methodology is also adaptable into turbidimetric platforms, which make it a good candidate for clinical implementation through its translation to the clinical analysis routine.

Disclosing genetic risk for Alzheimer's dementia to individuals with mild cognitive impairment

“…The design of these trials provide access to APOE genotyping results to their participants. In addition, some healthy individuals have obtained genetic risk information about AD through studies of precision medicine, physicians, or direct‐to‐consumer options 13,41,42 . Most notably, 23andMe has FDA approval to include APOE results in their direct‐to‐consumer personal genome service 43 .…”

ABCA1- and ABCG1-mediated cholesterol efflux capacity of cerebrospinal fluid is impaired in Alzheimer's disease

“…The minimum detectable concentration is 4 ng/ml and 8 ng/ml for total apoE and apoE4, respectively. Because apoE4 production is discrete and not continuous according to the null, heterozygous, or homozygous genotype, the apoE4/total apoE ratio could be used to identify the apo4 genotype (26,27). Based on this concept we stratified subjects in apo4 carriers when the apoE4/apoE ratio was >0 (26,28).…”

Evaluation of a semi-automatic isoelectric focusing method for apolipoprotein E phenotyping

“…Nevertheless, in opposition with mass spectrometry that is able to detect all isoforms with a high specificity, ELISA techniques are specific for apoE4, thus not allowing a complete apoE phenotyping [7]. A recent method based on apoE-polystyrene interaction has been described, but it is again specific for apoE4 detection and does not distinguish between homozygote E4/E4 or heterozygous phenotypes containing E4 isoform [8].…”