Apolipoprotein-Mediated Transcytosis of Vaccine Aluminum Adjuvant Nanoparticles Across the Blood-Brain Barrier: An Uninvestigated Hypothesis

This version substantially revises and extends Version 1.0. The primary hypothesis has been reformulated within a protein corona framework: PS80 is now presented as an efficiency amplifier of a baseline apolipoprotein adsorption mechanism (H0) rather than a prerequisite, broadening the scope of the hypothesis to all aluminum-adjuvanted vaccines. The title has been updated accordingly. New material includes: A dedicated introduction to protein corona dynamics and kinetic competition in Section 2. A two-level hypothesis structure (H1 primary + H0 corollary) in Section 5, with an additional falsifiable prediction (H0a). A new subsection 7.2 on organ-specific distribution via LDLR expression and its relationship to autoimmune disease patterns, including ASIA syndrome (Shoenfeld & Agmon-Levin 2011), Matzinger's danger model, NLRP3 inflammasome activation, and cryptic antigen exposure. Incorporation of Vojdani & Vojdani (2025) on anti-PEG antibody cross-reactivity with human tissue antigens including actin and MOG, with discussion of structural analogy to PS80. Five new references added [16–20]. The core hypothesis, experimental predictions H1a–H1d, clinical vaccine table, and parallel LNP/mRNA hypothesis are unchanged from v1.0. Abstract Background: Several widely used vaccine formulations simultaneously contain aluminum salts as adjuvants andpolysorbate 80 (PS80) as a surfactant. The pharmacological properties of each excipient have been independentlydocumented, yet their potential synergistic interaction — and the broader question of apolipoprotein coronaformation on aluminum adjuvant nanoparticles — have never been experimentally evaluated. Hypothesis: We propose that vaccine aluminum adjuvant nanoparticles reaching the vascular compartment acquire aprotein corona whose composition determines their biological fate. If apolipoprotein E (ApoE) or ApoB are recruitedto the corona surface with the receptor-binding domain exposed, the particle may be recognized by LDL receptors(LDLR) on the cerebrovascular endothelium and transcytosed into the brain parenchyma via the mechanismdescribed by Kreuter et al. Polysorbate 80 (PS80), present as a co-excipient in several aluminum-containingvaccines, is proposed to act not as a prerequisite for this mechanism but as an efficiency amplifier: by increasing theproportion of ApoE in the corona and favoring its receptor-competent orientation, PS80 makes the mechanism moreprobable and reproducible. The underlying pathway may however operate at baseline even in the absence of PS80, inany formulation that allows a fraction of aluminum particles to reach systemic circulation. Evidence base: Three independent lines of research support the biological plausibility of this hypothesis: (1) Kreuteret al. demonstrated that PS80-coated nanoparticles of diverse chemical composition adsorb apolipoproteins in vivo,enabling LDL receptor-mediated endocytosis at the cerebrovascular endothelium; (2) Gherardi et al. demonstratedthat vaccine aluminum particles exhibit long-term biopersistence and can translocate to the brain via intracellularphagocyte-mediated transport; (3) Mold, Umar, King and Exley (2018) reported extraordinary aluminumconcentrations in post-mortem brain tissue from donors with autism spectrum disorder, with aluminum foundpredominantly in microglia-like and non-neuronal inflammatory cells. Implications: If confirmed, this mechanism would represent an additional pathway for aluminum adjuvantneurodeposition. The protein corona framework further explains interindividual variability in neurological adverseevent profiles. A structurally analogous parallel hypothesis is articulated regarding PEGylated lipid nanoparticles inmRNA vaccines. Both hypotheses are falsifiable and amenable to direct experimental testing