HDL mimetics protect Alzheimer's patients carrying APOE e4 from SARS-CoV-2 invasion

Patients with Alzheimer's disease (AD) inheriting Apolipoprotein (APOE) e4 are susceptible to COVID-19, but the underlying mechanism of how such a neurodegenerative disease promotes respiratory vulnerability to viral in-fections remains insufficiently understood. The uncovering of genetic basis of COVID-19 outcome holds the potential to establish disease models for therapeutic development. Here, using human iPSC-derived type II alveolar epithelial cells (hAECII) from AD patients with APOE e4 and healthy individuals, we showed that AECII of AD had a greater level of SARS-CoV-2 invasion but not replication, along with increased expressions of viral receptor and co-receptors, while reduced pulmonary surfactant proteins. Since low serum HDL-C levels have been implicated in the onset of both AD and COVID-19, we further revealed that HDL mimetics, including 4 F dimeric peptide and its phospholipid conjugate pHDL, were effective in protecting AECII bearing APOE e4 against SARS-CoV-2 invasion. In AD, concomitant with improved AD pathological phenotypes, HDL mimetics specifically restored the defective basal SP-D, a pulmonary innate immune lipoprotein that targets glycans of the spike protein to neutralize invading viruses. Moreover, HDL mimetics demonstrated strong SP-D-independent virucidal effects, which additionally restricted the entry of coronaviral particles into non-AD AECII models and lungs of human ACE2-transgenic mice in response to Alpha and Omicron variants of SARS-CoV-2. Our work