This review article focuses on the upstream pertinent pathophysiology leading to neurodegenerative disease. Specifically, the nexus appears to be blood brain barrier (BBB) leakiness resulting in a two-prong inflammatory disease spectrum damaging the microvasculature and corrupted protein synthesis and degradation with accumulating misfolded toxic proteins. The suboptimal results of removing misfolded proteins means a new approach to disease in the preclinical state is required aimed at other targets.Validated noninvasive imaging and serologic biomarkers of early preclinical disease implemented in the high-risk patient cohort along with periodic surveillance once effective treatments are developed will be required.This review discusses the physiology and pathophysiology of the BBB, new MRI imaging techniques identifying the leak and altered fluid dynamic effects in the preclinical state. The risk factors for disease development, preventative measures, and potential treatment targets are also discussed.

Introduction: The objectives of this study were to (1) investigate the association between human blood type and COVID-19 infection in both inpatient and longitudinal populations at our institution in South Florida and (2) identify the association between blood type and severity of COVID-19 infection via presence of cellular biomarkers of severe infection in hospitalized individuals. Methods: This study consists of (1) a single-center retrospective analysis of 669 of 2,741 COVID-19 positive screened patients seen from January 1, 2020 until March 31, 2021 at the University of Miami Emergency Department (ED) who tested positive for COVID-19 infection and had a documented ABO blood type and (2) a longitudinal SARS-CoV-2 immunity study (“CITY”) at the University of Miami Miller School of Medicine consisting of 185 survey participants. COVID-19 outcome rates and 95% confidence intervals were calculated for each ABO blood type and Rh group using Chi-squared tests for categorical and ANOVA for continuous variables in the inpatient cohort and Chi-squared tests for the longitudinal cohort, all executed in R studio. Results: Our inpatient cohort had a mean age of 53.6 (± 17.9) years with 48% males and 52% females. When compared to patients with other blood types, those with O- demonstrated less risk of developing COVID-19 pneumonia (26.7% for O- vs. 69.2% for type A-, 56.5% for A+, 71.4% for AB+, 53.7% for B+, 51.5% for O+, p-value= 0.003 via Chi-squared test) and decreased mortality due to COVID-19 infection (17.0% mortality for O vs. 26.3% for A, 29.2% for B, p-value= 0.012 via Chi-squared test). Blood type O- demonstrated less elevated levels of LDH than did other blood types (p-value= 0.001, ANOVA) and a higher frequency of clinically accepted baseline levels of troponin (0.04 ng/mL) (p-value= 0.026, ANOVA) (Figure 1). Most of the longitudinal cohort was ABO blood grouping type O (47% (87/185)), with 33.5% type A, 14.1% B, and 5.4% AB. Most individuals were Rh positive (85.9%). There was no significant association found between COVID status (infection vs. non-infection) and ABO (Chi-squared test (3, N = 185) = 1.8, p = 0.6) or Rh (Chi-squared test (1, N = 185) = 0.16, p = 0.7) blood typing. Nearly all participants had been vaccinated (95.1% (176/185)), with a majority reporting primary vaccination with Pfizer (57.8% (107/185)), followed by Moderna (33% (61/185)), and Johnson & Johnson (4.3% (8/185)). 8 participants (4.3%) were unvaccinated. Conclusions: In an inpatient setting, blood type O sustained less risk of COVID-19 mortality and O- demonstrated less risk of developing COVID-19 pneumonia. In a longitudinal setting, there was no association found between blood type and COVID-19 severity. As the novelty of COVID-19 infection declines with time, further studies on risk-stratification by blood type are encouraged.