MAPT and Apathy: In a study of persons with HIV infection ages 50 and older, the presence of apathy was not associated with any component of a panel of potential biomarkers, including tumor necrosis factor-alpha, kynurenine, tryptophan, quinolinic acid, brain-derived neurotrophic factor, glial fibrillary acidic protein, neurofilament light chain, and phosphorylated tau at position threonine 181 [73].