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Chronic traumatic encephalopathy (CTE) is a progressive neurodegenerative disease, characterized by hyperphosphorylated tau, found in individuals with a history of exposure to repetitive head impacts. While the neuropathologic hallmark of CTE is found in the cortex, hippocampal tau has proven to be an important neuropathologic feature to examine the extent of disease severity. However, the hippocampus is also heavily affected in many other tauopathies, such as Alzheimer’s disease (AD). How CTE and AD differentially affect the hippocampus is unclear. Using immunofluorescent analysis, a detailed histologic characterization of 3R and 4R tau isoforms and their differential accumulation in the temporal cortex in CTE and AD was performed. CTE and AD were both observed to contain mixed 3R and 4R tau isoforms, with 4R predominating in mild disease and 3R increasing proportionally as pathological severity increased. CTE demonstrated high levels of tau in hippocampal subfields CA2 and CA3 compared to CA1. There were also low levels of tau in the subiculum compared to CA1 in CTE. In contrast, AD had higher levels of tau in CA1 and subiculum compared to CA2/3. Direct comparison of the tau burden between AD and CTE demonstrated that CTE had higher tau densities in CA4 and CA2/3, while AD had elevated tau in the subiculum. Amyloid beta pathology did not contribute to tau isoform levels. Finally, it was demonstrated that higher levels of 3R tau correlated to more severe extracellular tau (ghost tangles) pathology. These findings suggest that mixed 3R/4R tauopathies begin as 4R predominant then transition to 3R predominant as pathological severity increases and ghost tangles develop. Overall, this work demonstrates that the relative deposition of tau isoforms among hippocampal subfields can aid in differential diagnosis of AD and CTE, and might help improve specificity of biomarkers for in vivo diagnosis.

Neurodegeneration is a seminal feature of many neurological disorders. Chronic traumatic encephalopathy (CTE) is caused by repetitive head impacts (RHI) and is characterized by sulcal tau pathology. However, quantitative assessments of regional neurodegeneration in CTE have not been described. In this study, we quantified three key neurodegenerative measures, including cortical thickness, neuronal density, and synaptic proteins, in contact sport athletes ( n  = 185) and non-athlete controls ( n  = 52) within the sulcal depth, middle, and gyral crest of the dorsolateral frontal cortex. Cortical thickness and neuronal density were decreased within the sulcus in CTE compared to controls ( p ’s < 0.05). Measurements of synaptic proteins within the gyral crest showed a reduction of α-synuclein with CTE stage ( p  = 0.002) and variable changes in PSD-95 density. After adjusting for age, multiple linear regression models demonstrated a strong association between the duration of contact sports play and cortical thinning ( p  = 0.001) and neuronal loss ( p  = 0.032) within the sulcus. Additional regression models, adjusted for tau pathology, suggest that within the sulcus, the duration of play was associated with neuronal loss predominantly through tau pathology. In contrast, the association of duration of play with cortical thinning was minimally impacted by tau pathology. Overall, CTE is associated with cortical atrophy and a predominant sulcal neurodegeneration. Furthermore, the duration of contact sports play is associated with measures of neurodegeneration that are more severe in the cortical sulcus and may occur through tau-dependent and independent mechanisms.

Abstract Background We investigated whether dolutegravir (DTG) monotherapy could be used to maintain virological suppression in people living with human immunodeficiency virus (HIV) on a successful dolutegravir-based triple therapy. Methods MONCAY (MONotherapy of TiviCAY) was a 48-week, multicentric, randomized, open-label, 12% noninferiority margin trial. Patients with CD4 nadir >100/μL, plasma HIV-1 RNA <50 copies/mL for ≥12 months, and stable regimen with DTG/abacavir (ABC)/lamivudine (3TC) were 1:1 randomized to continue their regimen or to DTG monotherapy. The primary endpoint was the proportion of patients with HIV RNA <50 copies/mL at week 24 in intention-to-treat snapshot analysis. Virologic failure (VF) was defined as 2 consecutive HIV RNA >50 copies/mL within 2 weeks apart. Results Seventy-eight patients were assigned to DTG monotherapy and 80 to continue DTG/ABC/3TC. By week 24, 2 patients in the DTG group experienced VF without resistance to the integrase strand transfer inhibitor (INSTI) class; 1 patient discontinued DTG/ABC/3TC due to an adverse event. The success rate at week 24 was 73/78 (93.6%) in the DTG arm and 77/80 (96.3%) in the DTG/ABC/3TC arm (difference, 2.7%; 95% confidence interval [CI], –5.0 to 10.8). During subsequent follow-up, 5 additional VFs occurred in the DTG arm (2 of which harbored emerging resistance mutation to INSTI). The cumulative incidence of VF at week 48 was 9.7% (95% CI, 2.8 to 16.6) in the DTG arm compared with 0% in the DTG/ABC/3TC arm (P = .005 by the log-rank test). The Data Safety Monitoring Board recommended to reintensify the DTG arm with standardized triple therapy. Conclusions Because the risk of VF with resistance increases over time, we recommend avoiding DTG monotherapy as a maintenance strategy among people living with chronic HIV infection. Clinical Trials Registration NCT02596334 and EudraCT 2015-002853-36. In a randomized, noninferiority trial, dolutegravir monotherapy was not a valid option to maintain virological suppression over week 24 in people living with chronic human immunodeficiency virus infection on a successful dolutegravir/abacavir/lamivudine regimen and favored emergence of integrase strand transfer inhibitor resistance.