HIV-associated neurocognitive disorder (HAND) and Alzheimer’s disease (AD) are two neurocognitive disorders with overlapping clinical presentations and pathophysiology. The two have been thought to be two separate entities. However, the introduction and widespread use of antiretroviral therapy (ART) has altered the clinical manifestations of HAND, shifting from a pattern of subcortical dementia to one more akin to cortical dementia, resembling AD. Thus, the line between the two disease entities is not clear-cut. In this review, we discuss the concept of Alzheimer’s disease-like dementia (ADLD) in HIV, which describes this phenomenon. While the mechanisms of HIV-associated ADLD remain to be elucidated, potential mechanisms include HIV-specific pathways, including epigenetic imprinting from initial viral infection, persistent and low viral load (which can only be detected by ultra-sensitive PCR), HIV-related inflammation, and putative pathways underlying traditional AD risk factors. Importantly, we have shown that HIV-specific microRNAs (miRs) encapsulated in extracellular vesicles (EV-miRs) play an important role in mediating the detrimental effects in the cardiovascular system. A useful preclinical model to study ADLD would be to expose AD mice to HIV-positive EVs to identify candidate EV-miRs that mediate the HIV-specific effects underlying ADLD. Characterization of the candidate EV-miRs may provide novel therapeutic armamentaria for ADLD.

With the resurgence of measles outbreaks globally it is important to understand how seropositivity induced by measles vaccination wanes over time. We aimed to measure the prevalence of measles seropositivity in vaccinated individuals and assess changes in antibody levels over time since vaccination. We conducted a systematic review and meta-analysis by searching PubMed, Embase, Scopus, Web of Science, and Cochrane Library databases from January 1980 to April 2025 for studies reporting serological outcomes following measles-containing vaccination. The search criteria included clinical trials, cross-sectional studies, cohort studies, and case series with ≥10 participants. The primary outcome was the proportion of vaccinated individuals seropositive for measles IgG antibodies. Meta-regression was performed to assess the relationship between seropositivity and time since vaccination. The study was registered with PROSPERO, CRD420251026672. The search identified 2348 unique records. Following title and abstract screening, 89 articles were selected for full-text review, of which 18 studies were included, encompassing 23,236 vaccinated individuals from 10 countries. Overall pooled proportion of seropositive individuals was 87·8% (95% Confidence Interval [CI] 83·9%–91·2%, I² = 97·9%). Most individuals included in the analysis had received at least two doses of measles-containing vaccine, whereas evidence for single-dose recipients was limited. Single-dose recipients displayed a pooled seropositivity of 84·3% (95% CI, 71·6–93·9; 6 studies) and multi-dose recipients (individuals who received ≥2 doses) exhibited 88·8% (95% CI, 84·4–92·6; 15 studies; p = 0·252 for between-group heterogeneity). Notably, only one study included solely single-dose recipients, highlighting that estimates for this group are based on limited data. The overall seropositivity declined with increased time between vaccination and serological assessment: 92·9% (95% CI, 84·3%–98·4%) within 10 years, 87·0% (95% CI, 70·4%–97·4%) at 11–15 years, 82·8% (95% CI, 67·8%–93·9%) at 16–22 years, and 81·9% (95% CI, 30·8%–100%) at ≥23 years post-vaccination. Meta-regression suggested measles seropositivity declines at a rate of 0·48% per year in vaccinated individuals (β = −0·048, 95% CI, −0·078 to −0·018; p = 0·002). Ten years after measles vaccination, vaccinated individuals displayed high seropositivity. The observed decrease in measles seropositivity in the years after vaccination may indicate waning humoral immunity. However, this systematic review and meta-analysis was unable to assess the relationship between seropositivity and measles infection rates, thus further investigation is needed. No funding was received for the study design, data collection, analysis, interpretation, writing of the manuscript, or the decision to submit for publication.