Multiancestry analysis of the HLA locus in Alzheimer’s and Parkinson’s diseases uncovers a shared adaptive immune response mediated by
HLA-DRB1*04
subtypes
Across multiancestry groups, we analyzed Human Leukocyte Antigen (HLA) associations in over 176,000 individuals with Parkinson’s disease (PD) and Alzheimer’s disease (AD) versus controls. We demonstrate that the two diseases share the same protective association at the HLA locus. HLA-specific fine-mapping showed that hierarchical protective effects of HLA-DRB1 *04 subtypes best accounted for the association, strongest with HLA-DRB1 *04:04 and HLA-DRB1 *04:07, and intermediary with HLA-DRB1 *04:01 and HLA-DRB1 *04:03. The same signal was associated with decreased neurofibrillary tangles in postmortem brains and was associated with reduced tau levels in cerebrospinal fluid and to a lower extent with increased Aβ42. Protective HLA-DRB1 *04 subtypes strongly bound the aggregation-prone tau PHF6 sequence, however only when acetylated at a lysine (K311), a common posttranslational modification central to tau aggregation. An HLA-DRB1 *04-mediated adaptive immune response decreases PD and AD risks, potentially by acting against tau, offering the possibility of therapeutic avenues.
Intermittent Courses of Corticosteroids Also Present a Risk forPneumocystisPneumonia in Non-HIV Patients
Introduction.Pneumocystispneumonia (PCP) is rising in the non-HIV population and associates with higher morbidity and mortality. The aggressive immunosuppressive regimens, as well as the lack of stablished guidelines for chemoprophylaxis, are likely contributors to this increased incidence. Herein, we have explored the underlying conditions, immunosuppressive therapies, and clinical outcomes of PCP in HIV-negative patients.Methods. Retrospective analysis of PCP in HIV-negative patients at Mayo Clinic from 2006–2010. The underlying condition, immunosuppressive therapies, coinfection, and clinical course were determined. PCP diagnosis required symptoms of pneumonia and identification of the organisms by visualization or by a real-time polymerase chain reaction.Results. A total of 128 cases of PCP were identified during the study period. Hematological malignancies were the predisposing condition for 50% of the patients. While 87% had received corticosteroids or other immunosuppressive therapies for >4 weeks prior to the diagnosis, only 7 were receiving PCP prophylaxis. Up to 43% of patients were not on daily steroids. Sixty-seven patients needed Intensive Care Unit (ICU) and 53 received mechanical ventilation. The mortality for those patients requiring ICU was 40%.Conclusions. PCP diagnosis in the HIV-negative population requires a high level of suspicion even if patients are not receiving daily corticosteroids. Mortality remains high despite adequate treatment.