IgG Immune Complexes Break Immune Tolerance of Human Microglia
JOURNAL OF IMMUNOLOGY
Authors: van der Poel, Marlijn; Hoepel, Willianne; Hamann, Jorg; Huitinga, Inge; den Dunnen, Jeroen
Microglia are phagocytic cells involved in homeostasis of the brain and are key players in the pathogenesis of multiple sclerosis (MS). A hallmark of MS diagnosis is the presence of IgG Abs, which appear as oligoclonal bands in the cerebrospinal fluid. In this study, we demonstrate that myelin obtained post mortem from 8 out of 11 MS brain donors is bound by IgG Abs. Importantly, we show that IgG immune complexes strongly potentiate activation of primary human microglia by breaking their tolerance for microbial stimuli, such as LPS and Poly I:C, resulting in increased production of key proinflammatory cytokines, such as TNF and IL-1 beta. We identified Fc gamma RI and Fc gamma RIIa as the two main responsible IgG receptors for the breaking of immune tolerance of microglia. Combined, these data indicate that IgG immune complexes potentiate inflammation by human microglia, which may play an important role in MS-associated inflammation and the formation of demyelinating lesions.
SARS-CoV-2 antibody prevalence in Brazil: results from two successive nationwide serological household surveys
LANCET GLOBAL HEALTH
Authors: Hallal, Pedro C.; Hartwig, Fernando P.; Horta, Bernardo L.; Silveira, Mariangela F.; Struchiner, Claudio J.; Vidaletti, Luis P.; Neumann, Nelson A.; Pellanda, Lucia C.; Dellagostin, Odir A.; Burattini, Marcelo N.; Victora, Gabriel D.; Menezes, Ana M. B.; Barros, Fernando C.; Barros, Aluisio J. D.; Victora, Cesar G.
Background Population-based data on COVID-19 are essential for guiding policies. There are few such studies, particularly from low or middle-income countries. Brazil is currently a hotspot for COVID-19 globally. We aimed to investigate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody prevalence by city and according to sex, age, ethnicity group, and socioeconomic status, and compare seroprevalence estimates with official statistics on deaths and cases. Methods In this repeated cross-sectional study, we did two seroprevalence surveys in 133 sentinel cities in all Brazilian states. We randomly selected households and randomly selected one individual from all household members. We excluded children younger than 1 year. Presence of antibodies against SARS-CoV-2 was assessed using a lateral flow point-of-care test, the WONDFO SARS-CoV-2 Antibody Test (Wondfo Biotech, Guangzhou, China), using two drops of blood from finger prick samples. This lateral-flow assay detects IgG and IgM isotypes that are specific to the SARS-CoV-2 receptor binding domain of the spike protein. Participants also answered short questionnaires on sociodemographic information (sex, age, education, ethnicity, household size, and household assets) and compliance with physical distancing measures. Findings We included 25 025 participants in the first survey (May 14-21) and 31165 in the second (June 4-7). For the 83 (62%) cities with sample sizes of more than 200 participants in both surveys, the pooled seroprevalence increased from 1.9% (95% CI 1.7-2.1) to 3.1% (2.8-3.4). City-level prevalence ranged from 0% to 25.4% in both surveys. 11(69%) of 16 cities with prevalence above 2.0% in the first survey were located in a stretch along a 2000 km of the Amazon river in the northern region. In the second survey, we found 34 cities with prevalence above 2.0%, which included the same 11 Amazon cities plus 14 from the northeast region, where prevalence was increasing rapidly. Prevalence levels were lower in the south and centre-west, and intermediate in the southeast, where the highest level was found in Rio de Janeiro (7.5% [4.2-12.2]). In the second survey, prevalence was similar in men and women, but an increased prevalence was observed in participants aged 20-59 years and those living in crowded conditions (4.4% [3.5-5.6] for those living with households with six or more people). Prevalence among Indigenous people was 6.4% (4.1-9.4) compared with 1.4% (1.2-1.7) among White people. Prevalence in the poorest socioeconomic quintile was 3.7% (3- 2-4.3) compared with 1.7% (1.4-2-2) in the wealthiest quintile. Interpretation Antibody prevalence was highly heterogeneous by country region, with rapid initial escalation in Brazil's north and northeast. Prevalence is strongly associated with Indigenous ancestry and low socioeconomic status. These population subgroups are unlikely to be protected if the policy response to the pandemic by the national government continues to downplay scientific evidence. Copyright (C) 2020 The Author(s). Published by Elsevier Ltd.