On rechallenge 1 year later, 11 of 14 volunteers had reinfection, although only 1 1 had symptoms. detectable response (IgG index value 1). Most (= 1323, 60%) had responses in July with index values classified as high (IgG 10); 1003 (76%) remained within this stratum. Adjusted median index values declined slowly but continuously (July vs. December values were 21 vs. 13; < 0.001). The trajectory of the response did not vary by Cinnamaldehyde age group, sex, race/ethnicity, or diabetes status. Patients without an assay detectable response (= 137) were more likely to be White and in the younger (18 to 44 years) or older (80 years) age groups and less likely to have diabetes and hypoalbuminemia. Limitation: Lack of data on symptoms or reverse transcriptase polymerase chain reaction diagnosis, cohort of persons who survived infection, and use of a semiquantitative assay. Conclusion: Despite impaired immunity, most seropositive patients receiving dialysis maintained RBD antibody levels over 6 months. A slow and continual decline in median antibody levels over time was seen, but no indication that subgroups with impaired immunity had a shorter-lived humoral response was found. Primary Cinnamaldehyde Funding Source: Ascend Clinical Laboratories. Recent studies have begun to delineate breadth and duration of the adaptive immune response to SARS-CoV-2 infection (1C6). Among the antibodies to a set of SARS-CoV-2 antigensnucleocapsid, receptor-binding domain (RBD) of the spike protein, and S2 domain of the spike proteinIgG responses to the spike protein antigens are among the most durable (3, 5, 6). Studies have also correlated Rabbit Polyclonal to RAB6C titers of RBD IgG with the ability to neutralize SARS-CoV-2 (5, 7, 8). Longitudinal studies tracking response to SARS-CoV-2 infection to date have been limited by modest sample sizes (<200) (9, 10), with 1 exception from a homogeneous population from Iceland (6). Early reports emphasized relatively rapid decline or complete disappearance of detectable antibody levels among patients with known infection (1, 4). On the other hand, Wajnberg and colleagues (5) reported high-level and persistent responses for up to 5 months after infection. Although this study included a cross-sectional assessment of 30?082 persons, longitudinal responses were followed among 121 volunteers. In the larger study from Iceland, 1263 persons with SARS-CoV-2 infection were followed for more than 4 months; the authors concluded that antiviral antibodies plateaued after Cinnamaldehyde an initial peak near month 2 (6). These studies, and others (2, 3), have been confined to healthy populations or have not separately examined response among subgroups known to have blunted or shortened adaptive immune responses. In July 2020, we did a survey of a large nationwide sample of patients receiving dialysis in the United States. We showed that patients receiving dialysis can serve as a sentinel population for SARS-CoV-2 seroepidemiology because they are broadly representative of susceptible groups, including older persons, persons of color, and persons with substantial comorbidity (11). Moreover, they have blood drawn monthly, facilitating follow-up testing for antibody responses. Here, we present 6 months of longitudinal data on the evolution of RBD antibodies in the patients receiving dialysis who were seropositive (= 2215) in July. Using a semiquantitative commercially available assay, we Cinnamaldehyde examine the persistence of antibodies stratified by antibody response level, age group, sex, race/ethnicity, and diabetes status. We also report the characteristics of persons whose antibody response persistently remains below the detectable assay range. Methods In July 2020, we tested remainder plasma from 28?503 patients receiving hemodialysis for the presence of total RBD antibody. The patients tested were from 1200 dialysis facilities throughout the United States. Our sampling strategy and testing methods are described in detail elsewhere (11). The mean age, sex, geographic region, and race/ethnicity distribution of our sampled patients matched that of the overall U.S. dialysis population. Assay Characteristics The initial antibody test done in July, the Siemens total RBD immunoglobulin assay, measures IgG and IgM antibodies and has a manufacturer-reported sensitivity of 100% and specificity of 99.8% (12). To assess serologic.