Lancet Infect Dis. from 46 laboratory\confirmed coronavirus disease\2019 (COVID\19) PK68 subjects. Secondly, 85 unfavorable serum samples collected before the SARS\CoV\2 pandemic were analyzed. Thirdly, possible correlations between antibody levels and the producing neutralizing activity against a clinical isolate of SARS\CoV\2 were evaluated. PK68 Results Rabbit Polyclonal to OR10C1 revealed that both assessments are endowed with low PK68 sensitivity on the day of hospital admission, which increased to 97.8% and 100% for samples collected after 15 days for DiaSorin and Roche assessments, respectively. The specificity evaluated for the two tests ranges from 96.5% to 100%, respectively.?Importantly, a poor direct correlation between antibody titers and neutralizing activity levels was evidenced in the present study. These data further shed light on both potentials and possible limitations related to SARS\CoV\2 serology. In this context, great efforts are still necessary for investigating antibody kinetics to develop novel diagnostic algorithms. Moreover, further investigations around the role of neutralizing antibodies and their correlate of protection will be of paramount importance for the development of effective vaccines. strong class=”kwd-title” Keywords: COVID\19 diagnostic assays, neutralizing activity, SARS\CoV\2 serology AbbreviationsAUCarea under the curveCIconfidence intervalCOIcutoff indexCPEcytopathic effectDMEMDulbecco’s altered Eagle’s mediumECLIAelectrochemiluminescence immunoassayEDAEndpoint Dilutions AssayFBSfetal bovine serumICUintensive care unitMOImultiplicity of infectionNnucleocapsidNEAAnon\essential amino acidsP/Spenicillin/streptomycinPFUplaque forming unitPRAplaque reduction assaySspikeSEstandard errorTCID50 median tissue culture infectious dose 1.?BACKGROUND Tracking the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS\CoV\2) positive subjects certainly represents an urgent epidemiological need for facing coronavirus disease\2019 (COVID\19) pandemic waves worldwide. Additionally, commercially available serological assays are of pivotal importance from a diagnostic point of view, especially in those subjects with a clinical picture suggestive for COVID\19 but lacking a molecular\based confirmation of SARS\CoV\2 contamination. 1 To date, several studies have characterized the kinetics of SARS\CoV\2\elicited antibodies evidencing immunoglobulin M (IgM) within 5 days from symptoms onset for and IgG within approximatively 7 days, 2 , 3 , 4 , 5 but the persistence of the humoral immunity towards SARS\CoV\2 seems to be poor. 6 , 7 A plethora of serologic assessments are invading the market, and some of them have been evaluated. 8 However, other assays deserve further analyses as?there is no consensus so far on antigens utilized for the antibody testing nor for the antibody isotype to be detected. These last aspects can be of pivotal importance for evaluating antibody response to candidate vaccines, for selecting plasmas for clinical trials, and for?dissecting unknown immunological aspects related to seroconversion. Indeed, according to WHO, as of 24th September 2020, no correlations between seroconversion, neutralizing activity, and immunity have been made. 9 In the present study, we evaluated the performances of two commercial serology assessments, the LIAISON? SARS\CoV\2 S1/S2 PK68 IgG by DiaSorin and Elecsys Anti\SARS\CoV\2 cobas? by Roche, on 46 COVID\19 patients and 85 sera collected before the current pandemic. Data PK68 obtained from both commercial assays were then compared to the neutralizing activity of each serum against a clinical isolate of SARS\CoV\2, a clinical isolate from a patient admitted to San Raffaele Hospital, Milan (Italy) during the early COVID\19 pandemic in Lombardy. 2.?MATERIALS AND METHODS 2.1. Clinical samples The study was examined and approved by San Raffaele Hospital IRB in the COVID\19 Biobanking project COVID\BioB N CE: 34/int/2020 19/March/2020 ClinicalTrials.gov Identifier: “type”:”clinical-trial”,”attrs”:”text”:”NCT04318366″,”term_id”:”NCT04318366″NCT04318366. Forty\six serum samples were randomly collected from laboratory\confirmed symptomatic COVID\19 patients on their admission to the hospital (T0) and 15 days later (T15). Eighty\five pre\pandemic serum samples, spanning from 2012 to 2018, were also tested for the presence of anti\SARS\CoV\2 antibodies. 2.2. Immunoassays Elecsys Anti\SARS\CoV\2 cobas? by Roche and LIAISON? SARS\CoV\2 S1/S2 IgG assay by DiaSorin were used for detecting anti\SARS\CoV\2 antibodies in all serum samples. Analyses were performed according to the manufacturer’s instructions by using cobas? and LIAISON? XL Analyzer platforms. In brief, Elecsys by Roche uses a recombinant SARS\CoV\2 nucleocapsid (N) antigen. The electrochemiluminescence immunoassay (ECLIA) can detect the presence of IgG, IgM, and IgA antibodies realizing the N protein. 10 According to the producer, samples positive for anti\SARS\CoV\2 antibodies show a cutoff index (COI) equal to or greater than 1. All samples with a COI? ?1.0 are considered negative for the presence of SARS\CoV\2 antibodies. The SARS\CoV\2.