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Topics in Antiviral Medicine ; 29(1):53-54, 2021.
Article in English | EMBASE | ID: covidwho-1250660


Background: Further knowledge on adaptive immunity to SARS-CoV-2 (CoV-2) in children is needed in order to define possible immunization strategies and reconsider pandemic control measures. We analyzed anti-CoV-2 antibodies (Ab) and their neutralizing activity (PRNT), alongside antigen (Ag) specific cellular response, in relation to virus load in nasopharyngeal swabs. Methods: We analysed 42 CoV-2 patients at 7 days after symptoms onset. CoV-2 viral load (VL) was measured by RT-PCR and digital droplet PCR on longitudinal samples of nasopharyngeal swabs (NP). Virus infectivity (FFU) was tested by virus focus forming assay. CoV-2 antibodies were investigated by Diasorin (CoV-2 Ab) and neutralization assay (PRNT). CoV-2-specific CD4-CD40L+ T-cells and Spike specific B-cells were analysed by flow cytometry. Plasma proteomic profiling was measured by 2 Olink panels. We calculated the area under the curve (AUC) of the viral load from NP collected every 48 hours up to undetectable VL. Mann-Whitney was used to compare means in individuals with neutralizing activity (PRNT+) or not (PRNT-);linear regression was used to evaluate the associations between virus load and infectivity over time. Principal component analysis (PCA) was used to analyse proteomic data. Results: Higher VL was found in seronegative patients expressed in terms of both CoV-2 Ab (p=0.003) and PRNT (p=0.0007). Similarly, lower FFU was associated with higher CoV-2 Ab (p=0.003;rho=-0.67) and PRNT (p=0.023;rho=-0.46). Further, the AUC of the viral load in NP showed an inverse correlation with CoV-2 Ab (p=0.031;rho=-0.54). Development of humoral response was associated with the presence of CoV-2 specific IgD-CD27+ B cells, with a higher frequency of CoV-2 specific B cells found in seropositive compared to seronegative (p=0.001). Besides, individuals developing neutralizing Ab had higher frequency CD4-CD40L+ T-cells compared to PRNT- (p=0.03). The plasma proteome confirmed the association between cellular and humoral CoV-2 immunity, with PRNT+ showing higher viral signal transduction molecules (SLAMF1, CD244, CLEC4G). Conclusion: This work provides a virological and immunological characterization of SARS-CoV-2 infected children presenting a differential Abmediated neutralizing activity. It demonstrates that children with neutralizing antibodies present reduced viral load, faster virus clearance and lower in vitro infectivity. These data provide information that can drive vaccination endpoints and quarantine measures policies.

Biochimica Clinica ; 44(SUPPL 2):S103, 2020.
Article in English | EMBASE | ID: covidwho-984242


Severe acute respiratory syndrome coronavirus 2 (SARSCoV-2) is the etiological agent of Coronavirus Disease 2019 (COVID-19), rapidly spread in the current pandemic. The diagnosis of Covid 19 is based on the detection of viral RNA by molecular amplification (NAAT) in nasopharingeal swabs and virus-specific antibodies of different isotypes in the serum. IgM and IgG anti-Sars CoV-2 appear 4-7 days after the onset of symptoms but the highest level of IgM and IgG are detected after 2-3 weeks and 3-6 weeks, respectively. Serological assays are useful for the diagnosis and for epidemiological studies. To compare different methods, we measured serum antibody levels with three automated assays including Elecsys®Roche anti-SarsCov2, Abbott Sars-CoV-2 IgG and Diasorin Liason®SARS-CoV-2 S1/S2 IgG in a goup of 50 selected subjects (negative or positive for nasopharingeal swab, initial screening with Abbott serological test or previuos clinical suspect of COVID-19). A good concordance of the results (68%) was found between Roche and Diasorin assays, and between Roche and Abbott tests while the concordance between Abbott and Diasorin is lower (38%). The samples were also analyzed with other 2 non automated assays: Euroimmun Sars-CoV-2 ELISA (IgG) and Euroimmun Sars-CoV-2 ELISA (IgA). The percentage of positivity is 58% with Diasorin Liason®SARS-CoV-2 S1/S2 IgG, 42% for Abbott Sars-CoV-2 IgG, 32% for Euroimmun Sars-CoV-2 ELISA (IgA), 30% for Euroimmun Sars-CoV-2 ELISA (IgG) and 28% for Elecsys® Roche anti-SarsCov2. The concordance of ~88% and 86% was revealed between Roche test and Euroimmun (IgG), and between Roche and Euroimmun (IgA), respectively, while it reduced to 66% among Diasorin and Euroimmun (IgG) and 62% between Abbott and Euroimmune (IgG).The results in agreement with all five tests were the 34% of total selected cases. The percentage of positive specimens tested with Roche method confirmed with at least 2 other assays was 100%;this value was 93% for Euroimmun (IgG), 81% for Euroimmun (IgA), 52% for Diasorin assay and 47% for Abbott test.