Temporal trends and differences of SARS-CoV-2-specific antibody responses in symptomatic and asymptomatic subjects: a longitudinal study from Umbria in Italy

  1. Iosief Abraha
  2. Paolo Eusebi
  3. Antonella Germani
  4. Erica Pasquarelli
  5. Sofia Pascolini
  6. Rossana Antonietti
  7. Sandro Argenti
  8. Alessandra Fioravanti
  9. Elisa Martini
  10. Luana Aristei
  11. Paola Mancinelli
  12. Maria Letizia Ottaviani
  13. Martina Roselli
  14. Milena Barzacca
  15. Erika Belardinelli
  16. Marta Micheli

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Abstract

Dynamics of antibody responses following SARS-CoV-2 infection are controversial in terms of immunity and persistence. We aimed to assess longitudinally the trend of antibody serological titres, their correlation with clinical severity as well as clinical reinfection during a follow-up.

Design

Longitudinal cohort, 12 months follow-up study.

Setting

USL Umbria 2.

Participants

Consecutive subjects aged 15–75 who were discharged with the diagnosis of Sars-Cov-2 from the hospitals of the AUSL Umbria 2, or resulted positive to a PCR test for SARS-CoV-2 infection with or without symptoms were recruited. SARS-CoV-2 serological testing for antibodies targeting the Nucleocapside and Spike proteins were determined.

Results

Of 184 eligible subjects, 149 were available for evaluation: 17 were classified as oligo/asymptomatic, 107 as symptomatic, 25 as hospital admitted. Participants differed in terms of signs and symptoms as well as treatment. Overall there was a significant difference in terms of antibody titres between groups (anti-S: p<0.00; anti-N: p=0.019). Median anti-S titres in the symptomatic and hospital admitted participants were significantly higher compared with the oligo/asymptomatic participants. During follow-up, the median titre of anti-S antibodies did not show significant variations (p=0.500) and the difference within groups remained constant overtime. Subjects that showed an anti-S titre above the threshold of 12 U/mL were 88.7% at first visit and 88.2% at last follow-up. Anti-N values were higher in the hospital admitted participants compared with the other two groups. Anti-N titre reduced constantly overtime (p<0.001) and across the three groups of participants. The percentage of the subjects with serological titre above threshold (<1.4 U/mL) decreased from 74.5%% to 29.2% (p<0.001). None of the participants developed clinically evident reinfection.

Conclusion

Anti-N and anti-S correlate well with clinical severity. While anti-N declines overtime, anti-S antibodies persist for at least 1 year.

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  1. Version published to 10.1136/bmjopen-2021-056370
  2. ScreenIT

    SciScore for 10.1101/2021.08.09.21261450: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIRB: This study was approved by the Regional Research Ethics Committee (Comitato Etico Regionale –
    Consent: Umbria, CER 3695/20), and written informed consent was obtained.
    Sex as a biological variablenot detected.
    Randomizationnot detected.
    Blindingnot detected.
    Power Analysisnot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Laboratory methods: Serum samples were analyzed using two commercial serologic assays: Abbott SARS-CoV-2 IgG, DiaSorin Liaison SARS-CoV-2 S1/S2 IgG.
    Abbott
    suggested: (Abbott, RRID:SCR_010477)
    The analysis of the normal distribution of the sample was evaluated using the Kolmogorov - Smirnov test using STATA software, with the significance level at P <0.05.
    STATA
    suggested: (Stata, RRID:SCR_012763)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    Strength and limitation: Strength of our study include follow-up that lasted for at least one year across from the first pandemic from, the use of both types of serological assays for the understanding of antibody characteristics. We acknowledge some limitations of our study. First, our study does not have a baseline serologic testing since it was conceived in late April and it was not possible to obtain serologic testing when participants had the disease. The time from disease onset and the first clinical and serologic testing was 3 to 6 months. We believe that this could not have biased our results, however, we are unsure whether those that resulted negative at the first visit – who predominately were oligo/asymptomatic participants – could have positive result on the first visit. Second, the study lacks clinical and serological information regarding those who died during the pandemic event, hence we are unable to conclude whether quantitative serologic testing could predict survival. Conclusion: Beside determining the diagnosis of current and past infection, one of the major role of serological testing is to determine the immunization status with which it is possible to predict immunity from future infection. The use of SARS-CoV-2 serological tests requires understanding of how these tests perform in populations over time. Immunologic response from Sars-Cov-2 infection is characterized by both anti N and anti-S antibodies. While anti-N antibodies can be useful for diagnosi...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.

    About SciScore

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  3. Version published to 10.1101/2021.08.09.21261450v1 on medRxiv