Pre-pandemic antibodies screening against SARS-CoV-2 and virus detection among children diagnosed with eruptive fevers

Int J Immunopathol Pharmacol. 2024 Jan-Dec:38:3946320241260633. doi: 10.1177/03946320241260633.

Abstract

Objectives: This study aims to assess the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG antibodies against the spike (S) and nucleocapsid (NP) proteins, as well as neutralizing antibodies against the receptor-binding domain (RBD). Additionally, it aims to detect viral RNA of SARS-CoV-2 in pre-pandemic archival pediatric specimens collected before the announcement of the COVID-19 pandemic spread on March 20th, 2020, in Morocco. The objective is to investigate the existence of pre-pandemic immunity to SARS-CoV-2.

Methods: We conducted a cross-sectional study, to analyze IgG antibody levels in a cohort of 106 pre-pandemic pediatric participants. Using an indirect enzyme-linked immunosorbent assay (ELISA), we measured the IgG levels against the S and NP proteins of SARS-CoV-2. Additionally, we staged a competitive ELISA assay to evaluate the neutralizing capability of these antibodies. We used reverse transcription polymerase chain reaction (rRT-PCR) to detect viral NP and ORF1ab genes of SARS-CoV-2 in oropharyngeal swabs. Moreover, we conducted on the same specimens a multiplexed RT-PCR to detect RNA of the most common 27 pathogens involved in lower respiratory tract infections.

Results: Among the 106 serum samples, 13% (nn = =14) tested positive for SARS-CoV-2 IgG antibodies using ELISA. Temporal analysis indicated varying IgG positivity levels across 2019. Neutralizing antibodies were found in 21% of the 28 samples analyzed, including two with high inhibition rates (93%). The SARS-CoV-2 RNA was detected using rRT-PCR in 14 samples. None of the samples tested positive for the other 27 pathogens associated with lower respiratory tract infections, using multiplexed RT-PCR.

Conclusion: Our study addresses the possibility, that COVID-19 infections occurred in Morocco before the recognized outbreak. On the other hand, some of the cases might reflect cross-reactivity with other coronaviruses or be influenced by previous viral exposures or vaccinations. Understanding these factors is crucial to comprehending pediatric immune responses to newly emerging infectious diseases.

Keywords: IgG; SARS-CoV-2; cross-reactive immunity; high-affinity antibodies; human-coronaviruses; humoral immunity; neutralizing antibodies.

MeSH terms

  • Adolescent
  • Antibodies, Neutralizing / blood
  • Antibodies, Neutralizing / immunology
  • Antibodies, Viral* / blood
  • COVID-19* / diagnosis
  • COVID-19* / epidemiology
  • COVID-19* / immunology
  • Child
  • Child, Preschool
  • Coronavirus Nucleocapsid Proteins / immunology
  • Cross-Sectional Studies
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Fever / diagnosis
  • Fever / immunology
  • Fever / virology
  • Humans
  • Immunoglobulin G* / blood
  • Immunoglobulin G* / immunology
  • Male
  • Morocco / epidemiology
  • Phosphoproteins
  • RNA, Viral / blood
  • SARS-CoV-2* / immunology
  • Seroepidemiologic Studies
  • Spike Glycoprotein, Coronavirus / immunology

Substances

  • Antibodies, Viral
  • Immunoglobulin G
  • Antibodies, Neutralizing
  • Spike Glycoprotein, Coronavirus
  • Coronavirus Nucleocapsid Proteins
  • RNA, Viral
  • nucleocapsid phosphoprotein, SARS-CoV-2
  • spike protein, SARS-CoV-2
  • Phosphoproteins