Strong cell-mediated immunity with a weak antibody response confirmed in children after SARS-CoV-2 omicron infection

In a recent study posted on bioRxiv* Preprint server, researchers evaluated antibody response and cell-mediated immunity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) omicron infection in children.

Infection rates associated with the SARS-CoV-2 omicron mutant are consistently high in all age groups. The seroprevalence of SARS-CoV-2 in children increased significantly from 40% to 82% after the advent of Omicron. Therefore, extensive research is needed to understand the extent of the immune response elicited by Omicron infection in the young population.

About research

In this study, researchers investigated the immune response of cells and antibodies induced after SARS-CoV-2 omicron variant infection in children aged 6 to 14 years, and obtained the results from previous coronavirus disease. Compared with 2019 (COVID-19) infection and vaccination status.

The team evaluated the ability to neutralize sera from individuals who reported spontaneous infection with the SARS-CoV-2 mutant, which was predominant before Omicron. SARS-CoV-2 wild-type and antibody-binding ability to the Omicron spike (S) and receptor-binding domain (RBD) regions is a serum collected from 54 children aged 5 to 15 years infected with the preomicron mutant. Estimated from a serological sample. .. These estimates were compared to those of 30 adult participants and unvaccinated adults and children.

The team also recruited 43 unvaccinated children with positive SARS-CoV-2 results obtained during the wave of Omicron infection. The antibody response after primary or secondary infection was measured. The primary infection was a case of Omicron as the first COVID-19 exposure, and the secondary infection was a case of a previous pre-Omicron mutant infection. In addition, the team determined serological responses after primary and secondary infections among the children.

Functional humoral immunity was also presumed PseudovirusA base neutralization assay performed after primary and secondary Omicron infections. In addition, the team recruited 32 children aged 6 to 14 years who were vaccinated with the BNT162b2 COVID-19 vaccine. This includes 10 double-vaccinated and 22 single-vaccinated children.

result

The results of the study showed that the relative antibody-binding activity against SARS-CoV-2 Omicron S and RBD was significantly reduced in children and adults compared to wild-type strains. Relative binding was reduced by 85% in children and 88% in adults, but only 41% showed a positive RBD response. This indicates that the recognition of Omicron by antibodies in serum after pre-Omicron infection was significantly reduced in children and adults.

The team noted that primary Omicron infection elicited low levels of antibody response against Pleomicrons and Omicron variants. Antibody titers were significantly higher against the SARS-CoV-2 delta mutant in one of the children tested. On the other hand, secondary Omicron infection stimulated a strong antibody response against all Pleomicron mutants, showing an 8-fold increase against wild-type RBD and a 10-fold increase against Omicron RBD. However, the reduction in Omicron-specific titers compared to previous variants was consistent despite Omicron infection.

Primary Omicron infection was also found to elicit equivalent and low levels of antibody response against Pleomicrons and Omicron variants. In particular, the titer of Pleomicron was 22% of that observed in the historic group of patients with Preomicron. However, secondary Omicron infection increased the antibody response elicited against all viral mutants. Nucleocapsid-specific reactions were relatively lower after primary Omicron infection than after secondary infection.

In addition, weak neutralizing activity was induced by primary Omicron infection, but only 53% of infected children showed detectable neutralizing titers despite previous infections. On the other hand, strong neutralization was observed after secondary infection with a measurable neutralization titer.

Double vaccination elicited a strong antibody response against SARS-CoV-2S and RBD associated with all SARS-CoV-2 mutants. Only one vaccination was given and some variation was observed between children reflecting previous infections. Responses to Omicron S were reduced by 74% and RBD was reduced by 79% compared to responses to wild type. In addition, the observed S-specific antibody levels were 7.3-fold higher after single vaccination against wild-type and 19-fold higher after double vaccination than after spontaneous infection before Omicron. In addition, omicron-specific antibody response did not increase after infection, 71% lower than in wild-type strains.

In particular, Pleomicron and Omicron-specific antibody titers Spike protein Significantly increased after vaccination, indicating the effect of hybrid immunity. Relative omicron-specific titers were also found to be consistent after the use of wild-type S immunogens. This suggested that the primary omicron infection stimulated the humoral immune response for a strong response to vaccination, while maintaining a relatively comparable perception of the omicron mutant.

Overall, the study results showed that primary SARS-CoV-2 omicron infection elicited moderate antibody response and inadequate neutralizing activity. Researchers believe that the COVID-19 vaccine has shown strong immunogenicity in children, but the effectiveness of the vaccine is influenced by the history of infection with Omicron or pre-Omicron variants.

*Important Notices

bioRxiv publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information.