Neutralizing Antibodies in Children with SARS-CoV-2

The adaptive immune system, or acquired immunity, is a strategic immune response mounted by specific antibodies. This response uses immunological memory to enhance the immune response and is activated by exposure to pathogens. Although it tends to be slower than the innate response, it is an important step in the process of eliminating pathogens.

With the COVID-19 pandemic currently underway, it is essential to better understand the adaptive immunity of children in relation to the SARS-CoV-2 virus to define possible vaccination strategies and reconsider control measures during the pandemic.

A recent study conducted by researchers in Italy analyzed anti-SARS-CoV-2 antibodies as well as their neutralizing activity, as well as the specific cellular response of the antigen, in relation to viral loads in nasopharyngeal swabs. The data was presented during the virtual sessions of the Conference on Retroviruses and Opportunistic Infections (CROI) 2021.

The study included 42 participants whose viral loads were measured by RT-PCR and digital droplet PCR tests on longitudinal nasopharyngeal swab samples 7 days after symptom onset. A focus formation assay was used to test for virus infectivity and viral antibodies were investigated by diasorin and neutralization assays.

In addition, CD4, CD40L + T lymphocytes and Spike-specific B lymphocytes were analyzed by flow cytometry. 2 Olink panels were used to measure the proteomic profiling of plasma. The Mann-Whitney, a test used to compare the differences between two independent groups, was used to compare the means in individuals with or without neutralizing activity.

The results of the study showed that higher levels of viral load were found in HIV negative patients expressed in terms of anti-SARS-CoV-2 antibody and neutralizing activity. Lower viral infectivity was also associated with higher anti-SARS-CoV-2 antibodies and neutralizing activity.

Development of the humoral response was associated with the presence of SARS-CoV-2 specific IgD-CD27 + B cells, with a higher frequency of SARS-CoV-2 specific B cells found in seropositive compared to seronegatives.

“This work provides a virological and immunological characterization of children infected with SARS-CoV-2 exhibiting differential Ab-mediated neutralizing activity,” the authors wrote. “This demonstrates that children with neutralizing antibodies have a reduced viral load, faster viral clearance and lower in vitro infectivity. This data provides information that can guide vaccination settings and policies for quarantine measures. “