Antibody Avidity Maturation Following Booster Vaccination with an Intranasal Adenovirus Salnavac Vaccine

The COVID-19 pandemic has led to the rapid development of new vaccines and methods of testing vaccine-induced immunity. Despite the extensive research that has been conducted on the level of specific antibodies, less attention has been paid to studying the avidity of these antibodies. The avidity of serum antibodies is associated with a vaccine showing high effectiveness and reflects the process of affinity maturation. In the context of vaccines against SARS-CoV-2, only a limited number of studies have investigated the avidity of antibodies, often solely focusing on the wild-type virus following vaccination. This study provides new insights into the avidity of serum antibodies following adenovirus-based boosters. We focused on the effects of an intranasal Salnavac booster, which is compared, using a single analytical platform, to an intramuscular Sputnik V.

The avidity of RBD-specific IgGs and IgAs was investigated through ELISA using urea and biolayer interferometry.

The results demonstrated the similar avidities of serum antibodies, which were induced by both vaccines for six months post-booster. However, an increase in antibody avidity was observed for the wild-type and Delta variants, but not for the BA.4/5 variant.

Collectively, our data provide the insights into antibody avidity maturation after the adenovirus-based vaccines against SARS-CoV-2.