The following is a summary of “Antibody Avidity Maturation Following Recovery From Infection or the Booster Vaccination Grants Breadth of SARS-CoV-2 Neutralizing Capacity,” published in the March 2023 issue of Infectious Diseases by Nakagama, et al.

It’s crucial to reduce (re-)exposures by using antibodies that can cross-neutralize SARS-CoV-2 variants. For a study, researchers sought to assess SARS-CoV-2 neutralizing potential and the role of antibody maturation—the process by which the selection of higher affinity antibodies augments host immunity.

The study analyzed sera from SARS-CoV-2 convalescents at 2, 6, or 10 months post-recovery, and BNT162b2 vaccine recipients at 3 or 25 weeks post-vaccination. Anti-spike IgG avidity was measured using urea-treated ELISAs. Neutralizing capacity was assessed by surrogate neutralization assays, and the breadth of neutralizing capacity was inferred by the fold change between variant and wild-type neutralization.

Late-convalescent sera’s avidity indices were noticeably greater than those of early-convalescent sera (median, 37.7 [interquartile range 28.4-45.1] vs. 64.9 [57.5-71.5], P< .0001). (Spearman r = 0.49 vs. 0.67 [wild-type]; 0.18-0.52 vs. 0.48-0.83 [variants]) The best anticipated neutralizing capacity was for urea-resistant, high-avidity IgG. Higher-avidity convalescent sera were more effective in neutralizing different SARS-CoV-2 variants (P< .001 for Alpha; P< .01 for Delta and Omicron). Only after receiving the booster dosage did vaccine recipients’ avidities mature meaningfully, and by week 25, they had only a very small amount of cross-neutralizing power.

The maturation of antibody avidity was crucial in determining the cross-neutralizing capacity of antibodies against SARS-CoV-2 variants. Avidity maturation was progressive beyond acute recovery from infection or became apparent after the booster vaccine dose, granting broader anti-SARS-CoV-2 neutralizing capacity. Understanding the maturation kinetics of the two building blocks of anti-SARS-CoV-2 humoral immunity was essential.

Reference: academic.oup.com/jid/article/227/6/780/6955885