Affinity and Subtypes Analysis of the Anti-Nucleocapsid Antibodies in SARS-CoV-2 Vaccinated and Non-Vaccinated Individuals

The COVID-19 pandemic has underscored the critical need to understand immune responses arising from both natural infection and vaccination. This study examines the affinity and subclass distribution of anti-nucleocapsid (anti-N) antibodies in 60 participants, comprising 30 vaccinated and 30 non-vaccinated individuals. Using enzyme-linked immunosorbent assays (ELISA), we quantified total IgG (tIgG) and its subclasses (IgG1, IgG2, IgG3, and IgG4) in serum samples. Antibody affinity was assessed using ammonium thiocyanate to evaluate the strength of antigen-antibody interactions. We observed significantly elevated levels of tIgG and its subclasses in the vaccinated participants compared to the non-vaccinated controls, indicating a more robust immune response post-vaccination. In vaccinated individuals, the mean levels of tIgG, IgG1, IgG2, IgG3, and IgG4 were 2.59, 1.02, 0.055, 0.061, and 0.095 (OD), respectively, while non-vaccinated individuals showed lower mean levels at 0.512, 0.11, 0.052, 0.051, and 0.048 (OD) for tIgG, IgG1, IgG2, IgG3, and IgG4, respectively. This notable difference suggests that vaccination promotes not only higher production of these antibody subclasses but also, as shown by the corresponding affinity tests, an increased binding strength of anti-N antibodies. These results indicate that vaccination induces a more robust and higher-quality immune response, contributing to improved immune protection against SARS-CoV-2. The study highlights the critical role of anti-N antibodies in vaccine efficacy and long-term immunity. Our findings offer valuable insights into immune dynamics, informing future vaccine development and strategies for pandemic control, potentially leading to better management of emerging variants and more effective public health interventions.