Describing immune responses to SARS-CoV-2 in natural infection and among vaccine Recipients in Uganda

Abstract

Background: Describing T and B cell immune responses to SARS-COV-2 among naturally infected and vaccinated individuals is of at most importance in developing vaccines that will lead to COVID-19 disease resolution. Here we compare T cell responses from both the vaccinated and naturally infected people when re-stimulated with both spike and Nucleocapsid peptide. We also compare antibody responses from those whose samples were taken before COVID-19 (Pre-Cov), from those that were infected with COVID-19 and those that received AstraZeneca vaccine. Objective: To describe antibody and T-cell immune responses to SARS-CoV-2 among naturally infected and vaccinated individuals Methods: A study looking at B and T-cell responses among adults above 18 years naturally infected and those vaccinated with SARS-CoV-2. It was conducted at the Immunology Laboratory of MakCHS. We used stored serum and PBMC samples. A total of 12 PBMCs which consisted of 3 samples from mildly infected COVID-19 patients and 9 samples from vaccinated participants analyzed using flow cytometry. We also evaluated antibody titers from 32 pre-covid participants, 52 naturally infected patients and 64 vaccinated ARUA study participants. Data was analyzed using Flowjo software for flow cytometry Comparisons and graphs were made using Graph Prism 9.4.1 for both PBMC and ELISA software. The Mann Whitney U T test for non-parametric variables was used for comparisons. A significant difference was used with p values <0.05 Results: There was a significant expression of TNFa (p=0.0182), HLA-DR+, CD38+ (p=0.0091), CD107a (p=0.0091), ICOS (p=0.0091) PD-1 (p=0.0091) IL-17F (p=0.0227) Mann Whitney T test. We also observed significant production of IgG antibodies from those that were vaccinated and naturally infected compared to those that had provided samples before COVID-19 disease era. Conclusion: In this context, for a greater expression of the IL-2, the vaccinated participants would need to receive a booster dose of the vaccine to enhance the efficiency of the Immune system. A significant expression of IL-10 and PD-1 in the vaccinated individuals is suggestive of an ongoing inflammatory responses and maybe a predictor of a better outcome from sustainably activating the adaptive immune system against COVID-19 infection in vaccination individuals. Significant expression of HLA-DR+, CD38+ on both CD4+ and CD8+ in vaccinated participants was associated with robust T cell response suggestive of a better outcome in resolution of COVID-19 disease. Presumably a longer gap between the first priming vaccine doses to the next booster dose is thought to have an impact on how the effector and memory T cells are reactivated and how rapidly and robustly they respond.