In a recent study published in Microorganisms, researchers compared the generation of B-cell-mediated antibody responses and T-cell-mediated cellular responses among patients vaccinated with BNT162b messenger ribonucleic acid (mRNA) and patients with mild coronavirus disease 2019 (COVID-19).
Study: The BNT162b mRNA vaccine elicited higher CD4 + antibody and T cell responses than patients with mild COVID-19. Image credit: Numstocker / Shutterstock
Fund
Immunization against the causative agent of COVID-19, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can occur through vaccination or natural infections. The BNT162b2 mRNA vaccine was approved for use after being shown to be safe and 95% effective in preventing COVID-19.
Studies have reported the development of serological immunity after double BNT162b2 vaccinations; however, no comparative assessment of long-term B lymphocyte and T lymphocyte-mediated immune responses induced by natural COVID-19 infections and BNT162b2 vaccination beyond three months has been performed.
About the study
In the present study, the researchers compared B-cell-mediated antibody responses and T-cell-mediated cellular responses between BNT162b mRNA vaccines and mild patients with COVID-19.
A total of 37 convalescent COVID-19 patients included patients with pneumonia (n = 15) and patients with mild symptoms of COVID-19 (n = 22) diagnosed with SARS-CoV-2 nasal test and enrolled in the study from March to December 2020. In addition, vaccinated BNT162b (n = 20) who were health workers enrolled in the study from December 2020 to January 2021.
Serum samples from 15 and 8 convalescent patients with COVID-19 with pneumonia were evaluated at an early stage (59 days after SARS-CoV-2 infection) and at a later time (212 days after SARS infection). -CoV-2). Similarly, convalescents 11 and 11 of COVID-19 with mild symptoms of COVID-19 were analyzed at an early time (48 days after SARS-CoV-2 infection) and at a later time (after 193 days of COVID-19), respectively.
Blood samples were also obtained from 20 vaccinated BNT162b (with no previous history of COVID-19) at an early and late time (three weeks after the second vaccination and six months after the second vaccination), respectively. In addition, 10 samples were obtained after three weeks of booster vaccination.
Peripheral mononuclear blood cells (PMBCs) were isolated from blood samples for the evaluation of S-specific T lymphocyte proliferative responses and the production of type 1 T (TH1) and / or TH2 cytokines. To assess B lymphocyte immune responses, immunoglobulin G (IgG) levels against SARS-CoV-2 (S) ear protein and neutralizing antibody (Nt Ab) titers were assessed for all participants.
To assess T lymphocyte responses, proliferative levels of differentiation 4 (CD4 +) and CD8 + were assessed. Statistical analysis was performed using GraphPad Prism 6 and statistical tests such as the Wilcoxon signed range test and the Friedman test for paired data comparisons. The Mann – Whitney U test and the Kruskal – Wallis test were used for unpaired data comparisons.
Results
Anti-S IgG levels and Nt Ab titers were higher among those vaccinated with BNT162b and patients with pneumonia compared with those with mild COVID-19 patients and remained high among patients with pneumonia, while that titers were reduced among those vaccinated with BNT162b. However, the initial antibody titers were restored using the booster dose of BNT162b.
Similarly, the proliferative responses of CD4 + T lymphocytes among those vaccinated with BNT162b and patients with pneumonia were similar, but were lower among patients with mild COVID-19. However, unlike antibody titers, CD4 + responses remained high in both BNT162b vaccine and post-COVID patients.
Proliferative responses of CD8 + T lymphocytes were lower among those vaccinated with BNT162b than patients with pneumonia, decreased after six months of BNT162b vaccination and did not reach baseline levels after booster vaccination. The cytokine profile among BNT162b vaccinated and post-COVID-19 patients showed mainly TH1 cells such as interferon gamma (IFN-γ), tumor necrosis factor alpha (TNFα), interleukin-2 ( IL-2), the inflammatory protein of macrophages. MIP) -1α, 1β). The production of TH2 cytokines (IL-4.5) was negligible between both groups.
Higher antibody titers and CD4 + T cell responses were observed among BNT162b2 vaccines compared to those observed in mild patients with COVID-19. Antibody titers decreased six months after vaccination and required a booster vaccine to reach baseline levels, and the proliferative responses of CD4 + T lymphocytes remained high over time.
Conclusion
Overall, the results of the study showed that BNT162b vaccinations and severe SARS-CoV-2 infections induced greater serological responses than mild COVID-19; however, the initial immune responses induced by natural and severe SARS-CoV-2 infections lasted longer compared to BNT162b vaccinations. However, the initial antibody titers were restored after booster vaccinations.