Protective Immunity of COVID-19 Vaccination with ChAdOx1 nCoV-19 Following Previous SARS-CoV-2 Infection: A Humoral and Cellular Investigation

Abstract

Infections caused by SARS-CoV-2 induce a severe acute respiratory syndrome called COVID-19 and have led to more than six million deaths worldwide. Vaccination is the most effective preventative measure, and cellular and humoral immunity is crucial to developing individual protection. Here, we aim to investigate hybrid immunity against SARS-CoV-2 triggered by the ChAadOx1 nCoV-19 vaccine in a Brazilian cohort. We investigated the immune response from ChAadOx1 nCoV-19 vaccination in naïve (noCOVID-19) and previously infected individuals (COVID-19) by analyzing levels of D-dimers, total IgG, neutralizing antibodies (Nabs), IFN-γ (interferon-γ) secretion, and immunophenotyping of memory lymphocytes. No significant differences in D-dimer levels were observed 7 or 15 days after vaccination (DAV). All vaccinated individuals presented higher levels of total IgG or Nabs with a positive correlation (R = 0.88). Individuals in the COVID-19 group showed higher levels of antibody and memory B cells, with a faster antibody response starting at 7 DAV compared to noCOVID-19 at 15 DAV. Further, ChAadOx1 nCoV-19 vaccination led to enhanced IFN-γ production (15 DAV) and an increase in activated T CD4+ naïve cells in noCOVID-19 individuals in contrast with COVID-19 individuals. Hence, our data support that hybrid immunity triggered by ChAadOx1 nCoV-19 vaccination is associated with enhanced humoral response, together with a balanced cellular response.

Long-Term Dynamic Changes in Hybrid Immunity over Six Months after Inactivated and Adenoviral Vector Vaccination in Individuals with Previous SARS-CoV-2 Infection

“…Despite individuals who were previously infected and received two doses of CoronaVac showing a slower decline compared to ChAdOx1, their binding antibody levels and neutralizing activities remained at a low titer six months after vaccination [ 36 ]. Conversely, a single dose of ChAdOx1 exhibited robust antibody and neutralizing activity that was consistent with those reported in previous studies [ 14 , 37 ], while a second dose did not clearly enhance the immune response in individuals with prior infection. Similar results were found in mRNA vaccination, indicating that immunization with a single dose significantly boosted the expansion of pre-existing memory B cells in individuals with prior infection, while minimal changes in antibody response was observed after a second dose [ 11 ].…”

“…However, existing evidence has largely focused on the early response following mRNA vaccination among previously infected individuals [ 10 , 11 , 12 , 13 ]. Few studies have evaluated the impacts of inactivated and vector-based vaccines [ 14 , 15 , 16 ]. Additionally, most investigations have focused on short-term immunogenicity, while long-term evaluations remain limited.…”

Cellular Immunity of SARS-CoV-2 in the Borriana COVID-19 Cohort: A Nested Case–Control Study

“…Furthermore, De Marcos and co-authors [ 37 ] found no difference in cellular immune response to the Omicron variant in a cohort of naïve or SARS-CoV-2–infected vaccinated health workers. In Brazil, Azamor and co-authors [ 68 ] found that 120 days after the second dose of ChAadOx1 nCoV-19, the percentages of CD4+ and CD8+ T cells were higher in a non-infected SARS-CoV-2 group compared with an infected SARS-CoV-2 group. Our results of cellular immune responses in the naïve group and the SARS-CoV-2 patients follow this thread.…”

Inactivated and Immunogenic SARS-CoV-2 for Safe Use in Immunoassays and as an Immunization Control for Non-Clinical Trials

“…Previously inactivated (56 °C, 30 min) serum samples were serially diluted in culture medium from 1:6 to 1:1458 (3-fold dilution factor), and PRNT 50 was performed in Vero CCL-81 cells (density 200,000 cells/well) cultivated in 24-well plates using the Wuhan strain. The results were expressed in reciprocal serum dilution [ 32 ]. PRNT 50 titers less than 1:10 were considered negative for NAb presence, and the upper limit of quantification of positive samples was 1:1458.…”