CD4 and IL-2 mediated NK cell responses after COVID-19 infection and mRNA vaccination in adults

Assessment of the BNT162B2 COVID-19 vaccine immune response in Brazilian indigenous adolescents

BACKGROUND

COVID-19 vaccination of minors is crucial for global pandemic control, especially among indigenous populations, who are often more vulnerable due to limited healthcare resources and communal living settings.

OBJECTIVES

To assess the immunogenicity responses of the BNT162b2 vaccine in immunized Brazilian indigenous adolescents.

METHODS

A cohort study was conducted with indigenous adolescents aged 12 to 18 years residing in the largest peri-urban indigenous region in Brazil. SARS-CoV-2-specific immune responses were analyzed before (D1) and after (D2) completion of the vaccination schedule. Demographic data were collected using a questionnaire.

RESULTS

Of the 129 adolescents invited, 98 (75.96 %) participated in the study. Most were of Guarani ethnicity, single, had lower incomes, and were educated only to the elementary level. Post-vaccination, a statistically significant increase was noted in IgG concentration (24.03 % to 37.02 %). Increases were observed in B lymphocytes (11.88 to 13.92 cells/mm3), memory B cells (13.58 to 15.96 cells/mm3), NK cells (20.23 to 24.08 cells/mm3), and non-classical monocytes (9.23 to 11.34 cells/mm3), while CD8+ T cells decreased (24.41 to 21.69 cells/mm3). Adolescents with prior exposure to the virus showed increased levels of B lymphocytes and CD8+ T cells. No significant changes were observed in other cell subpopulations from exposure to the virus.

CONCLUSION

Elevated levels of antibodies and certain cell subpopulations were observed in vaccinated adolescents, confirming the effectiveness of the BNT162b2 vaccine in maintaining humoral and cellular responses. This study is the first to describe data from indigenous minors vaccinated against COVID-19 with the BNT162b2 vaccine, highlighting the importance of vaccination efforts and the potential need for booster doses.

Long-term dynamics of natural killer cells in response to SARS-CoV-2 vaccination: Persistently enhanced activity postvaccination

Natural Killer (NK) cells play a significant role in the early defense against virus infections and cancer. Recent studies have demonstrated the involvement of NK cells in both the induction and effector phases of vaccine-induced immunity in various contexts. However, their role in shaping immune responses following SARS-CoV-2 vaccination remains poorly understood. To address this matter, we conducted a comprehensive analysis of NK cell phenotype and function in SARS-CoV-2 unexposed individuals who received the BNT162b2 vaccine. We employed a longitudinal study design and utilized a panel of 53 15-mer overlapping peptides covering the receptor binding domain (RBD) of the SARS-CoV-2 Spike protein to assess NK cell function at 0 and 20 days following the first vaccine, and 30 and 240 days following booster. Additionally, we evaluated the levels of total IgG anti-Spike antibodies and their potential neutralizing ability. Our findings revealed an increased NK cell activity upon re-exposure to RBD when combined with IL12 and IL18 several months after booster. Concurrently, we observed that the frequencies of NKG2A + NK cells declined over the course of the follow-up period, while NKG2C increased only in CMV positive subjects. The finding that NK cell functions are inducible 9 months after vaccination upon re-exposure to RBD and cytokines, sheds light on the role of NK cells in contributing to SARS-CoV-2 vaccine-induced immune protection and pave the way to further studies in the field.

Comparing population-level humoral and cellular immunity to SARS-Cov-2 in Bangalore, India

Two types of immunity, humoral and cellular, offer protection against COVID. Humoral protection, contributed by circulating neutralizing antibodies, can provide immediate protection but decays more quickly than cellular immunity and can lose effectiveness in the face of mutation and drift in the SARS-CoV-2 spike protein. Therefore, population-level seroprevalence surveys used to estimate population-level immunity may underestimate the degree to which a population is protected against COVID. In early 2021, before India began its vaccination campaign, we tested for humoral and cellular immunity to SARS-Cov-2 in representative samples of slum and non-slum populations in Bangalore, India. We found that 29.7% of samples (unweighted) had IgG antibodies to the spike protein and 15.5% had neutralizing antibodies, but at up to 46% showed evidence of cellular immunity. We also find that prevalence of cellular immunity is significantly higher in slums than in non-slums. These findings suggest (1) that a significantly larger proportion of the population in Bangalore, India, had cellular immunity to SARS-CoV-2 than had humoral immunity, as measured by serological surveys, and (2) that low socio-economic status communities display higher frequency of cellular immunity, likely because of greater exposure to infection due to population density.