T-Cell Mediated Response after Primary and Booster SARS-CoV-2 Messenger RNA Vaccination in Nursing Home Residents

Kinetics of pro- and anti-inflammatory spike-specific cellular immune responses in long-term care facility residents after COVID-19 mRNA primary and booster vaccination: a prospective longitudinal study in Japan

BACKGROUND

The magnitude and durability of cell-mediated immunity in older and severely frail individuals following coronavirus disease 2019 (COVID-19) vaccination remain unclear. A controlled immune response could be the key to preventing severe COVID-19; however, it is uncertain whether vaccination induces an anti-inflammatory cellular immune response. To address these issues, a 48-week-long prospective longitudinal study was conducted. A total of 106 infection-naive participants (57 long-term care facility [LTCF] residents [median age; 89.0 years], 28 outpatients [median age; 72.0 years], and 21 healthcare workers [median age; 51.0 years]) provided peripheral blood mononuclear cell (PBMC) samples for the assessment of spike-specific PBMC responses before primary vaccination, 24 weeks after primary vaccination, and three months after booster vaccination. Cellular immune responses to severe acute respiratory syndrome coronavirus 2 spike protein were examined by measuring interferon (IFN)-γ, tumor necrosis factor (TNF), interleukin (IL)-2, IL-4, IL-6, and IL-10 levels secreted from the spike protein peptide-stimulated PBMCs of participants.

RESULTS

LTCF residents exhibited significantly lower IFN-γ, TNF, IL-2, and IL-6 levels than healthcare workers after the primary vaccination. Booster vaccination increased IL-2 and IL-6 levels in LTCF residents comparable to those in healthcare workers, whereas IFN-γ and TNF levels in LTCF residents remained significantly lower than those in healthcare workers. IL-10 levels were not significantly different from the initial values after primary vaccination but increased significantly after booster vaccination in all subgroups. Multivariate analysis showed that age was negatively associated with IFN-γ, TNF, IL-2, and IL-6 levels but not with IL-10 levels. The levels of pro-inflammatory cytokines, including IFN-γ, TNF, IL-2, and IL-6, were positively correlated with humoral immune responses, whereas IL-10 levels were not.

CONCLUSIONS

Older and severely frail individuals may exhibit diminished spike-specific PBMC responses following COVID-19 vaccination compared to the general population. A single booster vaccination may not adequately enhance cell-mediated immunity in older and severely frail individuals to a level comparable to that in the general population. Furthermore, booster vaccination may induce not only a pro-inflammatory cellular immune response but also an anti-inflammatory cellular immune response, potentially mitigating detrimental hyperinflammation.

Neutralizing antibody levels detected early after mRNA-based vaccination do not predict by themselves subsequent breakthrough infections of SARS-CoV-2

The development of mRNA vaccines represented a significant achievement in response to the global health crisis during the SARS-CoV-2 pandemic. Evaluating vaccine efficacy entails identifying different anti-SARS-CoV-2 antibodies, such as total antibodies against the Receptor Binding Domain (RBD) of the S-protein, or neutralizing antibodies (NAbs). This study utilized an innovative PETIA-based kit to measure NAb, and the investigation aimed to assess whether levels of anti-RBD IgG and NAb uniformly measured 30 days after vaccination could predict individuals at a higher risk of subsequent infection in the months following vaccination. Among a cohort of healthy vaccinated healthcare workers larger than 6,000, 12 mRNA-1273- and 115 BNT162b2-vaccinated individuals contracted infections after the first two doses. The main finding is that neither anti-RBD IgG nor NAb levels measured at day 30 post-vaccination can be used as predictors of breakthrough infections (BI). Therefore, the levels of anti-SARS-CoV-2 antibodies detected shortly after vaccination are not the pivotal factors involved in antiviral protection, and other characteristics must be considered in understanding protection against infection. Furthermore, the levels of anti-RBD and NAbs followed a very similar pattern, with a correlation coefficient of r = 0.96. This robust correlation would justify ceasing the quantification of NAbs, as the information provided by both determinations is highly similar. This optimization would help allocate resources more efficiently and speed up the determination of individuals' humoral immunity status.

When Cell-Mediated Immunity after Vaccination Is Important

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A 12-month follow-up of the immune response to SARS-CoV-2 primary vaccination: evidence from a real-world study

A real-world population-based longitudinal study, aimed at determining the magnitude and duration of immunity induced by different types of vaccines against COVID-19, started in 2021 by enrolling a cohort of 2,497 individuals at time of their first vaccination. The study cohort included both healthy adults aged ≤65 years and elderly subjects aged >65 years with two or more co-morbidities. Here, patterns of anti-SARS-CoV-2 humoral and cell-mediated specific immune response, assessed on 1,182 remaining subjects, at 6 (T6) and 12 months (T12) after the first vaccine dose, are described. At T12 median anti-Spike IgG antibody levels were increased compared to T6. The determinants of increased anti-Spike IgG were the receipt of a third vaccine dose between T6 and T12 and being positive for anti-Nucleocapside IgG at T12, a marker of recent infection, while age had no significant effect. The capacity of T12 sera to neutralize in vitro the ancestral B strain and the Omicron BA.5 variant was assessed in a subgroup of vaccinated subjects. A correlation between anti-S IgG levels and sera neutralizing capacity was identified and higher neutralizing capacity was evident in healthy adults compared to frail elderly subjects and in those who were positive for anti-Nucleocapside IgG at T12. Remarkably, one third of T12 sera from anti-Nucleocapside IgG negative older individuals were unable to neutralize the BA.5 variant strain. Finally, the evaluation of T-cell mediated immunity showed that most analysed subjects, independently from age and comorbidity, displayed Spike-specific responses with a high degree of polyfunctionality, especially in the CD8 compartment. In conclusion, vaccinated subjects had high levels of circulating antibodies against SARS-CoV-2 Spike protein 12 months after the primary vaccination, which increased as compared to T6. The enhancing effect could be attributable to the administration of a third vaccine dose but also to the occurrence of breakthrough infection. Older individuals, especially those who were anti-Nucleocapside IgG negative, displayed an impaired capacity to neutralize the BA.5 variant strain. Spike specific T-cell responses, able to sustain immunity and maintain the ability to fight the infection, were present in most of older and younger subjects assayed at T12.

Specific immune responses after BNT162b2 mRNA vaccination and COVID-19 infection

Although vaccines against COVID-19 are effective tools in preventing severe disease, recent studies have shown enhanced protection after vaccine boosters. The aim of our study was to examine the dynamics and duration of both humoral and cellular immune responses following a three-dose regimen of the BNT162b2 mRNA vaccine. In a longitudinal prospective study we enrolled 86 adults who received the BNT162b2 vaccine, 35 unvaccinated individuals with a history of mild COVID-19 and a control group of 30 healthy SARS-CoV-2 seronegative persons. We assessed the SARS-CoV-2-specific T cell responses and IgG production up to 12 months post the third BNT162b2 dose in 24 subjects. The vaccinated group had significantly higher IgG antibody levels after two doses compared to the convalescent group (p<0.001). After the third dose, IgG levels surged beyond those detected after the second dose (p<0.001). Notably, these elevated IgG levels were maintained 12 months post the third dose. After two doses, specific T cell responses were detected in 87.5% of the vaccinated group. Additionally, there was a significant decrease before the third dose. However, post the third dose, specific T cell responses surged and remained stable up to the 12-month period. Our findings indicate that the BNT162b2 vaccine induces potent and enduring humoral and cellular responses, which are notably enhanced by the third dose and remain persistant without a significant decline a year after the booster. Further research is essential to understand the potential need for subsequent boosters.