Evidence suggests that innate and adaptive cellular responses mediate resistance to the influenza virus and confer protection after vaccination. However, few studies have resolved the contribution of cellular responses within the context of preexisting antibody titers. Here, we measured the peripheral immune profiles of 206 vaccinated or unvaccinated adults to determine how baseline variations in the cellular and humoral immune compartments contribute independently or synergistically to the risk of developing symptomatic influenza. Protection correlated with diverse and polyfunctional CD4+ and CD8+ T, circulating T follicular helper, T helper type 17, myeloid dendritic and CD16+ natural killer (NK) cell subsets. Conversely, increased susceptibility was predominantly attributed to nonspecific inflammatory populations, including γδ T cells and activated CD16- NK cells, as well as TNFα+ single-cytokine-producing CD8+ T cells. Multivariate and predictive modeling indicated that cellular subsets (1) work synergistically with humoral immunity to confer protection, (2) improve model performance over demographic and serologic factors alone and (3) comprise the most important predictive covariates. Together, these results demonstrate that preinfection peripheral cell composition improves the prediction of symptomatic influenza susceptibility over vaccination, demographics or serology alone.
© 2023. The Author(s), under exclusive licence to Springer Nature America, Inc.

The characterization of B. pertussis (Bp) antigen-specific CD4+ T cell cytokine responses should be included in the evaluation of immunogenicity of pertussis vaccines but is often hindered by the lack of standardized robust assays.
To overcome this limitation, we developed a two-step assay comprising a short-term stimulation of fresh whole blood with Bp antigens and cryopreservation of the stimulated cells, followed later on by batch-wise intracellular cytokine analysis by flow cytometry. Blood samples collected from recently acellular (aP) vaccine boosted subjects with a whole-cell- or aP-primed background was incubated for 24 hrs with Pertussis toxin, Filamentous hemagglutinin or a Bp lysate (400µl per stimulation). Antigen-specific IFN-γ-, IL-4/IL-5/IL-13-, IL-17A/IL-17F- and/or IL-22-producing CD4+ T cells were quantified by flow cytometry to reveal Th1, Th2, and Th17-type responses, respectively. The frequencies of IFN-γ-producing CD8+ T cells were also analyzed.
We demonstrate high reproducibility of the Bp-specific whole blood intracellular staining assay. The results obtained after cryopreservation of the stimulated and fixed cells were very well correlated to those obtained without cryopreservation, an approach used in our previously published assay. Optimization resulted in high sensitivity thanks to very low non-specific backgrounds, with reliable detection of Bp antigen-specific Th1, Th2 and Th17-type CD4+ T cells, in the lowest range frequency of 0.01-0.03%. Bp antigen-specific IFN-γ+ CD8+ T lymphocytes were also detected. This test is easy to perform, analyse and interpret with the establishment of strict criteria defining Bp antigen responses.
Thus, this assay appears as a promising test for evaluation of Bp antigen-specific CD4+ T cells induced by current and next generation pertussis vaccines.
Copyright © 2023 Corbière, Lambert, Rodesch, van Gaans-van den Brink, Misiak, Simonetti, Van Praet, Godefroid, Diavatopoulos, van Els, Mascart and PERISCOPE WP5 Task 7 working group.

Influenza viruses remain a leading cause of global respiratory illness in humans. The suboptimal effectiveness of seasonal influenza vaccination underscores the need for a more comprehensive understanding of immune mediators of protection, especially in populations with diverse baseline immune profiles and exposure histories. While anti-influenza antibody titers are typically used to define correlates of protection, mounting evidence suggests a substantive role for innate and cellular immunity in determining tolerance and resistance during influenza virus infection. However, distinct cell subsets that correlate with protection against symptomatic influenza remain to be identified in humans. Here, we measured baseline cellular and serologic profiles in peripheral blood from 206 vaccinated or unvaccinated adult subjects enrolled in the 2018 SHIVERS-II cohort to determine how baseline variations in the cellular and humoral immune compartments contribute independently or synergistically to the risk of developing symptomatic influenza infection. Protection from symptomatic influenza correlated with increased individual frequencies of diverse and polyfunctional CD4 and CD8 T cells, cells associated with engagement of humoral responses including cTfh and mDCs, Th17 cells, and innate effector CD16-expressing cytotoxic and cytokine-producing NK cells. In contrast, increased susceptibility was predominantly attributed to nonspecific inflammatory populations including γδ T cells and activated CD16 neg NK cells, as well as TNFα + single-producing CD8 T cells. A trained random forest model categorizing symptomatic influenza cases identified that cellular covariates substantially improved model accuracy up to 86% over demographic and serologic factors alone (61%). A corresponding variable importance analysis showed cellular populations comprise 28 of the top 30 covariates (from 48 total), with the single most important factor being ICOS + cTfh cells. Lastly, using a multivariate logistic regression model considering participant demographics, anti-influenza antibody titers, vaccination status, and cell population covariates, we quantified how these factors contribute to risk of symptomatic influenza infection. Protection was associated with a combination of lymphocyte populations including naïve, CD107a + , and Th17 CD4 T cells, and serologic factors including antibodies targeting neuraminidase. Increased risk of symptomatic influenza (95% subtype A) was associated with elevated anti-hemagglutinin antibodies against influenza B (Yamagata), along with γδ T cells and TNFα + CD8 T cell single-cytokine producers. Together, these results demonstrate that the composition of pre-infection peripheral cell profiles is a stronger predictor of symptomatic influenza susceptibility than vaccination, demographics, or serology.

SARS-CoV-2 mRNA vaccines induce robust anti-spike (S) antibody and CD4+ T cell responses. It is not yet clear whether vaccine-induced follicular helper CD4+ T (TFH) cell responses contribute to this outstanding immunogenicity. Using fine-needle aspiration of draining axillary lymph nodes from individuals who received the BNT162b2 mRNA vaccine, we evaluated the T cell receptor sequences and phenotype of lymph node TFH. Mining of the responding TFH T cell receptor repertoire revealed a strikingly immunodominant HLA-DPB1∗04-restricted response to S167-180 in individuals with this allele, which is among the most common HLA alleles in humans. Paired blood and lymph node specimens show that while circulating S-specific TFH cells peak one week after the second immunization, S-specific TFH persist at nearly constant frequencies for at least six months. Collectively, our results underscore the key role that robust TFH cell responses play in establishing long-term immunity by this efficacious human vaccine.
Copyright © 2021 Elsevier Inc. All rights reserved.

The host immunity of patients with adenovirus pneumonia in different severity of illness is unclear. This study compared the routine laboratory tests and the host immunity of human adenovirus (HAdV) patients with different severity of illness. A co-cultured cell model in vitro was established to verify the T cell response in vitro. Among 140 patients with confirmed HAdV of varying severity, the number of lymphocytes in the severe patients was significantly reduced to 1.91 × 109/L compared with the healthy control (3.92 × 109/L) and the mild patients (4.27 × 109/L). The levels of IL-6, IL-10, and IFN-γ in patients with adenovirus pneumonia were significantly elevated with the severity of the disease. Compared with the healthy control (20.82%) and the stable patients (33.96%), the percentage of CD8+ T cells that produced IFN-γ increased to 56.27% in the progressing patients. Adenovirus infection increased the percentage of CD8+ T and CD4+ T cells that produce IFN-γ in the co-culture system. The hyperfunction of IFN-γ+ CD8+ T cells might be related to the severity of adenovirus infection. The in vitro co-culture cell model could also provide a usable cellular model for subsequent experiments.