To Örebro University

mRNA vaccines are likely to become widely used for the prevention of infectious diseases in the future. Nevertheless, a notable gap exists in mechanistic data, particularly concerning the potential effects of sequential mRNA immunization or preexisting immunity on the early innate immune response triggered by vaccination. In this study, healthy adults, with or without documented prior SARS-CoV-2 infection, were vaccinated with the BNT162b2/Comirnaty mRNA vaccine. Prior infection conferred significantly stronger induction of proinflammatory and type I IFN-related gene signatures, serum cytokines, and monocyte expansion after the prime vaccination. The response to the second vaccination further increased the magnitude of the early innate response in both study groups. The third vaccination did not further increase vaccine-induced inflammation. In vitro stimulation of PBMCs with TLR ligands showed no difference in cytokine responses between groups, or before or after prime vaccination, indicating absence of a trained immunity effect. We observed that levels of preexisting antigen-specific CD4 T cells, antibody, and memory B cells correlated with elements of the early innate response to the first vaccination. Our data thereby indicate that preexisting memory formed by infection may augment the innate immune activation induced by mRNA vaccines.

Background and Aims: Peripheral arterial disease (PAD) is a clinical manifestation of atherosclerosis, affecting arteries in the leg. Based on their symptoms and severity, PAD patients are characterized into three sub-groups: asymptomatic, intermittent claudication (IC) and critical limb ischemia (CLI). Despite its high prevalence, PAD remains under diagnosed and the role of immune cells in PAD pathophysiology remains poorly understood. In this study, we characterized the innate immune responses in PAD patients compared to healthy controls.

Methods: Blood samples were collected from 14 patients with PAD (IC) and 30 healthy controls, to assess the phenotype of monocytes and neutrophils by using 10-colour flow cytometry. Phagocytosis assay was performed with labelled E.coli particles. Mann-Whitney U non-parametrical test was used for statistical comparison between PAD patients and healthy controls.

Results: A significant higher proportion of leukocytes (p<0.05) and neutrophils (p<0.01) was observed in PAD patients compared to healthy controls, whereas monocyte subsets showed no significant differences. Interestingly, neutrophils showed a significantly impaired phagocytosis capability (p<0.05) and reduced expression of myeloperoxidase (MPO) (p<0.05) in PAD patients compared to healthy controls.

Conclusions: Taken together these results, suggest that PAD patients have an increased proportion of neutrophils in circulation, with impaired phagocytosis capability, compared to healthy controls.

Background and Aims: Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis, affecting the lower limbs. T cells are among the principal contributors to the development of atherosclerotic plaques. However, T cell immune responses in PAD pathophysiology are poorly understood and a detailed phenotypic and functional characterization of T cell immune responses in PAD is needed.

Methods: Blood samples were collected from PAD patients with claudicatio intermittens (n=14) and healthy controls (HCs, n=30). We assessed the phenotype of active, effector and memory T cell subsets by evaluating the expression of specific surface and intracellular markers analysed by 10-colour flow cytometry. Functional responses were evaluated by performing T cell receptor (TCR) stimulation of PBMCs in a 3D cell culture system to assess cytokine production by ELISA. Statistical analyses were performed using the Mann-Whitney U test.

Results: No differences were observed between PAD and HCs in terms of active, effector and memory T cell phenotypes and in the frequency of cells expressing CCR6 and CXCR3 (markers associated with T cells producing IL-17 and IFN-γ). However, lower frequencies of IFN-γ+ cells among CD8+ (P=0.04), and CD4+CD8+ cells (P=0.03) were observed in PAD compared to HCs. TNF-α production in PAD-derived PBMCs, via TCR stimulation was increased at both 48- (P=0.004) and 72-hour time points (P=0.003). No differences were observed in IL-1β, IFN-γ and IL-17 secretion.

Conclusions: Taken together these results suggest that increased TNF-α secretion by PBMCs in response to TCR activation might contribute to the pro-inflammatory environment in PAD pathogenesis.