Immunosenescence is a process of remodeling the immune system under the influence of chronic inflammation during aging. Parkinson’s disease (PD) is a common age-associated neurodegenerative disorder and is frequently accompanied by neuroinflammation. On the other hand, cytomegalovirus (CMV), one of the most spread infections in humans, may induce chronic inflammation which contributes to immunosenescence, differentiation and the inflation of T cells and NK cells. Currently, there is no clear understanding of immunosenescence severity in PD patients infected with CMV. In this study, we analyzed differentiation stages and immunosenescence characteristics of T cells and NK cells in 31 patients with mild and moderate PD severity, 33 age-matched and 30 young healthy donors. The PD patients were 100% CMV-seropositive compared to 76% age-matched and 73% young CMV-infected healthy donors. The proportion of effector memory T cells re-expressing CD45RA, CD57+CD56− T cells and CD57+CD56+ T cells was significantly reduced in PD patients compared with CMV-seropositive age-matched healthy individuals. The CD57+CD56− T cell proportion in PD patients was similar to that of CMV-seropositive young healthy donors. Thus, PD is characterized by reduced peripheral blood T cell immunosenescence, even against the background of CMV infection.

Coronavirus disease 2019 (COVID-19), caused by the SARS-CoV-2 virus, is accompanied by a dysregulated immune response. In particular, NK cells, involved in the antiviral response, are affected by the infection. This study aimed to investigate circulating NK cells with a focus on their activation, depletion, changes in the surface expression of key receptors, and functional activity during COVID-19, among intensive care unit (ICU) patients, moderately ill patients, and convalescents (CCP). Our data confirmed that NK cell activation in patients with COVID-19 is accompanied by changes in circulating cytokines. The progression of COVID-19 was associated with a coordinated decrease in the proportion of NKG2D+ and CD16+ NK cells, and an increase in PD-1, which indicated their exhaustion. A higher content of NKG2D+ NK cells distinguished surviving patients from non-survivors in the ICU group. NK cell exhaustion in ICU patients was additionally confirmed by a strong negative correlation of PD-1 and natural cytotoxicity levels. In moderately ill patients and convalescents, correlations were found between the levels of CD57, NKG2C, and NKp30, which may indicate the formation of adaptive NK cells. A reduced NKp30 level was observed in patients with a lethal outcome. Altogether, the phenotypic changes in circulating NK cells of COVID-19 patients suggest that the intense activation of NK cells during SARS-CoV-2 infection, most likely induced by cytokines, is accompanied by NK cell exhaustion, the extent of which may be critical for the disease outcome.

Parkinson disease (PD) is attributed to a proteostasis disorder mediated by α-synuclein accumulating in a specific brain region. PD manifestation is often related to extraneuronal alterations, some of which could be used as diagnostic or prognostic PD biomarkers. In this work, we studied the shifts in the expression of proteostasis-associated chaperones of the HSP70 family and autophagy-dependent p62 protein values in the peripheral blood mononuclear cells (PBMC) of mild to moderate PD patients. Although we did not detect any changes in the intracellular HSP70 protein pool in PD patients compared to non-PD controls, an increase in the transcriptional activity of the stress-associated HSPA1A/B and HSPA6 genes was observed in these cells. Basal p62 content was found to be increased in PD patients’ PBMC, similarly to the p62 level in substantia nigra neural cells in PD. Moreover, the spontaneous apoptosis level was increased among PBMC and positively correlated with the p62 intracellular level in the PD group. A combined HSPA6- and p62-based analysis among 26 PD patients and 36 age-matched non-PD controls pointed out the diagnostic significance of these markers, with intermediate sensitivity and high specificity of this combination when observing patients diagnosed with PD.

BACKGROUND: COVID-19 mediates activation of immunocompetent cells. Little is known about the phenotypic marker CD38 on the surface of T and NK cells and its association with the severity of COVID-19. AIM: To analyze the distribution of the surface marker CD38 in subsets of T and NK cells at the different stages of their differentiation in the groups of patients with COVID-19 and convalescents, and to reveal the relationship between the level of CD38 expression in subpopulations of T and NK cells with the severity of COVID-19. MATERIALS AND METHODS: Peripheral blood mononuclear cells (PBMC) from patients and donors were isolated using ficoll density gradient followed by cytofluorimetric analysis of the surface markers: CD3, CD56, CD38. RESULTS: In PBMC samples the level of CD38 expression on NK cells (CD3CD56+), including CD56bright and CD56dim subsets, as well as on T lymphocytes, differentiating conventional CD56(CD3+CD56) and NKT-like (CD3+CD56+) cells, were analyzed. Among CD56 T cells and NKT-like cells the highest levels of CD38 expression were registered in the groups of patients of moderate severity and convalescents, and, in contrast, the decreased CD38 levels were detected in the group of patients from the intensive care unit. CONCLUSIONS: The findings suggest that the level of CD38+ T cell in COVID-19 may be of use as diagnostic value.

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BACKGROUND: Daily, people inhale airborne viral particles, some of which have a size of about 100 nm, such as particles of SARS-CoV-2. Kinetics of such 100 nm particle distribution in the respiratory tract is important, however, not a properly investigated question. AIM: To estimate the dissemination of inert viral particles based on the analysis of the spatial distribution of fluorescent 100 nm particles in the mouse lungs at different time points after the application. MATHERIALS AND METHODS: Fluorescent particles of 100 nm size were applied to C57BL/6 mice. 6, 24, 48 and 72 hours after, lungs were excised and fixed. Lung lobes were stained with immunohistochemistry as whole-mounts and then underwent optical clearance. Three-dimensional images of whole-mount mouse lung lobes were acquired using confocal laser scanning microscopy. RESULTS: 6 hours after the particle application particles were detected in lungs both as single particles and as particle agglomerates. Particles were both free and internalized by phagocytic cells. 24 hours after the application particles were detected both in bronchial lumen and in the alveolar space. Particles were detected in the mouse lungs up to 72 hours after the application. CONCLUSIONS: Reaching the respiratory tract of mammalian, inert particles which size equal to SARS-CoV-2 particle size distribute both in bronchi and in alveoli and undergoes internalization of phagocytic cells.

SARS-CoV-2-induced infection is still dangerous. Mouse models are convenient to the investigation of virus-activated immune response mechanisms. However, mice are not proper model organisms to study COVID-19 due to decreased interaction affinity between the SARS-CoV-2 receptor-binding domain (RBD) and mouse angiotensin-converting enzyme 2 (ACE2) compared with human ACE2. In the present study, we propose a mouse model that allows estimating the influence of SARS-CoV-2 on the immune system. To mimic the effects of RBD-ACE2 high-affinity interaction, mice received the ACE2 inhibitor MLN-4760. To simulate virus loading, we applied 100 nm particles suspended in the solution of RBD via the oropharyngeal route to mice. In this model, MLN-4760 application enhanced neutrophil egress from the bone marrow to the bloodstream and RBD attracted neutrophils to the luminal side of the conducting airway epithelium. By contrast, inert 100 nm particles were not potent to stimulate neutrophil recruitment to the conducting airway mucosa. Using this model, and by altering the dosage of the ACE2 inhibitor, nanoparticles, and RBD, one can adapt it to investigate different COVID-19 states characterized with mild or severe airway inflammation.