Immunological non-responders (INR) are HIV-infected subjects that fail to restore CD4⁺ T-cell counts despite undetectable HIV viral load, which is controlled by highly active antiretroviral therapy (HAART). In INR, impaired immune restoration is linked to low-productive proliferation of memory CD4⁺ T-lymphocytes. Taking into account that T-cell ability to divide depends on the activity of metabolic pathways, we aimed to determine rates of mitochondrial respiration and glycolysis in memory CD4⁺ T-cells of INR. Two groups of HIV-infected HAART-treated patients were studied: immunological non-responders and subjects with an adequate immunological response to therapy (immunological responders – IR). Control (C) group comprised uninfected volunteers. In both groups of HIV-infected patients glycolytic activity of memory CD4⁺ T-cells was lower than that in C. Mitochondrial respiration rate in memory CD4⁺ T-cells derived from IR was comparable to that of C at basal state, however, after stimulation IR failed to reach the values of uninfected subjects. INR had the lowest mitochondrial respiration rate both at basal state and after stimulation. Taken together, the data presented herein demonstrate that low regenerative potential of memory CD4⁺ T-cells derived from INR might be linked to diminished lymphocytes’ metabolic activity.

Fullerenols are polyhydroxylated derivatives of fullerene (C₆₀(OH)_n) with antioxidant, antiviral, and antibacterial properties and potential biomedical applications due to their solubility and biocompatibility. However, comprehensive assessment of their cytotoxicity is required, particularly regarding their effects on immune system cells. This study investigated the effects of fullerenol C₆₀(OH)₂₄ (MST-Nano, St. Petersburg, Russia) on the viability, apoptosis, and metabolism of THP-1 human monocytic leukemia cells. Cells were treated with concentrations ranging from 0.25 to 1000 µg/mL and incubated for 24, 48, and 72 h. Viability, apoptosis, and nanoparticle association were assessed by flow cytometry; glycolysis and mitochondrial respiration were measured after 24 h on a Seahorse XFe96 analyzer (Agilent Technologies, Santa Clara, CA, USA). Results showed that the effects of fullerenol depend on concentration and exposure time. At 24 h, 750 µg/mL increased viability, while 1000 µg/mL induced apoptosis. After 48 and 72 h, apoptosis increased at concentrations ≥750 µg/mL, with reduced viability. Nanoparticle association correlated with concentration and inversely correlated with viability but was independent of incubation time. Metabolic analysis revealed decreased glycolysis at 750 µg/mL after 24 h, while mitochondrial respiration was unaffected. Thus, our study demonstrated that fullerenol nanoparticles were safe for the THP-1 monocytic cell line up to 500 µg/mL.

Infection with hepatitis C virus (HCV) is common among HIV-positive patients, with up to 50% of them being coinfected in Russia. While highly active antiretroviral therapy (HAART) suppresses HIV replication and restores the immune system of HIV-infected subjects, HCV coinfection interferes with CD4⁺T cell regeneration and increases the risk of patients’ morbidity and mortality. During HAART, HIVinfection progression and the immune system restoration efficiency largely depend on immune activation and CD4⁺T cell exhaustion. This study determined the level of activation, exhaustion, and cytokine production in CD4⁺T cells obtained from the peripheral blood of HAART-treated HIV/HCV coinfected and HIV monoinfected subjects. The study comprised 11 HIV/HCV coinfected individuals and 10 HIV monoinfected patients receiving HAART for more than two years, with a control group of 10 volunteers without the signs of HIV or HCV infections. Compared with healthy controls, HIV/HCV coinfected patients had an increased frequency of activated CD38⁺HLA-DR⁺ CD4⁺T lymphocytes (p < 0.05), a higher level of CD4⁺T cell exhaustion determined according to the TIGIT expression density per cell (p < 0.05), and a greater proportion of interferon-gamma (IFNγ)-producing CD4⁺T lymphocytes following activation (p < 0.05). The frequency of IFNγ-producing CD4⁺T cells in the donors’ blood positively correlated with the proportion of activated CD4⁺T cells (R = 0.514, p < 0.01). Despite having a large number of IFNγ-producing CD4⁺T lymphocytes, the HIV/HCV coinfected patients’ average production of IFNγ by CD4⁺T cells was significantly lower than that in healthy controls (p < 0.05). The IFNγ production in CD4⁺T lymphocytes did not depend on activation (p > 0.05). However, a negative correlation was established between the IFNγ production and the level of CD4⁺T cell exhaustion (R = -0.400, p < 0.05). The letter was also found to inversely correlate with the CD4⁺T cell counts in the donors’ peripheral blood (R = -0.598, p < 0.01). These data suggest that HCV coinfection leads to pronounced functional exhaustion of CD4⁺T cells and may aggravate the course of HIVinfection in patients receiving HAART.

T cells demonstrate high degree of complexity and broad range of functions, which distinguish them from other immune cells. Throughout their lifetime, T lymphocytes experience several functional states: quiescence, activation, proliferation, differentiation, performance of effector and regulatory functions, memory formation, and apoptosis. Metabolism supports all functions of T cells, providing lymphocytes with energy, biosynthetic substrates, and signaling molecules. Therefore, T cells usually restructure their metabolism as they transition from one functional state to another. Strong association between the metabolism and T cell functions implies that the immune response can be controlled by manipulating metabolic processes within T lymphocytes. This review aims to highlight the main metabolic adaptations necessary for the T cell function, as well as the recent progress in techniques to modulate metabolic features of lymphocytes.

Introduction/Objective: "Immunological non-responders" (INRs) are individuals living with HIV who are undergoing Highly Active Antiretroviral Therapy (HAART) but fail to restore their CD4⁺ T-cells count despite effective viral control. The incomplete immune restoration in INRs is often associated with the low-productive proliferation of memory CD4⁺ T lymphocytes. The ability of CD4⁺ T cells to divide is critically dependent on the glycolytic pathway, which supplies the necessary energy and building blocks for cell division. We hypothesize that impaired glycolytic activity in the memory CD4⁺ T cells of INRs contributes to their ineffective proliferation, ultimately limiting immune restoration. Methods: This study involved two groups of HIV-infected HAART-treated subjects: INR and Immunological Responders (IR). A third group consisted of healthy controls, comprising uninfected volunteers. To identify the metabolic factors contributing to immunological non-response to therapy, glucose uptake, and lactate production were measured in the memory CD4⁺ T cells from all three groups. Results: INR had the highest activation level in memory CD4+ T cells and the greatest glucose uptake. However, both groups of HIV-infected patients had significantly reduced lactate production compared to the healthy donors. Short-term phytohemagglutinin stimulation provoked an increase in lactate production in memory CD4+ T lymphocytes. Nevertheless, we found significantly reduced lactate production levels in activated memory CD4+ Т cells of INR an IR. Conclusion: In INRs, there is a discrepancy between the highly activated phenotype of memory CD4⁺ T lymphocytes and their glycolytic activity. This reduced glycolysis may explain the lowproductive proliferation of memory CD4⁺ T lymphocytes in INRs.

T lymphocytes are a highly diverse group of cells that play a pivotal role in the adaptive immune response. The T cell population consists of two subsets: CD4+T-helper cells and CD8+ cytotoxic T lymphocytes, each comprising cells with varying functionality and maturity levels. Inhibitory receptors such as PD-1 and TIGIT tightly regulate T lymphocyte functions to maintain immune homeostasis. However, the presence of inhibitory receptors on T cells is also associated with exhaustion. The specific characteristics of inhibitory receptor expression on CD4+ and CD8+T lymphocyte subsets are not fully understood. This study aimed to assess the expression of inhibitory receptors PD-1 and TIGIT on different subsets of CD4+ and CD8+T lymphocytes in healthy individuals. The study involved 10 relatively healthy volunteers, averaging 43 years. T lymphocytes subsets were identified using flow cytometry. CD4+ and CD8+T cells were classified as naive (CD45R0-CCR7+), central memory (CD45R0+CCR7+), effector memory (CD45R0+CCR7-), or terminally differentiated effectors (CD45R0-CCR7-) followed by analysis of PD-1 and TIGIT expression. The study showed that the expression of suppressor molecules PD-1 and TIGIT on T lymphocytes in healthy individuals is closely linked to their differentiation stage. The presence of cells carrying PD-1 and TIGIT receptors was significantly lower in naive T lymphocytes compared to more mature subsets (p 0.05). Affiliation with CD4+ or CD8+T cells also significantly influenced the nature of inhibitory receptor expression. CD8+T lymphocytes had more TIGIT-positive elements than CD4+T cells (p 0.01). Moreover, unlike PD-1, TIGIT was found on most memory and terminally differentiated effector CD8+T lymphocytes. These findings improve our understanding of how inhibitory receptors regulate T cell functions and emphasize the need to reconsider how we interpret data in the context of T lymphocyte exhaustion.