(1) Background: Biomarkers of efficacy for subcutaneous immunotherapy (SCIT) on allergic rhinitis have not been evaluated in details. The present study aims to assess the relevance of measuring of sIgE, sIgG4 and IgE/IgG4 ratio during SCIT in patients with allergic rhinitis; (2) Methods: 20 patients, 13 men and 7 women aged 19 to 58 years, with clinically manifested seasonal and perennial allergic rhinitis were studied. At the initiation and in the end of the three-year course of SCIT serum allergen-specific IgE and IgG4 were measured with ImmunoCAP system. The sIgE/sIgG4 ratio was calculated as a biomarker for immunologic effectiveness; (3) Results: There was a significant increase of sIgG4 antibodies (p < 0.05), while at the end of SCIT for the sIgE levels no significant changes were seen (p > 0.05). Moreover, 90% of patients showed a decrease of the IgE/IgG4 ratio; (4) Conclusions: In most of treated patients with AR, SCIT with Bulgarian allergen products leads to clear immunological changes. After a 3-year of SCIT there is a significant increase in allergen specific IgG4 levels and both decrease of sIgE and IgE/IgG4 ratio. sIgE, sIgG4 and IgE/IgG4 ratio can be used as a substantial biomarker for predicting immunological effectiveness of SCIT.

Objectives: Cytokine dysregulation has been proposed as one of the main culprits for severe COVID-19 and poor prognosis. We examined the parallel presence of lymphopoietic, proinflammatory, Th1, Th2, regulatory cytokines, and chemokines in the serum of 47 patients with mild, moderate, and severe COVID-19 and evaluated the association between cytokine concentrations and disease severity. Methods: A multiplex quantitative cytokine analysis ProcartaPlex™ immunoassay was applied, using the Luminex^TM 200X detection system (Invitrogen). Results: The concentrations of twelve cytokines: IL-18, IFN-gamma, TNF-alpha; IL-21; IL-1alpha, IL-1beta, IL-6, IL-22; IL-10, IL-1RA; IL-7 and IFN-alpha were consistently elevated in the studied serum samples. All examined chemokines—Eotaxin, GRO-alpha, IL-8, IP-10, MCP-1, MIP-1alpha, MIP-1beta, SDF-1alpha, and RANTES, were detectable in all studied groups, confirming their importance in mediating the adaptive immune response regardless of disease severity. The serum concentrations of six mediators: IL-1beta, IL-6, IL-18, IL-10, IL-8, and IP-10, showed statistically significant differences among the groups with different disease severity. IL-6, IL-1beta, and IL-10 were more significantly elevated in severe cases while milder symptoms were associated with lower levels of IL-8 and IP-10. Conclusion: Overall, the studied chemokines demonstrated an associated production in acute COVID-19 infection. A strong correlation was observed between the Th1 mediators IL-18 and IL-10 and the proinflammatory IL-6 in the severe COVID-19 group. Our results indicated that severe COVID-19 was characterized by a dysregulated cytokine pattern whereby the Th1 immune response is outweighed by the immunoregulatory response, while inhibitory signals cannot balance the hyperinflammatory response.

Immune memory to SARS-CoV-2 is key for establishing herd immunity and limiting the spread of the virus. The duration and qualities of T-cell-mediated protection in the settings of constantly evolving pathogens remain an open question. We conducted a cross-sectional study of SARS-CoV-2-specific CD4+ and CD8+ T-cell responses at several time points over 18 months (30–750 days) post mild/moderate infection with the aim to identify suitable methods and biomarkers for evaluation of long-term T-cell memory in peripheral blood. Included were 107 samples from 95 donors infected during the periods 03/2020–07/2021 and 09/2021–03/2022, coinciding with the prevalence of B.1.1.7 (alpha) and B.1.617.2 (delta) variants in Bulgaria. SARS-CoV-2-specific IFNγ+ T cells were measured in ELISpot in parallel with flow cytometry detection of AIM+ total and stem cell-like memory (T_SCM) CD4+ and CD8+ T cells after in vitro stimulation with peptide pools corresponding to the original and delta variants. We show that, unlike IFNγ+ T cells, AIM+ virus-specific CD4+ and CD8+ T_SCM are more adequate markers of T cell memory, even beyond 18 months post-infection. In the settings of circulating and evolving viruses, CD8+ T_SCM is remarkably stable, back-differentiated into effectors, and delivers immediate protection, regardless of the initial priming strain.

Background/Objectives: Restored CD4 absolute counts (CD4AC) and CD4/CD8 ratio in the setting of continuous antiretroviral treatment (ART) do not exclude a low-level immune activation associated with HIV reservoirs, microbial translocation, or the side effects of ART itself, which accelerates the aging of people living with HIV (PLHIV). To delineate biomarkers of incomplete immune restoration in PLHIV on successful ART, we evaluated T-lymphocyte mitochondrial parameters in relation to phenotypic markers of immune exhaustion and senescence. Methods: PLHIV with sustained viral suppression, CD4AC >500 and CD4/CD8 ratio >0.9 on ART (n = 39) were compared to age-matched ART-naïve donors (n = 27) and HIV(–) healthy controls (HC, n = 35). CD4 and CD8 differentiation and effector subsets (CCR7/CD45RA and CD27/CD28), activation, exhaustion, and senescence markers (CD38, CD39 Treg, CD57, TIGIT, and PD-1) were determined by flow cytometry. Mitochondrial mass (MM) and membrane potential (MMP) of CD8 and CD4 T cells were evaluated with MitoTracker Green and Red flow cytometry dyes. Results: ART+PLHIV differed from HC by increased CD4 TEMRA (5.3 (2.1–8.8) vs. 3.2 (1.6–4.4), p < 0.05), persistent TIGIT+CD57–CD27+CD28– CD8+ subset (53.9 (45.5–68.9) vs. 40.1 (26.7–58.5), p < 0.05), and expanding preapoptotic TIGIT–CD57+CD8+ effectors (9.2 (4.3–21.8) vs. 3.0 (1.5–7.3), p < 0.01) in correlation with increased CD8+ MMP (2527 (1675–4080) vs.1477 (1280–1691), p < 0.01). These aberrations were independent of age, time to ART, or ART duration, and were combined with increasing CD4 T cell MMP and MM. Conclusions: In spite of recovered CD4AC and CD4/CD8 ratio, the increased CD8+ MMP, combined with elevated markers of exhaustion and senescence in ART+PLHIV, signals a malfunction of the CD8 effector pool that may compromise viral reservoir latency.

Background/Objectives: Immunosenescence implies innate and adaptive immunity dysfunction, which naturally occurs with aging. It is a complex multifactorial process which can be triggered by either genetic changes, immune changes or both. Numerous research studies have shown that the process of senescence goes alongside chronic immune activation. The purpose of this study is to analyze the changes in the expression of genes associated with adaptive and innate immune responses in order to identify reliable biomarkers for immune aging. Methods: For that aim, 55 clinically healthy individuals of active age (21–65 years) were distributed based on immunophenotyping in two groups, with and without signs of premature senescence. A gene expression analysis was subsequently made on those two groups, and the differentially expressed genes were presented and interpreted. Results: Altogether, forty-eight (48) genes exhibited differential expression between the two groups, most of which showed up-regulation (45) (fold change more than 2), and only three were down-regulated (fold change less than −2). The highest positive fold change showed IL-1β (10.76), BCL6 (13.25) and CCL4 (15.91), while the highest negative fold changes were documented for IL23R (−3.10), IL5 (−2.66) and PTGS2 (COX-2) (−2.15). Conclusions: Our results reveal that immunosenescence is positively associated with chronic inflammation, which is typical for the aging process. On the other hand, we identified markers of possible protective effects against oxidative stress and tumorigenesis. These findings can aid the early diagnosis of chronic degenerative diseases in subclinical phase, as well as the development of strategies to prevent the processes of premature immune aging.

Background: Chronic Fatigue Syndrome (CFS), also known as Myalgic Encephalomyelitis (ME), is a debilitating condition characterized by persistent fatigue and multisystemic symptoms, such as cognitive impairment, musculoskeletal pain, and post-exertional malaise. Recently, parallels have been drawn between ME/CFS and Long COVID, a post-viral syndrome following infection with SARS-CoV-2, which shares many clinical features with CFS. Both conditions involve chronic immune activation, raising questions about their immunopathological overlap. Objectives: This study aimed to compare immune biomarkers between patients with ME/CFS or Long COVID and healthy controls to explore shared immune dysfunction. Methods: We analyzed lymphocyte subsets, cytokine profiles, psychological status and their correlations in 190 participants, 65 with CFS, 54 with Long COVID, and 70 healthy controls. Results: When compared to healthy subjects, results in both conditions were marked by lower levels of lymphocytes (CFS—2.472 × 10⁹/L, p = 0.006, LC—2.051 × 10⁹/L, p = 0.009), CD8⁺ T cells (CFS—0.394 × 10⁹/L, p = 0.001, LC—0.404 × 10⁹/L, p = 0.001), and NK cells (CFS—0.205 × 10⁹/L, p = 0.001, LC—0.180 × 10⁹/L, p = 0.001), and higher levels of proinflammatory cytokines such as IL-6 (CFS—3.35 pg/mL, p = 0.050 LC—4.04 pg/mL, p = 0.001), TNF (CFS—2.64 pg/mL, p = 0.023, LC—2.50 pg/mL, p = 0.025), IL-4 (CFS—3.72 pg/mL, p = 0.041, LC—3.45 pg/mL, p = 0.048), and IL-10 (CFS—2.29 pg/mL, p = 0.039, LC—2.25 pg/mL, p = 0.018). Conclusions: Notably, there were no significant differences between CFS and Long COVID patients in the tested biomarkers. These results demonstrate that ME/CFS and Long COVID display comparable immune and inflammatory profiles, with no significant biomarker differences observed between the two groups.