Adaptive immunity to SARS-CoV-2 infection: A systematic review.

Background: There is evidence that the adaptive or acquired immune system is one of the crucial variables in differentiating the course of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This work aimed to analyze the immunopathological aspects of adaptive immunity that are involved in the progression of this disease. Methods: This is a systematic review based on articles that included experimental evidence from in vitro assays, cohort studies, reviews, cross-sectional and case-control studies from PubMed, SciELO, MEDLINE, and Lilacs databases in English, Portuguese, or Spanish between January 2020 and July 2022. Results: Fifty-six articles were finalized for this review. CD4+ T cells were the most resolutive in the health-disease process compared with B cells and CD8+ T lymphocytes. The predominant subpopulations of T helper lymphocytes (Th) in critically ill patients are Th1, Th2, Th17 (without their main characteristics) and regulatory T cells (Treg), while in mild cases there is an influx of Th1, Th2, Th17 and follicular T helper cells (Tfh). These cells are responsible for the secretion of cytokines, including interleukin (IL) - 6, IL-4, IL-10, IL-7, IL-22, IL-21, IL-15, IL-1α, IL-23, IL-5, IL-13, IL-2, IL-17, tumor necrosis factor alpha (TNF-α), CXC motivating ligand (CXCL) 8, CXCL9 and tumor growth factor beta (TGF-ß), with the abovementioned first 8 inflammatory mediators related to clinical benefits, while the others to a poor prognosis. Some CD8+ T lymphocyte markers are associated with the severity of the disease, such as human leukocyte antigen (HLA-DR) and programmed cell death protein 1 (PD-1). Among the antibodies produced by SARS-CoV-2, Immunoglobulin (Ig) A stood out due to its potent release associated with a more severe clinical form. Conclusions: It is concluded that through this study it is possible to have a brief overview of the main immunological biomarkers and their function during SARS-CoV-2 infection in particular cell types. In critically ill individuals, adaptive immunity is varied, aberrantly compromised, and late. In particular, the T-cell response is also an essential and necessary component in immunological memory and therefore should be addressed in vaccine formulation strategies.

Evaluation of the immunomodulatory effects of interleukin-10 on peripheral blood immune cells of COVID-19 patients: Implication for COVID-19 therapy.

Objective: Several therapies with immune-modulatory functions have been proposed to reduce the overwhelmed inflammation associated with COVID-19. Here we investigated the impact of IL-10 in COVID-19, through the ex-vivo assessment of the effects of exogenous IL-10 on SARS-CoV-2-specific-response using a whole-blood platform. Methods: Two cohorts were evaluated: in "study population A", plasma levels of 27 immune factors were measured by a multiplex (Luminex) assay in 39 hospitalized "COVID-19 patients" and 29 "NO COVID-19 controls" all unvaccinated. In "study population B", 29 COVID-19 patients and 30 NO COVID-19-Vaccinated Controls (NO COVID-19-VCs) were prospectively enrolled for the IL-10 study. Whole-blood was stimulated overnight with SARS-COV-2 antigens and then treated with IL-10. Plasma was collected and used for ELISA and multiplex assay. In parallel, whole-blood was stimulated and used for flow cytometry analysis. Results: Baseline levels of several immune factors, including IL-10, were significantly elevated in COVID-19 patients compared with NO COVID-19 subjects in "study population A". Among them, IL-2, FGF, IFN-γ, and MCP-1 reached their highest levels within the second week of infection and then decreased. To note that, MCP-1 levels remained significantly elevated compared with controls. IL-10, GM-CSF, and IL-6 increased later and showed an increasing trend over time. Moreover, exogenous addition of IL-10 significantly downregulated IFN-γ response and several other immune factors in both COVID-19 patients and NO COVID-19-VCs evaluated by ELISA and a multiplex analysis (Luminex) in "study population B". Importantly, IL-10 did not affect cell survival, but decreased the frequencies of T-cells producing IFN-γ, TNF-α, and IL-2 (p<0.05) and down-modulated HLA-DR expression on CD8+ and NK cells. Conclusion: This study provides important insights into immune modulating effects of IL-10 in COVID-19 and may provide valuable information regarding the further in vivo investigations.

Polyclonal expansion of TCR Vbeta 21.3+ CD4+ and CD8+ T cells is a hallmark of Multisystem Inflammatory Syndrome in Children.

Multiple Inflammatory Syndrome in Children (MIS-C) is a delayed and severe complication of SARS-CoV-2 infection that strikes previously healthy children. As MIS-C combines clinical features of Kawasaki disease and Toxic Shock Syndrome (TSS), we aimed to compare the immunological profile of pediatric patients with these different conditions. We analyzed blood cytokine expression, and the T cell repertoire and phenotype in 36 MIS-C cases, which were compared to 16 KD, 58 TSS, and 42 COVID-19 cases. We observed an increase of serum inflammatory cytokines (IL-6, IL-10, IL-18, TNF-α, IFNγ, CD25s, MCP1, IL-1RA) in MIS-C, TSS and KD, contrasting with low expression of HLA-DR in monocytes. We detected a specific expansion of activated T cells expressing the Vß21.3 T cell receptor ß chain variable region in both CD4 and CD8 subsets in 75% of MIS-C patients and not in any patient with TSS, KD, or acute COVID-19; this correlated with the cytokine storm detected. The T cell repertoire returned to baseline within weeks after MIS-C resolution. Vß21.3+ T cells from MIS-C patients expressed high levels of HLA-DR, CD38 and CX3CR1 but had weak responses to SARS-CoV-2 peptides in vitro. Consistently, the T cell expansion was not associated with specific classical HLA alleles. Thus, our data suggested that MIS-C is characterized by a polyclonal Vß21.3 T cell expansion not directed against SARS-CoV-2 antigenic peptides, which is not seen in KD, TSS and acute COVID-19.

Different degree of cytokinemia and T-cell activation according to serum IL-6 levels in critical COVID-19.

Introduction: Tocilizumab, a humanized anti-interleukin-6 receptor (IL-6R) antibody, is recommended for the treatment of severe to critical coronavirus diseases 2019 (COVID-19). However, there were conflicting results on the efficacy of tocilizumab. Therefore, we hypothesized that the differences in tocilizumab efficacy may stem from the different immune responses of critical COVID-19 patients. In this study, we described two groups of immunologically distinct COVID-19 patients, based on their IL-6 response. Methods: We prospectively enrolled critical COVID-19 patients, requiring oxygen support with a high flow nasal cannula or a mechanical ventilator, and analyzed their serial samples. An enzyme-linked immunosorbent assay and flow cytometry were used to evaluate the cytokine kinetics and cellular immune responses, respectively. Results: A total of nine patients with critical COVID-19 were included. The high (n = 5) and low IL-6 (n = 4) groups were distinguished by their peak serum IL-6 levels, using 400 pg/mL as the cut-off value. Although the difference of flow cytometric data did not reach the level of statistical significance, the levels of pro-inflammatory cytokines and the frequencies of intermediate monocytes (CD14+CD16+), IFN-γ+ CD4+ or CD8+ T cells, and HLA-DR+PD-1+ CD4+ T cells were higher in the high IL-6 group than in the low IL-6 group. Conclusion: There were distinctive two groups of critical COVID-19 according to serum IL-6 levels having different degrees of cytokinemia and T-cell responses. Our results indicate that the use of immune modulators should be more tailored in patients with critical COVID-19.

Impaired adaptive immune response in COVID-19 convalescent patients with hematological malignancies.

OBJECTIVES: The immune dysregulation during SARS-CoV-2 has the potential to worsen immune homeostasis after recovery. Patients with hematological malignancies with COVID-19 have changes both in the innate and adaptive immune responses. Little is known about the severity of immune dysfunction following recovery from COVID-19 in hematological patients. METHODS: Here, we performed a comprehensive analysis of the lymphocyte subsets in peripheral blood mononuclear cells by FACS Canto II in 55 patients, including 42 with hematological malignancies 4-6 weeks after COVID-19. RESULTS: Hematological COVID-19 convalescents had deep reduction in CD3+ T cells, including helper T cells (CD3 + CD4+), naïve helper T cells (CD3 + CD4 + CD45RA+), and memory CD4+ T cells among with extremely low levels of Treg cells and decreased expression of both TCRα/ß and TCRγ/δ. Severe immune dysregulation in hematological convalescents was expressed by increased activation of T lymphocytes, both as elevated levels of activated T cells (CD3 + HLA-DR+) and activated cytotoxic T cells (CD3 + CD8 + HLA-DR+). CONCLUSIONS: Our findings showed a profound impairment of the adaptive immune response in hematological convalescents which might be a result of persistent activation of T cells. Convalescents with lymphoid malignancies showed more pronounced depletion of key T lymphocytes subpopulations in creating an effective adaptive response and immune memory.

The Comparison of Monocyte Human Leukocyte Antigen-D-Related (mHLA-DR) Expression Levels Between Corona Virus Disease 2019 (COVID-19) Patients and Healthy Subjects.

BACKGROUND: SARS-CoV-2 can trigger a dysfunctional immune response in COVID-19 patients and lead to immunosuppression. HLA-DR molecule expressed on the surface of monocytes, known as mHLA-DR, has been widely used as a reliable marker of immunosuppression. Downregulation of mHLA-DR reflects an immunosuppressed state. This study aimed to compare the expression level of mHLA-DR between COVID-19 patients and healthy subjects concerning immune system dysregulation that can be triggered by SARS-CoV-2 and lead to immunosuppression. METHODS: This was an analytic observational study with a cross-sectional design that measured the mHLA-DR expression in EDTA blood samples from 34 COVID-19 patients and 15 healthy subjects using the BD FACSLyricTM Flow Cytometry System. The mHLA-DR examination results were expressed in AB/C (antibodies bound per cell) that were quantified using a standard curve constructed with Quantibrite phycoerythrin beads (BD Biosciences). RESULTS: Expression of mHLA-DR in COVID-19 patients (n = 34) were 21,201 [2,646-92,384] AB/C, with 40,543.5 [9,797-92,384] AB/C mild cases (n = 22), 21,201 [9,831-31,930] AB/C moderate cases (n = 6), and 7,496 [2,646-13,674] AB/C severe to critical cases (n= 6). Expression of mHLA-DR in healthy subjects (n = 15) was 43,161 [25,147-89,846] AB/C. Based on the Mann-Whitney U test, the mHLA-DR expression in COVID-19 patients significantly differed from the mHLA-DR expression in healthy subjects (p = 0.010). CONCLUSION: The level of mHLA-DR expression in COVID-19 patients was lower and significantly different from healthy subjects. Moreover, immunosuppression could be indicated by the decrease of mHLA-DR expression, which was below the reference range found in severe to critically ill COVID-19 patients.

Multivariate indicators of disease severity in COVID-19.

The novel coronavirus pandemic continues to cause significant morbidity and mortality around the world. Diverse clinical presentations prompted numerous attempts to predict disease severity to improve care and patient outcomes. Equally important is understanding the mechanisms underlying such divergent disease outcomes. Multivariate modeling was used here to define the most distinctive features that separate COVID-19 from healthy controls and severe from moderate disease. Using discriminant analysis and binary logistic regression models we could distinguish between severe disease, moderate disease, and control with rates of correct classifications ranging from 71 to 100%. The distinction of severe and moderate disease was most reliant on the depletion of natural killer cells and activated class-switched memory B cells, increased frequency of neutrophils, and decreased expression of the activation marker HLA-DR on monocytes in patients with severe disease. An increased frequency of activated class-switched memory B cells and activated neutrophils was seen in moderate compared to severe disease and control. Our results suggest that natural killer cells, activated class-switched memory B cells, and activated neutrophils are important for protection against severe disease. We show that binary logistic regression was superior to discriminant analysis by attaining higher rates of correct classification based on immune profiles. We discuss the utility of these multivariate techniques in biomedical sciences, contrast their mathematical basis and limitations, and propose strategies to overcome such limitations.

Endotoxin tolerance and low activation of TLR-4/NF-κB axis in monocytes of COVID-19 patients.

Higher endotoxin in the circulation may indicate a compromised state of host immune response against coinfections in severe COVID-19 patients. We evaluated the inflammatory response of monocytes from COVID-19 patients after lipopolysaccharide (LPS) challenge. Whole blood samples of healthy controls, patients with mild COVID-19, and patients with severe COVID-19 were incubated with LPS for 2 h. Severe COVID-19 patients presented higher LPS and sCD14 levels in the plasma than healthy controls and mild COVID-19 patients. In non-stimulated in vitro condition, severe COVID-19 patients presented higher inflammatory cytokines and PGE-2 levels and CD14 + HLA-DRlow monocytes frequency than controls. Moreover, severe COVID-19 patients presented higher NF-κB p65 phosphorylation in CD14 + HLA-DRlow, as well as higher expression of TLR-4 and NF-κB p65 phosphorylation in CD14 + HLA-DRhigh compared to controls. The stimulation of LPS in whole blood of severe COVID-19 patients leads to lower cytokine production but higher PGE-2 levels compared to controls. Endotoxin challenge with both concentrations reduced the frequency of CD14 + HLA-DRlow in severe COVID-19 patients, but the increases in TLR-4 expression and NF-κB p65 phosphorylation were more pronounced in both CD14 + monocytes of healthy controls and mild COVID-19 patients compared to severe COVID-19 group. We conclude that acute SARS-CoV-2 infection is associated with diminished endotoxin response in monocytes. KEY MESSAGES: Severe COVID-19 patients had higher levels of LPS and systemic IL-6 and TNF-α. Severe COVID-19 patients presented higher CD14+HLA-DRlow monocytes. Increased TLR-4/NF-κB axis was identified in monocytes of severe COVID-19. Blunted production of cytokines after whole blood LPS stimulation in severe COVID-19. Lower TLR-4/NF-κB activation in monocytes after LPS stimulation in severe COVID-19.

Increased frequency of CD14+HLA-DR-/low cells in type 2 diabetes patients with poor glycemic control.

AIMS: Type 2 diabetes (T2DM) is associated with alterations of the immune response and T2DM patients have an increased risk for infections and certain sorts of cancers. Although CD14+HLA-DR-/low cells have emerged as important mediators of immunosuppression in several pathologies, including cancer and non-malignant diseases, the presence of these cells in T2DM is not fully characterized. METHODS: In this study, we evaluated the frequency of CD14+HLA-DR-/low cells in non-obese T2DM patients and their association with glycemic control. Peripheral blood mononuclear cells were isolated from healthy controls (HC, n = 24) and non-obese T2DM patients (n = 25), the population was evaluated by flow cytometry, and an analysis of correlation between cell frequencies and clinical variables was performed. RESULTS: CD14+HLA-DR-/low monocytes were expanded in patients with T2DM compared to HC regardless of weight. Among the subjects with T2DM, the frequency of CD14+HLA-DR-/low was higher in patients with poor glycemic control (HbA1c > 9%) compared to those with better glycemic control (HbA1c < 9%) and, positively correlated with the years since the diagnosis of T2DM, the age of the patients and the glycemic index. CONCLUSIONS: An increased frequency of CD14+HLA-DR-/low cells in the blood of T2DM patients was recorded. The influence of hyperglycemia seems to be independent of obesity, but related to glycemic control and age.

Monocytic HLA-DR Expression in Immune Responses of Acute Pancreatitis and COVID-19.

Acute pancreatitis is a common gastrointestinal disease with increasing incidence worldwide. COVID-19 is a potentially life-threatening contagious disease spread throughout the world, caused by severe acute respiratory syndrome coronavirus 2. More severe forms of both diseases exhibit commonalities with dysregulated immune responses resulting in amplified inflammation and susceptibility to infection. Human leucocyte antigen (HLA)-DR, expressed on antigen-presenting cells, acts as an indicator of immune function. Research advances have highlighted the predictive values of monocytic HLA-DR (mHLA-DR) expression for disease severity and infectious complications in both acute pancreatitis and COVID-19 patients. While the regulatory mechanism of altered mHLA-DR expression remains unclear, HLA-DR-/low monocytic myeloid-derived suppressor cells are potent drivers of immunosuppression and poor outcomes in these diseases. Future studies with mHLA-DR-guided enrollment or targeted immunotherapy are warranted in more severe cases of patients with acute pancreatitis and COVID-19.

Monitoring of the Forgotten Immune System during Critical Illness-A Narrative Review.

Immune organ failure is frequent in critical illness independent of its cause and has been acknowledged for a long time. Most patients admitted to the ICU, whether featuring infection, trauma, or other tissue injury, have high levels of alarmins expression in tissues or systemically which then activate innate and adaptive responses. Although necessary, this response is frequently maladaptive and leads to organ dysfunction. In addition, the counter-response aiming to restore homeostasis and repair injury can also be detrimental and contribute to persistent chronic illness. Despite intensive research on this topic in the last 40 years, the immune system is not routinely monitored in critical care units. In this narrative review we will first discuss the inflammatory response after acute illness and the players of maladaptive response, focusing on neutrophils, monocytes, and T cells. We will then go through commonly used biomarkers, like C-reactive protein, procalcitonin and pancreatic stone protein (PSP) and what they monitor. Next, we will discuss the strengths and limitations of flow cytometry and related techniques as an essential tool for more in-depth immune monitoring and end with a presentation of the most promising cell associated markers, namely HLA-DR expression on monocytes, neutrophil expression of CD64 and PD-1 expression on T cells. In sum, immune monitoring critically ill patients is a forgotten and missing piece in the monitoring capacity of intensive care units. New technology, including bed-side equipment and in deep cell phenotyping using emerging multiplexing techniques will likely allow the definition of endotypes and a more personalized care in the future.

Spleen tyrosine kinase inhibition restores myeloid homeostasis in COVID-19.

Spleen tyrosine kinase (SYK) is a previously unidentified therapeutic target that inhibits neutrophil and macrophage activation in coronavirus disease 2019 (COVID-19). Fostamatinib, a SYK inhibitor, was studied in a phase 2 placebo-controlled randomized clinical trial and was associated with improvements in many secondary end points related to efficacy. Here, we used a multiomic approach to evaluate cellular and soluble immune mediator responses of patients enrolled in this trial. We demonstrated that SYK inhibition was associated with reduced neutrophil activation, increased circulation of mature neutrophils (CD10+CD33-), and decreased circulation of low-density granulocytes and polymorphonuclear myeloid-derived suppressor cells (HLA-DR-CD33+CD11b-). SYK inhibition was also associated with normalization of transcriptional activity in circulating monocytes relative to healthy controls, an increase in frequency of circulating nonclassical and HLA-DRhi classical monocyte populations, and restoration of interferon responses. Together, these data suggest that SYK inhibition may mitigate proinflammatory myeloid cellular and soluble mediator responses thought to contribute to immunopathogenesis of severe COVID-19.

Evaluation of Myeloid-derived Suppressor Cells in the Blood of Iranian COVID-19 Patients.

The cytokine storm and lymphopenia are reported in coronavirus disease 2019 (COVID-19). Myeloid-derived suppressive cells (MDSCs) exist in two different forms, granulocyte (G-MDSCs) and monocytic (M-MDSCs), that both suppress T-cell function. In COVID-19, the role of chemokines such as interleukin (IL)-8 in recruiting MDSCs is unclear. A recent report has correlated IL-8 and MDSCs with poor clinical outcomes in melanoma patients. In the current study, we evaluated the frequency of MDSCs and their correlation with serum IL-8 levels in severe COVID-19 patients from Iran. Thirty-seven severe patients (8 on ventilation, 29 without ventilation), thirteen moderate COVID-19 patients, and eight healthy subjects participated in this study between 10th April 2020 and 9th March 2021. Clinical and biochemical features, serum, and whole blood were obtained. CD14, CD15, CD11b, and HLA-DR expression on MDSCs was measured by flow cytometry. COVID-19 patients compared to healthy subjects had a greater frequency of M-MDSCs (12.7±13.3% vs 0.19±0.20%,), G-MDSCs (15.8±12.6% vs 0.35±0.40%,) and total-MDSCs (27.5±17.3% vs 0.55±0.41%,). M-MDSC (16.8±15.8% vs 5.4±4.8%,) and total-MDSC (33.3±18.5% vs 17.3±13.3%) frequency was higher in non- ventilated compared to moderate COVID-19 subjects. Serum IL-8 levels were higher in patients with COVID-19 than in normal healthy subjects (6.4±7.8 vs. 0.10±00 pg/mL). Ventilated patients (15.7±6.7 pg/mL), non-ventilated patients (5.7±2.7 pg/mL) and moderate patients (2.8±3.0 pg/mL) had significantly different levels of IL-8.  A negative correlation was found between the frequency of G-MDSCs and the international normalized ratio (INR) test (r=-0.39), and between the frequency of total-MDSCs and oxygen saturation (%) (r=-0.39). COVID-19 patients with severe non-ventilated disease had the highest levels of M-MDSCs. In addition to systemic MDSCs, lung, serum IL-8, and other inflammatory biomarkers should be measured.

Cutting Edge: Hyperinflammatory Monocytes Expressing CD56 Abound in Severe COVID-19 Patients.

Proinflammatory monocytes play a preponderant role in the development of a cytokine storm causing fatal consequences in coronavirus disease 2019 (COVID-19) patients, highlighting the importance of analyzing in more detail monocyte distribution in these patients. In this study, we identified an atypical monocyte subpopulation expressing CD56 molecules that showed a low level of HLA-DR and high level of l-selectin. They released higher amounts of TNF-α and IL-6 and expressed genes associated with an excessive inflammatory process. Remarkably, the frequency of CD56+ monocytes inversely correlated with that of CD16+ monocytes and a high CD56+/CD16+monocyte ratio was associated with both disease severity and mortality, as well as with serum concentration of type I IFN, a factor able to induce the appearance of CD56+ monocytes. In conclusion, severe COVID-19 is characterized by the abundance of hyperinflammatory CD56+ monocytes, which could represent a novel marker with prognostic significance and, possibly, a therapeutic target for controlling the inflammatory process occurring during COVID-19.

Immune Cells Profiles In The Peripheral Blood Of Patients With Moderate To Severe COVID-19 And Healthy Subjects With and Without Vaccination With The Pfizer-BioNTech mRNA Vaccine.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the causative agent of Coronavirus disease 2019 (COVID-19), has caused a global crisis. Patients with COVID-19 present with a range of clinical manifestations, from no symptoms to severe illness. However, little is known about the profiles of immune cells required to protect against SARS-CoV-2. This study was performed to determine the immune cells profiles in the peripheral blood of COVID-19 patients with moderate to severe disease (n=52), and compare the findings with those from healthy subjects vaccinated with Pfizer BioNTech mRNA vaccine (VS) (n=62), and non-vaccinated healthy subjects (HS) (n=30) from Kuwait. Absolute counts and percentages of total lymphocytes and lymphocyte subsets (CD3+ T cells, CD4+ T cells, CD8+ T cells, CD19+ B cells, and CD16+CD56+ NK cells) in the peripheral blood of the three groups were analyzed using flow cytometry. The results showed that the absolute counts of total lymphocytes, CD3+, CD4+, and CD8+ T cells, CD19+ B cells, and CD56+ NK cells, were significantly lower in COVID-19 patients than normal healthy controls and vaccinated subjects. The percentages of CD3+ and CD4+ T lymphocytes were also significantly lower in the COVID-19 patients. However, the percentage of CD16+CD56+ NK cells was significantly higher in the peripheral blood of COVID-19 patients, compared to the HS and VS groups with no detectable differences in the percentages of CD8+ T cells and CD19+ B cells between the three groups. Analysis of the monocyte subsets has showed a significantly higher percentage of CD14+HLA-DR+ monocytes in COVID-19 patients compared to HS whereas the inflammatory CD14+CD16+ HLA-DR+ monocytes, and the non-classical CD16+HLA-DR+ monocytes showed significantly lower frequency in the blood of the patients than that of HS. These findings demonstrate perturbations of both innate and adaptive immune cell subsets that reflect dysregulated host responses in COVID-19 patients with moderate to severe disease.

Therapeutic Hyperthermia Is Associated With Improved Survival in Afebrile Critically Ill Patients With Sepsis: A Pilot Randomized Trial.

OBJECTIVES: To test the hypothesis that forced-air warming of critically ill afebrile sepsis patients improves immune function compared to standard temperature management. DESIGN: Single-center, prospective, open-label, randomized controlled trial. SETTING: One thousand two hundred-bed academic medical center. PATIENTS: Eligible patients were mechanically ventilated septic adults with: 1) a diagnosis of sepsis within 48 hours of enrollment; 2) anticipated need for mechanical ventilation of greater than 48 hours; and 3) a maximum temperature less than 38.3°C within the 24 hours prior to enrollment. Primary exclusion criteria included: immunologic diseases, immune-suppressing medications, and any existing condition sensitive to therapeutic hyperthermia (e.g., brain injury). The primary outcome was monocyte human leukocyte antigen (HLA)-DR expression, with secondary outcomes of CD3/CD28-induced interferon gamma (IFN-γ) production, mortality, and 28-day hospital-free days. INTERVENTIONS: External warming using a forced-air warming blanket for 48 hours, with a goal temperature 1.5°C above the lowest temperature documented in the previous 24 hours. MEASUREMENTS AND MAIN RESULTS: We enrolled 56 participants in the study. No differences were observed between the groups in HLA-DR expression (692 vs 2,002; p = 0.396) or IFN-γ production (31 vs 69; p = 0.678). Participants allocated to external warming had lower 28-day mortality (18% vs 43%; absolute risk reduction, 25%; 95% CI, 2-48%) and more 28-day hospital-free days (difference, 2.6 d; 95% CI, 0-11.6). CONCLUSIONS: Participants randomized to external forced-air warming did not have a difference in HLA-DR expression or IFN-γ production. In this pilot study, however, 28-day mortality was lower in the intervention group. Future research should seek to better elucidate the impact of temperature modulation on immune and nonimmune organ failure pathways in sepsis.

Lymphocyte Phenotyping and HLA-DR Expression over the Course of COVID-19 Infection in Patients with Different Disease Severity.

BACKGROUND: The role of lymphocyte subsets in the diagnosis and follow up of COVID-19 is still unclear. So, we aim to study the changes in lymphocyte subsets and HLA-DR expression in the peripheral blood of hospitalized COVID-19 patients. METHODS: Lymphocyte subsets and HLA-DR expression were detected in the peripheral blood of 36 hospitalized patients of COVID-19; their data were compared to that of 36 healthy controls of comparable age and gender. RESULTS: Total lymphocytes, the percentage of CD3 T, CD4 T and CD8 T cells significantly decreased, while that of CD 56 cells significantly increased in SARS-CoV-2 infected patients. The expression of HLA-DR is down regulated in these cells. Neutrophil/lymphocyte ratio, neutrophil/CD3 ratio, neutrophil/CD4 ratio, and neutrophil/CD8 ratio are significantly increased in patients compared with controls. The absolute count of CD3, CD4, CD8 and CD19 cells, significantly decreased in SARS-CoV-2 infected patients. CONCLUSIONS: A marked reduction in CD8+T and CD4+T count together with HLA-DR cell expression with obvious impairment in cellular immunity has been detected in patients with more severe impairment and progressive course for the disease.

Activated CD8+CD38+ Cells Are Associated With Worse Clinical Outcome in Hospitalized COVID-19 Patients.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), that spread around the world during the past 2 years, has infected more than 260 million people worldwide and has imposed an important burden on the healthcare system. Several risk factors associated with unfavorable outcome were identified, including elderly age, selected comorbidities, immune suppression as well as laboratory markers. The role of immune system in the pathophysiology of SARS-CoV-2 infection is indisputable: while an appropriate function of the immune system is important for a rapid clearance of the virus, progression to the severe and critical phases of the disease is related to an exaggerated immune response associated with a cytokine storm. We analyzed differences and longitudinal changes in selected immune parameters in 823 adult COVID-19 patients hospitalized in the Martin University Hospital, Martin, Slovakia. Examined parameters included the differential blood cell counts, various parameters of cellular and humoral immunity (serum concentration of immunoglobulins, C4 and C3), lymphocyte subsets (CD3+, CD4+, CD8+, CD19+, NK cells, CD4+CD45RO+), expression of activation (HLA-DR, CD38) and inhibition markers (CD159/NKG2A). Besides already known changes in the differential blood cell counts and basic lymphocyte subsets, we found significantly higher proportion of CD8+CD38+ cells and significantly lower proportion of CD8+NKG2A+ and NK NKG2A+ cells on admission in non-survivors, compared to survivors; recovery in survivors was associated with a significant increase in the expression of HLA-DR and with a significant decrease of the proportion of CD8+CD38+cells. Furthermore, patients with fatal outcome had significantly lower concentrations of C3 and IgM on admission. However, none of the examined parameters had sufficient sensitivity or specificity to be considered a biomarker of fatal outcome. Understanding the dynamic changes in immune profile of COVID-19 patients may help us to better understand the pathophysiology of the disease, potentially improve management of hospitalized patients and enable proper timing and selection of immunomodulator drugs.

T cell response against SARS-CoV-2 persists after one year in patients surviving severe COVID-19.

BACKGROUND: In critically ill COVID-19 patients, the initial response to SARS-CoV-2 infection is characterized by major immune dysfunctions. The capacity of these severe patients to mount a robust and persistent SARS-CoV-2 specific T cell response despite the presence of severe immune alterations during the ICU stay is unknown. METHODS: Critically ill COVID-19 patients were sampled five times during the ICU stay and 9 and 13 months afterwards. Immune monitoring included counts of lymphocyte subpopulations, HLA-DR expression on monocytes, plasma IL-6 and IL-10 concentrations, anti-SARS-CoV-2 IgG levels and T cell proliferation in response to three SARS-CoV-2 antigens. FINDINGS: Despite the presence of major lymphopenia and decreased monocyte HLA-DR expression during the ICU stay, convalescent critically ill COVID-19 patients consistently generated adaptive and humoral immune responses against SARS-CoV-2 maintained for more than one year after hospital discharge. Patients with long hospital stays presented with stronger anti-SARS-CoV-2 specific T cell response but no difference in anti-SARS-CoV2 IgG levels. INTERPRETATION: Convalescent critically ill COVID-19 patients consistently generated a memory immune response against SARS-CoV-2 maintained for more than one year after hospital discharge. In recovered individuals, the intensity of SARS-CoV-2 specific T cell response was dependent on length of hospital stay. FUNDING: This observational study was supported by funds from the Hospices Civils de Lyon, Fondation HCL, Claude Bernard Lyon 1 University and Région Auvergne Rhône-Alpes and by partial funding by REACTing (Research and ACTion targeting emerging infectious diseases) INSERM, France and a donation from Fondation AnBer (http://fondationanber.fr/).