Innate immunology in COVID-19-a living review. Part I: viral entry, sensing and evasion

Neutrophil/Lymphocyte Ratio (NLR) and Lymphocyte/Monocyte Ratio (LMR) - Risk of Death Inflammatory Biomarkers in Patients with COVID-19

Aim

The aim of our retrospective study was search for new prognostic parameters, which can help quickly and cheaply identify patients with risk for severe course of SARS-CoV-2 infection.

Materials and Methods

The following peripheral blood combination biomarkers were calculated: NLR (neutrophil/lymphocytes ratio), LMR (lymphocyte/monocyte ratio), PLR (platelet/lymphocyte ratio), dNLR (neutrophils/(white blood cells - neutrophils)), NLPR (neutrophil/(lymphocyte × platelet ratio)) in 374 patients who were admitted to the Temporary Hospital no 2 of Clinical Hospital in Bialystok (Poland) with COVID-19. The patients were divided into four groups depending on the severity of the course of COVID-19 using MEWS classification.

Results

The NLR and dNLR were significantly increased with the severity of COVID-19, according to MEWS score. The AUC for the assessed parameters was higher in predicting death in patients with COVID-19: NLR (0.656, p=0.0018, cut-off=6.22), dNLR (0.615, p=0.02, cut-off=3.52) and LMR (0.609, p=0.03, cut-off=2.06). Multivariate COX regression analysis showed that NLR median above 5.56 (OR: 1.050, P=0.002), LMR median below 2.23 (OR: 1.021, P=0.011), and age >75 years old (OR: 1.072, P=0.000) had a significant association with high risk of death during COVID-19.

Conclusion

Our results indicate that NLR, dNLR, and LMR calculated on admission to the hospital can quickly and easy identify patients with risk of a more severe course of COVID-19. Increase NLR and decrease LMR have a significant predictive value in COVID-19 patient's mortality and might be a potential biomarker for predicting death in COVID-19 patients.

Dynamic Evaluation of Natural Killer Cells Subpopulations in COVID-19 Patients

The aim of the study was to evaluate the dynamic changes of the total Natural Killer (NK) cells and different NK subpopulations according to their differentiated expression of CD16/CD56 in COVID-19 patients. Blood samples with EDTA were analyzed on day 1 (admission moment), day 5, and day 10 for the NK subtypes. At least 30,000 singlets were collected for each sample and white blood cells were gated in CD45/SSC and CD16/CD56 dot plots of fresh human blood. From the lymphocyte singlets, the NK cells subpopulations were analyzed based on the differentiated expression of surface markers and classified as follows: CD16^-CD56^+/++/CD16⁺CD56⁺⁺/CD16⁺CD56⁺/CD16⁺⁺CD56⁻. By examining the CD56 versus CD16 flow cytometry dot plots, we found four distinct NK sub-populations. These NK subtypes correspond to different NK phenotypes from secretory to cytolytic ones. There was no difference between total NK percentage of different disease forms. However, the total numbers decreased significantly both in survivors and non-survivors. Additionally, for the CD16^-CD56^+/++ phenotype, we observed different patterns, gradually decreasing in survivors and gradually increasing in those with fatal outcomes. Despite no difference in the proportion of the CD16⁻CD56⁺⁺ NK cells in survivors vs. non–survivors, the main cytokine producers gradually decline during the study period in the survival group, underling the importance of adequate IFN production during the early stage of SARS-CoV-2 infection. Persistency in the circulation of CD56⁺⁺ NK cells may have prognostic value in patients, with a fatal outcome. Total NK cells and the CD16⁺CD56⁺ NK subtypes exhibit significant decreasing trends across the moments for both survivors and non-survivors.

Low Serum Vitamin D in COVID-19 Patients Is Not Related to Inflammatory Markers and Patients' Outcomes-A Single-Center Experience and a Brief Review of the Literature

The aim of the study was to evaluate the vitamin D status in hospitalized COVID-19 patients and the correlation with C reactive protein (CRP), ferritin, fibrinogen, and peripheral blood leukocytes, as well as inflammatory derived indices. A prospective study was performed on 203 COVID-19 hospitalized patients, classified by disease severity. Blood was collected after admission, and inflammatory biomarkers and vitamin D status were assessed using routine laboratory procedures. No significant correlation was found between vitamin D serum levels and disease severity stratified by different age groups. However, the highest vitamin D levels were found in patients with mild disease: median 29.39 (IQR 12.12-44.02) ng/mL, while for moderate and severe forms the serum levels were significantly lower: median 15.10 (IQR 9.56-24.11) ng/mL for moderate, and 18.86 (IQR 12.50-27.88) ng/mL for severe; p = 0.009. Patients with no comorbidities showed a significantly higher level of vitamin D median 24.72 (IQR 16.05-31.52) ng/mL compared to subjects with at least one comorbidity: median 16.02 (IQR 9.81-25.22) ng/mL, p = 0.004. We did not find an association between vitamin D levels and inflammatory biomarkers except for significantly lower vitamin D levels in moderate and severe COVID-19 compared to mild disease forms.

Exploring the Utility of NK Cells in COVID-19

Coronavirus disease 2019 (COVID-19) can manifest as acute respiratory distress syndrome and is associated with substantial morbidity and mortality. Extensive data now indicate that immune responses to SARS-CoV-2 infection determine the COVID-19 disease course. A wide range of immunomodulatory agents have been tested for the treatment of COVID-19. Natural killer (NK) cells play an important role in antiviral innate immunity, and anti-SARS-CoV-2 activity and antifibrotic activity are particularly critical for COVID-19 control. Notably, SARS-CoV-2 clearance rate, antibody response, and disease progression in COVID-19 correlate with NK cell status, and NK cell dysfunction is linked with increased SARS-CoV-2 susceptibility. Thus, NK cells function as the key element in the switch from effective to harmful immune responses in COVID-19. However, dysregulation of NK cells has been observed in COVID-19 patients, exhibiting depletion and dysfunction, which correlate with COVID-19 severity; this dysregulation perhaps contributes to disease progression. Given these findings, NK-cell-based therapies with anti-SARS-CoV-2 activity, antifibrotic activity, and strong safety profiles for cancers may encourage the rapid application of functional NK cells as a potential therapeutic strategy to eliminate SARS-CoV-2-infected cells at an early stage, facilitate immune–immune cell interactions, and favor inflammatory processes that prevent and/or reverse over-inflammation and inhibit fibrosis progression, thereby helping in the fight against COVID-19. However, our understanding of the role of NK cells in COVID-19 remains incomplete, and further research on the involvement of NK cells in the pathogenesis of COVID-19 is needed. The rationale of NK-cell-based therapies for COVID-19 has to be based on the timing of therapeutic interventions and disease severity, which may be determined by the balance between beneficial antiviral and potential detrimental pathologic actions. NK cells would be more effective early in SARS-CoV-2 infection and prevent the progression of COVID-19. Immunomodulation by NK cells towards regulatory functions could be useful as an adjunct therapy to prevent the progression of COVID-19.

Potential Therapeutic Targets and Vaccine Development for SARS-CoV-2/COVID-19 Pandemic Management: A Review on the Recent Update

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly pathogenic novel virus that has caused a massive pandemic called coronavirus disease 2019 (COVID-19) worldwide. Wuhan, a city in China became the epicenter of the outbreak of COVID-19 in December 2019. The disease was declared a pandemic globally by the World Health Organization (WHO) on 11 March 2020. SARS-CoV-2 is a beta CoV of the Coronaviridae family which usually causes respiratory symptoms that resemble common cold. Multiple countries have experienced multiple waves of the disease and scientific experts are consistently working to find answers to several unresolved questions, with the aim to find the most suitable ways to contain the virus. Furthermore, potential therapeutic strategies and vaccine development for COVID-19 management are also considered. Currently, substantial efforts have been made to develop successful and safe treatments and SARS-CoV-2 vaccines. Some vaccines, such as inactivated vaccines, nucleic acid-based, and vector-based vaccines, have entered phase 3 clinical trials. Additionally, diverse small molecule drugs, peptides and antibodies are being developed to treat COVID-19. We present here an overview of the virus interaction with the host and environment and anti-CoV therapeutic strategies; including vaccines and other methodologies, designed for prophylaxis and treatment of SARS-CoV-2 infection with the hope that this integrative analysis could help develop novel therapeutic approaches against COVID-19.