Short Communication: S100A8 and S100A9, Biomarkers of SARS-CoV-2 Infection and Other Diseases, Suppress HIV Replication in Primary Macrophages.

S100A8 and S100A9 are members of the Alarmin family; these proteins are abundantly expressed in neutrophils, form a heterodimer complex, and are secreted in plasma on pathogen infection or acute inflammatory diseases. Recently, both proteins were identified as novel biomarkers of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and were shown to play key roles in inducing an aggressive inflammatory response by mediating the release of large amounts of pro-inflammatory cytokines, called the "cytokine storm." Although co-infection with SARS-CoV-2 in people living with HIV-1 may result in an immunocompromised status, the role of the S100A8/A9 complex in HIV-1 replication in primary T cells and macrophages is still unclear. Here, we evaluated the roles of the proteins in HIV replication to elucidate their functions. We found that the complex had no impact on virus replication in both cell types; however, the subunits of S100A8 and S100A9 inhibit HIV in macrophages. These findings provide important insights into the regulation of HIV viral loads during SARS-CoV-2 co-infection.

Lipocalin-2, S100A8/A9, and cystatin C: Potential predictive biomarkers of cardiovascular complications in COVID-19.

Severe coronavirus (SARS-COV-2) infection often leads to systemic inflammation accompanied by cardiovascular complications including venous thromboembolism (VTE). However, it is largely undefined if inflammatory markers such as lipocalin-2 (LNC2), calprotectin (S100A8/A9), and cystatin C (CST3), previously linked with VTE, play roles in cardiovascular complications and advancement of COVID-19 severity. To investigate the same, hospitalized moderate and severe (presented pneumonia and required intensive care) COVID-19 patients were recruited. The levels of plasma LNC2, S100A8/A9, CST3, myoglobin, and cardiac Troponin I (cTnI) were assessed through enzyme-linked immunosorbent assay (ELISA). The investigation revealed a significantly upregulated level of plasma LNC2 at the moderate stage of SARS-CoV-2 infection. In contrast, the levels of S100A8/A9 and CST3 in moderate patients were comparable to healthy controls; however, a profound induction was observed only in severe COVID-19 patients. The tissue injury marker myoglobin was unchanged in moderate patients; however, a significantly elevated level was observed in the critically ill COVID-19 patients. In contrast, cTnI level was unchanged both in moderate and severe patients. Analysis revealed a positive correlation between the levels of S100A8/A9 and CST3 with myoglobin in COVID-19. In silico analysis predicted interactions of S100A8/A9 with toll-like receptor 4 (TLR-4), MyD88 LY96, and LCN2 with several other inflammatory mediators including MMP2, MMP9, TIMP1, and interleukins (IL-6, IL-17A, and IL-10). In summary, early induction of LCN2 likely plays a role in advancing the COVID-19 severity. A positive correlation of S100A8/A9 and CST3 with myoglobin suggests that these proteins may serve as predictive biomarkers for thromboembolism and tissue injury in COVID-19.

Hematopoietic progenitor cell liabilities and alarmins S100A8/A9-related inflammaging associate with frailty and predict poor cardiovascular outcomes in older adults.

Frailty affects the physical, cognitive, and social domains exposing older adults to an increased risk of cardiovascular disease and death. The mechanisms linking frailty and cardiovascular outcomes are mostly unknown. Here, we studied the association of abundance (flow cytometry) and gene expression profile (RNAseq) of stem/progenitor cells (HSPCs) and molecular markers of inflammaging (ELISA) with the cardiorespiratory phenotype and prospective adverse events of individuals classified according to levels of frailty. Two cohorts of older adults were enrolled in the study. In a cohort of pre-frail 35 individuals (average age: 75 years), a physical frailty score above the median identified subjects with initial alterations in cardiorespiratory function. RNA sequencing revealed S100A8/A9 upregulation in HSPCs from the bone marrow (>10-fold) and peripheral blood (>200-fold) of individuals with greater physical frailty. Moreover higher frailty was associated with increased alarmins S100A8/A9 and inflammatory cytokines in peripheral blood. We then studied a cohort of 104 more frail individuals (average age: 81 years) with multidomain health deficits. Reduced levels of circulating HSPCs and increased S100A8/A9 concentrations were independently associated with the frailty index. Remarkably, low HSPCs and high S100A8/A9 simultaneously predicted major adverse cardiovascular events at 1-year follow-up after adjustment for age and frailty index. In conclusion, inflammaging characterized by alarmin and pro-inflammatory cytokines in pre-frail individuals is mirrored by the pauperization of HSPCs in frail older people with comorbidities. S100A8/A9 is upregulated within HSPCs, identifying a phenotype that associates with poor cardiovascular outcomes.

Comparative transcriptome analyses reveal genes associated with SARS-CoV-2 infection of human lung epithelial cells.

During 2020, understanding the molecular mechanism of SARS-CoV-2 infection (the cause of COVID-19) became a scientific priority due to the devastating effects of the COVID-19. Many researchers have studied the effect of this viral infection on lung epithelial transcriptomes and deposited data in public repositories. Comprehensive analysis of such data could pave the way for development of efficient vaccines and effective drugs. In the current study, we obtained high-throughput gene expression data associated with human lung epithelial cells infected with respiratory viruses such as SARS-CoV-2, SARS, H1N1, avian influenza, rhinovirus and Dhori, then performed comparative transcriptome analysis to identify SARS-CoV-2 exclusive genes. The analysis yielded seven SARS-CoV-2 specific genes including CSF2 [GM-CSF] (colony-stimulating factor 2) and calcium-binding proteins (such as S100A8 and S100A9), which are known to be involved in respiratory diseases. The analyses showed that genes involved in inflammation are commonly altered by infection of SARS-CoV-2 and influenza viruses. Furthermore, results of protein-protein interaction analyses were consistent with a functional role of CSF2 and S100A9 in COVID-19 disease. In conclusion, our analysis revealed cellular genes associated with SARS-CoV-2 infection of the human lung epithelium; these are potential therapeutic targets.