Increased levels of pentraxins protein and cytokines bear good association in patients with severe dengue infection

Platelet derived exosomes disrupt endothelial cell monolayer integrity and enhance vascular inflammation in dengue patients

Background

Thrombocytopenia is the most notable phenomenon in dengue. Activation status of platelets and interaction of platelets with endothelium contribute towards dengue disease pathogenesis. Platelets are the major cell types known to release extracellular vesicles, especially exosomes in circulation. However, the role of platelet derived exosomes (PLT-EXOs) in endothelial dysfunction during dengue infection remains unknown.

Methods

In this study, we recruited 28 healthy subjects and 69 dengue patients categorized as WS- (n=31), WS+ (n=29) and SD (n=9). Platelets were isolated from platelet rich plasma of dengue patients and their activation was assessed by flow cytometry. PLT-EXOs were isolated by ultracentrifugation method. Western blot analyses were performed to characterize the exosomes. Exosome uptake experiment was carried out to see the internalization of exosomes inside endothelial cells (HUVECs). To observe the effect of exosomes on endothelial cells, exosomes were added on HUVECs and expression of adherens and tight junctional proteins were examined by immunofluorescence assay and western blot. Expression levels of vascular injury markers were measured in the culture supernatants of Exosome-HUVEC coculture and sera of dengue patients by MSD-multiplex assay.

Results

As compared to healthy subjects, CD41/CD61 expression was significantly reduced (p<0.0001) and CD62p expression was significantly increased (p<0.0001) on platelets in dengue patients. PLT-EXOs isolated from the dengue patients showed higher expression of CD63 and CD9 proteins than the healthy subjects. With in-vitro immunofluorescence assays, we illustrated the internalization of PLT-EXOs by the HUVECs and observed disruption of endothelial cell monolayer integrity in the presence of PLT-EXOs from WS+ and SD patients. Furthermore, the significant reduction in the expressions of ZO-2, VE-Cadherin and CD31 in endothelial cells following exposure to PLT-EXOs from the dengue patients provide direct evidence of PLT-EXOs mediated vascular permeability. PLT-EXOs stimulated the release of inflammatory markers CRP, SAA, sVCAM-1 and sICAM-1 in the supernatants of HUVEC cells. Importantly, significantly higher levels of CRP, sVCAM-1 and sICAM-1 in the sera of severe than mild dengue patients (p<0.0001) suggest their role in disease severity.

Conclusions

In summary, our data suggest that PLT-EXOs promote vascular leakage via release of proinflammatory mediators and compromise vascular barrier integrity in dengue patients.

Serum ferritin level as a prognostic biomarker for predicting dengue disease severity: A systematic review and meta-analysis

Serum ferritin levels serves as biomarkers in many inflammatory and infectious diseases. This current systematic review and meta-analysis evaluated whether serum ferritin levels are associated with severe dengue and its utility as a biomarker of disease severity. Literature searches were conducted in PubMed, Scopus, ScienceDirect, the Cochrane library, and Google Scholar. A total of 18 studies examining the serum ferritin levels in dengue cases in the context of disease severity (nine studies having dengue classification as non-severe vs. severe dengue cases, and nine studies having dengue classification as dengue without warning signs (DwoWS), dengue with warning signs (DwWS), and severe dengue cases) were included and the quality of the studies was assessed using the Quality in Prognostic Factor Studies tool. The meta-analysis was performed using STATA software to calculate the effect size as a standardized mean difference (SMD) or Hedges 'g' for the continuous outcome. Higher serum ferritin levels were found in severe dengue cases compared to non-severe cases [SMD (Hedges 'g') 4.05 (95% C.I. 2.09-6.00), (I2  = 98.8%)]. In the second group, DwWS cases showed high serum ferritin levels compared to DwoWS [SMD 2.01 (95% C.I. 0.92-3.10), (I2  = 97.89%)], and severe dengue cases showed higher levels of serum ferritin compared to DwWS [SMD 2.66 (95% C.I. 1.72-4.48), (I2  = 98.78%)] and DwoWS cases [SMD 6.65 (95% C.I. 1.72-11.59), (I2  = 99.78%]. Subgroup analysis for the country of study (India vs. others), ferritin testing methods, and ferritin measurement day revealed testing method as a significant contributor to heterogeneity. To conclude, the present study suggests serum ferritin as a prognostic marker for dengue disease severity. Multi-centric studies involving a large number of dengue patients with a uniform case definition accounting for all the confounding variables might help in determining a universal cut-off value to discriminate between non-severe and severe dengue.

Elevated Interleukin-37 Associated with Dengue Viral Load in Patients with Dengue Fever

Dengue remains a public health issue worldwide. Similar to chronic infectious diseases, stimulation of cytokine production is not enough to drive immune effector cells for effective virus clearance. One possible mechanism is the virus induces a large number of negative stimulatory cytokines inhibiting immune response. Interleukin 37 (IL-37) plays a crucial regulatory role in infection and immunity, inhibits innate and adaptive immunity as an anti-inflammatory cytokine by inhibiting proinflammatory mediators and pathways. To date, there are few studies reporting correlations between dengue fever (DF) and IL-37. In this study we found that the serum IL-37b and IL-37b-producing monocytes in patients were significantly increased in DF patients. A majority of the IL-37b produced by DF patients was produced by monocytes, not lymphocytes. Increased levels of IL-6, IL-10, and IFN-α were also found in DF patients. However, we failed to detect IL-1β, IL-17A and TNF-α in plasma, because of off-target. In our study, there was no relation between IL-6, IL-10, and IFN-α expressions and IL-37b in serum (P > 0.05). The IL-37b-producing monocytes were negatively correlated with the level of IFN-α in serum and platelet count, and positively correlated with lymphocytes percentage (P < 0.05, respectively). Additionally, serum DENV nonstructural protein 1 levels were positively correlated with monocytes percentages (P < 0.05). Our data represents findings for IL-37b expression and its potential mechanisms in DF patients' immune response.