Decrease in Dengue virus-2 infection and reduction of cytokine/chemokine production by Uncaria guianensis in human hepatocyte cell line Huh-7

BACKGROUND

Dengue fever may present hemorrhages and cavitary effusions as result of exacerbated immune responses. We investigated hydro-alcoholic extracts from leaves (UGL) and bark (UGB) of the medicinal species Uncaria guinanensis with respect to antiviral effects in Dengue virus (DENV) infection and in immunological parameters associated with in vivo physiopathological features.

METHODS

Chemical profiles from UGB or UGL were compared in thin layer chromatography and ¹H nuclear magnetic resonance using flavonoid compounds and a pentacyclic oxindole alkaloid-enriched fraction as references. DENV-2-infected hepatocytes (Huh-7) were treated with extracts. Cell viability, DENV antigens and immunological factors were detected by enzyme-linked immunosorbent assay (ELISA) or flow cytometry.

FINDINGS

The UGL mainly differed from UGB by selectively containing the flavonoid kaempferitrin. UGB and UGL improved hepatocyte viability. Both extracts reduced intracellular viral antigen and inhibited the secretion of viral non-structural protein (NS1), which is indicative of viral replication. Reduction in secretion of macrophage migration inhibitory factor was achieved by UGB, of interleukin-6 by UGL, and of interleukin-8 by both UGB and UGL. MAIN

CONCLUSIONS

The U. guianensis extracts presented, antiviral and immunomodulatory effects for DENV and possibly a hepatocyte-protective activity. Further studies may be performed to consider these products as potential candidates for the development of an herbal product for the future treatment of dengue.

Association of rs1285933 single nucleotide polymorphism in CLEC5A gene with dengue severity and its functional effects

Outbreaks of the Zika, dengue, and chikungunya viruses, especially in the Americas, pose a global threat due to their rapid spread and difficulty controlling the vector. Extreme phenotypes are often observed, from asymptomatic to severe clinical manifestations, which are well-studied in dengue. Host variations are also important contributors to disease outcomes, and many case-control studies have associated single nucleotide polymorphisms (SNPs) with severe dengue. Here, we found that the TC genotype and T-carriers for SNP rs1285933 in the C-type lectin superfamily member 5 (CLEC5A) gene was associated with severe dengue in a Northern Brazilian population (OR=2.75 and p-value=0.01, OR=2.11 and p-value=0.04, respectively). We also tested the functional effect of the CLEC5A protein and found that it is upregulated on the surface of human monocytes after in vitro dengue infection. CLEC5A was correlated with viral load inside the monocytes (Spearman r=0.55, p=0.008) and TNF production in culture supernatants (Spearman r=0.72, p=0.03). Analysis of mRNA in blood samples from DENV4-infected patients exhibiting mild symptoms showed that CLEC5A mRNA expression is correlated with TNF (r=0.67, p=0.0001) and other immune mediators. Monocytes from rs1285933 TT/TC individuals showed lower CLEC5A expression compared to CC genotypes. However, in these cells, CLEC5A was not correlated with TNF production. In summary, we confirmed that CLEC5A is genetically associated with dengue severity outcome, playing a central role during the immune response triggered by a dengue viral infection, and rs1285933 is a relevant SNP that is able to regulate signaling pathways after interactions between the dengue virus and CLEC5A receptors.

Antiviral and Immunomodulatory Effects of Norantea brasiliensis Choisy on Dengue Virus-2

BACKGROUND/AIMS

Severe dengue fever is a result of exacerbated immune responses and no specific treatments are available. We evaluated the antiviral and immunomodulatory effects of Norantea brasiliensis Choisy.

METHODS

Human adherent monocytes infected in vitro with dengue virus (DENV)-2 were incubated with the crude ethanol extract from leaves (NB1) or 3 derived fractions: dichloromethane (NB3), ethyl acetate (NB5), and butanolic (NB6) partitions. The antiviral and immunomodulatory activities were determined by intracellular detection of DENV antigen within monocytes and by secreted NS1 viral protein and cytokines.

RESULTS

The crude extract alone exhibited both antiviral activities (intracellular and secreted antigens) and all fractions derived from this extract modulated NS1 production. Regarding the immunomodulatory effect, among the secreted factors, TNF-α was inhibited by NB3 and NB6; IL-6 was inhibited by NB1, NB3, and NB6; IL-10 by NB1 and NB3; and IFN-α by NB6. The crude extract (NB1) presented the best antiviral effect, whereas the dichloromethane fraction (NB3) presented an immunomodulatory effect in the inflammatory and anti-inflammatory cytokines.

CONCLUSION

During in vitro DENV infection, N. brasiliensis Choisy exerts both antiviral and immunomodulatory effects that are likely associated, considering that less viral load may lead to less immunostimulation.