Dengue Virus Patients Research Articles

Integrative bulk and single-cell transcriptome profiling analysis reveals IFI27 as a novel interferon-stimulated gene in dengue.

The dengue virus (DENV) is a public health threat to humans. Increased vascular permeability, coagulopathy, and hemorrhagic diathesis are the pathophysiological hallmarks of severe dengue. However, although the interferon (IFN)-mediated innate immune response forms the backbone of cell-autonomous defense against pathogens, the exact IFN-stimulated genes (ISGs) involved in DENV infection remain to be determined. The present study collected transcriptomic data sets of peripheral blood mononuclear cells from DENV patients and healthy volunteers from public data repositories. Also, lentivirus and plasmid were used to overexpress and knockdown IFI27. Initially, differentially expressed genes were filtered, and gene set enrichment analysis (GSEA) was performed to assess related pathways. Subsequently, the least absolute shrinkage and selection operator regression and support vector machine-recursive feature elimination algorithms were used to screen crucial genes. The receiver operating characteristic curve analysis was then employed to test diagnostic efficacy. Next, CIBERSORT was used to analyze immune infiltration in 22 immune cell subsets. Additionally, to dissect high-resolution molecular phenotypes directly from individual cells and the cellular interactions between immune cell subpopulations, single-cell RNA sequencing (scRNA-seq) was performed. We found that the IFN-stimulated gene IFN-α-inducible protein 27 (IFI27) was highly expressed in dengue patients by leveraging bioinformatics analysis and machine learning algorithms. This finding was further validated in two independent published databases. In addition, IFI27 overexpression positively regulated DENV-2 infection, whereas IFI27 knockdown has the opposite effect. Consistently, scRNA-seq analysis supported this conclusion, along with further dissection of increased IFI27 expression mainly concentrated in monocytes and plasmacytoid dendritic cells. We also demonstrated that IFI27 inhibited dengue infection. Moreover, IFI27 was positively correlated with monocytes, M1 macrophages, activated dendritic cells, plasma cells, and resting mast cells and negatively correlated with CD8 T cells, γδ T cells, and naïve B cells. GSEA revealed that IFI27 was primarily enriched in the innate immune response, regulation of the viral life cycle, and JAK-STAT signaling pathway. Notably, the interactions between LGALS9 and its receptor CD47 were markedly increased in dengue patients compared to healthy controls, based on cell-cell communication analysis. Our findings reveal, for the first time, that IFI27 is a key ISG in DENV infection. Given that the innate immune system plays a significant role in antagonizing DENV invasion, while ISGs are the ultimate antiviral effectors, IFI27 may serve as a potential diagnostic marker and therapeutic target in dengue, although further validation is warranted.

Re-mining serum proteomics data reveals extensive post-translational modifications upon Zika and dengue infection.

Zika virus (ZIKV) and dengue virus (DENV) are two closely related flaviviruses with similar symptoms. However, due to the implications of ZIKV infections for pregnancy outcomes, understanding differences in their molecular impact on the host is of high interest. Viral infections change the host proteome, including post-translational modifications. As modifications are diverse and of low abundance, they typically require additional sample processing which is not feasible for large cohort studies. Therefore, we tested the potential of next-generation proteomics data in its ability to prioritize specific modifications for later analysis. We re-mined published mass spectra from 122 serum samples from ZIKV and DENV patients for the presence of phosphorylated, methylated, oxidized, glycosylated/glycated, sulfated, and carboxylated peptides. We identified 246 modified peptides with significantly differential abundance in ZIKV and DENV patients. Amongst these, methionine-oxidized peptides from apolipoproteins and glycosylated peptides from immunoglobulin proteins were more abundant in ZIKV patient serum and generate hypotheses on the potential roles of the modification in the infection. The results demonstrate how data-independent acquisition techniques can help prioritize future analyses of peptide modifications.

Single-cell temporal analysis of natural dengue infection reveals skin-homing lymphocyte expansion one day before defervescence

SummaryEffective clinical management of acute dengue virus (DENV) infection relies on the timing of suitable treatments during the disease progression. We analyzed single-cell transcriptomic profiles of the peripheral blood mononuclear cell samples from two DENV patients, collected daily during acute phase and also at convalescence. Key immune cell types demonstrated different dynamic responses over the course of the infection. On the day before defervescence (Day −1), we observed the peak expression of several prominent genes in the adaptive immunological pathways. We also characterized unique effector T cell clusters that expressed skin-homing signature genes at Day −1, whereas upregulation of skin and gut homing genes was also observed in plasma cells and plasmablasts during the febrile period. This work provides an overview of unique molecular dynamics that signify the entry of the critical phase, and the findings could improve the patient management of DENV infection.

NS1 glycoprotein detection in serum and urine as an electrochemical screening immunosensor for dengue and Zika virus.

The incidence of infection by the dengue virus (DENV) has grown dramatically, reaching 128 countries in tropical and subtropical regions worldwide, with a pattern of hyper-endemicity. DENV is a mosquito-borne disease having four serotypes, one or two circulating in epidemic outbreaks. The diagnosis of DENV is challenging mainly due to the circulation of new viruses with remarkable similarities, such as Zika (ZIKV) that may cause fetal microcephaly. DENV affects 390 million people per year, but these numbers may be higher due to the underreported and misclassified cases. Recently, the NS1 nonstructural protein has been described in serum and urine of DENV and ZIKV patients, suggesting its use as a biomarker for screening since a negative NS1 sample confirms the absence of these infections. Herein, a label-free immunosensor comprising an assembled nanostructured thin film of carbon nanotube-ethylenediamine is described. The advantage of in situ electrosynthesis of polymer film is to allow major control of thickness and conductivity, in addition to designing the reactive groups for functionalization. A quartz crystal microbalance system was used to estimate the thickness of the polymeric film obtained. The anti-NS1 monoclonal antibodies were immobilized to carbon nanotubes by covalent linkage, permitting a high stability during measurements. Analytical responses to NS1 were obtained by differential pulse voltammetry (DPV), showing a linear range from 20 to 800ngmL-1 and reproducibility of 3.0%, with a limit of detection (LOD) of 6.8ngmL- 1. This immunosensor was capable of detecting ZIKV and DENV NS1 in spiked urine and real serum in a clinical range.Graphical abstract.

Decreased Type I Interferon Production by Plasmacytoid Dendritic Cells Contributes to Severe Dengue.

The clinical presentation of dengue virus (DENV) infection is variable. Severe complications mainly result from exacerbated immune responses. Type I interferons (IFN-I) are important in antiviral responses and form a crucial link between innate and adaptive immunity. Their contribution to host defense during DENV infection remains under-studied, as direct quantification of IFN-I is challenging. We combined ultra-sensitive single-molecule array (Simoa) digital ELISA with IFN-I gene expression to elucidate the role of IFN-I in a well-characterized cohort of hospitalized Cambodian children undergoing acute DENV infection. Higher concentrations of type I IFN proteins were observed in blood of DENV patients, compared to healthy donors, and correlated with viral load. Stratifying patients for disease severity, we found a decreased expression of IFN-I in patients with a more severe clinical outcome, such as dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). This was seen in parallel to a correlation between low IFNα protein concentrations and decreased platelet counts. Type I IFNs concentrations were correlated to frequencies of plasmacytoid DCs, not DENV-infected myloid DCs and correlated inversely with neutralizing anti-DENV antibody titers. Hence, type I IFN produced in the acute phase of infection is associated with less severe outcome of dengue disease.

Surveillance of dengue virus in individual Aedes aegypti mosquitoes collected concurrently with suspected human cases in Tarlac City, Philippines

BackgroundVector control measures are critical for the prevention and reduction of dengue virus (DENV) transmission. Effective vector control is reliant not only on knowledge of mosquito abundance, but also on the timely and accurate detection of mosquito-borne infection. Mosquito-based virus surveillance programs typically rely on pool-based mosquito testing, although whether individual-based mosquito testing is a feasible alternative to this has not been widely studied. Applying an individual-based mosquito testing approach, we conducted a 1-month surveillance study of DENV in adult Aedes aegypti mosquitoes in homes of suspected dengue patients during the 2015 peak dengue season in Tarlac City, Philippines to more accurately assess the mosquito infection rate and identify the DENV serotypes and genotypes concurrently co-circulating in mosquitoes and patients there.MethodsWe performed a one-step multiplex real-time reverse transcription-polymerase chain reaction (RT-PCR) assay for the simultaneous detection and serotyping of DENV in patients and individual female Ae. aegypti mosquitoes. Additionally, we performed sequencing and phylogenetic analyses to further characterize the detected DENV serotypes in mosquitoes and patients at the genotype level.ResultsWe collected a total of 583 adult Ae. aegypti mosquitoes, of which we individually tested 359 female mosquitoes for the presence of DENV. Ten (2.8%) of the 359 female mosquitoes were positive for the presence of DENV. We detected DENV-1, DENV-2, and DENV-4 in the field-collected mosquitoes, which was consistent with the serotypes concurrently found in infected patients. Sequencing and phylogenetic analyses of the detected DENV serotypes based on the partial sequence of the evelope (E) gene revealed three genotypes concurrently present in the sampled mosquitoes and patients during the study period, namely DENV-1 genotype IV, DENV-2 Cosmopolitan genotype, and DENV-4 genotype II.ConclusionsWe demonstrated the utility of a one-step multiplex real-time RT-PCR assay for the individual-based DENV surveillance of mosquitoes. Our findings reinforce the importance of detecting and monitoring virus activity in local mosquito populations, which are critical for dengue prevention and control.

Zika Virus Disease Comparing Children and Adults in a Dengue-Endemic Setting

.Acute Zika virus (ZIKV) infection may mimic dengue virus (DENV) infection. We aimed to study the clinical difference of ZIKV disease among suspected non-severe DENV patients comparing children and adults. Patients with acute illness suspected of DENV disease plus no evidence of plasma leakage at the Bamrasnaradura Infectious Diseases Institute, Nonthaburi, Thailand, were enrolled from December 2016 to September 2018. Clinical data including DENV rapid diagnostic test (RDT) results were collected. Zika virus diagnosis was confirmed by real-time reverse transcription PCR on urine. Of 291 (180 pediatric and 111 adult) cases enrolled, 27 (10 pediatric and 17 adult) confirmed ZIKV cases were found. Rash was more frequent among pediatric ZIKV than pediatric non-ZIKV cases (100% versus 60%, P = 0.01). Rash, arthralgia, and conjunctivitis were more frequent among adult ZIKV than adult non-ZIKV cases (100% versus 29.8%, 64.7% versus 26.6%, 52.9% versus 9.7%, all P < 0.01, respectively). The median (interquartile range [IQR]) duration of rash was 4.5 (3.0, 7.25) days and 6.0 (4.5, 7.0) days in pediatric and adults ZIKV cases, respectively. Pediatric ZIKV cases had more fever (100% versus 58.5%, P = 0.03) but less arthralgia (20% versus 64.7%, P = 0.04) and less conjunctivitis (10% versus 52.9%, P = 0.04) than adult ZIKV cases. No ZIKV cases with DENV RDTs performed around day 3 of illness were positive for dengue nonstructural protein 1 (NS1) antigen. In dengue-endemic settings, rash and fever in children, and rash, arthralgia, and conjunctivitis in adults, particularly if rash persists for ≥ 3 days, plus negative dengue NS1 Ag during early febrile phase should prompt ZIKV diagnostic testing.

Molecular study of 2019 dengue fever outbreaks in Nepal.

Dengue cases have been continuously reported in Nepal, including some large outbreaks, since its first introduction in 2004. The disease is now expanding towards newer locations above 1400 m high, especially the country's capital city, Kathmandu. In 2019, >14,000 dengue cases including six deaths were reported. This study was aimed at the detection and molecular characterization of dengue virus (DENV) in dengue patients. A total of 451 patients were enrolled in this study. Demographic, clinical and laboratory information was collected from dengue patients. Dengue infection was confirmed by antibody/antigen detection assays followed by RT-PCR analysis. The DENV patients showed fever, body ache, headache, myalgia, retro-orbital pain and arthralgia. The platelets were decreased, serum liver enzymes were increased and leucopenia was seen. Out of 195 patients, 111 (57.0%) were positive for DENV RNA by consensus PCR. We found DENV-2, 70 (63.1%) as the predominant serotype responsible for the 2019 outbreak, while DENV-3 was detected in two patients. Our findings suggest that DENV-2 was the major serotype causing the 2019 massive outbreak in Nepal. This information will help in disease control programs to understand the molecular epidemiology and its changing trend.

Clinical, Virological, and Immunological Profiles of DENV, ZIKV, and/or CHIKV-Infected Brazilian Patients

Background: Arboviruses co-circulating within a population that are transmitted by the same vector have the potential to cause coinfections. Coinfections with dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) have been occurring in Brazil, but it is not well-understood how human responses vary during mono- or coinfections and whether they play different roles in pathogenesis. Methods: We investigated the clinical, virological, and immunological status during patients’ acute infections, focusing on the CCL/CXC chemokines, proinflammatory, as well as anti-inflammatory cytokines levels quantified by ELISAs. Viral load was determined by qRT-PCR in serum samples from 116 acute DENV, ZIKV, CHIKV, DENV/ZIKV, and CHIKV/ZIKV-infected adult patients from Brazil. Results: Most of the acute patients displayed fever, headache, prostration, and myalgia, regardless of the type of arbovirus infection. Zika viral load was higher in CHIKV/ZIKV coinfected patients compared with ZIKV or DENV/ZIKV infections. All infected individuals presented increased concentrations of C-X-C motif chemokine ligand 10/interferon protein-10 (CXCL10/IP-10), C-C motif chemokine ligand 2/monocyte chemoattractant protein-1 (CCL2/MCP-1), and tumor necrosis factor alpha (TNF-α) compared to healthy donors. Interestingly, the ZIKV group separated from CHIKV/ZIKV due to higher levels of interleukin-10 (IL-10) and lower levels of TNF-α. While DENV/ZIKV differentiated from CHIKV due to their higher levels of CCL2/MCP-1, in CHIKV- and CHIKV/ZIKV-infected patients, levels of CXC10/IP-10, CCL2/MCP-1, and migration inhibitory factor (MIF) were associated with CHIKV viral load. By contrast, in DENV/ZIKV- and CHIKV/ZIKV-infected patients, levels of CXCL10/IP-10, CCL2/MCP-1, and TNF-α showed a significant inverse correlation with ZIKV viral load. Conclusions: From all the circulating mediators measured, we detected differences of IL-10, TNF-α, and CCL2/MCP-1 between arbovirus groups. We hypothesize that CXC10/IP-10, CCL2/MCP-1, and MIF in the CHIKV-infected group could regulate the CHIKV viral load, while CXC10/IP-10, CCL2/MCP-1, and TNF-α in DENV/ZIKV, and CHIKV/ZIKV groups, could regulate ZIKV viral load.

Neopterin levels and Kyn/Trp ratios were significantly increased in dengue virus patients and subsequently decreased after recovery

ObjectivesDuring dengue fever, a pronounced gamma-interferon immune response produces neopterin and promotes tryptophan degradation by the enzyme indoleamine-2,3-dioxygenase 1 (IDO-1). Activated IDO-1 is indicated by an increased kynurenine to tryptophan ratio (Kyn/Trp) in patients. MethodsPlasma levels of neopterin, kynurenine, and tryptophan were measured in 72 hospitalized dengue virus (DENV) patients and 100 healthy individuals. Plasma levels of neopterin, kynurenine, and tryptophan were also measured prospectively in a second cohort of 13 DENV patients; on the day of hospitalization, on day 2–3 at discharge, and 7–10 days after discharge. DENV RNA positivity was determined by qualitative and quantitative methodologies. ResultsDENV RNA-positive patients presented significantly higher levels of neopterin (mean 36.5nmol/l) and Kyn/Trp ratios (mean 102μmol/mmol) compared to DENV RNA-negative individuals. A significant correlation between neopterin levels and Kyn/Trp ratios was observed in both DENV RNA-positive (Spearman’s rho=0.37, p< 0.01) and DENV RNA-negative (Spearman’s rho=0.89, p<0.001) patients. Kyn/Trp ratios were negatively correlated with platelet counts (Spearman’s rho=−0.43, p<0.01) and positively correlated with liver enzymes: AST (Spearman’s rho=0.68, p<0.01) and ALT (Spearman’s rho=0.51, p<0.05). In addition, the follow-up data presented a significant decrease in neopterin levels and Kyn/Trp ratios within 10 days after hospital entry. ConclusionsNeopterin levels and Kyn/Trp ratios were significantly increased in DENV patients and subsequently decreased after recovery.

Genotypes of the dengue virus in patients with dengue infection from Sabah, Malaysia

Dengue fever is an arthropod-borne viral disease caused by the Dengue virus (genus Falvivirus, family Flaviviridae). It has rapidly spread all over the world affecting approximately 400 million people annually. Human dengue infection is caused by four types of closely related viruses (also called serotypes) namely DENV-1, DENV-2, DENV-3, and DENV-4, all of which can be all found in Sabah, Malaysia. Each serotype can then be divided into unique groups based on its genotypes. In Malaysia, dengue has been reported as the most prevalent disease of the country with a ratio of 328.3 cases per 100,000 populations. Exacerbating this further, it was also recently reported in 2017 of the emergence of a newly identified Asian lineage dengue virus i.e. type 3 genotype II (D3GII) in Malaysia. We have aimed, through this study, to examine the serotypes and the genotypes of dengue virus circulating in Sabah. This study was conducted for a period of 8 months i.e. from January to August 2017. A total of 52 NS1 (50.9% were males and 49.1% were females) positive dengue patient serum samples were genotyped. Viral RNA was extracted from serum using QIAamp viral RNA mini kit and DNA sequencing was done on Applied Biosystems 3730xl DNA analyzer. The results showed that serotype DENV-3 was the most predominant dengue circulating virus in Sabah with 23 cases detected. These were further grouped under three genotypes namely D3GI (1 case), D3GII (14 cases) and D3GIII (8 cases). Serotype DENV-1 was the second most common circulating virus in Sabah with 17 cases and grouped under two genotypes, D1Gia (15 cases) and D1Gic (2 cases), respectively. On the other hand, only one genotype (D4GII) was detected for DENV-4 (9 cases), and two genotypes (D2 Cosmopolitan Clade I and D2 Cosmopolitan Clade Ib) for DENV-2, each with one case per genotype, respectively. Understanding of genotype diversity will be useful in designing strategies for dengue management in epidemiological surveillance and vaccine design.

Platelet factor 4 promotes rapid replication and propagation of Dengue and Japanese encephalitis viruses.

BackgroundActivated platelets release cytokines/proteins including CXCL4 (PF4), CCL5 and fibrinopeptides, which regulate infection of several pathogenic viruses such as HIV, H1N1 and HCV in human. Since platelet activation is the hallmark of Dengue virus (DV) infection, we investigated the role of platelets in DV replication and also in a closely related Japanese Encephalitis virus (JEV).Methods and findingsMicroscopy and PCR analysis revealed a 4-fold increase in DV replication in primary monocytes or monocytic THP-1 cells in vitro upon incubation with either DV-activated platelets or supernatant from DV-activated platelets. The mass spectrometry based proteomic data from extra-nuclear fraction of above THP-1 lysate showed the crucial association of PF4 with enhanced DV replication. Our cytokine analysis and immunoblot assay showed significant inhibition of IFN-α production in monocytes via p38MAPK-STAT2-IRF9 axis. Blocking PF4 through antibodies or its receptor CXCR3 through inhibitor i.e. AMG487, significantly rescued production of IFN-α resulting in potent inhibition of DV replication in monocytes. Further, flow cytometry and ELISA data showed the direct correlation between elevated plasma PF4 with increased viral NS1 in circulating monocytes in febrile DV patients at day-3 of fever than day-9. Similarly, PF4 also showed direct effects in promoting the JEV replication in monocytes and microglia cells in vitro. The in vitro results were also validated in mice, where AMG487 treatment significantly improved the survival of JEV infected animals. Interpretation: Our study suggests that PF4-CXCR3-IFN axis is a potential target for developing treatment regimen against viral infections including JEV and DV.

Epidemiological trends and molecular dynamics of dengue, chikungunya virus infection, coinfection, and other undifferentiated fever during 2015-2016 in Odisha, India.

Chikungunya virus (CHIKV) infection is spatiotemporally related to dengue virus (DENV) infection and mostly undiagnosed due to similar primary symptoms. In 2013, a high rate (36%) of coinfection of DENV and CHIKV was reported in Odisha. Hence, the hospital-based study was continued to synthesis current epidemiological understanding of their single distribution or coinfection. Suspected DENV patients serum samples were tested for DENV and CHIKV by serology and reverse-transcription polymerase chain reaction. The positive samples were used for analysis of mutation, selection pressure, and phylogenetic relationship. Clinical information was also analyzed. Among 648 (2015 and 2016) suspected DENV patients, 141 (21.7%) were positive for DENV (serotypes 1-3), 22 (3.4%) were positive for CHIKV (ECSA) and 4 (2.8%) were coinfected with both. Sequence analysis showed four consistent mutations (M104V, V112A, K166N, and F169L) in CprM gene of DENV 2 and two consistent mutations (M269V, D284E) in E1 gene of CHIKV. Interestingly, the CHIKV- E1 A226V mutation was absent in the studied population. It was also noticed that the peak incidence of both the infections occurs in August-September in 2015-16. Moreover, Plasmodium species, Salmonella typhi, and Rickettsial typhi infections were also observed in DENV patients. Different etiology was also detected in other undifferentiated fever patients as mixed infections (malaria, S. typhi, and R. typhi ). Hence, this investigation shows the significant reduction of DENV-CHIKV coinfection as compared with previous report, the burden of arboviruses and acute undifferentiated fever in Odisha in 2015-2016, highlighting the importance of epidemiological picture of febrile patients for appropriate patient management.

Human T Lymphocytes Are Permissive for Dengue Virus Replication

Dengue virus (DV) infection can cause either a self-limiting flu-like disease or a threatening hemorrhage that may evolve to shock and death. A variety of cell types, such as dendritic cells, monocytes, and B cells, can be infected by DV. However, despite the role of T lymphocytes in the control of DV replication, there remains a paucity of information on possible DV-T cell interactions during the disease course. In the present study, we have demonstrated that primary human naive CD4+ and CD8+ T cells are permissive for DV infection. Importantly, both T cell subtypes support viral replication and secrete viable virus particles. DV infection triggers the activation of both CD4+ and CD8+ T lymphocytes, but preactivation of T cells reduces the susceptibility of T cells to DV infection. Interestingly, the cytotoxicity-inducing protein granzyme A is highly secreted by human CD4+ but not CD8+ T cells after exposure to DV in vitro Additionally, using annexin V and polycaspase assays, we have demonstrated that T lymphocytes, in contrast to monocytes, are resistant to DV-induced apoptosis. Strikingly, both CD4+ and CD8+ T cells were found to be infected with DV in acutely infected dengue patients. Together, these results show that T cells are permissive for DV infection in vitro and in vivo, suggesting that this cell population may be a viral reservoir during the acute phase of the disease.IMPORTANCE Infection by dengue virus (DV) causes a flu-like disease that can evolve to severe hemorrhaging and death. T lymphocytes are important cells that regulate antibody secretion by B cells and trigger the death of infected cells. However, little is known about the direct interaction between DV and T lymphocytes. Here, we show that T lymphocytes from healthy donors are susceptible to infection by DV, leading to cell activation. Additionally, T cells seem to be resistant to DV-induced apoptosis, suggesting a potential role as a viral reservoir in humans. Finally, we show that both CD4+ and CD8+ T lymphocytes from acutely infected DV patients are infected by DV. Our results raise new questions about DV pathogenesis and vaccine development.

Evidence of dengue and chikungunya virus co-infection and circulation of multiple dengue serotypes in a recent Indian outbreak.

In India, dengue endemic areas overlap with chikungunya-affected areas and both the viruses are transmitted by same vector, Aedes aegypti - thereby increasing opportunity of co-infection by both viruses. Present study was carried out to understand the DENV-CHIKV infection dynamics during recent outbreaks in eastern India (West Bengal state) and its implication on disease manifestations. Blood was collected from 326 symptomatic febrile patients. Patients' serum was subjected to serological diagnosis for presence of anti-dengue-IgM, anti-chikungunya-IgM antibodies and dengue-NS1 antigen by ELISA. Viral RNA was extracted, and presence of dengue virus (DENV) and chikungunya virus (CHIKV) genome, their viral load (VL), and serotype among infected patients' plasma was determined by real-time qRT-PCR. Statistical analysis was performed by using EPI INFO software. DENV and CHIKV were detected in 54% and 33% of symptomatic patients respectively, among whom 23% were harboring both viruses. WHO classified warning signs were detected among 64% DENV patients and 61% DENV-CHIKV double-infected patients. Patients with warning signs always had much higher DEN VL than those without warning signs. Hemorrhagic manifestation and abdominal pain was found in significantly higher frequency among patients with high dengue VL (>10,000 copies/ml). DENV2 was the most predominant serotype among monotypic dengue patients, whereas DENV2-DENV4 combination was most prevalent among patients infected with dual dengue serotypes. This study indicated that DENV-CHIKV double infection and high dengue VL contributed towards severe disease manifestations among infected patients. DENV2 and DENV2-DENV4 combination were the most prevalent serotype(s) found in current outbreak.

Risk factors and clinical outcome of profound thrombocytopenia in adult patients with DENV infections

Severe thrombocytopenia is common in dengue virus (DENV) infections. However, studies focusing on the role of profound thrombocytopenia (PT) (nadir platelet counts ≤ 20 000/mm3) in DENV infections are scarce. This study aims to identify the associated features and outcome of DENV patients with PT. It involves 237 adult hospitalized patients who were DENV PCR positive. The presence of comorbidity (AOR = 4.625; 95% CI = 1.113–19.230), higher admission hematocrit (AOR = 1.213; 95% CI = 1.067–1.379), lower admission albumin (AOR = 0.870; 95% CI = 0.766–0.988) and lower admission platelets (AOR = 0.980; 95% CI = 0.969–0.991) was associated with platelets ≤ 20 000/mm3 in multivariate logistic regression. PT was not affected by DENV serotypes, coinfections and secondary DENV infections. Patients with PT had significantly higher risk of experiencing warning signs (AOR = 3.709, 95% CI = 1.089–12.634) and longer hospital stay (AOR = 1.943, 95% CI = 1.010–3.774). However, severe dengue disease, hemorrhagic manifestations and need for intensive care were not significantly associated with PT.

Dengue Virus Envelope Dimer Epitope Monoclonal Antibodies Isolated from Dengue Patients Are Protective against Zika Virus

ABSTRACTZika virus (ZIKV) is a mosquito-borne flavivirus responsible for thousands of cases of severe fetal malformations and neurological disease since its introduction to Brazil in 2013. Antibodies to flaviviruses can be protective, resulting in lifelong immunity to reinfection by homologous virus. However, cross-reactive antibodies can complicate flavivirus diagnostics and promote more severe disease, as noted after serial dengue virus (DENV) infections. The endemic circulation of DENV in South America and elsewhere raises concerns that preexisting flavivirus immunity may modulate ZIKV disease and transmission potential. Here, we report on the ability of human monoclonal antibodies and immune sera derived from dengue patients to neutralize contemporary epidemic ZIKV strains. We demonstrate that a class of human monoclonal antibodies isolated from DENV patients neutralizes ZIKV in cell culture and is protective in a lethal murine model. We also tested a large panel of convalescent-phase immune sera from humans exposed to primary and repeat DENV infection. Although ZIKV is most closely related to DENV compared to other human-pathogenic flaviviruses, most DENV immune sera (73%) failed to neutralize ZIKV, while others had low (50% effective concentration [EC50], <1:100 serum dilution; 18%) or moderate to high (EC50, >1:100 serum dilution; 9%) levels of cross-neutralizing antibodies. Our results establish that ZIKV and DENV share epitopes that are targeted by neutralizing, protective human antibodies. The availability of potently neutralizing human monoclonal antibodies provides an immunotherapeutic approach to control life-threatening ZIKV infection and also points to the possibility of repurposing DENV vaccines to induce cross-protective immunity to ZIKV.

Dengue vascular leakage is augmented by mast cell degranulation mediated by immunoglobulin Fcγ receptors

Dengue virus (DENV) is the most significant human arboviral pathogen and causes ∼400 million infections in humans each year. In previous work, we observed that mast cells (MC) mediate vascular leakage during DENV infection in mice and that levels of MC activation are correlated with disease severity in human DENV patients (St John et al., 2013b). A major risk factor for developing severe dengue is secondary infection with a heterologous serotype. The dominant theory explaining increased severity during secondary DENV infection is that cross-reactive but non-neutralizing antibodies promote uptake of virus and allow enhanced replication. Here, we define another mechanism, dependent on FcγR-mediated enhanced degranulation responses by MCs. Antibody-dependent mast cell activation constitutes a novel mechanism to explain enhanced vascular leakage during secondary DENV infection.

Pro-inflammatory cytokine induction by in vitro Dengue Virus-infection was selectively inhibited by patient serum rich in IgG1 subclass antibodies.

Event Abstract Back to Event Pro-inflammatory cytokine induction by in vitro Dengue Virus-infection was selectively inhibited by patient serum rich in IgG1 subclass antibodies. Judith Gonzalez Christen1*, Karina R. Flores Avila1, Rosa M. Medina Julian2 and José-Luis Montiel-Hernandez1 1 Facultad de Farmacia Universidad Autónoma del Estado de Morelos, Mexico 2 Laboratorio Estatal de Salud Publica Morelos, Mexico Introduction: Human infection with Dengue Virus (DV) is characterized by fever associated to an inflammatory response, which can progress as Dengue fever (DF) or as severe disease, Dengue Hemorrhagic fever (DHF), where higher levels of TNF, IL-1beta, Il-8, IFN-gamma, and IL-6 are associated with more severe manifestations (1,2,3). Antibodies have been also implicated on the severity of disease. Studies by Koraka and Thein have observed higher levels of anti-dengue lgG1 subclass antibodies in association with DHF(4,5,6). Additionally, results from our group found that total IgG1subclass antibodies were higher in DHF patients than those with DF. In the same context, cross-reactive antibodies from previous DV infections have been suggested to predispose to more severe secondary disease by a mechanism called ADE (antibody-enhanced infection of dengue target cells bearing Fc receptors). Some studies have suggested that immunoglobulin-mediated DV entry could modify the secretory activity of macrophages and induce NO or type I Interferon inhibition (7,8). But since the pre-exiting enhancing antibodies capable of inducing ADE’s effect were found at very low concentrations, it remains to be confirmed if these molecules are the only molecules to induce the severe symptoms of the disease. In this respect, a previous study by our group showed a positive correlation between serum levels of IgG1 and IL-1beta, but not with IL-6 levels, suggesting that even non-specific antibodies could have a role in the pro-inflammatory conditions. The aim of the present study was to characterize the role of neutralizing antibodies in the course of the in vitro DV-infection of macrophages and the secretion of pro-inflammatory cytokines. Additionally, to compare the effects of serum with low levels of IgG1/IL-1beta with those of patients with high concentrations of IgG1/IL-1beta in this mechanism. Material and Methods. THP-1 cell line (ATCC Tib202), differentiated with PMA 10 nM for 72 hrs, was employed as a macrophage model. In vitro DV-Infection assays were done at 1 MOI of Den-2 (New Guinea C). For the opsonized-assays, sera from 5 healthy donors (Ctr) was employed, 5 patient provided sera with low IgG1titers (LI) and 5 patient sera with higher IgG1 titers (HI); virus were pre-incubated for 1 hour with diluted serum (1:1000, in PBS) before infection. 2 hours after infection, cells were washed in PBS and cultured for 12, 24 or 48 hours in RPMI-1640/10% fetal bovine serum. TNF, IL-6 or IL-1beta were quantified using ELISA on cell culture supernatants and infection was evaluated by fluorescence microscopy. Results. DV-infection of macrophages induced the secretion of all cytokines evaluated but showed an outdated profile where peak TNF occurred at 12hrs, peak IL-1beta at 24 hrs and peak IL-6 at 48 hrs. Pre-incubation of DV with serum reduces the rate of infection, even with Ctr serum (17%); but inhibition was significantly higher with patient’s sera (LI, 36%; HI, 59%). Supernatant TNF secretion was decreased with all types of serum evaluated, also showing significant higher inhibitory effect by HI sera (Ctr, 17%; LI, 26% and HI, 38%). IL-6 secretion was also decreased by serum pre-incubation, but the maximum inhibitory effect was observed at 48 hours, where LI and HI showed a similar effect (Ctr, 17%; LI, 31%; HI, 34%). Finally, for IL-1beta we observed an inhibition at 12 hours of 60% with Ctr serum and 68% with LI or HI sera, but at 24hours, the inhibition obtained was of 75%, 67% and 50% for Ctr, LI and HI, respectively. At 48 hrs of DV infection, all sera induced a similar inhibitory effect (56%). Conclusions. Our results lead us to suggest that although the rate of infection is important to promote the pro-inflammatory cytokine secretion, other factors also contribute to modulate this effect since patient’s sera with high IgG1 levels showed increased inhibitory effect mediated by TNF, but this was not the case for IL-6 or IL-1beta. It should be noted that only the TNF’ inhibitory effect correlated with the rate of infection. Paradoxically, IL-1beta inhibition was higher employing sera from healthy donors, in comparison to DV patients, suggesting a modulation by a non-specific and IgG1-independent mechanism. Acknowledgements KFA was suppoted by a scholarship from CONACyT (350115). This work was supported by grant PROMEP-SEP 103.5/13/5259 and Facultad de Farmacia-UAEM.

Human Arthropod-Borne Viral Infections

Human Arthropod-Borne Viral Infections