Higher levels of dengue-virus-specific IgG and IgA during pre-defervescence associated with primary dengue hemorrhagic fever

Evolution of inflammation and immunity in a dengue virus 1 human infection model

Dengue virus (DENV) infections are major causes of morbidity and mortality throughout the tropics and subtropics. More than 400 million infections are estimated to occur every year, resulting in nearly 100 million symptomatic infections and more than 20,000 deaths. Early immune response kinetics to infection remain unclear, in large part due to the variable incubation period exhibited by the DENVs after introduction into a susceptible host. To fill this knowledge gap, we performed a comprehensive virologic and immunologic analysis of individuals experimentally infected with the underattenuated DENV-1 strain 45AZ5. This analysis captured both the kinetics and composition of the innate, humoral, and cellular immune responses elicited by experimental DENV-1 infection, as well as virologic and clinical features. We observed a robust DENV-specific immunoglobulin A (IgA) antibody response that manifested between the appearance of DENV-specific IgM and IgG in all challenged individuals, as well as the presence of a non-neutralizing/NS1-specific antibody response that was delayed relative to the appearance of DENV virion–specific humoral immunity. RNA sequencing analysis revealed discrete and temporally restricted gene modules that correlated with acute viremia and the induction of adaptive immunity. Our analysis provides a detailed description, in time and space, of the evolving matrix of DENV-elicited human inflammation and immunity and reveals several previously unappreciated immunological aspects of primary DENV-1 infection that can inform countermeasure development and evaluation.

Association of self-reported allergic rhinitis with dengue severity: A case-control study

BACKGROUND

The severity of dengue infection has been reportedly associated with patients' allergic reactions. To further elucidate the role of allergy in dengue severity, we conducted a matched case-control study to assess the association between allergic background and dengue shock syndrome.

METHODS

This is a matched case-control study that was carried out in the Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam from January to December 2017. Dengue infection was determined by non-structure protein 1 (NS1) diagnostic quick test or anti-dengue antibodies (IgM). The total and dengue-specific IgE levels were measured using ELISA. Patients' demographics, clinical, and allergic profiles were collected using a structured questionnaire.

RESULTS

A total of 572 dengue patients with positive NS1 (92.7%) or IgM antibodies (7.3%) results were included in this study. Of these patients, 143 patients developed dengue shock syndrome (case group) while the other 429 patients did not (control group). None of the baseline characteristics including age, sex, or being overweight was significantly different between the two groups (p>0.05). In multivariable analysis, having a history of dengue infection (OR=3.35, 95% CI: 1.8-6.17, p<0.001) and allergic rhinitis (OR=1.95, 95% CI: 1.11-3.4, p = 0.019) were found to be associated with dengue shock syndrome. Higher levels of dengue-specific IgE were not associated with worse outcomes in patients with allergies (p = 0.204) or allergic rhinitis (p = 0.284).

CONCLUSION

Dengue patients presenting with a history of a previous dengue infection or allergic rhinitis should be considered high-risk patients for the development of dengue shock syndrome.

Monomeric IgA Antagonizes IgG-Mediated Enhancement of DENV Infection

Dengue virus (DENV) is a prevalent human pathogen, infecting approximately 400 million individuals per year and causing symptomatic disease in approximately 100 million. A distinct feature of dengue is the increased risk for severe disease in some individuals with preexisting DENV-specific immunity. One proposed mechanism for this phenomenon is antibody-dependent enhancement (ADE), in which poorly-neutralizing IgG antibodies from a prior infection opsonize DENV to increase infection of F_c gamma receptor-bearing cells. While IgM and IgG are the most commonly studied DENV-reactive antibody isotypes, our group and others have described the induction of DENV-specific serum IgA responses during dengue. We hypothesized that monomeric IgA would be able to neutralize DENV without the possibility of ADE. To test this, we synthesized IgG and IgA versions of two different DENV-reactive monoclonal antibodies. We demonstrate that isotype-switching does not affect the antigen binding and neutralization properties of the two mAbs. We show that DENV-reactive IgG, but not IgA, mediates ADE in F_c gamma receptor-positive K562 cells. Furthermore, we show that IgA potently antagonizes the ADE activity of IgG. These results suggest that levels of DENV-reactive IgA induced by DENV infection might regulate the overall IgG mediated ADE activity of DENV-immune plasma in vivo, and may serve as a predictor of disease risk.

Development and Characterization of a Multiplex Assay to Quantify Complement-Fixing Antibodies against Dengue Virus

Antibodies capable of activating the complement system (CS) when bound with antigen are referred to as "complement-fixing antibodies" and are involved in protection against Flaviviruses. A complement-fixing antibody test has been used in the past to measure the ability of dengue virus (DENV)-specific serum antibodies to activate the CS. As originally developed, the test is time-consuming, cumbersome, and has limited sensitivity for DENV diagnosis. Here, we developed and characterized a novel multiplex anti-DENV complement-fixing assay based on the Luminex platform to quantitate serum antibodies against all four serotypes (DENV1-4) that activate the CS based on their ability to fix the complement component 1q (C1q). The assay demonstrated good reproducibility and showed equivalent performance to a DENV microneutralization assay that has been used to determine DENV serostatus. In non-human primates, antibodies produced in response to primary DENV1-4 infection induced C1q fixation on homologous and heterologous serotypes. Inter-serotype cross-reactivity was associated with homology of the envelope protein. Interestingly, the antibodies produced following vaccination against Zika virus fixed C1q on DENV. The anti-DENV complement fixing antibody assay represents an alternative approach to determine the quality of functional antibodies produced following DENV natural infection or vaccination and a biomarker for dengue serostatus, while providing insights about immunological cross-reactivity among different Flaviviruses.

A review targeting the infection by CHIKV using computational and experimental approaches

The rise of normal body temperature of 98.6 °F beyond 100.4 °F in humans indicates fever due to some illness or infection. Viral infections caused by different viruses are one of the major causes of fever. One of such viruses is, Chikungunya virus (CHIKV) is known to cause Chikungunya fever (CHIKF) which is transmitted to humans through the mosquitoes, which actually become the primary source of transmission of the virus. The genomic structure of the CHIKV consists of the two open reading frames (ORFs). The first one is a 5' end ORF and it encodes the nonstructural protein (nsP1-nsP4). The second is a 3' end ORF and it encodes the structural proteins, which is consisted of capsid, envelope (E), accessory peptides, E3 and 6 K. Till date, there is no effective vaccine or medicine available for early detection of the CHIKV infection and appropriate diagnosis to cure the patients from the infection. NSP3 of CHIKV is the prime target of the researchers as it is responsible for the catalytic activity. This review has updates of literature on CHIKV; pathogenesis of CHIKV; inhibition of CHIKV using theoretical and experimental approaches.Communicated by Ramaswamy H. Sarma.

Association of Allergic Symptoms with Dengue Infection and Severity: A Systematic Review and Meta-analysis

The relationship between the severity of dengue infection and allergy is still obscure. We conducted an electronic search across 12 databases for relevant articles reporting allergic symptoms, dengue infection, and dengue classification. These studies were categorized according to dengue severity and allergy symptoms, and a meta-analysis was performed by pooling the studies in each category. Among the included 57 articles, pruritus was the most common allergic sign followed by non-specified allergy and asthma (28.6%, 13%, and 6.5%, respectively). Despite the reported significant association of dengue with pruritus and total IgE level (P < 0.05), in comparison with non-dengue cases and healthy controls, there was no association between the different severe dengue group with pruritus, skin allergy, food allergy or asthma. However, removing the largest study revealed a significant association between asthma with dengue hemorrhagic fever (DHF) rather than dengue fever (DF). In comparison with DF, DHF was associated with IgE positivity. Furthermore, specific-IgE level was higher in secondary DF rather than primary DF. There was a possible association between allergy symptoms and dengue severity progression. Further studies are needed to clarify this association.

Association between dengue severity and plasma levels of dengue-specific IgE and chymase

There is no definitive predictor of dengue severity, and this has led to a very large number of unnecessary hospitalizations worldwide. Although mast cell mediators are believed to a play role in dengue severity, the lack of precise kinetic data demands further research on early predictors. We enrolled 111 patients with confirmed dengue and 85 with "other febrile illness" (OFI) in a hospital-based prospective study in Vietnam. Dengue patients were classified as level 1, 2, or 3 based on the clinical intervention received. Blood samples were collected from each patient every day (pre- and post-defervescence) and after discharge. Plasma chymase, total IgE, and dengue-specific IgE were measured. Dengue-specific IgE levels showed an increasing trend during the course of illness and remained high even at post-discharge, although no significant difference was observed among severity levels. Total IgE showed no such trend. The specific IgE/total IgE ratio (S/T ratio) remained constantly higher in level 3 patients compared to other levels, with a significant difference at some time points. The S/T ratio of acute phase samples (before defervescence) tended to increase with increasing severity (level 1 < 2 < 3), and was significantly higher in level 3 patients than in level 1 and OFI patients. As an early predictor of severity allowing level 3 patients to be distinguished from other dengue patients, the S/T ratio achieved a sensitivity of 75% and specificity of 68%. We describe the kinetic profiles of IgEs, their ratio, and chymase levels at different severity levels. The S/T ratio was found to be associated with dengue severity, suggesting that it could potentially be used as an early predictor of severity.

Shared IgG Infection Signatures vs. Hemorrhage-Restricted IgA Clusters in Human Dengue: A Phenotype of Differential Class-Switch via TGFβ1

Phenotypic manifestations of infectious diseases are closely related to individual immune responses. Methods to extract information from patients' own immune reactions would be of great use for both diagnosis and treatment. Dengue fever is one of the diseases that clinical aggravations could occur paradoxically after humoral immunity appears. This property makes dengue fever an excellent disease model to explore. A principal component analyses (PCAs)-based framework derived from a prior vaccination study was developed. The framework was verified by successful demonstrations of known IgG signatures from a Mexico Dengue data set. Afterward the pipeline was tested upon de novo IgG and IgA libraries of Dengue patients from southern Taiwan. We discovered four infection signatures within IgG repertoires, two of which were identical to previous reports. However, it was IgA but not IgG that could differentiate hemorrhagic from non-hemorrhagic patients. IgA repertoires were found more diversified among bleeders, from whom seven signature clusters were characterized. The expressions of transforming growth factor beta 1 (TGFβ1) and accordingly mediated class-switch activity of IgA were distinct only among the PCA-segregated bleeding group. In sum, intercontinental sharing of IgG signatures in dengue fever was demonstrated via a unified working flow. Differential regulation of IgA class-switch with associated diversity expansion plus existences of hemorrhage-restricted clusters were shown. The ability of the framework to find common IgG signatures would implicate applications to infections even from unknown pathogens. The clusters within IgA repertoires could offer perspectives to other IgA-related bleeding disorders such as Henoch-Schönlein purpura or IgA nephropathy. Substantiated grounds for IgA-specific effector function via TGFβ1-mediated class-switch would be a new factor to consider for infectious diseases.

Meta-analysis of biomarkers for severe dengue infections

BACKGROUND

Dengue viral infection is an acute infection that has the potential to have severe complications as its major sequela. Currently, there is no routine laboratory biomarker with which to predict the severity of dengue infection or monitor the effectiveness of standard management. Hence, this meta-analysis compared biomarker levels between dengue fever (DF) and severe dengue infections (SDI) to identify potential biomarkers for SDI.

METHODS

Data concerning levels of cytokines, chemokines, and other potential biomarkers of DF, dengue hemorrhagic fever, dengue shock syndrome, and severe dengue were obtained for patients of all ages and populations using the Scopus, PubMed, and Ovid search engines. The keywords "(IL1* or IL-1*) AND (dengue*)" were used and the same process was repeated for other potential biomarkers, according to Medical Subject Headings terms suggested by PubMed and Ovid. Meta-analysis of the mean difference in plasma or serum level of biomarkers between DF and SDI patients was performed, separated by different periods of time (days) since fever onset. Subgroup analyses comparing biomarker levels of healthy plasma and sera controls, biomarker levels of primary and secondary infection samples were also performed, as well as analyses of different levels of severity and biomarker levels upon infection by different dengue serotypes.

RESULTS

Fifty-six studies of 53 biomarkers from 3,739 dengue cases (2,021 DF and 1,728 SDI) were included in this meta-analysis. Results showed that RANTES, IL-7, IL-8, IL-10, IL-18, TGF-b, and VEGFR2 levels were significantly different between DF and SDI. IL-8, IL-10, and IL-18 levels increased during SDI (95% CI, 18.1-253.2 pg/mL, 3-13 studies, n = 177-1,909, I2 = 98.86%-99.75%). In contrast, RANTES, IL-7, TGF-b, and VEGFR2 showed a decrease in levels during SDI (95% CI, -3238.7 to -3.2 pg/mL, 1-3 studies, n = 95-418, I2 = 97.59%-99.99%). Levels of these biomarkers were also found to correlate with the severity of the dengue infection, in comparison to healthy controls. Furthermore, the results showed that IL-7, IL-8, IL-10, TGF-b, and VEGFR2 display peak differences between DF and SDI during or before the critical phase (day 4-5) of SDI.

DISCUSSION

This meta-analysis suggests that IL-7, IL-8, IL-10, TGF-b, and VEGFR2 may be used as potential early laboratory biomarkers in the diagnosis of SDI. This can be used to predict the severity of dengue infection and to monitor the effectiveness of treatment. Nevertheless, methodological and reporting limitations must be overcome in future research to minimize variables that affect the results and to confirm the findings.

Secretory phospholipase A2 in the pathogenesis of acute dengue infection

Introduction

Platelet activating factor (PAF) is an important mediator of vascular leak in acute dengue. Phospholipase A2s (PLA2) are inflammatory lipid enzymes that generate and regulate PAF and other mediators associated with mast cells. We sought to investigate if mast cell activation and increases in secretory sPLA2s are associated with an increase in PAF and occurrence of dengue haemorrhagic fever (DHF).

Methods

The changes in the levels of mast cell tryptase, PAF and the activity of sPLA2 were determined throughout the course of illness in 13 adult patients with DHF, and 30 patients with dengue fever (DF).

Results

We found that sPLA2 activity was significantly higher in patients with DHF when compared to those with DF, during the first 120 h of clinical illness. sPLA2 activity was significantly associated with PAF levels, which were also significantly higher in patients with DHF. Although levels of mast cell tryptase were higher in patients with DHF, the difference was not significant, and the levels were not above the reference ranges. sPLA2 activity significantly correlated with the degree of viraemia in patients with DHF but not in those with DF.

Conclusion

sPLA2 appears to play an important role in the pathogenesis of dengue. Since its activity is significantly increased during the early phase of infection in patients with DHF, this suggests that understanding the underlying mechanisms may provide opportunities for early intervention.