Kinetics of antibodies in sera, saliva, and urine samples from adult patients with primary or secondary dengue 3 virus infections

Dengue virus serotype did not contribute to clinical severity or mortality in Taiwan's largest dengue outbreak in 2015

BACKGROUND

Dengue virus serotype 2 (DENV-2) was the major serotype in the 2015 dengue outbreak in Taiwan, while DENV-1 and DENV-3 were dominant between 2005 and 2014. We aimed to investigate whether DENV-2 contributed to disease severity and mortality in the outbreak in Kaohsiung city, Taiwan.

METHODS

We collected serum samples from dengue patients to detect the presence of DENV and determine the serotypes by using quantitative reverse transcription-polymerase chain reaction. Our cohorts comprised 105 DENV-1-infected cases and 1,550 DENV-2-infected cases. Demographic data, DENV serotype, and comorbidities were covariates for univariate and multivariate analyses to explore the association with severity and mortality.

RESULTS

The results suggested that DENV-1 persisted and circulated, while DENV-2 was dominant during the dengue outbreak that occurred between September and December 2015. However, DENV-2 did not directly contribute to either severity or mortality. Aged patients and patients with diabetes mellitus (DM) or moderate to severe chronic kidney disease (CKD) had a higher risk of developing severe dengue. The mortality of dengue patients was related to a higher Charlson comorbidity index score and severe dengue. Among DENV-2-infected patients and older patients, preexisting anti-dengue IgG, DM, and moderate to severe CKD were associated with severe dengue. Moreover, female sex and severe dengue were associated with a significantly higher risk of death.

CONCLUSIONS

Our findings highlight the importance of timely serological testing in elderly patients to identify potential secondary infections and focus on the meticulous management of elderly patients with DM or moderate to severe CKD to reduce dengue-related death.

Identification of Torquetenovirus Species in Patients with Kawasaki Disease Using a Newly Developed Species-Specific PCR Method

A next-generation sequencing (NGS) study identified a very high viral load of Torquetenovirus (TTV) in KD patients. We aimed to evaluate the feasibility of a newly developed quantitative species-specific TTV-PCR (ssTTV-PCR) method to identify the etiology of KD. We applied ssTTV-PCR to samples collected from 11 KD patients and 22 matched control subjects who participated in our previous prospective study. We used the NGS dataset from the previous study to validate ssTTV-PCR. The TTV loads in whole blood and nasopharyngeal aspirates correlated highly (Spearman's R = 0.8931, p < 0.0001, n = 33), supporting the validity of ssTTV-PCR. The ssTTV-PCR and NGS results were largely consistent. However, inconsistencies occurred when ssTTV-PCR was more sensitive than NGS, when the PCR primer sequences mismatched the viral sequences in the participants, and when the NGS quality score was low. Interpretation of NGS requires complex procedures. ssTTV-PCR is more sensitive than NGS but may fail to detect a fast-evolving TTV species. It would be prudent to update primer sets using NGS data. With this precaution, ssTTV-PCR can be used reliably in a future large-scale etiological study for KD.

Evaluation of an Immunoglobulin E Capture Enzyme-Linked Immunosorbent Assay for the Early Diagnosis of Dengue

Dengue virus (DENV) is the etiological agent of dengue, the most important mosquito-transmitted viral disease of humans worldwide. Enzyme-linked immunosorbent assays (ELISAs) designed to detect DENV IgM are commonly used for dengue diagnosis. However, DENV IgM is not reliably detected until ≥4 days after illness onset. Reverse transcription-polymerase chain reaction (RT-PCR) can diagnose early dengue but requires specialized equipment, reagents, and trained personnel. Additional diagnostic tools are needed. Limited work has been performed to determine whether IgE-based assays can be used for the early detection of vector-borne viral diseases, including dengue. In this study, we determined the efficacy of a DENV IgE capture ELISA for the detection of early dengue. Sera were collected within the first 4 days of illness onset from 117 patients with laboratory-confirmed dengue, as determined by DENV-specific RT-PCR. The serotypes responsible for the infections were DENV-1 and DENV-2 (57 and 60 patients, respectively). Sera were also collected from 113 dengue-negative individuals with febrile illness of undetermined etiology and 30 healthy controls. The capture ELISA detected DENV IgE in 97 (82.9%) confirmed dengue patients and none of the healthy controls. There was a high false positivity rate (22.1%) among the febrile non-dengue patients. In conclusion, we provide evidence that IgE capture assays have the potential to be explored for early diagnosis of dengue, but further research is necessary to address the possible false positivity rate among patients with other febrile illnesses.

Urine and Saliva: Relevant Specimens for Malaria Diagnosis?

Blood remains the specimen of preference for malaria diagnosis, whether it is for microscopic, nucleic acid-based or biomarker detection of Plasmodium present in a patient. However, concerning the disadvantages of blood drawing, specimens that can be non-invasively collected under non-hygienic settings would come in handy for malaria diagnosis in endemic areas with limited resources. Although the current approaches using saliva or urine might not be as sensitive and specific as using blood, the potential of these two specimens should not be underestimated and efforts in developing diagnostic methods for Plasmodium detection specifically in these two specimens should continue without giving up. This review not only compiles and summarizes the sensitivity and specificity achieved by various detection approaches when using these samples for malaria diagnosis, it also intends to enhance the possibility of using saliva and urine for diagnostic purposes by describing how Plasmodium nucleic acid and antigens may likely be present in these samples. This review may hopefully encourage and motivate researchers in developing saliva- and urine-based diagnostic methods for Plasmodium detection to facilitate the control and eradication of malaria. In summary, the presence of Plasmodium DNA and antigens in urine and saliva makes these two specimens relevant and useful for malaria diagnosis.

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.

Detecting anti-SARS-CoV-2 antibodies in urine samples: A noninvasive and sensitive way to assay COVID-19 immune conversion

Serum-based ELISA (enzyme-linked immunosorbent assay) has been widely used to detect anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. However, to date, no study has investigated patient urine as a biological sample to detect SARS-CoV-2 virus-specific antibodies. An in-house urine-based ELISA was developed using recombinant SARS-CoV-2 nucleocapsid protein. The presence of SARS-CoV-2 antibodies in urine was established, with 94% sensitivity and 100% specificity for the detection of anti-SARS-CoV-2 antibodies with the urine-based ELISA and 88% sensitivity and 100% specificity with a paired serum-based ELISA. The urine-based ELISA that detects anti-SARS-CoV-2 antibodies is a noninvasive method with potential application as a facile COVID-19 immunodiagnostic platform, which can be used to report the extent of exposure at the population level and/or to assess the risk of infection at the individual level.

Integrated view of molecular diagnosis and prognosis of dengue viral infection: future prospect of exosomes biomarkers

Dengue viruses (DENVs) are the viruses responsible for dengue infection which affects lungs, liver, heart and also other organs of individuals. DENVs consist of the group of four serotypically diverse dengue viruses transmitted in tropical and sub-tropical countries of world. Aedes mosquito is the principal vector which spread the infection from infected person to healthy humans. DENVs can cause different syndromes depending on serotype of virus which range from undifferentiated mild fever to dengue hemorrhagic fever resulting in vascular leakage due to release of cytokine and Dengue shock syndrome with fluid loss and hypotensive shock, or other severe manifestations such as bleeding and organ failure. Increase in dengue cases in pediatric population is a major concern. Transmission of dengue depends on various factors like temperature, rainfall, and distribution of Aedes aegypti mosquitoes. The present review describes a comprehensive overview of dengue, pathophysiology, diagnosis, treatment with an emphasis on potential of exosomes as biomarkers for early prediction of dengue in pediatrics.

[Dengue virus E protein-based luciferase immunosorbent assay for detecting dengue virus IgG antibody]

OBJECTIVE

To establish a luciferase immunosorbent assay (DENV-LISA) based on dengue virus (DENV) E protein, a specific antigen of DENV, for detection of DENV IgG antibody.

METHODS

The fused expression plasmids of DENV1-E1 and DENV2-E2 with luciferase were constructed. The plasmids were transfected into 293T cells, and the fusion protein containing the specific antigen and luciferase was obtained for establishing DENV-LISA. The specificity and sensitivity of DENV-LISA were assessed and compared with those of commercial DENV IgG antibody detection kit (ELISA).

RESULTS

The established DENV-LISA had a positive detection rate of 32.4% and a specificity of 96.6%, showing a similar positive detection rate with the commercial ELISA kit (35.3%; P>0.05). DENV-LISA was capable of detecting positive samples with a 1: 6400 dilution with a high sensitivity. The test values of DENV-LISA did not differ significantly between plates or within plates in the same batch (P> 0.05), suggesting a good reproducibility of the test.

CONCLUSION

The luciferase immunosorbent assay based on DENV E protein has high specificity and sensitivity for detecting DENV IgG antibody, and can be used for early screening, surveillance and epidemiological investigation of DENV infection.

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.

Non-Invasive Dengue Diagnostics-The Use of Saliva and Urine for Different Stages of the Illness

Dengue diagnosis is largely dependent on clinical symptoms and routinely confirmed with laboratory detection of dengue virus in patient serum samples collected via phlebotomy. This presents a challenge to patients not amenable to venipuncture. Non-invasive methods of dengue diagnosis have the potential to enhance the current dengue detection algorithm. In this study, samples from dengue infected patients were collected between January 2012 until September 2012 and September 2013 until December 2013 in two different setups. Panel A samples (blood, urine, and saliva) were collected daily when the 39 patients were hospitalised and during their follow-up visits while Panel B samples (saliva) were collected from 23 patients during the acute stage of dengue. Using DENV PCR on Panel A, from day 2 to day 4 post fever onset, serum showed the best overall positivity followed by saliva and urine (100%/82.1%/67.9%). From day 5 until day 10 post fever onset, serum and urine had similar positivity (67.4%/61.2%), followed by saliva (51.3%). Beyond day 10 post fever onset, DENV was undetectable in sera, but urine and saliva showed 56.8% and 28.6% positivity, respectively. DENV in urine was detectable up until 32 days post fever. Panel B results showed overall sensitivity of 32.4%/36% (RNA/NS1) for DENV detection in saliva. Our results suggest that the urine-based detection method is useful especially for late dengue detection, where DENV is undetected in sera but still detectable in urine. This provides a potential tool for the physician to pick up new cases in an area where there is ongoing dengue transmission and subsequently prompt for intensified vector control activities.

Antibody and B cell responses to SARS-CoV-2 infection and vaccination

Antibodies, and the B cell and plasma cell populations responsible for their production, are key components of the human immune system's response to SARS-CoV-2, which has caused the coronavirus disease 2019 (COVID-19) pandemic. Here, we review findings addressing the nature of antibody responses against SARS-CoV-2 and their role in protecting from infection or modulating COVID-19 disease severity. In just over a year, much has been learned, and replicated in independent studies, about human immune responses to this pathogen, contributing to the development of effective vaccines. Nevertheless, important questions remain about the duration and effectiveness of antibody responses, differences between immunity derived from infection compared to vaccination, the cellular basis for serological findings, and the extent to which viral variants will escape from current immunity.

Detection of Urinary Antibodies and Its Application in Epidemiological Studies for Parasitic Diseases

For epidemiological studies of infectious diseases, pathogen-specific antibody levels in an area give us essential and appropriate information. The antibodies against pathogens are usually detected in blood, the drawing of which inconveniences people. Collection of blood increases the risk of accidental infections through blood, and it is difficult to obtain the participation of the target populations, especially the younger generation. On the other hand, urine samples, which contain a high enough level of antibodies for ELISA, can be harmlessly and easily collected and therefore have been used for epidemiological studies for diseases. The antibody examination of urine has been used for the epidemiology of parasitic diseases with a high sensitivity and specificity of serum samples. In this paper, we reviewed antibody assays with urine for seven parasitic diseases that urine diagnostic methods have reported in the past, and these are important infections included in NTDs, caused, for example, by Leishmania donovani, Wuchereria bancrofti, Schistosoma japonicum, Paragonimus westermani, Echinococcus granulosus, Echinococcus multilocularis, Strongyloides stercoralis, and Opisthorchis viverrini. The easy and safe urine surveillance system might be an admirable tool for future epidemiological studies for infectious diseases.

Sero-prevalence of arthropod-borne viral infections among Lukanga swamp residents in Zambia

INTRODUCTION

The re-emergence of vector borne diseases affecting millions of people in recent years has drawn attention to arboviruses globally. Here, we report on the sero-prevalence of chikungunya virus (CHIKV), dengue virus (DENV), mayaro virus (MAYV) and zika virus (ZIKV) in a swamp community in Zambia.

METHODS

We collected blood and saliva samples from residents of Lukanga swamps in 2016 during a mass-cholera vaccination campaign. Over 10,000 residents were vaccinated with two doses of Shanchol™ during this period. The biological samples were collected prior to vaccination (baseline) and at specified time points after vaccination. We tested a total of 214 baseline stored serum samples for IgG antibodies against NS1 of DENV and ZIKV and E2 of CHIKV and MAYV on ELISA. We defined sero-prevalence as the proportion of participants with optical density (OD) values above a defined cut-off value, determined using a finite mixture model.

RESULTS

Of the 214 participants, 79 (36.9%; 95% CI 30.5-43.8) were sero-positive for Chikungunya; 23 (10.8%; 95% CI 6.9-15.7) for Zika, 36 (16.8%; 95% CI 12.1-22.5) for Dengue and 42 (19.6%; 95% CI 14.5-25.6) for Mayaro. Older participants were more likely to have Zika virus whilst those involved with fishing activities were at greater risk of contracting Chikungunya virus. Among all the antigens tested, we also found that Chikungunya saliva antibody titres correlated with baseline serum titres (Spearman's correlation coefficient = 0.222; p = 0.03).

CONCLUSION

Arbovirus transmission is occurring in Zambia. This requires proper screening tools as well as surveillance data to accurately report on disease burden in Zambia.

Transcriptional and clonal characterization of B cell plasmablast diversity following primary and secondary natural DENV infection

Antibody-mediated humoral immunity is thought to play a central role in mediating the immunopathogenesis of acute DENV infection, but limited data are available on the diversity, specificity, and functionality of the antibody response at the molecular level elicited by primary or secondary DENV infection. In order to close this functional gap in our understanding of DENV-specific humoral immunity, we utilized high-throughput single cell RNA sequencing to investigate B cells circulating in both primary and secondary natural DENV infections. We captured full-length paired immunoglobulin receptor sequence data from 9,027 B cells from a total of 6 subjects, including 2,717 plasmablasts. In addition to IgG and IgM class-switched cells, we unexpectedly found a high proportion of the DENV-elicited plasmablasts expressing IgA, principally in individuals with primary DENV infections. These IgA class-switched cells were extensively hypermutated even in individuals with a serologically confirmed primary DENV infection. Utilizing a combination of conventional biochemical assays and high-throughput shotgun mutagenesis, we determined that DENV-reactive IgA class-switched antibodies represent a significant fraction of DENV-reactive Igs generated in response to DENV infection, and that they exhibit a comparable epitope specificity to DENV-reactive IgG antibodies. These results provide insight into the molecular-level diversity of DENV-elicited humoral immunity and identify a heretofore unappreciated IgA plasmablast response to DENV infection.

Epidemiological study on dengue in southern Brazil under the perspective of climate and poverty

Social and epidemiological aspects of dengue were evaluated in an important metropolitan area in southern Brazil, from August 2012 to September 2014. Demographic, clinical, serological data were collected from patients with acute dengue symptoms treated at public health system units (HSUs). A systematic approach to analyze the spatial and temporal distribution of cases was developed, considering the temporal cross-correlation between dengue and weather, and the spatial correlation between dengue and income over the city's census tracts. From the 878 patients with suggestive symptoms, 249 were diagnosed as positive dengue infection (28%). Considering the most statistically significant census tracts, a negative correlation was found between mean income and dengue (r = -0.65; p = 0.02; 95% CI: -0.03 to -0.91). The occurrence of dengue followed a seasonal distribution, and it was found to be three and four months delayed in relation to precipitation and temperature, respectively. Unexpectedly, the occurrence of symptomatic patients without dengue infection followed the same seasonal distribution, however its spatial distribution did not correlate with income. Through this methodology, we have found evidence that suggests a relation between dengue and poverty, which enriches the debate in the literature and sheds light on an extremely relevant socioeconomic and public health issue.

The detection of anti-dengue virus IgM in urine in participants enrolled in an acute febrile illness study in Puerto Rico

BACKGROUND

Dengue is an important arboviral disease with about 100 million dengue cases per year, of which, ~5% result in severe disease. Clinical differentiation of dengue from other acute febrile illnesses (AFI) is difficult, and diagnostic blood tests are costly. We evaluated the utility of anti-DENV IgM in urine to identify dengue cases among AFI patients enrolled in a clinical study.

METHODS

Between May 2012-March 2013, 1538 study participants with fever for ≤7 days were enrolled, a medical history was obtained, and serum and urine specimens were collected. Serum was tested for DENV RNA and anti-DENV IgM. Urine was tested for anti-DENV IgM, and its sensitivity and specificity to detect sera laboratory-positive dengue cases were calculated. We evaluated if urine anti-DENV IgM positivity early (≤5 days post-illness onset [DPO]) and late (6-14 DPO) in the clinical course was associated with dengue severity.

RESULTS

Urine anti-DENV IgM sensitivity and specificity were 47.4% and 98.5%, respectively, when compared with serum anti-DENV IgM ELISA results, and 29.7% and 91.1% when compared with serum rRT-PCR results. There was no correlation between urine anti-DENV IgM positivity and patient sex or pre-existing chronic disease. Early in the clinical course, a significantly higher proportion of those who developed dengue with warning signs had anti-DENV IgM in their urine when compared to those without warning signs (20.4% vs. 4.3%). There was no difference in the proportion with urine anti-DENV IgM positivity between severity groups late in the clinical course.

CONCLUSION

While detection of urine anti-DENV IgM lacked adequate diagnostic sensitivity, it is a highly specific marker for laboratory-positive dengue, and its presence early in the clinical course may distinguish those with more severe disease. Further assessment of urine anti-DENV IgM by DPO is warranted to determine its utility as an early diagnostic (and possibly prognostic) marker for dengue.

Find the right sample: A study on the versatility of saliva and urine samples for the diagnosis of emerging viruses

BACKGROUND

The emergence of different viral infections during the last decades like dengue, West Nile, SARS, chikungunya, MERS-CoV, Ebola, Zika and Yellow Fever raised some questions on quickness and reliability of laboratory diagnostic tests for verification of suspected cases. Since sampling of blood requires medically trained personal and comprises some risks for the patient as well as for the health care personal, the sampling by non-invasive methods (e.g. saliva and/ or urine) might be a very valuable alternative for investigating a diseased patient.

MAIN BODY

To analyse the usefulness of alternative non-invasive samples for the diagnosis of emerging infectious viral diseases, a literature search was performed on PubMed for alternative sampling for these viral infections. In total, 711 papers of potential relevance were found, of which we have included 128 in this review.

CONCLUSIONS

Considering the experience using non-invasive sampling for the diagnostic of emerging viral diseases, it seems important to perform an investigation using alternative samples for routine diagnostics. Moreover, during an outbreak situation, evaluation of appropriate sampling and further processing for laboratory analysis on various diagnostic platforms are very crucial. This will help to achieve optimal diagnostic results for a good and reliable case identification.

Bethony J. Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis

The diagnosis of strongyloidiasis by coprological methods has a low sensitivity, underestimating the prevalence of Strongyloides stercoralis in endemic areas. Serodiagnostic tests for strongyloidiasis have shown robust diagnostic properties. However, these methods require a blood draw, an invasive and labor-intensive sample collection method, especially in the resource-limited settings where S. stercoralis is endemic. Our study examines a urine-based assay for strongyloidiasis and compares its diagnostic accuracy with coprological and serological methods. Receiver operating characteristic (ROC) curve analyses determined the diagnostic sensitivity (D-Sn) and specificity (D-Sp) of the urine ELISA, as well as estimates its positive predictive value and diagnostic risk. The likelihood ratios of obtaining a positive test result (LR+) or a negative test result (LR-) were calculated for each diagnostic positivity threshold. The urine ELISA assay correlated significantly with the serological ELISA assay for strongyloidiasis, with a D-Sn of 92.7% and a D-Sp of 40.7%, when compared to coprological methods. Moreover, the urine ELISA IgG test had a detection rate of 69%, which far exceeds the coprological method (28%). The likelihood of a positive diagnosis of strongyloidiasis by the urine ELISA IgG test increased significantly with increasing units of IgG detected in urine. The urine ELISA IgG assay for strongyloidiasis assay has a diagnostic accuracy comparable to serological assay, both of which are more sensitive than coprological methods. Since the collection of urine is easy and non-invasive, the urine ELISA IgG assay for strongyloidiasis could be used to screen populations at risk for strongyloidiasis in S. stercoralis endemic areas.

Accuracy of immunoglobulin M and immunoglobulin A of saliva in early diagnosis of dengue: Systematic Review and Meta-analysis

The objective of the study was to conduct a systematic review to synthesize the current evidence on the accuracy of IgM and IgA to early diagnosis the dengue virus. The review protocol was registered at PROSPERO (CRD 42015024808). We searched for studies in the following electronic database from 1990 to January 2018. The search identified 3507 studies. Five studies were included for quantitative analysis. Three studies included evaluations of salivary IgM provided a sensitivity of 86% and specificity of 93%. Two studies included evaluating of IgA salivary showed a combined sensitivity of 69% and a combined specificity of 98%. Despite the results found and the low methodological quality of the studies included in the meta-analysis it is still soon to claim that IgA is better than IgM to diagnosis Dengue.

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.

PCA-MLP SVM distinction of salivary Raman spectra of dengue fever infection

Dengue fever (DF) is a disease of major concern caused by flavivirus infection. Delayed diagnosis leads to severe stages, which could be deadly. Of recent, non-structural protein (NS1) has been acknowledged as a biomarker, alternative to immunoglobulins for early detection of dengue in blood. Further, non-invasive detection of NS1 in saliva makes the approach more appealing. However, since its concentration in saliva is less than blood, a sensitive and specific technique, Surface Enhanced Raman Spectroscopy (SERS), is employed. Our work here intends to define an optimal PCA-SVM (Principal Component Analysis-Support Vector Machine) with Multilayer Layer Perceptron (MLP) kernel model to distinct between positive and negative NS1 infected samples from salivary SERS spectra, which, to the best of our knowledge, has never been explored. Salivary samples of DF positive and negative subjects were collected, pre-processed and analyzed. PCA and SVM classifier were then used to differentiate the SERS analyzed spectra. Since performance of the model depends on the PCA criterion and MLP parameters, both are examined in tandem. Its performance is also compared to our previous works on simulated NS1 salivary samples. It is found that the best PCA-SVM (MLP) model can be defined by 95 PCs from CPV criterion with P1 and P2 values of 0.01 and -0.2 respectively. A classification performance of [76.88%, 85.92%, 67.83%] is achieved.

Saliva and viral infections

Over the last 10 years there have been only a handful of publications dealing with the oral virome, which is in contrast to the oral microbiome, an area that has seen considerable interest. Here, we survey viral infections in general and then focus on those viruses that are found in and/or are transmitted via the oral cavity; norovirus, rabies, human papillomavirus, Epstein‐Barr virus, herpes simplex viruses, hepatitis C virus, and HIV. Increasingly, viral infections have been diagnosed using an oral sample (e.g. saliva mucosal transudate or an oral swab) instead of blood or urine. The results of two studies using a rapid and semi‐quantitative lateral flow assay format demonstrating the correlation of HIV anti‐IgG/sIgA detection with saliva and serum samples are presented. When immediate detection of infection is important, point‐of‐care devices that obtain a non‐invasive sample from the oral cavity can be used to provide a first line diagnosis to assist in determining appropriate counselling and therapeutic path for an increasing number of diseases.

Siderophore vaccine conjugates protect against uropathogenic Escherichia coli urinary tract infection

Uropathogenic Escherichia coli (UPEC) is the primary cause of uncomplicated urinary tract infections (UTIs). Whereas most infections are isolated cases, 1 in 40 women experience recurrent UTIs. The rise in antibiotic resistance has complicated the management of chronic UTIs and necessitates new preventative strategies. Currently, no UTI vaccines are approved for use in the United States, and the development of a highly effective vaccine remains elusive. Here, we have pursued a strategy for eliciting protective immunity by vaccinating with small molecules required for pathogenesis, rather than proteins or peptides. Small iron-chelating molecules called siderophores were selected as antigens to vaccinate against UTI for this vaccine strategy. These pathogen-associated stealth siderophores evade host immune defenses and enhance bacterial virulence. Previous animal studies revealed that vaccination with siderophore receptor proteins protects against UTI. The poor solubility of these integral outer-membrane proteins in aqueous solutions limits their practical utility. Because their cognate siderophores are water soluble, we hypothesized that these bacterial-derived small molecules are prime vaccine candidates. To test this hypothesis, we immunized mice with siderophores conjugated to an immunogenic carrier protein. The siderophore-protein conjugates elicited an adaptive immune response that targeted bacterial stealth siderophores and protected against UTI. Our study has identified additional antigens suitable for a multicomponent UTI vaccine and highlights the potential use of bacterial-derived small molecules as antigens in vaccine therapies.

Dengue Specific Immunoglobulin A Antibody is Present in Urine and Associated with Disease Severity

The kinetics of dengue virus (DENV)-specific IgA antibody in urine and the potential correlation with disease severity remain elusive. In this study, 262 serial urine samples from 78 laboratory-confirmed patients were assayed by a commercial immunoglobulin A (IgA) kit against DENV. All cases were classified into dengue fever (DF) and severe dengue (SD) according to the 2009 WHO/TDR guideline. The total positive rate of IgA in urine was 59%. DENV-specific IgA was detected in urine from day 2 to day 13 after the onset of illness in DF patients; While for SD patients, anti-DENV IgA could be detected till day 14. The positive rate of IgA in patients with secondary infection was higher than that in patients with primary infection. Importantly, during 4-7 days after the onset of illness, the IgA positive rate of SD patients was significantly higher than that of DF patients. Especially, the intensity of IgA signal in SD patients was obviously stronger than that in DF patient at the recovery stage. Overall, our results suggested that the existence of DENV-specific IgA antibodies in urine might be a warning sign for the severity of disease and its measurement might provide valuable guidance for proper patient management.

Evaluation of the performances of six commercial kits designed for dengue NS1 and anti-dengue IgM, IgG and IgA detection in urine and saliva clinical specimens

Background

Rapid diagnostic tests (RDTs) have been commercialized in order to help physicians in dengue diagnosis. Until recently, only blood samples were used for those tests but it has been shown in several studies that urine and saliva can also be employed for dengue diagnosis. RDTs for the detection of NS1 antigen and anti-dengue IgG, IgM and IgA in urine and saliva specimens have thus been developed by Standard Diagnostics. The aim of this study was to evaluate the performances these new commercial assays.

Methods

Two panels of clinical specimens were used: one for the evaluation of the NS1-detection devices and the second for the evaluation of the antibody-detection kits. Each panel consisted of urine and saliva specimens collected sequentially from 86 patients with a confirmed dengue infection. A total of 291 saliva and 440 urine samples were included in the NS1-evaluation panel and 530 saliva and 528 urine specimens constituted the antibody-evaluation panel. All samples were tested in parallel by in-house ELISAs and by the commercial RDTs.

Results

The RDTs demonstrated an overall sensitivity of 15.5 %/27.9 %/10.7 % for NS1/IgG/IgA detection in urine samples and 20.4 %/ 34.8 %/11 %/6.2 % for NS1/IgG/IgM/IgA detection in saliva samples. Compared to the in-house NS1 ELISA, the results obtained with the NS1 RDT demonstrated a good correlation with urine samples (kappa coefficient: 0.88) but not with saliva specimens (kappa coefficient: 0.28). RDTs designed for antibody detection in saliva and urine were extremely specific (100 %), but less sensitive than the in-house ELISAs (i.e., reduction of the overall sensitivity by 12.2 % for the RDT designed for IgG detection in urine and by 23.7 % for the RDT detecting anti-DENV IgM in saliva). IgM were not detected in urine, either by RDT or ELISA.

Conclusions

Although the RDTs evaluated here offer an apparently attractive approach for dengue diagnosis, this study suggests that these new commercial kits would require further improvement to increase the sensitivity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1551-x) contains supplementary material, which is available to authorized users.

High prevalence of clinically unsuspected dengue disease among children in Ribeirao Preto city, Brazil

The aim of this study was to analyze the characteristics of Dengue virus (DENV)-infected children and the accuracy of dengue diagnosis based on clinical presentations. The inclusion criteria were children ≥1-year-old presenting febrile illness with 1-7 days of onset. Children (n = 110) aged 2-15 years were included in this study. DENV infection was confirmed with virological tests using serum, salvia, and/or urine samples. The attending pediatricians classified 56/110 (50.91%) of the children as suspected dengue cases. The DENV infection was confirmed by specific laboratory tests in 52/56 (92.9%) of the suspected dengue cases but also in 44/54 (81.5%) of the unsuspected dengue cases; total of 96/110 (87.27%) confirmed dengue cases. The clinical diagnosis gave an overall sensitivity of 54.2% (52/96) and a specificity of 71.4% (10/14). The positive predictive value of the clinical diagnosis was 92.8% and negative predictive value was 18.5%. After the third day of onset of symptoms, the DENV genome detection rate was similar in serum and saliva samples, suggesting that saliva samples represent an alternative to blood samples for early dengue diagnosis. Vaccination against Yellow fever virus did not influence the antibody response against DENV-1, DENV-2, and DENV-3, which circulated during the study period. Although the signs and symptoms were compatible with dengue, the attending pediatricians did not suspect the disease in several children. Therefore, the inclusion of virological tests for early diagnosis in the protocols for dengue surveillance would help in the implementation of prompt treatment of patients and epidemic containment strategies. J. Med. Virol. 88:1711-1719, 2016. © 2016 Wiley Periodicals, Inc.

Performance of Dengue Diagnostic Tests in a Single-Specimen Diagnostic Algorithm

BACKGROUND

Anti-dengue virus (DENV) immunoglobulin M (IgM) seroconversion has been the reference standard for dengue diagnosis. However, paired specimens are rarely obtained, and the interval for this testing negates its usefulness in guiding clinical case management. The presence of DENV viremia and appearance of IgM during the febrile phase of dengue provides the framework for dengue laboratory diagnosis by using a single serum specimen.

METHODS

Archived paired serum specimens (n = 1234) from patients with laboratory-confirmed dengue from 2005 through 2011 were used to determine the diagnostic performance of real-time reverse transcription polymerase chain reaction (RT-PCR), for detection of DENV serotypes 1-4, and enzyme-linked immunosorbent assays (ELISAs), for detection of DENV nonstructural protein 1 (NS1) antigen and anti-DENV IgM.

RESULTS

During 1-3 days after illness onset, real-time RT-PCR and NS1 antigen testing detected 82%-69% and 90%-84% of cases, respectively, as viremia levels declined, while anti-DENV IgM ELISA detected 5%-41% of cases as antibody appeared. Over the 10-day period of the febrile phase of dengue, the cumulative effect of using these 3 types of tests in a diagnostic algorithm confirmed ≥90% of dengue cases.

CONCLUSIONS

The use of molecular or NS1 antigen tests to detect DENV and one to detect anti-DENV IgM in a single serum specimen collected during the first 10 days of illness accurately identified ≥90% of dengue primary and secondary cases.

Recognition of a multiple antigen peptide containing sequence from mimotope of the dengue type 3 virus NS4B protein by human antibodies

OBJECTIVE

To evaluate the recognition of NS4B mimotope, as multiple antigen peptide (MAP), by dengue antibodies presents in serum samples from patients with different serotype infections.

METHODS

A MAP containing mimotope sequence was synthesized and used to evaluate the recognition of NS4B mimotope as MAP by a panel of 66 human sera from dengue cases by an indirect ELISA assay.

RESULTS

The MAP differentiated between sera from dengue viruses infected patients and sera from healthy individuals and the best reactivity was shown by serum from dengue type 3 virus patients. The recognition was more intense with serum from patients with secondary infection.

CONCLUSIONS

The findings suggest the potential use of NS4B mimotope on the development of a multi-epitope diagnostic tool. These results are important for further immunogenicity studies.

Value of Routine Dengue Diagnostic Tests in Urine and Saliva Specimens

Background

Dengue laboratory diagnosis is essentially based on detection of the virus, its components or antibodies directed against the virus in blood samples. Blood, however, may be difficult to draw in some patients, especially in children, and sampling during outbreak investigations or epidemiological studies may face logistical challenges or limited compliance to invasive procedures from subjects. The aim of this study was to assess the possibility of using saliva and urine samples instead of blood for dengue diagnosis.

Methodology/Principal Findings

Serial plasma, urine and saliva samples were collected at several time-points between the day of admission to hospital until three months after the onset of fever in children with confirmed dengue disease. Quantitative RT-PCR, NS1 antigen capture and ELISA serology for anti-DENV antibody (IgG, IgM and IgA) detection were performed in parallel on the three body fluids. RT-PCR and NS1 tests demonstrated an overall sensitivity of 85.4%/63.4%, 41.6%/14.5% and 39%/28.3%, in plasma, urine and saliva specimens, respectively. When urine and saliva samples were collected at the same time-points and tested concurrently, the diagnostic sensitivity of RNA and NS1 detection assays was 69.1% and 34.4%, respectively. IgG/IgA detection assays had an overall sensitivity of 54.4%/37.4%, 38.5%/26.8% and 52.9%/28.6% in plasma, urine and saliva specimens, respectively. IgM were detected in 38.1% and 36% of the plasma and saliva samples but never in urine.

Conclusions

Although the performances of the different diagnostic methods were not as good in saliva and urine as in plasma specimens, the results obtained by qRT-PCR and by anti-DENV antibody ELISA could well justify the use of these two body fluids to detect dengue infection in situations when the collection of blood specimens is not possible.

Dengue is the most important arthropod-borne disease affecting humans and represents a huge public health burden in affected countries. Symptoms are often non-specific hence the need for an early, sensitive and specific diagnosis of dengue for appropriate management as well as for early epidemic detection. Currently, almost all laboratory diagnostic methods require a blood specimen that may be sometimes be difficult or inconvenient to obtain. In this study, we assessed the possibility to use saliva and urine samples as alternatives to blood specimens in dengue diagnosis. We demonstrated that the performances of the different diagnostic methods (RT-PCR, NS1 antigen detection and anti-DENV IgM/IgG/IgA ELISAs) were in general not as good in saliva and urine as in plasma, but that the use of these body fluids obtained by non-invasive methods could be of value in certain circumstances such as outbreak investigations or in young children (once they are old enough to comply to instructions), in addition to the situations when blood cannot be easily collected (e.g., lack of phlebotomist, refusal of the procedure, etc.).

Challenges in the Laboratory Diagnosis and Management of Dengue Infections

Dengue fever is considered the most important arthropod-borne viral diseases in terms of morbidity and mortality. An accurate and efficient diagnosis of dengue plays an important role in case confirmation. The virus may be isolated during the viremic phase (within day 5 of illness), from serum, plasma and peripheral blood mononuclear cells. Enzyme linked immunoassay (ELISA) has demonstrated the presence of high levels of dengue NS1 antigen and tests may be performed by enzyme-immunoassays (EIAs) or immune-chromatographic (ICT) methods. These assays are specific with respect to different flaviviruses. Conventional and real time RT PCR, nested PCR, multiplex PCR and Nucleic acid sequence based amplification (NASBA) have been described as sensitive and relatively rapid method of detecting the virus during the early viremic phase. Other tests used include assay of anti-dengue specific IgM and IgG ELISA. Currently no curative treatment in terms of anti-viral drugs is available for dengue and patients are managed with rest and aggressive supportive therapy. Management may be done at home or in the hospital depending on the severity of the illness. Hospital management includes fluid therapy, blood component transfusion and other modalities of treatments like steroids, recombinant factor VII and management of complications. Various vaccines are in trial stages and may become available in the near future.

Dengue laboratory diagnosis: still some room for improvement

Dengue is the most important and widely distributed arthropod-borne viral disease affecting humans. The number of dengue virus infections has steadily grown and more than 100 countries survey dengue incidence every year. Due to the lack of an approved antiviral treatment or licensed preventative vaccine, accurate and opportune diagnosis is commended for efficient dengue epidemiological surveillance, to propose control measures in order to curtail outbreaks timely and treat patients satisfactorily. In this review, the basis, application and indications for different diagnostic tests are described, and their advantages and limitations considered. At the end of this piece, we speculate what the future may hold for the diagnosis of dengue infections.

Diagnosing dengue virus infection: rapid tests and the role of micro/nanotechnologies

Due to the progressive spread of the dengue virus and a rising incidence of dengue disease, its rapid diagnosis is important for developing countries and of increasing relevance for countries in temperate climates. Recent advances in bioelectronics, micro- and nanofabrication technologies have led to new miniaturized point-of-care devices and analytical platforms suited for rapid detection of infections. Starting from the available tests for dengue diagnosis, this review examines emerging rapid, micro/nanotechnologies-based tools, including label-free biosensor methods, microarray and microfluidic platforms, which hold significant potential, but still need further development and evaluation. The epidemiological and clinical setting as key determinants for selecting the best analytical strategy in patients presenting with fever is then discussed. This review is aimed at the clinicians and microbiologists to deepen understanding and enhance application of dengue diagnostics, and also serves as knowledge base for researchers and test developers to overcome the challenges posed by this disease.

FROM THE CLINICAL EDITOR

Dengue disease remains a significant problem in many developing countries. Unfortunately rapid diagnosis with easy and low cost tests for this disease is currently still not realized. In this comprehensive review, the authors highlighted recent advances in nanotechnology which would enable development in this field, which would result in beneficial outcomes to the population.

Detecting Dengue Virus Nonstructural Protein 1 (NS1) in Urine Samples Using ELISA for the Diagnosis of Dengue Virus Infection

Dengue virus (DENV) infection is a serious global health threat. For the surveillance and control of dengue, there is a need for robust diagnostic tools that are relatively easy to use and reliable in various clinical settings. We investigated the applicability of NS1 antigen detection in urine samples for the diagnosis of DENV. About 118 urine samples, obtained from 96 dengue patients at various phases of disease, were used for this study. NS1 antigen was detected by ELISA in the urine samples obtained from patients after 2-17 days of disease onset. Positive detection rates of NS1 antigen ranged between 13-43%. Based on real-time RT-PCR, positive detection rates of viral genome in the urine samples ranged between 20-33% on days 0 to ≥15. On days 11 to ≥15 after the disease onset, NS1 antigen was detected at similar rates in serum and urine samples. Additionally, NS1 antigen was detected in 2 urine samples, but not in the serum samples, on days 7 and 16 after the onset of the disease. The results confirm the applicability of NS1 antigen detection in urine samples using ELISA to diagnose acute DENV infection and suggests that the assay is potentially useful when only limited amounts of serum samples are available and in limited resource settings.

Evaluation of the diagnostic accuracy of a new dengue IgA capture assay (Platelia Dengue IgA Capture, Bio-Rad) for dengue infection detection

Considering the short lifetime of IgA antibodies in serum and the key advantages of antibody detection ELISAs in terms of sensitivity and specificity, Bio-Rad has just developed a new ELISA test based on the detection of specific anti-dengue IgA. This study has been carried out to assess the performance of this Platelia Dengue IgA Capture assay for dengue infection detection. A total of 184 well-characterized samples provided by the French Guiana NRC sera collection (Laboratory of Virology, Institut Pasteur in French Guiana) were selected among samples collected between 2002 and 2013 from patients exhibiting a dengue-like syndrome. A first group included 134 sera from confirmed dengue-infected patients, and a second included 50 sera from non-dengue infected patients, all collected between day 3 and day 15 after the onset of fever. Dengue infection diagnoses were all confirmed using reference assays by direct virological identification using RT-PCR or virus culture on acute sera samples or on paired acute-phase sera samples of selected convalescent sera. This study revealed: i) a good overall sensitivity and specificity of the IgA index test, i.e., 93% and 88% respectively, indicating its good correlation to acute dengue diagnosis; and ii) a good concordance with the Panbio IgM capture ELISA. Because of the shorter persistence of dengue virus-specific IgA than IgM, these results underlined the relevance of this new test, which could significantly improve dengue diagnosis accuracy, especially in countries where dengue virus is (hyper-) endemic. It would allow for additional refinement of dengue diagnostic strategy.

Dengue

Dengue viruses have spread rapidly within countries and across regions in the past few decades, resulting in an increased frequency of epidemics and severe dengue disease, hyperendemicity of multiple dengue virus serotypes in many tropical countries, and autochthonous transmission in Europe and the USA. Today, dengue is regarded as the most prevalent and rapidly spreading mosquito-borne viral disease of human beings. Importantly, the past decade has also seen an upsurge in research on dengue virology, pathogenesis, and immunology and in development of antivirals, vaccines, and new vector-control strategies that can positively impact dengue control and prevention.

Approach to non-invasive sampling in dengue diagnostics: exploring virus and NS1 antigen detection in saliva and urine of travelers with dengue

BACKGROUND

Dengue diagnostics currently relies on serum and plasma tests. Although the proof of concept for detecting dengue virus (DENV) RNA and nonstructural protein 1 (NS1) antigen from urine and saliva has been demonstrated, few studies have explored their use in diagnostics.

OBJECTIVES

To investigate the occurrence, excretion kinetics, and diagnostic potential of DENV-RNA and NS1 antigen in the urine and saliva of dengue patients.

STUDY DESIGN

We examined serial serum, urine (n=50) and saliva (n=48) samples of 14 Finnish travelers with dengue. All samples were analyzed by NS1 ELISA and DENV RT-PCR, and the first and last serum specimens were tested for DENV IgG and IgM. In addition, biochemical parameters were studied from the urine and clinical and laboratory data of the patients were collected.

RESULTS

DENV-NS1 protein and RNA proved detectable from saliva and urine using tests developed for serum samples. RNA/NS1 detection showed a diagnostic sensitivity of 64%/54% and 60%/56% for urine and saliva, respectively. RNA analyses performed on days 7-13 after onset of symptoms revealed the sensitivity for urine (72%) to be greater than for serum (31%) or saliva (50%). The concentration of urine samples had no impact on RNA detection.

CONCLUSIONS

Noninvasive sampling enables an alternative approach to dengue diagnostics. The performance of the NS1 antigen assay may be improved by optimizing it for urine and saliva samples. The prolonged excretion of DENV-RNA in urine extends the sampling time window for molecular diagnostics and surveillance.

Diagnostic efficacy of saliva for dengue - a reality in near future? A piloting initiative

BACKGROUND

Dengue, a mosquito-transmitted viral infection presents variable symptoms, including death. Due to their increasing incidences, early detection and improved diagnoses of severe cases are of prime importance. Currently, viral antigens and antibodies are detected by traditional serological tests. However, the introduction of oral fluid as an alternative, has led to many researches. Hence, this prompted us to carry out a pilot study to evaluate the diagnostic efficacy of saliva in detecting dengue antibody by using Enzyme Linked Immunosorbent Assay (ELISA).

AIM AND OBJECTIVES

To evaluate the presence of Dengue antibody in saliva and its sensitivity and specificity through ELISA.

METHODOLOGY AND RESULTS

Twenty seropositive patients and twenty seronegative patients of Dengue were considered individually. Saliva samples collected from these patients were subjected to ELISA test for detection of Dengue antibody. A sensitivity of 100% and a specificity of 100% were obtained for making a diagnosis of Dengue infection.

CONCLUSION

Many studies have been conducted by utilizing saliva as a diagnostic tool, especially in western population. Its advantages over venipuncture are many, especially as it is less invasive, safe, less expensive and as it allows large numbers of samples to be collected easily for screening and epidemiological purposes. In a developing tropical country like India, such a diagnostic tool has to be encouraged. Further research necessitates the implementation of saliva as a diagnostic tool.

Kinetics of dengue non-structural protein 1 antigen and IgM and IgA antibodies in capillary blood samples from confirmed dengue patients

Large-scale epidemiological surveillance of dengue in the field and dengue patient management require simple methods for sample collection, storage, and transportation as well as effective diagnostic tools. We evaluated the kinetics of three biological markers of dengue infection-non-structural protein 1 (NS1) antigen, immunoglobulin M (IgM), and IgA-in sequential capillary blood samples collected from fingertips of confirmed dengue patients. The overall sensitivities and specificities of the tests were 96% and 100%, respectively, for NS1, 58.1% and 100%, respectively, for IgM, and 33% and 100%, respectively, for IgA. During the acute phase of the disease, NS1 was the best marker of dengue infection, with a sensitivity of 98.7%, whereas from day 5, all three markers exhibited relevant levels of sensitivity. This first descriptive study of the kinetics of biological markers of dengue in capillary blood samples confirms the usefulness of this biological compartment for dengue diagnosis and argues for its exploitation in community-level and remote settings.

Variation in dengue virus plaque reduction neutralization testing: systematic review and pooled analysis

Background

The plaque reduction neutralization test (PRNT) remains the gold standard for the detection of serologic immune responses to dengue virus (DENV). While the basic concept of the PRNT remains constant, this test has evolved in multiple laboratories, introducing variation in materials and methods. Despite the importance of laboratory-to-laboratory comparability in DENV vaccine development, the effects of differing PRNT techniques on assay results, particularly the use of different dengue strains within a serotype, have not been fully characterized.

Methods

We conducted a systematic review and pooled analysis of published literature reporting individual-level PRNT titers to identify factors associated with heterogeneity in PRNT results and compared variation between strains within DENV serotypes and between articles using hierarchical models.

Results

The literature search and selection criteria identified 8 vaccine trials and 25 natural exposure studies reporting 4,411 titers from 605 individuals using 4 different neutralization percentages, 3 cell lines, 12 virus concentrations and 51 strains. Of 1,057 titers from primary DENV exposure, titers to the exposure serotype were consistently higher than titers to non-exposure serotypes. In contrast, titers from secondary DENV exposures (n = 628) demonstrated high titers to exposure and non-exposure serotypes. Additionally, PRNT titers from different strains within a serotype varied substantially. A pooled analysis of 1,689 titers demonstrated strain choice accounted for 8.04% (90% credible interval [CrI]: 3.05%, 15.7%) of between-titer variation after adjusting for secondary exposure, time since DENV exposure, vaccination and neutralization percentage. Differences between articles (a proxy for inter-laboratory differences) accounted for 50.7% (90% CrI: 30.8%, 71.6%) of between-titer variance.

Conclusions

As promising vaccine candidates arise, the lack of standardized assays among diagnostic and research laboratories make unbiased inferences about vaccine-induced protection difficult. Clearly defined, widely accessible reference reagents, proficiency testing or algorithms to adjust for protocol differences would be a useful first step in improving dengue PRNT comparability and quality assurance.

Fine scale spatiotemporal clustering of dengue virus transmission in children and Aedes aegypti in rural Thai villages

BACKGROUND

Based on spatiotemporal clustering of human dengue virus (DENV) infections, transmission is thought to occur at fine spatiotemporal scales by horizontal transfer of virus between humans and mosquito vectors. To define the dimensions of local transmission and quantify the factors that support it, we examined relationships between infected humans and Aedes aegypti in Thai villages.

METHODOLOGY/PRINCIPAL FINDINGS

Geographic cluster investigations of 100-meter radius were conducted around DENV-positive and DENV-negative febrile "index" cases (positive and negative clusters, respectively) from a longitudinal cohort study in rural Thailand. Child contacts and Ae. aegypti from cluster houses were assessed for DENV infection. Spatiotemporal, demographic, and entomological parameters were evaluated. In positive clusters, the DENV infection rate among child contacts was 35.3% in index houses, 29.9% in houses within 20 meters, and decreased with distance from the index house to 6.2% in houses 80-100 meters away (p<0.001). Significantly more Ae. aegypti were DENV-infectious (i.e., DENV-positive in head/thorax) in positive clusters (23/1755; 1.3%) than negative clusters (1/1548; 0.1%). In positive clusters, 8.2% of mosquitoes were DENV-infectious in index houses, 4.2% in other houses with DENV-infected children, and 0.4% in houses without infected children (p<0.001). The DENV infection rate in contacts was 47.4% in houses with infectious mosquitoes, 28.7% in other houses in the same cluster, and 10.8% in positive clusters without infectious mosquitoes (p<0.001). Ae. aegypti pupae and adult females were more numerous only in houses containing infectious mosquitoes.

CONCLUSIONS/SIGNIFICANCE

Human and mosquito infections are positively associated at the level of individual houses and neighboring residences. Certain houses with high transmission risk contribute disproportionately to DENV spread to neighboring houses. Small groups of houses with elevated transmission risk are consistent with over-dispersion of transmission (i.e., at a given point in time, people/mosquitoes from a small portion of houses are responsible for the majority of transmission).

Commercial dengue rapid diagnostic tests for point-of-care application: recent evaluations and future needs?

Dengue fever, dengue haemorrhagic fever, and dengue shock syndrome (DF/DHF/DSS) are tropical diseases that cause significant humanitarian and economic hardship. It is estimated that more than 2.5 billion people are at risk of infection and more than 100 countries have endemic dengue virus transmission. Laboratory tests are essential to provide an accurate diagnosis of dengue virus infection so that appropriate treatment and patient management may be administered. In many dengue endemic settings, laboratory diagnostic resources are limited and simple rapid diagnostic tests (RDTs) provide opportunities for point-of-care diagnosis. This paper addresses current issues relating to the application of commercial dengue RDTs for the diagnosis of acute dengue virus infection, recent diagnostic evaluations, and identifies future needs.

Evaluation of a novel commercial rapid test for dengue diagnosis based on specific IgA detection

The performance of the novel commercial test ASSURE® Dengue IgA Rapid test (MP Diagnostics) was evaluated using a panel of 172 sera collected from dengue patients and 47 sera from healthy blood donors. The overall specificity and sensitivity were 61.0% and 85.1%, respectively. However, the positivity rate for IgA went from 33.3% for sera collected the same day of fever onset to 81.2% for sera collected 5 days after fever onset. Infections with serotype 2 viruses were detected more efficiently than those with serotype 1 viruses, and no sera from infections with serotypes 3 and 4 were available. In addition, the kit was twice more efficient at detecting secondary infections than at detecting primary infections. Finally, the ASSURE® test showed good repeatability and reproducibility. The results of this study suggest that the ASSURE® Dengue IgA Rapid test may become a useful and easy-to-use test for early dengue diagnosis.

Detection of dengue virus genome in urine by real-time reverse transcriptase PCR: a laboratory diagnostic method useful after disappearance of the genome in serum

The reemergence of dengue virus (DENV) infection has created a requirement for improved laboratory diagnostic procedures. In this study, DENV genome detection in urine was evaluated as a diagnostic method. The DENV genome was detected by real-time reverse transcriptase PCR (RT-PCR) in urine and serum of dengue patients. The detection rate of DENV genome in urine was 25% (2/8) on disease days 0 to 3 and 32% (7/22) on days 4 to 5. The rate was 50% or higher on days 6 to 16, 52% (11/21) on days 6 to 7, 78% (7/9) on days 8 to 9, 80% (4/5) on days 10 to 11, 50% (2/4) on days 12 to 13, and 60% (3/5) on days 14 to 16. The last positive urine sample was on day 16. The detection rates in serum were highest on days 0 to 3 and were greater than 50% on days 0 to 7. Detection rates decreased thereafter, and the last positive detection was on day 11. These results indicate that the time frames for positive detection differ between urine and serum samples, whereby detection rates of 50% or higher are evident between days 6 to 16 for urine samples and days 0 to 7 for serum samples. Nucleotide sequences of PCR products were identical between urine and serum samples. The detection of DENV genome in urine samples by real-time RT-PCR is useful to confirm DENV infection, particularly after viremia disappears.

Development of ASSURE Dengue IgA Rapid Test for the Detection of Anti-dengue IgA from Dengue Infected Patients

Background:

Rapid and early dengue diagnosis is essential for patient management and early disease intervention. MP Diagnostics ASSURE^® Dengue IgA Rapid Test (Dengue IgA RT) was developed for the rapid detection of anti-dengue IgA in patients’ biological samples. The performance of Dengue IgA RT was examined using multiple categories of well-characterized samples.

Materials and Methods:

Dengue IgA RT was designed and developed. Following characterization of samples by reference ELISAs, the performance of the kit was evaluated.

Results:

The overall sensitivity and specificity of Dengue IgA RT were 86.70% (n=233) and 86.05% (n=681) respectively; in which Dengue IgA RT detected 77.42% primary and 92.86% secondary cases; compared to 70.97% and 72.14% by IgM-Cap ELISA and 89.25% and 20% by Non-Structural Protein 1 (NS1) Ag ELISA respectively. Using 125 paired samples, Dengue IgA RT showed 84.80% sensitivity at acute phase and 99.20% sensitivity at convalescent phase; with 92% specificity at both phases. Dengue IgA RT also demonstrated a consistent performance (sensitivity: 85.53%, specificity: 80%) with 76 whole blood samples. In detecting all four serotypes of DENV (n=162), the performance of Dengue IgA RT was comparable with in-house IgM-Cap ELISA. Kinetics of anti-dengue IgA production was elucidated with 42.86% detection level as early as one-two days after fever onset, which increased to 83.33% between five and seven days after fever onset.

Conclusion:

Dengue IgA RT demonstrated a good performance and is applicable as one of the dengue early diagnostic tools at all levels of health care system.

Estimation of dengue virus IgM persistence using regression analysis

Dengue virus IgM persistence was estimated using follow-up sera from 98 patients (60 with primary infections and 38 with secondary infections) whose first-specimen IgM index was strongly positive, suggesting recent disease onset. Regression analysis of the follow-up IgM index versus days between samples yielded a trend line that reached the cut-point index (1.10) at 179 days for the primary infection group and 139 days for the secondary infection group. This difference reflected significantly higher first-sample IgM indices in primary infections than in secondary infections rather than differences in IgM decay rates.