Anti-dengue IgG Antibodies Research Articles

Dengue virus transmission during non-outbreak period in Dar Es Salaam, Tanzania: a cross-sectional survey

BackgroundTanzania has experienced multiple dengue outbreaks between 2010 and 2019, caused by various dengue virus (DENV) strains. In 2019, there were 6917 confirmed dengue cases and 13 deaths in Tanzania. Routine diagnosis of dengue fever is unfortunately excluded, particularly during non-outbreak periods, resulting in delayed outbreak detection and control. The aim of this study was to improve early detection and control measures for DENV by investigating its circulation in human and Aedes aegypti (A.aegypti) mosquitoes during the non-outbreak periods in Dar es Salaam, Tanzania, which is an area frequently affected by dengue outbreaks.MethodsFour hundred and fifteen (415) blood samples were collected from patients attending randomly selected health facilities in five wards; Azimio, Keko, Mtoni, Mbagala and Chamazi within Temeke district. The samples were tested for DENV NS1 antigen and anti-dengue IgM and IgG antibodies by rapid test. Then, 150 out of 415 blood samples were tested for the DENV by conventional Reverse Transcriptase Polymerase Chain Reaction (RT-PCR). Two thousand two hundred and fifty (2,250) adult female A.aegypti mosquitoes were collected using a Prokopack aspirator and BG sentinel trap or obtained after rearing immature stages and tested, in pools of 15 for DENV by RT-PCR. Statistical Software, SPSS version 23, was used for data analysis.ResultsOf the tested blood samples, 17% (71/415) were positive by NS1 antigen, 0.5% (2/415) by IgM, 0.5% (2/415) by IgG antibodies, and 0.5% (2/415) by IgM and IgG. None of the samples tested positive by DENV RT-PCR. Moreover, 3.3% (5/150) of tested mosquito pools had DENV by RT-PCR. Individuals aged between 21 and 40 years of age had increased risk of testing positive for DENV NS1 antigen, followed by those aged 5–20 years old, particularly those residing from Azimio ward, Keko ward, Mtoni ward and Mbagala ward, p-value ≤ 0.05.ConclusionFindings from this study revealed evidence of DENV circulation during non-outbreak periods in Dar es Salaam, Tanzania. These findings underscore the importance of including testing for dengue infection in routine differential diagnoses of febrile cases, and also frequent dengue surveillance in mosquitos. This proactive approach will help early DENV outbreak detection and control in the country.

IgG, IgM, and Nonstructural Protein 1 Response Profiles after Receipt of Tetravalent Dengue Vaccine TAK-003 in a Phase 2 Randomized Controlled Trial.

The profiles of vaccine-induced dengue antibodies may differ from those produced following natural infection and could potentially interfere with the interpretation of diagnostic tests. We assessed anti-dengue IgG and IgM antibodies, and nonstructural protein 1 antigen profiles in the serum of adults who received a single dose of the tetravalent dengue vaccine TAK-003 as either an initially developed high-dose formulation or the standard approved formulation in a phase 2 study in Singapore (#NCT02425098). Immunoglobulin G and IgM profiles during the first 30 days postvaccination varied by baseline serostatus (microneutralization assay). Nonstructural protein 1 antigen was not detected in the serum of any participants. Vaccine-induced IgG and IgM antibodies can affect serological confirmation of subsequent dengue infection in vaccinees. These results highlight the limitations of using serological tests for dengue diagnosis, particularly in a postvaccination setting, and emphasize the need for more sensitive antigen- and molecular-based testing for accurate dengue diagnosis.

Seroprevalence of dengue IgG and associated risk factors in symptomatic and asymptomatic adults in Posadas (Misiones, Argentina), 2017-2019

BackgroundDengue represents a major public health problem in the Americas in general, and in Posadas (Misiones, Argentina) in particular. This study aimed to assess the seroprevalence of dengue virus infection, analyze associated factors, and determine the proportion of asymptomatic cases. MethodsThis prospective cross-sectional study took place from November 2017 to April 2019 in the High Complexity Laboratory of Misiones, at the School Hospital Dr. Ramón Madariaga in Posadas. A random sample of 301 adults (≥ 15 years) was selected from the electoral registry and stratified by geographical area of residence. Sociodemographic, clinical, and laboratory data were collected by means of a survey and serology. Results were analyzed using multivariable logistic regression. ResultsThe median age of the sample was 33 years; 66% were women, and 46.5% had completed at least secondary school. Anti-dengue IgG antibodies were present in 40.2% of the sample (95% confidence interval [CI] 34.5–45.9%), including 90% of those who reported dengue and 20.5% who did not (odds ratio [OR] 33.25, 95% CI 15.46–71.51, p < 0.001). In the multivariable analysis, adjusted for age, group, gender, and vaccination against yellow fever, seropositivity was associated with having relatives with dengue (adjusted OR 3.96, 95% CI 2.18–7.23; p < 0.001). ConclusionSeroprevalence for dengue in Posadas was higher than estimates based on the notification records, and there was a high proportion of asymptomatic cases. Educational level and having a family member who had suffered from dengue were associated with positive serology.

The burden of dengue and force of infection among children in Kerala, India; seroprevalence estimates from Government of Kerala-WHO Dengue study

Dengue shows high geographic heterogeneity within and across endemic countries. In the context of increasing burden and predicted outbreaks due to climate change, understanding the heterogeneity will enable us to develop region specific targeted interventions, including vaccination. World Health Organisation (WHO) suggests standard methodologies to study the burden and heterogeneity at national and subnational levels. Regional studies with robust and standard methodology to capture heterogeneity are scarce. We estimated the seroprevalence of dengue in children aged 9-12 years and the force of infection in Kerala, India, from where Zika cases also have been reported recently. We conducted a school-based cross-sectional survey in 38 clusters; selected by stratified random sampling, representing rural, urban, high burden and low-burden administrative units. Validation of Indirect IgG ELISA was done by Plaque Reduction Neutralization Test (PRNT90) using the local isolates of all four serotypes. Force of infection (FOI) was estimated using the WHO-FOI calculator. We conducted a follow-up survey among a subsample of seronegative children, to estimate the rate of sero-conversion. Among 5236 children tested, 1521 were positive for anti-dengue IgG antibody. The overall seroprevalence in the state was 29% (95% CI 24.1-33.9). The validity corrected seroprevalence was 30.9% in the overall sample, 46.9% in Thiruvananthapuram, 26.9% in Kozhikkode and 24.9% in Kollam. Age-specific seroprevalence increased with age; 25.7% at 9 years, 29.5% at 10 years, 30.9% at 11 years and 33.9% at 12 years. Seroprevalence varied widely across clusters (16.1%-71.4%). The estimated force of infection was 3.3/100 person-years and the seroconversion rate was 4.8/100 person-years. 90% of children who tested positive were not aware of dengue infection. All the four serotypes were identified in PRNT and 40% of positive samples had antibodies against multiple serotypes. The study validates the WHO methodology for dengue serosurveys and confirms its feasibility in a community setting. The overall seroprevalence in the 9-12 year age group is low to moderate in Kerala; there are regional variations; high burden and low burden clusters co-exist in the same districts. The actual burden of dengue exceeds the reported numbers. Heterogeneity in prevalence, the high proportion of inapparent dengue and the hyperendemic situation suggest the need for region-specific and targeted interventions, including vaccination. World Health Organization.

Performance of VIDAS® Diagnostic Tests for the Automated Detection of Dengue Virus NS1 Antigen and of Anti-Dengue Virus IgM and IgG Antibodies: A Multicentre, International Study

Dengue is a serious mosquito-transmitted disease caused by the dengue virus (DENV). Rapid and reliable diagnosis of DENV infection is urgently needed in dengue-endemic regions. We describe here the performance evaluation of the CE-marked VIDAS® dengue immunoassays developed for the automated detection of DENV NS1 antigen and anti-DENV IgM and IgG antibodies. A multicenter concordance study was conducted in 1296 patients from dengue-endemic regions in Asia, Latin America, and Africa. VIDAS® dengue results were compared to those of competitor enzyme-linked immunosorbent assays (ELISA). The VIDAS® dengue assays showed high precision (CV ≤ 10.7%) and limited cross-reactivity (≤15.4%) with other infections. VIDAS® DENGUE NS1 Ag showed high positive and negative percent agreement (92.8% PPA and 91.7% NPA) in acute patients within 0-5 days of symptom onset. VIDAS® Anti-DENGUE IgM and IgG showed a moderate-to-high concordance with ELISA (74.8% to 90.6%) in post-acute and recovery patients. PPA was further improved in combined VIDAS® NS1/IgM (96.4% in 0-5 days acute patients) and IgM/IgG (91.9% in post-acute patients) tests. Altogether, the VIDAS® dengue NS1, IgM, and IgG assays performed well, either alone or in combination, and should be suitable for the accurate diagnosis of DENV infection in dengue-endemic regions.

Reduction in Anti-Dengue Virus IgG Antibody Levels with the Use of a Larvicide for Vector Control in Rural Lao People's Democratic Republic.

The Lao People's Democratic Republic is an endemic area of dengue, with cases reported in urban and rural areas every year. In this study, we indirectly evaluated the efficacy of a larvicide (SumiLarvTM 2MR discs) that was used for vector control against Aedes mosquitoes. Villages in a rural area of Lao PDR were selected as study areas, non-intervention and intervention villages. At the intervention village, the larvicide was used to treat refillable water containers for 27 months (October 2017 to February 2020), while at the non-intervention villages were no treatment. The serum samples of villagers from both villages were randomized to collect in the pre-intervention and in post-intervention periods. An enzyme-linked immunosorbent assay (ELISA) was used to examine anti-dengue virus (DENV) IgG antibody levels in serum samples. Recombinant DENV serotype 2 non-structural protein1 was used as an antigen for the ELISA, the optical density (OD) values were analyzed for comparison. The results showed that the OD values decreased significantly (p &lt; 0.01) between the pre-intervention and post-intervention periods at the intervention site. The treatment of water storage containers in rural areas with SumiLarvTM 2MR discs may help to protect residents from Aedes mosquito bites, and hence, reduce DENV infections.

Evaluation of VIDAS® Diagnostic Assay Prototypes Detecting Dengue Virus NS1 Antigen and Anti-Dengue Virus IgM and IgG Antibodies.

Dengue is a serious tropical disease caused by the mosquito-borne dengue virus (DENV). Performant, rapid, and easy-to-use assays are needed for the accurate diagnosis of acute DENV infection. We evaluated the performance of three prototype assays developed for the VIDAS® automated platform to detect dengue NS1 antigen and anti-dengue IgM and IgG antibodies. Positive and negative agreement with competitor enzyme-linked immunosorbent assays (ELISA) and rapid diagnostic tests (RDT) was evaluated in 91 Lao patients (57 adults, 34 children) with acute DENV infection. The VIDAS® NS1 assay showed the best overall agreement (95.6%) with the competitor NS1 ELISA. Both VIDAS® NS1 and NS1 ELISA assays also demonstrated high sensitivity relative to DENV RNA RT-PCR set as gold standard (85.7% and 83.9%, respectively). In contrast, NS1 RDT was less sensitive relative to DENV RNA RT-PCR (72.7%). The overall agreement of VIDAS® IgM and IgG assays with the competitor assays was moderate (72.5% for IgM ELISA, 76.9% for IgG ELISA, and 68.7% for IgM and IgG RDT). In most analyses, test agreements of the VIDAS® assays were comparable in adults and children. Altogether, the VIDAS® dengue prototypes performed very well and appear to be suitable for routine detection of dengue NS1 antigen and anti-dengue IgM/IgG antibodies.

Epidemiology and immuno-molecular status of Nepal dengue outbreak

Background: The emergence and circulation of dengue infection have become one of the major public health concerns in the world with its high prevalence in the sub-tropical and tropical countries. Hundreds of Dengue cases have been reported annually and the shift of serotypes in every year has raised the concern of public health in Nepal. The detection of dengue virus infections and circulation of different serotypes in different areas has a great role for the clinical management of patients, surveillance, and clinical trial assessments in the days to come. Methods and materials: Clinically suspected dengue cases (n = 240) were subjected to sero analysis for anti-dengue IgM, IgG antibody and NS1 antigen followed by IgG end-point ELISA. Viral RNA extraction was performed for all samples using the Qiagen kit. cDNA was prepared, and RT-PCR was performed using D1 and DencomR2 primers. Dengue Serotyping was done for PCR positive samples using gene-specific primers. Results: Out of 240 dengue suspected cases, male (n = 153/63.75%), female (n = 87/36.25%) and children below 10 years (6.25%) were diagnosed as positive by ELISA. NS1 (59.16%), IgM (33%) and IgG (7.9%) were detected by ELISA, however, only 14 samples were positive alone to each test. Most of the cases were found to be of primary infection. Antibody level for each serum was calculated and categorized as high (43228.70), medium and low (953.53). Only 35.83% of the suspected cases were confirmed positive for dengue virus by PCR and were of Dengue Serotype-1 in the year 2016 in Nepal. Conclusion: The single test alone could not be confirmatory as only 35.83% of the clinically suspected cases were confirmed for Dengue virus infection by PCR. This implies that confirmatory tests like PCR should be coupled with the ELISA results for the proper diagnosis and management of the disease.

Association of serum C-reactive protein level and polymorphisms with susceptibility to dengue infection and severe clinical outcome among eastern Indian patients.

Dengue virus (DENV) infection is a major public health concern in India ranging from simple febrile illness to severe outcome. This study aimed to investigate association of serum CRP level and CRP gene polymorphisms towards development of dengue disease susceptibility and severity among eastern Indian patients. Blood was collected from 348 symptomatic patients. Sera was subjected to serological diagnosis for the presence of anti-dengue IgM, anti-dengue IgG antibodies and dengue NS1 antigen by ELISA. Viral RNA was extracted and the presence of DENV genome, viral load, serotypes was determined by qRT-PCR. CRP level and polymorphisms were determined by immunoturbidimetry and polymerase chain reaction-restriction fragment length polymorphism, respectively. Statistical analysis was performed by GraphPad-Prism. Among 206 dengue patients, CRP level increased significantly among patients within acute phase, and patients with qRT-PCR/NS1 antigen positivity, high viral load (HVL), secondary infection, and DENV4 and DENV2 infections. rs3091244, TT genotype positively associated with dengue susceptibility (p = 0.03). CT genotype of rs3093059 and TT genotype of rs3091244 were found to correlate with elevated CRP level and development of WHO-defined warning signs. TT genotype of rs3091244 was more prevalent among HVL patients. Thus, these CRP polymorphic variants and CRP concentration might act as potential prognostic biomarkers for predicting disease severity among acute-stage dengue patients.

Laser scanning optical investigations of dengue virus infection from antibody fluorescence of human blood

Dengue is the most important arthropod-borne viral disease of public health significance today, and the geographic distribution includes more than 100 countries worldwide. A definite diagnosis of dengue virus infection is based on clinical criteria supported by antibody tests of whole blood. In this study, we report on dengue infected whole blood diagnostics using laser scanning confocal microscopy (LSCM) over a laser excitation of 488, 543 and 633 nm wavelengths. Based on our findings, the system has potential applications in the detection and quantification of dengue virus infected cells, antigens and antibodies in blood in vitro. Analysis of about 100 infected patients shows that the primary organism (or pathogen), characteristic of dengue infection, causes a significant biochemical change in the nature of human blood in which it resides, and, due to which, fluorescence increases in dengue samples. Thus, the use of a reliable and sensitive rapid diagnostic test using LSCM can simultaneously detect the presence of anti-dengue IgG and IgM antibodies, which is a breakthrough in diagnosis and of great clinical use. The antibodies for dengue continue to be distinguishable for a couple of months after infection. This change in blood fluorescence may be a significant contribution from light scattering through antibodies produced against the dengue antigen.

Seroprevalence of dengue fever and the associated sociodemographic, clinical, and environmental factors in Makkah, Madinah, Jeddah, and Jizan, Kingdom of Saudi Arabia

This study aimed to estimate the seroprevalence of anti-dengue IgG antibodies in Makkah, Al Madinah, Jeddah, and Jizan; and to identify the associated demographic, clinical, and environmental independent risk factors. A community-based household serosurvey conducted between September 20, 2016 and January 31, 2017. A multi-stage stratified cluster sampling was used to select 6596 participants from Makkah, Madinah, Jeddah, and Jizan. Blood samples were drawn from all participants to detect anti-dengue IgG antibodies. A semi-structured questionnaire was used to collect information on demographic, clinical, and environmental data. Multivariate logistic regression was carried out to identify independent risk factors of dengue seropositivity. The dengue seroprevalence (95% confidence intervalI) was 26.7% (25.6%, 27.8%), with the highest (33.6%) and lowest (14.8%) rates in Jizan and Madinah, respectively, and reaching 50% or more in several districts of the four cities. Demographic predictors of seroprevalence included: dwelling in Makkah (odds ratio [OR] = 2.19, p < 0.001) or Jizan (OR = 2.17, p < 0.001); older age (OR = 3.91, p < 0.001 for age>30 years); housing type (OR = 1.84 and 1.82, p < 0.001 for popular and social houses, respectively); and number of household occupants (OR = 0.86 and 0.71 for 6–10 [p = 0.042] and 11–20 [p = 0.002] occupants, respectively). Environmental predictors included the absence of pest control works in residency area (OR = 1.39, p = 0.002), presence of mosquitoes in the home (OR = 1.39, p = 0.001), and absence of awareness campaigns (OR = 1.97, p < 0.001). One in four inhabitants of the Western region of Saudi Arabia was seropositive for the dengue virus. Implementation of behavior-based educational programs is recommended, involving the population in the identification and eradication of vector sources and promoting appropriate behaviors that prevent the spread.

Dengue seroprevalence and force of primary infection in a representative population of urban dwelling Indonesian children.

BackgroundIndonesia reports the second highest dengue disease burden in the world; these data are from passive surveillance reports and are likely to be significant underestimates. Age-stratified seroprevalence data are relatively unbiased indicators of past exposure and allow understanding of transmission dynamics.Methodology/Principal FindingsTo better understand dengue infection history and associated risk factors in Indonesia, a representative population-based cross-sectional dengue seroprevalence study was conducted in 1–18-year-old urban children. From October to November 2014, 3,210 children were enrolled from 30 geographically dispersed clusters. Serum samples were tested for anti-dengue IgG antibodies by indirect ELISA. A questionnaire investigated associations between dengue serologic status and household socio-demographic and behavioural factors. Overall, 3,194 samples were tested, giving an adjusted national seroprevalence in this urban population of 69.4% [95% CI: 64.4–74.3] (33.8% [95% CI: 26.4–41.2] in the 1–4-year-olds, 65.4% [95% CI: 69.1–71.7] in the 5–9-year-olds, 83.1% [95% CI: 77.1–89.0] in the 10–14-year-olds, and 89.0% [95% CI: 83.9–94.1] in the 15–18-year–olds). The median age of seroconversion estimated through a linear model was 4.8 years. Using a catalytic model and considering a constant force of infection we estimated 13.1% of children experience a primary infection per year. Through a hierarchical logistic multivariate model, the subject’s age group (1–4 vs 5–9 OR = 4.25; 1–4 vs. 10–14 OR = 12.60; and 1–4 vs 15–18 OR = 21.87; p<0.0001) and the number of cases diagnosed in the household since the subject was born (p = 0.0004) remained associated with dengue serological status.Conclusions/SignificanceThis is the first dengue seroprevalence study in Indonesia that is targeting a representative sample of the urban paediatric population. This study revealed that more than 80% of children aged 10 years or over have experienced dengue infection at least once. Prospective incidence studies would likely reveal dengue burdens far in excess of reported incidence rates.

Detection of dengue cases by serological testing in a dengue vaccine efficacy trial: Utility for efficacy evaluation and impact of future vaccine introduction

BackgroundDengue diagnosis confirmation and surveillance are widely based on serological assays to detect anti-dengue IgM or IgG antibodies since such tests are affordable/user-friendly. The World Health Organization identified serological based diagnosis as a potential tool to define probable dengue cases in the context of vaccine trials, while acknowledging that this may have to be interpreted with caution. MethodsIn a phase IIb randomized, placebo-controlled trial assessing the efficacy of a tetravalent dengue vaccine (CYD-TDV) in Thai schoolchildren, case definition was based on virological confirmation by either serotype-specific RT-PCRs or by NS1-antigen ELISA (Clinicaltrials.gov NCT00842530). Here, we characterized suspected dengue cases using IgM and IgG ELISA to assess their utility in evaluating probable dengue cases in the context of vaccine efficacy trials, comparing virologically-confirmed and serologically diagnosed dengue in the vaccine and placebo groups. Serologically probable cases were defined as: (1) IgM positive acute- or convalescent-phase samples, or (2) IgG positive acute-phase sample and ≥4-fold IgG increase between acute and convalescent-phase samples. ResultsSerological diagnosis had good sensitivity (97.1%), but low specificity (85.1%) compared to virological confirmation. A high level of false positivity through serology diagnosis particularly in the 2 months post-vaccination was observed, and is most likely related to detection of the immune response to the dengue vaccine. This lack of specificity and bias with vaccination demonstrates the limitation of using IgM and IgG antibody responses to explore vaccine efficacy. ConclusionReliance on serological assessments would lead to a significant number of false positives during routine clinical practice and surveillance following the introduction of the dengue vaccine.

Seroepidemiology of Asymptomatic Dengue Virus Infection in Jeddah, Saudi Arabia.

BACKGROUNDAlthough virologically confirmed dengue fever has been recognized in Jeddah, Saudi Arabia, since 1994, causing yearly outbreaks, no proper seroepidemiologic studies on dengue virus have been conducted in this region. Such studies can define the extent of infection by this virus and estimate the proportion that may result in disease. The aim of this study was to measure the seroprevalence of past dengue virus infection in healthy Saudi nationals from different areas in the city of Jeddah and to investigate demographic and environmental factors that may increase exposure to infection.METHODSSera were collected from 1984 Saudi subjects attending primary health care centers in six districts of Jeddah. These included general patients of various ages seeking routine vaccinations, antenatal care or treatment of different illnesses excluding fever or suspected dengue. A number of blood donors were also tested. Serum samples were tested by enzyme immunoassay (EIA) for IgG antibodies to dengue viruses 1, 2, 3, 4. A questionnaire was completed for each patient recording various anthropometric data and factors that may indicate possible risk of exposure to mosquito bites and dengue infection. Patients with missing data and those who reported a history of dengue fever were excluded from analysis, resulting in a sample of 1939 patients to be analyzed.RESULTSThe overall prevalence of dengue virus infection as measured by anti-dengue IgG antibodies from asymptomatic residents in Jeddah was 47.8% (927/1939) and 37% (68/184) in blood donors. Infection mostly did not result in recognizable disease, as only 19 of 1956 subjects with complete information (0.1%) reported having dengue fever in the past. Anti dengue seropositivity increased with age and was higher in males than females and in residents of communal housing and multistory buildings than in villas. One of the six districts showed significant increase in exposure rate as compared to the others. Availability of public sewage was associated with lower infection at a nearly significant level. No other clear risk factors were identifiable. Infection was not related to travel abroad.CONCLUSIONSOur results indicate a relatively high exposure of Jeddah residents to infection by dengue viruses, which must be considered endemic to this region. Infection largely remained asymptomatic or was only associated with minor illness for which patients did not seek treatment. These results call for continued vigilance for clinical cases of dengue that may arise from this wide exposure. They also call for more extensive control efforts to reduce exposure to and transmission of dengue viruses.

A novel dengue virus serotype-2 nanovaccine induces robust humoral and cell-mediated immunity in mice

Dengue virus (DENV), a member of the Flaviviridae family, can be transmitted to humans through the bite of infected Aedes mosquitoes. The incidence of dengue has increased worldwide over the past few decades. Inadequate vector control, changing global ecology, increased urbanization, and faster global travel are factors enhancing the rapid spread of the virus and its vector. In the absence of specific antiviral treatments, the search for a safe and effective vaccine grows more imperative. Many strategies have been utilized to develop dengue vaccines. Here, we demonstrate the immunogenic properties of a novel dengue nanovaccine (DNV), composed of ultraviolet radiation (UV)-inactivated DENV-2, which has been loaded into the nanoparticles containing chitosan/Mycobacterium bovis Bacillus Calmette-Guerin cell wall components (CS/BCG-NPs). We investigated the immunogenicity of DNV in a Swiss albino mouse model. Inoculation with various concentrations of vaccine (0.3, 1, 3 and 10μg/dose) with three doses, 15-day apart, induced strong anti-dengue IgM and IgG antibodies in the mouse serum along with neutralizing antibody against DENV-2 reference strain (16681), a clinical-isolate strain (00745/10) and the mouse-adapted New Guinea-C (NGC) strain. Cytokine and chemokine secretion in the serum of DNV-immunized mice showed elevated levels of IFN-γ, IL-2, IL-5, IL-12p40, IL-12p70, IL-17, eotaxin and RANTES, all of which have varying immune functions. Furthermore, we observed a DNV dose-dependent increase in the frequencies of IFN-γ-producing CD4+ and CD8+ T cells after in vitro stimulation of nucleated cells. Based on these findings, DNV has the potential to become a candidate dengue vaccine.

Evidence of dengue virus transmission and factors associated with the presence of anti-dengue virus antibodies in humans in three major towns in Cameroon.

BackgroundDengue is not well documented in Africa. In Cameroon, data are scarce, but dengue infection has been confirmed in humans. We conducted a study to document risk factors associated with anti-dengue virus Immunoglobulin G seropositivity in humans in three major towns in Cameroon.Methodology/Principal FindingsA cross sectional survey was conducted in Douala, Garoua and Yaounde, using a random cluster sampling design. Participants underwent a standardized interview and were blood sampled. Environmental and housing characteristics were recorded. Randomized houses were prospected to record all water containers, and immature stages of Aedes mosquitoes were collected. Sera were screened for anti-dengue virus IgG and IgM antibodies. Risk factors of seropositivity were tested using logistic regression methods with random effects.Anti-dengue IgG were found from 61.4% of sera in Douala (n = 699), 24.2% in Garoua (n = 728) and 9.8% in Yaounde (n = 603). IgM were found from 0.3% of Douala samples, 0.1% of Garoua samples and 0.0% of Yaounde samples. Seroneutralization on randomly selected IgG positive sera showed that 72% (n = 100) in Douala, 80% (n = 94) in Garoua and 77% (n = 66) in Yaounde had antibodies specific for dengue virus serotype 2 (DENV-2).Age, temporary house walls materials, having water-storage containers, old tires or toilets in the yard, having no TV, having no air conditioning and having travelled at least once outside the city were independently associated with anti-dengue IgG positivity in Douala. Age, having uncovered water containers, having no TV, not being born in Garoua and not breeding pigs were significant risk factors in Garoua. Recent history of malaria, having banana trees and stagnant water in the yard were independent risk factors in Yaounde.Conclusion/SignificanceIn this survey, most identified risk factors of dengue were related to housing conditions. Poverty and underdevelopment are central to the dengue epidemiology in Cameroon.

Seroprevalence of Dengue IgG Antibodies among Healthy Adult Population in Lahore, Pakistan

Background. Dengue is a mosquito-borne flavivirus infection prevalent in tropical and subtropical regions around the world. Aim of this study was to determine seroprevalence of anti-dengue IgG antibodies in healthy adult population of Lahore and also describe risk factors in relation to dengue seropositivity. Methods. In this cross-sectional study, 274 healthy adult individuals aged 15 years and above were randomly selected using multistage sampling technique. These individuals were interviewed between July–September 2012, using a semistructured questionnaire, followed by drawing 3 mL of their venous blood for dengue IgG test. Nova Tech ELISA kit with sensitivity and specificity of 96.5% and 97.5%, respectively, was used for serology. Results. Out of 274 participants, 184 (67.2%) were found to be positive for dengue IgG antibodies. Seroprevalence was higher among individuals with poor awareness about potential breeding sites for dengue mosquito (63.6%), followed by the subjects who had poor knowledge about dengue signs/symptoms and complications (52.2% and 68.5%, resp.). Conclusion. About two-third of healthy population of Lahore was also seropositive for anti-dengue IgG during July–September 2012, indicating a considerable burden of subclinical dengue infection in the city. Males were predominantly affected than the females. We found no statistical association between dengue IgG seropositivity and socioeconomic status, occupation, and knowledge about the disease.

Prevalence of anti‐dengue immunoglobulin G antibodies among American Red Cross blood donors in Puerto Rico, 2006

Dengue is endemic in Puerto Rico and causes periodic outbreaks involving thousands of persons. Seroprevalence studies among blood donors can provide useful data on the immune status of the adult population. The objective of this study was to determine the prevalence of anti-dengue immunoglobulin (Ig)G antibodies in a random sample of blood donors to the American Red Cross (ARC) in Puerto Rico. Three-hundred randomly selected blood donations collected by the ARC from February 1 to March 31, 2006, were tested using an anti-dengue IgG enzyme-linked immunosorbent assay. One-third of the positive specimens were randomly selected and tested by a microneutralization test (MNT) to determine the serotypes of previous dengue infections. Most (84%) blood donors were male, and the mean age was 44.6 years (range, 18-80 years). The prevalence (95% confidence interval) of anti-dengue IgG antibodies was 92% (89%-95%). Of the 92 specimens tested by the MNT, reactivity to all four dengue serotypes was observed and 96% were secondary infections. The predominant serotype with the highest neutralization titers, as identified by at least a fourfold higher titer compared to any other serotype tested, was identified in 32 specimens; the most common predominant serotypes identified by the MNT were DENV-3 and DENV-2 (63%). Recent infection with DENV-1 was detected but, in 2005, routine surveillance did not detect any cases of this serotype. Supplementary serologic testing of donated blood can potentially provide information on the silent circulation or introduction of dengue serotypes.

Kinetics of non-structural protein 1, IgM and IgG antibodies in dengue type 1 primary infection

BackgroundEarly and accurate diagnosis of dengue infection is essential for control of disease outbreaks. Recently, the dengue virus non-structural antigen 1 (NS1), a conserved and secreted glycoprotein, has been used as a marker for early diagnosis of dengue with convenience and cost-effectiveness. Serological tests of dengue IgM and IgG antibodies are still the most widely used for diagnosis of dengue. In order to assess combined diagnostic value of these tests, we study the kinetic profiles of circulating NS1, dengue IgM and IgG antibodies over the course of the disease by using an in-house dengue type 1 (DENV1) specific NS1 capture ELISA and the commercial Panbio Dengue IgM and IgG capture ELISAs.ResultsA panel of 313 acute-and early convalescent-phase serum specimens from 140 DENV1 primary infected patients during an outbreak of dengue in Guangzhou, China, in 2006 were studied. Dengue NS1 presented high levels in acute-phase serum samples. It was detectable as early as day 1 of illness, and up to 14 day after onset. The sensitivity of NS1 detection was ranged from 81.8% to 91.1% with samples taken during the first 7 days. Anti-dengue IgM antibody was detectable on the third day of onset with the positive rate of 42.9%, and rapidly increasing to 100% by day 8 of illness. Anti-dengue IgG antibody was detectable on the fifth day of onset with low level at the first week of onset, and slowly increasing to 100% by day 15 of illness. Combining the results of NS1 and IgM antibody detection allowed positive diagnosis in 96.9% -100% for samples taken after day 3 of onset.ConclusionsDengue NS1 detection might shorten the window period by first few days of illness. A combination of dengue NS1 antigen and IgM antibody testing facilitates enhanced diagnosis rates. The procedures should be suitable for developing countries where dengue is endemic.

Seroprevalence and risk factors for dengue infection in socio-economically distinct areas of Recife, Brazil

Brazil currently accounts for the majority of dengue cases reported in the Americas, with co-circulation of DENV 1-3. Striking variation in the epidemiological pattern of infection within cities has been observed. Therefore, investigation of dengue transmission in small areas is important to formulate control strategies. A population-based household survey was performed in three diverse socio-economic and environmental areas of Recife, a large urban center of Brazil, between 2005 and 2006. Dengue serostatus and individual- and household-level risk factors for infection were collected in residents aged between 5 and 64 years. A total of 2833 individuals were examined, and their residences were geo-referenced. Anti-dengue IgG antibodies were measured using commercial ELISA. The dengue seroprevalence and the force of infection were estimated in each area. Individual and household variables associated with seropositivity were assessed by multilevel models for each area. A spatial analysis was conducted to identify risk gradients of dengue seropositivity using Generalized Additive Models (GAM). The dengue seroprevalence was 91.1%, 87.4% 74.3%, respectively, in the deprived, intermediate and high socio-economic areas, inversely related to their socio-economic status. In the deprived area, 59% of children had already been exposed to dengue virus by the age of 5 years and the estimated force of infection was three times higher than that in the privileged area. The risk of infection increased with age in the three areas. Not commuting away from the area was a risk factor for seropositivity in the deprived area (OR=2.26; 95% CI: 1.18-4.30). Number of persons per room was a risk factor for seropositivity in the intermediate (OR=3.00; 95% CI: 3.21-7.37) and privileged areas (OR=1.81; 95% CI: 1.07-3.04). Living in a house, as opposed to an apartment, was a risk factor for seropositivity in the privileged area (OR=3.62; 95% CI: 2.43-5.41). The main difference between the privileged and other areas could be attributed to the much larger proportion of apartment dwellers. Intensive vector control, surveillance and community education should be considered in deprived urban areas where a high proportion of children are infected by an early age.