Cross reactivity of commercial anti-dengue immunoassays in patients with acute Zika virus infection

Nanobody-Based Lateral Flow Assay for Rapid Zika Virus Detection

Zika virus infections remain severely underdiagnosed due to their initial mild clinical symptoms. However, recent outbreaks have revealed neurological complications in adults and severe deformities in newborns, emphasizing the critical need for accurate diagnosis. Lateral flow assays (LFAs) provide a rapid, cost-effective, and user-friendly method for antigen testing at point-of-care, bedside, or in home settings. LFAs utilizing nanobodies have multiple benefits over traditional antibody-based techniques, as nanobodies are much smaller, more stable, and simpler to manufacture. We introduce a nanobody-based LFA for the rapid identification of Zika virus antigens. Starting from two previously reported nanobodies recognizing the Zika nonstructural protein 1 (NS1), we evaluate periplasmic and cytosolic nanobody expression and test different purification tags and immobilization strategies. We quantify nanobody binding kinetics and validate their mutually noncompetitive binding. Avidity effects boost the capture of the tetrameric target protein by 3 orders of magnitude and point to a general strategy for higher sensitivity LFA sensing. The nanobody LFA detects Zika NS1 with a limit of detection ranging from 25 ng/mL in buffer to 1 ng/mL in urine. This nanobody-LFA has the potential to facilitate on-site and self-diagnosis, improve our understanding of Zika infection prevalence, and support public health initiatives in regions affected by Zika virus outbreaks.

A Scoping Review of Arthropod-Borne Flavivirus Infections in Solid Organ Transplant Recipients

Arthropod-borne flaviviruses (ABFs), transmitted by mosquitoes or ticks, are increasing due to climate change and globalization. This scoping review examines the epidemiology, clinical characteristics, diagnostics, treatment, and outcomes of ABF infection in solid organ transplant recipients (SOTRs). A database search up to January 25, 2024, focused on ABFs such as West Nile virus (WNV), dengue virus (DENV), Japanese encephalitis virus (JEV), Powassan virus (POWV), yellow fever virus (YFV), and Zika virus (ZIKV), limited to SOTRs. We identified 173 WNV cases from 84 studies, with 28 donor-derived infections (DDIs). Common clinical features included fever (78.5%), altered mental status (65.1%), and weakness or paralysis (45.6%). Treatment involved reducing immunosuppression (IS) in 93 cases, with intravenous immunoglobulin (IVIG), interferon alfa-2b, and ribavirin used in 75 cases. Seven cases involved graft loss or rejection post-infection. WNV infection had a 23.7% mortality rate, with severe neurological complications in 43.9% For DENV infection, 386 cases from 47 studies were identified, including 14 DDI cases. Symptoms included fever (85%), myalgias (56.4%), and headache or retro-orbital pain (34.6%). Severe dengue occurred in 50 cases (13.0%). IVIG was administered in six cases. Reduction in IS was reported in 116 patients. DENV mortality rate was 4.9%. Additionally, 26 cases of less common ABFs such as JEV, POWV, YFV, and ZIKV were described. In summary, ABF infections among SOTRs are associated with higher morbidity and mortality compared to the general population, emphasizing the need for improved preventive strategies, timely diagnosis, and optimized management protocols.

Detection of anti-premembrane antibody as a specific marker of four flavivirus serocomplexes and its application to serosurveillance in endemic regions

In the past few decades, several emerging/re-emerging mosquito-borne flaviviruses have resulted in disease outbreaks of public health concern in the tropics and subtropics. Due to cross-reactivities of antibodies recognizing the envelope protein of different flaviviruses, serosurveillance remains a challenge. Previously we reported that anti-premembrane (prM) antibody can discriminate between three flavivirus infections by Western blot analysis. In this study, we aimed to develop a serological assay that can discriminate infection or exposure with flaviviruses from four serocomplexes, including dengue (DENV), Zika (ZIKV), West Nile (WNV) and yellow fever (YFV) viruses, and explore its application for serosurveillance in flavivirus-endemic countries. We employed Western blot analysis including antigens of six flaviviruses (DENV1, 2 and 4, WNV, ZIKV and YFV) from four serocomplexes. We tested serum samples from YF-17D vaccinees, and from DENV, ZIKV and WNV panels that had been confirmed by RT-PCR or by neutralization assays. The overall sensitivity/specificity of anti-prM antibodies for DENV, ZIKV, WNV, and YFV infections/exposure were 91.7%/96.4%, 91.7%/99.2%, 88.9%/98.3%, and 91.3%/92.5%, respectively. When testing 48 samples from Brazil, we identified multiple flavivirus infections/exposure including DENV and ZIKV, DENV and YFV, and DENV, ZIKV and YFV. When testing 50 samples from the Philippines, we detected DENV, ZIKV, and DENV and ZIKV infections with a ZIKV seroprevalence rate of 10%, which was consistent with reports of low-level circulation of ZIKV in Asia. Together, these findings suggest that anti-prM antibody is a flavivirus serocomplex-specific marker and can be employed to delineate four flavivirus infections/exposure in regions where multiple flaviviruses co-circulate.

Aptamer-associated colorimetric reverse transcription loop-mediated isothermal amplification assay for detection of dengue virus

Current diagnostic methods for dengue, such as serological tests, have limitations in terms of cross-reactivity with other viruses. To address this issue, we explored the potential of combining the loop-mediated isothermal amplification (LAMP) technique with the affinity of aptamers to develop point-of-care testing. In this study, we utilized 60 serum samples. An aptamer capable of binding to the dengue virus was employed as a platform for capturing genetic material, and its performance was compared to a commercial kit. Dengue virus was detected through RT-PCR and colorimetric reverse transcription loop-mediated isothermal amplification (RT-LAMP), allowing visual observation of the results without the need for equipment. In the context of the aptamer LAMP assay, our analysis revealed the detection of the dengue virus in 38 out of 60 samples, with 95% sensitivity and 100% specificity compared to RT-PCR and/or APTA-RT-PCR. Importantly, we observed no cross-reaction when assessing samples positive for the zika virus, underscoring the assay's selectivity. This innovative aptameric capture of the viral RNA in combination with the RT-LAMP (APTA-RT-LAMP) method has the potential to offer valuable molecular insights into neglected infectious diseases in a simpler and faster manner.

IMPORTANCE

Dengue is a neglected tropical disease of significant epidemiological importance in tropical and subtropical countries. Current diagnostics for this infection present challenges, such as cross-reactivity in serological tests. Finding ways to enhance the diagnosis of this disease is crucial, given the absence of specific treatments. An accurate, simple, and effective diagnosis contributes to the improved management of infected individuals. In this context, our work combines molecular biology techniques, such as isothermal loop amplification, with aptamers to detect the dengue virus in biological samples. Our method produces colorimetric results based on a color change, with outcomes available in less than 2 hours. Moreover, it requires simpler equipment compared to molecular PCR tests.

Innovations in dengue virus detection: An overview of conventional and electrochemical biosensor approaches

Globally, people are in great threat due to the highly spreading of viral infectious diseases. Every year like 100-300 million cases of infections are found, and among them, above 80% are not recognized and irrelevant. Dengue virus (DENV) is an arbovirus infection that currently infects people most frequently. DENV encompasses four viral serotypes, and they each express comparable sign. From a mild febrile sickness to a potentially fatal dengue hemorrhagic fever, dengue can induce a variety of symptoms. Presently, the globe is being challenged by the untimely identification of dengue infection. Therefore, this review summarizes advances in the detection of dengue from conventional methods (nucleic acid-based, polymerase chain reaction-based, and serological approaches) to novel biosensors. This work illustrates an extensive study of the current designs and fabrication approaches involved in the formation of electrochemical biosensors for untimely identifications of dengue. Additionally, in electrochemical sensing of DENV, we skimmed through significances of biorecognition molecules like lectins, nucleic acid, and antibodies. The introduction of emerging techniques such as the CRISPR/Cas' system and their integration with biosensing platforms has also been summarized. Furthermore, the review revealed the importance of electrochemical approach compared with traditional diagnostic methods.

Influence of previous Zika virus infection on acute dengue episode

BACKGROUND

The co-circulation of flaviviruses in tropical regions has led to the hypothesis that immunity generated by a previous dengue infection could promote severe disease outcomes in subsequent infections by heterologous serotypes. This study investigated the influence of antibodies generated by previous Zika infection on the clinical outcomes of dengue infection.

METHODOLOGY/PRINCIPAL FINDINGS

We enrolled 1,043 laboratory confirmed dengue patients and investigated their prior infection to Zika or dengue. Severe forms of dengue disease were more frequent in patients with previous Zika infection, but not in those previously exposed to dengue.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest that previous Zika infection may represent a risk factor for subsequent severe dengue disease, but we did not find evidence of antibody-dependent enhancement (higher viral titer or pro-inflammatory cytokine overexpression) contributing to exacerbation of the subsequent dengue infection.

Detection of anti-premembrane antibody as a specific marker of four flavivirus serocomplexes and its application to serosurveillance in endemic regions

In the past few decades, several emerging/re-emerging mosquito-borne flaviviruses have resulted in disease outbreaks of public health concern in the tropics and subtropics. Due to cross-reactivities of antibodies recognizing the envelope protein of different flaviviruses, serosurveillance remains a challenge. Previously we reported that anti-premembrane (prM) antibody can discriminate between three flavivirus infections by Western blot analysis. In this study, we aimed to develop a serological assay that can discriminate infection or exposure with flaviviruses from four serocomplexes, including dengue (DENV), Zika (ZIKV), West Nile (WNV) and yellow fever (YFV) viruses, and explore its application for serosurveillance in flavivirus-endemic countries. We employed Western blot analysis including antigens of six flaviviruses (DENV1, 2 and 4, WNV, ZIKV and YFV) from four serocomplexes. We tested serum samples from YF-17D vaccinees, and from DENV, ZIKV and WNV panels that had been confirmed by RT-PCR or by neutralization assays. The overall sensitivity/specificity of anti-prM antibodies for DENV, ZIKV, WNV, and YFV infections/exposure were 91.7%/96.4%, 91.7%/99.2%, 88.9%/98.3%, and 91.3%/92.5%, respectively. When testing 48 samples from Brazil, we identified multiple flavivirus infections/exposure including DENV and ZIKV, DENV and YFV, and DENV, ZIKV and YFV. When testing 50 samples from the Philippines, we detected DENV, ZIKV, and DENV and ZIKV infections with a ZIKV seroprevalence rate of 10%, which was consistent with reports of low-level circulation of ZIKV in Asia. Together, these findings suggest that anti-prM antibody is a flavivirus serocomplex-specific marker and can be employed to delineate four flavivirus infections/exposure in regions where multiple flaviviruses co-circulate.

Multi-epitope Antigen for Specific Serological Detection of Dengue Viruses

Dengue is an infectious disease of global health concern that continues to require surveillance. Serological testing has been used to investigate dengue-infected patients, but specificity is affected by the co-circulation of ZIKA virus (ZIKV), which shares extensive antigen similarities. The goal of this study was the development of a specific dengue virus (DENV) IgG ELISA based on a multi-epitope NS1-based antigen for antibody detection. The multi-epitope protein (T-ΔNS1), derived from a fragment of the NS1-protein of the four DENV serotypes, was expressed in Escherichia coli and purified via affinity chromatography. The antigenicity and specificity were evaluated with sera of mice infected with DENV-1-4 or ZIKV or after immunization with the recombinant ΔNS1 proteins. The performance of the T-ΔNS1-based IgG ELISA was also determined with human serum samples. The results demonstrate that the DENV T-ΔNS1 was specifically recognized by the serum IgG of dengue-infected mice or humans but showed no or reduced reactivity with ZIKV-infected subjects. Based on the available set of clinical samples, the ELISA based on the DENV T-ΔNS1 achieved 77.42% sensitivity and 88.57% specificity. The results indicate that the T-ΔNS1 antigen is a promising candidate for the development of specific serological analysis.

The increasing complexity of arbovirus serology: An in-depth systematic review on cross-reactivity

Diagnosis of arbovirus infection or exposure by antibody testing is becoming increasingly difficult due to global expansion of arboviruses, which induce antibodies that may (cross-)react in serological assays. We provide a systematic review of the current knowledge and knowledge gaps in differential arbovirus serology. The search included Medline, Embase and Web of Science databases and identified 911 publications which were reduced to 102 after exclusion of studies not providing data on possible cross-reactivity or studies that did not meet the inclusion criteria regarding confirmation of virus exposure of reference population sets. Using a scoring system to further assess quality of studies, we show that the majority of the selected papers (N = 102) provides insufficient detail to support conclusions on specificity of serological outcomes with regards to elucidating antibody cross-reactivity. Along with the lack of standardization of assays, metadata such as time of illness onset, vaccination, infection and travel history, age and specificity of serological methods were most frequently missing. Given the critical role of serology for diagnosis and surveillance of arbovirus infections, better standards for reporting, as well as the development of more (standardized) specific serological assays that allow discrimination between exposures to multiple different arboviruses, are a large global unmet need.

Comparing the performance of dengue virus IgG and IgG-capture enzyme-linked immunosorbent assays in seroprevalence study

BACKGROUND

Dengue virus (DENV) is the leading cause of arboviral diseases in humans worldwide. Currently Dengvaxia, the first dengue vaccine licensed in 20 countries, was recommended for DENV seropositive individuals aged 9-45 years. Studying dengue seroprevalence can improve our understanding of the epidemiology and transmission dynamics of DENV, and facilitate future intervention strategies and assessment of vaccine efficacy. Several DENV envelope protein-based serological tests including IgG and IgG-capture enzyme-linked immunosorbent assays (ELISAs) have been employed in seroprevalence studies. Previously DENV IgG-capture ELISA was reported to distinguish primary and secondary DENV infections during early convalescence, however, its performance over time and in seroprevalence study remains understudied.

METHODS

In this study, we used well-documented neutralization test- or reverse-transcription-polymerase-chain reaction-confirmed serum/plasma samples including DENV-naïve, primary and secondary DENV, primary West Nile virus, primary Zika virus, and Zika with previous DENV infection panels to compare the performance of three ELISAs.

RESULTS

The sensitivity of the InBios IgG ELISA was higher than that of InBios IgG-capture and SD IgG-capture ELISAs. The sensitivity of IgG-capture ELISAs was higher for secondary than primary DENV infection panel. Within the secondary DENV infection panel, the sensitivity of InBios IgG-capture ELISA decreased from 77.8% at < 6 months to 41.7% at 1-1.5 years, 28.6% at 2-15 years and 0% at > 20 years (p < 0.001, Cochran-Armitage test for trend), whereas that of IgG ELISA remains 100%. A similar trend was observed for SD IgG-capture ELISA.

CONCLUSIONS

Our findings demonstrate higher sensitivity of DENV IgG ELISA than IgG-capture ELISA in seroprevalence study and interpretation of DENV IgG-capture ELISA should take sampling time and primary or secondary DENV infection into consideration.

Electrochemical magneto-immunoassay for detection of zika virus antibody in human serum

Zika virus (ZIKV) is a flavivirus transmitted by infected Aedes genus mosquitoes. An infected person may be asymptomatic or present symptoms such as fever, arthralgia, and in pregnancy it may lead to neurological disorders in the fetus, such as microcephaly. Based on the high dissemination potential of ZIVK and its similar antigen composition to other arboviruses, new approaches for selective virus detection are urgently needed. This work reports the development of an electrochemical immunoassay for detection of anti-ZIKV antibodies, using magnetic beads functionalized with recombinant protein derived from the non-structural protein 1 (ΔNS1-ZIKV) and anti-IgG antibodies labeled with horseradish peroxidase (HRP) enzyme. The magneto-immunoassay uses disposable microfluidic devices for detection of anti-ZIKV in serum samples. A linear response was obtained for a wide concentration range from 0.01 to 9.80 × 10⁵ pg mL^-1 (r² = 0.982), with a limit of detection of 0.48 pg mL^-1. The proposed immunoassay proved to be highly efficient for the detection of anti-ZIKV antibodies in serum, offering promising perspectives for the development of fast, simple, and affordable point-of-care diagnosis devices for ZIKV.

Detection of DENV-2 and ZIKV coinfection in southeastern Brazil by serum and urine testing

PURPOSE

Aedes aegypti mosquito-borne diseases have a significant impact on public health in Brazil. In this study, we investigated the presence of the Zika virus (ZIKV) and dengue virus (DENV) in serum and urine samples from symptomatic participants who attended an Emergency Care Unit located in a city in the northwestern region of São Paulo between February 2018 and April 2019.

METHODS

Serum and urine samples were collected from participants suspected of having arbovirus infection. After the extraction of viral RNA, viral detection was performed by real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) (One-Step RT-qPCR).

RESULTS

A total of 305 participants participated in this study. A total of 283 blood and 270 urine samples were collected. Of 305 patients, 36.4% (111/305) were positive for ZIKV, 43.3% (132/305) for DENV2, and 0.3% (1/305) for DENV1. Coinfection with ZIKV/DENV2 was observed in 13.1% of participants. If only serum samples were used, ZIKV detection would have decreased to 23.3% (71/305). Of all the participants included in the study, only one was suspected of having ZIKV infection based on clinical diagnosis, and the remaining participants were suspected of having DENV.

CONCLUSION

By testing serum and urine samples, we increased the detection of both viruses and detected considerable levels of ZIKV and DENV-2 coinfection when compared to other studies. Additionally, we detected an unnoticed ZIKV outbreak in the city. These findings highlight the importance of the molecular diagnosis of arboviruses to aid public health surveillance and management strategies.

Diagnostic and vaccine potential of Zika virus envelope protein (E) derivates produced in bacterial and insect cells

Introduction

In the present study we evaluated the features of different recombinant forms of Zika virus (ZIKV) proteins produced in either bacterial (Eschericha coli) or insect cells (Drosophila melanogaster). The ZIKV-envelope glycoprotein (EZIKV) is responsible for virus entry into host cells, is the main target of neutralizing antibodies and has been used as a target antigen either for serological tests or for the development of subunit vaccines. The EZIKV is composed of three structural and functional domains (EDI, EDII, and EDIII), which share extensive sequence conservation with the corresponding counterparts expressed by other flaviviruses, particularly the different dengue virus (DENV) subtypes.

Methods

In this study, we carried out a systematic comparison of the antigenicity and immunogenicity of recombinant EZIKV, EDI/IIZIKV and EDIIIZIKV produced in E. coli BL21 and Drosophila S2 cells. For the antigenicity analysis we collected 88 serum samples from ZIKV-infected participants and 57 serum samples from DENV-infected. For immunogenicity, C57BL/6 mice were immunized with two doses of EZIKV, EDI/IIZIKV and EDIIIZIKV produced in E. coli BL21 and Drosophila S2 cells to evaluate humoral and cellular immune response. In addition, AG129 mice were immunized with EZIKV and then challenge with ZIKV.

Results

Testing of samples collected from ZIKV-infected and DENV-infected participants demonstrated that the EZIKV and EDIIIZIKV produced in BL21 cells presented better sensitivity and specificity compared to proteins produced in S2 cells. In vivo analyses were carried out with C57BL/6 mice and the results indicated that, despite similar immunogenicity, antigens produced in S2 cells, particularly EZIKV and EDIIIZIKV, induced higher ZIKV-neutralizing antibody levels in vaccinated mice. In addition, immunization with EZIKV expressed in S2 cells delayed the onset of symptoms and increased survival rates in immunocompromised mice. All recombinant antigens, either produced in bacteria or insect cells, induced antigen-specific CD4+ and CD8+ T cell responses.

Conclusion

In conclusion, the present study highlights the differences in antigenicity and immunogenicity of recombinant ZIKV antigens produced in two heterologous protein expression systems.

Nanobody-Based Blocking of Binding ELISA for the Detection of Anti-NS1 Zika-Virus-Specific Antibodies in Convalescent Patients

Zika virus has spread around the world with rapid pace in the last five years. Although symptoms are typically mild and unspecific, Zika's major impact occurs during pregnancy, generating a congenital syndrome. Serology plays a key role in its diagnosis. However, its use is limited due to the uncertainty caused by the cross-reaction of antibodies elicited in response to other flavivirus infections when tested in direct immunoassays. Using a panel of previously generated anti-Zika non-structural protein 1 (NS1) nanobodies, a set was selected that only recognizes epitopes present in Zika and is immunogenic to humans. A proper arrangement of these nanobodies was made and conditions were optimized in order to develop a novel serology assay. This new ELISA relies on the inhibition of the binding of a set of selected nanobodies to Zika-immobilized NS1 when previously incubated with Zika convalescent sera. Using the developed blocking of binding assay, it was possible to discriminate between Zika-specific and cross-reactive antibodies in serum samples from infections with Zika and other flaviviruses.

In silico and in vitro arboviral MHC class I-restricted-epitope signatures reveal immunodominance and poor overlapping patterns

INTRODUCTION

The present work sought to identify MHC-I-restricted peptide signatures for arbovirus using in silico and in vitro peptide microarray tools.

METHODS

First, an in-silico analysis of immunogenic epitopes restricted to four of the most prevalent human MHC class-I was performed by identification of MHC affinity score. For that, more than 10,000 peptide sequences from 5 Arbovirus and 8 different viral serotypes, namely Zika (ZIKV), Dengue (DENV serotypes 1-4), Chikungunya (CHIKV), Mayaro (MAYV) and Oropouche (OROV) viruses, in addition to YFV were analyzed. Haplotype HLA-A*02.01 was the dominant human MHC for all arboviruses. Over one thousand HLA-A2 immunogenic peptides were employed to build a comprehensive identity matrix. Intending to assess HLAA*02:01 reactivity of peptides in vitro, a peptide microarray was designed and generated using a dimeric protein containing HLA-A*02:01.

RESULTS

The comprehensive identity matrix allowed the identification of only three overlapping peptides between two or more flavivirus sequences, suggesting poor overlapping of virus-specific immunogenic peptides amongst arborviruses. Global analysis of the fluorescence intensity for peptide-HLA-A*02:01 binding indicated a dose-dependent effect in the array. Considering all assessed arboviruses, the number of DENV-derived peptides with HLA-A*02:01 reactivity was the highest. Furthermore, a lower number of YFV-17DD overlapping peptides presented reactivity when compared to non-overlapping peptides. In addition, the assessment of HLA-A*02:01-reactive peptides across virus polyproteins highlighted non-structural proteins as "hot-spots". Data analysis supported these findings showing the presence of major hydrophobic sites in the final segment of non-structural protein 1 throughout 2a (Ns2a) and in nonstructural proteins 2b (Ns2b), 4a (Ns4a) and 4b (Ns4b).

DISCUSSION

To our knowledge, these results provide the most comprehensive and detailed snapshot of the immunodominant peptide signature for arbovirus with MHC-class I restriction, which may bring insight into the design of future virus-specific vaccines to arboviruses and for vaccination protocols in highly endemic areas.

Effect of prior Zika and dengue virus exposure on the severity of a subsequent dengue infection in adults

Given the structural similarity between Zika and dengue viruses, prior infection from one virus is hypothesized to modulate the severity of a subsequent infection from the other virus. A previous paediatric cohort study observed that a prior Zika infection may increase the risk of a subsequent symptomatic or severe dengue infection. The Colombo Dengue study is a prospective hospital-based cohort study in Sri Lanka that recruits symptomatic adult dengue patients within the first three days of fever. Anti-Dengue Envelope and anti-Zika NS1 IgG antibodies were tested by ELISA (Euroimmun, Lubeck, Germany) in all recruited patients. Associations between pre-morbid seroprevalence for either or both infections and adverse clinical outcomes of the current dengue infection were explored. A total of 507 dengue infected patients were assessed of whom 342 (68%) and 132 (26%) patients had anti-dengue IgG and anti-Zika IgG respectively. People with combined prior dengue and zika exposure as well as prior dengue exposure alone, were at increased risk of plasma leakage, compensated and uncompensated shock, and severe dengue (p < 0·05), compared to people without prior exposure to either infection. The effect of prior Zika exposure alone could not be established due to the small the number of primary dengue infections with prior Zika exposure.

Development and evaluation of a visible reverse transcription-loop-mediated isothermal amplification (RT-LAMP) for the detection of Asian lineage ZIKV in field-caught mosquitoes

The Zika virus (ZIKV) infection is an emerging and re-emerging arbovirus infection that is transmitted to humans through the bite of infected mosquitoes. Early detection of ZIKV in mosquitoes is one of the prerequisite approaches for tracking the spread of the virus. Therefore, this study aims to develop and validate a visual reverse transcription-loop-mediated isothermal amplification (RT-LAMP) method called ZIKV-RT-LAMP, for detecting ZIKV in field collected mosquito samples from Thailand. A single-tube ZIKV-RT-LAMP assay was developed to detect Asian lineage ZIKV RNA. The detection limit and cross-reactivity of ZIKV were investigated. The hemi-nested RT-PCR (hn-RT-PCR) and the colorimetric LAMP kit (cLAMP kit) were performed as reference assays. The detection limit of the ZIKV-RT-LAMP assay was 10^-6 ffu/ml or pfu/ml, making it highly specific and 100 times more sensitive than the hn-RT-PCR and cLAMP kits. The ZIKV-RT-LAMP assay detected the Asian lineage of ZIKV RNA without cross-reactivity with other arthropod-borne viruses. The sensitivity and specificity of the ZIKV-RT-LAMP assay were 92.31% and 100%, respectively. The ZIKV-RT-LAMP is a simple, rapid, and inexpensive method for detecting ZIKV in field-caught mosquitos. In the future, extensive surveys of field-caught mosquito populations should be conducted. Early detection of ZIKV in field-caught mosquitoes provides for prompt and effective implementation of mosquito control strategies in endemic areas.

Complexity of Viral Epitope Surfaces as Evasive Targets for Vaccines and Therapeutic Antibodies

The dynamic interplay between virus and host plays out across many interacting surfaces as virus and host evolve continually in response to one another. In particular, epitope-paratope interactions (EPIs) between viral antigen and host antibodies drive much of this evolutionary race. In this review, we describe a series of recent studies examining aspects of epitope complexity that go beyond two interacting protein surfaces as EPIs are typically understood. To structure our discussion, we present a framework for understanding epitope complexity as a spectrum along a series of axes, focusing primarily on 1) epitope biochemical complexity (e.g., epitopes involving N-glycans) and 2) antigen conformational/dynamic complexity (e.g., epitopes with differential properties depending on antigen state or fold-axis). We highlight additional epitope complexity factors including epitope tertiary/quaternary structure, which contribute to epistatic relationships between epitope residues within- or adjacent-to a given epitope, as well as epitope overlap resulting from polyclonal antibody responses, which is relevant when assessing antigenic pressure against a given epitope. Finally, we discuss how these different forms of epitope complexity can limit EPI analyses and therapeutic antibody development, as well as recent efforts to overcome these limitations.

Capeding M, Padilla CD, Sasmono RT, Hafalla JCR, Hibberd ML. Combining rapid diagnostic tests to estimate primary and post-primary dengue immune status at the point of care

BACKGROUND

Characterising dengue virus (DENV) infection history at the point of care is challenging as it relies on intensive laboratory techniques. We investigated how combining different rapid diagnostic tests (RDTs) can be used to accurately determine the primary and post-primary DENV immune status of reporting patients during diagnosis.

METHODS AND FINDINGS

Serum from cross-sectional surveys of acute suspected dengue patients in Indonesia (N:200) and Vietnam (N: 1,217) were assayed using dengue laboratory assays and RDTs. Using logistic regression modelling, we determined the probability of being DENV NS1, IgM and IgG RDT positive according to corresponding laboratory viremia, IgM and IgG ELISA metrics. Laboratory test thresholds for RDT positivity/negativity were calculated using Youden's J index and were utilized to estimate the RDT outcomes in patients from the Philippines, where only data for viremia, IgM and IgG were available (N:28,326). Lastly, the probabilities of being primary or post-primary according to every outcome using all RDTs, by day of fever, were calculated. Combining NS1, IgM and IgG RDTs captured 94.6% (52/55) and 95.4% (104/109) of laboratory-confirmed primary and post-primary DENV cases, respectively, during the first 5 days of fever. Laboratory test predicted, and actual, RDT outcomes had high agreement (79.5% (159/200)). Among patients from the Philippines, different combinations of estimated RDT outcomes were indicative of post-primary and primary immune status. Overall, IgG RDT positive results were confirmatory of post-primary infections. In contrast, IgG RDT negative results were suggestive of both primary and post-primary infections on days 1-2 of fever, yet were confirmatory of primary infections on days 3-5 of fever.

CONCLUSION

We demonstrate how the primary and post-primary DENV immune status of reporting patients can be estimated at the point of care by combining NS1, IgM and IgG RDTs and considering the days since symptoms onset. This framework has the potential to strengthen surveillance operations and dengue prognosis, particularly in low resource settings.

Arbovirus Surveillance in Field-Collected Mosquitoes From Pernambuco-Brazil, During the Triple Dengue, Zika and Chikungunya Outbreak of 2015-2017

The (re) emergence of arboviruses around the world is a public health concern once severe outbreaks are usually associated with these infections. The co-circulation of Dengue (DENV), Zika (ZIKV) and Chikungunya (CHIKV) viruses in the past few years has caused a unique epidemic situation in Brazil. The northeast region of the country was the most affected by clinical complications from such arboviruses’ infections, including neurological disorders caused by ZIKV. In this particular region, Aedes mosquitoes are the main vectors of DENV, ZIKV and CHIKV, with Culex quinquefasciatus also considered as a potential vector of ZIKV. Therefore, virological surveillance in mosquitoes contributes to understanding the epidemiological profile of these diseases. Here, we report the circulation of DENV, ZIKV and CHIKV in Aedes spp. and Cx. quinquefasciatus female mosquitoes collected in areas with a high arbovirus circulation in humans in the Metropolitan Region of Recife, Pernambuco, Brazil, during the triple-epidemics of 2015-17. All the field-caught mosquitoes were sent to the laboratory for arbovirus screening after RNA extraction and RT-PCR/RT-qPCR. A total of 6,227 females were evaluated and, as a result, DENV, ZIKV and CHIKV were identified in Ae. aegypti, Ae. taeniorhynchus and Cx. quinquefasciatus mosquito pools. In addition, DENV and ZIKV were isolated in C6/36 cells. In conclusion, it is important to highlight that arbovirus surveillance performed in mosquitoes from DENV-ZIKV-CHIKV hotspots areas can serve as an early-warning system to target vector control actions more efficiently in each studied area.

REASSURED Multiplex Diagnostics: A Critical Review and Forecast

The diagnosis of infectious diseases is ineffective when the diagnostic test does not meet one or more of the necessary standards of affordability, accessibility, and accuracy. The World Health Organization further clarifies these standards with a set of criteria that has the acronym ASSURED (Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free and Deliverable to end-users). The advancement of the digital age has led to a revision of the ASSURED criteria to REASSURED: Real-time connectivity, Ease of specimen collection, Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free or simple, and Deliverable to end-users. Many diagnostic tests have been developed that aim to satisfy the REASSURED criteria; however, most of them only detect a single target. With the progression of syndromic infections, coinfections and the current antimicrobial resistance challenges, the need for multiplexed diagnostics is now more important than ever. This review summarizes current diagnostic technologies for multiplexed detection and forecasts which methods have promise for detecting multiple targets and meeting all REASSURED criteria.

OUP accepted manuscript

The Zika virus (ZIKV) disease caused a public health emergency of international concern that started in February 2016. The overall number of ZIKV-related cases increased until November 2016, after which it declined sharply. While the evaluation of the potential risk and impact of future arbovirus epidemics remains challenging, intensified surveillance efforts along with a scale-up of ZIKV whole-genome sequencing provide an opportunity to understand the patterns of genetic diversity, evolution, and spread of ZIKV. However, a classification system that reflects the true extent of ZIKV genetic variation is lacking. Our objective was to characterize ZIKV genetic diversity and phylodynamics, identify genomic footprints of differentiation patterns, and propose a dynamic classification system that reflects its divergence levels. We analysed a curated dataset of 762 publicly available sequences spanning the full-length coding region of ZIKV from across its geographical span and collected between 1947 and 2021. The definition of genetic groups was based on comprehensive evolutionary dynamics analyses, which included recombination and phylogenetic analyses, within- and between-group pairwise genetic distances comparison, detection of selective pressure, and clustering analyses. Evidence for potential recombination events was detected in a few sequences. However, we argue that these events are likely due to sequencing errors as proposed in previous studies. There was evidence of strong purifying selection, widespread across the genome, as also detected for other arboviruses. A total of 50 sites showed evidence of positive selection, and for a few of these sites, there was amino acid (AA) differentiation between genetic clusters. Two main genetic clusters were defined, ZA and ZB, which correspond to the already characterized ‘African’ and ‘Asian’ genotypes, respectively. Within ZB, two subgroups, ZB.1 and ZB.2, represent the Asiatic and the American (and Oceania) lineages, respectively. ZB.1 is further subdivided into ZB.1.0 (a basal Malaysia sequence sampled in the 1960s and a recent Indian sequence), ZB.1.1 (South-Eastern Asia, Southern Asia, and Micronesia sequences), and ZB.1.2 (very similar sequences from the outbreak in Singapore). ZB.2 is subdivided into ZB.2.0 (basal American sequences and the sequences from French Polynesia, the putative origin of South America introduction), ZB.2.1 (Central America), and ZB.2.2 (Caribbean and North America). This classification system does not use geographical references and is flexible to accommodate potential future lineages. It will be a helpful tool for studies that involve analyses of ZIKV genomic variation and its association with pathogenicity and serve as a starting point for the public health surveillance and response to on-going and future epidemics and to outbreaks that lead to the emergence of new variants.

Towards Integrated Management of Dengue in Mumbai

With increasing urbanisation, the dengue disease burden is on the rise in India, especially in large cities such as Mumbai. Current dengue surveillance in Mumbai includes municipal corporation carrying out specific activities to reduce mosquito breeding sites and the use of insecticides to suppress the adult mosquito populations. Clinical cases remain either underreported or misreported due to the restriction to government clinics, missing the large private health care sector. There is a need for an integrated approach to manage dengue outbreaks in Mumbai. There are various novel strategies available for use that can be utilised to improve disease detection, mosquito surveillance, and control of mosquito-borne diseases. These novel technologies are discussed in this manuscript. Given the complex ecosystem of mosquito-borne diseases in Mumbai, integrating data obtained from these technologies would support the ongoing mosquito control measures in Mumbai.

Imperfect diagnosis: The truncated legacies of Zika testing

When the Zika virus burst onto the international scene in the second half of 2015, the development of diagnostic tools was seen as an urgent global health priority. Diagnostic capacity was restricted to a small number of reference laboratories, and none of the few available molecular or serological tests had been validated for extensive use in an outbreak setting. In the early weeks of the crisis, key funders stepped in to accelerate research and development efforts, and the WHO took responsibility for steering diagnostic standardization, a role it had successfully played during the West Africa Ebola virus outbreak. Yet when the WHO declared the end of the Zika Public Health Emergency of International Concern in November 2016, diagnostic capacity remained patchy, and few tools were available at the scale required in the countries that bore the brunt of the epidemic, particularly Brazil. This article analyses the limited impact of global R&D efforts on the availability of Zika diagnostic options where they were most needed and for those most vulnerable: women who might have been exposed to the virus during their pregnancy and children born with suspected congenital Zika syndrome. The truncated legacies of testing during the Zika crisis reveal some of the fault lines in the global health enterprise, particularly the limits of 'emergency R&D' to operate in geopolitical contexts that do not conform to the ideal type of a humanitarian crisis, or to tackle technical issues that are inextricably linked to domestic struggles over the scope and distribution of biological citizenship. Diagnostic shortcomings, we argue, lie at the heart of the stunning transformation, in less than two years, in the status of Zika: from international public health emergency to neglected disease.

NS1-based ELISA test efficiently detects dengue infections without cross-reactivity with Zika virus

OBJECTIVES

The aim of this study was to achieve greater specificity of dengue virus (DENV) serological tests based on a recombinant antigen derived from non-structural protein 1 (ΔNS1) with regard to cross-reactive Zika virus (ZIKV) anti-NS1 antibody responses. This is of relevance in endemic regions for the serological discrimination of both DENV and ZIKV, such as Brazil and other tropical countries.

METHODS

The ΔNS1 proteins were obtained as recombinant antigens and were evaluated as solid-phase-bound antigens in the ELISA test to detect anti-NS1 IgG antibodies. The performance of the ∆NS1-based DENV IgG ELISA was assessed with both mouse and human serum samples previously exposed to DENV or ZIKV.

RESULTS

The ∆NS1-based DENV IgG ELISA detected anti-DENV NS1 IgG without cross-reactivity with ZIKV-positive serum samples. The sensitivity and specificity of the assay determined using samples previously characterized by real-time PCR (qRT-PCR) or plaque reduction neutralization assay (PRNT) were 82% and 93%, respectively.

CONCLUSION

The ∆NS1-based DENV IgG ELISA conferred enhanced diagnostic specificity for anti-DENV serological tests and may be particularly useful for serological analyses in endemic regions for both DENV and ZIKV transmission.

Evaluation of Two Serological Assays for Diagnosing Zika Virus Infection

Zika virus (ZIKV) emerged and spread rapidly in South American countries during 2015. Efforts to diagnose ZIKV infection using serological tools were challenging in dengue-endemic areas because of antigenic similarities between both viruses. Here, we assessed the performance of an in-house developed IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA) and the plaque reduction neutralization test (PRNT) to diagnose ZIKV infection. Acute and convalescent paired serum samples from 51 patients who presented with clinical symptoms suggestive of an arbovirus illness in dengue-endemic areas of Honduras, Venezuela, Colombia and Peru were used in the assessment. Samples were tested for ZIKV, dengue and chikungunya virus using a variety of laboratory techniques. The results for the ZIKV-RNA screening and seroconversion detected by the microneutralization test were used to construct a composite reference standard. The overall sensitivity and specificity for the MAC-ELISA were 93.5% and 100.0%, respectively. Contrastingly, the overall sensitivity and specificity for the PRNT were 96.8% and 95.0%, respectively. Restricting the analysis according to IgM or neutralizing antibodies against dengue, the performances of both serological assays were adequate. The findings of this study reveal that the MAC-ELISA and PRNT would provide initial reliable laboratory diagnostic assays for ZIKV infection in dengue-endemic areas.

Competitive ELISA for a serologic test to detect dengue serotype-specific anti-NS1 IgGs using high-affinity UB-DNA aptamers

Serologic tests to detect specific IgGs to antigens related to viral infections are urgently needed for diagnostics and therapeutics. We present a diagnostic method for serotype-specific IgG identification of dengue infection by a competitive enzyme-linked immunosorbent assay (ELISA), using high-affinity unnatural-base-containing DNA (UB-DNA) aptamers that recognize the four categorized serotypes. Using UB-DNA aptamers specific to each serotype of dengue NS1 proteins (DEN-NS1), we developed our aptamer-antibody sandwich ELISA for dengue diagnostics. Furthermore, IgGs highly specific to DEN-NS1 inhibited the serotype-specific NS1 detection, inspiring us to develop the competitive ELISA format for dengue serotype-specific IgG detection. Blood samples from Singaporean patients with primary or secondary dengue infections confirmed the highly specific IgG detection of this format, and the IgG production initially reflected the serotype of the past infection, rather than the recent infection. Using this dengue competitive ELISA format, cross-reactivity tests of 21 plasma samples from Singaporean Zika virus-infected patients revealed two distinct patterns: 8 lacked cross-reactivity, and 13 were positive with unique dengue serotype specificities, indicating previous dengue infection. This antigen-detection ELISA and antibody-detection competitive ELISA combination using the UB-DNA aptamers identifies both past and current viral infections and will facilitate specific medical care and vaccine development for infectious diseases.

Seropositivity for dengue and Leptospira IgM among patients with acute febrile illness: an indicator of co-infection?

Introduction

Presentation of febrile illness with nonspecific features, overlapping manifestations of dengue and leptospirosis, limited laboratory diagnostic tests, make the clinical diagnosis of pyrexia a challenge. The present study aimed to determine the prevalence of Leptospira and dengue IgM co-infection among acute febrile illness patients.

Methods

This is a retrospective hospital-based study which included patient data collected from June 2016 to May 2017. Inpatients' samples (n=2139) were tested for dengue and/or Leptospira IgM at the Microbiology Laboratory. Data like duration of fever, platelet count, hemoglobin, white blood cell count, erythrocyte sedimentation rate, results of liver and renal function tests, mode of treatment, were collected from medical records of laboratory-confirmed co-infection cases.

Results

Among 1612 serum samples tested for dengue IgM by ELISA, 382 (23.7%) were positive, 17 equivocal and 1213 were negative. Of the 811 Leptospira IgM ELISA done, 119 (14.7%) were positive, 17 equivocal and 675 negative. Two hundred eighty-four samples were tested for both infections and nine (3.2%) were positive for both and 275 were negative. These nine patients positive for dual infections showed elevated transaminases, alkaline phosphatase, serum bilirubin, creatinine, and blood urea, thrombocytopenia and leukocytosis. They received effective antibiotics along with supportive treatment and were cured of the infection.

Conclusions

The study emphasizes the possibility of leptospirosis and dengue co-infection (3.2%) and need for confirmation by a highly specific test like PCR. If co-infection is suspected, treatment with specific antibiotics for leptospirosis and supportive treatment for dengue is mandatory, with due attention to complexity of organ involvement.

Temperature-dependent secretion of Zika virus envelope and non-structural protein 1 in mammalian cells for clinical applications

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus associated with congenital Zika syndrome and Guillain-Barré syndrome in adults. The recombinant ZIKV envelope (E) antigen can be useful for serodiagnosis of ZIKV infection and for monitoring immune responses during preclinical and clinical ZIKV vaccine development. In this study, we describe production of ZIKV E using the modified polyethyleneimine (PEI) transfection in HEK293 cells to improve cost-effective large-scale production. We show that the secretion of ZIKV E in HEK293 cells is dependent on cell culture incubation temperatures where incubation at a low temperature of 28 °C improved protein secretion of both, E-CD4 and E, whereas a substantial decrease in secretion was observed at 37 °C. The resulting E-CD4 produced at low temperature yielded similar binding profiles in ELISAs in comparison with a commercially available E protein using human seropositive sera to ZIKV. We also show that ZIKV NS1 and NS1 β-ladder antigens produced in HEK293 cells, have similar binding profiles in ELISA which suggests that both NS1 or NS1 β-ladder can be used for serodiagnosis of ZIKV. In conclusion, we propose a cost-effective production of the ZIKV E and NS1, suitable for both, clinical and research applications in endemic countries.

Dengue and hantavirus coinfection with good outcomes: a clinical case from Panama

Dengue and hantavirus are endemic in central Panama. We present a case report of a patient coinfected with dengue and hantavirus who presented overlapping clinical manifestations of both infections. The patient did not require intensive care-as it is commonplace during hantavirus pulmonary syndrome-and he had a good outcome. Patient's care was positively impacted due to correct diagnosis of coinfection. This case highlights that in endemic areas, coinfection with dengue virus and hantavirus should be suspected. To the best of our knowledge, this case is the first documented case of coinfection with dengue virus and hantavirus in Central America.

A Label and Probe-Free Zika Virus Immunosensor Prussian Blue@carbon Nanotube-Based for Amperometric Detection of the NS2B Protein

Zika virus (ZIKV) is a mosquito-borne infection, predominant in tropical and subtropical regions causing international concern due to the ZIKV disease having been associated with congenital disabilities, especially microcephaly and other congenital abnormalities in the fetus and newborns. Development of strategies that minimize the devastating impact by monitoring and preventing ZIKV transmission through sexual intercourse, especially in pregnant women, since no vaccine is yet available for the prevention or treatment, is critically important. ZIKV infection is generally asymptomatic and cross-reactivity with dengue virus (DENV) is a global concern. An innovative screen-printed electrode (SPE) was developed for amperometric detection of the non-structural protein (NS2B) of ZIKV by exploring the intrinsic redox catalytic activity of Prussian blue (PB), incorporated into a carbon nanotube–polypyrrole composite. Thus, this immunosensor has the advantage of electrochemical detection without adding any redox-probe solution (probe-less detection), allowing a point-of-care diagnosis. It was responsive to serum samples of only ZIKV positive patients and non-responsive to negative ZIKV patients, even if the sample was DENV positive, indicating a possible differential diagnosis between them by NS2B. All samples used here were confirmed by CDC protocols, and immunosensor responses were also checked in the supernatant of C6/36 and in Vero cell cultures infected with ZIKV.

Analysis of a Routinely Used Commercial Anti-Chikungunya IgM ELISA Reveals Cross-Reactivities with Dengue in Brazil: A New Challenge for Differential Diagnosis?

In Brazil, chikungunya emerged in 2014, and by 2016, co-circulated with other arbovirosis, such as dengue and zika. ELISAs (Enzyme-Linked Immunosorbent Assays) are the most widely used approach for arboviruses diagnosis. However, some limitations include antibody cross reactivities when viruses belong to the same genus, and sensitivity variations in distinct epidemiological scenarios. As chikungunya virus (CHIKV) is an alphavirus, no serological cross reactivity with dengue virus (DENV) should be observed. Here, we evaluated a routinely used chikungunya commercial IgM (Immunoglobulin M) ELISA test (Anti-Chikungunya IgM ELISA, Euroimmun) to assess its performance in confirming chikungunya in a dengue endemic area. Samples (n = 340) representative of all four DENV serotypes, healthy individuals and controls were tested. The Anti-CHIKV IgM ELISA test had a sensitivity of 100% and a specificity of 25.3% due to the cross reactivities observed with dengue. In dengue acute cases, the chikungunya test showed an overall cross-reactivity of 31.6%, with a higher cross-reactivity with DENV-4. In dengue IgM positive cases, the assay showed a cross-reactivity of 46.7%. Serological diagnosis may be challenging and, despite the results observed here, more evaluations shall be performed. Because distinct arboviruses co-circulate in Brazil, reliable diagnostic tools are essential for disease surveillance and patient management.

Enzyme-linked immunosorbent assays using virus-like particles containing mutations of conserved residues on envelope protein can distinguish three flavivirus infections

The recent outbreaks of Zika virus (ZIKV) in flavivirus-endemic regions highlight the need for sensitive and specific serological tests. Previously we and others reported key fusion loop (FL) residues and/or BC loop (BCL) residues on dengue virus (DENV) envelope protein recognized by flavivirus cross-reactive human monoclonal antibodies and polyclonal sera. To improve ZIKV serodiagnosis, we employed wild type (WT) and FL or FL/BCL mutant virus-like particles (VLP) of ZIKV, DENV1 and West Nile virus (WNV) in enzyme linked immunosorbent assays (ELISA), and tested convalescent-phase serum or plasma samples from reverse-transcription PCR-confirmed cases with different ZIKV, DENV and WNV infections. For IgG ELISA, ZIKV WT-VLP had a sensitivity of 100% and specificity of 52.9%, which was improved to 83.3% by FL/BCL mutant VLP and 92.2% by the ratio of relative optical density of mutant to WT VLP. Similarly, DENV1 and WNV WT-VLP had a sensitivity/specificity of 100%/70.0% and 100%/56.3%, respectively; the specificity was improved to 93.3% and 83.0% by FL mutant VLP. For IgM ELISA, ZIKV, DENV1 and WNV WT-VLP had a specificity of 96.4%, 92.3% and 91.4%, respectively, for primary infection; the specificity was improved to 93.7–99.3% by FL or FL/BCL mutant VLP. An algorithm based on a combination of mutant and WT-VLP IgG ELISA is proposed to discriminate primary ZIKV, DENV and WNV infections as well as secondary DENV and ZIKV infection with previous DENV infections; this could be a powerful tool to better understand the seroprevalence and pathogenesis of ZIKV in regions where multiple flaviviruses co-circulate.

Surveillance and Epidemiology of Dengue in Medellín, Colombia from 2009 to 2017

Dengue is the most prevalent arthropod-borne viral disease in humans, primarily transmitted by the Aedes aegypti mosquito. We conducted a descriptive analysis of dengue cases from 2009 to 2017 in Medellín, Colombia, using data available from the Secretariat of Health. We analyzed the burden of outbreak years on the healthcare system, risk of cases exhibiting severe illness, potential disease surveillance problems, gender and age as risk factors, and spatiotemporal patterns of disease occurrence. Our data consisted of 50,083 cases, separated based on whether they were diagnostic test negative, diagnostic test positive (primarily IgM ELISA), clinically confirmed, epidemiologically linked, or probable. We used dengue incidence to analyze epidemiological trends between our study years, related to human movement patterns, between gender and age-groups, and spatiotemporally. We used risk to analyze the severity of dengue cases between the study years. We identified human movement could contributed to dengue spread, and male individuals (incidence rate: 0.86; 95% CI: 0.76-0.96) and individuals younger than 15 years (incidence rate: 1.24; 95% CI: 1.13-1.34) have higher incidence of dengue and located critical parts of the city where dengue incidence was high. Analysis was limited by participant diagnostic information, data concerning circulating strains, and a lack of phylogenetic information. Understanding the characteristics of dengue is a fundamental part of improving the health outcomes of at-risk populations. This analysis will be useful to support studies and initiatives to counteract dengue and provide context to the surveillance data collected by the health authorities in Medellín.

A graphene-based dengue immunosensor using plant-derived envelope glycoprotein domain III (EDIII) as the novel probe antigen

The envelope glycoprotein domain III (EDIII) of dengue virus (DENV) has been recognised as the antigenic region responsible for receptor binding. In the present work, we have proposed a novel immunosensor constructed on a graphene-coated screen-printed carbon electrode (SPCE) using plant-derived EDIII as the probe antigen to target DENV IgG antibodies. The developed immunosensor demonstrated high sensitivity towards DENV IgG within a wide linear working range (125-2000 ng mL^-1) under the optimised sensing conditions. The limit of detection was determined to be 22.5 ng mL^-1. The immunosensor also showed high specificity towards DENV IgG, capable of differentiating DENV IgG from the antibodies of other infectious diseases including the similarly structured Zika virus (ZIKV). The ability of the immunosensor to detect dengue antibodies in serum samples was also verified by conducting tests on mouse serum samples. The proposed immunosensor was able to provide a binary (positive/negative) response towards the serum samples comparable to the conventional enzyme-linked immunosorbent assay (ELISA), indicating promising potential for realistic applications.

Highly sensitive and specific graphene/TiO2 impedimetric immunosensor based on plant-derived tetravalent envelope glycoprotein domain III (EDIII) probe antigen for dengue diagnosis

This study reports on the development of a novel impedimetric immunosensor design using plant-derived antigenic glycoprotein for the detection of dengue virus (DENV) IgG antibodies. The electrochemical immunosensor platform was constructed using screen-printed carbon electrode (SPCE) modified with graphene/titanium dioxide (G/TiO₂) nanocomposite to improve the electrode in terms electrochemical performance and specific surface area. A plant-derived dengue envelope domain III (EDIII) protein was used as the antigenic probe protein in this immunosensing strategy. Under optimised sensing conditions, the immunosensor demonstrated high sensitivity towards DENV IgG in a wide linear working range (62.5-2000 ng/mL), with a limit of detection of 2.81 ng/mL. The immunosensor showed high specificity for discriminating DENV IgG against antibodies of other infectious disease, including the closely related Zika virus (ZIKV). The reliability of the immunosensor in serological diagnosis was verified by challenging the immunosensor against serum samples, compared to conventional enzyme-linked immunosorbent assay (ELISA). As shown by its remarkable performance throughout the study, the devised immunosensor is proposed as a reliable and practical diagnostic tool for the serological detection of dengue in realistic applications.

Highly Sensitive Detection of Zika Virus Nonstructural Protein 1 in Serum Samples by a Two-Site Nanobody ELISA

The Zika virus was introduced in Brazil in 2015 and, shortly after, spread all over the Americas. Nowadays, it remains present in more than 80 countries and represents a major threat due to some singularities among other flaviviruses. Due to its easy transmission, high percentage of silent cases, the severity of its associated complications, and the lack of prophylactic methods and effective treatments, it is essential to develop reliable and rapid diagnostic tests for early containment of the infection. Nonstructural protein 1 (NS1), a glycoprotein involved in all flavivirus infections, is secreted since the beginning of the infection into the blood stream and has proven to be a valuable biomarker for the early diagnosis of other flaviviral infections. Here, we describe the development of a highly sensitive nanobody ELISA for the detection of the NS1 protein in serum samples. Nanobodies were selected from a library generated from a llama immunized with Zika NS1 (ZVNS1) by a two-step high-throughput screening geared to identify the most sensitive and specific nanobody pairs. The assay was performed with a sub-ng/mL detection limit in the sera and showed excellent reproducibility and accuracy when validated with serum samples spiked with 0.80, 1.60, or 3.10 ng/mL of ZVNS1. Furthermore, the specificity of the developed ELISA was demonstrated using a panel of flavivirus’ NS1 proteins; this is of extreme relevance in countries endemic for more than one flavivirus. Considering that the nanobody sequences are provided, the assay can be reproduced in any laboratory at low cost, which may help to strengthen the diagnostic capacity of the disease even in low-resource countries.

A serological framework to investigate acute primary and post-primary dengue cases reporting across the Philippines

BACKGROUND

In dengue-endemic countries, targeting limited control interventions to populations at risk of severe disease could enable increased efficiency. Individuals who have had their first (primary) dengue infection are at risk of developing more severe secondary disease, thus could be targeted for disease prevention. Currently, there is no reliable algorithm for determining primary and post-primary (infection with more than one flavivirus) status from a single serum sample. In this study, we developed and validated an immune status algorithm using single acute serum samples from reporting patients and investigated dengue immuno-epidemiological patterns across the Philippines.

METHODS

During 2015/2016, a cross-sectional sample of 10,137 dengue case reports provided serum for molecular (anti-DENV PCR) and serological (anti-DENV IgM/G capture ELISA) assay. Using mixture modelling, we re-assessed IgM/G seroprevalence and estimated functional, disease day-specific, IgG:IgM ratios that categorised the reporting population as negative, historical, primary and post-primary for dengue. We validated our algorithm against WHO gold standard criteria and investigated cross-reactivity with Zika by assaying a random subset for anti-ZIKV IgM and IgG. Lastly, using our algorithm, we explored immuno-epidemiological patterns of dengue across the Philippines.

RESULTS

Our modelled IgM and IgG seroprevalence thresholds were lower than kit-provided thresholds. Individuals anti-DENV PCR+ or IgM+ were classified as active dengue infections (83.1%, 6998/8425). IgG- and IgG+ active dengue infections on disease days 1 and 2 were categorised as primary and post-primary, respectively, while those on disease days 3 to 5 with IgG:IgM ratios below and above 0.45 were classified as primary and post-primary, respectively. A significant proportion of post-primary dengue infections had elevated anti-ZIKV IgG inferring previous Zika exposure. Our algorithm achieved 90.5% serological agreement with WHO standard practice. Post-primary dengue infections were more likely to be older and present with severe symptoms. Finally, we identified a spatio-temporal cluster of primary dengue case reporting in northern Luzon during 2016.

CONCLUSIONS

Our dengue immune status algorithm can equip surveillance operations with the means to target dengue control efforts. The algorithm accurately identified primary dengue infections who are at risk of future severe disease.

Risk of dengue virus infection according to serostatus in individuals from dengue endemic areas of Mexico

The variability in the host immune response directed against dengue virus (DENV) has demonstrated the need to understand the immune response associated with protection in incident infection. The objective was to estimate the association between serostatus and the risk of incident DENV infection. We used a prospective study from 2014 to 2016 in the localities of Axochiapan and Tepalcingo, Morelos, Mexico. We recruited 966 participants, of which, according to their infection history registered were categorized in four groups. To accomplish the objectives of this study, we selected to 400 participants older than 5 years of age were followed for 2.5 years. Blood samples were taken every 6 months to measure serological status and infection by ELISA. In individuals with at least two previous infections the risk of new infection was lower compared to a seronegative group (hazard ratio adjusted 0.49, 95% CI 0.24-0.98), adjusted for age and locality. Therefore, individuals who have been exposed two times or more to a DENV infection have a lower risk of re-infection, thus showing the role of cross-immunity and its association with protection.

Dengue and Zika virus multi-epitope antigen expression in insect cells

Dengue virus and Zika virus are arthropod-borne flaviviruses that cause millions of infections worldwide. The co-circulation of both viruses makes serological diagnosis difficult as they share high amino acid similarities in viral proteins. Antigens are one of the key reagents in the differential diagnosis of these viruses through the detection of IgG antibodies in serological assays during the convalescent-phase of infections. Here, we report the expression of Dengue virus (DENV) and Zika virus (ZIKV) antigens containing non-conserved and immunodominant amino acid sequences using the baculovirus expression vector system in insect cells. We designed DENV and ZIKV antigens based on the domain III of the E protein (EDIII) after analyzing previously reported epitopes and by multiple alignment of the most important flaviviruses. The ZIKV and DENV multi-epitope genes were designed as tandem repeats or impaired repeats separated by tetra- or hexa-glycine linkers. The biochemical analyses revealed adequate expression of the antigens. Then, the obtained multi-epitope antigens were semi-purified in a sucrose gradient and tested using patients' sera collected during the convalescent-phase that were previously diagnosed positive for anti-DENV and -ZIKV IgG antibodies. The optimal serum dilution was 1:200, and the mean absorbance values in the preliminary tests show that multi-epitope antigens have been recognized by human sera. The production of both antigens using the multi-epitope strategy in the eukaryotic system and based on the EDIII regions provide a proof of concept for the use of antigens in the differentiation between DENV and ZIKV.

Spatiotemporal transmission dynamics of co-circulating dengue, Zika, and chikungunya viruses in Fortaleza, Brazil: 2011-2017

The mosquito-borne viruses dengue (DENV), Zika (ZIKV), and chikungunya (CHIKV), now co-endemic in the Americas, pose growing threats to health worldwide. However, it remains unclear whether there exist interactions between these viruses that could shape their epidemiology. This study advances knowledge by assessing the transmission dynamics of co-circulating DENV, ZIKV, and CHIKV in the city of Fortaleza, Brazil. Spatiotemporal transmission dynamics of DENV, ZIKV, and CHIKV were analyzed using georeferenced data on over 210,000 reported cases from 2011 to 2017 in Fortaleza, Brazil. Local spatial clustering tests and space-time scan statistics were used to compare transmission dynamics across all years. The transmission of co-circulating viruses in 2016 and 2017 was evaluated at fine spatial and temporal scales using a measure of spatiotemporal dependence, the τ-statistic. Results revealed differences in the diffusion of CHIKV compared to previous DENV epidemics and spatially distinct transmission of DENV/ZIKV and CHIKV during the period of their co-circulation. Significant spatial clustering of viruses of the same type was observed within 14-day time intervals at distances of up to 6.8 km (p<0.05). These results suggest that arbovirus risk is not uniformly distributed within cities during co-circulation. Findings may guide outbreak preparedness and response efforts by highlighting the clustered nature of transmission of co-circulating arboviruses at the neighborhood level. The potential for competitive interactions between the arboviruses should be further investigated.

A review of dengue diagnostics and implications for surveillance and control

Dengue is the world’s most common arboviral infection, with almost 4 billion people estimated to be living at risk of dengue infection. A recently introduced vaccine is currently recommended only for seropositive individuals in a restricted age range determined by transmission intensity. With no effective dengue vaccine for the general population or any antiviral therapy, dengue control continues to rely heavily on vector control measures. Early and accurate diagnosis is important for guiding appropriate management and for disease surveillance to guide prompt dengue control interventions. However, major uncertainties exist in dengue diagnosis and this has important implications for all three. Dengue can be diagnosed clinically against predefined lists of signs and symptoms and by detection of dengue-specific antibodies, non-structural 1 antigen or viral RNA by reverse transcriptase–polymerase chain reaction. All of these methods have their limitations. This review aims to describe and quantify the advantages, uncertainties and variability of the various diagnostic methods used for dengue and discuss their implications and applications for dengue surveillance and control.

Neurological complications associated with emerging viruses in Brazil

Objective

To test the hypotheses that emerging viruses are associated with neurological hospitalizations and that statistical models can be used to predict neurological sequelae from viral infections.

Methods

An ecological study was carried out to observe time trends in the number of hospitalizations with inflammatory polyneuropathy and Guillain‐Barré syndrome (GBS) in the state of Rio de Janeiro from 1997 to 2017. Increases in GBS from month to month were assessed using a Farrington test. In addition, a cross‐sectional study was conducted analyzing 50 adults hospitalized for inflammatory polyneuropathies from 2015 to 2017. The extent to which Zika virus symptoms explained GBS hospitalizations was evaluated using a calibration test.

Results

There were significant increases (Farrington test, P<0.001) in the incidence of GBS following the introduction of influenza A/H1N1 in 2009, dengue virus type 4 in 2013, and Zika virus in 2015. Of 50 patients hospitalized, 14 (28.0%) were diagnosed with arboviruses, 9 (18.0%) with other viruses, and the remainder with other causes of such neuropathies. Statistical models based on cases of emerging viruses accurately predicted neurological sequelae, such as GBS.

Conclusion

The introduction of novel viruses increases the incidence of inflammatory neuropathies.

The introduction of novel viruses increases the incidence of inflammatory neuropathies in Brazil.

Specificity of NS1-based immunochromatographic tests for dengue virus with regard to the Zika virus protein

OBJECTIVES

This study was performed to determine whether Dengue virus (DENV) immunochromatographic tests can detect and differentiate nonstructural protein 1 (NS1) from each of the four DENV serotypes and do not cross-react with the Zika virus (ZIKV) NS1 protein.

METHODS

We compared the specificity of six NS1-based DENV immunochromatographic tests (point of care) in the detection of NS1 proteins from each of the four DENV serotypes and ZIKV. The tests were performed with NS1 proteins produced in mammalian cells. Cross-reactivity was confirmed with a purified recombinant ZIKV NS1 protein and DENV⁺ or ZIKV⁺ human serum samples.

RESULTS

Cross-reaction was observed in 2 out of the 6 evaluated tests using cell culture supernatants containing NS1 protein of each tested virus. Cross-reactivity with ZIKV was confirmed with purified recombinant ZIKV NS1 produced in Escherichia coli. Further analyses with serum samples collected from DENV⁺ or ZIKV⁺ patients confirmed the cross-reactivity with ZIKV protein in 2 tests.

CONCLUSIONS

The detection of the NS1 protein is the basis for several commercially available serological DENV diagnostic tests. The present results emphasize the relevance of testing specificity of presently available NS1-based DENV serological tests and the need of adjustments of tests that cross-react with the ZIKV protein. Our results are particularly relevant for regions where both viruses are endemically found, as in the case of Brazil.

Evaluation and optimisation of commercial Zika IgG avidity assay

BACKGROUND

ZIKV infection has potentially severe consequences particularly in fetuses/newborns born to mothers that were infected early in pregnancy. Diagnosis relies on the detection of ZIKV IgM that can also be detected due to cross reactivity or to nonspecific polyclonal activation of the immune system. Therefore, in case of ZIKV IgM detection, identification of a recent infection can be of major importance for the optimal management of pregnant women.

OBJECTIVE

This study evaluates the performances of a commercially available assay to measure ZIKV-IgG avidity.

STUDY DESIGN

A total of 110 serum or plasma samples collected from symptomatic or asymptomatic patients living or returning from a ZIKV endemic area were classified according to epidemiological and clinical information, and to serology and molecular assays' results. Samples were tested with the IgG ZIKV Avidity Test (DIA.PRO®) according to manufacturer's instruction and with a modified protocol.

RESULTS

By using the manufacturer's Avidity Index cut-off, distinction between recent and past infection was unclear with similar AIs in the two situations (p = 0.8872). Sensitivity and specificity in identifying recent infection were poor, 67.3 % and 4.5 % respectively. By using a modified protocol, a better discrimination was observed with significant differences between mean AIs (p = 0.0318), and with higher sensitivity and specificity, respectively 87.8 % and 100 %.

CONCLUSION

Our results highlight that IgG ZIKV Avidity Test DIA.PRO® assay is not reliable enough to be used in clinical practice without modifications.

Serological tests reveal significant cross-reactive human antibody responses to Zika and Dengue viruses in the Mexican population

Zika virus (ZIKV) is a mosquito-borne flavivirus that has caused recent large outbreaks in the Americas. Given its association with severe congenital defects including microcephaly, distinguishing infections caused by ZIKV from those caused by dengue virus (DENV) is of primordial importance. The objectives of this study were to evaluate the recombinant proteins rEIII-ZIKV (Envelope protein domain III) and rNS1ß-leader-ZIKV (non-structural protein 1) for the serological diagnosis of ZIKV in the Mexican population. We also evaluated potential cross-reactivity in commercial enzyme-linked immunosorbent assays (ELISA) based on the ZIKV NS1 and DENV NS1 proteins. rEIII-ZIKV and rNS1ß-leader-ZIKV proteins were tested with sera from 30 PCR-confirmed ZIKV cases, 50 ZIKV-naive, DENV-exposed subjects with no acute febrile disease, (asymptomatic subjects, AS), and 50 ZIKV-naive and DENV naive AS. Commercial ELISA tests were evaluated with sera from 57 ZIKV and 20 DENV PCR-confirmed cases, and 50 ZIKV-naive, DENV-exposed AS. In-house ELISA assays showed that IgM antibody levels against rEIII-ZIKV and rNS1ß-ZIKV were higher in ZIKV naive, DENV-exposed AS than in acutely infected ZIKV individuals. IgG reactivity was highest for rEIII-ZIKV, and indistinguishable between acutely infected ZIKV cases and DENV exposed AS. Positivity for the Euroimmun Zika IgM assay at 7-10 days was considerably higher in DENV-naive ZIKV patients (86%) than in DENV-exposed ZIKV patients (33%), while 39% of the latter had false-negative anti-ZIKV IgG before 7 days of onset. DENV-exposed ZIKV patients presented lower anti-ZIKV IgM and higher IgG responses similar to a secondary dengue response. Forty-four percent of DENV- exposed acute ZIKV patients were DENV IgM positive with the Panbio Dengue assay, and two (15%) of the DENV-naive ZIKV patients presented false DENV IgG conversion. Given the extensive cross-reactivity to both the NS1 and EDIII proteins in current serological methods, the development of sensitive and specific serological tests to distinguish ZIKV from DENV infections is an urgent priority.

Optimization and scale-up production of Zika virus ΔNS1 in Escherichia coli: application of Response Surface Methodology

Diagnosing Zika virus (ZIKV) infections has been challenging due to the cross-reactivity of induced antibodies with other flavivirus. The concomitant occurrence of ZIKV and Dengue virus (DENV) in endemic regions requires diagnostic tools with the ability to distinguish these two viral infections. Recent studies demonstrated that immunoassays using the C-terminal fragment of ZIKV NS1 antigen (ΔNS1) can be used to discriminate ZIKV from DENV infections. In order to be used in serological tests, the expression/solubility of ΔNS1 and growth of recombinant E. coli strain were optimized by Response Surface Methodology. Temperature, time and IPTG concentration were evaluated. According to the model, the best condition determined in small scale cultures was 21 °C for 20 h with 0.7 mM of IPTG, which predicted 7.5 g/L of biomass and 962 mg/L of ΔNS1. These conditions were validated and used in a 6-L batch in the bioreactor, which produced 6.4 g/L of biomass and 500 mg/L of ΔNS1 in 12 h of induction. The serological ELISA test performed with purified ΔNS1 showed low cross-reactivity with antibodies from DENV-infected human subjects. Denaturation of ΔNS1 decreased the detection of anti-ZIKV antibodies, thus indicating the contribution of conformational epitopes and confirming the importance of properly folded ΔNS1 for the specificity of the serological analyses. Obtaining high yields of soluble ΔNS1 supports the viability of an effective serologic diagnostic test capable of differentiating ZIKV from other flavivirus infections.

Loop-Mediated Isothermal Amplification (LAMP) for the Diagnosis of Zika Virus: A Review

The recent outbreak of Zika virus (ZIKV) in the Americas and its devastating developmental and neurological manifestations has prompted the development of field-based diagnostics that are rapid, reliable, handheld, specific, sensitive, and inexpensive. The gold standard molecular method for lab-based diagnosis of ZIKV, from either patient samples or insect vectors, is reverse transcription-quantitative polymerase chain reaction (RT-qPCR). The method, however, is costly and requires lab-based equipment and expertise, which severely limits its use as a point-of-care (POC) tool in resource-poor settings. Moreover, given the lack of antivirals or approved vaccines for ZIKV infection, a POC diagnostic test is urgently needed for the early detection of new outbreaks and to adequately manage patients. Loop-mediated isothermal amplification (LAMP) is a compelling alternative to RT-qPCR for ZIKV and other arboviruses. This low-cost molecular system can be freeze-dried for distribution and exhibits high specificity, sensitivity, and efficiency. A growing body of evidence suggests that LAMP assays can provide greater accessibility to much-needed diagnostics for ZIKV infections, especially in developing countries where the ZIKV is now endemic. This review summarizes the different LAMP methods that have been developed for the virus and summarizes their features, advantages, and limitations.

Recombination of B- and T-cell epitope-rich loci from Aedes- and Culex-borne flaviviruses shapes Zika virus epidemiology

Sporadic human Zika virus (ZIKV) infections have been recorded in Africa and Asia since the 1950s. Major epidemics occurred only after ZIKV emerged in the Pacific islands and spread to the Americas. Specific biological determinants of the explosive epidemic nature of ZIKV have not been identified. Phylogenetic studies revealed incongruence in ZIKV placement in relation to Aedes-borne dengue viruses (DENV) and Culex-borne flaviviruses. We hypothesized that this incongruence reflects interspecies recombination resulting in ZIKV evasion of cross-protective T-cell immunity. We investigated ZIKV phylogenetic incongruence in relation to: DENV T-cell epitope maps experimentally identified ex vivo, published B-cell epitope loci, and CD8⁺ T-cell epitopes predicted in silico for mosquito-borne flaviviruses. Our findings demonstrate that the ZIKV proteome is a hybrid of Aedes-borne DENV proteins interspersed amongst Culex-borne flavivirus proteins derived through independent interspecies recombination events. These analyses infer that DENV-associated proteins in the ZIKV hybrid proteome generated immunodominant human B-cell responses, whereas ZIKV recombinant derived Culex-borne flavivirus-associated proteins generated immunodominant CD8⁺ and/or CD4⁺ T-cell responses. In silico CD8⁺ T-cell epitope ZIKV cross-reactive prediction analyses verified this observation. We propose that by acquiring cytotoxic T-cell epitope-rich regions from Culex-borne flaviviruses, ZIKV evaded DENV-generated T-cell immune cross-protection. Thus, Culex-borne flaviviruses, including West Nile virus and Japanese encephalitis virus, might induce cross-protective T-cell responses against ZIKV. This would explain why explosive ZIKV epidemics occurred in DENV-endemic regions of Micronesia, Polynesia and the Americas where Culex-borne flavivirus outbreaks are infrequent and why ZIKV did not cause major epidemics in Asia where Culex-borne flaviviruses are widespread.