Evaluation of the Diasorin Liaison® XL Zika Capture IgM CMIA for Zika virus serological testing

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.

Coronavirus Disease 2019 (COVID-19) Diagnostic Tools: A Focus on Detection Technologies and Limitations

The ongoing coronavirus disease (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses a severe threat to human health and the global economy and has resulted in overwhelming stress on health care systems worldwide. Despite the global health catastrophe, especially in the number of infections and fatalities, the COVID-19 pandemic has also revolutionized research and discovery with remarkable success in diagnostics, treatments, and vaccine development. The use of many diagnostic methods has helped establish public health guidelines to mitigate the spread of COVID-19. However, limited information has been shared about these methods, and there is a need for the scientific community to learn about these technologies, in addition to their sensitivity, specificity, and limitations. This review article is focused on providing insights into the major methods used for SARS-CoV-2 detection. We describe in detail the core principle of each method, including molecular and serological approaches, along with reported claims about the rates of false negatives and false positives, the types of specimens needed, and the level of technology and the time required to perform each test. Although this study will not rank or prioritize these methods, the information will help in the development of guidelines and diagnostic protocols in clinical settings and reference laboratories.

Co-circulation and misdiagnosis led to underestimation of the 2015-2017 Zika epidemic in the Americas

During the 2015-2017 Zika epidemic, dengue and chikungunya-two other viral diseases with the same vector as Zika-were also in circulation. Clinical presentation of these diseases can vary from person to person in terms of symptoms and severity, making it difficult to differentially diagnose them. Under these circumstances, it is possible that numerous cases of Zika could have been misdiagnosed as dengue or chikungunya, or vice versa. Given the importance of surveillance data for informing epidemiological analyses, our aim was to quantify the potential extent of misdiagnosis during this epidemic. Using basic principles of probability and empirical estimates of diagnostic sensitivity and specificity, we generated revised estimates of reported cases of Zika that accounted for the accuracy of diagnoses made on the basis of clinical presentation with or without laboratory confirmation. Applying this method to weekly reported case data from 43 countries throughout Latin America and the Caribbean, we estimated that 944,700 (95% CrI: 884,900-996,400) Zika cases occurred when assuming all confirmed cases were diagnosed using molecular methods versus 608,400 (95% CrI: 442,000-821,800) Zika cases that occurred when assuming all confirmed cases were diagnosed using serological methods. Our results imply that misdiagnosis was more common in countries with proportionally higher reported cases of dengue and chikungunya, such as Brazil. Given that Zika, dengue, and chikungunya appear likely to co-circulate in the Americas and elsewhere for years to come, our methodology has the potential to enhance the interpretation of passive surveillance data for these diseases going forward. Likewise, our methodology could also be used to help resolve transmission dynamics of other co-circulating diseases with similarities in symptomatology and potential for misdiagnosis.

Recent progresses and remaining challenges for the detection of Zika virus

Zika virus (ZIKV) has emerged as a particularly notorious mosquito-borne flavivirus, which can lead to a devastating congenital syndrome in the fetuses of pregnant mothers (e.g., microcephaly, spasticity, craniofacial disproportion, miscarriage, and ocular abnormalities) and cause the autoimmune disorder Guillain-Barre' syndrome of adults. Due to its severity and rapid dispersal over several continents, ZIKV has been acknowledged to be a global health concern by the World Health Organization. Unfortunately, the ZIKV has recently resurged in India with the potential for devastating effects. Researchers from all around the world have worked tirelessly to develop effective detection strategies and vaccines for the prevention and control of ZIKV infection. In this review, we comprehensively summarize the most recent research into ZIKV, including the structural biology and evolution, historical overview, pathogenesis, symptoms, and transmission. We then focus on the detection strategies for ZIKV, including viral isolation, serological assays, molecular assays, sensing methods, reverse transcription loop mediated isothermal amplification, transcription-mediated amplification technology, reverse transcription strand invasion based amplification, bioplasmonic paper-based device, and reverse transcription isothermal recombinase polymerase amplification. To conclude, we examine the limitations of currently available strategies for the detection of ZIKV, and outline future opportunities and research challenges.

An antibody panel for highly specific detection and differentiation of Zika virus

Zika virus (ZIKV) is an emerging flavivirus transmitted to humans by Aedes mosquitos. ZIKV can be transmitted from mother to fetus during pregnancy and can cause microcephaly and other birth defects. Effective vaccines for Zika are yet to be approved. Detection of the ZIKV is based on serological testing that often shows cross-reactivity with the Dengue virus (DENV) and other flaviviruses. We aimed to assemble a highly specific anti-Zika antibody panel to be utilized in the development of a highly specific and cost-effective ZIKV rapid quantification assay for viral load monitoring at point-of-care settings. To this end, we tested the affinity and specificity of twenty one commercially available monoclonal and polyclonal antibodies against ZIKV and DENV envelope proteins utilizing nine ZIKV and twelve DENV strains. We finalized and tested a panel of five antibodies for the specific detection and differentiation of ZIKV and DENV infected samples.

Evaluation of the LIAISON XL Zika Capture IgM II for the Diagnosis of Zika Virus Infections

The aim of this study is to evaluate the performance characteristics of the LIAISON XL Zika Capture IgM II. For this purpose we tested 128 samples obtained from recent infections caused by the Zika (ZIKV; 74 samples), dengue (DENV; 10 samples), chikungunya (CHIK V; 11 samples), rubella (RUBV; 10 samples) and measles (MeV; 10 samples) viruses, as well as human parvovirus B19 (HPVB19; 13 samples). The results of the assay under evaluation are compared with those obtained from an indirect immunofluorescence (IIF) assay, and the discrepancies are resolved by considering other laboratory results (PCR and a plaque-reduction neutralization test). The LIAISON showed excellent sensitivity (100%). The specificity (91.25%) was hampered by some false-positive results in recent dengue virus, chikungunya virus, measles virus and human parvovirus B19 infections. The method evaluated is adequate, but the low specificity makes it necessary to consider the clinical and epidemiological contexts of patients, as well as other laboratory results.

Zika virus: an emerging challenge to public health worldwide

Zika virus (ZIKV) is a mosquito-borne virus that was first isolated from Zika forest, Uganda, in 1947. Since its inception, major and minor outbreaks have been documented from several parts of world. Aedes spp. mosquitoes are the primary vectors of ZIKV, but the virus can also be transmitted through sexual practices, materno-fetal transmission, and blood transfusion. The clinical presentations of symptomatic ZIKV infections are similar to dengue and chikungunya, including fever, headache, arthralgia, retro-orbital pain, conjunctivitis, and rash. ZIKV often causes mild illness in the majority of cases, but in some instances, it is linked with congenital microcephaly and autoimmune disorders like Guillain-Barré syndrome. The recent Indian ZIKV outbreak suggests that the virus is circulating in the South East Asian region and may cause new outbreaks in future. At present, no specific vaccines or antivirals are available to treat ZIKV, so management and control of ZIKV infections rely mostly on preventive measures.

Detecting Vertical Zika Transmission: Emerging Diagnostic Approaches for an Emerged Flavivirus

Zika virus (Zika) was recently responsible for a massive epidemic that spread throughout Latin America and beyond. Though Zika is typically asymptomatic or self-limiting, the sheer numbers of Zika infections led to the identification of unexpected phenotypes including sexual transmission, Guillain-Barré syndrome, and teratogenicity. Thousands of infants in South, Central, and North America have now been born with microcephaly or one of a number of fetal anomalies constituting the congenital Zika syndrome (CZS). Diagnosing CZS is based on a combination of clinical risk assessment and laboratory testing (which includes determining whether the mother has experienced a possible Zika infection during her pregnancy). A newborn suspected of having congenital Zika infection (due to maternal Zika infection or a birth defect described in association with congenital Zika infection) is then specifically tested for presence of Zika virus in neonatal tissue or anti-Zika IgM in the blood or cerebrospinal fluid. Though the guidelines are clear, there is room for considerable practice variation to emerge from individualized patient-provider encounters, largely due to limitations in diagnostic testing for Zika. The natural history of Zika further obscures our ability to know who, when, and how to test. Molecular diagnostics are highly specific but may not serve well those with asymptomatic infection. Serologic assays expand the diagnostic window but are complicated by cross-reactivity among related flaviviruses and passive immunity transferred from mother to baby. Furthermore, existing and emerging diagnostic tools may not be widely available due to limitations in resources and infrastructure of health systems in affected areas. Improvements in assay parameters as well as advances in platforms and deployability hold promise for optimizing diagnostic approaches for congenital Zika infection. The diagnostic tools and technologies under development must be integrated with forthcoming clinical knowledge of congenital Zika infection to fully realize the value that laboratory testing holds for diagnosing in utero mother to child transmission but also for understanding, predicting, and managing the health outcomes due to congenital Zika infection.

Performance of InBios ZIKV Detect™ 2.0 IgM Capture ELISA in two reference laboratories compared to the original ZIKV Detect™ IgM Capture ELISA

ZIKV Detect™ 2.0 IgM Capture ELISA (InBios International, Seattle, WA) recently replaced the ZIKV Detect™ IgM Capture ELISA and a number of significant changes have been made to the original version. This study compares data generated from the ZIKV Detect™ 2.0 IgM Capture ELISA, to data generated using the original version of the kit. The same sample sets were used in this comparison, and reference test results for these samples were used to assess sensitivity, specificity, accuracy and concordance of results across two laboratories. Average sensitivity increased from 90.4% to 92.5% with the updated kit where the increase was not statistically different, and specificity increased from 79.5% to 97.4%, a statistically-significant difference. Accuracy of the ZIKV Detect™ 2.0 IgM Capture ELISA was 89% compared to 63.9% for the original version of the kit, and agreement across the laboratories increased from 79.5% to 97.4%. With secondary dengue virus infections, specificity increased from 9.3% to 82.6% with the updated kit, primarily due to the change in interpretation criteria that no longer includes “Possible Zika positive.”

Performance evaluation of the Diasorin LIAISON® XL Zika capture IgM CLIA test

Because Zika virus (ZIKV) can cause serious birth defects and is involved in cases of Guillain-Barré syndrome, the ZIKV outbreak in the American continent in 2015 resulted in an enormous need for ZIKV diagnostic tools. We evaluated the LIAISON® XL Zika Capture IgM test on 106 samples from patients, mainly travelers, with a confirmed or probable ZIKV infection. Sensitivity between 0 and 84 days after onset of symptoms was 92.5%. Specificity was evaluated on a panel of 56 samples known to cause possible cross-reactions. Cross-reaction with DENV antibodies was limited (10.5%) but false-positive results occurred in samples from patients with malaria, CMV and EBV infections.

Serologic Tools and Strategies to Support Intervention Trials to Combat Zika Virus Infection and Disease

Zika virus is an emerging mosquito-borne flavivirus that recently caused a large epidemic in Latin America characterized by novel disease phenotypes, including Guillain-Barré syndrome, sexual transmission, and congenital anomalies, such as microcephaly. This epidemic, which was declared an international public health emergency by the World Health Organization, has highlighted shortcomings in our current understanding of, and preparation for, emerging infectious diseases in general, as well as challenges that are specific to Zika virus infection. Vaccine development for Zika virus has been a high priority of the public health response, and several candidates have shown promise in pre-clinical and early phase clinical trials. The optimal selection and implementation of imperfect serologic assays are among the crucial issues that must be addressed in order to advance Zika vaccine development. Here, I review key considerations for how best to incorporate into Zika vaccine trials the existing serologic tools, as well as those on the horizon. Beyond that, this discussion is relevant to other intervention strategies to combat Zika and likely other emerging infectious diseases.

Evaluation of a Rapid Immunochromatographic Assay and Two Enzyme-Linked Immunosorbent Assays for Detection of IgM-Class Antibodies to Zika Virus

There are currently five serologic assays available for detection of anti-Zika virus (ZIKV) IgM-class antibodies with U.S. Food and Drug Administration emergency use authorization. Among these are the Chembio DPP Zika IgM system (DPP Zika ICA; Chembio, Medford, NY), a rapid immunochromatographic assay (ICA), and the InBios ZIKV Detect 2.0 IgM antibody capture enzyme-linked immunosorbent assay (ZIKV 2.0 MAC-ELISA; InBios international, Inc., Seattle, WA), which has replaced the original InBios ZIKV Detect MAC-ELISA. We evaluated performance of these three serologic assays using 72 specimens characterized by plaque reduction neutralization testing (PRNT) for the presence or absence of neutralizing antibodies (NAbs) to ZIKV, dengue virus (DENV), and West Nile virus (WNV). The InBios ZIKV 2.0 MAC-ELISA was "presumptive Zika positive" in all 15 PRNT-confirmed ZIKV samples, while the Chembio DPP Zika ICA was nonreactive in three (20%) and the InBios ZIKV MAC-ELISA was negative in four (27%). The Chembio DPP Zika ICA and InBios ZIKV 2.0 MAC-ELISA showed >95% specificity in 22 ZIKV/DENV-seronegative specimens and in 13 samples positive for NAbs to non-ZIKV flaviviruses. Comparatively, the InBios ZIKV MAC-ELISA was "presumptive" or "possible Zika positive" in 8 of 12 WNV or DENV PRNT-positive samples and in 12 of 22 PRNT-seronegative sera. Our findings suggest that replacement of the InBios ZIKV MAC-ELISA with the InBios ZIKV 2.0 MAC-ELISA will lead to fewer samples requiring PRNT, minimizing unnecessary anxiety among patients ultimately determined to be seronegative for ZIKV and DENV by PRNT and alleviating some of the testing burden on laboratories performing PRNT.

Diagnostic Testing for Zika Virus: a Postoutbreak Update

Since the emergence and dissemination of Zika virus (ZIKV) in late 2015, our understanding of the biology, transmission, clinical disease, and potential sequelae associated with infection has markedly expanded. Over the past 2 years, the number of diagnostic assays for ZIKV has increased from none in 2015 to 5 serological assays and 14 molecular assays in 2017, all with emergency use authorization granted through the U.S. Food and Drug Administration. Here we provide an update on ZIKV, addressing what we have collectively learned since the outbreak began, including a summary of currently available diagnostic assays for this virus.

Development of Zika Virus Serological Testing Strategies in New York State

The recent outbreak of Zika virus (ZIKV) in the Americas has challenged diagnostic laboratory testing strategies. At the Wadsworth Center, ZIKV serological testing was performed for over 10,000 specimens, using a combination of an enzyme-linked immunosorbent assay (ELISA) for IgM antibodies (Abs) to ZIKV, a polyvalent microsphere immunoassay (MIA) to detect Abs broadly reactive with flaviviruses, and a plaque reduction neutralization test (PRNT) for further testing. Overall, 42% of patients showed serological evidence of flavivirus infection (primarily past dengue virus [DENV] infection), while 7% possessed IgM Abs to ZIKV and/or DENV. ZIKV IgM Abs typically arose within 3 to 4 days, with only one instance of duration beyond 100 days after reported symptoms. PRNT analysis of 826 IgM-positive specimens showed 7% positive neutralization to ZIKV alone, 9% to DENV alone, and 85% to both ZIKV and DENV. Thus, the extensive Ab cross-reactivity among flaviviruses significantly reduced the value of performing PRNT analysis, especially when a traditional paired serum algorithm with viral neutralization titering was used. Nevertheless, the finding of a negative ZIKV result by PRNT was invaluable for reassuring both physicians and patients. The MIA detected both IgM and IgG, which enabled us to identify patients who presented without IgM anti-ZIKV Abs but still had ZIKV-specific neutralizing Abs. On the basis of these results, a new algorithm, which included an IgM Ab capture (MAC)-ELISA to detect recent infection, a flavivirus MIA to identify patients no longer producing IgM, and a single-dilution PRNT for ZIKV exclusion and occasional discrimination of ZIKV and DENV, was implemented.