Screening and exclusion of Zika virus infection in travellers by an NS1-based ELISA and qRT-PCR

ICP-MS and fluorescence dual-mode detection of ZIKV-RNA based on quantum dot labeling with hybridization chain reaction

The detection of Zika virus (ZIKV) is of great significance to human life and health. Herein, we presented an ICP-MS and fluorescent dual-mode sensor for quantitative analysis of Zika virus RNA fragments (ZIKV-RNA), which employed quantum dots (QDs) as signal tags and combined with hybridization chain reaction (HCR). The dual-mode sensor realized cross-checking of the analysis results and improved the assay accuracy. Firstly, the single-stranded DNA (ssDNA) was anchored on the surface of magnetic beads (MBs). Afterward, HCR was conducted with probe DNA-CdSe quantum dots conjugates (pDNA-QDs) and link DNA (lDNA), producing the MBs-ssDNA-[pDNA-QDs-lDNA]n conjugates. In the presence of target ZIKV-RNA, a strand displacement reaction occurred, leading to the dissociation of the [pDNA-QDs-lDNA]n labels from the conjugates into the solution. Finally, the signal intensity was detected using ICP-MS and fluorescence analysis, with achieved limits of detection of 131 pM and 152 pM, respectively. The inter-assay RSD values of fluorescence and ICP-MS were 3.94 % and 4.26 % at 10 nM level, respectively, showing that the method had good precision. This method showed high selectivity and was applied to the analysis of biological fluids. There was no significant difference between the results of ICP-MS modes and fluorescence mode. This method offers a new strategy for sensitivity analysis of ZIKV-RNA and exhibits promise in clinical applications for diagnosis.

The Role of NS1 Protein in the Diagnosis of Flavivirus Infections

Nonstructural protein 1 (NS1) is a glycoprotein among the flavivirus genus. It is found in both membrane-associated and soluble secreted forms, has an essential role in viral replication, and modulates the host immune response. NS1 is secreted from infected cells within hours after viral infection, and thus immunodetection of NS1 can be used for early serum diagnosis of dengue fever infections instead of real-time (RT)-PCR. This method is fast, simple, and affordable, and its availability could provide an easy point-of-care testing solution for developing countries. Early studies show that detecting NS1 in cerebrospinal fluid (CSF) samples is possible and can improve the surveillance of patients with dengue-associated neurological diseases. NS1 can be detected postmortem in tissue specimens. It can also be identified using noninvasive methods in urine, saliva, and dried blood spots, extending the availability and effective detection period. Recently, an enzyme-linked immunosorbent assay (ELISA) assay for detecting antibodies directed against Zika virus NS1 has been developed and used for diagnosing Zika infection. This NS1-based assay was significantly more specific than envelope protein-based assays, suggesting that similar assays might be more specific for other flaviviruses as well. This review summarizes the knowledge on flaviviruses' NS1's potential role in antigen and antibody diagnosis.

The endogenous factors affecting the detection of serum SARS-CoV-2 IgG/IgM antibodies by ELISA

To investigate endogenous interference factors of the detection results of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgM/IgG. Enzyme-linked immunosorbent assay (ELISA) was used to detect SARS-CoV-2 IgM/IgG in sera of 200 patients without COVID-19 infection, including rheumatoid factor (RF) positive group, antinuclear antibody (ANA) positive group, pregnant women group and normal senior group, with 50 in each group and 100 normal controls. The level of SARS-CoV-2 IgG in pregnant women was significantly higher than that in normal control group (P = 0.000), but there was no significant difference between other groups. The levels of SARS-CoV-2 IgM in pregnant women group, normal senior group, ANA positive group and RF positive group were significantly higher than that in normal control group (P<0.05), with significant higher false positive rates in these groups (P = 0.036, P = 0.004, P = 0.000, vs normal control group). Serum RF caused SARS-CoV-2 IgM false-positive in concentration dependent manner, especially when its concentration was higher than 110.25 IU/L, and urea dissociation test can turn the false positive to negative. ANA, normal seniors, pregnant women and RF can lead to false-positive reactivity of SARS-CoV-2 IgM and/or IgG detected using ELISA. These factors should be considered when SARS-CoV-2 IgM or IgG detection is positive, false positive samples caused by RF positive can be used for urea dissociation test. This article is protected by copyright. All rights reserved.

NS1 glycoprotein detection in serum and urine as an electrochemical screening immunosensor for dengue and Zika virus

The incidence of infection by the dengue virus (DENV) has grown dramatically, reaching 128 countries in tropical and subtropical regions worldwide, with a pattern of hyper-endemicity. DENV is a mosquito-borne disease having four serotypes, one or two circulating in epidemic outbreaks. The diagnosis of DENV is challenging mainly due to the circulation of new viruses with remarkable similarities, such as Zika (ZIKV) that may cause fetal microcephaly. DENV affects 390 million people per year, but these numbers may be higher due to the underreported and misclassified cases. Recently, the NS1 nonstructural protein has been described in serum and urine of DENV and ZIKV patients, suggesting its use as a biomarker for screening since a negative NS1 sample confirms the absence of these infections. Herein, a label-free immunosensor comprising an assembled nanostructured thin film of carbon nanotube-ethylenediamine is described. The advantage of in situ electrosynthesis of polymer film is to allow major control of thickness and conductivity, in addition to designing the reactive groups for functionalization. A quartz crystal microbalance system was used to estimate the thickness of the polymeric film obtained. The anti-NS1 monoclonal antibodies were immobilized to carbon nanotubes by covalent linkage, permitting a high stability during measurements. Analytical responses to NS1 were obtained by differential pulse voltammetry (DPV), showing a linear range from 20 to 800 ng mL^-1 and reproducibility of 3.0%, with a limit of detection (LOD) of 6.8 ng mL^{- 1}. This immunosensor was capable of detecting ZIKV and DENV NS1 in spiked urine and real serum in a clinical range.Graphical abstract.

High Seroprevalence of Antibodies against Arboviruses among Pregnant Women in Rural Caribbean Colombia in the Context of the Zika Virus Epidemic

Mosquito-borne viruses such as dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV) have spread in recent decades. We aimed to assess seroprevalence of arboviral infections in pregnant women living in Cereté, Caribbean Colombia. In 2016 a cross-sectional facility-based sero-survey study was performed among pregnant women (N = 90). Most of them (66%) reported at least one symptom or sign compatible with arboviral infection over the previous 15 days. All screened women had a positive IgG for DENV, 89% for ZIKV, and 82% for CHIKV. One woman tested positive for ZIKV IgM. This study shows the high exposure among pregnant women to arboviruses in endemic areas, shown by the high seroprevalence of past arboviral infections. Given the evidence on the potential risks of these arboviral infections on pregnancy and infant outcomes, these results highlight the need for continuous epidemiological surveillance of arboviral diseases, particularly among those most of risk of their harmful consequences.