Compensating for cross-reactions using avidity and computation in a suspension multiplex immunoassay for serotyping of Zika versus other flavivirus infections

Zika virus screening during pregnancy: Results and lessons learned from a screening program and a post-delivery follow-up analysis (2016-2022)

OBJECTIVE

To evaluate a Zika virus screening program applied to asymptomatic exposed pregnant women.

METHODOLOGY

Analysis of data generated during the roll out of a Zika screening program. We included socio-demographic data, ultrasounds, and serological results (IgM, IgG, and Plaque Reduction Neutralization Test; PRNT) from asymptomatic pregnant women exposed to Zika virus enrolled in the screening program between 2016 to 2019.

RESULTS

We included 406 asymptomatic ZIKV-exposed pregnant women who gave 400 full-term new-borns. The median age was 30 years (IQR = 25-34), which was lower (29 years; IQR = 24-34) among women of non-EU migrant origin (76.4% of the sample). Migrant women tended to delay the first pre-natal consultation compared to EU origin women (p = .003). Overall, 83.2% (N = 328) of participants had ZIKV low risk serological profile (IgM-/IgG- or IgM-/IgG+ and PRNT-), 3.0% (N = 12) showed high risk of recent ZIKV infection (IgM+ or PRNT+) and 13.7% (N = 54) had indeterminate results. A fetal malformation was identified in 29 children (9.3%). Fetal malformation was associated with a ZIKV high risk serological profile [24 out of the 246 (1.6%) with low risk profile and 3 out of the 12 with at high risk profile (25.0%; p = .02)]. Four newborns with high risk profile had a positive ZIKV-PCR test, which included two cases with microcephaly. No association was observed between maternal exposure to ZIKV infection and developmental abnormalities during the post-natal period follow-up.

CONCLUSIONS

The ZIKV-screening program had considerable costs and yielded a high rate of indeterminate results among asymptomatic pregnant women. Considering the poor value for decision-making of the results, efforts should focus on providing early access to routine maternity care, especially to migrant women. A simpler screening protocol might consider an initial ZIKV-PCR or IgM determination and subsequent referral to a fetal medicine specialist in those women with a positive result and/or whom ultrasound examination has revealed fetal abnormalities (10% of total women in our study sample).

Immunoglobulin M seroneutralization for improved confirmation of Japanese encephalitis virus infection in a flavivirus-endemic area

BACKGROUND

The mainstay of diagnostic confirmation of acute Japanese encephalitis (JE) involves detection of anti-JE virus (JEV) immunoglobulin M (IgM) by enzyme-linked immunosorbent assay (ELISA). Limitations in the specificity of this test are increasingly apparent with the introduction of JEV vaccinations and the endemicity of other cross-reactive flaviviruses. Virus neutralization testing (VNT) is considered the gold standard, but it is challenging to implement and interpret. We performed a pilot study to assess IgG depletion prior to VNT for detection of anti-JEV IgM neutralizing antibodies (IgM-VNT) as compared with standard VNT.

METHODS

We evaluated IgM-VNT in paired sera from anti-JEV IgM ELISA-positive patients (JE n=35) and negative controls of healthy flavivirus-naïve (n=10) as well as confirmed dengue (n=12) and Zika virus (n=4) patient sera. IgM-VNT was subsequently performed on single sera from additional JE patients (n=76).

RESULTS

Anti-JEV IgG was detectable in admission serum of 58% of JE patients. The positive, negative and overall percentage agreement of IgM-VNT as compared with standard VNT was 100%. A total of 12/14 (86%) patient samples were unclassified by VNT and, with sufficient sample available for IgG depletion and IgG ELISA confirming depletion, were classified by IgM-VNT. IgM-VNT enabled JE case classification in 72/76 (95%) patients for whom only a single sample was available.

CONCLUSIONS

The novel approach has been readily adapted for high-throughput testing of single patient samples and it holds promise for incorporation into algorithms for use in reference centres.

Acute micro-outbreak of Chagas disease in the southeastern Amazon: a report of five cases

Background:

Chagas disease is gaining importance in the Brazilian Amazon region as a differential diagnosis of febrile syndrome. The most recent microoutbreak occurred in Ipixuna, in Amazonas state.

Methods:

An epidemiological survey was conducted using parasitological and serological tests, and electrocardiographic analysis.

Results:

The patients belonged to one family and had ingested açaí acquired from Ipixuna. All patients reported fever and initially a thick blood smear test was done to identify Trypanosoma cruzi. Benznidazole treatment was administered to all patients.

Conclusions:

Knowledge of the epidemiological dynamics of Chagas disease allows us to improve control and management measures for this disease.

Sero-Prevalence of West Nile Virus in Urban and Peri-Urban Poultry Farms of Guwahati, India

West Nile virus (WNV) is a zoonotic, emerging mosquito-borne virus which can cause severe disease in the form of encephalitis and acute flaccid paralysis in humans. In Assam, northeast India, arboviruses seem to be re-emerging, however, WNV has been little studied. The present investigation was carried out from April, 2018 to March, 2019 to study sero-positivity of WNV in chicken in urban and peri-urban areas of Guwahati, the capital city of Assam. Four urban and four peri-urban areas of Guwahati were selected. A total of 864 chicken serum samples (72 samples per month) were screened by ELISA and further confirmed by haemagglutination inhibition (HI), which revealed that 3.13% of the chickens had been exposed to WNV, with 0.69% sero-positivity in urban areas compared to 5.56% in peri-urban. Peak sero-prevalence of WNV were reported during the month of July and August with 8.33% each with lowest sero-prevalence being recorded in November (1.39%) and no sero-positive birds from December to April. These results indicate that WNV is one of the actively circulating flaviviruses in Assam, and human febrile and encephalitic cases should be screened for the disease.

Selected Biomarkers of Tick-Borne Encephalitis: A Review

Tick-borne encephalitis (TBE) is an acute disease caused by the tick-borne encephalitis virus. Due to the viral nature of the condition, there is no effective causal treatment for full-blown disease. Current and nonspecific TBE treatments only relieve symptoms. Unfortunately, the first phase of TBE is characterized by flu-like symptoms, making diagnosis difficult during this period. The second phase is referred to as the neurological phase as it involves structures in the central nervous system-most commonly the meninges and, in more severe cases, the brain and the spinal cord. Therefore, it is important that early markers of TBE that will guide clinical decision-making and the choice of treatment are established. In this review, we performed an extensive search of literature reports relevant to biomarkers associated with TBE using the MEDLINE/PubMed database. We observed that apart from routinely determined specific immunoglobulins, free light chains may also be useful in the evaluation of intrathecal synthesis in the central nervous system (CNS) during TBEV infection. Moreover, selected metalloproteinases, chemokines, or cytokines appear to play an important role in the pathogenesis of TBE as a consequence of inflammatory reactions and recruitment of white blood cells into the CNS. Furthermore, we reported promising findings on tau protein or Toll-like receptors. It was also observed that some people may be predisposed to TBE. Therefore, to understand the role of selected tick-borne encephalitis biomarkers, we categorized these factors and discussed their potential application in the diagnosis, prognosis, monitoring, or management of TBE.

Determining seropositivity-A review of approaches to define population seroprevalence when using multiplex bead assays to assess burden of tropical diseases

Background

Serological surveys with multiplex bead assays can be used to assess seroprevalence to multiple pathogens simultaneously. However, multiple methods have been used to generate cut-off values for seropositivity and these may lead to inconsistent interpretation of results. A literature review was conducted to describe the methods used to determine cut-off values for data generated by multiplex bead assays.

Methodology/Principal findings

A search was conducted in PubMed that included articles published from January 2010 to January 2020, and 308 relevant articles were identified that included the terms “serology”, “cut-offs”, and “multiplex bead assays”. After application of exclusion of articles not relevant to neglected tropical diseases (NTD), vaccine preventable diseases (VPD), or malaria, 55 articles were examined based on their relevance to NTD or VPD. The most frequently applied approaches to determine seropositivity included the use of presumed unexposed populations, mixture models, receiver operating curves (ROC), and international standards. Other methods included the use of quantiles, pre-exposed endemic cohorts, and visual inflection points.

Conclusions/Significance

For disease control programmes, seropositivity is a practical and easily interpretable health metric but determining appropriate cut-offs for positivity can be challenging. Considerations for optimal cut-off approaches should include factors such as methods recommended by previous research, transmission dynamics, and the immunological backgrounds of the population. In the absence of international standards for estimating seropositivity in a population, the use of consistent methods that align with individual disease epidemiological data will improve comparability between settings and enable the assessment of changes over time.

Serological surveys can provide information regarding population-level disease exposure by assessing immune responses created during infection. Multiplex bead assays (MBAs) allow for an integrated serological platform to monitor antibody responses to multiple pathogens concurrently. As programs adopt integrated disease control strategies, MBAs are especially advantageous since many of these diseases may be present in the same population and antibodies against all pathogens of interest can be detected simultaneously from a single blood sample. Interpreting serological data in a programmatic context typically involves classifying individuals as seronegative or seropositive using a ‘cut-off’, whereby anyone with a response above the defined threshold is considered to be seropositive. Although studies increasingly test blood samples with MBAs, published studies have applied different methods of determining seropositivity cut-offs, making results difficult to compare across settings and over time. The lack of harmonized methods for defining seropositivity is due to the absence of international standards, pathogen biology, or assay-specific methods that may impact resulting data. This review highlights the need for a standardized approach for which cut-off methods to use per pathogen when applied to integrated disease surveillance using platforms such as MBAs.

Diagnostic Potential of a Luminex-Based Coronavirus Disease 2019 Suspension Immunoassay (COVID-19 SIA) for the Detection of Antibodies against SARS-CoV-2

Due to the current, rapidly increasing Coronavirus disease 2019 (COVID-19) pandemic, efficient and highly specific diagnostic methods are needed. The receptor-binding part of the spike (S) protein, S1, has been suggested to be highly virus-specific; it does not cross-react with antibodies against other coronaviruses. Three recombinant partial S proteins of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) expressed in mammalian or baculovirus-insect cells were evaluated as antigens in a Luminex-based suspension immunoassay (SIA). The best performing antigen (S1; amino acids 16-685) was selected and further evaluated by serum samples from 76 Swedish patients or convalescents with COVID-19 (previously PCR and/or serologically confirmed), 200 pre-COVID-19 individuals (180 blood donors and 20 infants), and 10 patients with acute Epstein-Barr virus infection. All 76 positive samples showed detectable antibodies to S1, while none of the 210 negative controls gave a false positive antibody reaction. We further compared the COVID-19 SIA with a commercially available enzyme immunoassay and a previously evaluated COVID-19 rapid antibody test. The results revealed an overall assay sensitivity of 100%, a specificity of 100% for both IgM and IgG, a quantitative ability at concentrations up to 25 BAU/mL, and a better performance as compared to the commercial assays, suggesting the COVID-19 SIA as a most valuable tool for efficient laboratory-based serology.

A need to raise the bar - A systematic review of temporal trends in diagnostics for Japanese encephalitis virus infection, and perspectives for future research

•

Japanese encephalitis virus (JEV) remains a leading cause of neurological infection in Asia.

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A systematic review identified 20,212 published human cases of laboratory-confirmed JEV infections from 205 studies.

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15,167 (75%) of cases were confirmed with the lowest confidence diagnostic test, i.e., level 3 or 4, or level 4.

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Only 109 (53%) of the studies reported contemporaneous testing for dengue-specific antibodies.

•

A fundamental pre-requisite for the control of JE is lacking — that of a simple and specific diagnostic procedure that can be adapted for point-of-care tests and readily used throughout JE endemic regions of the world.

Objective

Japanese encephalitis virus infection (JE) remains a leading cause of neurological disease in Asia, mainly involving individuals living in remote areas with limited access to treatment centers and diagnostic facilities. Laboratory confirmation is fundamental for the justification and implementation of vaccination programs. We reviewed the literature on historical developments and current diagnostic capability worldwide, to identify knowledge gaps and instill urgency to address them.

Methods

Searches were performed in Web of Science and PubMed using the term 'Japanese encephalitis' up to 13th October 2019. Studies reporting laboratory-confirmed symptomatic JE cases in humans were included, and data on details of diagnostic tests were extracted. A JE case was classified according to confirmatory levels (Fischer et al., 2008; Campbell et al., 2011; Pearce et al., 2018; Heffelfinger et al., 2017), where level 1 represented the highest level of confidence.

Findings

20,212 published JE cases were identified from 205 studies. 15,167 (75%) of these positive cases were confirmed with the lowest-confidence diagnostic tests (level 3 or 4, or level 4). Only 109 (53%) of the studies reported contemporaneous testing for dengue-specific antibodies.

Conclusion

A fundamental pre-requisite for the control of JEV is lacking — that of a simple and specific diagnostic procedure that can be adapted for point-of-care tests and readily used throughout JE-endemic regions of the world.

Emerging infectious disease laboratory and diagnostic preparedness to accelerate vaccine development

Rapid vaccine development in response to an outbreak of a new emerging infectious disease (EID) is a goal targeted by public health agencies worldwide. This goal becomes more complicated when there are no standardized sets of viral and immunological assays, no accepted and well-characterized samples, standards or reagents, and no approved diagnostic tests for the EID pathogen. The diagnosis of infections is of critical importance to public health, but also in vaccine development in order to track incident infections during clinical trials, to differentiate natural infection responses from those that are vaccine-related and, if called for by study design, to exclude subjects with prior exposure from vaccine efficacy trials. Here we review emerging infectious disease biological standards development, vaccine clinical assay development and trial execution with the recent experiences of MERS-CoV and Zika virus as examples. There is great need to establish, in advance, the standardized reagents, sample panels, controls, and assays to support the rapid advancement of vaccine development efforts in response to EID outbreaks.

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.

Distinction between serological responses following tick-borne encephalitis virus (TBEV) infection vs vaccination, Sweden 2017

Tick-borne encephalitis virus (TBEV) is an important European vaccine-preventable pathogen. Discrimination of vaccine-induced antibodies from those elicited by infection is important. We studied anti-TBEV IgM/IgG responses, including avidity and neutralisation, by multiplex serology in 50 TBEV patients and 50 TBEV vaccinees. Infection induced antibodies reactive to both whole virus (WV) and non-structural protein 1 (NS1) in 48 clinical cases, whereas 47 TBEV vaccinees had WV, but not NS1 antibodies, enabling efficient discrimination of infection/vaccination.

Antibody responses to Zika virus proteins in pregnant and non-pregnant macaques

The specificity of the antibody response against Zika virus (ZIKV) is not well-characterized. This is due, in part, to the antigenic similarity between ZIKV and closely related dengue virus (DENV) serotypes. Since these and other similar viruses co-circulate, are spread by the same mosquito species, and can cause similar acute clinical syndromes, it is difficult to disentangle ZIKV-specific antibody responses from responses to closely-related arboviruses in humans. Here we use high-density peptide microarrays to profile anti-ZIKV antibody reactivity in pregnant and non-pregnant macaque monkeys with known exposure histories and compare these results to reactivity following DENV infection. We also compare cross-reactive binding of ZIKV-immune sera to the full proteomes of 28 arboviruses. We independently confirm a purported ZIKV-specific IgG antibody response targeting ZIKV nonstructural protein 2B (NS2B) that was recently reported in ZIKV-infected people and we show that antibody reactivity in pregnant animals can be detected as late as 127 days post-infection (dpi). However, we also show that these responses wane over time, sometimes rapidly, and in one case the response was elicited following DENV infection in a previously ZIKV-exposed animal. These results suggest epidemiologic studies assessing seroprevalence of ZIKV immunity using linear epitope-based strategies will remain challenging to interpret due to susceptibility to false positive results. However, the method used here demonstrates the potential for rapid profiling of proteome-wide antibody responses to a myriad of neglected diseases simultaneously and may be especially useful for distinguishing antibody reactivity among closely related pathogens.

Detection of Specific ZIKV IgM in Travelers Using a Multiplexed Flavivirus Microsphere Immunoassay

Zika virus (ZIKV) has spread widely in the Pacific and recently throughout the Americas. Unless detected by RT-PCR, confirming an acute ZIKV infection can be challenging. We developed and validated a multiplexed flavivirus immunoglobulin M (IgM) microsphere immunoassay (flaviMIA) which can differentiate ZIKV-specific IgM from that due to other flavivirus infections in humans. The flaviMIA bound 12 inactivated flavivirus antigens, including those from ZIKV and yellow fever virus (YFV), to distinct anti-flavivirus antibody coupled beads. These beads were used to interrogate sera from patients with suspected ZIKV infection following travel to relevant countries. FlaviMIA results were validated by comparison to the ZIKV plaque reduction neutralization test (PRNT). The results highlight the complexity of serological ZIKV diagnosis, particularly in patients previously exposed to, or vaccinated against, other flaviviruses. We confirmed 99 patients with ZIKV infection by a combination of RT-PCR and serology. Importantly, ZIKV antibodies could be discriminated from those ascribed to other flavivirus infections. Serological results were sometimes confounded by the presence of pre-existing antibodies attributed to previous flavivirus infection or vaccination. Where RT-PCR results were negative, testing of appropriately timed paired sera was necessary to demonstrate seroconversion or differentiation of recent from past infection with or exposure to ZIKV.