Preliminary multiplex microarray IgG immunoassay for the diagnosis of toxoplasmosis and rubella

Congenital Toxoplasmosis Diagnosis: Current Approaches and New Insights

PURPOSE

The aim of this study is to describe and discuss current disadvantages in congenital toxoplasmosis (CT) diagnosis, and what can be improved or changed through new perspectives and technological advances.

METHODS

We used Pubmed, Cochrane, and EBSCO databases to research publications from 10 years to date describing current diagnostic methods for CT. The keywords used for this Mini-Review were Toxoplasma gondii, congenital toxoplasmosis, diagnosis, and prospects using Boolean operators such as AND, OR, identifying scientific publications highlighting the importance of implementing new diagnostic methods.

RESULTS

Current diagnosis methods have several disadvantages, i.e., time-consuming, low sensitivity or specificity, and non-cost effective, that bring up the necessity of improving or developing new approaches. Recombinant proteins can help improve specificity by generating tests that use circulating strains in a specific geographical region, SAG1 and BAG1, as they are expressed during a particular stage of the disease (acute or chronic, respectively), for its use in serological diagnoses, such as capture ELISA and immunochromatography. Point of Care (POC) tests are methods performed at the patient care site, which leads to rapid patient treatment; despite the advantages, several improvements and perspectives are necessary to be implemented globally.

CONCLUSIONS

Although already established diagnosis methods for CT may be sufficient in some regions, there is still a persistent demand to develop tests with higher throughput, cost, and time reduction in developing countries, where prevalence is high. New approaches in CT diagnosis, such as recombinant proteins, capture ELISA, immunochromatography, and POC tests methods, can increase performance in terms of specificity and sensitivity simplifying diagnostic tests' requirements.

Rational design and evaluation of the recombinant multiepitope protein for serodiagnosis of rubella

BACKGROUND

Rubella is an infection caused by rubella virus (RV) and is generally regarded as a mild childhood disease. The disease continues to be of public health importance mainly because when the infection is acquired during early pregnancy it often results in fetal abnormalities, which are classified as congenital rubella syndrome (CRS). An accurate diagnosis for rubella is thus of pivotal importance for proper treatment.

OBJECTIVE

To produce a recombinant multiepitope protein (rMERUB) for the diagnosis of rubella, based on conserved immunodominant epitopes of glycoprotein E1 and E2.

METHODS

A synthetic gene was designed and cloned into vector pET21a with a 6xHis tag at the C-terminal for affinity purification and overexpressed in Escherichia coli cells. Biophysical analysis of rMERUB was performed by circular dichroism. Biological activity was assessed using an in-house ELISA assay.

RESULTS

Expression in Escherichia coli showed a ~22 kDa protein that was purified and used to perform structural assays and an IgG ELISA. Structural analyses reveal rMERUB has a β leaf pattern that promotes the exposure of epitopes, thus allowing antibody recognition. Evaluation of 33 samples (22=positive; 11=negative) was performed using in-house ELISA and this was compared with a commercial kit. The sensitivity was 100% (95% CI: 85-100) and specificity 90.91% (95% CI: 62-99). Excellent agreement (Kappa index = 0.9) was obtained between ELISA assays.

CONCLUSIONS

The careful choice of epitopes and the high epitope density, coupled with simple-step purification, pinpoints rMERUB as a promising alternative for rubella diagnosis, with potential for the development of a diagnostic kit.

Performance of Zika Assays in the Context of Toxoplasma gondii, Parvovirus B19, Rubella Virus, and Cytomegalovirus (TORCH) Diagnostic Assays

Infections during pregnancy that may cause congenital abnormalities have been recognized for decades, but their diagnosis is challenging. This was again illustrated with the emergence of Zika virus (ZIKV), highlighting the inherent difficulties in estimating the extent of pre- and postnatal ZIKV complications because of the difficulties in establishing definitive diagnoses. We reviewed the epidemiology, infection kinetics, and diagnostic methods used for Toxoplasma gondii, parvovirus B19, rubella virus, and cytomegalovirus (TORCH) infections and compared the results with current knowledge of ZIKV diagnostic assays to provide a basis for the inclusion of ZIKV in the TORCH complex evaluations. Similarities between TORCH pathogens and ZIKV support inclusion of ZIKV as an emerging TORCH infection. Our review evaluates the diagnostic performance of various TORCH diagnostic assays for maternal screening, fetal screening, and neonatal screening. We show that the sensitivity, specificity, and positive and negative predictive value of TORCH complex pathogens are widely variable, stressing the importance of confirmatory testing and the need for novel techniques for earlier and accurate diagnosis of maternal and congenital infections. In this context it is also important to acknowledge different needs and access to care for different geographic and resource settings.

Field Test and Validation of the Multiplier Measles, Mumps, Rubella, and Varicella-Zoster Multiplexed Assay System in the Democratic Republic of the Congo by Using Dried Blood Spots

Here we describe baseline validation studies and field performance of a research-use-only chemiluminescent multiplex serology panel for measles, mumps, rubella, and varicella-zoster virus used with dried blood spots in support of the 2013-2014 Democratic Republic of the Congo Demographic and Health Survey. Characterization of the panel using U.S. FDA-cleared commercial kits shows good concordance for measles, mumps, rubella, and varicella-zoster with average sensitivity across assays of 94.9% and an average specificity of 91.4%. As expected, performance versus available standards validated for plaque-reduction assays does not provide a 1:1 correspondence with international units and yet demonstrates excellent linearity (average Hill's slope = 1.02) and ∼4 logs of dynamic range. In addition, for the four assays, the multiplexed format allowed for inclusion of three positive and two negative controls for each sample. A prototype Dynex Multiplier chemiluminescent automated immunoassay instrument with a charge-coupled device camera provided a rugged and robust processing and data acquisition platform. Performance of a multiplex instrument for serological testing in a substantially resource-limited environment shows excellent reproducibility, minimal cross-reactivity, and a clear discrimination between specific assays and should be considered a viable option for future serosurveys.IMPORTANCE The critical evaluation of immunization programs is key to identifying areas of suboptimal vaccination coverage, monitoring activities, and aiding development of public health policy. For evaluation of vaccine effectiveness, direct antibody binding assay methods, including enzyme immunoassay, enzyme-linked fluorescence assays, and indirect immunofluorescence assay, are most commonly used for detection of IgG antibodies. However, despite their well-demonstrated, reliable performance, they can be labor-intensive and time-consuming and require separate assays for each individual marker. This necessitates increased sample volumes, processing time, and personnel, which may limit assessment to a few key targets in resource-limited settings, that is, low- and middle-income locations where funding for public health or general infrastructure that directly impacts public health is restricted, limiting access to equipment, infrastructure, and trained personnel. One solution is a multiplexed immunoassay, which allows for the detection of multiple analytes in a single reaction for increased efficiency and rapid surveillance of infectious diseases in limited-resource settings. Thus, the scope of the project precluded a full validation, and here we present abbreviated validation studies demonstrating adequate sensitivity, specificity, and reproducibility.

Validation of monoplex assays detecting antibodies against Corynebacterium diphtheriae and Clostridium tetani toxins, rubella virus and parvovirus B19 for incorporation into Multiplex Serology

Serological assays detecting antibodies in serum or plasma samples are useful and versatile instruments to investigate an individual's infection and vaccination history, e.g. for clinical diagnosis, personal risk evaluation, and seroepidemiological studies. Multiplex Serology is a suspension bead array-based high-throughput methodology for simultaneous measurement of antibodies against multiple pathogens in a single reaction vessel, thus economizing sample volume, measurement time, and costs. We developed and validated bead-based pathogen-specific Monoplex Serology assays, i.e. assays including only antigens for the respective pathogen, to detect antibodies against Corynebacterium diphtheriae and Clostridium tetani toxins, rubella virus and parvovirus B19. The developed assays expand the portfolio of existing pathogen-specific bead-based serology assays and can be efficiently incorporated into larger Multiplex Serology panels. The newly developed Monoplex Serology assays consist of only one antigen per infectious agent, expressed as Glutathione S-transferase-fusion proteins in E. coli. Specificity, sensitivity and Cohen's kappa statistics in comparison with routine clinical diagnostic assays were calculated for serum dilutions 1:100 and 1:1000. All pathogen-specific assays were successfully validated at both serum dilutions with the exception of rubella Monoplex Serology which showed impaired sensitivity (57.6%) at dilution 1:1000. Specificities of successfully validated Monoplex Serology assays ranged from 85.6% to 100.0% (median: 91.7%), and sensitivities from 81.3% to 95.8% (median: 90.9%); agreement with the reference assays ranged from substantial to almost perfect (kappa: 0.66-0.86, median: 0.78). Statistical performance and slim assay design enable efficient incorporation of the developed assays into Multiplex Serology.