Serotyping, a challenging approach for Toxoplasma gondii typing

Genotype analysis has revealed a high genetic diversity in strains of Toxoplasma gondii, isolated from a wide range of intermediate hosts and different geographic origins. Diversity is notably striking for parasites from wild hosts in South America, generally referred as non-archetypal genotypes. Those genotypes are implicated in the etiology of severe clinical disease, multivisceral toxoplasmosis, associated with high rate of mortality in immunocompetent individuals. Can we accept specific antibodies produced during T. gondii infection as biomarkers to identify infecting genotypes? Scientific evidence supports a positive response to this question; however, the genetic diversity of T. gondii genotypes organized into 16 haplogroups and collectively defined in 6 major clades, provides a reminder of the complexity and difficulty for the purpose. This review discusses serological approaches to genotyping T. gondii.

Development and application of a novel triplex protein microarray method for rapid detection of antibodies against avian influenza virus, Newcastle disease virus, and avian infectious bronchitis virus

Avian influenza virus (AIV), Newcastle disease virus (NDV), and avian infectious bronchitis virus (IBV) inflict immense damage on the global poultry industry annually. Serological diagnostic methods are fundamental for the effective control and prevention of outbreaks caused by these viruses. In this study, a novel triplex protein microarray assay was developed and validated for the rapid and simultaneous visualized detection of antibodies against AIV, NDV, and IBV in chicken sera. The AIV nuclear protein (NP), NDV phosphoprotein (P), and IBV nonstructural protein 5 (nsp5) were produced in a prokaryotic expression system, purified, and immobilized onto an initiator integrated poly(dimethylsiloxane) (iPDMS) film as probes to detect antibodies against these viruses in chicken sera. After optimization of the reaction conditions, no cross-reactivity was detected with infectious bursal disease virus, avian leukosis virus subgroup J and chicken anemia virus antisera. The lowest detectable antibody titers in this assay corresponded to hemagglutination inhibition (HI) titers of 2⁴ and 2¹ for AIV and NDV, respectively, and to an IDEXX antibody titer of 10³ for IBV, using the HI assay and IDEXX commercial ELISA kit as the reference methods. When156 serum samples were tested using the new assay, the HI test and the IBV IDEXX ELISA kit, the assay showed 96.8% (151/156), 97.4% (152/156) and 99.4% (155/156) diagnostic accuracy for detection of AIV, NDV and IBV antibody, respectively. The current study suggests that the newly developed triplex microarray is rapid, sensitive, and specific, providing a viable alternative assay for AIV, NDV, and IBV antibody screening in epidemiological investigations and vaccination evaluations.

Lateral Flow Serodiagnosis in the Double-Antigen Sandwich Format: Theoretical Consideration and Confirmation of Advantages

Determination of the presence in the blood of antibodies specific to the causative agent of a particular disease (serodiagnosis) is an effective approach in medical analytical chemistry. Serodiagnostics performed in the lateral flow immunoassay format (immunochromatography) meet the modern requirements for point-of-care testing and are supported by existing technologies of large-scale diagnostic tests production, thus increasing the amount of attention in a tense epidemiological situation. For traditional lateral flow serodiagnostics formats, a large number of nonspecific immunoglobulins in the sample significantly reduces the degree of detectable binding. To overcome these limitations, an assay based on the formation of immobilized antigen-specific antibody-labeled antigen complexes detection was proposed. However, the requirements for its implementation, providing maximum sensitivity, have not been established. This article describes the mathematical model for the above assay. The influence of the ratio of reagent concentrations on the analysis results is considered. It is noted that the formation of specific antibody complexes with several labeled antigens is the main limiting factor in reducing the detection limit, and methods are proposed to minimize this factor. Recommendations for the choice of the assay conditions, following from the analysis of the model, are confirmed experimentally.

Serological Array-in-Well Multiplex Assay Reveals a High Rate of Respiratory Virus Infections and Reinfections in Young Children

The multiplex immunoassay was successfully used to simultaneously detect antibodies against seven different viruses. The developed serological microarray is a new promising tool for diagnostic, epidemiological, and seroprevalence analyses of virus infections.

Serological assays are used to diagnose and characterize host immune responses against microbial pathogens. Microarray technologies facilitate high-throughput immunoassays of antibody detection against multiple pathogens simultaneously. To improve survey of influenza A virus (IAV), influenza B virus (IBV), respiratory syncytial virus (RSV), and adenovirus (AdV) antibody levels, we developed a microarray consisting of IAV H1N1, IAV H1N1pdm09 (vaccine), IAV H3N2, IBV Victoria, IBV Yamagata, RSV, AdV type 5 hexon protein, and control antigens printed on the bottom of a microtiter plate well. Bound IgG antibodies were detected with anti-human IgG-coated photon-upconverting nanoparticles and measured with a photoluminescence imager. The performance of the microarray immunoassay (MAIA) was evaluated with serum samples (n = 576) collected from children (n = 288) at 1 and 2 years of age and tested by standard enzyme immunoassays (EIAs) for antibodies to IAV vaccine and RSV. EIAs and MAIA showed substantial to almost perfect agreement (Cohen’s κ, 0.62 to 0.83). Applying MAIA, we found seroprevalences of 55% for IAV H1N1, 54% for IAV vaccine, 30% for IAV H3N2, 24% for IBV Victoria, 25% for IBV Yamagata, 38% for RSV, and 26% for AdV in 1-year-old children (n = 768). By the age of 2 years, IgG seropositivity rates (n = 714) increased to 74% for IAV H1N1, 71% for IAV vaccine, 49% for IAV H3N2, 47% for IBV Yamagata, 49% for IBV Victoria, 68% for RSV, and 58% for AdV. By analyzing increases in antibody levels not biased by vaccinations, we found a reinfection rate of 40% for RSV and 31% for AdV in children between 1 and 2 years of age.

IMPORTANCE The multiplex immunoassay was successfully used to simultaneously detect antibodies against seven different viruses. The developed serological microarray is a new promising tool for diagnostic, epidemiological, and seroprevalence analyses of virus infections.

Novel protein chip for the detection of antibodies against infectious bronchitis virus

BACKGROUND

Infectious bronchitis (IB) caused by the IB virus (IBV) can cause acute damage to chickens around the world. Therefore, rapid diagnosis and immune status determination are critical for controlling IBV outbreaks. Enzyme-linked immunosorbent assays (ELISAs) have been widely used in the detection of IBV antibodies in the early infection and continuous infection of IB because they are more sensitive and quicker than other diagnostic methods.

RESULTS

We have developed two indirect microarray methods to detect antibodies against IBV: a chemiluminescent immunoassay test (CIT) and a rapid diagnostic test (RDT). IBV nonstructural protein 5 (nsp5) was expressed, purified from Escherichia coli, and used to spot the initiator integrated poly(dimethylsiloxane), which can provide a near "zero" background for serological assays. Compared with the IDEXX IBV Ab Test kit, CIT and RDT have a sensitivity and specificity of at least 98.88% and 91.67%, respectively. No cross-reaction was detected with antibodies against avian influenza virus subtypes (H5, H7, and H9), Newcastle disease virus, Marek's disease virus, infectious bursal disease virus, and chicken anemia virus. The coefficients of variation of the reproducibility of the intra- and inter-assays for CIT ranged from 0.8 to 18.63%. The reproducibility of RDT was consistent with the original results. The application of the IBV nsp5 protein microarray showed that the positive rate of the CIT was 96.77%, that of the nsp5 ELISA was 91.40%, and that of the RDT was 90.32%. Furthermore, the RDT, which was visible to the naked eye, could be completed within 15 min. Our results indicated that compared with nsp5 ELISA, the CIT was more sensitive, and the RDT had similar positive rates but was faster. Furthermore, the two proposed methods were specific and stable.

CONCLUSIONS

Two microarray assays, which were rapid, specific, sensitive, and relatively simple, were developed for the detection of an antibody against IBV. These methods can be of great value for the surveillance of pathogens and monitoring the efficiency of vaccination.

Multiplex immunoassay for detection of immunoglobulin G to herpes simplex virus types 1, 2 and cytomegalovirus based on PHOSPHAN technology

We have developed a multiplex immunoassay test (immunochip) based on PHOSPHAN technology for the detection of immunoglobulin G to herpes simplex virus (HSV) types 1, 2 and cytomegalovirus (CMV). The immunochip consists of HSV type specific gG1 (HSV-1) and gG2 (HSV-2) recombinant antigens, the lysate antigen for detection of total IgG to both HSV types (HSV 1/2), and CMV specific chimeric recombinant antigen containing the immunodominant sequences of pp150, gB, pp28 and pp52 proteins. The sensitivity and specificity of simultaneous IgGs detection with recombinant proteins were comparable to the commercial ELISA kits regardless of the kind of investigated serum specimens (patient sera, standard serum panels). The lysate HSV antigen was as sensitive but significantly less specific, so that it could not be recommended for use as a component of the multiplex test. These results can be used as a basis for creating commercial multiplex tests intended for high-productive screening of HSV, CMV and other TORCH-infections in a clinical laboratory.

Array-in-well platform-based multiplex assay for the simultaneous detection of anti-HIV- and treponemal-antibodies, and Hepatitis B surface antigen

Multiplex assays detecting sets of related clinical analytes simultaneously can save considerable amount of time and resources. Array-in-well (AIW) is a powerful platform for the multiplex detection of different analytes where microarrays can be printed at the bottom of microtiter wells, thus combining the potential of microarrays with the ease of handling microtiter wells. We have developed a single-step AIW assay for the simultaneous screening of HIV, Treponema pallidum subspecies pallidum (causing syphilis) and Hepatitis B virus infections targeting the specific detection of anti-HIV- and treponemal-antibodies and Hepatitis B surface antigen (HBsAg), respectively, using two different fluorescent label technologies i.e. DyLight 633 and europium nanoparticle. Double-antigen assay formats were used for anti-HIV- and treponemal-antibody detection that can simultaneously detect both IgG and IgM, and thus reduce the window period of detection. AIW assay was evaluated with well characterized serum/plasma samples (n=111), and the qualitative results were in near complete agreement with those of the reference assays. The AIW assay exhibited 100% sensitivities for all three analytes, and 100% specificities for anti-HIV antibodies and HBsAg, and 98.6% specificity for treponemal antibodies. The limit of detection of HBsAg in AIW assay was 0.18 ng/ml. This high performing AIW assay has the potential to be used as a multiplex screening test for these three infections.

An integrated lab-on-chip for rapid identification and simultaneous differentiation of tropical pathogens

Tropical pathogens often cause febrile illnesses in humans and are responsible for considerable morbidity and mortality. The similarities in clinical symptoms provoked by these pathogens make diagnosis difficult. Thus, early, rapid and accurate diagnosis will be crucial in patient management and in the control of these diseases. In this study, a microfluidic lab-on-chip integrating multiplex molecular amplification and DNA microarray hybridization was developed for simultaneous detection and species differentiation of 26 globally important tropical pathogens. The analytical performance of the lab-on-chip for each pathogen ranged from 10² to 10³ DNA or RNA copies. Assay performance was further verified with human whole blood spiked with Plasmodium falciparum and Chikungunya virus that yielded a range of detection from 200 to 4×10⁵ parasites, and from 250 to 4×10⁷ PFU respectively. This lab-on-chip was subsequently assessed and evaluated using 170 retrospective patient specimens in Singapore and Thailand. The lab-on-chip had a detection sensitivity of 83.1% and a specificity of 100% for P. falciparum; a sensitivity of 91.3% and a specificity of 99.3% for P. vivax; a positive 90.0% agreement and a specificity of 100% for Chikungunya virus; and a positive 85.0% agreement and a specificity of 100% for Dengue virus serotype 3 with reference methods conducted on the samples. Results suggested the practicality of an amplification microarray-based approach in a field setting for high-throughput detection and identification of tropical pathogens.

Tropical diseases consist of a group of debilitating and fatal infections that occur primarily in rural and urban settings of tropical and subtropical countries. While the primary indices of an infection are mostly the presentation of clinical signs and symptoms, outcomes due to an infection with tropical pathogens are often unspecific. Accurate diagnosis is crucial for timely intervention, appropriate and adequate treatments, and patient management to prevent development of sequelae and transmission. Although, multiplex assays are available for the simultaneous detection of tropical pathogens, they are generally of low throughput. Performing parallel assays to cover the detection for a comprehensive scope of tropical infections that include protozoan, bacterial and viral infections is undoubtedly labor-intensive and time consuming. We present an integrated lab-on-chip using microfluidics technology coupled with reverse transcription (RT), PCR amplification, and microarray hybridization for the simultaneous identification and differentiation of 26 tropical pathogens that cause 14 globally important tropical diseases. Such diagnostics capacity would facilitate evidence-based management of patients, improve the specificity of treatment and, in some cases, even allow contact tracing and other disease-control measures.

Point-of-care vertical flow allergen microarray assay: proof of concept

BACKGROUND

Sophisticated equipment, lengthy protocols, and skilled operators are required to perform protein microarray-based affinity assays. Consequently, novel tools are needed to bring biomarkers and biomarker panels into clinical use in different settings. Here, we describe a novel paper-based vertical flow microarray (VFM) system with a multiplexing capacity of at least 1480 microspot binding sites, colorimetric readout, high sensitivity, and assay time of <10 min before imaging and data analysis.

METHOD

Affinity binders were deposited on nitrocellulose membranes by conventional microarray printing. Buffers and reagents were applied vertically by use of a flow controlled syringe pump. As a clinical model system, we analyzed 31 precharacterized human serum samples using the array system with 10 allergen components to detect specific IgE reactivities. We detected bound analytes using gold nanoparticle conjugates with assay time of ≤10 min. Microarray images were captured by a consumer-grade flatbed scanner.

RESULTS

A sensitivity of 1 ng/mL was demonstrated with the VFM assay with colorimetric readout. The reproducibility (CV) of the system was <14%. The observed concordance with a clinical assay, ImmunoCAP, was R(2) = 0.89 (n = 31).

CONCLUSIONS

In this proof-of-concept study, we demonstrated that the VFM assay, which combines features from protein microarrays and paper-based colorimetric systems, could offer an interesting alternative for future highly multiplexed affinity point-of-care testing.

Microarray of surface-exposed proteins of Rickettsia heilongjiangensis for serodiagnosis of Far-eastern spotted fever

Background

Far-eastern spotted fever (FESF) is an important emerging infectious disease in Northeast Asia. The laboratory diagnosis of FESF in hospitals is mainly based on serological methods. However, these methods need to cultivate rickettsial cells as diagnostic antigens, which is both burdensome and dangerous.

Methods

Eleven surface-exposed proteins (SEPs) were identified in our previous study and their recombinant proteins (rSEPs) fabricated on a microarray were serologically analyzed with seventeen paired sera from patients suffered from FESF in this study.

Results

All the rSEPs showed sensitivities of between 53% and 82% to acute-phase sera and of between 65% and 82% to convalescent-phase sera, and all the rSEPs except rRplA showed specificities of between 80% and 95%. The combination assay of two, three, or four of the four rSEPs (rOmpA-2, rOmpB-3, rRpsB, and rSdhB) showed better sensitivities of between 76% and 94% to the acute-phase sera or between 82% and 100% to the convalescent-phase sera and acceptable specificities of between 75% and 90%.

Conclusions

Our results suggest that the four rSEPs are more likely candidate antigens for serological diagnosis of FESF.

Microbial glycan microarrays define key features of host-microbial interactions

Genomic approaches continue to provide unprecedented insight into the microbiome, yet host immune interactions with diverse microbiota can be difficult to study. We therefore generated a microbial microarray containing defined antigens isolated from a broad range of microbial flora to examine adaptive and innate immunity. Serological studies with this microarray show that immunoglobulins from multiple mammalian species have unique patterns of reactivity, whereas exposure of animals to distinct microbes induces specific serological recognition. Although adaptive immunity exhibited plasticity toward microbial antigens, immunological tolerance limits reactivity toward self. We discovered that several innate immune galectins show specific recognition of microbes that express self-like antigens, leading to direct killing of a broad range of Gram-negative and Gram-positive microbes. Thus, host protection against microbes seems to represent a balance between adaptive and innate immunity to defend against evolving antigenic determinants while protecting against molecular mimicry.

Whole CMV proteome pattern recognition analysis after HSCT identifies unique epitope targets associated with the CMV status

Cytomegalovirus (CMV) infection represents a vital complication after Hematopoietic Stem Cell Transplantation (HSCT). We screened the entire CMV proteome to visualize the humoral target epitope-focus profile in serum after HSCT. IgG profiling from four patient groups (donor and/or recipient +/− for CMV) was performed at 6, 12 and 24 months after HSCT using microarray slides containing 17174 of 15mer-peptides overlapping by 4 aa covering 214 proteins from CMV. Data were analyzed using maSigPro, PAM and the ‘exclusive recognition analysis (ERA)’ to identify unique CMV epitope responses for each patient group. The ‘exclusive recognition analysis’ of serum epitope patterns segregated best 12 months after HSCT for the D+/R+ group (versus D−/R−). Epitopes were derived from UL123 (IE1), UL99 (pp28), UL32 (pp150), this changed at 24 months to 2 strongly recognized peptides provided from UL123 and UL100. Strongly (IgG) recognized CMV targets elicited also robust cytokine production in T-cells from patients after HSCT defined by intracellular cytokine staining (IL-2, TNF, IFN and IL-17). High-content peptide microarrays allow epitope profiling of entire viral proteomes; this approach can be useful to map relevant targets for diagnostics and therapy in patients with well defined clinical endpoints. Peptide microarray analysis visualizes the breadth of B-cell immune reconstitution after HSCT and provides a useful tool to gauge immune reconstitution.

Four assay designs and on-chip calibration: gadgets for a sepsis protein array

A protein microarray for the early stage diagnosis of sepsis that allows the simultaneous detection of C-reactive protein (CRP) (2-200 μg/mL), procalcitonin (PCT) (0.2-50 ng/mL), and interleukin 6 (IL-6) (2-2000 pg/mL) has been developed. To enable the parallel detection of the differently abundant analytes, the low binding affinity between CRP and phosphocholine is exploited in a "low-sensitive" sandwich assay for CRP. The calibration is integrated directly on the chip resulting in a "one patient-one array" format, to provide a user-friendly and rapid diagnostic tool. Four different assay designs are introduced: (I) the classical assay that works with biotin-streptavidin chemistry, (II) the rapid assay that is performed in a single detection step, and two ultrasensitive assay designs accomplished either by (III) an enzymatic or (IV) an antibody mediated amplification resulting in high density labeling. The assay designs were evaluated by the repetitive measurement of low, medium, and high concentration levels of commercially available certified control sera. The precision was similar across all assay designs (coefficient of variation (CV), CVintra: 8-14%; CVinter: 18-34%), while the sensitivity (limits of detection (LODs)) increased by 1 order of magnitude for the ultrasensitive assays (III, IV) and the accuracy was analyte dependent but best for the classical (I) and the antibody amplified (IV) assays.

Evaluation of a novel array-based toxoplasma, rubella, cytomegalovirus, and herpes simplex virus IgG enzyme linked immunosorbent assay and its comparison with virion/serion enzyme linked immunosorbent assays

Background

The dramatic increase in use of the IgG test for toxoplasma, rubella, cytomegalovirus (CMV), and herpes simplex virus (HSV) [TORCH] has led to the requirement for a high-efficiency method that can be used in the clinical laboratory. This study aimed to compare the results of BGI-Array ELISA TORCH IgG (BGI-GBI, China) screening method to those of Virion/Serion TORCH IgG ELISA (Virion/Serion, Germany).

Methods

Serum specimens (n=400) submitted for routine IgG testing by Virion/Serion ELISA were also tested using the BGI-Array ELISA method. The agreements of these two kinds of method were analyzed by κ-coefficients calculation.

Results

Following repeat testing, the BGI-Array ELISA TORCH IgG assays demonstrated agreements of 99.5% (398/400 specimens), 98% (392/400 specimens), 99% (396/400 specimens), and 99.5% (398/400 specimens), respectively. The BGI-Array ELISA IgG assays provided results comparable to Virion/Serion ELISA results, with κ-coefficients showing near-perfect agreement for the HSV (κ=0.87), rubella (κ=0.92) and CMV (κ=0.93) and substantial agreement for the toxoplasma (κ=0.80) IgG assays. The use of the BGI-Array ELISA TORCH IgG assays could reduce the turnaround time (1.5 hr vs. 5 hr by Virion/Serion ELISA for 100 specimens) and were easy to use.

Conclusions

BGI-Array ELISA TORCH IgG shows a good agreement with Virion/Serion ELISA methods and is suitable for clinical application.

Protein chips for high-throughput doping screening in athletes

Sport and doping are a contradiction in terms, however, doping abuse in sports has been a serious problem for many years. The systematic screening of every athlete for all prohibited drugs should be an indispensable feature of the Olympic Games. The gas chromatography mass spectrometry method is reserved as a reference method, but is limited by its low throughput. The advent of protein chip technology may enable the screening of all athletes for any illegal use of drugs.

Novel microarrays for simultaneous serodiagnosis of multiple antiviral antibodies

We developed an automated diagnostic system for the detection of virus-specific immunoglobulin Gs (IgGs) that was based on a microarray platform. We compared efficacies of our automated system with conventional enzyme immunoassays (EIAs). Viruses were immobilized to microarrays using a radical cross-linking reaction that was induced by photo-irradiation. A new photoreactive polymer containing perfluorophenyl azide (PFPA) and poly(ethylene glycol) methacrylate was prepared and coated on plates. Inactivated measles, rubella, mumps, Varicella-Zoster and recombinant Epstein-Barr viruse antigen were added to coated plates, and irradiated with ultraviolet light to facilitate immobilization. Virus-specific IgGs in healthy human sera were assayed using these prepared microarrays and the results obtained compared with those from conventional EIAs. We observed high correlation (0.79-0.96) in the results between the automated microarray technique and EIAs. The microarray-based assay was more rapid, involved less reagents and sample, and was easier to conduct compared with conventional EIA techniques. The automated microarray system was further improved by introducing reagent storage reservoirs inside the chamber, thereby conserving the use of expensive reagents and antibodies. We considered the microarray format to be suitable for rapid and multiple serological diagnoses of viral diseases that could be developed further for clinical applications.

Quantifying antibody binding on protein microarrays using microarray nonlinear calibration

We present a microarray nonlinear calibration (MiNC) method for quantifying antibody binding to the surface of protein microarrays that significantly increases the linear dynamic range and reduces assay variation compared with traditional approaches. A serological analysis of guinea pig Mycobacterium tuberculosis models showed that a larger number of putative antigen targets were identified with MiNC, which is consistent with the improved assay performance of protein microarrays. MiNC has the potential to be employed in biomedical research using multiplex antibody assays that need quantitation, including the discovery of antibody biomarkers, clinical diagnostics with multi-antibody signatures, and construction of immune mathematical models.

Pneumonia pathogen detection and microbial interactions in polymicrobial episodes

Recent reports show that microbial communities associated with respiratory infections, such as pneumonia and cystic fibrosis, are more complex than expected. Most of these communities are polymicrobial and might comprise microorganisms originating from several diverse biological and ecological sources. Moreover, unexpected bacteria in the etiology of these respiratory infections have been increasingly identified. These findings were established with the use of efficient microbiological diagnostic tools, particularly molecular tools based on common gene amplification, followed by cloning and sequencing approaches, which facilitated the identification of the polymicrobial flora. Similarly, recent investigations reported that microbial interactions might exist between species in polymicrobial communities, including typical pneumonia pathogens, such as Pseudomonas aeruginosa and Candida albicans. Here, we review recent tools for microbial diagnosis, in particular, of intensive care unit pneumonia and the reported interactions between microbial species that have primarily been identified in the etiology of these infections.

Serologic prevalence of amoeba-associated microorganisms in intensive care unit pneumonia patients

BACKGROUND

Patients admitted to intensive care units are frequently exposed to pathogenic microorganisms present in their environment. Exposure to these microbes may lead to the development of hospital-acquired infections that complicate the illness and may be fatal. Amoeba-associated microorganisms (AAMs) are frequently isolated from hospital water networks and are reported to be associated to cases of community and hospital-acquired pneumonia.

METHODOLOGY/PRINCIPAL FINDINGS

We used a multiplexed immunofluorescence assay to test for the presence of antibodies against AAMs in sera of intensive care unit (ICU) pneumonia patients and compared to patients at the admission to the ICU (controls). Our results show that some AAMs may be more frequently detected in patients who had hospital-acquired pneumonia than in controls, whereas other AAMs are ubiquitously detected. However, ICU patients seem to exhibit increasing immune response to AAMs when the ICU stay is prolonged. Moreover, concomitant antibodies responses against seven different microorganisms (5 Rhizobiales, Balneatrix alpica, and Mimivirus) were observed in the serum of patients that had a prolonged ICU stay.

CONCLUSIONS/SIGNIFICANCE

Our work partially confirms the results of previous studies, which show that ICU patients would be exposed to water amoeba-associated microorganisms, and provides information about the magnitude of AAM infection in ICU patients, especially patients that have a prolonged ICU stay. However, the incidence of this exposure on the development of pneumonia remains to assess.

Surface-activated microtiter-plate microarray for simultaneous CRP quantification and viral antibody detection

Microarrays are widely used in high-throughput DNA and RNA hybridization tests and recently adopted to protein and small molecule interaction studies in basic research and diagnostics. Parallel detection of serum antibodies and antigens has several potential applications in epidemiologic research, vaccine development, and in the diagnosis of allergies, autoimmunity, and infectious diseases. This study demonstrates an immobilization method for immunoassay-based microarray in conventional 96-well polystyrene plates for a serologic diagnostic method combined with quantitative C-reactive protein (CRP) assay. A synthetic peptide (HIV-1), a recombinant protein (Puumala hantavirus nucleocapsid), and purified virus preparations (Sindbis and adenoviruses) were used as antigens for virus-specific antibody detection and monoclonal anti-CRP antibody for antigen detection. The microarray was based on conventional enzyme immunoassays and densitometry from photographed results. Peptide and recombinant antigens functioned well, while whole virus antigens gave discrepant results in 1 out of 23 samples from the reference method, tested with human sera with various antibody responses. The CRP results were in concordance in the concentration range 0.5-150 mg/L with 2 commercially available CRP assays: ReaScan rapid test (R(2) = 0.9975) and Cobas 6000 analyzer (R(2) =0.9595). The results indicate that microtiter plates provide a promising platform for further development of microarrays for parallel antibody and antigen detection.

Multiplexed infectious protein microarray immunoassay suitable for the study of the specificity of monoclonal immunoglobulins

Enzyme-linked immunosorbent assays (ELISAs) used to detect antibodies specific for common infectious agents such as Epstein-Barr virus (EBV), cytomegalovirus (CMV), Toxoplasma gondii (T. gondii), and hepatitis C virus (HCV) are time-consuming and require large volumes of samples, which restrict their use. We propose a new assay based on a multiplexed infectious protein (MIP) microarray combining different epitopes representative of the four germs. Antigens and lysates were printed on nitrocellulose slides to constitute the microarray. First, the microarray was incubated with human serum samples. Then, the suitability of the microarray for analysis of the specificity of purified monoclonal immunoglobulin (mc Ig) was assessed using serum and mc Ig of HCV-positive patients. Bound human immunoglobulin G (IgG) was detected using fluorescently labeled secondary antibodies, and the signals were quantified. Results obtained in serum samples with the new MIP microarray immunoassay were compared with ELISAs; we observed concordances of 95% for EBV, 93% for CMV, 91% for T. gondii, and 100% for HCV. Regarding purified mc Ig of HCV-positive patients, 3 of 3 recognized antigens printed on the microarray. Hence, the novel EBV/CMV/T. gondii/HCV MIP microarray allows simultaneous diagnosis of polyclonal and monoclonal immune response to infectious diseases using very small volume samples.

Peptide microarray analysis of in silico-predicted epitopes for serological diagnosis of Toxoplasma gondii infection in humans

Toxoplasma gondii infections occur worldwide in humans and animals. In immunocompromised or prenatally infected humans, T. gondii can cause severe clinical symptoms. The identification of specific epitopes on T. gondii antigens is essential for the improvement and standardization of the serological diagnosis of toxoplasmosis. We selected 20 peptides mimicking linear epitopes on GRA1, GRA2, GRA4, and MIC3 antigenic T. gondii proteins in silico using the software ABCpred. A further 18 peptides representing previously published epitopes derived from GRA1, SAG1, NTPase1, and NTPase2 antigens were added to the panel. A peptide microarray assay was established to prove the diagnostic performance of the selected peptides with human serum samples. Seropositive human serum samples (n = 184) were collected from patients presenting with acute toxoplasmosis (n = 21), latent T. gondii infection (n = 53), and inactive ocular toxoplasmosis (n = 10) and from seropositive forest workers (n = 100). To adjust the cutoff values for each peptide, sera from seronegative forest workers (n = 75) and patients (n = 65) were used. Univariate logistic regression suggested the significant diagnostic potential of eight novel and two previously published peptides. A test based on these peptides had an overall diagnostic sensitivity of 69% (100% in ocular toxoplasmosis patients, 86% in acutely infected patients, 81% in latently infected patients, and 57% in seropositive forest workers). The analysis of seronegative sera performed with these peptides revealed a diagnostic specificity of 84%. The results of our study suggest that the use of a bioinformatic approach for epitope prediction in combination with peptide microarray testing is a powerful method for the selection of T. gondii epitopes as candidate antigens for serological diagnosis.

Analysis of clonal type-specific antibody reactions in Toxoplasma gondii seropositive humans from Germany by peptide-microarray

Background

Different clonal types of Toxoplasma gondii are thought to be associated with distinct clinical manifestations of infections. Serotyping is a novel technique which may allow to determine the clonal type of T. gondii humans are infected with and to extend typing studies to larger populations which include infected but non-diseased individuals.

Methodology

A peptide-microarray test for T. gondii serotyping was established with 54 previously published synthetic peptides, which mimic clonal type-specific epitopes. The test was applied to human sera (n = 174) collected from individuals with an acute T. gondii infection (n = 21), a latent T. gondii infection (n = 53) and from T. gondii-seropositive forest workers (n = 100).

Findings

The majority (n = 124; 71%) of all T. gondii seropositive human sera showed reactions against synthetic peptides with sequences specific for clonal type II (type II peptides). Type I and type III peptides were recognized by 42% (n = 73) or 16% (n = 28) of the human sera, respectively, while type II–III, type I–III or type I–II peptides were recognized by 49% (n = 85), 36% (n = 62) or 14% (n = 25) of the sera, respectively. Highest reaction intensities were observed with synthetic peptides mimicking type II-specific epitopes. A proportion of the sera (n = 22; 13%) showed no reaction with type-specific peptides. Individuals with acute toxoplasmosis reacted with a statistically significantly higher number of peptides as compared to individuals with latent T. gondii infection or seropositive forest workers.

Conclusions

Type II-specific reactions were overrepresented and higher in intensity in the study population, which was in accord with genotyping studies on T. gondii oocysts previously conducted in the same area. There were also individuals with type I- or type III-specific reactions. Well-characterized reference sera and further specific peptide markers are needed to establish and to perform future serotyping approaches with higher resolution.

An antigen microarray immunoassay for multiplex screening of mouse monoclonal antibodies

The mouse monoclonal antibody (mAb) technology still represents a key source of reagents for research and clinical diagnosis, although it is relatively inefficient and expensive and therefore unsuitable for high-throughput production against a vast repertoire of antigens. In this article, we describe a protocol that combines the immunization of individual mice with complex mixtures of influenza virus strains and a microarray-based immunoassay procedure to perform a parallel screening against the viral antigens. The protocol involves testing the supernatants of somatic cell hybrids against a capture substratum containing an array of different antigens. For each fusion experiment, we carried out more than 25,000 antigen-antibody reactivity tests in less than a week, a throughput that is two orders of magnitude higher than that of traditional antibody detection assays such as enzyme-linked immunosorbent assays and immunofluorescence. Using a limited number of mice, we can develop a vast repertoire of mAbs directed against nuclear and surface proteins of several human and avian influenza virus strains.

Detection of blood-transmissible agents: can screening be miniaturized?

Transfusion safety relating to blood-transmissible agents is a major public health concern, particularly when faced with the continuing emergence of new infectious agents. These include new viruses appearing alongside other known reemerging viruses (West Nile virus, Chikungunya) as well as new strains of bacteria and parasites (Plasmodium falciparum, Trypanosoma cruzi) and finally pathologic prion protein (variant Creutzfeldt-Jakob disease). Genomic mutations of known viruses (hepatitis B virus, hepatitis C virus, human immunodeficiency virus) can also be at the origin of variants susceptible to escaping detection by diagnostic tests. New technologies that would allow the simultaneous detection of several blood-transmissible agents are now needed for the development and improvement of screening strategies. DNA microarrays have been developed for use in immunohematology laboratories for blood group genotyping. Their application in the detection of infectious agents, however, has been hindered by additional technological hurdles. For instance, the variability among and within genomes of interest complicate target amplification and multiplex analysis. Advances in biosensor technologies based on alternative detection strategies have offered new perspectives on pathogen detection; however, whether they are adaptable to diagnostic applications testing biologic fluids is under debate. Elsewhere, current nanotechnologies now offer new tools to improve the sample preparation, target capture, and detection steps. Second-generation devices combining micro- and nanotechnologies have brought us one step closer to the potential development of innovative and multiplexed approaches applicable to the screening of blood for transmissible agents.

Protein subcellular localization profiling of breast cancer cells by dissociable antibody microarray staining

We have developed dissociable antibody microarray (DAMA) staining technology that provides a new approach to the global analysis of protein subcellular localization (SCL) in fixed cells. We have developed and optimized this technology for protein SCL profiling, generated ChipView, a program for management and analysis of molecular image database, and utilized the technique to identify proteins with unique SCL in breast cancer cell lines. We compared the SCL profiles of 325 proteins among nine different breast cell lines, and have identified one protein, Cyclin B1, with distinctively different SCLs between normal and cancer cell lines. With classic individual immunostaining, Cyclin B1 was confirmed to localize to the cytoplasm of seven breast cancer cell lines and in both cytoplasm and nuclei of two normal breast cell lines, and to have higher expression levels in the cancer cell lines tested.

Optically induced linking of protein and nanoparticles to gold surfaces

Attachment of molecules and proteins to surfaces is of great interest for the development of a large variety of applications. We present herein a novel approach to efficiently couple a molecule of choice to biological building blocks. We synthesized and employed a new derivative of 5-bromo-7-nitroindoline to attach nucleophilic molecules and proteins to gold surfaces by photochemical activation. The reaction can be seen as a photoactivated alternative to the activated ester type chemistries that are commonly used to attach proteins or molecules to surfaces. We characterize the reaction by UV-vis and NMR spectroscopy, and as test of principle experiment, we show that we can attach proteins to surfaces and demonstrate that we can functionalize gold nanoparticles by this optically induced cross-linking reaction.

Microarrays: molecular allergology and nanotechnology for personalised medicine (I)

The diagnosis of antibody-mediated allergic disorders is based on the clinical findings and the detection of allergen-specific IgE based on in vitro and in vivo techniques, together with allergen provocation tests. In vitro diagnostic techniques have progressed enormously following the introduction of the advances made in proteomics and nanotechnology--offering tools for the diagnosis and investigation of allergy at molecular level. The most advanced developments are the microarray techniques, which in genomics allowed rapid description of the human genetic code, and which now have been applied to proteomics, broadening the field for research and clinical use. Together with these technological advances, the characterisation of most of the different proteins generating specific IgE and which conform each natural allergen, as well as their purification or genetic engineering-based synthesis, have been crucial elements--offering the possibility of identifying disease-causing allergens at molecular level, establishing a component-resolved diagnosis (CRD), using them to study the natural course of the disease, and applying them to improvements in specific immunotherapy. Microarrays of allergic components offer results relating to hundreds of these allergenic components in a single test, and use a small amount of serum that can be obtained from capillary blood. The availability of new molecules will allow the development of panels including new allergenic components and sources, which will require evaluation for clinical use. The present study reviews these new developments, component-resolved diagnosis, and the development of microarray techniques as a critical element for furthering our knowledge of allergic disease.

Rapid and simultaneous detection of Ureaplasma parvum and Chlamydia trachomatis antibodies based on visual protein microarray using gold nanoparticles and silver enhancement

Based on gold-labeled silver stain (GLSS) method, we developed the visual protein microarray for simultaneous, sensitive, and specific detection of Ureaplasma parvum and Chlamydia trachomatis using N-terminus multiple-banded antigen (NMBA) of U. parvum and major outer membrane protein of C. trachomatis. The specific antigens were immobilized on glass surface that was treated with 3-glycidoxypropyltrimethoxysilane, and they were used as the capturing probes to recognize the complementary target antibodies binding to the detecting probes of Nano-gold-Staphylococcal protein A (SPA). In the "sandwich" format, Nano-gold-SPA probe was used as an indicator and GLSS was applied to amplify the detection signals and produce black image on array spots, which were visible with naked eyes. In our model arrays, the detection limit of protein microarray was as low as 2 ng/mL, and the lowest titer of detectable antibody was 1:128; thus, this sensitivity was comparable to the fluorescent detection method. The visual simultaneous protein microarrays were used to detect total 186 clinical samples, which had been determined by enzyme-linked immunosorbent assay (ELISA) and fluorescence quantitative real-time polymerase chain reaction; the results were identical and no distinct difference (P > 0.05) existed between them. Our results demonstrate that we have developed the visual protein microarray technique, which is of high sensitivity and high specificity, and it may have potential in clinical applications.

In situ chemical modification of peptide microarrays: application to the study of the antibody responses to methylated antigens

Peptide microarrays are useful tools for characterizing the humoral response against methylated antigens. They are usually prepared by printing unmodified and methylated peptides on substrates such as functionalized microscope glass slides. The preferential capture of antibodies by methylated peptides suggests the specific recognition of methylated epitopes. However, unmodified peptide epitopes can be masked due to their interaction with the substrate. The accessibility of unmodified peptides and thus the specificity of the recognition of methylated peptide epitopes can be probed using the in situ methylation procedure described here. Alternately, the in situ methylation of peptide microarrays allows probing the presence of antibodies directed toward methylated epitopes starting from easy-to-make and cost-effective unmodified peptide libraries. In situ methylation was performed using formaldehyde in the presence of sodium cyanoborohydride and nickel chloride. This chemical procedure converts lysine residues into mono- or dimethyl lysines.

Magnetic bead-based detection of autoimmune responses using protein microarrays

In the present study, a magnetic bead-based detection approach for protein microarrays is described as an alternative approach to the commonly used fluorescence-based detection system. Using the bead-based detection approach with applied magnetic force, it was possible to perform the detection step more rapidly as a result of the accelerated binding between the captured analyte in the microspot and the detection antibody, which was coupled to the magnetic beads. The resulting strong opacity shift on the microspots could be recorded with an ordinary flatbed scanner. In the context of autoimmunity, a set of 24 serum samples was analyzed for the presence of antibodies against 12 autoantigens using standard fluorescence and magnetic bead-based detection methods. Dynamic range, sensitivity, and specificity were determined for both detection methods. We propose from our findings that the magnetic bead-based detection option provides a simplified and cost effective readout method for protein microarrays.

Application of physicochemically modified silicon substrates as reverse-phase protein microarrays

Physicochemically modified silicon substrates can provide a high quality alternative to nitrocellulose-coated glass slides for use in reverse-phase protein microarrays. Enhancement of protein microarray sensitivities is an important goal, especially because molecular targets within patient tissues exist in low abundance. The ideal array substrate has a high protein binding affinity and low intrinsic background signal. Silicon, which has low intrinsic autofluorescence, is being explored as a potential microarray surface. In a previous paper ( Nijdam , A. J. ; Cheng , M. M.-C. ; Fedele , R. ; Geho , D. H. ; Herrmann , P. ; Killian , K. ; Espina , V. ; Petricoin , E. F. ; Liotta , L. A. ; Ferrari , M. Physicochemically Modified Silicon as Substrate for Protein Microarrays . Biomaterials 2007 , 28 , 550 - 558 ), it is shown that physicochemical modification of silicon substrates increases the binding of protein to silicon to a level comparable with that of nitrocellulose. Here, we apply such substrates in a reverse-phase protein microarray setting in two model systems.

Serological microarray for detection of HSV-1, HSV-2, VZV, and CMV antibodies

The seroprevalence of human herpesviruses is high and reactivations occur frequently. A microarray was designed and tested for the detection of IgG and IgM antibodies for Puumala hantavirus (PUUV) and IgG antibodies against four herpesviruses. Initially, a microarray platform was set up using an unrelated in-house antigen, PUUV recombinant nucleocapsid protein, to optimize the protocol for the detection of antibodies. Detection of the four herpesviruses was set up in a microarray using the recombinant proteins of herpes simplex virus (HSV) glycoprotein G1 and G2, varicella-zoster virus (VZV) glycoprotein E, and cytomegalovirus (CMV) pp150 phosphoprotein. The results of the PUUV panel were in good agreement with the PUUV IgG immunofluorescent assay and IgM enzyme immunoassay (EIA). Seropositive and negative clinical reference panels were tested for herpesviruses by the serological microarray, and the results were compared to those of individual EIAs used for standard diagnostic purposes. The serologic microarray for HSV, VZV and CMV antibody detection gave good specificities for IgG. However, sensitivities of the assay varied depending on the herpesvirus detected. The serological microarray showed potential for screening purposes. The microarray based analyses were easy to perform, and HSV-1, HSV-2, VZV, and CMV antibodies could be detected on the same microarray.

Characterization of Clostridium species utilizing liquid chromatography/mass spectrometry of intact proteins

A method for biomarker candidate discovery and strain level pathogen characterization using liquid chromatography/mass spectrometry (LC/MS) with electrospray ionization is described. This method was applied to two pathogenic Clostridium species: C. difficile and C. perfringens. Seven marker proteins per species (fourteen total) were successfully implemented to speciate unknowns during a blind study and could enhance serological and genetic approaches by serving as new targets for detection. Two sets of C. perfringens isolates that were 100% similar by pulsed-field gel electrophoresis (PFGE) were distinguished using LC/MS, demonstrating the high specificity of this approach. The use of LC/MS is less labor intensive than PFGE, affords greater specificity than real-time PCR, and requires no primers or antibodies.

Diagnostic microbiologique : du diagnostic par étiologie au diagnostic par syndrome

Objectifs

Depuis les dix dernières années, l’introduction de la biologie moléculaire et l’automatisation ont radicalement changé les pratiques dans les laboratoires de microbiologie clinique. L’amélioration de la communication entre les microbiologistes et les cliniciens ainsi que les évolutions technologiques telles que la standardisation et le développement de tests diagnostics plus rapides ont conduit à une réorganisation des laboratoires de microbiologie.

Méthodes

Jusqu’à présent la prescription des examens ciblait un diagnostic étiologique précis, actuellement l’évolution se fait vers le diagnostic par syndrome incluant un panel de tests regroupant les étiologies responsables d’un syndrome donné y compris les pathogènes émergents.

Résultats et conclusions

Dans cette revue, nous avons résumé les développements technologiques les plus récents en matière de diagnostic microbiologique adapté au diagnostic par syndrome incluant les stratégies de diagnostic exhaustif, les DNA microarray et les microarray antigéniques.