Antigen biochips verify and extend the scope of antibody detection in Lyme borreliosis

Recent strategies for the diagnosis of early Lyme disease

Lyme disease (LD) is the most common tick-borne disease in the Northern Hemisphere. As the most prevalent vector-borne disease in the USA, LD affects 300,000 human cases each year. LD is caused by inoculation of the bacterial spirochete, Borrelia burgdorferi sensu lato, from an infected tick. If not treated quickly and completely, the bacteria disseminate from the tick's biting site into multiple organs including the joints, heart, and brain. Thus, the best outcome from medical intervention can be expected with early detection and treatment with antibiotics, prior to multi-organ dissemination. In the absence of a characteristic rash, LD is diagnosed using serological testing involving enzyme-linked immunosorbent assay (ELISA) followed by western blotting, which is collectively known as the two-tier algorithm. These assays detect host antibodies against the bacteria, but are hampered by low sensitivity, which can miss early LD cases. This review discusses the application of some current assays for diagnosing LD clinically, thus providing a foundation for exploring newer techniques being developed in the laboratory for more sensitive detection of early LD.

Establishment of N-succinimidyl 4-(maleimidomethyl) cyclohexanecarboxylate (SMCC) modified biochip enabling concurrent detection of serum infectious antibodies in neuroborreliosis

In this study, we developed a novel protein biochip that was modified with N-succinimidyl 4-(maleimidomethyl)cyclohexanecarboxylate (SMCC) and specialized for concurrent detection of serum IgG and IgM antibodies against Borrelia burgdorferi antigens, flagellin, outer surface protein C (OspC) and variable major protein-like sequence (VlsE) in the patients with neuroborreliosis (NB), respectively. Surface chemical characteristics of the biochips were validated with atomic force microscope (AFM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The visualized detection limit for IgG antibodies against flagellin, OspC and VlsE antigens on the biochip were 0.78 µg/ml, 0.78 µg/ml and 1.56 µg/ml, respectively. Finally, serum IgG and IgM antibodies in 72 patients with NB and 188 healthy individuals were tested on the biochip. The seroimmunological outcome by the biochip were evaluated in comparison with enzyme linked immunosorbent assay (ELISA) assay. The results demonstrated that the prevalences of IgG and IgM antibodies in the cases were 41.7%, 63.9% to flagellin; 20.8% and 51.4% to OspC and 76.4%, 62.5% to VlsE, respectively. Utilization of the biochip in detection IgM antibody against flagellin was compatible with ELISA assay (R(2)=0.849). Thus, the protein biochip would provide a potential platform not only for enabling detection of corresponding antibodies directed against B. burgdorferi antigens, but also for monitoring course of the disease.

Development of a novel protein biochip enabling validation of immunological assays and detection of serum IgG and IgM antibodies against Treponema pallidum pathogens in the patients with syphilis

In this study, we developed a novel protein biochip methodology that was characterized by dithiobis (succinimidyl undecanoate) (DSU) and specialized for detection of serum IgG and IgM antibodies against Treponema pallidum pathogens in the patients with syphilis, respectively. The biochips were validated by a dimension of atomic force microscope (AFM). The visualized detection limit of IgG antibody on the biochip was 0.39μg/ml. Finally, 286 serum samples from the patients with syphilis were simultaneously tested on the rTpN15-17-47 coated biochips. The results were evaluated in comparison with the assays of T. pallidum particle agglutination (TPPA) and the toluidine red unheated serum test (TRUST). The result demonstrated that the relative positive rate in the 286 patients by biochip was 99.0%, similar to that by TPPA (97.9%, P>0.05) and higher than that by TRUST, (76.2%, P<0.01). The detection specificities were 100% for the biochip and the TPPA and 97.0% for the TRUST. Thus, the protein biochip would provide a useful platform not only for enabling concurrent detection of the infectious antibodies directed against T. pallidum on a larger scale, but also for monitoring therapy modality of the disease.

Inferring epitopes of a polymorphic antigen amidst broadly cross-reactive antibodies using protein microarrays: a study of OspC proteins of Borrelia burgdorferi

Epitope mapping studies aim to identify the binding sites of antibody-antigen interactions to enhance the development of vaccines, diagnostics and immunotherapeutic compounds. However, mapping is a laborious process employing time- and resource-consuming ‘wet bench’ techniques or epitope prediction software that are still in their infancy. For polymorphic antigens, another challenge is characterizing cross-reactivity between epitopes, teasing out distinctions between broadly cross-reactive responses, limited cross-reactions among variants and the truly type-specific responses. A refined understanding of cross-reactive antibody binding could guide the selection of the most informative subsets of variants for diagnostics and multivalent subunit vaccines. We explored the antibody binding reactivity of sera from human patients and Peromyscus leucopus rodents infected with Borrelia burgdorferi to the polymorphic outer surface protein C (OspC), an attractive candidate antigen for vaccine and improved diagnostics for Lyme disease. We constructed a protein microarray displaying 23 natural variants of OspC and quantified the degree of cross-reactive antibody binding between all pairs of variants, using Pearson correlation calculated on the reactivity values using three independent transforms of the raw data: (1) logarithmic, (2) rank, and (3) binary indicators. We observed that the global amino acid sequence identity between OspC pairs was a poor predictor of cross-reactive antibody binding. Then we asked if specific regions of the protein would better explain the observed cross-reactive binding and performed in silico screening of the linear sequence and 3-dimensional structure of OspC. This analysis pointed to residues 179 through 188 the fifth C-terminal helix of the structure as a major determinant of type-specific cross-reactive antibody binding. We developed bioinformatics methods to systematically analyze the relationship between local sequence/structure variation and cross-reactive antibody binding patterns among variants of a polymorphic antigen, and this method can be applied to other polymorphic antigens for which immune response data is available for multiple variants.

Development of a protein biochip to identify 6 monoclonal antibodies against subtypes of recombinant human interferons

Recombinant human interferons (rhIFNs) are broadly used as effective therapeutic agents with antiviral, antitumor, and immune-modulating properties. Advances in protein biochip technology have benefited the medical community greatly, making true parallelism, miniaturization, and high throughput possible. In this study, 5 rhIFN proteins (IFN-alpha1b, IFN-alpha2a, IFN-alpha2b, IFN-beta, and IFN-gamma) were immobilized onto an N-hydroxysuccinimide (NHS)-modified gold-based biochip. The protein biochip was incubated with 6 specific mouse IgG antibodies (AK1, AK2, AK3, AK4, BK1, and CK1) against the human IFNs and then with Cy3-conjugated goat anti-mouse IgG antibody. The results showed that monoclonal antibody AK1 presented a unique binding characteristic to IFN-alpha1b. AK2 reacted in immunoassays equally with IFN-alpha2a and IFN-alpha2b. AK3 detected IFN-alpha1b, IFN-alpha2a, and IFN-alpha2b. AK4 had positive immunological responses directed to both IFN-alpha1b and IFN-alpha2b. Monoclonal antibodies BK1 and CK1 recognized epitope of IFN-beta and IFN-gamma, specifically. The assay specificity of the biochip was further confirmed by enzyme-linked immunosorbent assay (ELISA) and western blotting. Finally, 88 serum samples from patients treated with rhIFN-alpha2b were simultaneously tested on a single biochip. The result demonstrated that 6.8% (6 of 88 cases) presented positive reactions to anti-IFN-alpha2b antibodies, indicating that the patients under rhIFN-alpha2b therapy produced neutralized antibody against the IFN. The biochip format would offer a competitive alternative tool not only for facilitating characterization of IFN subtypes but also potentially for enabling clinical serum detection of corresponding antibodies directed against IFNs.

A Quick and Parallel Analytical Method Based on Quantum Dots Labeling for ToRCH-Related Antibodies

Quantum dot is a special kind of nanomaterial composed of periodic groups of II-VI, III-V or IV-VI materials. Their high quantum yield, broad absorption with narrow photoluminescence spectra and high resistance to photobleaching, make them become a promising labeling substance in biological analysis. Here, we report a quick and parallel analytical method based on quantum dots for ToRCH-related antibodies including Toxoplasma gondii, Rubella virus, Cytomegalovirus and Herpes simplex virus type 1 (HSV1) and 2 (HSV2). Firstly, we fabricated the microarrays with the five kinds of ToRCH-related antigens and used CdTe quantum dots to label secondary antibody and then analyzed 100 specimens of randomly selected clinical sera from obstetric outpatients. The currently prevalent enzyme-linked immunosorbent assay (ELISA) kits were considered as "golden standard" for comparison. The results show that the quantum dots labeling-based ToRCH microarrays have comparable sensitivity and specificity with ELISA. Besides, the microarrays hold distinct advantages over ELISA test format in detection time, cost, operation and signal stability. Validated by the clinical assay, our quantum dots-based ToRCH microarrays have great potential in the detection of ToRCH-related pathogens.

A direct immunoassay assessment of streptavidin- and N-hydroxysuccinimide-modified biochips in validation of serological TNFalpha responses in hemophagocytic lymphohistiocytosis

The authors report 2 biochip platforms on gold manufactured by either nanoscale biotinylated self-assembled architectures to streptavidin surface or proteins containing free NH(2) groups to N-hydroxysuccinimide (NHS)-activated surfaces and investigated the potential application of tumor necrosis factor-alpha (TNFalpha) serodiagnosis of hemophagocytic lymphohistiocytosis (HLH). Interactions of TNFalpha antigen and TNFalpha antibody on the biochips were optimized using an indirect immunofluorescence method. Variation coefficients were 1.87% to 4.56% on the streptavidin biochip and 5.03% to 8.64% on the NHS biochip. The correlation coefficients (r) in TNFalpha and TNFalpha antibody assays in HLH patients between the 2 biochip formats were 0.9623 and 0.9386 and the concordance frequencies were 92.2% and 96.1%, respectively. To detect plasma TNFalpha-receptor complexes (TNFR1 and R2) in HLH, a biochip assay strategy was developed. Plasma levels of TNFalpha, TNFalpha antibody, and TNFalpha-receptor complexes (TNFR1 and R2) were detected in plasmas from 42 HLH cases using streptavidin biochips. Frequencies of the biomarkers in the plasmas were 40.5% (17/42) for TNFalpha, 30.9% (13/42) for TNFalpha antibody, 28.6% (12/42) for TNFalpha-receptor 1 complex, and 26.1% (11/42) for TNFalpha-receptor 2 complex, respectively. The streptavidin biochip format was more sensitive than the NHS surface and was demonstrated to be a valuable tool to identify individual biomarker molecules and molecular complexes in sera and cell lysates and to track therapeutic progress of patients.

Development of a fluorescent and colorimetric detection methods-based protein microarray for serodiagnosis of TORCH infections

We developed a protein microarray methodology that has the ability of serodiagnosis of IgM antibodies directed against TORCH pathogens. Six chemical surface modifications were validated by a dimension atomic force microscope (AFM) and contact angle measurement, agarose modified surface of which offered an appropriate platform for detecting IgM antibody. Further, signal amplification sensitivities on agarose modified microarrays were detected by Cy3-labeled biotin-streptavidin and immunogold-based assays. The detection limits of IgM antibody on the microarrays were 0.48 and 0.24 microg/ml, quantitatively equal to 0.25 and 12.5pg, respectively, on each spot as ascertained by the two assays. Satisfactory linear correlations between the signal intensity and the logarithm of the IgM concentration were obtained. Finally, 60 serum samples characterized by a commercial ELISA were evaluated by the protein microarray. There were good concordances between the results of the protein microarray and ELISA assay for sorting of the TORCH infected sera (95.0% by fluorescence-based assay and 96.7% by immunogold-based assay). Clearly, the potential application of this protein microarray format facilitates clinical detection of not only the antibodies directed against TORCH pathogens but also other autoimmune diseases.