Nanoparticle-Based biobarcode amplification assay (BCA) for sensitive and early detection of human immunodeficiency type 1 capsid (p24) antigen

Current applications and future trends of molecular diagnostics in clinical bacteriology

Molecular diagnostics of infectious diseases, in particular, nucleic-acid-based methods, are the fastest growing field in clinical laboratory diagnostics. These applications are stepwise replacing or complementing culture-based, biochemical, and immunological assays in microbiology laboratories. The first-generation nucleic acid assays were monoparametric such as conventional tests, determining only a single parameter. Improvements and new approaches in technology now open the possibility for the development of multiparameter assays using microarrays, multiplex nucleic acid amplification techniques, or mass spectrometry, while the introduction of closed-tube systems has resulted in rapid microbial diagnostics with a subsequently reduced contamination risk. Whereas the first assays were focused on the detection and identification of microbial pathogens, these new technologies paved the way for the parallel determination of multiple antibiotic resistance determinants or to perform microbial epidemiology and surveillance on a genetic level.

Detection of anthrax toxin by an ultrasensitive immunoassay using europium nanoparticles

We developed a europium nanoparticle-based immunoassay (ENIA) for the sensitive detection of anthrax protective antigen (PA). The ENIA exhibited a linear dose-dependent pattern within the detection range of 0.01 to 100 ng/ml and was approximately 100-fold more sensitive than enzyme-linked immunosorbent assay (ELISA). False-positive results were not observed with serum samples from healthy adults, mouse plasma without PA, or plasma samples collected from mice injected with anthrax lethal factor or edema factor alone. For the detection of plasma samples spiked with PA, the detection sensitivities for ENIA and ELISA were 100% (11/11 samples) and 36.4% (4/11 samples), respectively. The assay exhibited a linear but qualitative correlation between the PA injected and the PA detected in murine blood (r=0.97731; P<0.0001). Anthrax PA was also detected in the circulation of mice infected with spores from a toxigenic Sterne-like strain of Bacillus anthracis, but only in the later stages of infection. These results indicate that the universal labeling technology based on europium nanoparticles and its application may provide a rapid and sensitive testing platform for clinical diagnosis and laboratory research.

Detection of HIV-1 p24 Gag in plasma by a nanoparticle-based bio-barcode-amplification method

BACKGROUND

Detection of HIV-1 in patients is limited by the sensitivity and selectivity of available tests. The nanotechnology-based bio-barcode-amplification method offers an innovative approach to detect specific HIV-1 antigens from diverse HIV-1 subtypes. We evaluated the efficacy of this protein-detection method in detecting HIV-1 in men enrolled in the Chicago component of the Multicenter AIDS Cohort Study (MACS).

METHODS

The method relies on magnetic microparticles with antibodies that specifically bind the HIV-1 p24 Gag protein and nanoparticles that are encoded with DNA and antibodies that can sandwich the target protein captured by the microparticle-bound antibodies. The aggregate sandwich structures are magnetically separated from solution, and treated to remove the conjugated barcode DNA. The DNA barcodes (hundreds per target) were identified by a nanoparticle-based detection method that does not rely on PCR.

RESULTS

Of 112 plasma samples from HIV-1-infected subjects, 111 were positive for HIV-1 p24 Gag protein (range: 0.11-71.5 ng/ml of plasma) by the bio-barcode-amplification method. HIV-1 p24 Gag protein was detected in only 23 out of 112 men by the conventional ELISA. A total of 34 uninfected subjects were negative by both tests. Thus, the specificity of the bio-barcode-amplification method was 100% and the sensitivity 99%. The bio-barcode-amplification method detected HIV-1 p24 Gag protein in plasma from all study subjects with less than 200 CD4(+) T cells/microl of plasma (100%) and 19 out of 20 (95%) HIV-1-infected men who had less than 50 copies/ml of plasma of HIV-1 RNA. In a separate group of 60 diverse international isolates, representative of clades A, B, C and D and circulating recombinant forms CRF01_AE and CRF02_AG, the bio-barcode-amplification method identified the presence of virus correctly.

CONCLUSIONS

The bio-barcode-amplification method was superior to the conventional ELISA assay for the detection of HIV-1 p24 Gag protein in plasma with a breadth of coverage for diverse HIV-1 subtypes. Because the bio-barcode-amplification method does not require enzymatic amplification, this method could be translated into a robust point-of-care test.

Sensitivity by combination: immuno-PCR and related technologies

The versatility of immunoassays for the detection of antigens can be combined with the signal amplification power of nucleic acid amplification techniques in a broad range of innovative detection strategies. This review summarizes the spectrum of both, DNA-modification techniques used for assay enhancement and the resulting key applications. In particular, it focuses on the highly sensitive immuno-PCR (IPCR) method. This technique is based on chimeric conjugates of specific antibodies and nucleic acid molecules, the latter of which are used as markers to be amplified by PCR or related techniques for signal generation and read-out. Various strategies for the combination of antigen detection and nucleic acid amplification are discussed with regard to their laboratory analytic performance, including novel approaches to the conjugation of antibodies with DNA, and alternative pathways for signal amplification and detection. A critical assessment of advantages and drawbacks of these methods for a number of applications in clinical diagnostics and research is conducted. The examples include the detection of viral and bacterial antigens, tumor markers, toxins, pathogens, cytokines and other targets in different biological sample materials.

Improving defences at the portal of HIV entry: mucosal and innate immunity

The authors discuss the key scientific issues in mucosal and innate immunity related to immune protection against HIV infection.

Blood safety: Opportunities and challenges addressed through Critical Path research at FDA

New scientific discoveries and technologies create opportunities for medical and public health advancement through development of innovative products. However, novel products and technologies bring new challenges to regulation. FDA recently established a 'Critical Path' research initiative to modernize regulatory science concepts and tools to meet the challenges of the 21st century. Central to this initiative is the concept that regulatory science is distinct from the 'discovery' science that generates ideas for development of new drugs, biologics, or medical devices. In this article, the authors discuss the concepts of FDA 'Critical Path' research and review examples of such research performed in the Office of Blood Research and Review within the Center for Biologics Research and Evaluation at FDA to illustrate how the 'Critical Path' research is being used to address opportunities and challenges impacting blood and blood products.: