Quantification of recombinant core-like particles of bluetongue virus using immunosorbent electron microscopy

Glycoprotein- and Lectin-Based Approaches for Detection of Pathogens

Infectious diseases alone are estimated to result in approximately 40% of the 50 million total annual deaths globally. The importance of basic research in the control of emerging and re-emerging diseases cannot be overemphasized. However, new nanotechnology-based methodologies exploiting unique surface-located glycoproteins or their patterns can be exploited to detect pathogens at the point of use or on-site with high specificity and sensitivity. These technologies will, therefore, affect our ability in the future to more accurately assess risk. The critical challenge is making these new methodologies cost-effective, as well as simple to use, for the diagnostics industry and public healthcare providers. Miniaturization of biochemical assays in lab-on-a-chip devices has emerged as a promising tool. Miniaturization has the potential to shape modern biotechnology and how point-of-care testing of infectious diseases will be performed by developing smart microdevices that require minute amounts of sample and reagents and are cost-effective, robust, and sensitive and specific. The current review provides a short overview of some of the futuristic approaches using simple molecular interactions between glycoproteins and glycoprotein-binding molecules for the efficient and rapid detection of various pathogens at the point of use, advancing the emerging field of glyconanodiagnostics.

Exploitation of microbial forensics and nanotechnology for the monitoring of emerging pathogens

Emerging infectious diseases remain among the leading causes of global mortality. Traditional laboratory diagnostic approaches designed to detect and track infectious disease agents provide a framework for surveillance of bio threats. However, surveillance and outbreak investigations using such time-consuming approaches for early detection of pathogens remain the major pitfall. Hence, reasonable real-time surveillance systems to anticipate threats to public health and environment are critical for identifying specific aetiologies and preventing the global spread of infectious disease. The current review discusses the growing need for monitoring and surveillance of pathogens with the same zeal and approach as adopted by microbial forensics laboratories, and further strengthening it by integrating with the innovative nanotechnology for rapid detection of microbial pathogens. Such innovative diagnostics platforms will help to track pathogens from high risk areas and environment by pre-emptive approach that will minimize damages. The various scenarios with the examples are discussed where the high risk associated human pathogens in particular were successfully detected using various nanotechnology approaches with potential future prospects in the field of microbial forensics.

Identification and classification of respiratory syncytial virus (RSV) strains by surface-enhanced Raman spectroscopy and multivariate statistical techniques

There is a critical need for a rapid and sensitive means of detecting viruses. Recent reports from our laboratory have shown that surface-enhanced Raman spectroscopy (SERS) can meet these needs. In this study, SERS was used to obtain the Raman spectra of respiratory syncytial virus (RSV) strains A/Long, B1, and A2. SERS-active substrates composed of silver nanorods were fabricated using an oblique angle vapor deposition method. The SERS spectra obtained for each virus were shown to possess a high degree of reproducibility. Based on their intrinsic SERS spectra, the four virus strains were readily detected and classified using the multivariate statistical methods principal component analysis (PCA) and hierarchical cluster analysis (HCA). The chemometric results show that PCA is able to separate the three virus strains unambiguously, whereas the HCA method was able to readily distinguish an A2 strain-related G gene mutant virus (DeltaG) from the A2 strain. The results described here demonstrate that SERS, in combination with multivariate statistical methods, can be utilized as a highly sensitive and rapid viral identification and classification method.

Low-level detection of viral pathogens by a surface-enhanced Raman scattering based immunoassay

The need for rapid, highly sensitive, and versatile diagnostic tests for viral pathogens spans from human and veterinary medicine to bioterrorism prevention. As an approach to meet these demands, a diagnostic test employing monoclonal antibodies (mAbs) for the selective extraction of viral pathogens from a sample in a chip-scale, sandwich immunoassay format has been developed using surface-enhanced Raman scattering (SERS) as a readout method. The strengths of SERS-based detection include its inherent high sensitivity and facility for multiplexing. The capability of this approach is demonstrated by the capture of feline calicivirus (FCV) from cell culture media that is exposed to a gold substrate modified with a covalently immobilized layer of anti-FCV mAbs. The surface-bound FCVs are subsequently coupled with an extrinsic Raman label (ERL) for identification and quantification. The ERLs consist of 60-nm gold nanoparticles coated first with a layer of Raman reporter molecules and then a layer of mAbs. The Raman reporter molecule is strategically designed to chemisorb as a thiolate adlayer on the gold nanoparticle, to provide a strong and unique spectral signature, and to covalently link a layer of mAbs to the gold nanoparticle. The last feature provides a means to selectively tag substrate-bound FCV. This paper describes the development of the assay, which uses cell culture media as a sample matrix and has a linear dynamic range of 1 x 10(6)-2.5 x 10(8) viruses/mL and a limit of detection of 1 x 10(6) viruses/mL. These results reflect the findings from a detailed series of investigations on the effects of several experimental parameters (e.g., salt concentration, ERL binding buffer, and sample agitation), all of which were aimed at minimizing nonspecific binding and maximizing FCV binding efficiency. The performance of the assay is correlated with the number of captured FCV, determined by atomic force microscopy, as a means of method validation.

Control of antigen mass transfer via capture substrate rotation: An absolute method for the determination of viral pathogen concentration and reduction of heterogeneous immunoassay incubation times

Immunosorbent assays are commonly employed as diagnostic tests in human healthcare, veterinary medicine and bioterrorism prevention. These assays, however, often require long incubation times, limiting sample throughput. As an approach to overcome this weakness, this paper examines the use of rotating capture substrates to increase the flux of antigen to the surface, thereby reducing the incubation time. To assess the capability of this approach, porcine parvovirus (PPV) was selectively extracted from solution by systematically varying the rotation rate of a gold substrate modified with a layer of anti-PPV monoclonal antibodies. The captured PPV were then directly imaged and quantified by atomic force microscopy. The benefits of substrate rotation are demonstrated by comparing an assay performed under stagnant conditions to one carried out with substrate rotation at 800 rpm, both for 10 min incubations at 25 degrees C. The use of rotation lowered the limit of detection to 3.4x10(4)TCID50/mL (approximately 80 fM) from 3.2x10(5)TCID50/mL (approximately 800 fM) under stagnant conditions. Results are also presented that show this strategy can be used: (1) to determine antigen concentrations without standards and (2) to establish the numerical relationship between quantal concentration units (e.g., 50% tissue culture infective dose (TCID50)) and quantitative concentration units (e.g., viruses/mL) The potential to broadly apply this technique to heterogeneous immunoassays is also briefly discussed.

Rapid and sensitive detection of respiratory virus molecular signatures using a silver nanorod array SERS substrate

A spectroscopic assay based on surface enhanced Raman scattering (SERS) using silver nanorod array substrates has been developed that allows for rapid detection of trace levels of viruses with a high degree of sensitivity and specificity. This novel SERS assay can detect spectral differences between viruses, viral strains, and viruses with gene deletions in biological media. The method provides rapid diagnostics for detection and characterization of viruses generating reproducible spectra without viral manipulation.

A single chain Fv antibody displayed on phage surface recognises conformational group-specific epitope of bluetongue virus

A single chain fragment variable (scFv) antibody gene was isolated from hybridoma cell line secreting monoclonal antibody (MAb) 20E9 that recognises bluetongue virus (BTV) VP7. DNA fragments encoding variable regions of heavy and light chains were amplified by RT-PCR and library of scFv was constructed in phage vector. Two scFv clones that were selected showed specific reactivity with conformational epitope VP7. The N-terminal 22 amino acid residues of 20E9 light chain were identical to that deduced from scFv DNA sequence. An in-frame TAG stop codon was found in the coding sequence and its potential role in regulating the expression and stability of scFv in phage is discussed.