Development of an immunochromatographic strip test for antigen detection of elephant endotheliotropic herpesvirus in Asian elephants (Elephas maximus)

Elephant endotheliotropic herpesvirus (EEHV) is the causative agent of EEHV-hemorrhagic disease (EEHV-HD) in elephants worldwide. This disease is highly virulent and a predominant cause of fatalities in young Asian elephants. Rapid diagnosis and aggressive therapies have been determined to be a key strategy in the successful treatment of this disease. Herein, we have developed the immunochromatographic strip test for EEHV detection. Accordingly, 31.2 kDa of partial EEHV DNA polymerase (DNApol) protein was expressed in Escherichia coli and used to generate rabbit polyclonal anti-EEHV DNApol antibodies. These were then used to develop an ICS test for EEHV antigen detection using the double-antibody sandwich colloidal gold method. Anti-EEHV DNApol antibodies conjugated with 40 nm colloidal gold solution were used as a detector, while rabbit anti-EEHV DNApol and goat anti-rabbit IgG antibodies immobilized on the nitrocellulose membrane were used as the test and control lines, respectively. The test had a detection limit of 1.25 × 10⁵ viral genome copies (vgc)/mL of EEHV obtained from blood samples. Moreover, no specialized equipment or laboratory infrastructure was required in the administration of this test. This developed ICS test for EEHV antigen detection can be used in field application for the rapid detection of EEHV in resource-limited environments.

Lateral flow immunoassay for small-molecules detection in phytoproducts: a review

Phytoproducts are involved in various fields of industry. Small-molecule (Mw < 900 Da) organic compounds can be used to indicate the quality of plant samples in the perspective of efficacy by measuring the necessary secondary metabolites and in the perspective of safety by measuring the adulterant level of toxic compounds. The development of reliable detection methods for these compounds in such a complicated matrix is challenging. The lateral flow immunoassay (LFA) is one of the immunoassays well-known for its simplicity, portability, and rapidity. In this review, the general principle, components, format, and application of the LFA for phytoproducts are discussed.

Design of multiplexing lateral flow immunoassay for detection and typing of foot-and-mouth disease virus using pan-reactive and serotype-specific monoclonal antibodies: Evidence of a new hook effect

The foot-and-mouth disease (FMD) is the most important transboundary viral disease of livestock in the international context, because of its extreme contagiousness, widespread diffusion, and severe impact on animal trade and animal productions. The rapid and on-field detection of the virus responsible for the FMD represents an urgent demand to efficiently control the diffusion of the infection, especially in low resource setting where the FMD is endemic. Colorimetric lateral flow immunoassay (LFIA) is largely used for the development of rapid tests, due to the extreme simplicity, cost-effectiveness, and on-field operation. In this work, two multiplex LFIA devices were designed for the diagnosis of FMD and the simultaneous identification of major circulating serotypes of the FMD virus. The LFIAs relied on the sandwich-type immunoassay and combined a set of well-characterised monoclonal antibodies (mAb) pairs. One LFIA aimed at detecting and identifying O, A and Asia-1 serotypes, the second device enabled the detection and differentiation of the SAT 1 and SAT 2 serotypes. Both devices also incorporated a broad-specific test line reporting on infection from FMDV, regardless the strain and the serotype involved. Accordingly, five and four reactive zones were arranged in the two devices to achieve a total of six simultaneous analyses. The development of the two multiplex systems highlighted for the first time the relevance of the mAb positioning along the LFIA strip in connection with the use of the same or different mAb as capture and detector ligands. In fact, the excess of detector mAb typically employed for increasing the sensitivity of sandwich immunoassay induced a new type of hook effect when combined with the same ligand used as the capture. This effect strongly impacted assay sensitivity, which could be improved by an intelligent alignment of the mAb pairs along the LFIA strip. The analytical and diagnostic performances of the two LFIAs were studied by testing reference FMDV strains grown in cell cultures and some representative field samples (epithelium homogenates). Almost equivalent sensitivity and specificity to those of a reference Ag-ELISA kit were shown, except for the serotype SAT 2. These simple devices are suitable in endemic regions for in-field diagnosis of FMD accompanied by virus serotyping and, moreover, could be deployed and used for rapid confirmation of secondary outbreaks after FMD incursions in free-areas, thus contributing to promptly implement control measures.

A quantum dot fluorescent microsphere based immunochromatographic strip for detection of brucellosis

BACKGROUND

Brucellosis is a serious zoonosis disease that frequently causes significant economic loss in animal husbandry and threatens human health. Therefore, we established a rapid, accurate, simple and sensitive fluorescent immunochromatographic strip test (ICST) based on quantum dots (QDs) for detection the antibodies of Brucella infection animals serum.

RESULTS

The test strips were successfully prepared by quantum dot fluorescent microspheres (QDFM) as tracers, which were covalently coupled to an outer membrane protein of Brucella OMP22. The outer membrane protein OMP28 and monoclonal antibodies of OMP22 were separately dispensed onto a nitrocellulose membrane as test and quality control lines, respectively. The critical threshold for determining negative or positive through the ratio of the fluorescent signal of the test line and the control line (H_T / H_C) is 0.0492. The repeatability was excellent with an overall average CV of 8.78%. Under optimum conditions, the limit of detection was 1.05 ng/mL (1:512 dilution). With regard to the detection of brucellosis in 150 clinical samples, the total coincidence rate of ICST and Rose Bengal plate test (RBPT) was 97.3%, the coincidence rate of positive samples was 98.8%, the coincidence rate of negative samples was 95.3%, the sensitivity of RBPT is 1:32, and no cross reaction with the sera of other related diseases was observed.

CONCLUSION

In our present study, the QDFM has promising application for on-site screening of brucellosis owing to its high detection speed, high sensitivity, high specificity and low cost.

A multi-target lateral flow immunoassay enabling the specific and sensitive detection of total antibodies to SARS COV-2

A rapid test for detecting total immunoglobulins directed towards the nucleocapsid protein (N) of severe acute syndrome coronavirus 2 (SARS CoV-2) was developed, based on a multi-target lateral flow immunoassay comprising two test lines. Both test lines bound to several classes of immunoglobulins (G, M, and A). Specific anti-SARS immunoglobulins were revealed by a colorimetric probe formed by N and gold nanoparticles. Targeting the total antibodies response to infection enabled achieving 100% diagnostic specificity (95.75-100, C.I. 95%, n = 85 healthy and with other infections individuals) and 94.6% sensitivity (84.9-98.9, C.I. 95%, n = 62 SARS CoV-2 infected subjects) as early as 7 days post confirmation of positivity. Agreeing results with a reference serological ELISA were achieved, except for the earlier detection capability of the rapid test. Follow up of the three seroconverting patients endorsed the hypothesis of the random rise of the different immunoglobulins and strengthened the 'total antibodies' approach for the trustworthy detection of serological response to SARS CoV-2 infection.

Development of qualitative and quantitative immunochromatographic strip test assay for rapid and simple detection of leucomalachite green residual in aquatic animals

A rapid and simple immunochromatographic strip test assay based on competitive format was developed for leucomalachite green (LMG) detection. LMG-bovine serum albumin and rabbit anti-sheep IgG were immobilized on nitrocellulose membrane for the test line and control line, respectively. Anti-LMG-colloidal gold conjugate was immobilized onto the conjugate pad. For qualitative detection, the cut-off limit of the strip test was determined at 2 µg/L by the naked eye. For quantitative analysis, the working range of the LMG detection was 0.7-2 µg/L with LOD at 0.28 µg/L. A one-step immunochromatographic strip test for LMG detection can be completed within 5 min without any incubation, washing and blocking steps. Analysis results of LMG in aquatic animals obtained from the immunochromatographic strip test were in good agreement with those realized from enzyme-link immunosorbent assay. The developed the immunochromatographic strip test offered rapid detection as a simple (one-step), cost-effective, instrument-free assay and no need for handling reagents.

Development of a simple and rapid method for the detection of isomiroestrol in Pueraria candollei by an immunochromatographic strip test

Pueraria candollei (P. candollei) is a traditional Thai herb widely used for estrogen replacement therapy because it contains many unique chromenes that possess potent estrogenic activity, one of which is known as isomiroestrol. Since isomiroestrol is a promising compound that is solely present in P. candollei, it can be used as an identifying marker for standardization of P. candollei. Here, we developed a lateral-flow immunochromatographic strip (ICS) test using a colloidal gold nanoparticle-conjugated anti-isomiroestrol monoclonal antibody (12C1-mAb) for the detection of isomiroestrol in plant samples and products of P. candollei. The advantages of the developed ICS over an enzyme-linked immunosorbent assay are its simplicity and rapidity, as the ICS test can be completed 15 min after dipping the strip into the analyte solution. The detectable concentration of isomiroestrol was 7.0 µg/mL. Considering the demand for the standardization of P. candollei due to concerns regarding its quality, our ICS test using isomiroestrol as an identifying marker would be effective and useful to assess the presence of isomiroestrol.

Colour-encoded lateral flow immunoassay for the simultaneous detection of aflatoxin B1 and type-B fumonisins in a single Test line

A multiplex Lateral Flow Immunoassay was developed based on the use of a single Test line and multicolour gold nanoparticles (GNPs) as signal reporters. Red and blue GNPs were linked to antibodies directed towards two different analytes and included in a typical lateral flow immunoassay configuration, in which the Test line was formed by the mixture of two antigens. As a result of the immunoreactions occurring at the Test zone, diverse combinations of red and blue GNPs labels were captured. Therefore, the Test line assumed different colours depending on which - and how much - analyte is present in the sample. The multiplexing capability of the 'colour-encoded assay' is illustrated by the simultaneous detection of aflatoxin B1 (AFB1) and type-B fumonisins (FMs) in wheat and food products that made with wheat. Reproducible detection of AFB1 and FMs contamination in raw and processed food was achieved with visual cut-off levels at 1 ng mL^-1 and 50 ng mL^-1, respectively. The contaminant was identified based on the colour of the label according with a specific colour code. Furthermore, strips images were acquired by means of a common smartphone and analysed through RGB data analysis providing semi-quantitative detection of the two mycotoxins.

A fluorescent immunochromatographic strip test using a quantum dot-antibody probe for rapid and quantitative detection of 1-aminohydantoin in edible animal tissues

A rapid, simple, and sensitive fluorescent immunochromatographic strip test (ICST) based on quantum dots (QDs) has been developed to detect 1-aminohydantoin (AHD), a major metabolite of nitrofurantoin in animal tissues. To achieve this, QD-labeled antibody conjugates, which consist of CdSe/ZnS QDs and monoclonal antibodies, were prepared by an activated ester method. Under optimal conditions, with the nitrophenyl derivative of AHD as the target, the ICST had a linear range from 0.1 to 100 ng/mL, with a correlation coefficient of 0.9656 and a 50% inhibitory concentration of 4.51 ng/mL. The limit of detection was 0.14 ng/g, which was below the minimum required performance limit of 1 μg/kg for AHD established by the European Commission. The recoveries for AHD ranged from 81.5% to 108.2%, with coefficients of variation below 13%, based on intraday and interday analysis. Furthermore, for AHD in real samples, the ICST showed high reliability and high correlation with liquid chromatography-tandem mass spectrometry (correlation coefficient of 0.9916). To the best of our knowledge, this is the first report of a novel and sensitive method based on a fluorescent ICST to detect AHD below the minimum required performance limit. The ICST demonstrated high reliability, and could be ideally suited for rapid, simple, and on-site screening of AHD contamination in animal tissues. Graphical abstract A rapid, simple, and sensitive fluorescent immunochromatographic strip test that is based on quantum dots was developed to detect 1-aminohydantoin (AHD), a major metabolite of nitrofurantoin in animal tissues. 2-NBA 2-nitrobenzaldehyde, NP nitrophenyl.

A novel immunochromatographic system for easy-to-use detection of group 1 avian influenza viruses with acquired human-type receptor binding specificity

A switch of viral hemagglutinin receptor binding specificity from bird-type α2,3- to human-type α2,6-linked sialic acid is necessary for an avian influenza virus to become a pandemic virus. In this study, an easy-to-use strip test to detect receptor binding specificity of influenza virus was developed. A biotinylated anti-hemagglutinin antibody that bound a broad range of group 1 influenza A viruses and latex-conjugated α2,3 (blue) and α2,6 (red) sialylglycopolymers were used in an immunochromatographic strip test, with avidin and lectin immobilized on a nitrocellulose membrane at test and control lines, respectively. Accumulation of a sialylglycopolymer–virus–antibody complex at the test line was visualized by eye. The strip test could be completed in 30 min and did not require special equipment or skills, thereby avoiding some disadvantages of current methods for analyzing receptor binding specificity of influenza virus. The strip test could detect the receptor binding specificity of a wide range of influenza viruses, as well as small increases in the binding affinity of variant H5N1 viruses to α2,6 sialylglycans at viral titers >128 hemagglutination units. The strip test results were in agreement with those of ELISA virus binding assays, with correlations >0.95. In conclusion, the immunochromatographic strip test developed in this study should be useful for monitoring potential changes in the receptor binding specificity of group 1 influenza A viruses in the field.

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A novel immunochromatographic strip test system was developed.

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The strip test was developed to detect influenza virus receptor binding specificity.

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The strip test was applicable to a broad range of group 1 influenza A viruses.

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The strip detected faint increases in human-type specificity of variant H5N1 viruses.

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The system could be applied for easy monitoring the viral pandemic potential.

Immunological-based assays for specific detection of shrimp viruses

Among shrimp viral pathogens, white spot syndrome virus (WSSV) and yellow head virus (YHV) are the most lethal agents, causing serious problems for both the whiteleg shrimp, Penaeus (Litopenaeus) vannamei, and the black tiger shrimp, Penaeus (Penaeus) monodon. Another important virus that infects P. vannamei is infectious myonecrosis virus (IMNV), which induces the white discoloration of affected muscle. In the cases of taura syndrome virus and Penaeus stylirostris densovirus (PstDNV; formerly known as infectious hypodermal and hematopoietic necrosis virus), their impacts were greatly diminished after the introduction of tolerant stocks of P. vannamei. Less important viruses are Penaeus monodon densovirus (PmDNV; formerly called hepatopancreatic parvovirus), and Penaeus monodon nucleopolyhedrovirus (PemoNPV; previously called monodon baculovirus). For freshwater prawn, Macrobrachium rosenbergii nodavirus and extra small virus are considered important viral pathogens. Monoclonal antibodies (MAbs) specific to the shrimp viruses described above have been generated and used as an alternative tool in various immunoassays such as enzyme-linked immunosorbent assay, dot blotting, Western blotting and immunohistochemistry. Some of these MAbs were further developed into immunochromatographic strip tests for the detection of WSSV, YHV, IMNV and PemoNPV and into a dual strip test for the simultaneous detection of WSSV/YHV. The strip test has the advantages of speed, as the result can be obtained within 15 min, and simplicity, as laboratory equipment and specialized skills are not required. Therefore, strip tests can be used by shrimp farmers for the pond-side monitoring of viral infection.