A simple and rapid immunochromatographic strip test for detecting antibody to porcine reproductive and respiratory syndrome virus

Evaluation of sperm quality and male fertility: The use of molecular markers in boar sperm and seminal plasma

In pig production, the optimization of artificial insemination (AI) efficiency significantly relies on the accurate assessment of semen quality and fertility of boars. Traditional methods such as conventional seminogram techniques, although long-standing, exhibit limited sensitivity in predicting boar fertility, warranting the exploration of novel molecular markers. This review synthesizes the current knowledge on the utilization of molecular markers for semen quality evaluation and male fertility prediction in boars, providing an in-depth examination of molecular markers in this context. Specifically, the present work delves into the potential of OMICs technologies, encompassing genetic and genomic approaches, transcriptomics, proteomics, and metabolomics. A diverse array of molecular markers, including genomic regions associated with sperm quality and male fertility, chromatin integrity, mitochondrial DNA content, mRNA and non-coding RNA signatures, as well as proteins and metabolites in sperm and seminal plasma, are identified as promising molecular markers for fertility prediction in boars. Furthermore, the need of validating biomarkers and their practical implementation in AI centres is here emphasized. Addressing these considerations and integrating molecular markers within the swine breeding field holds the potential to enhance reproductive management practices and optimize productivity in boar breeding programs. This integration can significantly improve overall efficiency within the pig breeding industry.

Point-of-Care Diagnostics for Farm Animal Diseases: From Biosensors to Integrated Lab-on-Chip Devices

Zoonoses and animal diseases threaten human health and livestock biosecurity and productivity. Currently, laboratory confirmation of animal disease outbreaks requires centralized laboratories and trained personnel; it is expensive and time-consuming, and it often does not coincide with the onset or progress of diseases. Point-of-care (POC) diagnostics are rapid, simple, and cost-effective devices and tests, that can be directly applied on field for the detection of animal pathogens. The development of POC diagnostics for use in human medicine has displayed remarkable progress. Nevertheless, animal POC testing has not yet unfolded its full potential. POC devices and tests for animal diseases face many challenges, such as insufficient validation, simplicity, and portability. Emerging technologies and advanced materials are expected to overcome some of these challenges and could popularize animal POC testing. This review aims to: (i) present the main concepts and formats of POC devices and tests, such as lateral flow assays and lab-on-chip devices; (ii) summarize the mode of operation and recent advances in biosensor and POC devices for the detection of farm animal diseases; (iii) present some of the regulatory aspects of POC commercialization in the EU, USA, and Japan; and (iv) summarize the challenges and future perspectives of animal POC testing.

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.

A quantum dot-based lateral flow immunoassay for the rapid, quantitative, and sensitive detection of specific IgE for mite allergens in sera from patients with allergic rhinitis

The prevalence of allergic rhinitis (AR) is increasing worldwide. However, the current systems used to measure levels of immunoglobulin E (IgE) in sera are associated with several disadvantages that limit their further application. Consequently, there is a need to develop novel highly sensitive strategies that can rapidly detect IgE in a quantitative manner. The development of such systems will significantly enhance our ability to diagnose, treat, and even prevent AR. Herein, we describe our experience of using quantum dot-based lateral flow immunoassay (QD-LFIA), combined with a portable fluorescence immunoassay chip detector (PFICD), to detect serum-specific IgE against Dermatophagoides pteronyssinus (Der-p) and Dermatophagoides farinae (Der-f), two common mite allergens in China. Our data showed that our system could detect serum-specific levels of IgE against Der-p and Der-f as low as 0.093 IU/mL and 0.087 IU/mL, respectively. We also established a standard curve to determine serum-specific IgE concentrations that correlated well with the clinical BioIC microfluidics system. The sensitivity of our assay was 96.7% for Der-p and 95.5% for Der-f, while the specificity was 87.2% for Der-p and 85.3% for Der-f. Collectively, our results demonstrate that QD-LFIA is a reliable system that could be applied to detect serum-specific IgE in accordance with clinical demands. This QD-LFIA strategy can be applied at home, in hospitals, and in pharmacies, with reduced costs and time requirements when compared with existing techniques. In the future, this system could be developed to detect other types of allergens and in different types of samples (for example, whole blood).

Graphical abstract

Nanomaterials and nanocomposite applications in veterinary medicine

Nowadays, nanotechnology has made huge, significant advancements in biotechnology and biomedicine related to human and animal science, including increasing health safety, production, and the elevation of national income. There are various fields of nanomaterial applications in veterinary medicine such as efficient diagnostic and therapeutic tools, drug delivery, animal nutrition, breeding and reproduction, and valuable additives. Additional benefits include the detection of pathogens, protein, biological molecules, antimicrobial agents, feeding additives, nutrient delivery, and reproductive aids. There are many nanomaterials and nanocomposites that can be used in nanomedicine such as metal nanoparticles, liposomes, carbon nanotubes, and quantum dots. In the near future, nanotechnology research will have the ability to produce novel tools for improving animal health and production. Therefore, this chapter was undertaken to spotlight novel methods created by nanotechnology for application in the improvement of animal health and production. In addition, the toxicity of nanomaterials is fully discussed to avoid the suspected health hazards of toxicity for animal health safety.

Simultaneous detection of classical PRRSV, highly pathogenic PRRSV and NADC30-like PRRSV by TaqMan probe real-time PCR

Porcine Reproductive and Respiratory Syndrome (PRRS), an acute infectious disease caused by the porcine reproductive and respiratory syndrome virus (PRRSV), is one of the most devastating diseases affecting the global swine industry. In order to establish a multiplex real-time PCR method for the simultaneous detection of the classical PRRSV (C-PRRSV) strain, the highly pathogenic PRRSV (HP-PRRSV) strain and NADC30-like PRRSV (NL-PRRSV) strain, we designed specific primers and TaqMan fluorescent probes based on the Nsp2 target gene sequence of these three different PRRSV strains, and designed American-type PRRSV (PRRSV-U) special primers and probes based on the relatively conserved target gene sequence of ORF7. The method established in this study can quickly and accurately detect and differentiate three types of strains of clinical tissue samples, respectively. This method plays a key role in the rapid diagnosis and determination of PRRSV.

An enhanced immunochromatographic strip test using colloidal gold nanoparticle-labeled dual-type N proteins for detection of antibodies to PRRS virus

Porcine reproductive and respiratory syndrome (PRRS) is recognized as one of the most important infectious diseases causing serious economic loss in the swine industry worldwide. Due to its increasing genetic diversity, a rapid and accurate diagnosis is critical for PRRS control. The immunochromatographic strip test (ICST) is a rapid and convenient type of immunoassay. In this study, an on-site immunochromatographic assay-based diagnostic method was developed for detection of PRRS virus (PRRSV)-specific antibodies. The method utilized colloidal gold nanoparticle-labeled dual-type nucleocapsid proteins encoded by open reading frame 7. We evaluated 991 field samples from pig farms and 66 serum samples from experimentally PRRSV-inoculated pigs. Based on true PRRSV-specific antibody-positive or -negative sera determined by immunofluorescence assay and IgM enzyme-linked immunosorbent assay (ELISA), the specificity and sensitivity of the ICST were 97.5% and 91.1%, respectively, similar to those of a commercial ELISA (IDEXX PRRS X3 Ab). More importantly, the ICST was completed within 15 min and could detect the PRRSV-specific antibody at an earlier stage of infection (3-7 days) than that of ELISA (7+ days). The results demonstrate that the developed ICST has great potential as an on-farm diagnostic method, providing excellent diagnostic performance in a quick and convenient manner.

Development of an immunochromatographic strip for detection of antibodies against porcine reproductive and respiratory syndrome virus

A simple and rapid immunochromatographic test strip incorporating a colloidal gold-labeled recombinant Nsp7 antigen probe was successfully developed for the detection of anti-porcine reproductive and respiratory syndrome virus (PRRSV) antibodies in swine. Recombinant Nsp7 protein of PRRSV labeled with colloidal gold was dispensed on a conjugate pad for use as the detector. Staphylococcal protein A and purified porcine anti-Nsp7 antibodies were blotted on a nitrocellulose membrane to form test and control lines, respectively. A comparison of the strip with standard diagnostic tests, enzyme-linked immunosorbent assays and immunoperoxidase monolayer assay, was also performed. The immunochromatographic test strip was shown to be of high specificity and sensitivity. Furthermore, the strip assay is rapid and easy to perform with no requirement for professional-level skills or equipment. It is suggested that the immunochromatographic test strip can be used to quickly and accurately detect PRRSV antibody and to be suitable for diagnostic purposes in the field.

Opportunities and challenges for the application of microfluidic technologies in point-of-care veterinary diagnostics

There is a growing need for low-cost, rapid and reliable diagnostic results in veterinary medicine. Point-of-care (POC) tests have tremendous advantages over existing laboratory-based tests, due to their intrinsic low-cost and rapidity. A considerable number of POC tests are presently available, mostly in dipstick or lateral flow formats, allowing cost-effective and decentralised diagnosis of a wide range of infectious diseases and public health related threats. Although, extremely useful, these tests come with some limitations. Recent advances in the field of microfluidics have brought about new and exciting opportunities for human health diagnostics, and there is now great potential for these new technologies to be applied in the field of veterinary diagnostics. This review appraises currently available POC tests in veterinary medicine, taking into consideration their usefulness and limitations, whilst exploring possible applications for new and emerging technologies, in order to widen and improve the range of POC tests available.

Development and clinical evaluation of a new gold-immunochromatographic assay for the detection of antibodies against field strains of pseudorabies virus

An immunochromatographic strip (ICS) was developed for the detection of swine antibodies against glycoprotein E (gE) in Pseudorabies Virus (PRV). In this test, Staphylococcal Protein A (SPA) labeled with colloidal gold was dispensed on a conjugate pad as the detector. Purified PRV-gE and pig-IgG were blotted on a nitrocellulose membrane for the test (T) and control lines (C), respectively. If the tested serum contains IgG antibodies against PRV-gE, the IgG will interact with the colloidal gold-SPA to form a complex (gold-SPA-swine IgG). The complex will react with the immobilized PRV-gE on the T line and the Pig-IgG in the C line of the ICS to form two visible red bands. If there is no IgG antibody against PRV-gE in the sample serum, only the C line will be visible. The ICS was capable of specifically detecting PRV-gE antibody within 5 min, and its stability and reproducibility were quite good after storage at 4°C and use within 4 months. Using an IDEXX Pseudorabies Virus gE Antibody Test Kit (IDEXX PRV gE Ab test) as a reference, the relative specificity and sensitivity of the ICS were determined to be 81.6% and 90.7%, respectively. Furthermore, there was a good agreement between the results obtained by the commercial product and the ICS (kappa=0.7289).

Use of recombinant nucleocapsid proteins for serological diagnosis of feline coronavirus infection by three immunochromatographic tests

Three types of immunochromatographic assays (ICAs) were designed to detect anti-feline coronavirus (FCoV) antibodies. Recombinant FCoV nucleocapsid protein (rNP) was used as a conjugate or test line in all 3 ICA kits (_CJIgG/_TNP, _CJNP/_TNP, and _CJNP/_TPA). All three ICA kits were capable of detecting anti-FCoV antibodies; however, non-specific positive reactions of anti-FCoV antibody-negative plasma samples with the test line were observed in 2 ICA kits (_CJIgG/_TNP and _CJNP/_TNP), in which rNP was used as the test line. On the other hand, the specific detection of anti-FCoV antibodies was possible in all plasma, serum, whole blood, and ascitic fluid samples using the ICA kit with protein A blotted as the test line (_CJNP/_TPA). In addition, the specificity and sensitivity of ICA (_CJNP/_TPA) were equivalent to those of the reference ELISA. The development of simple antibody test methods using the principle of ICA (_CJNP/_TPA) for other coronavirus and feline viral infections is expected in the future.

A one-step RT-PCR assay to detect and discriminate porcine reproductive and respiratory syndrome viruses in clinical specimens

Outbreaks of highly pathogenic porcine reproductive and respiratory syndrome virus (HP-PRRSV) have led to large economic losses and, subsequently, have drawn great attention to its diagnosis and prevention. To facilitate rapid discrimination of HP-PRRSV from classical PRRSV (C-PRRSV), we developed a one-step RT-PCR assay. Primer specificities were evaluated with RNA extracted from 8 viral strains and our results revealed that the primers had a high specificity for PRRSV. The assay sensitivity was 25 copies/μL for both HP-PRRSV and C-PRRSV. A total of 929 serum samples were identified, of which 20.45% were HP-PRRSV-positive and 1.51% were C-PRRSV-positive, which was completely consistent with that of immunochromatochemistry and sequencing method. The proposed assay can detect the virus 2 days prior the onset of symptoms and it can be performed in 2h, thereby providing a rapid method to discriminate HP-PRRSV from C-PRRSV for the identification and prevention of PRRSV infections.

Comparison of the lateral flow immunoassays (LFIA) for the diagnosis of Helicobacter pylori infection

Helicobacter pylori infection is the most common human infection where approximately 50% of the world populations are infected. The diagnosis of such infection is mainly done by endoscopy where gastric biopsies are examined for the presence of H. pylori. Such invasive approach is costly, time consuming and generally requires more than one test to confirm the infection. Serology on the other hand is a non-invasive approach that can detect H. pylori exposure. The lateral flow immunoassays (LFIA) support the serological approach and have the advantage of being fast, economic and require no additional equipment or experience. In this review the principles, components of the LFIA, sensitivities and specificities of the commercially available H. pylori test strips were compared and discussed.

Study of Colloidal Gold Strip in Detecting the Antibody of Porcine Epidemic Diarrhea

Porcine Epidemic Diarrhea Virus (PEDV) infection has caused huge economic losses, but no serological method is available for batch detection of field samples. The aim of the study was to develop a method for large-batch detection of PEDV infection. Colloidal gold-labeled staphylococcal protein A (SPA) was sprayed on glass fibers to prepare a conjugate pad. The recombinant N protein of PEDV was blotted on the test line of the nitrocellulose (NC) membrane, and pig IgG was streaked on the control line of the NC membrane. The immunochromatographic strip was used for detection of antibodies against PEDV. The results showed that the strip test was simple and the results could be determined within 10 min with naked eyes. The test strip was highly specific for pig serum against PEDV and no cross-reaction was observed. The test strip had close similarity with ELISA. Storage at room temperature for 6 months did not affect the specificity and sensitivity obviously. A total of 320 clinical pig sera were detected by both ELISA and the developed test strip, and the coincidence was 96.3 %. Therefore, the developed immunochromatographic strip is specific, sensitive, stable, fast and simple, and it is suitable for on-site detection of antibodies against PEDV.

Development of an immunochromatographic strip for the detection of antibodies against Porcine circovirus-2

A rapid (<5 min) immunochromatographic strip using a colloidal gold–labeled antigen probe was successfully developed and applied for the detection of Porcine circovirus-2 (PCV-2) antibodies in swine. Recombinant Cap protein truncated nuclear localization signal of PCV-2, was expressed and labeled with colloidal gold. This conjugate was dispensed on a conjugate pad as the detector. Staphylococcal protein A and purified porcine anti–PCV-2 antibodies were blotted on a nitrocellulose membrane for the test and control lines, respectively. Sensitivity and specificity of this strip test was evaluated using PCV-2 antisera as well as other sera from pigs infected with a variety of swine viruses. For the validation of this strip test, 500 clinical swine serum samples were assessed both by the strip and a commercial enzyme-linked immunosorbent assay (ELISA) kit. The agreement between the immunochromatographic strip and ELISA kit was 94.00%. This strip possesses high sensitivity and specificity and may be useful as a candidate for rapid diagnosis of PCV-2 antibodies in the field.

Development and evaluation of an immunochromatographic strip test based on the recombinant UL51 protein for detecting antibody against duck enteritis virus

Background

Duck enteritis virus (DEV) infection causes substantial economic losses to the worldwide duck-producing areas. The monitoring of DEV-specific antibodies is a key to evaluate the effect of DEV vaccine and develop rational immunization programs. Thus, in this study, an immunochromatographic strip (ICS) test was developed for detecting DEV serum antibodies.

Results

The ICS test is based on membrane chromatography, and uses both the purified recombinant UL51 protein conjugated with colloidal gold and goat anti-rabbit IgG conjugated with colloidal gold as tracers, the purified recombinant UL51 protein as the capture reagent at the test line, and rabbit IgG as the capture reagent at the control line. The specificity of the ICS was evaluated by sera against DEV, Duck hepatitis virus (DHV), Riemerella anatipestifer (RA), Duck E. coli, Muscovy duck parvovirus (MPV), or Duck Influenza viruses (DIV). Only sera against DEV showed the strong positive results. In order to determine the sensitivity of the ICS, anti-DEV serum diluted serially was tested, and the minimum detection limit of 1:128 was obtained. The ICS components, which are provided in a sealed package, require no refrigeration and are stable for 12 months. To evaluate the effect of the ICS, 110 duck serum samples collected from several non-immune duck flocks were simultaneously tested by the ICS test, enzyme-linked immunosorbent assay (ELISA) and neutralization test (NT). The results showed that the sensitivity of the ICS test was almost consistent with ELISA and much higher than NT, has low cost, and is rapid (15 min) and easy to perform with no requirement of specialized equipment, reagent or technicians.

Conclusions

In this work, we successfully developed a simple and rapid ICS test for detecting DEV serum antibodies for the first time. The ICS test was high specific and sensitive for the rapid detection of anti-DEV antibodies, and has great potential to be used for the serological surveillance of DEV infection in the field.

A rapid immunochromatographic test strip for detecting rabies virus antibody

An immunochromatographic test strip (ICTS) for detecting antibodies to rabies virus was developed, using colloidal gold particles labeled with rabies virus glycoprotein as the tracer. The assay was evaluated using sera from dogs immunized with various commercial rabies vaccines, or from dogs in the clinics and sera from dogs immunized with vaccines against pathogens other than rabies virus, and negative sera from a wide variety of animal sources, including dogs, mice, and cats which had never been vaccinated. The ICTS was found to be highly specific for antibodies against rabies virus, with a detection limit of 0.5IU/ml as measured by the fluorescent antibody virus neutralization (FAVN) test. Compared with the FAVN test, the specificity and sensitivity of ICTS were 98.2% and 90.4%, respectively. There was an excellent agreement between results obtained by the ICTS and FAVN tests (kappa=0.888). Strips stored at 4°C in a plastic bag with a desiccant retained their specificity and sensitivity for at least 15 months, and strips stored at ambient temperature remained stable for 12 months. The immunochromatographic test strip may therefore be useful for clinical laboratories lacking specialized equipment and for diagnosis in the field for rapid detection of rabies virus-specific antibodies.

Development and application of lateral flow test strip technology for detection of infectious agents and chemical contaminants: a review

Recent progress in the laboratory has been a result of improvements in rapid analytical techniques. An update of the applications of lateral flow tests (also called immunochromatographic assay or test strip) is presented in this review manuscript. We emphasized the description of this technology in the detection of a variety of biological agents and chemical contaminants (e.g. veterinary drugs, toxins and pesticides). It includes outstanding data, such as sample treatment, sensitivity, specificity, accuracy and reproducibility. Lateral flow tests provide advantages in simplicity and rapidity when compared to the conventional detection methods.

Development of an immunochromatographic strip for the detection of antibodies against foot-and-mouth disease virus serotype O

An immunochromatographic strip was developed for the serological detection of type O foot-and-mouth disease (FMD) in swine. In the strip, the expressed protein of VP1, the main protective antigen of FMDV, labeled with colloidal gold was used as the detector, the staphylococcal protein A (SPA) and swine anti-foot-and-mouth disease virus (FMDV) antibody were blotted on the nitrocellulose membrane for the test and control lines, respectively. 296 swine serum samples were collected to evaluate the characteristics of the strip in comparison with existing commercial liquid-phage blocking ELISA (LPB ELISA) kit and peptide ELISA kit. The strip was shown to be of high specificity and sensitivity. Furthermore, the dipstick assay based on the strip is rapid (5 min) and easy to perform with no requirement of professional skills, reagents nor equipment. This suggests that the immunochromatographic strip is an acceptable alternative for use in clinical laboratories lacking specialized equipment and for field diagnosis.

Development and validation of an immunogold chromatographic test for on-farm detection of PRRSV

An immunochromatographic test strip was developed to detect porcine reproductive and respiratory syndrome virus (PRRSV). The test uses two gold-labeled monoclonal antibodies: D5 against recombinant nucleocapsid protein (rN) and E9 against recombinant M protein (rM). In the test, PRRSV binds to a mixture of D5 and E9 labeled with colloidal gold; the complexes move through a membrane and are captured by rabbit anti-rM and anti-rN antibodies at a test line, producing a reddish-purple band because of the increased concentration of gold. Unbound monoclonal antibodies move past the test line to be captured by goat anti-mouse antibodies, producing a band at a control line. In samples without PRRSV or with low virus concentration, a band appears only at the control line. A crossover-trial demonstrated that the test strip was highly specific for PRRSV. The test strip detection limit was between 7.8x10(3) and 1.6x10(4) TCID(50)/ml. Analysis of 100 clinical samples indicated that the sensitivity, specificity, and accuracy of the immunochromatographic test strip relative to reverse transcription polymerase chain reaction (RT-PCR) were 97.0, 93.9, and 96.0%, respectively. Because the test is simple and rapid, it can be used by an unskilled person to detect PRRSV in the field.