Development and Evaluation of an Immunochromatographic Strip for Detection of Streptococcus Suis Type 2 Antibody

Development and evaluation of a colloidal gold immunochromatographic assay based on recombinant protein CatL1D for serodiagnosis of sheep fasciolosis

Fasciolosis is a zoonotic parasitic disease that seriously endangers the development of animal husbandry and human health. In order to develop a rapid serological diagnostic method for fasciolosis in ruminants, the CatL1D and CatB4 genes of Fasciola hepatica were amplified by reverse transcription polymerase chain reaction (PCR) and cloned, respectively, and then the CatL-B fusion gene (MeCatL-B) was constructed by gene splicing by overlap extension PCR technique. The recombinant rCatL1D, rCatB4 and rMeCatL-B proteins were then prepared by prokaryotic expression, respectively, and the recombinant protein with high specificity and sensitivity was screened via indirect enzyme-linked immunosorbent assay. Using the selected recombinant protein rCatL1D as a diagnostic antigen, we developed a colloidal gold immunochromatographic assay (CGIA) for detecting F. hepatica-specific antibodies, and 426 serum samples of slaughtered sheep were used to evaluate the sensitivity and specificity of F. hepatica CGIA assay. The results showed that the sensitivity and specificity of rCatL1D protein (100%, 96.67%) were higher than those of rCatB4 (94.29%, 80%) and rMeCatL-B (91.43%, 90%). Compared with the gold standard post-mortem inspection, the specificity and sensitivity of the CGIA method was 100% and 97%, respectively, and the consistency rate between these two methods was 99.3%. These results confirmed that the CGIA method based on rCatL1D protein could be a promising approach for rapid diagnosis of sheep fasciolosis because of its high sensitivity and specificity.

Methods for the detection and characterization of Streptococcus suis: from conventional bacterial culture methods to immunosensors

One of the most important zoonotic pathogens worldwide, Streptococcus suis is a swine pathogen that is responsible for meningitis, toxic shock and even death in humans. S. suis infection develops rapidly with nonspecific clinical symptoms in the early stages and a high fatality rate. Recently, much attention has been paid to the high prevalence of S. suis as well as the increasing incidence and its epidemic characteristics. As laboratory-acquired infections of S. suis can occur and it is dangerous to public health security, timely and early diagnosis has become key to controlling S. suis prevalence. Here, the techniques that have been used for the detection, typing and characterization of S. suis are reviewed and the prospects for future detection methods for this bacterium are also discussed.

A new immunoassay of serum antibodies against Peste des petits ruminants virus using quantum dots and a lateral-flow test strip

A fast and ultrasensitive test-strip system combining quantum dots (QDs) with a lateral-flow immunoassay strip (LFIAS) was established for detection of Peste des petits ruminants virus (PPRV) antibody. The highly luminescent water-soluble carboxyl-functionalized QDs were used as the signal output and were conjugated to streptococcal protein G (SPG), which was capable of binding to immunoglobulin G (IgG) from many species through an amide bond to capture the target PPRV IgGs. The PPRV N protein, which was immobilized on the detection zone of the test strip, was expressed by transfecting recombinant Bacmid-PPRV-N with Lipofect into Sf9 insect cells. When exposed to PPRV IgG, QD-SPG bound to PPRV N protein, resulting in the formation of a complex that subsequently produced a bright fluorescent band in response to 365 nm ultraviolet excitation. Sensitivity evaluation showed that the QD-LFIAS limit of detection (LOD) for PPRV antibody was superior to competitive enzyme-linked immunosorbent assay (c-ELISA) and the immunochromatographic strip. No cross reaction was observed when the positive sera of bluetongue virus, canine distemper virus, goat pox virus, and foot-and-mouth disease virus were tested. Further evaluation using field samples indicated that the diagnostic specificity and sensitivity of the QD-LFIAS was 99.47 and 97.67 %, respectively, with excellent agreement between QD-LFIAS and c-ELISA. The simple analysis step and objective results that can be obtained within 15 min indicate that this new method shows great promise for rapid, sensitive detection of PPRV IgG for onsite, point-of-care diagnosis and post vaccination evaluation (PVE). Graphical Abstract Ultrasensitive fluorescent QD immunochromotography in combination with recombinant PPRV N protein could be used to detect PPRV antibody in serum.

Rapid detection of Enterobacter cloacae by immunomagnetic separation and a colloidal gold-based immunochromatographic assay

This is the first study of detection of Enterobacter cloacae via combined immunomagnetic separation and a colloidal gold-based immunochromatographic assay.

Streptococcus suis infection: an emerging/reemerging challenge of bacterial infectious diseases?

Streptococcus suis (S. suis) is a family of pathogenic gram-positive bacterial strains that represents a primary health problem in the swine industry worldwide. S. suis is also an emerging zoonotic pathogen that causes severe human infections clinically featuring with varied diseases/syndromes (such as meningitis, septicemia, and arthritis). Over the past few decades, continued efforts have made significant progress toward better understanding this zoonotic infectious entity, contributing in part to the elucidation of the molecular mechanism underlying its high pathogenicity. This review is aimed at presenting an updated overview of this pathogen from the perspective of molecular epidemiology, clinical diagnosis and typing, virulence mechanism, and protective antigens contributing to its zoonosis.

Prevalência de Streptococcus suis sorotipo 2: discussão da literatura brasileira

Streptococcus suis é mundialmente considerado um dos patógenos de maior impacto sanitário e econômico na indústria suinícola. Dentre os sorotipos descritos como zoonóticos, o sorotipo 2 é o mais frequentemente isolado de animais e humanos doentes na maioria dos países. O estudo da epidemiologia das infecções por S. suis no Brasil é importante para a implantação de medidas efetivas de controle. O objetivo do presente trabalho foi realizar uma revisão crítica da literatura brasileira, com suporte da literatura mundial, abordando o diagnóstico do agente e sua prevalência em animais clinicamente doentes e portadores sadios, com destaque para a prevalência do sorotipo 2 no país.

Development and preliminary application of an immunochromatographic strip for rapid detection of infection with porcine reproductive and respiratory syndrome virus in swine

A "strip test" to detect porcine reproductive and respiratory syndrome virus (PRRSV) was established using a monoclonal antibody (MAb) 2D7 conjugated with colloidal gold. Two MAbs binding to protein N at different epitopes, 2D7 and 1G7 were obtained. In the test, samples of PRRSV bound to colloidal gold-conjugated MAb 2D7. The complex was then captured by MAb 1G7 at the test line (T) on the nitrocellulose membrane, presenting a purple band. If the sample did not contain PRRSV or if the quantity of PRRSV was less than that required for the kit, only the control line (C), in which goat anti-mouse antibody was added as the capture antibody, was present. Results from the sensitivity test of the kit demonstrated that the lowest detected quantity of PRRSV is 2.9 × 10(3)TCID(50)/ml. In clinical trials, the specificity and the sensitivity of this kit are 98.1% and 88.4%, respectively, compared with RT-PCR. Furthermore, this kit was found to be efficient in three areas of China and appears to have better results in practical applications than in empirical studies. In summary, this kit has not only high rates of specificity and sensitivity but also has the beneficial features such as efficiency, convenience and speed.

A rapid assay for detecting antibody against Bluetongue virus with a latex agglutination test using recombinant VP7 antigen

A latex agglutination test (LAT) for detecting antibody against Bluetongue virus (BTV) in ruminants was developed using latex beads coupled with recombinant VP7 protein. Compared with competitive enzyme-linked immunosorbent assay (ELISA), the specificity and sensitivity of the LAT were 99.0% and 93.0%, respectively. There was excellent agreement between the results obtained by competitive ELISA and the LAT (kappa = 0.930). Because it is rapid and easy to use, the LAT could be used for BTV antibody detection, especially for screening many serum samples.

Development of a convenient immunochromatographic strip for the diagnosis of infection with Japanese encephalitis virus in swine

Japanese encephalitis (JE) is caused by the Japanese encephalitis virus (JEV). It is a major public health problem in Asia. JEV infects swine which results in fatal encephalitis, abortion and stillbirth in pregnant sow, and hypospermia in boars. Swine is a viral amplifier, and thus plays a critical role in JEV transmission. Thus, development of a rapid method for JEV detection in swine is required for clinical JE diagnosis, as well as to suppress viral spread. In this study, a convenient and rapid immunochromatographic strip (ICS) was developed for detecting JEV in swine using two monoclonal antibodies (MAbs) (2A2 and 4D1) against the E protein of JEV. Results showed that colloidal gold-conjugated MAbs 2A2 (CG-MAb) bond with JEV and the resulting complex was held by the other MAb 4D1 at the test line to give a reddish-purple band. Sensitivity tests demonstrated that ICS can detect 2.5x10(5)PFU of JEV. The clinical screening results showed that the specificity and sensitivity of the ICS were 99.3% and 85.7% respectively as compared to that of RT-PCR. This suggests that the MAbs-based ICS test can be used as a convenient method for the rapid detection of JEV in infected swine samples.

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 and evaluation of an immunochromatographic strip for the detection of serum antibodies against bluetongue virus

In this study, an immunochromatographic strip (ICS) was developed for the detection of bluetongue virus (BTV) serum antibodies. Colloidal gold particles labeled with streptococcal protein G (SPG), which can bind to the F(C) fragment of mammalian immunoglobulins, were used as the detector reagent. A recombinant VP7 BTV protein and a purified rabbit anti-SPG antibody were immobilized on test and control regions of a nitrocellulose membrane, respectively. In order to evaluate the ICS, 37 sera from animals exposed to different BTV serotypes were used as positive controls. In addition, 50 positive sera against viruses other than BTV, and eight sera taken from naive healthy sheep were used to determine the specificity of the ICS. Three hundred and three field sera taken from sheep and cattle were used after the above sera had been used for validation. Compared with the competitive ELISA (c-ELISA), the specificity and sensitivity of the ICS was 97.6% and 100%, respectively. There was excellent agreement between the results obtained by c-ELISA and the ICS (kappa=0.930). As it is rapid and easy to use, the test is suitable for the serological surveillance of BTV infection in the field.