Visual typing detection of brucellosis with a lateral flow immunoassay based on coloured latex microspheres

Novel Vertical Flow Immunoassay with Au@PtNPs for Rapid, Ultrasensitive, and On-Site Diagnosis of Human Brucellosis

Brucellosis is an infectious zoonosis caused by Brucella with clinical symptoms of wavy fever, fatigue, and even invasion of tissues and organs in the whole body, posing a serious threat to public health around the world. Herein, a novel vertical flow immunoassay based on Au@Pt nanoparticles (Au@PtNPs-VFIA) was established for detection of Brucella IgG antibody in clinical serum samples. The testing card of Au@PtNPs-VFIA was manufactured by printing the purified Brucella LPS and goat antimouse IgG on the nitrocellulose membrane as the test-spot or control-spot, respectively. Au@PtNPs labeled with protein G (Au@PtNPs-prG) were concurrently employed as detection probes presenting visible spots and catalysts mimicking catalytic enzymes to catalyze the DAB substrate (H2O2 plus O-phenylenediamine) for deepening color development. The testing procedure of Au@PtNPs-VFIA takes 2-3 min, and the limit of detection (LOD) for Brucella antibody is 0.1 IU/mL, which is faster and more sensitive than that of Au@PtNP-based lateral flow immunoassay (Au@PtNPs-LFIA: 15 min and 1.56 IU/mL, respectively). By comparing with vertical flow immunoassay based on classic Au nanoparticles (AuNPs-VFIA), the Au@PtNPs-VFIA is 32 times or 16 times more sensitive with or without further development of DAB substrate catalysis. Au@PtNPs-VFIA did not react with the serum samples of Gram-negative bacterium infections but only weakly cross-reacted with diagnostic serum of Y. enterocolitica O9 infection. In detection of clinical samples, Au@PtNPs-VFIA was validated for possessing 98.33% sensitivity, 100% specificity, and 99.17% accuracy, which were comparable with or even better than those obtained by the Rose-Bengal plate agglutination test, serological agglutination test, AuNPs-VFIA, and Au@PtNPs-LFIA. Therefore, this newly developed Au@PtNPs-VFIA has potential for rapid, ultrasensitive, and on-site diagnosis of human Brucellosis in clinics.

Latest Trends in Lateral Flow Immunoassay (LFIA) Detection Labels and Conjugation Process

LFIA is one of the most successful analytical methods for various target molecules detection. As a recent example, LFIA tests have played an important role in mitigating the effects of the global pandemic with SARS-COV-2, due to their ability to rapidly detect infected individuals and stop further spreading of the virus. For this reason, researchers around the world have done tremendous efforts to improve their sensibility and specificity. The development of LFIA has many sensitive steps, but some of the most important ones are choosing the proper labeling probes, the functionalization method and the conjugation process. There are a series of labeling probes described in the specialized literature, such as gold nanoparticles (GNP), latex particles (LP), magnetic nanoparticles (MNP), quantum dots (QDs) and more recently carbon, silica and europium nanoparticles. The current review aims to present some of the most recent and promising methods for the functionalization of the labeling probes and the conjugation with biomolecules, such as antibodies and antigens. The last chapter is dedicated to a selection of conjugation protocols, applicable to various types of nanoparticles (GNPs, QDs, magnetic nanoparticles, carbon nanoparticles, silica and europium nanoparticles).

A Novel Immunochromatographic Strip Based on Latex Microspheres for the Rapid Detection of North American-Type Porcine Reproductive and Respiratory Syndrome Virus

A latex microsphere-based immunochromatographic strip (ICS) test was successfully developed for the rapid and sensitive detection of porcine reproductive and respiratory syndrome virus (PRRSV). The PRRSV N protein-specific monoclonal antibody (mAb) 1H4 labeled with latex microspheres was dispensed on a conjugate pad for use as the detector. The same mAb and goat anti-mouse antibody were blotted on a nitrocellulose membrane to generate test and control lines, respectively. The limit of virus detection was approximately 5 × 10^2.0 median tissue culture infectious dose (TCID₅₀)/ml, and the limit of N protein detection was approximately 15 ng/ml. Other common porcine viruses were tested to evaluate the specificity of the ICS, and positive results were observed for only North American-type PRRSV. A comparison of the strip with a standard diagnostic test (reverse transcriptase polymerase chain reaction, RT-PCR) was also performed, and the results showed that the ICS test exhibited relatively high specificity and sensitivity (90.32 and 73.91%, respectively) and relatively high positive predictive value (PPV) and negative predictive value (NPV; 85 and 82.35%, respectively). These results suggest that the ICS test can be used to rapidly and accurately detect PRRSV and can be suitable for diagnostic applications in the field.

Development of a novel glycoprotein-based immunochromatographic test for the rapid serodiagnosis of bovine brucellosis

AIMS

Bovine brucellosis is a worldwide zoonotic disease that causes important economic losses and public health concerns. Because control of the disease depends on vaccination, serodiagnosis and isolation of the infected animals; affordable, rapid and accurate point of care (POC) tests are needed.

METHODS AND RESULTS

We developed and evaluated a novel glycoprotein-based immunochromatographic test for the detection of IgG antibodies against the O-polysaccharide of Brucella in bovine serum samples. Brucella GlycoStrip combines the power of immunochromatographic and bacterial glycoengineering technologies for the diagnosis of bovine brucellosis. The analysis of positive and negative reference samples indicated that the test has a diagnostic sensitivity and specificity of 96.9% (95% CI: 92.7-100.0%) and 100%, respectively.

CONCLUSIONS

Due to the recombinant glycoprotein-based antigen OAg-AcrA, which consists of the O-side chain of Brucella smooth lipopolysaccharide (sLPS) covalently linked to the carrier protein AcrA, the test is highly accurate, allows the differentiation of infected animals from those vaccinated with a rough strain or with a single dose of a smooth strain and fulfill the minimum diagnostic requirements established by the national and international regulations.

SIGNIFICANCE AND IMPACT OF STUDY

This strip test could provide a rapid (10 min) and accurate diagnosis of bovine brucellosis in the field contributing to the control of the disease.