Indirect ELISA with recombinant GP5 for detecting antibodies to porcine reproductive and respiratory syndrome virus

Development of Indirect ELISA and its evaluation in Comparison with KOH hydrolysis and Fungal culture for the immuno diagnosis of Trichophyton rubrum and Trichophyton mentagrophytes infection in Humans

Trichophyton is a keratinophilic fungus that can invade keratinized tissues of humans and cause superficial mycoses called dermatophytosis. The objective of this study was to develop and evaluate indirect ELISA in comparison with gold standard methods such as direct microscopic examination of KOH mounts and fungal culture for the diagnosis of Trichophyton infection in humans. The present investigation reports the production and partial purification of T. rubrum mycelial antigens and production of specific polyclonal antibodies. It also reports the development and optimization of indirect ELISA and evaluation of its potential in comparison with gold standard methods for the diagnosis of Trichophyton infection in humans. The diagnostic sensitivity and specificity of Trichophyton indirect ELISA was 93.75% and 93.33 % respectively. The positive and negative predictive values were high as well, found to be 93.75% and 90.00% respectively indicating usefulness of the assay. In all comparisons, the correlation coefficient (r) value was >0.5 indicating strong correlation between KOH hydrolysis test, fungal culture method and indirect ELISA. A significant correlation coefficient of 0.856 (P < 0.0001) was obtained between indirect ELISA and fungal culture method. This shows a good agreement between fungal culture method and indirect ELISA. The present study clearly shows diagnostic performance of Trichophyton indirect ELISA developed in this study is efficient as fungal culture method for the diagnosis of Trichophyton infection in humans.

Diagnosis of porcine circovirus type 2 infection with a combination of immunomagnetic beads, single-domain antibody, and fluorescent quantum dot probes

The use of a specific antibody conjugated with nanobeads, forming immunomagnetic nanobeads (IMNBs), has been demonstrated to be useful for the capture and detection of viruses. In this study, IMNBs functionalized with a single-domain antibody against the capsid protein (Cap) of porcine circovirus type 2 (PCV2), hereafter denoted as psdAb, were evaluated and used to capture PCV2. Quantum dots (QDs) conjugated with psdAb were used as a fluorescence probe to visualize PCV2 captured by IMNBs. The specificity and sensitivity of this method were further evaluated using common pathogens of pig viral disease and PCV2. To assess its practicality, clinical samples were tested in this study. The results showed that 2.57 ± 0.13 mg Cap or 0.97 ± 0.064 × 10(6) copies of PCV2 particles could be captured by 1 mg of IMNBs in 30 min. This suggests that the IMNBs have the ability to efficiently capture PCV2 with good specificity, as there was no cross-reaction with other pathogens, and with strong sensitivity, with a detection limit as low as 10(3) copies/ml of PCV2 particles. Moreover, PCV2 in inguinal lymph node, lung, spleen, serum, and fecal samples was successfully detected by IMNBs. The results demonstrate that this method is promising for the rapid and effective detection of PCV2 in complex clinical samples.

Development of a recombinant N-Gp5c fusion protein-based ELISA for detection of antibodies to porcine reproductive and respiratory syndrome virus

The recent dramatic increase in reported cases of porcine reproductive and respiratory syndrome (PRRS) in pig farms is a potential threat to the global swine industry, and thus, detecting PRRS virus (PRRSV) in pig herds is essential to help control the spread of PRRS. IDEXX HerdChek™ PRRS, a commercially available indirect enzyme-linked immunosorbent assay (iELISA), is the industry standard for detection of antibodies against PRRSV. In the present study, an effective iELISA for detection of PRRSV antibodies was developed using a recombinant fusion protein N-Gp5c (rN5c, a combination of the nucleocapsid protein and the C-terminal 78 aa of Gp5) produced in Escherichia coli. This assay was validated by comparison with an immunofluorescent assay and IDEXX-ELISA. The diagnostic specificity, sensitivity, and accuracy of the rN5c-iELISA method were 94.8, 95.6, and 95.1%, respectively. Cross-reactivity assays demonstrated that iELISA was PRRSV-specific. Repeatability tests revealed that the coefficients of variation of positive sera within and between runs were less than 13 and 22%, respectively. The rN5c-iELISA is simpler to produce and perform, time-saving, and suitable for large scale surveys of PRRSV infection at lower cost.

Application of GP5 protein to develop monoclonal antibody against porcine reproductive and respiratory syndrome virus

In this study, a panel of monoclonal antibodies (mAbs) against Porcine reproductive and respiratory syndrome virus(PRRSV), named as 8C9 and4B4, were produced by fusing SP2/0 myeloma cells and spleen cells of BALB/c mice immunized with the PRRSV (TCID(50)=5.5), screened by the indirect ELISA and subjected to several limiting dilutions. mAbs were then identified by biological characterization. Among the two fusion cell strains, 8C9 belonged to the IgG1 subclass and 4B4 belonged to the IgG2a subclass. The titers in cell culture supernatant and abdomen liquor reached to 1:10(4)and 1:10(5), respectively. The specificity test indicated that the two cells had specific reactions for the PRRSV and GP5 protein respectively, and no reaction with Classical swine fever virus (CSFV) or Swine vesicular disease virus (SVDV). The molecular weights of the heavy chain and light chain were about 45.0 kDa and 25.0 kDa, respectively. In neutralization activity tests, the results showed that the prepared mAb 4B4 can protect 50% of cells with no CPE in dilution up to 1:512, but mAB 8C9 has no neutralization activities to PRRSV.