Development and characterization of monoclonal antibodies against Besnoitia besnoiti tachyzoites

Preparation of a novel monoclonal antibody against Avian leukosis virus subgroup J Gp85 protein and identification of its epitope

Avian leukosis virus subgroup J (ALV-J) is an avian oncogenic retrovirus that has caused huge economic losses in the poultry industry due to its great pathogenicity and transmission ability. However, the continuous emergence of new strains would bring challenges to diagnosis and control of ALV-J. .This study focuses on preparing the monoclonal antibody (MAb) against ALV-J Gp85 and identifying its epitope. The truncated ALV-J gp85 gene fragment was amplified and then cloned into expression vectors. Purified GST-Gp85 was used to immune mice and His-Gp85 was used to screen MAb. Finally, a hybridoma cell line named J16 that produced specific MAb against the ALV-J. Immunofluorescence assay showed that MAb J16 specifically recognized ALV-J rather than ALV-A or ALV-K infected DF-1 cells. To identify the epitope recognized by MAb J16, fourteen partially overlapping ALV-J Gp85 fragments were prepared and tested by Western blot. The results indicated that peptide 150-LIRPYVNQ-157 was the minimal epitope of ALV-J Gp85 recognized by MAb J16. Alignment analysis of Gp85 from different ALV subgroups showed that the epitope keep high conservation among 36 ALV-J strains, but significant different from that of ALV subgroup A, B, C, D, E and K. Overall, we prepared a MAb specific against ALV-J and identified peptide 150-LIRPYVNQ-157 as a novel specific epitope of ALV-J Gp85, which may assist in laying the foundation for specific ALV-J detection methods.

First highly sensitive and specific competitive ELISA for detection of bovine besnoitiosis with potential as a multi-species test

Serological cross-reactions represent a serious problem in some currently available tests to diagnose Besnoitia infections in many species including cattle, caribou and donkeys. False-positive results are due to the low positive-predictive value of these serological tests for besnoitiosis. These tests therefore have clear limitations if large herds are screened in areas with low prevalence, since increased numbers of false-positive reactions require confirmatory testing by alternative serological methods, e.g. immunoblotting, which are time-consuming and create extra costs. To overcome this problem, we aimed to develop a highly sensitive and specific competitive ELISA (cELISA) using a panel of 12 monoclonal antibodies raised against the tachyzoite stage of Besnoitia besnoiti. A cELISA set up with one of these antibodies (Bb-cELISA1) was screened with a large panel of B. besnoiti-positive bovine sera to estimate the diagnostic sensitivity of the test. Sera from herds with Neospora caninum- or Sarcocystis spp.-infected cattle were used to estimate its diagnostic specificity. Relative to a reference standard, which combined the results obtained in a previously established highly sensitive and specific ELISA, in the immunofluorescence antibody test and in B. besnoiti tachyzoite and bradyzoite immunoblots, the new Bb-cELISA1 revealed a diagnostic sensitivity of 99.2% (95% confidence interval: 97.1-99.9%) and a diagnostic specificity of 99.9% (95% confidence interval: 97.7-100%). This novel assay was tested on a variety of proven Besnoitia-positive sera from other species, including B. besnoiti-infected cats, rabbits or Besnoitia bennetti-infected donkeys or Besnoitia tarandi-infected caribou. The results obtained with the new Besnoitia-cELISA for these animal species also corresponded almost perfectly with those of the reference tests, which included immunoblot and immunofluorescence antibody tests. In conclusion, the novel Besnoitia-cELISA represents a valuable tool for the diagnosis and control of bovine besnoitiosis and for studies on the epidemiology of Besnoitia infections in a variety of host species, including naturally exposed wildlife and experimental hosts.