Rapid detection of specific polyclonal and monoclonal antibodies against bovine leukemia virus

Production, Characterization, and Use of Monoclonal Antibodies Against gp51 Protein to Diagnose Bovine Leukemia Virus Infection

Enzootic bovine leukosis (EBL) is a retroviral infection that causes persistent lymphocytosis and lymphosarcoma in cattle. The economic importance of infection by bovine leukemia virus (BLV) is due to several factors, including losses in exportation, treatment of secondary infection, and reduction in dairy production. To facilitate the development of a national test that is sensitive, simple, and applicable on a large scale, this work aimed to produce and characterize monoclonal antibodies (mAbs) against gp51 protein from BLV for use in an enzyme-linked immunosorbent assay (ELISA) test. Two hundred seventy-four hybridomas were generated, from which 37 were mAbs secretory clones screened by indirect ELISA. The specificity of the mAbs generated against gp51 was verified by Western blot analysis, and the isotypes were characterized for isotyping in IgG1 and IgM. To evaluate the test, 250 sera were tested by agar gel immunodiffusion and mAb-ELISA. The values obtained for the mAb-ELISA test were 95% sensitivity and 90% specificity.

Dot enzyme-linked immunosorbent assay for more reliable staging of patients with Human African trypanosomiasis

Human African trypanosomiasis (HAT) or sleeping sickness is a disease characterized by a hemolymphatic stage 1 followed by a meningoencephalitic stage 2 which is fatal without specific treatment. Furthermore, due to the toxicity of drugs used to treat stage 2 (mainly melarsoprol) accurate staging is required. Actual criteria employed during field surveys are not sensitive enough for precise staging. Antineurofilament (anti-NF) and antigalactocerebrosides (anti-GalC) antibodies have been identified in cerebrospinal fluid (CSF) as potential markers of central nervous system (CNS) involvement. We describe a dot enzyme-linked immunosorbent assay (dot-ELISA) to detect anti-GalC and anti-NF antibodies and its value in staging. NF- and GalC-dotted nitrocellulose strips were first developed in our laboratory. They were then evaluated in Angola and Central African Republic on 140 CSF samples. Compared to our staging criteria (i.e., CSF cell count > or = 20 cells/microl, CSF immunoglobulin M concentration > or = 100 mg/liter, and/or the presence of trypanosomes in the CSF), combined detection of both CSF anti-NF and CSF anti-GalC by dot-ELISA showed 83.2% sensitivity and 100.0% specificity. Dot-ELISA could be a useful test to diagnose CNS involvement in HAT in the less-equipped laboratories or in the field situation and to improve patient treatment.

Evaluation of virus excretion by cells persistently infected with the bovine leukaemia virus (BLV) using monoclonal antibodies

BACKGROUND

bovine leukaemia virus (BLV) is the causative agent of enzootic bovine leukaemia. Studies in vitro usually require the use of infected cell lines, mostly to produce antigen. Two of the most widely used cell lines are FLK-BLV and BLV-bat2.

OBJECTIVE

the dynamics of the excretion of BLV proteins and whole virus by the persistently BLV-infected cell lines mentioned above was studied using an indirect ELISA in combination with eight monoclonal antibodies (mAbs) and cow and rabbit serum.

STUDY DESIGN

tissue culture flasks were seeded with different concentrations of cells (13000-67000 cells per cm2, corresponding to 1-5 million cells per 75 cm2 flask) and were studied for 20 days. Samples (1.5 ml) were removed every 24 h and the presence of BLV proteins was determined using an indirect ELISA assay in which the antigen reaction with the monoclonal antibodies was evidenced by peroxidase labeled anti-mouse immunoglobulins.

RESULTS

cell line FLK-BLV produced a complete monolayer as early as 4 days after passage, 3 days earlier than BLV-bat2. Using mAbs, the amount of viral proteins in the supernatant showed a cyclic pattern, with two evident peaks at days ca. 8 and 16. These peaks occurred even in the absence of passage or medium change, which causes depletion of essential nutrients and acidity. In comparison to polyclonal serum, mAbs gave more clear and defined values and are useful for determining the dynamics of viral production.

CONCLUSION

when aiming for high viral yield, BLV should be harvested between days 6 and 8 after passage, when viral shedding is at its maximum. These results are very useful for preparing antigen for monoclonal antibody production, or for techniques such as ELISA or Western blot.

Comparative study of PCR as a direct assay and ELISA and AGID as indirect assays for the detection of bovine leukaemia virus

The choice of a diagnostic method depends on the characteristics of the herd to be analysed. Two herds with different prevalences of enzootic bovine leukaemia were chosen to study the concordance between agar gel immunodiffusion (AGID), enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) methods. PCR, an increasingly used virological method, was performed with four sets of primers, amplifying different genomic regions (env, pol and tax), from DNA extracted either from peripheral blood monocytes (PBMCs) or milk leucocytes. The highest percentage of positive animals was obtained using PCR performed with DNA extracted from PBMCs using primers which amplified either env or pol, followed by PCR using PBMCs and primers which hybridized with tax, then ELISA using serum and finally AGID. The results of PCR were more consistent with PBMCs than when milk leucocytes were used.

Production and characterization of monoclonal antibodies against bovine leukaemia virus using various crude antigen preparations: a comparative study

A total of 59 monoclonal antibodies (mAbs) specific against the bovine leukaemia virus (BLV) using different antigen preparations was produced. The five antigen preparations for immunizing BALB/c mice were: live cells (CEL), sonicated and ultracentrifuged cells (SOC), cell lysates (LYS), semi-purified BLV (PV), and formalin-treated cells (FOR) from two cell lines permanently infected with BLV (FLK-BLV and BLV-bat2). These viral component presentations were selected to obtain mAbs against specific BLV proteins: located on the cell surface (FOR and CEL), in free virus particles (PV) and intracellular viral proteins (SOC and LYS). Two antigen preparations (SOC and LYS) were lethal to the mice following the intravenous and intrasplenic routes. Six fusions were performed in this study that rendered specific antibodies against BLV. The highest number of hybridomas was produced with SOC; however, the majority of the hybridomas produced (> 90%) were against cellular proteins. Even though immunization with PV gave the lowest number of hybridomas, the majority of them were specific against BLV. Based on the reactivity of the mAbs in Western blot (WB), we classified the mAbs into five groups, namely anti-gp51SU (39 mAbs), anti-gp30TM (six mAbs), anti-Pr72env (nine mAbs), anti-Pr66gag-pro (one mAb) and anti-Prgag (four mAbs). A very high percentage of the mAbs produced (48 of 59) reacted with gp51SU, suggesting that this is the most immunogenic and accessible BLV protein presented in the different antigen preparations. The majority of our mAbs recognized more than one band in WB, suggesting that, aside from reacting with mature proteins, the mAbs also recognized viral precursors.