Development and evaluation of an immunochromatographic assay using a gp51 monoclonal antibody for the detection of antibodies against the bovine leukemia virus

Antigenicity of subregions of recombinant bovine leukemia virus (BLV) glycoprotein gp51 for antibody detection

Bovine leukemia virus (BLV) is an enveloped virus, found worldwide that can infect cattle and induce many subclinical symptoms and malignant tumors. BLV infection causes severe economic losses in the cattle industry. The identification of BLV-infected cattle for segregation or elimination would be the most effective way to halt the spread of BLV infection on farms, owing to the lack of effective treatments and vaccines. Therefore, antibody detection against the viral glycoprotein gp51 is an effective method for diagnosing BLV-infected animals. In this study, ten different subregions of gp51 containing a common B cell epitope are vital for developing antigens as epitope-driven vaccine design and immunological assays. Such antigens were produced in Escherichia coli expression system to react with antibodies in the serum from BLV-infected cattle and compete for antigenicity. Recombinant His-gp51^56-110 and gp51^33-301(full) had the same sensitivity in BLV-positive sera, indicating that antibodies responded to the limited subregion of viral gp51, a common B cell epitope. This finding provides significant information for antigen selection in BLV to use in antibody detection assays. Further studies are needed to evaluate the antigenicity of His-gp51^56-110 and gp51^33-301(full) as antigens for antibody detection assays using a larger number of bovine serum samples.

Triple Immunochromatographic System for Simultaneous Serodiagnosis of Bovine Brucellosis, Tuberculosis, and Leukemia

An immunochromatographic test system has been developed for the simultaneous rapid multiplex serodiagnostics of bovine brucellosis, tuberculosis, and leukemia. The test system is based on the use of a conjugate of gold nanoparticles with the chimeric protein Cysteine-A/G and three analytical zones with immobilized pathogen antigens: Brucella abortus lipolysaccharide, recombinant proteins MPB64 and MPB83-MPB63 of Mycobacterium bovis, and recombinant protein p24 of the bovine leukemia virus. Prototypes of the test system were tested on 98 samples of sera from healthy and infected animals. The diagnostic sensitivity of the developed test system was 92% for brucellosis, 92% for tuberculosis, and 96% for leukemia. False positive test results were not observed.

A simple and rapid assay to evaluate purity of foot-and-mouth disease vaccine before animal experimentation

Currently, foot-and-mouth disease (FMD) vaccine purity is tested in cattle to detect antibodies against the non-structural protein (NSP) after repeated immunization with the final vaccine product. In case of vaccine failure, the manufacturing company would suffer significant economic loss. To prevent such unfortunate losses with the final vaccine product, in vitro testing is required to quantitate an NSP antigen during the manufacturing process prior to animal experiments. A novel lateral-flow assay device was developed using a monoclonal antibody (MAb) against the 3B NSP. To determine the minimal amount of NSP required to elicit antibodies in livestock, goats were immunized several times with various concentrations of either the recombinant 3AB (rec.3AB) protein or FMD virus culture supernatant. Antibodies against 3AB were elicited after a second immunization with 10.6 ng to 42.5 ng of rec.3AB and a third immunization with a 10-fold diluted FMD virus culture supernatant in goats. The lateral-flow assay device detected the minimal amount of rec.3AB and native NSP in FMD virus culture supernatant required to induce NSP antibodies in goats. The in vitro assay device is simple and economical, provides rapid results, and should be useful for FMD vaccine-manufacturing companies prior to conducting animal experiments to test the vaccine purity.