Development of a capsid based competitive inhibition enzyme-linked immunosorbent assay for detection of bovine immunodeficiency virus antibodies in cattle and buffalo serum

Bovine immunodeficiency virus: a lentiviral infection

The bovine immunodeficiency virus (BIV) is a lentivirus which is known to infect cattle worldwide. Though serological and genomic evidence of BIV in cattle has been found throughout the world, isolation of the virus has been reported only from few places. Very little is known about its impact on animal health status, pathogenesis and mode of transmission. BIV is considered generally non-pathogenic and is not known to cause any serious disease in cattle. BIV is genetically and antigenically related to Jembrana disease virus (JDV), the cause of an acute disease in Bali cattle (Bos javanicus) and human immunodeficiency virus, the cause of acquired immunodeficiency syndrome in human. Therefore, it is important to monitor the presence of BIV in cattle to keep vigil over its possible evolution in its natural host to emerge as pathogenic lentivirus like JDV. Differentiation of BIV infection in cattle from the acutely pathogenic JDV is important for diagnosis of the latter. Currently, BIV is considered as a safe model for understanding the complex genome of lentiviruses. Further research on BIV is indeed needed to elucidate its possible role in animal health as well as for insight into the molecular mechanisms adopted by related lentiviruses.

Recombinant protein-based viral disease diagnostics in veterinary medicine

Identification of pathogens or antibody response to pathogens in human and animals modulates the treatment strategies for naive population and subsequent infections. Diseases can be controlled and even eradicated based on the epidemiology and effective prophylaxis, which often depends on development of efficient diagnostics. In addition, combating newly emerging diseases in human as well as animal healthcare is challenging and is dependent on developing safe and efficient diagnostics. Detection of antibodies directed against specific antigens has been the method of choice for documenting prior infection. Other than zoonosis, development of inexpensive vaccines and diagnostics is a unique problem in animal healthcare. The advent of recombinant DNA technology and its application in the biotechnology industry has revolutionized animal healthcare. The use of recombinant DNA technology in animal disease diagnosis has improved the rapidity, specificity and sensitivity of various diagnostic assays. This is because of the absence of host cellular proteins in the recombinant derived antigen preparations that dramatically decrease the rate of false-positive reactions. Various recombinant products are used for disease diagnosis in veterinary medicine and this article discusses recombinant-based viral disease diagnostics currently used for detection of pathogens in livestock and poultry.

Prior bovine immunodeficiency virus infection does not inhibit subsequent superinfection by the acutely pathogenic Jembrana disease virus

In cattle the interaction between the two genetically and antigenically related bovine lentiviruses, the acutely pathogenic Jembrana disease virus (JDV) and the non-pathogenic Bovine immunodeficiency virus (BIV) has not been reported although both JDV and a BIV-like virus have been reported in the Bali cattle (Bos javanicus) population in Indonesia. The outcome of infection of Bali cattle with the R29 strain of BIV prior to superinfection 42 days later with JDV(TAB/87) was determined. All BIV-inoculated cattle were successfully infected and developed an antibody response to the TM and CA proteins. BIV infection did not prevent subsequent infection with JDV or ameliorate the clinical signs of Jembrana disease in the infected cattle. It did, however, modify the dynamics of the JDV infection with an earlier onset and end of the acute disease process, and a reduction in the duration of viremia that exceeded 10(6) genome copies/ml of plasma.

Single-chain fragment variable antibody against the capsid protein of bovine immunodeficiency virus and its use in ELISA

Recombinant antibody specific for the capsid (CA) protein of bovine immunodeficiency virus (BIV) was generated in the form of single-chain fragment variable (ScFv) using the phage display technique for affinity selection. The variable heavy (V(H)) and variable light (V(L)) chain gene fragments were recovered from cells of CA-specific hybridoma (9G10) described previously. The V(H) and V(L) DNA fragments were assembled through a flexible linker DNA to generate ScFv fragment which was cloned in a phagemid expression vector to express ScFv protein. The specific reactivity of the expressed ScFv to the CA antigen was confirmed by Western blot, and the ScFv fragment was used to develop a competitive inhibition ELISA for detection of antibodies to BIV in cattle and buffalo. The recombinant antibody was shown to be more than four times sensitive than its parent monoclonal antibody (MAb, 9G10) by testing of spiked samples of reference positive sera. The improved sensitivity of the recombinant antibody-based ELISA was confirmed by the detection of a larger proportion of animals with BIV antibody by it than by the MAb-based ELISA.