The development of an interferon-gamma (IFNγ) assay for the diagnosis of tuberculosis in African elephants (Loxodonta africana) and black rhinoceros (Diceros bicornis)

Abstract

The objective of this project was to design tools for a diagnostic test that will prove valuable in the detection of tuberculosis in elephants and rhinoceros by using the cytokine IFNγ as an indicator of Mycobacterium bovis responsiveness. Interferon-gamma (IFNγ), a type II interferon, is a cytokine mainly produced by Th1 and cytotoxic T-cells expressing surface markers CD4 and CD8, respectively and natural killer cells (Ibelgaufts; 1999). In response to a mycobacterial infection antigen specific Th1- and cytotoxic T-cells are induced. When these cells encounter their specific mycobacterial antigen, they will respond by producing IFNγ. Based on this principle a diagnostic test was developed. In this test PBMCs will be stimulated with M.bovis specific antigen and the subsequent production of IFNγ by specific T-helper cells will be determined by IFNγ of elephants and rhinoceros. In order to develop such an assay recombinant elephant and rhinoceros IFNγ was cloned, sequenced, expressed, purified and subsequently a monoclonal antibody against IFNγ was produced. Monoclonal antibodies were selected by a number of ELISAs using recombinant IFNγ. Preliminary results are promising and further tests are underway regarding the specificity and sensitivity of the assay before field trials can be performed. The results of this study has significant implications in the design of an IFNγ diagnostic kit for the diagnosis of tuberculosis, as caused by M.bovis, in elephants and rhinoceros as well as other wildlife affected by this debilitating disease.