Development and validation of cytokine quantitative, real time RT-PCR assays for characterization of Asian elephant immune responses

Infectious disease is an important factor in Asian elephant health and long-term species survival. In studying disease pathogenesis, it is important to consider not only the pathogen, but also the effectiveness of the host immune response. Currently, there is a paucity of information available on elephant immune function. Measurement of cytokine levels within clinical samples can provide valuable information regarding immune function during health and disease that may elucidate disease susceptibility. To develop tools for assessment of elephant immune function, Asian elephant partial mRNA sequences for interleukin (IL)-2, IL-4, IL-10, IL-12, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and β-actin were determined. Sequence information was then utilized to design elephant-specific primers and probes for quantitative, real time, RT-PCR assays for the measurement of cytokine mRNA. Greater than 300 bps of Asian elephant mRNA sequence were determined for each cytokine of interest. Consistent and reproducible, real time, RT-PCR assays with efficiencies of greater than 93% were also developed. Assay sensitivities ranged from less than 1 to 5000 DNA copies with the exception of IL-12, which had a sensitivity of 42,200 copies. Employment of molecular techniques utilizing mRNA-based detection systems, such as real time, RT-PCR, facilitate sensitive and specific cytokine detection and measurement in samples from species for which commercial reagents are not available. Future studies utilizing these techniques to compare elephant immune function during health and in the face of infection will be useful for characterizing the contribution of the elephant immune system to disease.