Development of an interferon-γ release assay (IGRA) for detection of Brucella abortus and clinical diagnosis of brucellosis

Abstract

Introduction: Brucellosis, caused by Brucella abortus (B. abortus), is an important zoonosis posing a great risk to both livestock and humans. Currently, most assays for clinical diagnosis of brucellosis have been developed based on serological principles; however, these assays have a number of limitations and disadvantages.

Methodology: To address this concern, the aim of this study was to develop a gamma interferon (IFN-γ) release assay (IGRA) for the diagnosis of brucellosis. Towards this end, the stimulating effect induced by different somatic antigens of B. abortus on the secretion of IFN-γ was evaluated.

Results: The best antigen candidate, B. abortus strain 2308, able to induce high levels of IFN-γ expression in peripheral blood (PB) cells from cattle, was used for the development of the IGRA. The optimal concentration for stimulation was determined as 1.0×10⁷ CFU/mL. This study demonstrated that IFN-γ was detectable on day 5 post infection (p.i.) and peaked on day 14 p.i.. Finally, the IGRA developed was used for detection of B. abortus in clinical samples, and a higher level of IFN-γ was detected in Brucella-infected samples compared to vaccination samples and negative controls.

Conclusions: The optimal somatic antigen for B. abortus was identified and used to establish a robust IGRA. The IGRA developed is suitable for clinical diagnosis of brucellosis, especially in the early stages of infection.