Application of Western blot analysis for the diagnosis of Encephalitozoon cuniculi infection in rabbits: example of a quantitative approach.

Diagnosis of Encephalitozoon cuniculi infection in rabbits remains a major veterinary issue. ELISA or immunofluorescence assays are the current reference standards of serological tests. However, these conventional techniques suffer from a lack of accuracy for distinguishing active from past infections, as a positive serostatus is common in clinically normal rabbits. In this study, we assessed the diagnostic performance of Western blot (WB) to detect both anti-E. cuniculi immunoglobulin G (IgG) and immunoglobulin M (IgM) in comparison with ELISA and to address the intensity of the immune response through a quantitative approach. Positive WB results were highly correlated with the E. cuniculi-related diseased status (P < 0.0001). Although it was more labor intensive and less standardized, quantitative WB provided detailed comparable analysis regarding the humoral response and diagnostic performance similar to ELISA testing with statistically higher sensitivity (88.4 vs. 76.1% for IgG detection and 84.3 vs. 70.4% for IgM, P < 0.01). Several specific WB bands were shown to be significantly associated with concomitant clinical signs, like the one located at 50 kDa (OR = 8.2, [2.4-27.7], P = 0.0008) for IgG and (OR = 27.9, [4.2-187.9], P = 0.0006) for IgM. Therefore, the quantitative WB may have application in veterinary diagnostic laboratories to increase the accuracy of the clinical diagnosis of E. cuniculi infection. In addition, this tool may help to further understand the development and function of the humoral immune response to this infectious agent.