| A two-dimensional gel electrophoresis (2-DE) protocol was optimized and used to study differential protein expression in the spleen of the chicken in response to Marek's disease virus (MDV) infection. Initially, the reproducibility of the optimized 2-DE protocol was tested and 648+/-92 (n=27 gels) protein spots with isoelectric points between 3-10 and molecular masses of 14-120 kDa were visualized. Correlation coefficients for protein spot volumes within each animal were between 0.78-0.96 and those among animals were between 0.94-9.97. This protocol was then used to study proteomic changes in the chicken spleen in response to experimental MDV infection. Infection of chickens with the RB1B-MDV resulted in differentially expressed proteins at least once at 7, 14, or 21 days post infection (d.p.i.). The identified proteins were involved in a variety of cellular functions including antigen processing and presentation, ubiquitin-proteasome protein degradation, apoptosis, and formation of cellular structural components. Subsequently, JM16-MDV infected spleen proteomes of genetically susceptible B19 and resistant B21 chickens were compared at 4, 7, 14, and 21 d.p.i. The differentially regulated proteins between lines were determined to be involved in various cellular activities such as antioxidative functions, molecular chaperoning, protein elongation, RNA processing, and cell proliferation. Proteomic profiling of infected spleens revealed that different components of major histocompatiblity complex (MHC) class II molecules were down-regulated. It was hypothesized that MDV infection interferes with the MHC class II-mediated antigen presentation through manipulation of the interferon (IFN)-gamma inducible MHC class II gene expression pathway. Accordingly, the effect of MDV infection on the expression of a panel of selected genes was quantified in spleens of chickens infected with RB1B-MDV. This final study showed a significant down-regulation of all components of the MHC class II heterotrimer together with significant changes in the expression of several other IFN-gamma signaling molecules in MDV infected chickens at multiple sampling points, suggesting a possible mechanism by which MDV may evade host immunosurveillance. Overall, this endeavor sheds light on some of the mechanisms of host response to MDV as well as the underlying basis for genetic resistance to MD in chickens. |
