Analysis of specificity of the custom anti-human ORF2p monoclonal antibody in human cells. (A) Western blot analysis of mouse and human ORF2 (predicted size 150 and 149 kDa, respectively) and EN (predicted size 30 and 26 kDa, respectively) proteins generated from expression plasmids containing codon-optimized human ORF2 (hORF2), a codon-optimized sequence corresponding to the human ORF2 endonuclease fragment (hEN), codon-optimized mouse ORF2 (mORF2), and a codon-optimized sequence corresponding to the mouse ORF2 endonuclease fragment (mEN) transiently transfected in 293 cells. Custom anti-human ORF2p monoclonal antibody specifically detects proteins of human origin. (B) Western blot analysis of the same samples as in A was performed with custom anti-mouse ORF2p polyclonal antibodies which specifically detect proteins of mouse origin. Control lane indicates cells transiently transfected with an empty vector. GAPDH is used as a loading control; 15 to 150 kDa on the right indicate positions of molecular markers.