The pentameric B subunit of cholera toxin (CtxB) is an efficient mucosal adjuvant for vaccines. We report the expression of a chimeric protein comprising the synthetic cholera toxin B subunit fused at its C-terminal with rabies surface glycoprotein (G protein) in tobacco plants. The similar to 80.3 kDa fusion polypeptide expressed at 0.4% of the total soluble protein in leaves of the selected transgenic lines. The fusion protein formed a similar to 403 kDa pentameric protein which was functionally active in binding to GM1 receptor. The plant-made protein had a higher affinity for GM 1 receptor than the native bacterial CtxB. The pentameric fusion protein was recognized by the anti-cholera toxin as well as anti-rabies antibodies. Its immuno-protective ability against rabies remains to be examined. (C) 2009 Elsevier Inc. All rights reserved.