Localization of rabies virus glycoprotein into the endoplasmic reticulum produces immunoprotective antigen

Rabies virus surface glycoprotein (rabies G-protein) with (G+RS) and without (G-RS) endoplasmic reticulum retrieval signal was expressed and characterized in tobacco plants. Transgenically expressed rabies G-protein was estimated at 0.015-0.38 % of total leaf protein. The relative migration of the rabies G-protein on SDS-PAGE was at the position, as anticipated for the viral coat protein (~66 kDa). Immunolocalization by confocal microscopy established that immunoprotective G+RS expressed in tobacco was primarily confined to ER. G+RS showed binding to Con A lectin and was susceptible to N-glycosidase F activity similar to native rabies G-protein. However, the G-RS transgenically expressed in tobacco leaves was glycosylated differently and was resitant to N-glycosidase F. Immunological studies and Rapid Fluorescent Foci Inhibition Test (RFFIT) showed that G+RS was immunogenic and immunoprotective, whereas G-RS was moderately immunogenic but non-protective against live virus challenge. Hence, plants can express the antigenic component of rabies virus with suitable glycosylation, which is important to give protection against rabies virus infection.