Immunogenic Analysis of Plant-Derived Recombinant Hepatitis A Virus VP1-Fc in Sublingual-, Nasal-, and Oral-Immunized Mice

Hepatitis A virus (HAV) causing an acute viral hepatitis diseases in human belongs to a picornavirus with a single-stranded, positive-sense RNA genome coding a single polyprotein that is subsequently processed into structural and nonstructural proteins. Capsid protein VP1 containing a major immunodominant epitope of HAV appears to be the dominant structural protein. The production of antigenic VP1 protein is necessary for immunological and biochemical studies directed towards subunit vaccine development. In this work, recombinant chimeric protein (TAT-VP1-Fc-KDEL), consisting of TAT (trans-activating transcriptional activator), human hepatitis A virus VP1, an Fc antibody fragment, and endoplasmic reticulum retention signal (KDEL), was expressed in Agrobacterium-infiltrated Nicotiana benthamiana leaves using a beet curly top virus (BCTV) vector system. Recombinant TAT-VP1-Fc/KDEL had a molecular mass of approximately 68 kDa. Recombinant TAT-VP1-Fc/KDEL, purified using Protein A Sepharose affinity chromatography, elicited production of specific IgG and IgG subclasses (IgG1, IgG2a, and IgG2b) in the serum after sublingual-, nasal-, and oral-immunization. Additionally, recombinant TAT-VP1-Fc/KDEL elicited production of specific IgA in the feces and vaginal wash. These results suggest that recombinant TAT-VP1-Fc/KDEL from infiltrated tobacco plants can be used as an effective experimental immunogen in vaccine development. This work was supported by a grant from the Next-Generation BioGreen 21 Program (PJ009553), Rural Development Administration, Republic of Korea.