Antibody Responses in Mice Stimulated by Various Doses of the Potato-Derived Major Surface Antigen of Hepatitis B Virus

Abstract

The ability of potato-derived major surface antigen of hepatitis B virus (P-HBsAg) to elicit antibody responses to different dosages of P-HBsAg ranging from 0.02 to 30 g administered orally in mice was examined. All immunized groups produced specific serum IgG and fecal IgA antibodies against P-HBsAg, even at low levels (<5 g), after administration of a 0.5-g yeast-derived HBsAg (Y-HBsAg; LG Life Sciences, Republic of Korea) booster.The major surface antigen of hepatitis B virus (HBV) (HBsAg) is one of the best-developed examples of a plant-derived antigen (6,9,11,13,18); however, low expression levels prevent plant-derived antigens from being economically competitive (5,15,16). Average antigen expression levels are in the range of 0.01% to 0.4% of total soluble protein (TSP). Aspects related to eliciting protective antibody responses, e.g., oral administration doses (1, 10), efficient delivery of oral vaccines (3, 4), and functional effects of adjuvants (12), were identified to stimulate immune responses after vaccination with low levels of plant-derived antigen.The objective here was to examine the effects of plant-based oral immunization on HBV-specific immune responses over a broad range of doses, from the lowest dose of 0.02 g potatoderived HBsAg (P-HBsAg) to the maximum dose of 30 g P-HBsAg. IgG humoral and IgA mucosal responses were observed at various P-HBsAg doses, and these results are discussed in relation to the optimization of plant-derived vaccines. Furthermore, the analysis of IgG subclass distribution following oral administration with varied doses of P-HBsAg was carried out to understand the mechanism of the immune response.To evaluate the immunogenicity upon oral administration of various doses of P-HBsAg from a plant line showing the highest production of HBsAg (7, 18), mice were immunized orally with tuber extract on days 1, 7, and 14. The detailed procedure was described previously (18). Mice were immunized with 150 g of yeast-derived HBsAg (Y-HBsAg; LG Life Sciences, Republic of Korea) mixed with 10 g of Cholera toxin (CT; Sigma) as a positive control. Each concentration of P-HBsAg administered to mice was divided into one of the the following three groups: lower level, consisting of 0.02, 0.1, and 0.5 g; middle level, consisting of 1.0, 2.5, and 5.0 g; and higher level, consisting of 10 g, 15 g, and 30 g. Only five concentrations (0.1, 1.0, 5.0, 10, and 30 g) were shown among the nine concentrations depicted in the figures to help with understanding by using a concise arrangement. Antigen-specific IgG responses to representative doses in mouse sera against P-HBsAg were graphically monitored up to week 12 (Fig. 1a). The groups administered 10 g and 30 g of antigen stimulated slight primary responses of 41 mIU and 51 mIU, respectively, at 7 weeks before booster administration compared to responses of the mice immunized with potato extract from the nontransformed (NT) plant (NT group) (4 mIU). Mice administered higher levels of P-HBsAg (10, 15, and 30 g) exhibited significantly increased immu...

Plant‐made oral vaccines against human infectious diseases—Are we there yet?

“…The expression level of the major surface antigen of hepatitis B virus (P‐HBsAg) reached 0.003–0.09% of TSP in transgenic potato. Mice produced specific faecal IgA and serum IgG antibodies against P‐HBsAg after oral administration (Youm et al ., ). Herbicide‐resistant lettuce was engineered to stably express the small surface antigen of hepatitis B virus (S‐HBsAg) (Pniewski et al ., ).…”

Production of Pharmaceutical Proteins in Solanaceae Food Crops

“…In this regard, it is of interest to mention the work from Youm et al [89] who examined the antibody response in mice orally immunized using various doses of potato-derived major surface antigen of hepatitis B virus (ranging from 0.02 to 30 μg potato-derived antigen). Approaches to increase the yield of recombinant protein expressed in transgenic plants include down regulation of native proteins within the tubers and targeting the protein to the cell secretory pathway.…”

Mucosal Vaccines from Plant Biotechnology

“…These data coupled with those described above (Kapusta et al, 2010;Kostrzak et al, in press) argue for lower doses in order to avoid development of Treg-mediated tolerance. Different findings were obtained by feeding mice HBsAg transgenic potatoes at different doses (0.1-30 μg/ dose) with 10 μg CT adjuvant, three times weekly followed by a parenteral boost of 0.5 μg HBsAg at week 8 (Youm et al, 2010). In this study, anti-HBsAg antibodies in both serum and fecal samples increased in direct relation to the oral dose.…”