Lettuce‐produced hepatitis C virus E1E2 heterodimer triggers immune responses in mice and antibody production after oral vaccination

Abstract

SummaryThe hepatitis C virus (HCV) is a major etiologic agent for severe liver diseases (e.g. cirrhosis, fibrosis and hepatocellular carcinoma). Approximately 140 million people have chronic HCV infections and about 500 000 die yearly from HCV‐related liver pathologies. To date, there is no licensed vaccine available to prevent HCV infection and production of a HCV vaccine remains a major challenge. Here, we report the successful production of the HCV E1E2 heterodimer, an important vaccine candidate, in an edible crop (lettuce, Lactuca sativa) using Agrobacterium‐mediated transient expression technology. The wild‐type dimer (E1E2) and a variant without an N‐glycosylation site in the E2 polypeptide (E1E2∆N6) were expressed, and appropriate N‐glycosylation pattern and functionality of the E1E2 dimers were demonstrated. The humoral immune response induced by the HCV proteins was investigated in mice following oral administration of lettuce antigens with or without previous intramuscular prime with the mammalian HEK293T cell‐expressed HCV dimer. Immunization by oral feeding only resulted in development of weak serum levels of anti‐HCV IgM for both antigens; however, the E1E2∆N6 proteins produced higher amounts of secretory IgA, suggesting improved immunogenic properties of the N‐glycosylation mutant. The mice group receiving the intramuscular injection followed by two oral boosts with the lettuce E1E2 dimer developed a systemic but also a mucosal immune response, as demonstrated by the presence of anti‐HCV secretory IgA in faeces extracts. In summary, our study demonstrates the feasibility of producing complex viral antigens in lettuce, using plant transient expression technology, with great potential for future low‐cost oral vaccine development.

Parenteral–Oral Immunization with Plant-Derived HBcAg as a Potential Therapeutic Vaccine against Chronic Hepatitis B

“…Hence, we presume that the trace induction of anti-HBc S-IgA here may have resulted from an adopted immunization protocol comprising the prime injection and low-dosed oral boosting performed in long intervals, which is analogous to immunization with HBsAg [15]. This supposition can be supported by other reports, which showed that exclusive oral immunization or higher or frequent dosage of antigens evoked polarization of the GALT response toward significant mucosal immunity, sometimes over a systemic one [17,35,36]. Moreover, in this context, the induction of a significant systemic response by orally administered plant-derived HBcAg without any exogenous adjuvant can be considered an additional benefit.…”

Plant‐produced Zika virus envelope protein elicits neutralizing immune responses that correlate with protective immunity against Zika virus in mice

“…Edible plants such as lettuce may offer a more palatable choice for the production of oral vaccines (Chen et al ., ; Lai et al ., ). Notably, a very recent publication demonstrated that oral administration of lettuce‐derived hepatitis C virus E1E2 dimers following an intramuscular priming elicited both systemic and mucosal immune responses (Clarke et al ., ). This result illuminates the feasibility of producing E protein‐based oral vaccines for Flaviviridae viruses including ZIKV.…”

Validation of leaf and microbial pectinases: commercial launching of a new platform technology

“…Chloroplast genetic engineering offers several unique advantages including high‐level expression (Bally et al ., ; Clarke et al ., ; Daniell et al ., ,; Jin and Daniell, ; Sanz‐Barrio et al ., ), transgene containment through maternal inheritance (Daniell, , ) and production in leaves enabling harvest before flowering offer almost complete transgene containment. Biomass for enzyme products is currently produced in Fraunhofer hydroponic facility by PhylloZyme.…”

“…To the best of our knowledge, this is the first report of engineered high-value commercial products produced in leaves for industrial applications using crude leaf extracts (Table 1; Figures S1 and S2). Chloroplast genetic engineering offers several unique advantages including high-level expression (Bally et al, 2009;Clarke et al, 2017;Daniell et al, 2016a,b;Jin and Daniell, 2015;Sanz-Barrio et al, 2011), transgene containment through maternal inheritance (Daniell, 2002(Daniell, , 2007 and production in leaves enabling harvest before flowering offer almost complete transgene containment. Biomass for enzyme products is currently produced in Fraunhofer hydroponic facility by PhylloZyme.…”