Abstract
Hepatitis B and C viruses chronically affect approximately 3.5% of the global population, causing more than 800,000 deaths yearly due to severe liver pathogenesis. Current HBV vaccines have significantly contributed to the reduction of chronic HBV infections, supporting the notion that virus eradication is a feasible public health objective in the near future. In contrast to HBV, a prophylactic vaccine against HCV infection is not available yet; however, intense research efforts within the last decade have significantly advanced the field and several vaccine candidates are shortlisted for clinical trials. A successful vaccine against an infectious disease of global importance must not only be efficient and safe, but also easy to produce, distribute, administer, and economically affordable to ensure appropriate coverage. Some of these requirements could be fulfilled by oral vaccines that could complement traditional immunization strategies. In this review, we discuss the potential of edible plant-based oral vaccines in assisting the worldwide fight against hepatitis B and C infections. We highlight the latest research efforts to reveal the potential of oral vaccines, discuss novel antigen designs and delivery strategies, as well as the limitations and controversies of oral administration that remain to be addressed to make this approach successful.
Highlights
Vaccination is the primary and most effective tool in combating infectious diseases in both humans and animals; the success of immunization critically depends on achieving a broad level of coverage, sufficient to interrupt transmission of pathogens [1]
We provide a concise update on the development of plant-based oral vaccines against two major human pathogens, the hepatitis B and C viruses, currently affecting more than 325 million chronic carriers worldwide [4]
The targeted release of oral vaccine antigens into the human intestine and vaccine protection efficacy are among the other challenges encountered in edible vaccine development [25]. Another significant disadvantage regarding the production of oral vaccines is the yield of recombinant antigens, which varies considerably depending on the characteristics of the candidate antigen, the nature and biomass of the edible plant host, protein stability, and the technology utilized
Summary
Vaccination is the primary and most effective tool in combating infectious diseases in both humans and animals; the success of immunization critically depends on achieving a broad level of coverage, sufficient to interrupt transmission of pathogens [1]. Is characterized by the production of a different set of cytokines such as IL-4, IL-5, IL-6, IL-10, and IL-13, which further support humoral immunity This complex signaling leading to lymphocyte activation may occur in any individual PPs or MLNs, but, depending on the context of antigenic exposure can either trigger antigen-specific humoral and cellular immune responses or be oriented to immune tolerance, another major drawback of oral vaccination [12,13] (Figure 1). The targeted release of oral vaccine antigens into the human intestine and vaccine protection efficacy are among the other challenges encountered in edible vaccine development [25] Another significant disadvantage regarding the production of oral vaccines is the yield of recombinant antigens, which varies considerably depending on the characteristics of the candidate antigen, the nature and biomass of the edible plant host, protein stability, and the technology utilized (i.e., transient expression or stable chloroplast transformation). International efforts in conducting more clinical studies and sharing the data and outcomes from the clinical trials of oral vaccines are of importance for the future development of oral plant vaccines against viral infections such as HBV and HCV [18,33]
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