Hepatitis E virus (HEV) is one of the leading causes of acute viral hepatitis. Transmission of HEV mainly occurs via the fecal-oral route (ingesting contaminated water or food) or by contact with infected animals and their raw meat products. Some animals, such as pigs, wild boars, sheep, goats, rabbits, camels, rats, etc., are natural reservoirs of HEV, which places people in close contact with them at increased risk of HEV disease. Although hepatitis E is a self-limiting infection, it could also lead to severe illness, particularly among pregnant women, or chronic infection in immunocompromised people. A growing number of studies point out that HEV can be classified as a re-emerging virus in developed countries. Preventative efforts are needed to reduce the incidence of acute and chronic hepatitis E in non-endemic and endemic countries. There is a recombinant HEV vaccine, but it is approved for use and commercially available only in China and Pakistan. However, further studies are needed to demonstrate the necessity of applying a preventive vaccine and to create conditions for reducing the spread of HEV. This review emphasizes the hepatitis E virus and its importance for public health in Europe, the methods of virus transmission and treatment, and summarizes the latest studies on HEV vaccine development.

Plants are increasingly used for the production of high-quality biological molecules for use as pharmaceuticals and biomaterials in industry. Plants have proved that they can produce life-saving therapeutic proteins (Elelyso™—Gaucher’s disease treatment, ZMapp™—anti-Ebola monoclonal antibodies, seasonal flu vaccine, Covifenz™—SARS-CoV-2 virus-like particle vaccine); however, some of these therapeutic proteins are difficult to bring to market, which leads to serious difficulties for the manufacturing companies. The closure of one of the leading companies in the sector (the Canadian biotech company Medicago Inc., producer of Covifenz) as a result of the withdrawal of investments from the parent company has led to the serious question: What is hindering the exploitation of plant-made biologics to improve health outcomes? Exploring the vast potential of plants as biological factories, this review provides an updated perspective on plant-derived biologics (PDB). A key focus is placed on the advancements in plant-based expression systems and highlighting cutting-edge technologies that streamline the production of complex protein-based biologics. The versatility of plant-derived biologics across diverse fields, such as human and animal health, industry, and agriculture, is emphasized. This review also meticulously examines regulatory considerations specific to plant-derived biologics, shedding light on the disparities faced compared to biologics produced in other systems.

Plant viruses have traditionally been studied as pathogens in the context of understanding the molecular and cellular mechanisms of a particular disease affecting crops. In recent years, viruses have emerged as a new alternative for producing biological nanomaterials and chimeric vaccines. Plant viruses were also used to generate highly efficient expression vectors, revolutionizing plant molecular farming (PMF). Several biological products, including recombinant vaccines, monoclonal antibodies, diagnostic reagents, and other pharmaceutical products produced in plants, have passed their clinical trials and are in their market implementation stage. PMF offers opportunities for fast, adaptive, and low-cost technology to meet ever-growing and critical global health needs. In this review, we summarized the advancements in the virus-like particles-based (VLPs-based) nanotechnologies and the role they played in the production of advanced vaccines, drugs, diagnostic bio-nanomaterials, and other bioactive cargos. We also highlighted various applications and advantages plant-produced vaccines have and their relevance for treating human and animal illnesses. Furthermore, we summarized the plant-based biologics that have passed through clinical trials, the unique challenges they faced, and the challenges they will face to qualify, become available, and succeed on the market.

(1) Background: Hepatitis E virus (HEV) is a causative agent of acute viral hepatitis, predominantly transmitted by the fecal–oral route. In developed countries, HEV is considered to be an emerging pathogen since the number of autochthonous cases is rising. Hepatitis E is a viral disease with a proven zoonotic potential for some of its genotypes. The main viral reservoirs are domestic pigs and wild boar. Consumption of undercooked meat, as well as occupational exposure, are key factors for the spread of HEV. In order to evaluate the risks of future viral evolution, a detailed examination of the ecology and distribution of the virus is needed. The aim of the present study is to investigate the prevalence of anti-HEV IgG Ab in domestic pigs and wild boar in Bulgaria; (2) Methods: In this study, during the period of three years between 2017 and 2019, 433 serum samples from 19 different pig farms and 1 slaughterhouse were collected and analyzed. In addition, 32 samples from wild boar were also collected and analyzed during the 2018–2019 hunting season. All samples were analyzed by commercial indirect ELISA; (3) Results: Overall, HEV seroprevalence was 60% (95% CI 42.7–77.1) in domestic pigs and 12.5% (4/32) in wild boar. The observed seroprevalence of the slaughter-aged pigs was 73.65% (95% Cl 58.7–87.3). Prevalence in domestic pigs was significantly higher in the samples collected during 2019 (98% (95% Cl 96.1–99.9)) compared to those collected during 2017 (45.33% (95% CI 2.7–87.3)) and 2018 (38.46% (95% CI 29.1–49.7.); (4) Conclusions: Our findings suggest that domesticated pigs and wild boar might be the reason for the increased HEV transmission across Bulgaria. The genotypic characterization of HEV found in pigs, wild boar and humans will give a more accurate view of the zoonotic transmission of this virus.

The core antigen of hepatitis B virus (HBcAg) is capable of self-assembly into virus-like particles (VLPs) when expressed in a number of heterologous systems. Such VLPs are potential carriers of foreign antigenic sequences for vaccine design. In this study, we evaluated the production of chimeric HBcAg VLPs presenting a foreign epitope on their surface, the 551–607 amino acids (aa) immunological epitope of the ORF2 capsid protein of hepatitis E virus. A chimeric construct was made by the insertion of 56 aa into the immunodominant loop of the HBcAg. The sequences encoding the chimera were inserted into the pEAQ-HT vector and infiltrated into Nicotiana benthamiana leaves. The plant-expressed chimeric HBcHEV ORF2 551–607 protein was recognized by an anti-HBcAg mAb and anti-HEV IgG positive swine serum. Electron microscopy showed that plant-produced chimeric protein spontaneously assembled into “knobbly” ~34 nm diameter VLPs. This study shows that HBcAg is a promising carrier platform for the neutralizing epitopes of hepatitis E virus (HEV) and the chimeric HBcAg/HEV VLPs could be a candidate for a bivalent vaccine.

The Hepatitis E virus (HEV) is a causative agent of acute hepatitis, mainly transmitted by the fecal-oral route or zoonotic. Open reading frame (ORF) 2 encodes the viral capsid protein, which is essential for virion assembly, host interaction, and inducing neutralizing antibodies. In this study, we investigated whether full-length and N- and C-terminally modified versions of the capsid protein transiently expressed in N. benthamiana plants could assemble into highly-immunogenic, virus-like particles (VLPs). We also assessed whether such VLPs can act as a carrier of foreign immunogenic epitopes, such as the highly-conserved M2e peptide from the Influenza virus. Plant codon-optimized HEV ORF2 capsid genes were constructed in which the nucleotides coding the N-terminal, the C-terminal, or both parts of the protein were deleted. The M2e peptide was inserted into the P2 loop after the residue Gly556 of HEV ORF2 protein by gene fusion, and three different chimeric constructs were designed. Plants expressed all versions of the HEV capsid protein up to 10% of total soluble protein (TSP), including the chimeras, but only the capsid protein consisting of aa residues 110 to 610 (HEV 110–610) and chimeric M2 HEV 110–610 spontaneously assembled in higher order structures. The chimeric VLPs assembled into particles with 22–36 nm in diameter and specifically reacted with the anti-M2e antibody.