Characterization of an immunomodulatory Der p 2-FIP-fve fusion protein produced in transformed rice suspension cell culture

Effect of combination treatment with Lactobacillus rhamnosus and corticosteroid in reducing airway inflammation in a mouse asthma model

BACKGROUND

Asthma is a complex multifactorial chronic airway inflammatory disease with diverse phenotypes and levels of severity and is associated with significant health and economic burden. In a certain population of asthma patients, the symptoms cannot be well controlled with steroid. There has been long standing interest in the use of probiotics for treating allergic diseases. The purpose of this study is to investigate whether the combination of Lactobacillus rhamnosus GG (LGG) with prednisolone could reduce the dosage of glucocorticoid in controlling airway inflammation in a murine model for allergic asthma.

MATERIAL AND METHODS

We used Der p 2-sensitized asthma model in female BALB/c mice. The animals were treated with 75 μl or 50 μl oral prednisolone or combination treatment of these two doses of oral prednisolone with LGG. Airway hyperresponsiveness, serum specific IgE/IgG1/IgG2a, infiltrating inflammatory cells in lung and cytokines were assessed.

RESULTS

Compared to 75 μl prednisolone, a lower dose of prednisolone with 50 μl was less satisfactory in suppressing airway hyperresponsives, serum IgE and IgG1, Th2 cytokines and inflammatory cytokines such as IL-6, IL-8 and IL-17 as well as infiltrating inflammatory cells. However, combination of 50 μl prednisolone and LGG decreased airway resistance and serum IgE and IgG1, inhibited the production of IL-4, IL-5, IL-6, IL-8, IL-13 and IL-17, upregulated serum IgG2a and enhanced Th1 immune response.

CONCLUSIONS

LGG may reduce the dosage of prednisolone and thus may be beneficial in the treatment of asthma.

Plant Platforms for Efficient Heterologous Protein Production

Production of recombinant proteins is primarily established in cultures of mammalian, insect and bacterial cells. Concurrently, concept of using plants to produce high-value pharmaceuticals such as vaccines, antibodies, and dietary proteins have received worldwide attention. Newer technologies for plant transformation such as plastid engineering, agroinfiltration, magnifection, and deconstructed viral vectors have been used to enhance the protein production in plants along with the inherent advantage of speed, scale, and cost of production in plant systems. Production of therapeutic proteins in plants has now a more pragmatic approach when several plant-produced vaccines and antibodies successfully completed Phase I clinical trials in humans and were further scheduled for regulatory approvals to manufacture clinical grade products on a large scale which are safe, efficacious, and meet the quality standards. The main thrust of this review is to summarize the data accumulated over the last two decades and recent development and achievements of the plant derived therapeutics. It also attempts to discuss different strategies employed to increase the production so as to make plants more competitive with the established production systems in this industry.

Current Understanding of the Structure and Function of Fungal Immunomodulatory Proteins

Fungal immunomodulatory proteins (FIPs) are a group of proteins found in fungi, which are extensively studied for their immunomodulatory activity. Currently, more than 38 types of FIPs have been described. Based on their conserved structure and protein identity, FIPs can be classified into five subgroups: Fve-type FIPs (Pfam PF09259), Cerato-type FIPs (Pfam PF07249), PCP-like FIPs, TFP-like FIPs, and unclassified FIPs. Among the five subgroups, Fve-type FIPs are the most studied for their hemagglutinating, immunomodulating, and anti-cancer properties. In general, these small proteins consist of 110–125 amino acids, with a molecular weight of ~13 kDa. The other four subgroups are relatively less studied, but also show a noticeable influence on immune cells. In this review, we summarized the protein modifications, 3-dimensional structures and bioactivities of all types of FIPs. Moreover, structure-function relationship of FIPs has been discussed, including relationship between carbohydrate binding module and hemagglutination, correlation of oligomerization and cytokine induction, relevance of glycosylation and lymphocyte activation. This summary and discussion may help gain comprehensive understanding of FIPs' working mechanisms and scope future studies.

B subunit of cholera toxin fused with VP7 from GCRV (grass carp reovirus) was expressed in E. coli and folds into an active protein

Grass carp reovirus (GCRV) is one of the most serious pathogens threatening grass carp (Ctenopharyngodon idella) production and results in high mortality in China. To obtain a genetically engineered oral vaccine against GCRV, the cholera toxin B subunit (CTB) of Vibrio cholerae was fused to VP7 (CTB-VP7) and transformed into BL21(DE3) for expression. SDS-PAGE and Western blotting showed that the purified rCTB-VP7 fusion protein (rCTB-VP7) was approximately 49.0 kDa. The monomeric nature of rCTB-VP7 through multistage purification showed a binding affinity for GM1, a receptor for biologically active CTB. rCTB-VP7 is not vulnerable to disassembly by SDS but is vulnerable to disassembly by 2-mercaptoethanol. rCTB-VP7 is stable and highly active at room temperature. The binding affinity experiment between rCTB-VP7 and GM1 also confirms the effects of acid and alkalinity in solution on the structure of rCTB-VP7. rCTB-VP7 bound to GM1 with different affinities under different temperatures and pH values. Prokaryotic expression of rCTB-VP7 was characterized by high expression and easy purification and had a strong binding force with GM1 at 37 °C and pH 7.4. Our results suggest that rCTB-VP7 has the potential as an oral vaccine for protection against GCRV in aquaculture.

Expression and active testing of VP7 from GCRV (Grass carp reovirus) fused with cholera toxin B subunit in rice calli

Grass carp reovirus (GCRV) is one of the most serious pathogens threatening grass carp (Ctenopharyngodon idellus) production and results in high mortality in China. VP7 from GCRV is involved in viral infection and could be suitable for developing vaccines for the control of GCRV infection. To obtain a genetically engineered vaccine and a plant-based oral vaccine and to evaluate their immune efficacy as an oral vaccine against GCRV, cholera toxin B subunit (CTB) of Vibrio cholerae fused to VP7 (CTB-VP7) was transformed into BL21(DE3) for expression. SDS-PAGE and Western blotting showed that the purified CTB-VP7 fusion protein (rCTB-VP7) was approximately 49.0 kDa. Meanwhile, CTB-VP7 was transformed into rice callus cells by Agrobacterium tumefaciens-mediated gene transformation. CTB-VP7 was integrated into the nuclear genome by PCR, and mRNA transcripts of CTB-VP7 were detected. ELISA and Western blot analyses revealed that the CTB-VP7 fusion protein (CTB-VP7) could be expressed in rice callus lines. The level of expression was determined to be 1.54% ± 0.43 of the total soluble protein. CTB-VP7 showed a binding affinity for monosialoganglioside(GM1), a receptor for CTB. CTB-VP7 showed a higher affinity towards GM1 compared to rCTB-VP7. CTB-VP7 bonded to GM1 with different affinities under different temperatures. Maximum binding of CTB-VP7 to GM1 was reported to occur within 2 h at 37 °C, and approximately half of the binding affinity remained at 25 °C. Our results suggest that CTB-VP7 could be produced in rice calli, increasing the possibility that edible plants can be employed in mucosal vaccines for protection against GCRV in aquaculture.

Production of BP178, a derivative of the synthetic antibacterial peptide BP100, in the rice seed endosperm

BACKGROUND

BP178 peptide is a synthetic BP100-magainin derivative possessing strong inhibitory activity against plant pathogenic bacteria, offering a great potential for future applications in plant protection and other fields. Here we report the production and recovery of a bioactive BP178 peptide using rice seeds as biofactories.

RESULTS

A synthetic gene encoding the BP178 peptide was prepared and introduced in rice plants. The gene was efficiently expressed in transgenic rice under the control of an endosperm-specific promoter. Among the three endosperm-specific rice promoters (Glutelin B1, Glutelin B4 or Globulin 1), best results were obtained when using the Globulin 1 promoter. The BP178 peptide accumulated in the seed endosperm and was easily recovered from rice seeds using a simple procedure with a yield of 21 μg/g. The transgene was stably inherited for at least three generations, and peptide accumulation remained stable during long term storage of transgenic seeds. The purified peptide showed in vitro activity against the bacterial plant pathogen Dickeya sp., the causal agent of the dark brown sheath rot of rice. Seedlings of transgenic events showed enhanced resistance to the fungal pathogen Fusarium verticillioides, supporting that the in planta produced peptide was biologically active.

CONCLUSIONS

The strategy developed in this work for the sustainable production of BP178 peptide using rice seeds as biofactories represents a promising system for future production of peptides for plant protection and possibly in other fields.

Putting the Spotlight Back on Plant Suspension Cultures

Plant cell suspension cultures have several advantages that make them suitable for the production of recombinant proteins. They can be cultivated under aseptic conditions using classical fermentation technology, they are easy to scale-up for manufacturing, and the regulatory requirements are similar to those established for well-characterized production systems based on microbial and mammalian cells. It is therefore no surprise that taliglucerase alfa (Elelyso®)-the first licensed recombinant pharmaceutical protein derived from plants-is produced in plant cell suspension cultures. But despite this breakthrough, plant cells are still largely neglected compared to transgenic plants and the more recent plant-based transient expression systems. Here, we revisit plant cell suspension cultures and highlight recent developments in the field that show how the rise of plant cells parallels that of Chinese hamster ovary cells, currently the most widespread and successful manufacturing platform for biologics. These developments include medium optimization, process engineering, statistical experimental designs, scale-up/scale-down models, and process analytical technologies. Significant yield increases for diverse target proteins will encourage a gold rush to adopt plant cells as a platform technology, and the first indications of this breakthrough are already on the horizon.

Alleviation of Dermatophagoides microceras-induced allergy by an immunomodulatory protein, FIP-fve, from Flammulina velutipes in mice

Asthma is a major public health concern. Its greatest risk factor is house dust mite (HDM). Dermatophagoides microceras (Der m) is a type of HDM, and in central Taiwan, there is approximately 80% prevalence of sensitization to Der m. FIP-fve is a fungal immunomodulatory protein (FIP) isolated from the fungus Flammulina velutipes, and exhibits anti-inflammatory properties. To investigate whether FIP-fve affects Der m-induced asthma and inflammation, we evaluated hyper-responsiveness (AHR), pathological changes, and cytokines in mice. We demonstrated that oral FIP-fve decreased Der m-induced airway AHR, airway inflammation, cell infiltration, and expression of cytokines in the bronchoalveolar lavage fluid of Balb/c mice. The results of this study suggest that FIP-fve suppresses asthma, inflammation, and respiratory pathogenesis stimulated by Der m. FIP-fve is able to maintain immunomodulatory activity even in simulated gastric fluid and intestinal fluid. FIP-fve could be a safe and stable agent for suppression of allergic asthma.

The modified rice αAmy8 promoter confers high-level foreign gene expression in a novel hypoxia-inducible expression system in transgenic rice seedlings

Expression of α-amylase genes in rice is induced not only by sugar starvation and gibberellin (GA) but also by O2 deficiency. Promoters of two rice α-amylase genes, αAmy3 and αAmy8, have been shown to direct high-level production of recombinant proteins in rice suspension cells and germinated seeds. In the present study, we modified the cis-acting DNA elements within the sugar/GA response complex (SRC/GARC) of αAmy8 promoter. We found that addition of a G box and duplicated TA box leads to high-level expression of αAmy8 SRC/GARC and significantly enhances αAmy8 promoter activity in transformed rice cells and germinated transgenic rice seeds. We also show that these modifications have drastically increased the activity of αAmy8 promoter in rice seedlings under hypoxia. Our results reveal that the G box and duplicated TA box may play important roles in stimulating promoter activity in response to hypoxia in rice. The modified αAmy8 promoter was used to produce the recombinant human epidermal growth factor (hEGF) in rice cells and hypoxic seedlings. We found that the bioactive recombinant hEGF are stably produced and yields are up to 1.8% of total soluble protein (TSP) in transformed rice cells. The expression level of synthetic hEGF containing preferred rice codon usage comprises up to 7.8% of TSP in hypoxic transgenic seedlings. Our studies reveal that the modified αAmy8 promoter can be applicable in establishing a novel expression system for the high-level production of foreign proteins in transgenic rice cells and seedlings under hypoxia.

Production of a chimeric allergen derived from the major allergen group 1 of house dust mite species in Nicotiana benthamiana

Plants are widely accepted as a general platform for the large-scale production of recombinant proteins, which has been demonstrated by the successful expression of various exogenous proteins. Using plants as a bioreactor for mass production of target proteins for vaccines is thought to show the most potential. This study explores whether a chimeric allergen R8, derived from the major allergen group 1 of house dust mites species (Dermatophagoides farinae and Dermatophagoides pteronyssinus), is expressed in tobacco. The highly efficient and useful Tobacco mosaic virus RNA-based overexpression (TRBO) vector was used to investigate expression of the R8 molecule in tobacco by agroinfection. Presence of R8 was detected using SDS-PAGE and Western blotting. Purified allergens were characterized using IgE-binding activity assay and allergen-specific immunotherapy (ASIT) in murine asthmatic models. The recombinant R8 was successfully expressed in tobacco leaves. The pro-peptide was observed in the herbaceous leaf extracts. This protein exhibits properties similar to the parental allergen ProDer f 1 expressed in Escherichia coli or tobacco with respect to IgE immunoreactivity. R8 also rectifies imbalance of TH1/TH2 cells. An herbaceous plant expression system model allows mass production of R8, which might be used in the future for diagnosis of asthma or production of a candidate vaccine for allergen-specific immunotherapy of asthma.

Improving pharmaceutical protein production in Oryza sativa

Application of plant expression systems in the production of recombinant proteins has several advantages, such as low maintenance cost, absence of human pathogens, and possession of complex post-translational glycosylation capabilities. Plants have been successfully used to produce recombinant cytokines, vaccines, antibodies, and other proteins, and rice (Oryza sativa) is a potential plant used as recombinant protein expression system. After successful transformation, transgenic rice cells can be either regenerated into whole plants or grown as cell cultures that can be upscaled into bioreactors. This review summarizes recent advances in the production of different recombinant protein produced in rice and describes their production methods as well as methods to improve protein yield and quality. Glycosylation and its impact in plant development and protein production are discussed, and several methods of improving yield and quality that have not been incorporated in rice expression systems are also proposed. Finally, different bioreactor options are explored and their advantages are analyzed.