Expression and purification of biologically active bovine Interferon λ3 (IL28B) in Pichia pastoris

Antiviral activity of mink interferon alpha expressed in the yeast Pichia pastoris

Many viruses can cause infections in mink, including canine distemper virus, mink enteritis virus, and Aleutian disease virus. Current treatments are ineffective, and these infections are often fatal, causing severe economic losses. As antiviral drugs may effectively prevent and control these infections, recent research has increasingly focused on antiviral interferons. Herein, the gene encoding a mature mink interferon alpha (MiIFN-α) was synthesized according to the P. pastoris preference of codon usage and a recombinant plasmid, pPICZαA-MiIFN-α, was constructed. pPICZαA-MiIFN-α was linearized and transformed into the P. pastoris X33 strain, and zeocin-resistant transformants were selected. Protein expression was induced by methanol. SDS-PAGE and western blot analyses showed that a 25-kDa fusion protein was expressed in the culture supernatant. Antiviral activity of the expressed protein was determined using cytopathic effect inhibition (CPEI). The purified MiIFN-α significantly inhibited the cytopathic effect of vesicular stomatitis virus with a green fluorescent protein (VSV-GFP) in F81 feline kidney cells, with an antiviral activity of 6.4 × 10⁷ IU/mL; it also significantly inhibited MEV replication in F81 cells. MiIFN-α antiviral activity against VSV-GFP was significantly reduced on treatment with pH 4 and pH 10 conditions for 24 h (p < 0.01). Serum MiIFN-α concentrations in rat were measured using enzyme-linked immune-sorbent assay; MiIFN-α concentrations in rat serum peaked at ~36 h after injection. A high dose of MiIFN-α was safe for use. There were no significant differences in body temperature, tissue changes, and lymphocyte, total white blood cell, and central granulocyte counts between the injected and control groups (p > 0.05). These findings lay a foundation for the large-scale production of recombinant MiIFNs.

Boosting expression level of plectasin in recombinant Pichia pastoris via 2A self-processing peptide assembly

Plectasin is a promising and potent antimicrobial peptide isolated from the fungus Pseudoplectania nigrella which has been heterologously expressed in various hosts. In this study, a four-copy cassette of plectasin was constructed via 2A peptide assembly to further increase its expression level in recombinant Pichia pastoris. The yeast transformant 4Ple-61 harboring four-copy cassette of plectasin could secrete 183.2 mg/L total protein containing 60.8% of plectasin at the flask level within 120 h, which was 2.3 times higher than that of the yeast transformant Ple-6 carrying one-copy cassette of plectasin. Western blot confirmed the significant peptide expression level in the transformant 4Ple-61. Furthermore, it yielded as high as 426.3 mg/L total protein within 120 h during a 5-L fermentation. The purified plectasin shows superior stability and good antimicrobial activity against conventional Staphylococcus aureus ATCC 26,001 and some food-borne antibiotic-resistant S. aureus strains with the MICs ranging from 8 to 32 μg/mL. Therefore, the strategy based on 2A peptide assembly can enhance the expression of plectasin and further expand its application prospect. KEY POINTS: • A yeast transformant 4Ple-61 with four-copy cassette of plectasin was constructed. • The plectasin level yield by the transformant 4Ple-61 was boosted by 2.3 times. • The plectasin showed good activity against food-borne antibiotic-resistant S. aureus.

An effective combination of codon optimization, gene dosage, and process optimization for high-level production of fibrinolytic enzyme in Komagataella phaffii (Pichia pastoris)

BACKGROUND

As a main drug for diseased thrombus, some clinically used thrombolytic agents have various disadvantages, safer novel thrombolytic agents are of great demand. This study aimed to achieve high and efficient production of a fibrinolytic enzyme with superior enzymatic properties, by a combination strategy of codon optimization, gene dosage and process optimization in Komagataella phaffii (K. phaffii).

RESULTS

After codon optimization, the fibase from a marine Bacillus subtilis was expressed and secreted in K. phaffii GS115. Recombinant strains harboring different copies of the fib gene (fib-nc) were successfully obtained via Geneticin (0.25-4 mg/ml) screening on minimal dextrose selection plates and assessment via real-time quantitative PCR. The respective levels of fibase produced by strains expressing fib-5.4c, fib-6c, fib-8c, fib-9c, and fib-12c were 4428, 5781, 7323, 7930, and 2472 U/ml. Levels increased as the copy number increased from 4 to 9, but decreased dramatically at copy number 12. After high cell density fermentation optimization, the highest fibase activity of the strain expressing fib-9c was 7930 U/ml in a shake flask and increased to 12,690 U/ml after 3 days of continuous culture in a 5-L fermenter, which is one of the highest levels of production reported. The recombinant fibase was maximally active at pH 9.0 and 45 °C, and was remarkably stable at pH levels ranging from 5 to 10 and temperatures up to 50 °C. As a metal-dependent serine protease, fibase did not cause hemolysis in vitro and preferentially degraded fibrin directly.

CONCLUSIONS

The combination of codon optimization, gene dosage, and process optimization described herein could be used for the expression of other therapeutic proteins difficult to express. The characteristics of the recombinant fibase suggest that it has potential applications for thrombosis prevention and therapy.

Association between IL28B Polymorphisms and Outcomes of Hepatitis B Virus Infection: A meta-analysis

BACKGROUND

Interleukin (IL) 28B polymorphisms encoding pro-inflammatory and anti-inflammatory cytokines trigger diverse clinical outcome of hepatitis virus infection. However, there is controversy concerning the association of IL28B polymorphisms with the outcome of hepatitis B virus (HBV) infection, with several studies obtaining inconsistent results. We performed a meta-analysis to evaluate the role of 3 single nucleotide polymorphisms (SNPs) rs12979860, rs12980275 and rs8099917 in the progression of HBV infection, overall and by ethnicity.

METHODS

Searched PubMed, Embase and Wiley Online Library electronic databases using 'interleukin 28B', 'IL 28B', 'IL 28B polymorphism', 'hepatitis B virus', 'HBV', and performed meta- analysis for rs12979860, rs12980275 and rs8099917 in Asian and Caucasian populations under the dominant recessive and allele model.

RESULTS

Eighteen studies were found in total and used for this meta-analysis, including 5587 cases and 4295 controls. The IL28B polymorphism rs12979860 had no association with HBV persistence (CC vs CT + TT: OR = 0.86, 95% CI = 0.76-1.00; TT vs CT + CC: OR = 1.14, 95% CI = 0.76-1.70; T vs C: OR = 1.03, 95% CI = 0.94-1.13). Similarly, neither rs12980275 nor rs8099917 had associations with HBV persistence (rs12980275 in AA vs AG + AA: OR = 1.15, 95% CI = 0.96-1.38; rs8099917 in TT vs GT + GG: OR = 1.15, 95% CI = 0.96-1.39). There was also no significant association of IL28B polymorphisms with persistent HBV infection in Asians or Chinese. There was no evidence of an association of rs12979860 with the HBV-related hepatocellular carcinoma susceptibility (T vs C: OR = 1.53, 95% CI = 0.96-2.43).

CONCLUSION

IL28B polymorphisms had no association with the outcome of HBV infection overall, nor in the Asians and the Chinese. These 3 SNPs might not be relevant to the development of HBV infection.

In-vivo Activity of IFN-λ and IFN-α Against Bovine-Viral-Diarrhea Virus in a Mouse Model

Bovine-viral-diarrhea virus (BVDV) can cause significant economic losses in livestock. The disease is controlled with vaccination and bovines are susceptible until vaccine immunity develops and may remain vulnerable if a persistently infected animal is left on the farm; therefore, an antiviral agent that reduces virus infectivity can be a useful tool in control programs. Although many compounds with promising in-vitro efficacy have been identified, the lack of laboratory-animal models limited their potential for further clinical development. Recently, we described the activity of type I and III interferons, IFN-α and IFN-λ respectively, against several BVDV strains in-vitro. In this study, we analyzed the in-vivo efficacy of both IFNs using a BALB/c-mouse model. Mice infected with two type-2 BVDV field strains developed a viremia with different kinetics, depending on the infecting strain's virulence, that persisted for 56 days post-infection (dpi). Mice infected with the low-virulence strain elicited high systemic TNF-α levels at 2 dpi. IFNs were first applied subcutaneously 1 day before or after infection. The two IFNs reduced viremia with different kinetics, depending on whether either one was applied before or after infection. In a second experiment, we increased the number of applications of both IFNs. All the treatments reduced viremia compared to untreated mice. The application of IFN-λ pre- and post-infection reduced viremia over time. This study is the first proof of the concept of the antiviral potency of IFN-λ against BVDV in-vivo, thus encouraging further trails for a potential use of this cytokine in cattle.

Production of thermostable endo-1,5-α-L-arabinanase in Pichia pastoris for enzymatically releasing functional oligosaccharides from sugar beet pulp

Sugar beet pulp is an agricultural processing residue that is a rich source of the cell wall polysaccharide arabinan. Functional oligosaccharides, specifically feruloylated arabino-oligosaccharides (FAOs), can be isolated from sugar beet pulp through selective action by endo-arabinanase (glycoside hydrolase family 43). This study aimed to develop yeast (Pichia pastoris) as an efficient, eukaryotic platform to produce a thermophilic endo-1,5-α-L-arabinanase (TS-ABN) for extracting FAOs from sugar beet pulp. Recombinant TS-ABN was secreted into yeast culture medium at a yield of ~ 80 mg/L, and the protein exhibited specific enzyme activity, pH and temperature optimum, and thermostability comparable to those of the native enzyme. Treatment of sugar beet pulp with Pichia-secreted TS-ABN released FAOs recovered by hydrophobic chromatography at 1.52% (w/w). The isolated FAOs averaged seven arabinose residues per ferulic acid, and treatment of T84 human colon epithelial cells significantly increased expression of two key tight junction-related proteins-zonula occludens-1 and occludin-in a dose-dependent manner. This research establishes a biochemical platform for utilizing sugar beet pulp to produce value-added bioproducts with potential nutraceutical applications.