Large-scale production of recombinant hepatitis B surface antigen from Pichia pastoris

HBV Vaccines: Advances and Development

Hepatitis B virus (HBV) infection is a global public health problem that is closely related to liver cirrhosis and hepatocellular carcinoma (HCC). The prevalence of acute and chronic HBV infection, liver cirrhosis, and HCC has significantly decreased as a result of the introduction of universal HBV vaccination programs. The first hepatitis B vaccine approved was developed by purifying the hepatitis B surface antigen (HBsAg) from the plasma of asymptomatic HBsAg carriers. Subsequently, recombinant DNA technology led to the development of the recombinant hepatitis B vaccine. Although there are already several licensed vaccines available for HBV infection, continuous research is essential to develop even more effective vaccines. Prophylactic hepatitis B vaccination has been important in the prevention of hepatitis B because it has effectively produced protective immunity against hepatitis B viral infection. Prophylactic vaccines only need to provoke neutralizing antibodies directed against the HBV envelop proteins, whereas therapeutic vaccines are most likely needed to induce a comprehensive T cell response and thus, should include other HBV antigens, such as HBV core and polymerase. The existing vaccines have proven to be highly effective in preventing HBV infection, but ongoing research aims to improve their efficacy, duration of protection, and accessibility. The routine administration of the HBV vaccine is safe and well-tolerated worldwide. The purpose of this type of immunization is to trigger an immunological response in the host, which will halt HBV replication. The clinical efficacy and safety of the HBV vaccine are affected by a number of immunological and clinical factors. However, this success is now in jeopardy due to the breakthrough infections caused by HBV variants with mutations in the S gene, high viral loads, and virus-induced immunosuppression. In this review, we describe various types of available HBV vaccines, along with the recent progress in the ongoing battle to develop new vaccines against HBV.

The advent of plant cells in bioreactors

Ever since agriculture started, plants have been bred to obtain better yields, better fruits, or sustainable products under uncertain biotic and abiotic conditions. However, a new way to obtain products from plant cells emerged with the development of recombinant DNA technologies. This led to the possibility of producing exogenous molecules in plants. Furthermore, plant chemodiversity has been the main source of pharmacological molecules, opening a field of plant biotechnology directed to produce high quality plant metabolites. The need for different products by the pharma, cosmetics agriculture and food industry has pushed again to develop new procedures. These include cell production in bioreactors. While plant tissue and cell culture are an established technology, beginning over a hundred years ago, plant cell cultures have shown little impact in biotechnology projects, compared to bacterial, yeasts or animal cells. In this review we address the different types of bioreactors that are currently used for plant cell production and their usage for quality biomolecule production. We make an overview of Nicotiana tabacum, Nicotiana benthamiana, Oryza sativa, Daucus carota, Vitis vinifera and Physcomitrium patens as well-established models for plant cell culture, and some species used to obtain important metabolites, with an insight into the type of bioreactor and production protocols.

Immunogenicity and safety assessment of a SARS-CoV-2 recombinant spike RBD protein vaccine (Abdala) in paediatric ages 3-18 years old: a double-blinded, multicentre, randomised, phase 1/2 clinical trial (ISMAELILLO study)

Background

COVID-19 in paediatric ages could result in hospitalizations and death. In addition, excluding children from vaccination could turn them into reservoirs of the SARS-COV-2. Safe and effective COVID-19 vaccines are urgently needed for large-scale paediatric vaccination. ISMAELILLO study aimed to evaluate safety and immunogenicity of two strengths of a new recombinant receptor-binding domain (RBD) protein vaccine (Abdala) in paediatric population.

Methods

A double-blinded, multicentre, randomised, phase 1/2 clinical trial was conducted in nine polyclinics in the province of Camagüey, Cuba. Healthy children and adolescents were stratified according to age (3-11 years old, or 12-18 years old) and they were randomly assigned (1:1; block size four) in two dosage level groups of vaccine to receive three intramuscular doses of 25 μg or 50 μg of RBD, 14 days apart. Main safety endpoint was analyzed as the percentage of serious adverse reactions during vaccination up to 28 days after the third dose (Day 56) in participants who received at least one dose vaccination. The primary immunogenicity endpoint assessed was seroconversion rate of anti-RBD IgG antibody at day 56. The immunogenicity outcomes were assessed in the per-protocol population. This trial is registered with Cuban Public Registry of Clinical Trials, RPCEC00000381.

Findings

Between July 15, 2021, and August 16, 2021, 644 paediatric subjects were screened, of whom 592 were enrolled after verifying that they met the selection criteria: firstly 88 were included in Phase 1 of the study and 504 who completed Phase 2. The vaccine was well tolerated. Injection site pain was the most frequently reported local event (143 [8·4%] of 1707 total doses applied), taking place in 66/851 (7·8%) in the 25 μg group and in 77/856 (9·0%) in the 50 μg. The most common systemic adverse event (AE) was headache: 23/851 (2·7%) in the 25 μg group and 19/856 (2·2%) in the 50 μg. Reactogenicity was mild or moderate in severity, represented in 75% of cases by local symptoms, completely resolved in the first 24-48 h. Twenty-eight days after the third dose, seroconversion anti-RBD IgG were observed in 98·2% of the children and adolescents (231/234) for the 50 μg group and 98·7% (224/228) for the 25 μg group without differences between both strength. The specific IgG antibody geometric mean titres (GMT) showed higher titres between participants who received Abdala 50 μg (231·3; 95% CI 222·6-240·4) compared to those who received 25 μg (126·7; 95% CI 121·9-131·7). The mean ACE2 inhibition %, were 59·4% for 25 μg, and for 50 μg, 72·9% (p < 0·01). Both strength elicited neutralising activity against the SARS-CoV-2, specifically (18·3; 95% CI 14·7-22·78) for Abdala 25 μg and (36·4; 95% CI 30·26-43·8) for 50 μg to the selected sample analyzed.

Interpretation

Abdala vaccine was safe and well tolerated at both antigenic strength levels tested in participants aged between 3 and 18 years. Regarding immunogenicity, Abdala Vaccine stimulated the production of specific IgG antibodies against the RBD of SARS-CoV-2 as well as the production of ACE2 inhibition titres and neutralising antibodies (Nab) in children and adolescents.

Funding

Centre for Genetic Engineering and Biotechnology (CIGB), Havana, Cuba.

Determining buffer conditions for downstream processing of VLP-based recombinant hepatitis B surface antigen using multimodal resins in bind-elute and flow-through purification modes

The difficulties in purification of VLP-based recombinant hepatitis B surface antigen (rHBsAg) are mainly emerged from inefficient semi-purification step plus proteins physicochemical properties and these issues make the downstream processing (DSP) very lengthy and expensive. In this study, optimization of rHBsAg (recombinantly-expressed in Pichia pastoris) DSP was performed using selection of buffering conditions in the semi-purification step. In the semi-purification optimization step, up to 73% of the protein impurities were eliminated and the utmost increase in rHBsAg purity (ca. 3.6-fold) was achieved using 20 mM sodium acetate, pH 4.5. By using rHBsAg binding and nonbinding situations obtained from the response surface plot in design of experiments (DOE), additional bind-elute and flow-through purification mode experiments were conducted and rHBsAg with high purity (near 100%) and recovery (> 83%) was achieved. Following assessment of critical quality attributes (i.e., purity, particle size distribution, host cell DNA, host cell protein, secondary structures, specific activity and relative potency), it was indicated that the characteristics of rHBsAg purified by the new DSP were similar or superior to the ones obtained from conventional DSP. The purification performance of the resin was constantly retained (97-100%) and no significant resin damage took place after 10 adsorption-elution-cleaning cycles. The new DSP developed for production of rHBsAg in this study can substitute the conventional one with granting satisfactory target protein quality, long-lasting resin efficacy, shorter and less expensive process. This process may be also employable for purification of both non-VLP- and VLP- based target proteins expressed in the yeast.

A phase 3, randomised, double-blind, placebo-controlled clinical trial evaluation of the efficacy and safety of a SARS-CoV-2 recombinant spike RBD protein vaccine in adults (ABDALA-3 study)

Background

The pandemic of COVID-19 raised the urgent need for safe and efficacious vaccines against SARS-CoV-2. We evaluated the efficacy and safety of a new SARS-CoV-2 virus receptor-binding domain (RBD) vaccine.

Methods

A phase 3, multicentre, randomised, double-blind, placebo-controlled trial was carried out at 18 clinical sites in three provinces of the south-eastern region of Cuba. Subjects (healthy or those with controlled chronic diseases) aged between 19 and 80 years, who gave written informed consent were eligible. Subjects were randomly assigned (1:1, in blocks) to two groups: placebo, and 50 μg RBD vaccine (Abdala). The product was administered intramuscularly, 0.5 mL in the deltoid region, in a three-dose immunization schedule at 0-14-28 days. The organoleptic characteristics and presentations of the vaccine and placebo were identical. All participants (subjects, clinical researchers, statisticians, laboratory technicians, and monitors) remained blinded during the study period. The main endpoint was to evaluate the efficacy of the Abdala vaccine in the prevention of symptomatic COVID-19. The trial is registered with the Cuban Public Registry of Clinical Trials, RPCEC00000359.

Findings

Between March 22 to April 03, 2021, 48,290 subjects were included (24,144 and 24,146 in the placebo and Abdala groups, respectively) in the context of predominant D614G variant circulation. The evaluation of the main efficacy outcomes occurred during May-June 2021, starting at May 3rd, in the context of high circulation of mutant viruses, predominantly VOC Beta. The incidence of adverse reactions for individuals in the placebo and Abdala vaccine groups were 1227/24,144 (5.1%) and 1621/24,146 (6.7%), respectively. Adverse reactions were mostly mild, and from the injection site, which resolved in the first 24-48 h. No severe adverse events with demonstrated cause-effect relationship attributable to the vaccine were reported. Symptomatic COVID-19 disease was confirmed in 142 participants in the placebo group (78.44 incidence per 1000 person-years, 95% confidence interval [CI], 66.07-92.46) and in 11 participants in Abdala vaccine group (6.05 incidence per 1000 person years; 95% CI 3.02-10.82). The Abdala vaccine efficacy against symptomatic COVID-19 was 92.28% (95% CI 85.74-95.82). Moderate/serious forms of COVID-19 occurred in 30 participants (28 in the placebo group and only 2 in the Abdala vaccine group) for a vaccine efficacy of 92.88% (95% CI 70.12-98.31). There were five critical patients (of which four died), all in the placebo group.

Interpretation

The Abdala vaccine was safe, well tolerated, and highly effective, fulfilling the WHO target product profile for COVID-19 vaccines. Those results, along with its immunization schedule and the advantage of easy storage and handling conditions at 2-8 °C, make this vaccine an option for the use in immunization strategies as a key tool for the control of the pandemic.

Funding

Centre for Genetic Engineering and Biotechnology (CIGB), Havana, Cuba.

How far have we explored fungi to fight cancer?

The use of fungal cultures have been well documented in human history. Although its used in healthcare, like penicillin and statins, have saved countless of lives, but there is still no fungal products that are specifically indicated for cancers. Research into fungal-derived materials to curb cancers in the recent decades have made a considerable progress in terms of drug delivery vehicles, anticancer active ingredients and cancer immunotherapy. Various parts of the organisms have successfully been exploited to achieve specific tasks. Apart from the identification of novel anticancer compound from fungi, its native capsular structure can also be used as drug cargo to achieve higher oral bioavailability. This review summarises the anticancer potential of fungal-derived materials, highlighting the role of capsular polysaccharides, proteins, and other structures in variety of innovative utilities to fit the current pharmaceutical technology. Many bioactive compounds isolated from fungi have also been formulated into nanoparticles to achieve greater anticancer activity. The progress of fungal compounds and their analogues in clinical trials is also highlighted. In addition, the potential of various fungal species to be developed for anticancer immunotherapy are also discussed.

Quantitative assessment of LPS-HBsAg interaction by introducing a novel application of immunoaffinity chromatography

Lipopolysaccharide (LPS), as a stubborn contamination, should be monitored and kept in an acceptable level during the pharmaceutical production process. Recombinant hepatitis B surface antigen (r-HBsAg) is one of the recombinant biological products, which is probable to suffer from extrinsic endotoxin due to its long and complex production process. This research aims to assess the potential interaction between LPS and r-HBsAg by recruiting immunoaffinity chromatography (IAC) as a novel tool to quantify the interaction. Molecular modeling was performed on the HBsAg molecule to theoretically predict its potential binding and interaction sites. Then dynamic light scattering (DLS) analysis was implemented on HBsAg, LPS, and mixtures of them to reveal the interaction. The virus-like particle (VLP) structure of HBsAg and the ribbon-like structure of LPS were visualized by transmission electron microscopy (TEM). Finally, the interaction was quantified by applying various LPS/HBsAg ratios ranging from 1.67 to 120 EU/dose in the IAC. Consequently, the LPS/HBsAg ratios in the eluate were measured from 1.67 to a maximum of 92.5 EU/dose. The results indicated that 77 to 100% of total LPS interacted with HBsAg by an inverse relationship to the incubated LPS concentration. The findings implied that the introduced procedure is remarkably practical in the quantification of LPS interaction with a target recombinant protein.

Production of Single-Domain Antibodies in Pichia pastoris

Single-domain antibodies (sdAbs) are binders that consist of a single immunoglobulin domain. SdAbs have gained importance as therapeutics, diagnostic reagents, and research tools. Functional sdAbs are commonly produced in Escherichia coli, which is a simple and widely used host for production of recombinant proteins. However, there are drawbacks of the E. coli expression system, including the potential for misfolded recombinant proteins and pyrogenic contamination with toxic lipopolysaccharides. Pichia pastoris is an alternative host for the production of heterologous proteins because of its high recombinant protein yields and the ability to produce soluble, properly folded proteins without lipopolysaccharide contamination. Here, we describe a method to produce sdAbs in P. pastoris. We present methods for the cloning of sdAb-encoding genes into a P. pastoris expression vector, production and purification of sdAbs, and measurement of sdAb-binding kinetics. Functional sdAbs are easily and routinely obtained using these methods.

Evaluation of Cell-Penetrating Peptides as Mucosal Immune Enhancers for Nasal Vaccination

Cell-penetrating peptides (CPPs) have been evaluated as enhancers in drug delivery, their addition in medical formulations favors drug absorption allowing obtaining the pharmacological effect with lower doses. In vaccine formulations their inclusion has been also explored with interesting results. Currently mucosal vaccination constitutes a promising alternative with the main advantage of inducing both systemic and mucosal immune responses, which are crucial for control tumors and infections at mucosal tissues. In the present work the nasal immune-enhancing effect of four CPPs was evaluated in Balb/c mice. Animals were intranasally immunized with CPP and the recombinant hepatitis B surface protein (HBsAg) as model antigen. The antibody response in sera and mucosal tissue was measured by ELISA. The IFN-γ secretion response at spleen was also evaluated by ELISPOT and ELISA. Among the CPPs studied one novel peptide stand out by its ability to potentiate the humoral and cellular immune response against the co-administered antigen. Considering that the use of mucosal routes is a promising strategy in vaccination, which are gaining special relevance nowadays in the development of novel candidates against SARS-CoV-2 and other potential emerging respiratory virus, the searching and development of safe mucosal adjuvants constitute a current need.

Contribution of yeast models to virus research

Abstract

Time and again, yeast has proven to be a vital model system to understand various crucial basic biology questions. Studies related to viruses are no exception to this. This simple eukaryotic organism is an invaluable model for studying fundamental cellular processes altered in the host cell due to viral infection or expression of viral proteins. Mechanisms of infection of several RNA and relatively few DNA viruses have been studied in yeast to date. Yeast is used for studying several aspects related to the replication of a virus, such as localization of viral proteins, interaction with host proteins, cellular effects on the host, etc. The development of novel techniques based on high-throughput analysis of libraries, availability of toolboxes for genetic manipulation, and a compact genome makes yeast a good choice for such studies. In this review, we provide an overview of the studies that have used yeast as a model system and have advanced our understanding of several important viruses.

Key points

• Yeast, a simple eukaryote, is an important model organism for studies related to viruses.

• Several aspects of both DNA and RNA viruses of plants and animals are investigated using the yeast model.

• Apart from the insights obtained on virus biology, yeast is also extensively used for antiviral development.

Design and development of a simple method for the detection and quantification of residual host cell DNA in recombinant rotavirus vaccine

Rotavirus recombinant vaccine is usually produced in Vero cells. Residual host DNA may reside in the final product and is considered a source of contamination. WHO protocols indicate that biological products should be free of any type of impurity such as nucleic acids, endotoxins, and host cell intermediate materials. Therefore, all recombinant biological therapeutics should be assessed for residual host DNA. In the present study, a sensitive and specific real-time PCR method was developed to detect residual host cell DNA in the final product. The Beta-actin gene of Vero cells was selected to detect residual host cell DNA. One set of primers and a TaqMan probe were designed for the gene using AlleleID 6 software. Real-time PCR reactions were set up, and efficiency of 84% was obtained. The sensitivity and limit of detection of the assay were determined to be 0.176 Fg/μl and 0.044 Fg/μl, respectively. The intra-assay and inter-assay variations were 4.4% and 1.04%, respectively. Furthermore, the specificity and sensitivity of the assay were high enough, and the detection limit was lower than that of the FDA and WHO standards. This indicates that our assay is highly specific and sensitive to detect residual host DNA of Vero cells in the recombinant rotavirus vaccine.

The race for a coronavirus vaccine

The international race to find a preventive vaccine and effective treatments against COVID 19 has been influenced by two fundamental factors. Firstly, by the molecular characterization of the causative virus and the pathology it produces, and secondly, by access to this information, mostly free of charge by the international scientific community causing a synergy to obtain results in such a short time. Several vaccines preparations against Covid19 have entered Phase 3 clinical trials. Although it is uncertain the degree of protection that they will achieve, preliminary data from Phase 1 and 2 trials and studies in animals indicate that they trigger an antiviral immune response without serious side effects. The current formulations include viral vectors, RNA vaccines, inactivated viruses, and recombinant proteins particles. They all have advantages and disadvantages, but only the results of Phase 3 clinical trials will ultimately decide the best candidates for vaccination campaigns. The tremendous impact of the SARS-CoV-2 in our society has triggered an unprecedented effort to find a vaccine to control the pandemic. Billions of dollars have already been invested in multiple vaccination schemes. According to the WHO, more than 170 vaccines were in different phases of development in August 2020. Here is a summary of the advantages and disadvantages of the front runner strategies categorized according to their delivery method.

Assessing virus like particles formation and r-HBsAg aggregation during large scale production of recombinant hepatitis B surface antigen from Pichia pastoris

The aggregation of recombinant proteins in the different stages of purification leads to the loss of a considerable portion of target protein and reduction in the process efficiency. As the active HBsAg used in Hepatitis B vaccine production is in the form of virus-like particle (VLP), therefore the time and stages at which the VLP assembling happened through the process would be important. The aim of this study was to explore the product aggregation during different stages of large scale production of rHBsAg in Pichia pastoris at production unit of the Pasteur Institute of Iran. Dynamic light scattering (DLS) and transmission electron microscopy (TEM), and also size exclusion-high-performance liquid chromatography (SE-HPLC) were carried out on samples taken from each downstream processes steps to determine the rate of VLPs formation as the desired product and the aggregated form at each stage of the purification. Based on the results, it was found that VLPs formation started at the acid precipitation stage and reached up to 80% at the thermal treatment stage. The ultrafiltration, ion exchange chromatography and immunoaffinity chromatography stages were disclosed to have the highest contribution in the formation of VLP (virus like particle) 22 nm.

Yeast-based vaccines: New perspective in vaccine development and application

In presently licensed vaccines, killed or attenuated organisms act as a source of immunogens except for peptide-based vaccines. These conventional vaccines required a mass culture of associated or related organisms and long incubation periods. Special requirements during storage and transportation further adds to the cost of vaccine preparations. Availability of complete genome sequence, well-established genetic, inherent natural adjuvant and non-pathogenic nature of yeast species viz. Saccharomyces cerevisiae, Pichia pastoris makes them an ideal model system for the development of vaccines both for public health and for on-farm consumption. In this review, we compile the work in this emerging field during last two decades with major emphases on S. cerevisiae and P. pastoris which are routinely used worldwide for expression of heterologous proteins with therapeutic value against infectious diseases along with possible use in cancer therapy. We also pointed towards the developments in use of whole recombinant yeast, yeast surface display and virus-like particles as a novel strategy in the fight against infectious diseases and cancer along with other aspects including suitability of yeast in vaccines preparations, yeast cell wall component as an immune stimulator or modulator and present status of yeast-based vaccines in clinical trials.

HBs antigen and mannose loading on the surface of iron oxide nanoparticles in order to immuno-targeting: fabrication, characterization, cellular and humoral immunoassay

Mannosylation of nanovaccine is an appropriate strategy for targeting the mannose receptors on DCs. Here, HBsAg and mannose loaded on the surface of iron oxide nanoparticles to increases HBsAg vaccine potency. Nanoparticles are made by co-precipitation method and bonded to the HBsAg and mannose by chemical bonding. The physicochemical properties of nano-vaccines, their toxicity and antigenicity were determined. The synthesized nano-vaccine showed spherical shape with a mean particle size of 60 nm, a zeta potential of -44 mV, an antigen-binding efficiency of around 100% and for mannose 78%. In vitro release of nanoparticles exhibited about 30% at the first day and about 60% until the third day. SDSPAGE analysis confirmed structural integrity of HBsAg loaded on nanoparticles. The HBsAg-loaded LCMNP and MLCMNP nanoparticles had no toxic effects on HEK293 cell line. The quantification of the intracellular Fe by ICP-OES as a criterion of nano-vaccine uptake revealed mannose intensify uptake of MLCMNP. In addition, mannose in the structure of MLCMNP improved IL-6, TNF-α and IFN-γ (>16 fold) cytokines genes expression by macrophage/dendritic cells after exposure in 12 h. Immunization of experimental mice (subcutaneously, two times with 2-week intervals) with 5 µg of HBsAg loaded on MLCMNP nanoparticles increased specific total IgG and IgG2a/IgG1 ratio. In addition, TNF-α, IL-12, IL-2 and IL-4 cytokines in mannosylated nano-vaccine increased versus nano-vaccine group while lymphocyte proliferation and IFN-γ responses in the targeted nano-vaccine group show a tiny increase versus the nano-vaccine group. The results show that mannosylated nano-vaccine promotes higher level of cellular and humoural immune responses against HBsAg nano-vaccine.

Accurate and cost-effective prediction of HBsAg titer in industrial scale fermentation process of recombinant Pichia pastoris by using neural network based soft sensor

In the current work, the attempt was made to apply best-fitted artificial neural network (ANN) architecture and the respective training process for predicting final titer of hepatitis B surface antigen (HBsAg), produced intracellularly by recombinant Pichia pastoris Mut⁺ in the commercial scale. For this purpose, in large-scale fed-batch fermentation, using methanol for HBsAg induction and cell growth, three parameters of average specific growth rate, biomass yield, and dry biomass concentration-in the definite integral form with respect to fermentation time-were selected as input vectors; the final concentration of HBsAg was selected for the ANN output. Used dataset consists of 38 runs from previous batches; feed-forward ANN 3:5:1 with training algorithm of backpropagation based on a Bayesian regularization was trained and tested with a high degree of accuracy. Implementing the verified ANN for predicting the HBsAg titer of the five new fermentation runs, excluded from the dataset, in the full-scale production, the coefficient of regression and root-mean-square error were found to be 0.969299 and 2.716774, respectively. These results suggest that this verified soft sensor could be an excellent alternative for the current relatively expensive and time-intensive analytical techniques such as enzyme-linked immunosorbent assay in the biopharmaceutical industry.

A novel application of ion exchange chromatography in recombinant hepatitis B vaccine downstream processing: Improving recombinant HBsAg homogeneity by removing associated aggregates

Production of recombinant HBsAg as a main component of the hepatitis B vaccine has already been established in commercial scale. So far, many studies have been performed to optimize the production process of this recombinant vaccine. However, still aggregation and dissociation of rHBsAg virus-like particles (VLPs) are major challenges in downstream processing of this biomedicine. The structural diversity of rHBsAg is dependent on many factors including cell types, molecular characteristics of the expressed recombinant rHBsAg, buffer composition as well as operation condition and specific characteristics of each downstream processing unit. Hence, it is not relatively easy to implement a single strategy to prevent aggregation formation in already established rHBsAg production processes. In this study, we examined the efficacy of weak anion exchange chromatography (IEC)- packed with DEAE Sepharose Fast Flow medium- on isolation of rHBsAg VLPs from aggregated structures. For this purpose, the influence of ionic strength of elution buffer as a key factor was investigated in isolation and recovery of rHBsAg VLPs. The elution buffer with electrical conductivity between 27 and 31 mS/cm showed the best results for removing aggregated rHBsAg based on SEC-HPLC analysis. The results showed that in the selected conductivity range, about 79% of rHBsAg was recovered with purity above 95%. The percentage of rHBsAg VLPs in the recovered sample was between 94% and 97.5% indicating that we could obtain highly homogeneous rHBsAg within the acceptable quality level. The TEM, SDS-PAGE and western blot analysis were also in agreement with our quantitative measurements.

Application of recurrent neural network for online prediction of cell density of recombinant Pichia pastoris producing HBsAg

Artificial neural networking (ANN) seems to be a promising soft sensor for implementing current approaches of quality by design (QbD) and process analytical technologies (PAT) in the biopharmaceutical industry. In this study, we aimed to implement best-fitted ANN architecture for online prediction of the biomass amount of recombinant Pichia pastoris (P. pastoris) - expressing intracellular hepatitis B surface antigen (HBsAg) - during the fed-batch fermentation process using methanol as a sole carbon source. For this purpose, at the induction phase of methanol fed-batch fermentation, carbon evolution rate (CER), dissolved oxygen (DO), and methanol feed rate were selected as input vectors and total wet cell weight (WCW) was considered as output vector for the ANN. The obtained results indicated that after training recurrent ANN with data sets of four fed-batch runs, this toolbox could predict the WCW of the next fed-batch fermentation process at each specified time point with high accuracy. The R-squared and root-mean-square error between actual and predicted values were found to be 0.9985 and 13.73, respectively. This verified toolbox could have major importance in the biopharmaceutical industry since recombinant P. pastoris is widely used for the large-scale production of HBsAg.

Integration of size-exclusion chromatography and ultracentrifugation for purification of recombinant hepatitis B surface antigen: An alternative method for immunoaffinity chromatography

In purification process of recombinant hepatitis B surface antigen (rHBsAg), immunoaffinity chromatography (IAF) is one of the most important and effective steps in rHBsAg purification. However, the buffer composition and the interaction of ligands-rHBsAg often lead to disassembly, deformation, and clumping of a portion of these virus-like particles (VLPs). Besides, the expensive media, variable biospecific ligand density and the possibility of product contamination are other reported drawbacks of using IAF which makes the production process of rHBsAg more challenging. This study investigated the possibility of substituting IAF with purification methods of size-exclusion chromatography (SEC) and ultracentrifugation. In the SEC, the efficacy of rHBsAg purification was examined by four different media in which Toyopearl HW 65S resin demonstrated the best results. By integrating Toyopearl HW 65S resin - with a bed height of 51 cm - and ultracentrifugation process at 47,000 rpm for 48 hr, 95% of protein impurities were removed. Compared to the IAF in rHBsAg production, the purified sample contained a higher percentage of multimeric rHBsAg particles without any noticeable monomer and aggregate forms. The result of this study indicates that the proposed integrated system could be an efficient mild purification alternative for conventional IAF.

Five-year Follow-up of Chronic Hepatitis B Patients Immunized by Nasal Route with the Therapeutic Vaccine HeberNasvac

A novel therapeutic vaccine for chronic hepatitis B (CHB) treatment comprising the recombinant hepatitis B surface (HBsAg) and nucleocapsid (HBcAg) antigens has been developed. Preclinical and clinical trials (CT) evidenced safety and immunogenicity in animal models as well as in phases I, II, and III clinical trials. A phase I CT has conducted in Cuba in 6 CHB patients refractory or incomplete responders to α-IFN. Patients were immunized ten times every two weeks via. nasal spray, with 100 ug HBsAg and 100 ug HBcAg. Clinical efficacy was monitored by assessing the levels of hepatitis B virus deoxyribonucleic acid (HBV DNA), alanine aminotransferase (ALT), HBeAg, and anti-HBeAg seroconversion as well as by qualitative/ quantitative HBsAg serology during this period. After a 5 year follow-up,HBeAg loss was verified in the three HBeAg (+) patients, in two cases with seroconversion to anti-HBeAg. A reduction to undetectable viral load was observed in 5 out of 6 patients, and in two cases HBsAg seroconversion was also detected. ALT increases above the 2X upper limit of normal (ULN) were only detected in HBeAg (+) patients and associated with HBe antigen loss. All patients had stiffness levels below 7.8 KPa by Fibroscan assessment at the end of this period. Although only a few patients were enrolled in this study, it seems that HeberNasvac may maintain some of the therapeutic effects for a prolonged period. How to cite this article: Fernandez G, Sanchez AL, Jerez E, Anillo LE, Freyre F, Aguiar JA, Leon Y, Cinza Z, Diaz PA, Figueroa N, Muzio V, Nieto GG, Lobaina Y, Aguilar A, Penton E, Aguilar JC. Five-year Follow-up of Chronic Hepatitis B Patients Immunized by Nasal Route with the Therapeutic Vaccine HeberNasvac. Euroasian J Hepatogastroenterol, 2018;8(2):133-139.

Increasing vaccine production using pulsed ultrasound waves

Vaccination is a safe and effective approach to prevent deadly diseases. To increase vaccine production, we propose that a mechanical stimulation can enhance protein production. In order to prove this hypothesis, Sf9 insect cells were used to evaluate the increase in the expression of a fusion protein from hepatitis B virus (HBV S1/S2). We discovered that the ultrasound stimulation at a frequency of 1.5 MHz, intensity of 60 mW/cm2, for a duration of 10 minutes per day increased HBV S1/S2 by 27%. We further derived a model for transport through a cell membrane under the effect of ultrasound waves, tested the key assumptions of the model through a molecular dynamics simulation package, NAMD (Nanoscale Molecular Dynamics program) and utilized CHARMM force field in a steered molecular dynamics environment. The results show that ultrasound waves can increase cell permeability, which, in turn, can enhance nutrient / waste exchange thus leading to enhanced vaccine production. This finding is very meaningful in either shortening vaccine production time, or increasing the yield of proteins for use as vaccines.

Design and validation of a new method to detect and quantify residual host cell DNA in human recombinant erythropoietin (rEPO)

During the purification of human recombinant erythropoietin (rEPO) from host cells, residual DNA may remain in final products. This contamination is a risk factor for patients and may result in the inactivation of some tumor suppressor genes or activation of oncogenes if its concentration is more than the standard defined by WHO. Based on WHO's criteria, acceptable level of residual DNA in biopharmaceuticals is less than 10-100 pg/dose. In this study, we have designed a sensitive and specific quantitative real-time polymerase chain reaction (PCR) assay for the detection of residual DNA in human rEPO products. All reported sequences of CHO's GAPDH gene were retrieved from GenBank, and a multiple alignment was performed using Mega 6 software to find conserved regions of the gene. Primers and probe were designed by AlleleID7 software for the highly conserved region. Quantitative real-time PCR showed an R² value more than 0.99 and the efficiency equal to 101% indicating a highly accurate and efficiency of the reaction, respectively. Based on the standard curve, the limit of detection of the assay was determined to be 10 copies/µL (0.00967 fg/µL). In addition, the inter- and intra-assay of the test were determined to be 1.14% and 0.65%, respectively, which are in acceptable range according to the WHO's guidelines.

Development of an in-House TaqMan Real-Time PCR-Based Method to Detect Residual Host Cell DNA in HBV Vaccine

Biological therapeutic products such as recombinant hepatitis B virus (HBV) vaccine, produced by microbial fermentation in complex media, should be evaluated for host cell DNA contamination in purification steps. Eliminating these contaminations increases the efficacy of the vaccine and decreases its side effects. The objective of the present study is to trace the residual host cell DNA (HCD) in recombinant HBV vaccine by developing a TaqMan Real-Time PCR method which is more sensitive, specific, and reproducible than traditional methods such as Picogreen analysis and Threshold DNA assay. Primers and a probe were designed for the most highly conserved regions of Pichia pastoris genome. To determine the specificity of the assay, in addition to performing a BLAST for the primers and the probe in NCBI nucleotide database, 20 different human genomes and 8 bacterial and viral genomes were used. Moreover, serial dilutions of plasmids, from 10(2) to 10(7) copies/μL (from 0.00064 to 6.4 pg/μL), were prepared to find the sensitivity and the limit of detection (LOD) of the assay. Using 28 different genome samples, the specificity of the assay was determined to be 100 %. In addition, the sensitivity and LOD of the method was 0.39 × 10(-5) pg/μL. Moreover, the reproducibility of the assay based on intra- and inter-assay was 1.03 and 1.06 %, respectively. Considering the suitable specificity and sensitivity, ease of use, relatively low cost, and rapidity of the assay, it can be a reproducible and sensitive method to examine recombinant vaccines for P. pastoris residual DNA.

Pulsed ultrasound for enhancing vaccine production

Hepatitis B is an infectious liver disease and vaccination is an effective way to protect individuals. We have applied mechanical wave stimulation to increase protein production. To validate our design, we used Sf9 insect cells to increase antigen fragment fusion protein expression for hepatitis B virus (HBV S1/S2). We discovered that stimulation at a frequency of 1.5 MHz, intensity of 60 mW/cm(2), for a duration of 10 minutes per day increased HBV S1/S2 production by 15%. This finding is very significant for shortening vaccine production time or increasing the yield of proteins for use as vaccines.

Expression and immunogenic characterization of recombinant gp350 for developing a subunit vaccine against Epstein-Barr virus

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that is linked to the development of various malignancies. There is an urgent need for effective vaccines against EBV. EBV envelope glycoprotein gp350 is an attractive candidate for a prophylactic vaccine. This study was undertaken to produce the truncated (codons 1-443) gp350 protein (gp350(1-443)) in Pichia pastoris and evaluate its immunogenicity. The gp350(1-443) protein was expressed as a secretory protein with an N-terminal His-tag in P. pastoris and purified through Ni-NTA chromatography. Immunization with the recombinant gp350(1-443) could elicit high levels of gp350(1-443)-specific antibodies in mice. Moreover, gp350(1-443)-immunized mice developed strong lymphoproliferative and Th1/Th2 cytokine responses. Furthermore, the recombinant gp350(1-443) could stimulate CD4(+) and CD8(+) T cell responses in vaccinated mice. Collectively, these findings demonstrated that the yeast-expressed gp350(1-443) retained strong immunogenicity. This study will provide a useful source for developing EBV subunit vaccine candidates.

Assessing stability and assembly of the hepatitis B surface antigen into virus-like particles during down-stream processing

The hepatitis B surface antigen (HBsAg) is a recombinant protein-based vaccine being able to form virus-like particles (VLPs). HBsAg is mainly produced using yeast-based expression systems, however, recent results strongly suggest that VLPs are not formed within the yeast cells during the cultivation but are formed in a gradual manner during the following down-stream procedures. VLPs are also not detectable during the first down-stream steps including mechanical and EDTA/detergent-assisted cell destruction. Moreover, VLPs are not detectable in the cell lysate treated with polyethylene glycol and colloidal silica. The first VLP resembling structures appear after elution of HBsAg from colloidal silica to which it binds through hydrophobic interaction. These first VLP resembling structures are non-symmetrical as well as heterodisperse and exhibit a high tendency toward cluster formation presumably because of surface exposed hydrophobic patches. More symmetrical and monodisperse VLPs appear after the following ion-exchange and size-exclusion chromatography most likely as the result of buffer changes during these purification steps (toward more neutral pH and less salt). Final treatment of the VLPs with the denaturant KSCN at moderate concentrations with following KSCN removal by dialysis does not cause unfolding and VLP disassembly but results in a re- and fine-structuring of the VLP surface topology.

Generation of hepatitis B virus PreS2-S antigen in Hansenula polymorpha

Despite the long availability of a traditional prophylactic vaccine containing the HBV surface antigen (HBsAg) and aluminum adjuvant, nearly 10% of the population remains unable to generate an effective immune response. Previous studies have indicated that hepatitis B virus (HBV) PreS2-S is abundant in T/B cell epitopes, which induces a stronger immune response than HBsAg, particularly in terms of cytotoxic T lymphocyte (CTL) reaction. In the current study, the HBV PreS2-S gene encoding an extra 26 amino acids (PreS2 C-terminus) located at the N-terminus of HBsAg was cloned into the pVCH1300 expression vector. PreS2-S expressed in the methylotrophic yeast, Hansenula polymorpha, was produced at a yield of up to 250 mg/L. Subsequent purification steps involved hydrophobic adsorption to colloidal silica, ion-exchange chromatography and density ultracentrifugation. The final product was obtained with a total yield of ∼ 15% and purity of ∼ 99%. In keeping with previous studies, ∼ 22 nm viruslike particles were detected using electron microscopy. The generated PreS2-S antigen will be further studied for efficacy and safty in animals.

Purification of hepatitis B surface antigen virus-like particles from recombinant Pichia pastoris and in vivo analysis of their immunogenic properties

Following earlier studies on high-level intracellular production of hepatitis B surface antigen (HBsAg) using recombinant Pichia pastoris, we present here in detail an enhanced method for the purification of recombinant HBsAg virus-like particles (VLPs). We have screened various detergents for their ability to promote the solubilization of recombinant intracellular HBsAg. In addition, we have analyzed the effect of cell disruption and extraction regarding their impact on the release of HBsAg. Our results show that introduction of the mild nonionic detergent Tween 20 in the initial process of cell lysis at ∼600bars by high pressure homogenization leads to the best results. The subsequent purification steps involved polyethylene glycol precipitation of host cell contaminants, hydrophobic adsorption of HBsAg to colloidal silica followed by ion-exchange chromatography and either isopycnic density ultracentrifugation or size exclusion chromatography for the recovery of the VLPs. After final KSCN treatment and dialysis, a total yield of ∼3% with a purity of >99% was reached. The pure protein was characterized by electron microscopy, showing the presence of uniform VLPs which are the pre-requisite for immunogenicity. The intramuscular co-administration of HBsAg VLPs, with either alum or a PEGylated-derivative of the toll-like receptor 2/6 agonist MALP-2, to mice resulted in the elicitation of significantly higher HBsAg-specific IgG titers as well as a stronger cellular immune response compared to mice vaccinated with a gold standard vaccine (Engerix™). These results show that P. pastoris derived HBsAg VLPs exhibit a high potential as a superior biosimilar vaccine against hepatitis B.

Conformational and thermal stability improvements for the large-scale production of yeast-derived rabbit hemorrhagic disease virus-like particles as multipurpose vaccine

Recombinant virus-like particles (VLP) antigenically similar to rabbit hemorrhagic disease virus (RHDV) were recently expressed at high levels inside Pichia pastoris cells. Based on the potential of RHDV VLP as platform for diverse vaccination purposes we undertook the design, development and scale-up of a production process. Conformational and stability issues were addressed to improve process control and optimization. Analyses on the structure, morphology and antigenicity of these multimers were carried out at different pH values during cell disruption and purification by size-exclusion chromatography. Process steps and environmental stresses in which aggregation or conformational instability can be detected were included. These analyses revealed higher stability and recoveries of properly assembled high-purity capsids at acidic and neutral pH in phosphate buffer. The use of stabilizers during long-term storage in solution showed that sucrose, sorbitol, trehalose and glycerol acted as useful aggregation-reducing agents. The VLP emulsified in an oil-based adjuvant were subjected to accelerated thermal stress treatments. None to slight variations were detected in the stability of formulations and in the structure of recovered capsids. A comprehensive analysis on scale-up strategies was accomplished and a nine steps large-scale production process was established. VLP produced after chromatographic separation protected rabbits against a lethal challenge. The minimum protective dose was identified. Stabilized particles were ultimately assayed as carriers of a foreign viral epitope from another pathogen affecting a larger animal species. For that purpose, a linear protective B-cell epitope from Classical Swine Fever Virus (CSFV) E2 envelope protein was chemically coupled to RHDV VLP. Conjugates were able to present the E2 peptide fragment for immune recognition and significantly enhanced the peptide-specific antibody response in vaccinated pigs. Overall these results allowed establishing improved conditions regarding conformational stability and recovery of these multimers for their production at large-scale and potential use on different animal species or humans.

Construction and characterization of virus-like particles: a review

Over the last three decades, virus-like particles (VLPs) have evolved to become a widely accepted technology, especially in the field of vaccinology. In fact, some VLP-based vaccines are currently used as commercial medical products, and other VLP-based products are at different stages of clinical study. Several remarkable advantages have been achieved in the development of VLPs as gene therapy tools and new nanomaterials. The analysis of published data reveals that at least 110 VLPs have been constructed from viruses belonging to 35 different families. This review therefore discusses the main principles in the cloning of viral structural genes, the relevant host systems and the purification procedures that have been developed. In addition, the methods that are used to characterize the structural integrity, stability, and components, including the encapsidated nucleic acids, of newly synthesized VLPs are analyzed. Moreover, some of the modifications that are required to construct VLP-based carriers of viral origin with defined properties are discussed, and examples are provided.

Th2-Th1 shift with the multiantigenic formulation TERAVAC-HIV-1 in Balb/c mice

In chronic HIV infection a progressive Th1 to Th2/Th0 cytokine-profile shift is related to disease progression. One of the possible benefits of a therapeutic vaccination might be to counterbalance this phenomenon to allow viral replication control under a Th1-type immune response. TERAVAC-HIV-1 is a multiantigenic formulation vaccine candidate against HIV-1 which comprises the recombinant protein CR3 that contains T cell epitopes and the surface and nucleocapsid antigens of Hepatitis B Virus (HBV). Previous studies showed that such virus like particles of the HBV provide a Th1 adjuvant effect. The present studies examined the capacity of TERAVAC to elicit a Th1 response in the presence of an ongoing HIV-specific Th2-type response in Balb/c mice. To examine this issue, we injected subcutaneously the animals with CR3 or viral lysate in alum which resulted in a Th2-type response. The CR3-specific Th2-type response was verified by induction of IL-4 and IL-10 secretion in ex vivo stimulated splenocytes without secretion of IFN-γ and IgG2a antibodies in serum. Further subcutaneous and simultaneous subcutaneous-nasal immunizations of the same mice with TERAVAC promoted IFN-γ secretion and production of IgG2a antibodies in accordance with a Th1-type response. This result suggests a therapeutic benefit of this vaccine candidate in the restoration of the Th1-type HIV-specific cellular response in seropositive patients.

Virus-like particles as a highly efficient vaccine platform: diversity of targets and production systems and advances in clinical development

Virus-like particles (VLPs) are a class of subunit vaccines that differentiate themselves from soluble recombinant antigens by stronger protective immunogenicity associated with the VLP structure. Like parental viruses, VLPs can be either non-enveloped or enveloped, and they can form following expression of one or several viral structural proteins in a recombinant heterologous system. Depending on the complexity of the VLP, it can be produced in either a prokaryotic or eukaryotic expression system using target-encoding recombinant vectors, or in some cases can be assembled in cell-free conditions. To date, a wide variety of VLP-based candidate vaccines targeting various viral, bacterial, parasitic and fungal pathogens, as well as non-infectious diseases, have been produced in different expression systems. Some VLPs have entered clinical development and a few have been licensed and commercialized. This article reviews VLP-based vaccines produced in different systems, their immunogenicity in animal models and their status in clinical development.

Enhanced cell disruption strategy in the release of recombinant hepatitis B surface antigen from Pichia pastoris using response surface methodology

BACKGROUND

Cell disruption strategies by high pressure homogenizer for the release of recombinant Hepatitis B surface antigen (HBsAg) from Pichia pastoris expression cells were optimized using response surface methodology (RSM) based on the central composite design (CCD). The factors studied include number of passes, biomass concentration and pulse pressure. Polynomial models were used to correlate the above mentioned factors to project the cell disruption capability and specific protein release of HBsAg from P. pastoris cells.

RESULTS

The proposed cell disruption strategy consisted of a number of passes set at 20 times, biomass concentration of 7.70 g/L of dry cell weight (DCW) and pulse pressure at 1,029 bar. The optimized cell disruption strategy was shown to increase cell disruption efficiency by 2-fold and 4-fold for specific protein release of HBsAg when compared to glass bead method yielding 75.68% cell disruption rate (CDR) and HBsAg concentration of 29.20 mg/L respectively.

CONCLUSIONS

The model equation generated from RSM on cell disruption of P. pastoris was found adequate to determine the significant factors and its interactions among the process variables and the optimum conditions in releasing HBsAg when validated against a glass bead cell disruption method. The findings from the study can open up a promising strategy for better recovery of HBsAg recombinant protein during downstream processing.