A new methanol-feeding strategy for the improved production of β-galactosidase in high cell-density fed-batch cultures of <Emphasis Type="Italic">Pichia pastoris</Emphasis> Mut<Superscript>+</Superscript> strains

Developing novel methanol-feeding strategies for the improved production of heterologous proteins in high cell-density fed-batch cultures of Pichia pastoris has been of great interest during recent years. In this study, a recombinant P. pastoris strain (GS115/His⁺ Mut⁺) producing β-galactosidase (β-Gal) was used to investigate conventional feeding strategies and to develop a new strategy to increase the recombinant protein production during fedbatch cultures on methanol. Three types of conventional methanol-feeding strategies, including μ-stat, dissolved oxygen-stat (DO-stat) and constant methanol concentration were investigated and compared with respect to alcohol oxidase (AOX), formate dehydrogenase (FDH) and β-gal activities, and cell dry weight (CDW), methanol, and formaldehyde concentration variations during the production phase. Methanol feeding with μ-stat 0.025/h exhibited the highest β-gal activity. Supplementing ammonium and magnesium in μ-stat 0.025/h did not affect the cell growth or methanol or formaldehyde concentrations throughout the fermentation but did improved the maximum β-gal activity from 148.2 to 158.1 kU/mL. A new three-step methanol-feeding strategy was developed based on the results obtained from conventional feeding strategies, which started with μ-stat 0.025/h for 5 h, then μ-stat 0.030/h, and finally, was switched to DO-stat when maintaining the DO above 20% air saturation became difficult. Implementation of this new feeding strategy resulted in a CDW of 107.2 ± 0.7 g/L, AOX specific activity of 0.1890 ± 0.0030 U/mg CDW, and β-gal activity of 173.5 ± 2.1 kU/mL after 29 h of fermentation, which shows a 5.6, 29.1, and 15.7% increase in CDW, AOX, and β-gal activity, respectively, compared to that of μ-stat at 0.025/h.     

Drug resistance in Vibrio cholerae strains isolated from clinical specimens

Cholera is a serious epidemic and endemic disease caused by the Gram-negative bacterium Vibrio cholerae. SXT is an integrative conjugation element (ICE) that was isolated from a V. cholerae; it encodes resistance to the antibiotics chloramphenicol, streptomycin and sulfamethoxazole/trimethoprim. One hundred seven V. cholerae O1 strains were collected from cholera patients in Iran from 2005 to 2007 in order to study the presence of SXT constin and antibiotic resistance.The study examined 107 Vibrio cholerae strains isolated from cholera prevalent in some Iranian provinces. Bacterial isolation and identification were carried out according to standard bacteriological methods. Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) to four antibiotics (chloramphenicol, streptomycin, sulfamethoxazole, and trimethoprim) were determined by broth microdilution method. PCR was employed to evaluate the presence of established antibiotic resistance genes and SXT constin using specific primer sets.The resistance of the clinical isolates to sulfamethoxazole, trimethoprime, chloramphenicol, and streptomycin was 97%, 99%, 99%, and 90%, respectively. The data obtained by PCR assay showed that the genes sulII, dfrA1, floR, strB, and sxt element were present in 95.3%, 95.3%, 81.3%, 95.3%, and 95.3% of the V. cholerae isolates.The Vibrio strains showed the typical multidrug-resistance phenotype of an SXT constin. They were resistant to sulfamethoxazole, trimethoprime, chloramphenicol, and streptomycin. The detected antibiotic resistance genes included dfrA for trimethoprim and floR, strB, sulII and int, respectively, for chloramphenicol, streptomycin, sulfamethoxazole, as well as the SXT element.     

Establishing a cGMP pancreatic islet processing facility: the first experience in Iran

It has been predicted that one of the greatest increase in prevalence of diabetes will happen in the Middle East bear in the next decades. The aim of standard therapeutic strategies for diabetes is better control of complications. In contrast, some new strategies like cell and gene therapy have aimed to cure the disease. In recent years, significant progress has occurred in beta-cell replacement therapies with a progressive improvement of short-term and long term outcomes. In year 2005, considering the impact of the disease in Iran and the promising results of the Edmonton protocol, the funding for establishing a current Good Manufacturing Practice (cGMP) islet processing facility by Endocrinology and Metabolism Research Center was approved by Tehran University of Medical Sciences. Several islet isolations were performed following establishment of cGMP facility and recruitment of all required equipments for process validation and experimental purpose. Finally the first successful clinical islet isolation and transplantation was performed in September 2010. In spite of a high cost of the procedure it is considered beneficial and may prevent long term complications and the costs associated with secondary cares. In this article we will briefly describe our experience in setting up a cGMP islet processing facility which can provide valuable information for regional countries interested to establish similar facilities.     

The implementation of tissue banking experiences for setting up a cGMP cell manufacturing facility

Cell manufacturing for clinical applications is a unique form of biologics manufacturing that relies on maintenance of stringent work practices designed to ensure product consistency and prevent contamination by microorganisms or by another patient's cells. More extensive, prolonged laboratory processes involve greater risk of complications and possibly adverse events for the recipient, and so the need for control is correspondingly greater. To minimize the associate risks of cell manufacturing adhering to international quality standards is critical. Current good tissue practice (cGTP) and current good manufacturing practice (cGMP) are examples of general standards that draw a baseline for cell manufacturing facilities. In recent years, stem cell researches have found great public interest in Iran and different cell therapy projects have been started in country. In this review we described the role of our tissue banking experiences in establishing a new cGMP cell manufacturing facility. The authors concluded that, tissue banks and tissue banking experts can broaden their roles from preparing tissue grafts to manufacturing cell and tissue engineered products for translational researches and phase I clinical trials. Also they can collaborate with cell processing laboratories to develop SOPs, implement quality management system, and design cGMP facilities.     

Differentiation of human ES cell-derived neural progenitors to neuronal cells with regional specific identity by co-culturing of notochord and somite

Limitations to the in vivo study of human nervous system development make it necessary to design an in vitro model to evaluate the in vivo effects of surrounding tissues on neurogenesis and regional identity of the human neural plate. Rostral neural progenitors (NPs) were initially generated from adherent human embryonic stem cells (hESCs) in a defined condition and characterized. Then, to find the role of somites (S) and notochords (N) in rostro-caudal (RC) and dorso-ventral (DV) patterning of neuronal cells, NPs were co-cultured with microencapsulated chicken S or N in alginate beads. In this study, N induced more neurogenesis as evaluated by expression of TUJ1 and MAP2-positive cells. Additionally, N induced spinal cord ventral brachiothoracic identity as well as NPs proliferation. We observed a synergic effect on motoneuron induction when S and N were used together. Moreover, S induced hindbrain identity in differentiated neuronal cells from NPs. These results indicate that highly enriched NPs can be generated in an adherent and defined system from hESCs. Moreover, S and N tissues highly influenced neuronal differentiation in point of proliferation, neurogenesis, and RC and DV regional identity. These results indicate a very simple and efficient protocol to mimic in vivo events of human neural development in vitro which is important in the context of developmental neuroscience and cellular replacement therapies.     

A chaperone trap contributes to the onset of cystic fibrosis

Protein folding is the primary role of proteostasis network (PN) where chaperone interactions with client proteins determine the success or failure of the folding reaction in the cell. We now address how the Phe508 deletion in the NBD1 domain of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein responsible for cystic fibrosis (CF) impacts the binding of CFTR with cellular chaperones. We applied single ion reaction monitoring mass spectrometry (SRM-MS) to quantitatively characterize the stoichiometry of the heat shock proteins (Hsps) in CFTR folding intermediates in vivo and mapped the sites of interaction of the NBD1 domain of CFTR with Hsp90 in vitro. Unlike folding of WT-CFTR, we now demonstrate the presence of ΔF508-CFTR in a stalled folding intermediate in stoichiometric association with the core Hsps 40, 70 and 90, referred to as a 'chaperone trap'. Culturing cells at 30 C resulted in correction of ΔF508-CFTR trafficking and function, restoring the sub-stoichiometric association of core Hsps observed for WT-CFTR. These results support the interpretation that ΔF508-CFTR is restricted to a chaperone-bound folding intermediate, a state that may contribute to its loss of trafficking and increased targeting for degradation. We propose that stalled folding intermediates could define a critical proteostasis pathway branch-point(s) responsible for the loss of function in misfolding diseases as observed in CF.     

Acquired immunogenicity of human DNA damaged by N-hydroxy-N-acetyl-4-aminobiphenyl

4-Aminobiphenyl, a known carcinogen, has many environmental sources like cigarette smoke, industrial waste, and so forth. It can be metabolized to form a potent mutagen, N-hydroxy-N-acetyl-4-aminobiphenyl (N-OH-AABP) that undergoes further processing to form electrophilic nitrenium ions which interact with DNA-forming covalent adducts, thereby exerting genotoxic effects. While the mutagenicity of N-OH-AABP has been amply reported, no extensive studies have been performed to assess the immunogenicity of N-OH-AABP-modified DNA. In this study, human placental DNA was modified with N-OH-AABP, and the structural perturbations in the DNA molecule were evaluated by ultraviolet spectroscopy and nuclease S1 digestion. Native and N-OH-AABP-modified DNA were used as antigens for immunizing female rabbits. The modified DNA was found to be highly immunogenic, eliciting high titer immunogen-specific antibodies, while the native form was almost nonimmunogenic. The induced antibodies exhibited wide range of heterogeneity in recognizing various nucleic acid conformers and DNA bases. We also detected deposits of immune complex in glomerular basement membrane in rabbits immunized with N-OH-AABP-DNA. Possible role of N-OH-AABP-DNA in the induction of antibodies in cancer patients and the related consequences have been discussed.     

Evaluation of Anti-Toxoplasma IgG, IgM, and IgA in Mothers with Spontaneous Abortion in Zanjan, Northwest Iran

Toxoplasma gondii is one of the major agents of infectious abortions and due to its worldwide distribution can threat healthy pregnant women who had no previous exposure to this parasite. The present study was designed to investigate the contribution of T. gondii to spontaneous abortions in Zanjan, Northwest of Iran, using ELISA method. Blood Samples were collected from 264 mothers referred to the provincial hospitals of Zanjan due to spontaneous abortion. The sera were isolated and subjected to evaluate the anti-Toxoplasma IgG, IgM and IgA antibodies. The results showed IgG positive (IgG⁺) in 99 cases (37.5%). A total of 68 women (25.8%) showed seroconversion with IgM or IgA or both IgM and IgA. They included: IgM⁺ in 21 (8.0%), IgA⁺ in 23 (8.7%) and both IgM⁺ and IgA⁺ in 24 (9.1%) subjects. In 23 cases, positive titers of IgM and IgG were accompanied. In general, the analysis of anti-Toxoplasma antibody patterns, showed that about 17% of the spontaneous abortions were associated with serological patterns of acute infection. According to these findings, a considerable proportion of spontaneous abortions can be attributed to T. gondii in the study area.     

Anticoccidial activity of herbal complex in broiler chickens challenged with Eimeria tenella

The objective of the present study was to evaluate the anticoccidial effect of different concentrations of the herbal complex of 4 plants (leaves of Azadirachta indica and Nicotiana tabacum, flowers of Calotropis procera and seeds of Trachyspermum ammi) in broiler chickens in comparison with amprolium anticoccidial. Three concentrations (2 g, 4 g and 6 g) of herbal complex were given to the experimental groups once a day and amprolium (at the dose rate of 125 ppm) was given orally in drinking water from the 14th to the 21st days of age. One group was kept as infected, non-medicated control and one as non-infected, non-medicated control. All groups were inoculated orally with 75,000 sporulated oocysts on the 14th day of age except the non-infected, non-medicated control. Among herbal complex medicated groups, the maximum anticoccidial effect was seen in the group medicated with 6 g herbal complex followed by 4 g and 2 g herbal complex medicated groups. Treatment with 6 g of the herbal complex significantly reduced the negative performance and pathogenic effects associated with Eimeria tenella challenge at a level that was comparable with amprolium when using a largely susceptible recent field isolate. In summary, concentration-dependent anticoccidial activity of the studied herbal complex suggests its use as an alternative anticoccidial agent to chemotherapeutic drugs for Eimeria tenella control.     

Analysis of ammonia-oxidizing bacteria dominating in lab-scale bioreactors with high ammonium bicarbonate loading

The ammonia-oxidizing bacterial community (AOB) was investigated in two types of laboratory-scale bioreactors performing partial oxidation of ammonia to nitrite or nitrate at high (80 mM) to extremely high (428 mM) concentrations of ammonium bicarbonate. At all conditions, the dominant AOB was affiliated to the Nitrosomonas europaea lineage as was determined by fluorescence in situ hybridization and polymerase chain reaction in combination with denaturing gradient gel electrophoresis. Molecular analysis of the mixed populations, based on the 16S rRNA and cbbL genes, demonstrated the presence of two different phylotypes of Nitrosomonas, while microbiological analysis produced a single phylotype, represented by three different morphotypes. One of the most striking features of the AOB populations encountered in the bioreactors was the domination of highly aggregated obligate microaerophilic Nitrosomonas, with unusual cellular and colony morphology, commonly observed in nitrifying bioreactors but rarely investigated by cultural methods. The latter is probably not an adaptation to stressful conditions created by high ammonia or nitrite concentrations, but oxygen seems to be a stressful factor in these bioreactors.