Prediction of recombinant protein production in an insect cell–baculovirus system using a flow cytometric technique

Designing Two Individual AcMNPV Polyhedrin-Plus Bac-to-Bac Expression System in order to Express GFP and CPV-VP2 in Insect Cells

Background: The importance of viral protein-2 (VP2) of canine parvovirus (CPV) in binding to human cancer cells, production of veterinary vaccines and diagnostic kits has motivated several researches on producing this protein. Objectives: Our purpose was to construct recombinant bacmid shuttle vectors expressing VP2 of CPV using Bac-to-Bac baculoviral expression system. Materials and Methods: Mini-Tn7 transposones engineered in pFastBac1 donor vectors were used to construct expression cassettes of GFP and CPV-VP2. The plasmids were transferred into E. coli DH₁₀Bac competent cells. Site-specific transposition of the genes into bacmid was accomplished using helper plasmid. Occurrence of Transposition was confirmed via PCR using specific primers and PUC/M₁₃ universal primers. The recombinant bacmid DNAs were transfected into Sf9 cells using cationic lipids to generate new recombinant baculoviruses expressing GFP and CPV-VP2. GFP and VP2 expressions were evaluated by fluorescence microscopy and western analysis, respectively. Results: Cloning, subcloning and recombination processes of both GFP and VP2 were accomplished and verified. Accuracy of transfection process was confirmed by GFP fluorescence microscopy.VP2 expression was verified by SDS-PAGE and western analysis. Conclusions: Two Bac-to-Bac expression systems were designed to produce recombinant VP2 and GFP in insect cells.

Monitoring of the effects of transfection with baculovirus on Sf9 cell line and expression of human dipeptidyl peptidase IV

Human dipeptidylpeptidase IV (hDPPIV) is an enzyme that is in hydrolase class and has various roles in different parts of human body. Its deficiency may cause some disorders in the gastrointestinal, neurologic, endocrinological and immunological systems of humans. In the present study, hDPPIV enzyme was expressed on Spodoptera frugiperda (Sf9) cell lines as a host cell, and the expression of hDPPIV was obtained by a baculoviral expression system. The enzyme production, optimum multiplicity of infection, optimum transfection time, infected and uninfected cell size and cell behavior during transfection were also determined. For maximum hDPPIV (269 mU mL(-1)) enzyme, optimum multiplicity of infection (MOI) and time were 0.1 and 72 h, respectively. The size of infected cells increased significantly (P < 0.001) after 24 h post infection. The results indicated that Sf9 cell line was applicable to the large scale for hDPPIV expression by using optimized parameters (infection time and MOI) because of its high productivity (4.03 mU m L(-1) h(-1)).

Characterization of viability and proliferation of alginate-poly-L-lysine-alginate encapsulated myoblasts using flow cytometry

Genetically modified cells encapsulated in alginate-poly-L-lysine-alginate (APA) are being developed to deliver therapeutic products to treat a variety of diseases. The characterization of the encapsulated cells thus becomes paramount. This study reports a novel method to assess the viability, granularity and proliferation of encapsulated cells based on flow cytometry. The in vitro viability of encapsulated G8 murine myoblasts secreting canine FVIII (cFVIII) measured by flow cytometry was comparable to the traditional trypan blue exclusion method and both correlated with cFVIII secretion levels. In contrast, after implantation into mice, only viability measured by flow cytometry correlated with cFVIII secretion. Further, flow cytometry analysis of encapsulated cells maintained in vitro and in vivo revealed a greater fraction of granular cells compared to free cells, suggesting that encapsulation influences the morphology (cytoplasmic composition) of cells within APA microcapsules. Interestingly, the proliferation study showed that encapsulated cells proliferate faster, on average, and were more heterogeneous in vivo compared to in vitro culture conditions, suggesting that encapsulated cell proliferation is complex and environment-dependent. In conclusion, we show that flow cytometry analysis allows for a more consistent and comprehensive examination of encapsulated cells to aid in the development of cell therapy protocols.

Getting more from cell size distributions: establishing more accurate biovolumes by estimating viable cell populations

Current approaches for cell size distribution modeling are attempting to describe the behavior of the entire distribution with respect to time. Although some advances have been made in this area, the modeling process requires a large number of culture-specific parameters and an a priori assumption of the distribution nature (Poisson, Gaussian, etc.). In this work, we propose a deconvolution of the distribution into size ranges and an iterative regression process with respect to a single culture variable, such as viability. Following this approach, two example applications are outlined using data collected with a Coulter Counter Multisizer. In the first, traditional biovolume measurements are corrected to account for the noneven distribution of nonviable cells. These corrections amount to an average increase of 7-65% in the calculated biovolume from 24 to 72 h postinfection and are expected to aid in the development of a new basis for nutrient consumption postinfection. In the second example, viability is predicted from the cell size distribution using both linear and exponential regressions. Differences between predicted and measured viabilities were found to be normally distributed with means of 0.4% and 0% as well as standard deviations of 7.6% and 8.1% for linear and exponential regression, respectively. Although only viability relationships were tested, our approach yielded significant results for both applications, allowing the possibility for further development.