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Over the past decade, several high-value proteins have been produced using plant-based transient expression systems. However, these studies exposed some limitations that must be overcome to allow plant expression systems to reach their full potential. These limitations are the low level of recombinant protein accumulation achieved in some cases, and

Over the past decade, several high-value proteins have been produced using plant-based transient expression systems. However, these studies exposed some limitations that must be overcome to allow plant expression systems to reach their full potential. These limitations are the low level of recombinant protein accumulation achieved in some cases, and lack of efficient co-expression vectors for the production of multi-protein complexes. This study report that tobacco Extensin (Ext) gene 3' untranslated region (UTR) can be broadly used to enhance recombinant protein expression in plants. Extensin is the hydroxyproline-rich glycoprotein that constitutes the major protein component of cell walls. Using transient expression, it was found that the Ext 3' UTR increases recombinant protein expression up to 13.5- and 6-fold in non-replicating and replicating vector systems, respectively, compared to previously established terminators. Enhanced protein accumulation was correlated with increased mRNA levels associated with reduction in read-through transcription. Regions of Ext 3' UTR essential for maximum gene expression included a poly-purine sequence used as a major poly-adenylation site. Furthermore, modified bean yellow dwarf virus (BeYDV)-based vectors designed to allow co-expression of multiple recombinant genes were constructed and tested for their performance in driving transient expression in plants. Robust co-expression and assembly of heavy and light chains of the anti-Ebola virus monoclonal antibody 6D8, as well as E. coli heat-labile toxin (LT) were achieved with the modified vectors. The simultaneous co-expression of three fluoroproteins using the single replicon, triple cassette is demonstrated by confocal microscopy. In conclusion, this study provides an excellent tool for rapid, cost-effective, large-scale manufacturing of recombinant proteins for use in medicine and industry.
ContributorsRosenthal, Sun Hee (Author) / Mason, Hugh (Thesis advisor) / Mor, Tsafrir (Committee member) / Chang, Yung (Committee member) / Arntzen, Charles (Committee member) / Arizona State University (Publisher)
Created2012
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Description
Dengue virus infects millions of people every year. Yet there is still no vaccine available to prevent it. Here we use a neutralizing epitope determinant on the dengue envelope (E) protein as an immunogen to be vectored by a measles virus (MV) vaccine. However the domain III (DIII) of the

Dengue virus infects millions of people every year. Yet there is still no vaccine available to prevent it. Here we use a neutralizing epitope determinant on the dengue envelope (E) protein as an immunogen to be vectored by a measles virus (MV) vaccine. However the domain III (DIII) of the dengue 2 E protein is too small to be immunogenic by itself. In order for it to be displayed on a larger particle, it was inserted into the amino terminus of small hepatitis B surface antigen (HBsAg, S) coding sequence. To generate the recombinant MV vector and verify the efficiency of this concept, a reverse genetics system was used where the MV vectors express one or two additional transcription units to direct the assembly of hybrid HBsAg particles. Two types of recombinant measles virus were produced: pB(+)MVvac2(DIII-S,S)P and pB(+)MVvac2(DIII-S)N. Virus recovered from pB(+)MVvac2(DIII-S,S)P was viable. An ELISA assay was performed to demonstrate the expression and secretion of HBsAg. Supernatant from MVvac2(DIII-S,S)P infected cells confirmed that hybrid HBsAg-domain III particles with a density similar to traditional HBsAg particles were released. Characteristics of the subviral particle have been analyzed for the successful incorporation of domain III. The replication fitness of the recombinant MV was evaluated using multi-step growth kinetics and showed reduced replication fitness when compared to the parental strain MVvac2. This demonstrates that viral replication is hindered by the addition of the two inserts into MV genome. Further analysis of MVvac2(DIII-S)N is needed to justify immune response studies in a small animal model using both of the generated recombinant vectors.
ContributorsHarahap, Indira Saridewi (Author) / Reyes del Valle, Jorge (Thesis director) / Hogue, Brenda (Committee member) / Misra, Rajeev (Committee member) / Barrett, The Honors College (Contributor) / T. Denny Sanford School of Social and Family Dynamics (Contributor) / School of Human Evolution and Social Change (Contributor) / School of Life Sciences (Contributor)
Created2014-05
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Description
HIV continues to remain a global health issue, in particular in many low and middle-income countries. The World Health Organization (WHO) estimates that of the nearly 38 million HIV-1 positive individuals, 25% are unaware they are infected. Despite decades of research, a safe and effective preventative vaccine has yet to

HIV continues to remain a global health issue, in particular in many low and middle-income countries. The World Health Organization (WHO) estimates that of the nearly 38 million HIV-1 positive individuals, 25% are unaware they are infected. Despite decades of research, a safe and effective preventative vaccine has yet to be produced. The HIV-1 envelope glycoprotein41 and the Gag structural protein have been identified to be particularly important in HIV-1 transcytosis and cytotoxic lymphocyte response, respectively. Enveloped virus-like particles (VLPs) consisting of Gag and a deconstructed form of glycoprotein (dgp41) comprising the membrane proximal external region (MPER), transmembrane domain and cytoplasmic tail may present a unique and safe way of presenting these proteins in a state mimicking their natural formation. Another form of presenting the immunogenic glycoprotein41, particularly the MPER component, is by presenting it onto the N-terminal of an IgG molecule, thereby creating an IgG fusion molecule. In our lab, both VLPs and IgG fusion molecules are highly expressed and purified within GnGn Nicotiana benthamiana. The results indicated that these recombinant proteins can be assembled properly within plants and can elicit an immune response in mice. This provides a preliminary step in using such Gag/dpg41 VLPs and RIC as present a safe, effective, and inexpensive HIV vaccine.
ContributorsGarcia, Izamar (Author) / Mor, Tsafrir (Thesis director) / Mason, Hugh (Committee member) / Kamzina, Aigerim (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
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Description

Plant-made virus-like particles (VLPs), composed of HIV-1 Gag and deconstructed gp41 proteins, have been shown to be safe and immunogenic in mice. Here, we report the successful production of HIV-1 Gag/dgp41 VLPs in Nicotiana benthamiana, using an enhanced geminivirus-based expression vector. This novel vector results in unique expression kinetics, with

Plant-made virus-like particles (VLPs), composed of HIV-1 Gag and deconstructed gp41 proteins, have been shown to be safe and immunogenic in mice. Here, we report the successful production of HIV-1 Gag/dgp41 VLPs in Nicotiana benthamiana, using an enhanced geminivirus-based expression vector. This novel vector results in unique expression kinetics, with peak protein accumulation and minimal necrosis achieved on day 4 post-infiltration. In comparing various purification strategies, it was determined that a 20% ammonium sulfate precipitation is an effective and efficient method for removing plant proteins and purifying the recombinant VLPs of interest. If further purification is required, this may be achieved through ultracentrifugation. VLPs are a useful platform for a variety of biomedical applications and developing the technology to efficiently produce VLPs in the plant expression system is of critical importance.

ContributorsFleming, Claire (Author) / Mor, Tsafrir (Thesis director) / Mason, Hugh (Committee member) / Kamzina, Aigerim (Committee member) / Barrett, The Honors College (Contributor) / Department of Physics (Contributor) / School of Life Sciences (Contributor)
Created2022-05