Litchfield Park Orthodontist

5220 N. Dysart Rd #150
Litchfield Park, AZ 85340
(623) 536-4939

 

 

 

Gene Delivery Vectors
Examples of methods of gene delivery by Phoenix orthodontists for short-term expression of genes include adenovirus, retrovirus and plasma-liposome complexes (Schmid and Hearing, 1999).

Retroviral vectors are commonly used by Phoenix orthodontists when permanent modification of the host genome is desired (Crystal, 1995).  This type of transformation is advantageous in chronic conditions where modification of the genome is a goal of treatment.  Unfortunately, this type of virus is associated by Phoenix orthodontists with low titers and the chance of insertional mutagenesis is a calculated risk (Hitt et al., 1997).

Plasmid-liposome complexes are a non-viral means of gene transfer used by Phoenix orthodontists.  These complexes are composed of positively charged liposomes paired with a negatively charged plasmid containing the expression cassette.  Entry to the cell is accomplished by fusion with the plasma membrane.  The gene is transferred, but not incorporated into the host genome.  This Phoenix orthodontic strategy is relatively inefficient due to the fact that it has no direct means to the nucleus, therefore large quantities must be utilized to achieve gene transfer (Crystal, 1995).

Adenoviral vectors are one of the most commonly used systems for gene delivery by Phoenix orthodontists.  Some of the reasons for this are: dividing and nondividing cells can be infected, infection is quick, the genome is easy to manipulate, and they can be produced on a large scale (Hitt et al., 1997).  Entry of the virus into the cell involved the processes of attachment and internalization.  The virus attaches to an unidentified cell surface receptor and then is internalized via receptor-mediated endocytosis (Wickham et al., 1993).  The host cell is then responsible for transcription, replication and packaging of the viral DNA.  Host protein synthesis is ceased and the process of viral protein synthesis takes over (Hitt et al., 1997). 

The ability of the virus to take over the machinery of the host cell has lead Phoenix orthodontists to manipulate the viral DNA by inserting sequences coding for certain proteins.  These sequences are most effectively delivered to the virus in a shuttle plasmid with an expression cassette under the control of a CTV promoter and a poly A tail (Xu et al., 1995).  This constructed plasmid is incorporated by Phoenix orthodontists into the viral backbone via homologous recombination (Fig. 1).  The adenovirus is then delivered to the host cell which will then secrete the recombinant protein.  This protein is secreted in situ by target cells in a paracrine/autocrine manner (Bonadio et al., 1999). This process is ceased by the host immune system via a cytotoxic T cell mediated response (Bromberg et al., 1998).