Retrovirus (RV) as a vector, Rapid Inactivations, Synthetic particles, Matrix Protein, Helper systems, Liposomes

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Gene Theraphy
Gene Theraphy Introduction
Human Diseases Targeted for Gene Therapy
Some Human Diseases Targeted for gene therapy
Vectors and Other Delivery Systems for Gene therapy
Viruses as vectors
Retrovirus (RV) as a vector
Adenovirus (AV) as a vector
Adeno associated virus (AAV) as a vector
Lentiviruses as a vector
Non-viral DNA delivery systems
Synthetic particles as vectors
Transient Expression for gene therapy
Splicesome mediated trans-RNA splicing (SMART)
Ex Vivo vs In Vivo Gene Therapy
Target Tissue of Choice for Gen-Delivery System

Retrovirus (RV) as a Vector.
Among the vectors, the most widely used vector is retrovirus, because it can introduce genes into a single active region of the chromatin, thus making it a permanent part of the genome for long term expression. However, there are a number of problems associated with the use of retroviruses as vectors

Features			Viral vectors			Non-viral vectors
	RV	AV	HV	PV	AAV	Mol.conj	Transfection	Liposomes
Insert capacity (kb)	8	7-8	720	725	4.5	-	-	-
Integrates	Yes	No	No	No	No	No	No/rare	No
Oncogenic	Yes	Yes	?	?	?	?	?	?
Viral proteins expressed	No	Yes	Yes	Yes	Yes	No	No	No
In vivo delivery

but solutions to some of these problems have been found. Significant improvements have actually been made in retroviral vectors through incorporation of synthetic and heterologous components

Major problems with retroviral (MOMLV) vector and possible solution

Problem	Solution
1. Regeneration of replication component retrovirus during vector production	1. Replace murine cells with human helper cells: replace MLV vector with non-homologous vectors
2. Insert size limited to ~ 8 kb	2. Use synthetic particles or MAS vectors
3. Rapid inactivation in vitro	3. Modify helper cells, gag and env genes; use synthetic particles/conjugate liposomes
4. Infect only dividing cells	4. Ad HIV matrix protein gene to helper systems