à Using a viral or some non-viralvector system enhances the efficiency, yet the immune response activates, andclearance of foreign particle is confirmed.à Alternatively, the DNA whichcontains the targeted transgene is may be injected and manipulated along with theliposomes into the patients. Plasmid DNA can also be targeted using different mechanicalmeans e.g. gene gun. (Klink D et.
al2004)The antibody against viral particles does not permitthe second injection of the viral vector. To reduce the amount of neutralizingantibody generated against vectors, is the current and basic area of research forimproving the vector delivery. In all gene delivery protocols, the requirementof transgene is to cross the cell membrane and to enter in the nucleus.
Thebiggest hurdle is the delivery of transgene into the intracellular compartmenteffectively (G FERRARI et.al. 1991).Many different modifications are suggested for the viral vectors and for the non-viralvectors for targeting the gene into the tissue. For example, VP22, which is aprotein of herpes simplex virus, contains a property of spreading from one cellto another cell, and this attribute has been implemented in designing manyvectors successfully. (Figure 2 General ways of in vivo gene therapy) Classification of vectors for in vivo approach: Viral vectors can be categorized into two main divisions,integrating and non-integrating vectors which are based on their specificrecombination capability to the chromosome of host cell.
Adeno associatedviruses are those, which are known for targeting the genetic material(DNA) tochromosome number 19 of human genome. The genes are incorporated into thechromosome which lead to a stable expression of targeted desired protein.Another type is known as TEMPORARY in which the proteins are expressed for ashort time period only and in this case, the gene is not well integrated ormanipulated with the chromosome.A flowsheet ispresented following to know about the classes of different vectors which areassociated with in vivo somatic cell gene transfer. The sheet is a betterexplanation of theory.
Cystic Fibrosis Treatment with invivo somatic cell gene therapy: Gene therapy has been developed as a unique treatmentfor the patients suffering from cystic fibrosis (CF), which is a condition thathas been widely-researched till now and yet for which no specific kind oftreatment exists that could halt the progression and development of lungdiseases. One way to treat CF is by using gene therapy (somatic cell genetransfer in vivo) which involves the transfer of corrected copies of aregulator named, cystic fibrosis transmembrane conductance regulator (CFTR)gene into the epithelial cells right into the air passage (Burney et.al. 2012).CFTR gene was cloned in 1989 that led toproof-of-principle studies and researches of CFTR gene transfer in vivo and indifferent animal models.
Earliest and basic clinical trials of many CF patientswere performed in 1993 which use both viral and non-viral gene transferringagents in both nasal passage and in other bronchial epithelial epithelium.Disadvantages/Demerits of In vivosomatic cell gene therapy:Along with all the potential uses of in vivo genetherapy, there are also exist some potential disadvantages of in vivo therapywhich are as follows:à the target cell infection is usuallynonspecific.à Many different types of cells havethe chances to be infected during the injecting of in vivo vectors in centralnervous systems e.g. in glia, neurons etc.
à the technique may be proving toxicand cause toxicity of cells.à Some vectors can be proving toxicfor host cells and reduce their immune response effectively.