Brent Cornell

      
Gene therapy is the insertion of genes into an individual’s cells to treat hereditary diseases by replacing defective alleles

• It differs from standard transgenic practices in that it is intended to transform existing organisms rather than create new ones
• Viral vectors are typically used, due to their ability to integrate DNA into the host’s genome
• The process involves removing cells from a patient and using a viral vector to introduce a functional copy of the defective gene
• When the cells are transplanted back into the patient, they should begin expressing the missing protein to restore normal health 

Overview of Gene Therapy

      
Severe combined immunodeficiency (SCID) is a genetic disorder caused by the absence of functional T lymphocytes

• This impairs the adaptive immune system and prevents antibody production, resulting in a deficient immune response
• Individuals with SCID are unable to respond to trivial infections and opportunistic infections can prove to be fatal

SCID is commonly caused by an autosomal recessive condition known as adenosine deaminase (ADA) deficiency

• This condition results from an inability to produce the enzyme ADA, which is needed to safely break down a toxic chemical
• Immature lymphocytes are particularly susceptible to this toxic chemical and consequently fail to mature (leading to SCID)
• Individuals who have undergone gene therapy have shown steady increases in cellular ADA levels following the procedure