The Question is from neet-botany biotechnology biotechnological-applications-in-medicine, and it was created by the author D VINOD

Question

A patient exhibits severe combined immunodeficiency (SCID) due to a deficiency in adenosine deaminase (ADA).  Which gene therapy approach is MOST likely to provide a long-term solution?

D VINOD · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
 **Primary Concept**: Gene therapy for SCID
 **Related Topics**: Adenosine deaminase deficiency, hematopoietic stem cells, retroviral vectors, ex vivo and in vivo gene therapy, bone marrow transplant.
 **Prerequisites**: Understanding of gene therapy techniques, SCID pathogenesis, and hematopoietic stem cell biology.
## SOLUTION PATHWAY
**Given Information**:
  Patient has SCID due to ADA deficiency.
  We need to find the most likely long-term solution using gene therapy.
**Method & Steps**:
 1. Analyze each option's potential for long-term efficacy.
  Reasoning:  The goal is to correct the ADA deficiency permanently in a significant population of cells.  This requires targeting cells with long lifespans and high proliferative capacity.
 2. Evaluate the advantages and disadvantages of each approach.
  Working: 
  A. In vivo gene therapy using a retroviral vector directly injected into the bone marrow is less effective because it may not efficiently transduce all relevant cells and the effect might be transient.
  B. Administering purified ADA enzyme intravenously provides only temporary relief; it doesn't address the underlying genetic defect.
  C. Ex vivo gene therapy using autologous hematopoietic stem cells is the most promising.  Hematopoietic stem cells (HSCs) are self-renewing and give rise to all blood cells, including lymphocytes crucial for immunity.  Correcting the ADA gene in these cells ensures long-term correction as the corrected cells continuously divide and differentiate.
  D. Bone marrow transplant from an HLA-matched sibling is a potential cure, but it's not a gene therapy approach. It involves replacing the entire hematopoietic system, carrying a risk of graft-versus-host disease and requiring a suitable donor.
 3. Identify the best long-term solution.
  Result: Ex vivo gene therapy using autologous hematopoietic stem cells (option C) offers the most likely long-term solution.
  Verification: This approach directly addresses the genetic defect in a population of cells capable of self-renewal and differentiation into all blood cell lineages, ensuring sustained ADA production and immune function.
 ## OPTION ANALYSIS
A :x: In vivo gene therapy is less efficient and may not provide long-term correction.  Transduction efficiency in the bone marrow can be variable.
B :x: Enzyme replacement therapy is not a gene therapy approach and is only a temporary solution. The patient needs a permanent correction of the ADA gene.
C ✓: Ex vivo gene therapy using autologous HSCs offers the best chance for long-term correction because HSCs self-renew and differentiate into all blood cell types, ensuring continuous production of ADA.
D :x: Bone marrow transplant is a viable treatment, but it is not a gene therapy and relies on donor availability and HLA matching. It also carries risks of rejection and graft-versus-host disease.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing in vivo and ex vivo gene therapy: Understanding the difference in target cell modification and delivery is crucial.
  2.Overlooking the importance of self-renewal capacity of target cells: Only cells with high self-renewal potential can ensure long-term correction.
 **Quick Tips**:
  1.Remember that HSCs are the key to long-term correction in blood-related diseases.
  2.Ex vivo gene therapy offers better control and higher efficiency than in vivo gene therapy.

D VINOD · Answer

In vivo gene therapy using a retroviral vector directly injected into the bone marrow.

D VINOD · Answer

Administering purified ADA enzyme intravenously.

D VINOD · Answer

The correct Option is "Ex vivo gene therapy using autologous hematopoietic stem cells."

D VINOD · Answer

Bone marrow transplant from an HLA-matched sibling.

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