L5. Gene therapy II - AI MCQs

Biochemistry and Biotechnology Fundamentals: Gene Therapy II

• This course covers gene therapy approaches for various genetic disorders.

Contents

• Gene therapy for monogenic diseases
• Gene therapy for cystic fibrosis
• Gene therapy for emphysema
• Gene therapy for sickle cell anemia
• Gene therapy for SCID

Learning Objectives

• Explain gene therapy approaches for cystic fibrosis
• Describe alpha-1 antitrypsin deficiency and its treatment
• Differentiate between different gene therapy approaches for treating sickle cell anemia
• Discuss the reasons and therapy for SCID

Gene Therapy: Overview of ex vivo Gene Therapy

• Cells are harvested from the patient
• A virus is altered so it cannot reproduce
• Altered cells are injected into the patient's body
• Cells become transgenic
• Altered cells produce the desired protein
• Altered virus is mixed with patient's cells
• A gene is inserted into the virus

Cystic Fibrosis (Monogenic Disease)

• Genetic CFTR mutation at birth
• CFTR mutant protein with abnormal ion transport
• Viscous mucus and inflammation
• Leads to infection, obstruction, inflammation and structural damage
• Resulting in pulmonary insufficiency, premature death, and decreased mucus viscosity.
• Treatments include rhDNase I for improved pulmonary function and reduced infections.

Cystic Fibrosis (Monogenic Disease): Mechanism

• Healthy cells have a functional CFTR protein for Cl− ion transport.
• In cystic fibrosis, CFTR protein is faulty, leading to thick mucus build-up.
• Mucus builds up in the lungs, pancreas, and other organs.

Gene Therapy for Cystic Fibrosis

• Correct version of the CFTR gene is placed in the patient's cells
• The presence of the correct CFTR gene allows cells to produce normal CFTR proteins.
• Gene therapy for cystic fibrosis can be achieved through:
  • Non-integrating gene therapy
  • Integrating gene therapy

Non-Integrating Gene Therapy for Cystic Fibrosis

• A piece of DNA with the correct CFTR gene is provided to the patient's cells
• The DNA remains separate from the patient's genome
• Cells can still use the new copy to make normal CFTR proteins.
• Advantage: doesn't disrupt the rest of the genome.
• Disadvantage: not permanent (repeated treatment may be needed).

Integrating Gene Therapy for Cystic Fibrosis

• A piece of DNA containing the correct CFTR gene is delivered to patient's cells
• The new gene becomes a permanent part of the patient's genome.
• Advantage: permanent.
• Disadvantage: the new gene could insert into a critical part of the genome.

Disadvantages of Using Adenovirus in CF Gene Therapy

• Lack of adenovirus receptor on alveolar sac cells leading to low transduction
• Immunogenicity (immune response)
• Non-integration: adenovirus genome stays as an episome and doesn't integrate into host genome.
• Not permanent

Emphysema

• Emphysema is a lung disease primarily caused by smoking, air pollution, chemical fumes, and exposure to irritants damaging the lungs and airways.
• Symptoms include shortness of breath, coughing, and fatigue.
• Alpha-1 antitrypsin deficiency (AATD) can also cause emphysema.

Alpha-1 Antitrypsin Deficiency

• Elastin is a stretchy protein crucial for lung function.
• Elastase, a protein that degrades elastin, needs control.
• Alpha-1-antitrypsin (AAT) inhibits elastase to prevent elastin breakdown.
• In AATD, low AAT levels lead to excessive elastase activity and lung damage, causing emphysema.

Gene Therapy for Alpha-1 Antitrypsin Deficiency

• A short coding sequence for AAT would correct the deficiency.
• Gene delivery could be targeting various tissues and cell types, without impacting lungs.
• The goal of gene therapy is to continuously express the gene to treat affected individuals

Sickle Cell Anemia (Monogenic Disease)

• In sickle cell anemia, the amino acid glutamic acid is replaced by valine in the beta-globin chain of hemoglobin
•  Sickle cells block blood flow, depriving organs of oxygen
• This can damage nerves and organs, including kidneys, liver, and spleen.
• Leads to symptoms like anemia, jaundice, pain crises, splenomegaly, and stroke.

Sickle Cell Anemia: Gene Therapy

• Several gene therapy approaches exist for sickle cell anemia.
• Using CRISPR, a gene is silenced to enable production of fetal hemoglobin, preventing sickling

Severe Combined Immunodeficiency (SCID)

• A rare genetic disorder where development of functional T cells and B cells is impaired.
• This is due to multiple genetic mutations, with two main types of lymphocytes being B and T cells
• This results in an almost absent immune system.
• Adenosine deaminase (ADA) deficiency is a common cause because the buildup of dATP inhibits ribonucleotide and DNA synthesis, thereby impacting T and B cells, which are vulnerable as they are rapidly dividing cells.
• Gene therapy approaches are available

ADA Converts Deoxyadenosine to a Non-Toxic Substance

• Normal function of ADA converts deoxyadenosine into deoxyinosine (not toxic)
• ADA deficiency leads to deoxyadenosine buildup that's harmful, damaging B and T cells

Gene Therapy for SCID: Ex Vivo Approach

• Hematopoietic stem cells (HSCs) are extracted.
• Modified HSCs are introduced and returned to the bloodstream
• Viral vectors like lentiviruses and retroviruses allow for long-term gene expression.

Cancer Gene Therapy: Immunotherapy

• Cancer cells are harvested and grown in vitro.
• Genes are added to make cancer cells more recognizable by the immune system.
• Altering the cells is followed by growing and killing the cells in vitro
• Cellular contents are used to create a vaccine

Cancer Gene Therapy: Oncolytic Agents

• Gene therapy uses viruses that are modified to target and destroy cancer cells.
• These modified viruses propagate themselves and/or express cytotoxic proteins, causing cancer cell death.

Cancer Gene Therapy: Gene Transfer

• The introduction of foreign genes into cancer cells or surrounding tissue.
• Genes can be suicide genes or antiangiogenesis genes.
• Adenovirus is commonly used as a gene transfer viral vector in clinical trials.

Ethical considerations in gene therapy

• Carcinogenesis, interference with natural selection, effect on offspring, access to therapy, use of gene therapy for enhancement, prenatal use, distinction between good and bad uses of technology, who decides on normal and disordered traits, high costs of gene therapy, and widespread use altering social acceptance of individuals.