#gene therapy

ZOOLOGY

Which disease was the first to be treated using gene therapy?

Adenosine deaminase (ADA) deficiency was the first disease to be treated using gene therapy. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.

Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Zoology section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Zoology portion (Latest NCERT Textbooks for Academic Session 2026-27 - Rationalized Edition for Class XI and XII), Topic: Structural organization, ph

View Details

Gene Therapy

One limitation of in vivo gene therapy is:

Direct in vivo administration viral vectors faces major limitation reduced control which cells internalize vector genome achieve therapeutic expression compared ex vivo selection. Systemic IV infusion distributes AAV particles according cardiac output vascular permeability liver sinusoidal fenestrations 100 nm capturing ~90 percent dose via heparan sulfate proteoglycan uptake hepatocytes Kupffer macrophages while target skeletal myofibers CNS neurons behind blood-brain barrier differentiated airway epithelia receive subtherapeutic copy numbers below threshold efficacy. No selection feasible af

Ref: Molecular Therapy In Vivo Targeting Limitations 2021; FDA Guidance In Vivo Gene Therapy Low Control Challenges; Lodish Gene Delivery Biodistribution Barriers Chap 9.

View Details

Gene Therapy

Target cells in cardiovascular gene therapy include:

Endothelial cell central therapeutic target cardiovascular gene therapy because monolayer regulates vascular homeostasis via eNOS converting L-arginine to nitric oxide stimulating soluble guanylate cyclase raising cGMP relaxing smooth muscle, prostacyclin via COX2 inhibiting platelet aggregation, barrier integrity VE-cadherin junctions, leukocyte adhesion E-selectin VCAM1. Dysfunction oxidative stress uncoupling eNOS drives atherosclerosis hypertension ischemia. Ischemic peripheral artery disease refractory angina benefit proangiogenic factors VEGF-A165, FGF4, HGF, HIF1-alpha delivered AAV1 or

Ref: Circ Res Cardiovascular Gene Therapy Endothelial Targets 2022; NHLBI Vascular Gene Therapy Overview; Lodish Vascular Biology Endothelial Function Chap 22.

View Details

Gene Therapy

Cancer gene therapy often uses strategy of:

Cancer gene therapy predominantly adopts tumoricidal strategy rather than restoration tumor suppressor because cancer genome carries multiple gain-of-function oncogenes KRAS MYC aneuploidy heterogeneity complicating simple addition. Methods eliminate malignant clone through introduction genes triggering death or immune recruitment. Oncolytic adenoviruses engineered deletion E1B 55 kDa protein normally inactivating p53 replicate selectively p53-deficient cancers lysing cells via viral burst releasing PAMPs tumor antigens danger signals ATP calreticulin HMGB1 driving immunogenic cell death. Suic

Ref: Nature Reviews Cancer Gene Therapy Oncolytic Mechanisms 2021; NCI Cancer Gene Therapy Targeted Killing; Molecular Therapy Oncolytic Viruses 2021.

View Details

Gene Therapy

Hemophilia gene therapy targets deficiency of:

Hemophilia A 1 in 5000 males and B 1 in 30000 males result null mutations coagulation cofactors FVIII 280 kDa glycoprotein encoded F8 Xq28 domains A1 A2 B A3 C1 C2 and FIX vitamin K dependent serine protease encoded F9 Xq27 gamma carboxyglutamic acid residues binding calcium phospholipid. Both assemble intrinsic tenase complex FVIIIa cofactor enhancing FIXa protease activity 200000-fold toward FX activation on phosphatidylserine-rich platelet surface accelerating thrombin burst fibrin clot formation. Deficiency prolongs aPTT causing hemarthrosis, muscle hematoma. Replacement requires frequent

Ref: NEJM Hemophilia Gene Therapy Nathwani 2022; FDA Hemgenix Roctavian Approvals; Alberts Cell Biology Coagulation Cascade Chap 20.

View Details

Gene Therapy

Which disease was among the first targets of gene therapy?

Adenosine deaminase deficiency autosomal recessive SCID became earliest successful gene therapy target due biological features favoring correction. Enzyme chromosome 20q13.12 deaminates adenosine to inosine and deoxyadenosine to deoxyinosine, deficiency leads accumulation deoxyadenosine converted deoxycytidine kinase to dATP elevated dATP allosterically inhibits ribonucleotide reductase essential dNTP synthesis DNA replication lymphocyte clonal expansion triggers apoptosis intrinsic pathway resulting absent T B NK cells. Lymphoid lineage provides selective advantage because corrected cells det

Ref: Lancet ADA First Gene Therapy NEJM 1990; NCBI SCID Gene Therapy History; NCERT Biotechnology Applications ADA Chapter 12.

View Details

Gene Therapy

CRISPR, ZFN and TALEN are used in gene therapy for:

CRISPR-Cas9, ZFN, TALEN constitute programmable site-specific endonucleases enabling precise genome manipulation. CRISPR uses single-guide RNA 20 nt spacer complementary to genomic target adjacent NGG PAM recognized Streptococcus pyogenes Cas9 possessing HNH domain cleaving complementary strand RuvC noncomplementary generating blunt double-strand break 3 bp upstream PAM. Zinc-finger arrays modules each recognizing 3 bp triplets linked FokI nuclease dimerize cutting within spacer, while TALEN repeats repeat-variable di-residues HD recognizing cytosine NI adenine NG thymine NN guanine provide si

Ref: NIH Genome Editing CRISPR ZFN TALEN Overview; Nature Biotech Comparison 2020; NCBI Gene Editing Therapy https://www.ncbi.nlm.nih.gov/books/NBK542207/.

View Details

Gene Therapy

Targeted killing of cells in gene therapy often uses:

Targeted killing arms tumor cells with enzymes converting systemically administered non-toxic prodrugs into potent cytotoxins achieving spatial specificity. Classic systems include HSV thymidine kinase type 1 phosphorylating ganciclovir 1000-fold higher affinity than mammalian kinase, E. coli cytosine deaminase codA converting 5-fluorocytosine to 5-fluorouracil inhibiting thymidylate synthase, bacterial nitroreductase NfsB reducing CB1954 to bifunctional alkylating crosslinking DNA. Expression restricted malignant cells using tumor-specific promoters survivin active G2/M, hTERT active 85 perce

Ref: PMC Suicide Gene Therapy HSV-TK Review; Nature Cancer Suicide Systems Overview; Lodish Molecular Biology Prodrug Activation Chap 23.

View Details

Gene Therapy

Gene augmentation therapy (GAT) is used to:

Gene augmentation alias addition therapy provides supplemental functional copy gene compensating recessive loss-of-function mutation where endogenous loci produce truncated or misfolded protein rapidly degraded proteasome or nonsense-mediated decay. Delivered cDNA lacks introns and native regulatory elements codon-optimized enhancing translation and CpG depleted reducing TLR9 activation expressed under heterologous constitutive promoter chicken beta-actin with CMV enhancer or tissue-specific transthyretin promoter driving strong transcription independent defective locus that remains present bu

Ref: NIH Gene Augmentation Therapy Strategy; Watson Molecular Biology Gene Augmentation Chap 15; NCBI Bookshelf Gene Addition https://www.ncbi.nlm.nih.gov/books/NBK21981/.

View Details

Gene Therapy

Which method directly delivers naked DNA into cells?

Electroporation applies brief high-intensity electric fields to transiently permeabilize lipid bilayer enabling direct cytosolic entry naked nucleic acids without chemical carriers. Square-wave pulses 100-1500 V/cm for microseconds to tens milliseconds generate transmembrane potential exceeding dielectric strength 0.2-1 V causing rearrangement lipids forming aqueous pores water intrusion between headgroups. Polyanionic DNA driven electrophoretically toward anode migrates through pores reaching cytoplasm within milliseconds before rapid resealing seconds mediated lateral diffusion and calcium-d

Ref: FDA Guidance Electroporation Devices 2021; Molecular Therapy Methods Electroporation Protocol; NCERT Biotechnology Ch 11 Electroporation Principles.

View Details

Gene Therapy

Non-viral vectors include:

Non-viral delivery uses chemically defined materials condensing nucleic acids avoiding viral capsid immunity and packaging limits. Cationic liposomes DOTAP, DOTMA, helper DOPE facilitating hexagonal phase transition, and cholesterol stabilizing bilayer electrostatically interact with negatively charged phosphate backbone plasmid DNA or mRNA condensing into lipoplexes 100-300 nm diameter positive zeta potential promoting binding anionic proteoglycans initiating endocytosis via clathrin and caveolae. Modern LNPs employ ionizable lipids DLin-MC3-DMA neutral at physiological pH 7.4 minimizing toxi

Ref: Lodish Molecular Cell Biology Non-viral Vectors Chap 9; NIH Non-viral Gene Delivery Liposomes Review; Alberts Membrane Fusion Liposome Mechanism.

View Details

Gene Therapy

Which viral vector shows very low immune response?

Recombinant AAV produced by triple transfection HEK293 cells with plasmids encoding rep/cap removed from vector, adenoviral helper functions E2A E4 VA RNA, and vector genome flanked by ITRs yields particles depleted viral coding sequences that normally generate PAMPs triggering innate and adaptive immunity. Capsid proteins VP1 VP2 VP3 ratio 1:1:10 from serotypes AAV2 AAV5 AAV9 exhibit low TLR2 mediated NF-kB activation and minimal TLR9 stimulation due to CpG depletion via codon optimization resulting reduced type I interferons, TNF-alpha, IL-12. Consequently transduced hepatocytes, muscle fibe

Ref: PMC AAV Low Immunogenicity Review PMCID 10142300; UQ Biomedical Sciences Vector Immunogenicity Comparison; Nature Med AAV Clinical Safety.

View Details