Gene editing is the technique using which scientists can change the DNA sequence of organisms. DNA is a biological molecule that stores and carries hereditary information from one generation to another. Several methods of gene editing are constantly being developed one of which is the CRISPR-Cas9 technique. It is a cheaper, faster, and effective method of gene editing.
Clustered regularly interspaced short palindromic repeats and CRISPR-associated protein 9 (CRISPR-Cas9) techniques use the bacterial naturally occurring genome editing system. This system helps bacteria evade viral pathogens. This gene-editing tool has revolutionized the field of bioengineering and has the potential to achieve medical breakthroughs in cases once not thought possible.
Jennifer Doudna and Emmanuelle Charpentier in 2012 published their finding that CRISPR-Cas9 could be programmed with RNA to edit genomic DNA sequence and received the Nobel prize for the discovery.
Potential CRISPR Applications
- Treating diseases: As CRISPR- Cas9 technique can modify DNA sequences, it has been proposed as a treatment of multiple human genetic diseases. Early researches in an animal model have shown it to be able to potentially treat genetic diseases such as Down syndrome, beta-thalassemia, sickle cell disease, hemophilia, cystic fibrosis, Huntington’s disease, Duchenne muscular dystrophy, and hosts of genetic heart disorders. It has the potential of modifying genes in cancer cells which can lead to cancer remission.
- Treatment of viral infection: Studies conducted in animal and in vitro models have shown CRISPR technology to be effective in reducing and eliminating persistent viral infection raising hope for the treatment of chronic viral illnesses like HIV infection in humans. Researches have shown it to be effective in limiting the multiplication of the Human Herpesvirus
- In antibacterial therapy: CRISPR technology might be used to develop selective antimicrobials to destroy drug-resistant pathogenic bacteria. Bacteria’s genetic system can be effectively used in preventing the acquisition of genomic elements that confer its resistance from antibacterial therapy. Also, it could help in targeting specific virulence factors of the organism.
- Organ transplantation can be made easy by creating blood vessels lacking proteins that cause graft rejection
- Creating genetic drives: This is another exciting possibility of CRISPR technology. By creating genetic drives the chances of favorable characters/traits from parents to offspring are increased which eventually spreads through an entire population over time. This could help eradicate invasive species and attain immunity from diseases. In adding to adding new sequences it can remove undesired sequences thus getting rid of unfavorable characters.
- In addition to its medical uses, this technology can be used in food processing and agriculture as well. It can help improve food shelf life, increase safety, and potentially increase plant yield and quality.
CRISPR Drawbacks and Limitations
- It is not 100% effective, the efficacy of gene editing is shown to be somewhere around 50-80%
- Off Target effect: Here the DNA sequence is cut from a site other than the intended site which can result in unwanted mutation and pose safety risks
- As the changes made to germ cells and the growing embryo can be inherited by future generations as well, there are multiple ethical and safety considerations associated with it. As a result of which it is illegal in most countries.
Recent Advances in CRISPR TechnologyCRISPR technology has the potential to revolutionize the field of medicine and treatment. Different clinical trials are being carried out to know more about the CRISPR technique and its safety and efficacy in treating various conditions.
- In the treatment of multiple solid tumors: the CRISPR technique is being studied for its efficacy and safety in the treatment of multiple solid tumors expressing mesothelin protein on their surface. The study is aimed at checking the anti-tumor effect of the technique in treating such tumors.
- Treatment of metastatic gastrointestinal cancer: A clinical trial is being carried out to check the efficacy of Tumor-Infiltrating Lymphocytes (TIL) in the treatment of gastrointestinal cancer. The downregulation of CISH (Cytokine-induced SH2 protein) has been shown to increase the effectiveness of TIL in the treatment of various cancers. This study applies the CRISPR technique to inhibit this protein thus potentiating the action of TIL in cancer regression.
- Herpetic keratitis: The safety, efficacy, and tolerability of BD111 (CRISPR/Cas9 mRNA Instantaneous Gene Editing Therapy) is being studied in a clinical trial for the treatment of herpetic viral keratitis refractive to other medications. It is being developed as a single dose therapy to be administered via corneal injection.
- Non-Hodgkin lymphoma: Treatment of a refractory case of Non-Hodgkin lymphoma using CRISPR-Edited Therapy (CB-010) is being studied for its safety and efficacy following treatment with cyclophosphamide and Fludarabine. ( Drugs used in the treatment of lymphoma)
- Hematological malignancy in AIDS: A clinical trial aimed at improving the condition of AIDS patients with hematological malignancy is underway with the help of a CRISPR modified CD34+ hematological stem cell transplant. This study aims at assessing its safety and efficacy.CD34+ cells are taken from healthy donors.
- Thalassemia: A study to assess the safety and efficacy of autologous CRISPR-Cas9 Modified CD34+ Human Hematopoietic Stem and Progenitor Cells in the treatment of patients with beta-thalassemia requiring blood transfusion is also being carried out.
- Severe sickle cell disease: The safety and efficacy of autologous CRISPR-Cas9 Modified CD34+ Human Hematopoietic Stem and Progenitor Cells is also being studied for its treatment in severe sickle cell disease.
- Multiple myeloma: A clinical trial studying the effectiveness of CRISPR edited therapy in treatment in cases of treatment-resistant and relapse cases of Multiple myeloma is underway.
- Renal cell carcinoma: A clinical study of CRISPR-based technology is also being assessed for its efficacy and safety in treating refractory cases of RCC.
- Rapid identification of TB: CRISPR based test is being evaluated for its efficacy in rapid diagnosis of TB in pulmonary TB suspects who are undergoing sputum analysis or other traditional methods of detection. The correctness of results of the gene-editing method will be compared with conventional methods of TB diagnosis including clinical diagnosis, conventional culture methods, and Xpert MTB/RIF assay.
Jeffrey R. Stricha, Daniel S. Chertow et al. CRISPR-Cas Biology and Its Application to Infectious Diseases.J Clin Microbiol. 2019 Apr; 57(4): e01307-18.( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6440769/)