Editing Viral Vector Engineering (section)

== 3. Lentiviral Vectors: Stable Integration ==

Lentiviruses (part of the retrovirus family) carry their genetic payload as RNA. 
* '''Mechanism:''' Once inside the host cell, the vector uses reverse transcriptase to convert its RNA payload into DNA. Crucially, it then uses an enzyme called integrase to permanently splice this new DNA into the host cell's genome.
* '''Application:''' Because the insertion is permanent, the therapeutic gene is copied every time the host cell divides. This makes lentiviral vectors ideal for ''ex vivo'' gene therapies targeting rapidly dividing cells, such as hematopoietic stem cells in the bone marrow or engineering CAR-T cells for cancer immunotherapy. 
* '''Drawback:''' The primary risk is insertional mutagenesis—if the vector accidentally integrates its DNA in the middle of a critical host gene (like a tumor suppressor), it can cause cancer.