Terms and definitions
You can click on any definition to return to the page where it was mentioned.
Adeno-associated virus (AAV) vector1,2: A non-replicating and non-pathogenic virus-based protein shell that is engineered as a vehicle to deliver a gene cassette to the nucleus.
Antibody: A protein that circulates in the blood and binds to a foreign substance. Antibodies are part of the humoral immune system.
Antigen: Any substance, such as bacteria or viruses, that causes the body’s immune system to produce antibodies against that substance.
Baculovirus: A type of virus that infects insects. It can be reprogrammed for use in manufacturing to help produce the large quantity of AAVs that are necessary for gene therapy.
CAG trinucleotide repeat (trinucleotide repeat expansion)3: A mutation that occurs when the three DNA base pairs, cytosine, adenine, and guanine (CAG), appear multiple times in a row. Excessive CAG repeats can lead to disease.
Capsid: The protein shell surrounding viral DNA that helps deliver the genetic material to specific cell types.
Cells: The building blocks for all living things. The trillions of cells in the body provide structure and function to all parts of the body. Cells contain DNA and are the smallest structural and functional unit of an organism.
Cellular immune response: Also known as cytotoxic T-cell response
Cellular tropism: The preferential ability of some viruses to infect a particular cell type. Variations in tropism may be due to properties, such as interaction with a specific receptor type on that cell.
Deoxyribonucleic acid (DNA): Genetic material found in the nucleus of cells that contains instructions to direct the cell’s activity. Your DNA contains a unique code that makes you, you.
Episome4: Circular DNA found in the nucleus that does not integrate into the chromosome and independently replicates.
Functional gene (transgene): The working gene/genetic material that has been inserted into the gene delivery vehicle (vector).
Gene5: A sequence of DNA bases (nucleotides) that provides the cell with instructions to make proteins, which carry out specific functions in the body.
Gene cassette6: The genetic material the gene therapy vector delivers to the target cells. It typically contains the functional gene and other regulatory elements to help direct expression.
Gene knockdown: Also known as gene silencing
Humoral immune response: Refers to antibody production by specialized immune cells (B cells) in response to a foreign substance (eg, viruses and bacteria).
Inherit: To receive genetic material from parents.
Messenger RNA (mRNA): Carries the instructions for making a protein.
MicroRNA (miRNA)7: Binds to mRNA to block mRNA from making protein.
Mutation: A change in the composition of a gene and/or its protein product that alters the protein function.
Neutralizing antibodies (NAbs)8: Types of antibodies that bind and interfere with the function of the antigen.
Nucleus: The core of the cell, which contains DNA.
Phenotype: A person’s observable physical traits, such as eye color and height.
Protein Shell: Also known as capsid, capsid shell, virus shell, vector shell or gene delivery vehicle shell
Ribonucleic acid (RNA)9: Genetic material present in all living cells that plays a major role in protein synthesis. Multiple types of RNA contribute to protein synthesis.
Serotypes: Different subtypes of AAV are called serotypes. The different serotypes have distinct protein shells that influence delivery of the functional gene, activation of the human immune system, and their ability to enter different types of cells (tropism).
Target cell: The location to which the functional gene is intended to be delivered, or targeted, towards, through vector tropism and tissue-specific promoters.
Tissue-specific promoter: Short sequences of DNA that instruct the cell when and how often to read the gene that follows, and are only active in certain cell types.
Transcription: The process of turning DNA into mRNA.
Transduction10: The process of introducing genetic material into another cell by an infectious agent, eg, a virus.
Wild-type11: The most frequently occurring form, appearance, or strain existing in nature.
X-linked disease: X-linked diseases are caused by mutations in genes on the X chromosome. Men only have one X chromosome, so only one defective copy of the gene is sufficient to cause disease. Women who have one normal copy of the gene and one mutant copy are known as carriers and may experience a range of symptoms or none at all.24
X-linked recessive pattern: In X-linked recessive inheritance, women are carriers when a mutation occurs on only one of two copies of the gene. Because men have only one X chromosome, sons who inherit a mutant copy will have symptoms of the disease. Hemophilia is considered to be a male-specific disease, except in rare cases when a woman inherits two mutant copies. However, female carriers can have symptoms, such as easy bruising, heavy menstrual bleeding, and excessive bleeding during childbirth.28