Viral vectors are engineered viruses used to deliver genetic material into cells, usually for the purpose of gene therapy, vaccine development, or basic research. Viruses naturally have the ability to infect cells and introduce their genetic material into the host cell’s genome. Scientists exploit this ability by modifying viruses to carry therapeutic or desired genes instead of their original genetic material.
Some advantages of using viral vectors include their high efficiency of gene delivery, ability to infect a wide range of cell types (including non-dividing cells), and the possibility of long-term gene expression in host cells.
There are several types of viral vectors commonly used in research and therapy:
- Adenoviral vectors: Derived from adenoviruses, these vectors have a large carrying capacity for foreign genes and can infect both dividing and non-dividing cells. However, they typically elicit a strong immune response and do not integrate into the host genome, resulting in transient gene expression.
- Adeno-associated viral (AAV) vectors: AAV vectors are derived from small, non-pathogenic viruses and can infect both dividing and non-dividing cells. AAV vectors can provide long-term gene expression with minimal immune response, making them popular choices for gene therapy applications. However, their carrying capacity for foreign genes is relatively small.
- Lentiviral vectors: Derived from retroviruses like HIV, lentiviral vectors can stably integrate into the host genome, allowing for long-term gene expression. They can infect both dividing and non-dividing cells and have a moderate carrying capacity. Lentiviral vectors have been widely used in gene therapy and basic research, including the generation of induced pluripotent stem cells (iPSCs).
- Retroviral vectors: Similar to lentiviral vectors, retroviral vectors are derived from retroviruses and can stably integrate into the host genome. However, they can only infect dividing cells, limiting their use in some applications.
While viral vectors have shown promise in various applications, there are potential risks and challenges associated with their use. These include the possibility of an immune response against the vector or the therapeutic gene, the potential for insertional mutagenesis (unintended integration of the viral vector into the host genome, causing harmful mutations), and the limitations in the size of the genetic material that can be packaged into the vector.
To address these challenges, researchers are continually developing new viral vector systems and alternative gene delivery methods, such as non-viral vectors, to improve the safety and efficacy of gene therapy and other applications.