Viral vector

Viral vectors are modified viruses designed to deliver genetic material into cells. This process can be performed inside an organism or in cell culture. Viral vectors have widespread applications in basic research, agriculture, and medicine.

Viruses have evolved specialized molecular mechanisms to transport their genomes into infected hosts, a process termed transduction. This capability has been exploited for use as viral vectors, which may integrate their genetic cargo—the transgene—into the host genome, although non-integrative vectors are also commonly used. In addition to agriculture and laboratory research, viral vectors are widely applied in gene therapy: as of 2022, all approved gene therapies were viral vector-based. Further, compared to traditional vaccines, the intracellular antigen expression enabled by viral vector vaccines offers more robust immune activation.

Many types of viruses have been developed into viral vector platforms, ranging from retroviruses to cytomegaloviruses. Different viral vector classes vary widely in strengths and limitations, suiting some to specific applications. For instance, relatively non-immunogenic and integrative vectors like lentiviral vectors are commonly employed for gene therapy. Chimeric viral vectors—such as hybrid vectors with qualities of both bacteriophages and eukaryotic viruses—have also been developed.

Viral vectors were first created in 1972 by Paul Berg. Further development was temporarily halted by a recombinant DNA research moratorium following the Asilomar Conference and stringent National Institutes of Health regulations. Once lifted, the 1980s saw both the first recombinant viral vector gene therapy and the first viral vector vaccine. Although the 1990s saw significant advances in viral vectors, clinical trials had a number of setbacks, culminating in Jesse Gelsinger's death. However, in the 21st century, viral vectors experienced a resurgence and have been globally approved for the treatment of various diseases. They have been administered to billions of patients, notably during the COVID-19 pandemic.