Frequently asked questions (FAQ)
What is an oncolytic virus?
An oncolytic virus is a recombinant virus that has been genetically modified in a laboratory to specifically replicate in tumor cells. At the end of the replication cycle, the oncolytic virus kills the tumor cell to release new virions (virus particles).
What is cancer immunotherapy and what is immunostimulatory gene therapy? What’s the difference?
Immunotherapy is a broad group of therapeutics that treat or prevent a disease by stimulating an immune response. One of the applications of immunotherapy is for treating cancer and this is referred to as cancer immunotherapy.
Immunostimulatory gene therapy is a type of cancer immunotherapy that uses a genetically modified (i.e., recombinant) vector containing immune-activating genes (transgenes) to stimulate an immune response. There are several types of vectors that can be used in immunostimulatory gene therapy including virus vectors and plasmid DNA vectors.
What is recombinant adenovirus?
LOAd therapy uses a genetically modified (i.e., recombinant) virus vector derived from a common cold virus called adenovirus. This type of viral vector is commonly used in gene therapy. This recombinant adenoviral vector has been attenuated (i.e., weakened) compared to native adenovirus, and it has also been modified so that it specifically replicates only in tumor cells.
Why does oncolytic virus only kill tumor cells?
In cells, retinoblastoma (Rb) is one of the key proteins regulating cell growth. Cancer cells typically have an abnormal Rb pathway and the LOAd virus has been genetically modified to take advantage of this. Thus, LOAd virus only replicates in cells with an abnormally functioning Rb pathway, which typically occurs in tumor cells.
Does LOAd virus only infect tumor cells?
No, LOAd virus is also able to infect normal cells surrounding the tumor cells. All infected cells will express the LOAd immunostimulatory genes (transgenes). This means that the immunostimulatory genes from the LOAd virus will be expressed as immune-activating proteins on the surface of infected cells where they can stimulate immune responses. Thus, LOAd virus works both by stimulating immune responses in the tumor area as well as by directly killing tumor cells.