Viruses, apocalyse or antidote?

4 May 2018

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Viruses are portrayed in mainstream media as these nasty little germs that can have apocalyptic scale devastation on the human population. From movies such as I am Legend and Planet of the Apes to video games like Resident Evil and The last of us, viruses (fictional or not) are always given a terrible reputation, which is sadly just not true. Yes, there are some viruses that are a major cause for concern are indeed life-threatening, Ebola and HIV are prime examples. This is, however, only one side of the story. Many viruses are being investigated for their use as treatments to diseases such as cancer and other genetic illnesses.

The truth behind science fiction

If you have seen, I am Legend this is a great place to start. Spoiler alert! The movie is quite old so I don’t feel bad about discussing the plot. The movie begins with the idea that a new virus has been developed as a cure for cancer. This virus then goes on to wipe out the human race. Worse still, it can mutate some of the humans it has infected. This is a great plot twist for a movie but the reality is far less ominous. I am legend is an example of how most great stories start with some truth. The movie mentions the virus that causes the apocalypse is a genetically re-engineered measles virus. As scary as this may sound, the measles vaccine virus is currently being investigated for its use as a cancer therapy. In fact, the first virus to gain FDA approval (in 2015) for the treatment of a particular skin cancer known as melanoma was a genetically engineered herpes virus. Its brand name is Imlygic. Before you baton down the hatches and prepare survival kits there are a few important facts you need to know about how this virus works and how it has been engineered. Herpes simplex virus type 1 is the germs responsible for cold sores while type 2 causes genital warts. So you may be wondering, who on earth thought of giving a patient cold sores to cure their cancer, how does that work?

Engineering viruses can be a good thing

Robert Coffin is the answer, he invented the engineered herpes virus that is now approved for treatment. Perhaps the most important thing you need to understand about the virus is, yes it is genetically engineered but that isn’t necessarily a bad thing. The virus has been engineered to be safer than its original cold sore spreading predecessor. This is done by making the virus obvious to the immune system and stopping it from reproducing in healthy cells. Viral genes that cause harm to its host cells are removed. Genes that help the virus hide from the immune system or genes that promote cell division to ensure viral replication are good examples. The removal of these genes ensures the virus can only infect and kill cancer cells. Cancer cells are susceptible to infection because they can divide rapidly and they are able to evade the immune system. This makes cancer cells the ideal place for the virus to grow. Scientists didn’t stop there, by deleting certain genes from the virus there is now space to replace them with an alternate gene. Scientists have inserted a human gene called granulocyte-macrophage colony-stimulating factor or GM-CSF for short. This gene stimulates the immune system and spurs it to take action against the virus as well as the cancer cells. The immune cells are then responsible in large part for killing the cancer cells.

Apocalypse now?

As for the idea of an apocalyptic virus, where does that leave us? This seems a little far-fetched when you consider that the engineered viruses are designed to specifically infect cancer cells and alert the immune system to their presence. The viruses are cleared by the immune system and destroy cancer cells along the way. So despite what Hollywood would have you believe viruses can be the good guys many of them are engineered yes, but that is not as scary as it sounds.

Fun facts

Did you know that viruses that kill cancer cells are called Oncolytic viruses? Onco – relating to tumours (like oncology) and lytic meaning to burst the cell.

Did you know that using viruses to treat cancer is a really old idea? The first recorded cases of patients going into temporary remission after a viral infection were recorded in the 1800s.


References

  1. Aref, S., Bailey, K. & Fielding, A. Measles to the Rescue: A Review of Oncolytic Measles Virus. Viruses 8, 294, doi:10.3390/v8100294 (2016).
  2. FDA. IMLYGIC (talimogene laherparepvec), https://www.fda.gov/vaccines-blood-biologics/cellular-gene-therapy-products/imlygic-talimogene-laherparepvec (03/01/2018).
  3. WHO. Herpes simplex virus, https://www.who.int/en/news-room/fact-sheets/detail/herpes-simplex-virus (2017).
  4. Ledford, H. Cancer-fighting viruses win approval. Nature News 526, 622 (2015).
  5. Kaufman, H. L., Kohlhapp, F. J. & Zloza, A. Oncolytic viruses: a new class of immunotherapy drugs. Nature Reviews Drug Discovery 14, 642, doi:10.1038/nrd4663 https://www.nature.com/articles/nrd4663#supplementary-information (2015).
  6. NCI. Oncolytic Virus Therapy: Using Tumor-Targeting Viruses to Treat Cancer, https://www.cancer.gov/news-events/cancer-currents-blog/2018/oncolytic-viruses-to-treat-cancer (2018).