Mousepox, caused by orthopoxvirus ectromelia virus, closely related to #smallpox only infects mice. In mice it causes a mild illness. In 2001 Australian scientists were developing a contraceptive vaccine for mice. But it killed all the mice. (Thread) newscientist.com/article/dn311-…
The vaccine was to help control mouse breeding and reduce agricultural damage . They used ectromelia virus as a vector to carry mouse egg proteins so the mice would develop antibodies to their own eggs and thereby become infertile.
They inserted a gene for production of interleukin-4, a cytokine that stimulates the immune system, hoping this would accelerate the production of antibodies. When they vaccinated the mice with smallpox vaccine (which also protects against ectromelia virus),
they discovered the genetic changes they had engineered also made the mice resistant to smallpox vaccine. In effect, they had created a more deadly virus that was also vaccine-resistant.
The work sparked concern around the world, because it suggested that similar engineering of #smallpox could produce a more lethal version that current vaccines could not protect against. Natural smallpox has a 30 per cent fatality rate.
The mousepox experiment killed all the mice – what if a similarly engineered smallpox resulted in a fatality rate of 50 to 100 per cent? If current vaccines could not protect against such a virus, then a pandemic of engineered smallpox could be an extinction event.
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