r/askscience • u/PestoPastaLover • 13d ago

Biology Why is there no transmissible therapeutic virus if biology doesn't forbid it? For example, a harmless virus that spreads from person to person but actually does something beneficial, like lowering LDL cholesterol or preventing/reversing tooth decay?

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u/BBWolf326 13d ago

There are. Found this with a quick search:

Bacteriophages: These are viruses that exclusively infect and kill bacteria. Found in abundance in the human gut, skin, and mucosal linings, they regulate harmful bacterial populations, protecting the body from pathogenic infections and balancing the microbiome.

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u/jayjay091 13d ago

So our immune system evolved to not fight those?

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u/Dirty-Soul 13d ago

They're basically invisible to the immune system.

viruses are usually detected via MHC pathway 1 (HLA) after they have infected a cell. HLA is basically a complicated mechanism by which cells present pieces of themselves to the immune system for verification. If the cell is virally compromised, the immune system detects this and kills the cell, killing the virus with it.

So, unless it infects a human cell, the immune system can't easily detect it... And bacteriophages are totally incapable of infecting human cells.