Protection from an unexpected source
Contrary to common belief, not all viruses are harmful to their hosts. Sometimes viruses can even protect their hosts from infection by other viruses. Scientists at the Max-Planck-Institute for Medical Research in Heidelberg and their collaborators have now demonstrated that this is the case for so-called endogenous virophages: small DNA viruses that are mostly found inserted into the genomes of single-cell eukaryotes.
https://www.gesundheitsindustrie-bw.de/en/article/press-release/protection-unexpected-source