This appears to be a consequence of a rudimentary immune system of the helper virus, termed MIMIVIRE (mimivirus virophage resistance element), akin to the CRISPR-Cas pathway.

Zamilon was discovered in 2013, in Acanthamoeba polyphaga amoebae co-infected with the giant virus Mont1, isolated from a Tunisian soil sample.

[2][6] A related strain, named Zamilon 2, was discovered by metagenomic analysis of a North American poplar wood chip bioreactor in 2015.

[3] Zamilon does not appear to inhibit the ability of its helper virus to replicate significantly, nor to lyse its host amoebae cells.

Although the helper virus formed a high proportion of abnormal virions in the presence of Zamilon, these were also observed at a comparable level in the virophage's absence.

[3] This is again unlike Sputnik, which reduces its helper virus's infectivity, inhibits its lysis of amoeba, and is associated with the generation of an increased proportion of abnormal Mimiviridae virions.