Quick recap of ERVs for new readers of ERV (or long-time readers who have forgotten!)–
ERVs are retroviruses that accidentally infected an egg/sperm cell, and became a permanent part of that egg/sperms DNA. That egg/sperm then went on to successfully generate a viable embryo, and because that retrovirus was part of the egg/sperms DNA, it also becomes a permanent part of the organisms DNA.
Though this is a very very rare, totally accidental event, on an evolutionary time-scale, random events have happened quite a few times, to the point where a large chunk of your, *your* DNA, is unquestionably retrovirus.
But retroviruses are A Bad Thing. They make us sick. Duh. So why arent we all sick now?
Well your genome has evolved ways of keeping these retroviral elements quiet– they are *there*, but they arent making babby viruses. The ERVs eventually accumulate lots of deletions and mutations, so they couldnt even potentially maybe generate a virus… but some of the younger ERVs still have the ability to make retroviral proteins, if not entire virus, if the cells tricks to keep the viruses quiet arent working properly.
Because ERVs are normally quiet, it seems looking for ERV proteins might be a useful marker for disease– cells arent working right because of cancer or some disease state, cells are not controlling ERV expression anymore, presence of ERV proteins indicate a disease state.
HERV-K elements are the youngest ERVs in your genome. If you poke cells in just the right way, you can get particle formation from totally normal, healthy human cells (but theyre noninfectious… probably). But a normal healthy human usually has fewer than 100 copies of HERV-K RNA/ml of blood (junk RNA from leaky/accidental transcription).
Breast cancer patients can have up to 108 copies/ml.
HIV-1 patients have up to 1010 copies/ml. O.o
Thats not just junk RNA, either. This group looked for HERV-K proteins and actual viral particles, and found them in the HIV-1 positive patients. Furthermore, the active HERV-Ks they found in the breast cancer patients all kinda looked alike. Continual transcription–>translation from the same endogenous retroviral locus. Like a factory that only knows how to make one toy.
… The HERV-K sequences in the HIV-1 patients changed over time. They were not just being transcribed–>translated… they were actively reverse transcribing and replicating… mutating and undergoing selection. That has never been described with a human ERV before O.o And it turns out that some of the activated HERV-Ks were human specific (ie not found in chimpanzees), which makes it look like these guys are still young and potentially active in humans!
And, this situation isnt as simple as ‘In breast cancer, THIS HERV-K is activated!’ or ‘In HIV-1 infection, THIS HERV-K is activated!’ They found 34 different activated HERV-Ks in their patients, six of which had never been described before. One, K111, was only found in the HIV-1+ patients, not the breast cancer patients.
But what does this all mean?
Well, for some kinds of breast cancer, this might mean we could figure out a diagnostic tool out of this. These scientists did *not* look for HERV-K expression in breast cancer tumors. They looked for HERV-K expression in blood. But, the question is, does the HERV expression only pop up after the cancer is already established and causing trouble (thus not a lot of help to us), or might they pop up way before things get really bad (thus giving us an extremely non-invasive diagnostic test?).
With HIV-1+ patients, this might mean we have a non-HIV target for our anti-HIV efforts. If these HERV-Ks are upregulated in infected cells (we dont know, it might be a global phenomena in response to an activated immune state, thus useless), we could direct our therapeutic vaccination efforts there. Target the old HERV that is not changing (… much…) instead of the rapidly evolving HIV-1.
Very very cool info in this paper. Maybe retroviruses that inserted into our genome, by accident, tens of thousands of years ago, can help us deal with modern diseases!
… Or they might be an artifact of the disease. Too little too late to be of any use to us. LOL!
We wont know until we look!!