I hesitate to write about this, as Im sure its going to be taken and amplified by Teh Crazy… but I suppose I better just get a head start…
Researchers took a dozen cat/dog vaccines from manufacturers in Japan and Britain, and looked for a specific cat endogenous retrovirus, RD-114. Why this cat ERV? Cause the viruses in these vaccines are passaged in cat cell lines to attenuate them. Cat cell lines that contain and can produce ERV RD-114. Whats RD-114? Welp, um, its distinct-from-but-related-to feline leukemia virus.
Well, no. MLV and FeLV are equally genetically distant from RED-114, that is, theyre all gammaretroviruses, and clearly genetically related, but they are not ‘the same virus’ any more than MLV and PERVs are ‘the same virus’.
And these are cat/dog vaccines that use cat cell-lines for production. While this is important information for maintaining the heath of our dogs/large cats in zoos/etc (its shouldnt have an effect on domestic cats, as they all already have this ERV), this has a minimal impact on humans. I am unaware of any human vaccines that use cat cell-lines.
However, this could have an impact on live attenuated vaccines passaged in mouse cell-lines:
…the current methods used for screening human vaccines for retroviral contaminants include extremely sensitive PCR-based RT assays (not required for veterinary vaccines) that are much more sensitive than conventional RT assays. Thus, contamination of human vaccines with XMRV, would not pass undetected with the currently available technology although this may not be necessarily true for vaccines produced in previous decades.
And, as we will see, their ‘finding an infectious ERV in pet vaccines’ isnt as AAAAAAAHHHHHHHSCARY as Im sure some will make it sound:
So, in Japan, they tested 15 samples of 11 vaccines from 7 manufactures. Of the 15 samples, 6 had some kind of reverse transcriptase activity. Those 6 were also PCR positive when they looked for RD-114 envelope sequence (because its an endogenous retrovirus, they all have the same envelope sequence).
Of those 6, 4 were in vaccines for dogs.
A different lab in Britain tested 6 vaccines via RT activity and Western Blots. Two had RD-114.
Now, these authors note that 1) not every batch of the same vaccine from the same company had RD-114 and 2) they had to passage these viruses a long time to see increases in RT activity. In other words, not every vaccine from the same company is contaminated, and the ones that are contaminated have very, very, very little virus in them.
The risks posed by a low level exposure to RD-114 for pets are likely extremely small.
…the large scale exposure to RD-114, particularly of the dog population, may have effects that are impossible to predict even if successful RD-114 transmission was an extremely rare event. Millions of puppies are vaccinated annually worldwide and they may be more susceptible to RD-114 infection than cats as the dog genome does not harbor RD-114. Also wild cats do not harbor RD-114 and they are regularly vaccinated in zoos with the same vaccines used for pets.
… Finally, although the risks posed by RD-114 are seemingly small, it would be appropriate to produce live attenuated vaccines in cells that do not express this endogenous retrovirus. To this end, cells of dog origin may be better suited to produce pet vaccines than cat cell lines, although not all cat cell lines express RD-114 (2, 10).
I love Arnie more than life itself, and Im still getting him vaccinated. However I will be happy if they start using a different cell line for producing dog vaccines.
Finally, again what they reasonably say about XMRV and humans:
A recently identified novel human retrovirus (xenotropic murine leukemia virus- related retrovirus, XMRV) has been found in some forms of prostate cancers and chronic fatigue syndrome in man (13, 20, 22) although causal association has not been proven yet. XMRV is almost undistinguishable from an ERV present in mice and it will be important to investigate how this virus passed into the human population, regardless of its pathogenic potential. Interestingly, the current methods used for screening human vaccines for retroviral contaminants include extremely sensitive PCR-based RT assays (not required for veterinary vaccines) that are much more sensitive than conventional RT assays. Thus, contamination of human vaccines with XMRV, would not pass undetected with the currently available technology although this may not be necessarily true for vaccines produced in previous decades.
Vaccines today are safe from XMRV contamination, and previous decades vaccines I think are covered under my initial post.