Dr. Antoinette C. Van Der Kuyl:
Academic Medical Centre, University of Amsterdam, Medical Microbiology, Meibergdreef 15, Amsterdam, 1105 AZ, Netherlands
The novel human retrovirus XMRV (xenotropic murine leukemia virus-related virus) is arguably the most controversial virus of this moment.
In conclusion, the most likely mode of XMRV transmission
points to mouse-derived biological products, but it cannot
formally be excluded that the virus was once transferred from
feral mice to humans.
The latter scenario is less likely as it would imply that a very
rapid spread in the human population must have occurred to
explain its presence on two continents. In this scenario, the
extreme sequence similarity among XMRV genomes, both
between and within individuals, would argue that the virus
replicates at very low levels.
Among the biological products, vaccines that were produced in
mice or mouse cells are possible candidates that warrant
further inspection. If XMRV was introduced in the human
population through the use of biologicals, a background level
of the virus in the human population, possibly varying with
geography or age group, would be expected.
Such a low level presence would then also explain the
(absence of) detection of the virus in different studies, as
well as its controversial association with disease.
We hope that this hypothesis will spur further discussion and
help to resolve the many remaining XMRV questions.