THURSDAY, July 26 (HealthDay News) -- Following bone marrow
transplants, two men infected with HIV no longer have any traces of the
AIDS-causing virus in their lymphocytes, researchers report.
Lymphocytes are a type of white blood cell and are a key part of the
immune system.
The U.S. researchers suspect that bone marrow transplantation along
with continuation of antiretroviral therapy resulted in the dramatic
effects evident eight months post-transplant. They are scheduled to
present these preliminary findings Thursday at the International AIDS
Conference in Washington, D.C.
HIV patients on antiretroviral therapy often achieve "undetectable
viral loads," meaning there are no virus particles in their blood. But
they still have latent HIV in their lymphocytes, and if antiretroviral
therapy were discontinued, the latent HIV could reactivate.
But having no traces of HIV in these white blood cells is an indication
that this "reservoir" of latent HIV may have been eliminated, the
researchers believe.
At this point, they are far from saying these patients are cured. But
the findings are "exciting," said Dr. Savita Pahwa, director of the Center
for AIDS Research at the University of Miami Miller School of Medicine,
who was not involved with the study.
"Every hint you get that it's possible to wipe out the reservoir needs
to be investigated," she said.
"Eliminating the reservoir is the key to the cure," said Pahwa. She
also stressed that it would only be
possible to say these patients were
"functionally cured" if the virus did not rebound when the patients went
off antiretroviral therapy.
The two men whose cases are described in the paper underwent
chemotherapy for blood cancers before receiving stem cell transplants. One
had his transplant two years ago; the other, four years ago. Both also
developed graft-versus-host disease (when transplanted cells attack the
host cells) and continued with their antiretroviral medications throughout
and after the transplant procedures.
Any of these factors could theoretically explain their HIV-free status,
but the bone marrow transplantation combined with antiretroviral therapy
seems the most likely explanation, said the study authors.
"We believe the transplanted cells killed off and replaced all of the
patients' own lymphocytes, including the infected cells, and the donor
cells were protected from becoming infected themselves by the
antiretroviral therapy they were taking throughout the transplant period,"
said study senior author Dr. Daniel Kuritzkes, chief of infectious
diseases at Brigham and Women's Hospital and professor of medicine at
Harvard Medical School in Boston.
Graft-versus-host disease also probably played a role, he said. "The
replacement of host cells by donor cells is itself a form of
graft-versus-host reaction," Kuritzkes explained.
But the only way to verify that the transplant plus antiretroviral
therapy can eradicate HIV is to take the patients off their medication
regimens.
That would be the "next logical step," said Kuritzkes, adding that this
would require patient consent and adherence to ethics protocols.
But even if the transplant procedure were found to eliminate the
reservoir of latent HIV cells, bone marrow transplantation is a very risky
procedure. Kuritzkes said he does not "foresee bone marrow transplantation
being performed on otherwise healthy HIV-infected patients who are doing
well on [antiretroviral therapy]."
Kuritzkes and his colleagues are continuing to enroll and follow
HIV-positive patients who have
undergone bone marrow transplants as part
of a larger study.
This preliminary study contains echoes of the so-called "Berlin
Patient," who has no detectable HIV cells in his blood five years after a
stem cell transplant for leukemia.
Like the two men discussed in the current paper, the Berlin Patient --
Timothy Ray Brown of Seattle -- also had been diagnosed with HIV and also
underwent chemotherapy (for acute myeloid leukemia) and developed
graft-versus-host disease.
But, unlike the current patients, Brown received his stem cell
transplant from a donor who had a rare genetic mutation that increases
immunity against the most common form of HIV. He remained HIV-free after
discontinuing antiretroviral therapy.
The two men described here received donor cells, which were "fully
susceptible" to HIV, Kuritzkes said. This raises the possibility that a
cure may be possible even when the donor does not have this gene mutation,
he said.
Because this research has not been peer-reviewed and published in a
medical journal, the data and conclusions should be considered
preliminary.
