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 curre
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