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updated 7/26/2012 2:51:07 PM ET 2012-07-26T18:51:07

Two men unlucky enough to get both HIV and cancer have been seemingly cleared of the virus, raising hope that science may yet find a way to cure for the infection that causes AIDS, 30 years into the epidemic.

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The researchers are cautious in declaring the two men cured, but more than two years after receiving bone marrow transplants, HIV can't be detected anywhere in their bodies. These two new cases are reminiscent of the so-called "Berlin patient," the only person known to have been cured of infection from the human immunodeficiency virus.

These two cases, presented as a “late-breaker” finding on Thursday at the 19th annual International AIDS Conference in Washington, D.C., are among the reasons that scientists have been speaking so openly at the event about their hopes of finding a cure.

“Everyone knows about this ‘Berlin patient’. We wanted to see if a simpler treatment would do the same thing”, said Dr. Daniel Kuritzkes of Brigham and Women’s Hospital in Boston, who oversaw the study. The widely publicized patient, Timothy Brown, was treated for leukemia with a bone marrow transplant that happened to come from a donor with a genetic mutation that makes immune cells resist HIV infection. The transplant replaced his own infected cells with healthy, AIDS-resistant cells. He is HIV-free five years later.

AIDS patients are susceptible to cancers, but they usually stop taking HIV drugs before receiving cancer treatment. “That allows the virus to come back and it infects their donor cells,” Kuritzkes said.

About 34 million people are infected with HIV, the virus that causes AIDS, globally; 25 million have died from it. While there’s no vaccine, cocktails of powerful antiviral drugs called antiretroviral therapy (ART) can keep the virus suppressed and keep patients healthy. No matter how long patients take ART, however, they are never cured. The virus lurks in the body and comes back if the drugs are stopped. Scientists want to flush out these so-called reservoirs and find a way to kill the virus for good.

Brown, and now these two other men, offer some real hope.

Dr. Timothy Henrich and colleagues at Brigham and Women’s Hospital launched a search about a year ago for HIV patients with leukemia or lymphoma who had received bone marrow stem cell transplants. Bone marrow is the body's source of immune system cells that HIV infects and it’s a likely place to look for HIV’s reservoirs.

“If you took an HIV patient getting treated for various cancers, you can check the effect on the viral reservoirs of various cancer treatments,” Kuritzkes, who works with Henrich, said. They found the two patients by asking colleagues at Dana-Farber Cancer Institute in Boston which, like Brigham and Women’s, is associated with Harvard Medical School.

Both men had endured multiple rounds of treatment for lymphoma, both had stem cell treatments and both had stayed on their HIV drugs throughout. “They went through the transplants on therapy,” Kuritzkes said.

It turns out that was key.

“We found that immediately before the transplant and after the transplant, HIV DNA was in the cells. As the patients’ cells were replaced by the donor cells, the HIV DNA disappeared,” Kuritzkes said. The donor cells, it appears, killed off and replaced the infected cells. And the HIV drugs protected the donor cells while they did it.

One patient is HIV-free two years later, and the other is seemingly uninfected three-and-a-half years later.

“They still have no detectable HIV DNA in their T-cells,” Kuritzkes said. In fact, doctors can’t find any trace of HIV in their bodies -- not in their blood plasma, not when they grow cells in the lab dishes, not by the most sensitive tests.

Can the patients be told they are cured?

“We’re being very careful not to do that,” Kuritzkes said.

For now, both men are staying on AIDS drugs until they can be carefully taken off under experimental conditions. "We are not saying, “You are like the Berlin patient’.”

Although the men are HIV-free, Kuritzkes says it's been an arduous experience for them. After being diagnosed HIV-positive, one underwent rounds of chemotherapy for Hodgkin’s disease, a kind of lymphoma, before receiving the final bone marrow transplant, called an allogeneic bone marrow transplant. It is not an easy treatment to endure.

The men, one from Boston and one from New York, were not initially told their HIV had seemingly disappeared. When researchers realized news media would cover the report, they were informed.

Neither man is being identified for privacy reasons but one is in his 50s and has been infected since the beginning of the AIDS epidemic in the early 1980s. The other man, in his 20s, was infected at birth.

The findings may not apply to all patients. Both men were a little unusual in that they had a genetic mutation that can make immune cells resistant to infection by HIV. Their new immune cells, however, which came from the donors, are fully susceptible to the virus.

“We’re never really going to be able to do bone marrow transplants in the millions of patients who are infected,” Kuritzkes said. “But if you can stimulate the virus and eliminate those cells, we can protect the remaining cells from being infected.”

Separately, two other studies presented at the conference have scientists optimistic about a cure. In one, a cancer drug called vorinostat flushed out latent HIV from a handful of patients, offering the possibility of killing these latent reservoirs. In another, about 15 French patients who got HIV drugs very early after their infections were able to stop treatment and don’t show any symptoms years later, even though they are still infected.

Organizers of the conference say the findings provide an argument for treating patients early. “(These studies) give us reason for enthusiasm, that ultimately we are going to get to where we needed to go, which is to cure people  with HIV infection,” said Dr. Steven Deeks, an HIV expert at the University of California, San Francisco.

More from AIDS conference:

'It was almost painless': Circumcision advocate tackles cringe factor
Yes, you can use pills to prevent AIDS, review finds
The female face of HIV -- not who you might think

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Photos: AIDS conference in Washington DC

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  1. People look at quilts in memory of AIDS victims at the "Keep the Promise" rally of AIDS advocates in Washington on July 22. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, a leading U.S. expert in the AIDS pandemic, said there is "no excuse" scientifically for not putting an end to the disease that has killed some 30 million people since it emerged in the 1980s. Speaking to reporters on the first day of the International AIDS Conference in the nation's capital, Fauci said science has the tools needed to combat HIV/AIDS. (Nicholas Kamm / AFP - Getty Images) Back to slideshow navigation
  2. U.S. Secretary of State Hillary Clinton speaks during the 19th International AIDS Conference in Washington D.C. (Jim Watson / AFP - Getty Images) Back to slideshow navigation
  3. Geojina Gutierrez, right, of Mexico City walks in the AIDS March in Washington, D.C., on July 22. (Jacquelyn Martin / AP) Back to slideshow navigation
  4. British pop icon Elton John walks to the podium to read names appearing on the AIDS Quilt on the National Mall on July 23 as part of the 19th International AIDS Conference in Washington, D.C. The conference is expected to draw 25,000 people, including politicians, scientists and activists, as well as some of the estimated 34 million people living with HIV who will tell their stories. (Karen Bleier / AFP - Getty Images) Back to slideshow navigation
  5. Adrian Gonzalez, an employee of the Condom Project, sets up a display at the International AIDS 2012 Conference in Washington, D.C., on July 23. The Condom Project (TCP) was established by a group of AIDS educators, activists and artists who work to de-stigmatize condoms among all people and to increase their use among sexually active individuals. (Kevin Lamarque / Reuters) Back to slideshow navigation
  6. Co-founder and Chairman of the Bill and Melinda Gates Foundation Bill Gates speaks alongside World Bank President Jim Yong Kim during the 19th International AIDS Conference in Washington, D.C. on July 23. (Jim Watson / AFP - Getty Images) Back to slideshow navigation
  7. Sex workers from around the world attend the Sex Workers' Freedom Festival in Calcutta, India, on July 22. Sex workers and social activists from 42 countries are congregrating in the city to participate in the weeklong festival organized to protest against the U.S. government's travel restrictions on sex workers wanting to attend the Intenational AIDS Conference in Washington, D.C. (Dibyangshu Sarkar / AFP - Getty Images) Back to slideshow navigation
  8. HIV-positive patient Aaron Laxton of St. Louis, center right, and other activists participate in a march from the Washington Convention Center to the White House on July 24, in Washington, D.C. AIDS activists from organizations all around the world participated in the march to "demand rights and resources to confront and cure HIV/AIDS." (Alex Wong / Getty Images) Back to slideshow navigation
  9. AIDS activists tie money and pill bottles to the White House fence. (Shawn Thew / EPA) Back to slideshow navigation
  10. AIDS activists are arrested by U.S. Park Police in front of the White House after marching from the 19th International AIDS Conference in Washington, D.C. (Shawn Thew / EPA) Back to slideshow navigation
  11. Bob Bowers of Madison, Wis., weeps as names of AIDS victims are read aloud at the AIDS Memorial Quilt on the National Mall in Washington, D.C. on July 24. Bowers, who has been HIV positive for 30 years, has lost dozens of friends to AIDS. (Kevin Lamarque / Reuters) Back to slideshow navigation
  12. Timothy Ray Brown, left, known as the 'Berlin Patient,' is the only person to have been cured of AIDS. He is greeted while waiting to enter a press conference to announce the launch of the Timothy Ray Brown Foundation at the Westin City Center hotel in Washington, D.C. "I wouldn't wish this on my worst enemy," Brown said of the treatment process that eventually cured him. (T.j. Kirkpatrick / Getty Images) Back to slideshow navigation
  13. Thousand of activists, sex workers and their children -- with many of them carrying symbollic red umbrellas -- attend a rally as a part of the International AIDS Conference organized by the Durber Mahila Samannay Committee in the Sonagachi redlight district in Calcutta, eastern India. A six-day conference is being held in Calcutta with hundreds of sex workers gathering from 30 countries to oppose the U.S. decision to not grant them travel visas. (Piyal Adhikary / EPA) Back to slideshow navigation
  14. Children of Indian sex workers gesture as they participate in a rally as part of the Sex Workers' Freedom Festival in Calcutta, India. (Dibyangshu Sarkar / AFP - Getty Images) Back to slideshow navigation
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