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[ Watch The Video: Barrier To HIV Cure Bigger Than Previously Thought ]

redOrbit Staff & Wire Reports Your Universe Online

Although current treatments for human immunodeficiency virus (HIV) can keep the disease at bay, a larger-than-expected amount of hidden virus may complicate efforts to find a cure, according to the most detailed and comprehensive analysis to date of the latent reservoir of HIV proviruses.

The three-year study, published Thursday in the journal Cell, deals a painful blow to researchers working hard to find a cure for HIV/AIDS, a disease that kills nearly two million people per year according to the World Health Organization (WHO).

Infectious disease experts at John Hopkins found that the amount of potentially active, dormant forms of HIV hiding in infected immune T cells may actually be 60 times greater than previously thought.

This hidden HIV is part of the so-called latent reservoir of functional proviruses that remains long after antiretroviral drug therapy has successfully brought viral replication to a standstill. If antiretroviral therapy is stopped or interrupted, some proviruses can reactivate, allowing HIV to make copies of itself and resume infection of other immune cells, the researchers said.

Senior study investigator Robert Siliciano, M.D., Ph.D., who in 1995 first showed that reservoirs of dormant HIV were present in immune cells, said that while the current studys results show most proviruses in the latent reservoir are defective, curing the disease will depend on finding a way to target all proviruses with the potential to restart the infection.

These results indicate an increased barrier to cure, as all intact noninduced proviruses need to be eradicated, Siliciano said. Although cure of HIV infection may be achievable in special situations, the elimination of the latent reservoir is a major problem, and it is unclear how long it will take to find a way to do this.

The studys results showed that among 213 HIV proviruses that were isolated from the reservoirs of eight patients and that were initially unresponsive to highly potent biological stimuli, some 12 percent could later still become active and capable of replicating their genetic material and transmitting infection to other cells. All of these non-induced proviruses had previously been thought to be defective, with no possible role in resumption of the disease, said Siliciano, a professor at the Johns Hopkins University School of Medicine and a Howard Hughes Medical Institute investigator.

These disappointing findings pose a serious problem to prevailing hopes for the so-called shock and kill approach to curing HIV, he said. That approach refers to forcing dormant proviruses to turn back on, making them visible and vulnerable to the immune systems cytolytic killer T cells, and then eliminating infected cells from the body while antiretroviral drugs prevent any new cells from becoming infected.

Read more from the original source:
HIV's Secret Hideout Frustrates Efforts To Develop A Cure