What are Immune-Based Therapies?
AIDS researchers have primarily concentrated on finding drugs that prevent HIV from replicating (creating more virus) inside the body. These drugs are often referred to as "antiretrovirals." However, there’s also been interest in developing treatments that can bolster the immune system’s ability to fight HIV on its own, potentially without the long-term use of antiretrovirals. These are called immune-based therapies (IBTs).
One approach is to reproduce important proteins, called "cytokines", that help regulate a person's immune system, then use them to stimulate or inhibit the growth and activity of various immune system cells. The most tested treatment using this approach is Proleukin, a high-tech recreation of interleukin-2 (IL-2), a naturally occurring cytokine that stimulates the production of CD4 cells. There is also interleukin-7 (IL-7), which may not only stimulate CD4 cell production, but also help reduce or eradicate a reservoir of HIV-infected cells that typically escape both the immune system and common HIV medications.
Another approach is the use of "therapeutic vaccines". While traditional vaccines are used to "prime" a person's immune system before a possible infection occurs, therapeutic vaccines attempt to "teach" a person's immune system to fight the virus after infection. Two such candidates are Vacc-4x and DermaVir.
Also in development under the umbrella of IBTs are gene therapies. A gene is part of DNA. Humans have between 50,000 and 100,000 genes that regulate how cells behave in the body. That is, genes can either "turn on" or "turn off" virtually any function that a cell is capable of.
Researchers have learned a great deal about the genes responsible for certain cellular activities. This has set the stage for additional research into ways to alter patients' genetic material to fight or prevent diseases. Gene therapy involves introducing genetic material into a person's cells to turn specific functions on or off. In the case of HIV, turning off certain CD4 cell functions may help protect it from becoming infected with HIV or from producing new virus. Alternatively, gene therapy might be used to turn on certain CD4 cell functions, perhaps to cause HIV-infected cells to self destruct or to begin producing HIV so that standard HIV medications can go to work.
Gene therapies for HIV-positive people have been very slow to develop, given their complexities and the potential risks involved. There are, however, several in development. One in particular is SB-728-T, a zinc finger DNA-binding protein transcription factor (ZFP TF). It disrupts the gene responsible for making CCR5 co-receptors on the surface of CD4 cells. When CD4 cells are unable to display produce these co-receptors it is much harder for HIV to infect them. The aim of SB-728-T therapy is to grow a new population of CD4 cells that are resistant to HIV infection, and thus make antiretroviral therapy unnecessary.
While these and other immune-based therapies are being intensively researched, it is important to note that no studies have yet been completed that have proven a clinical benefit (the ability to prolong a person's life).