Researchers have published a new study this week suggesting an important component of the immune system damaged by AIDS can possibly be replaced. Specifically, researchers at the Vaccine and Gene Therapy Institute (VGTI) at Oregon Health & Sciences University (OHSU) have been able to promote T-cell regeneration in a study involving rhesus macaque monkeys.
As previous research has demonstrated, HIV attacks the host’s immune system, including an important category of T cells critical for fighting infection called CD4+ T cells.
The virus specifically destroys those CD4+ T cells that reside in the tissues of the body — like the intestine and lung — that interface with the outside environment. As HIV replicates in the human body, the tissue levels of CD4+ T cells are killed and, when the number of these cells drop below a certain level, a patient develops AIDS. At this point, the patient’s immune system is weakened enough to allow infections caused by bacteria, viruses, fungi and parasites that are normally held at bay by a healthy human body. The infected body’s inability to fight off these “intruders,” leads to death.
“To learn more about HIV, its impacts and possible treatments, we study simian immunodeficiency virus (SIV), a close relative of HIV that infects and causes AIDS in nonhuman primates,” explained the study’s lead author Louis Picker, Ph.D. Picker serves as director of the VGTI’s vaccine program and associate director of the VGTI. He is also a professor of pathology, and molecular microbiology and immunology in the OHSU School of Medicine; and director of the Division of Pathobiology and Immunology at the OHSU Oregon National Primate Research Center.
“What we were able to discover using SIV-infected monkeys was that a certain naturally occurring protein called interleukin-15 (IL-15) caused a dramatic restoration of tissue CD4+ T cells when given in conjunction with antiretroviral drugs.”
Antiretroviral drugs are currently given to HIV-positive patients and are shown to slow the proliferation of the HIV virus, allowing patients to live longer. This research clearly demonstrated the importance of retroviral drugs in allowing for restoration of T cell population. This was done by observing SIV-positive animals that received IL-15 without antiretroviral drugs. This group of animals did not demonstrate the same improvements in T cell levels witnessed in animals receiving both IL-15 and antiretroviral drugs.
“What we now need to better understand is how populations of these crucial T cells are regulated,” explained Picker. “We’re also hopeful that this research will lead to effective therapies for treating patients with HIV and boosting their immune systems, making them less susceptible.”