Researchers at Oregon Health and Science University (OHSU) have developed a candidate vaccine that appears to completely clear an AIDS-causing virus from the body. Developed at OHSU's Vaccine and Gene Therapy Unit, the vaccine is now being tested through a non-human primate form of HIV, called simian immunodeficiency virus (SIV). It is hoped that an HIV-form of the vaccine will soon be tested on humans.
The only instances in which HIV infection has been cured to date involved a very small number of highly-publicized, unusual clinical cases. In these situations, individuals with HIV were treated with anti-viral medicines shortly after becoming infected, or received a stem cell transplant. According to Louis Picker, the associate director of the Vaccine and Gene Therapy Institute, this vaccine may elicit certain immune responses, which may have the ability to eradicate HIV from the body.
The approach the researchers used involved a common virus, know as cytomegalovirus (CMV), which is carried by a large part of the population. Pairing CMV with SIV was found to have a unique effect. Modifying CMV to express SIV proteins, generated T-cells, a key component of the body's immune system, which were able to locate and destroy SIV-infected cells.
T-cells elicited by SIV itself are not capable of eliminating the virus. However, this was not the case with SIV-specific T-cells elicited by the modified CMV. After receiving the candidate vaccine, roughly half of the monkeys in the trial who were infected with SIV experienced a total eradication of the infection over time. The researchers describe it as providing the T-cells with an improved targeting system and weapons to destroy an elusive enemy.
In essence, this method provides the body with a way to better prepare its defenses in combating the disease. The vaccine mobilizes a T-cell response that is capable of overtaking SIV invaders in half of the cases treated. What's more, the cases that did see a positive response experienced total removal of SIV from the host. The researchers are hopeful that pairing their modified CMV vector with HIV will produce a similar result in humans.
Currently, researchers are investigating why only a subset of the treated animals showed a positive response to the vaccine. In doing so, the team hopes to boost the vaccine's effectiveness.
