Monkey studies reveal promising vaccine approach for HIV

Details of this advance are published in the advance online edition of the journal Nature. The paper will also be published in an upcoming print addition of the journal.

The research team, led by Louis Picker, M.D., associate director of the OHSU VGTI and director of the VGTI's vaccine program, produced a vaccine candidate that programs the immune system of non-human primates to respond more swiftly to the presence of a primate version of HIV than it normally would. The team also included researchers from the National Cancer Institute-Frederick and the International AIDS Vaccine Initiative.

The VGTI researchers tested their vaccine candidate in rhesus macaque monkeys at the Oregon National Primate Research Center using a monkey form of HIV called Simian Immunodeficiency Virus (SIV). Of the monkeys that received the vaccine candidate, just more than half controlled replication of the virus to the extent that even the most sensitive tests could not detect signs of SIV.

To date, the vast majority of these animals have maintained control over the virus for more than a year, gradually losing any signs that they had ever been infected. In contrast, the macaques in the unvaccinated control group developed the monkey form of AIDS.

The researchers say that their work suggests that the immune responses elicited by this new vaccine candidate might completely clear SIV from animals that were initially infected. In comparison, antiretroviral therapy is able to control the disease, but cannot clear the virus from its hiding place within the immune systems own cells.

The VGTI team has been working for over ten years on its vaccine candidate, which is unique in using Cytomegalovirus (CMV) as the transport system used to introduce the vaccine into the body. CMV was chosen because it is believed that most people are already infected with CMV, but for the majority, the virus causes little or no symptoms. In addition, once a person is infected with CMV, this virus remains in the body for life. Picker and his team hypothesized that if such a persistent virus were used as a vector it could create and maintain resistance against HIV by programming a portion of the body's immune system called effector memory T-cells to be constantly on the alert for the virus.

"The next step in vaccine development is to test the vaccine candidate in clinical trials in humans. For a human vaccine the CMV vector would be weakened sufficiently so that it does not cause illness, but will still protect against HIV, " said Dr. Picker.

The National Institutes of Health and, the International AIDS Vaccine Initiative provided funding for this research.