Researchers Hoping That ‘Elite Controller’ Could Help in HIV/AIDS Vaccine Development
An HIV-positive woman who has never shown symptoms of the virus might provide insights into HIV/AIDS vaccine development, researchers from Johns Hopkins University said in a study recently published in the Journal of Virology, Reuters reports.
The woman, a so-called "elite suppressor," contracted HIV 10 years ago from her husband, a former injection drug user. Although her husband takes antiretroviral drugs to control his viral load, the woman does not need to take the drugs to keep her viral load at undetectable levels. The couple, who has been monogamous for at least 17 years, has the same strain of HIV. According to the researchers, the key difference in their ability to control the virus is the woman's immune system.
Joel Blankson, who led the study, said that the role of the woman's immune system is a "good sign in terms of developing a therapeutic vaccine," which would not prevent transmission of the virus but could be used to prevent HIV-positive people from progressing to AIDS (Fox, Reuters, 8/12).
The researchers said the study disproved some theories about elite suppression, including those that claimed such suppression always involved a defective or weakened HIV strain, which is easier for the immune system to attack, or that genetic variants confer a protective effect in suppressors. According to Blankson, "This an extremely rare case of coinfection in a controlled, monogamous relationship, which showed us how a strong immune system in the elite suppressor kept the virus from replicating and infecting other cells." Blankson added, "Our findings offer hope to vaccine researchers because they reveal that the immune system's primary offense, known as CD8 killer T-cells, can effectively halt disease progression by a pathogenic form of HIV" (IANS/Yahoo! News, 8/12).
Tests conducted by the researchers indicate that the woman's CD8 cells stalled HIV replication by as much as 90%, while the man's cells stalled replication by 30%. In an apparent response to this attack by her immune system, the woman's HIV also has mutated to become weaker, while the man's HIV has remained strong, Reuters reports.
According to Blankson, the researchers are trying to figure out how the woman's T-cells work to inhibit viral replication. According to Reuters, the researchers determined that while the man's T-cells make only one kind of cytokines -- which are immune system signaling proteins -- called gamma interferon, the woman's made that one and another called tumor necrosis factor. However, the cytokines cannot explain the woman's ability to suppress HIV, Reuters reports, because HIV/AIDS researchers have tried using such immune system proteins in patients and found they did not work well. Furthermore, the woman's immune cells seem to respond in this manner only when they encounter the virus. Blankson said the case could be explained by the possibility of the woman having unusual activity in her human leukocyte antigen system, which helps recognize bacterial and viral antigens (Reuters, 8/12).
The study is available online.