This Week in HIV Research: New Discovery in How HIV Hijacks a Cell
This week, a study finds a key step in how HIV binds to CD4 cells, which could lead to the development of new HIV drugs. Another study finds that most HIV drugs do not lower the effectiveness of hormonal contraceptives for women. And addressing hemostatic changes in HIV-associated tuberculosis could help lower the risk of death. To beat HIV, you have to follow the science!
HIV Hijacks Surface Molecule to Invade Cell
Researchers at the National Institutes of Health (NIH) have discovered a key step in how HIV binds to and infects a cell, according to a new study published in Cell Host & Microbe. The researchers were also able to block this step and prevent HIV from infecting the cell, which could lead to the development of new HIV drugs.
The study found that HIV binds to the surface of a CD4 cell and releases calcium, which activates the protein TMEM16F (from within the cell). TMEM16F then transfers a molecule called phosphatidylserine (PS) to the cell membrane's outer surface. HIV binds to the newly exposed PS and fuses with the cell membrane, entering the cell.
Developing new drugs that block any of these steps could prevent HIV from infecting cells, the researchers noted in the study press release, which also depicts the steps HIV takes to hijack a cell (below).
Most Antiretrovirals Do Not Lower the Effectiveness of Hormonal Contraceptives
Antiretrovirals have little interaction with hormonal contraceptives, a review of 46 studies that was published in AIDS found.
The exception is efavirenz (Sustiva, Stocrin), which may compromise the effectiveness of some hormonal implants and combination pills. Study authors caution that data on contraceptive effectiveness was quite limited in the studies under review. Most used the occurrence of ovulation as a marker for contraceptive efficacy. That marker can be imprecise, especially since women who use levonorgestrel implants tend to ovulate but not become pregnant. None of the studies under review found that hormonal contraceptives impact the effectiveness of antiretroviral therapy.
The drugs used for pre-exposure prophylaxis (PrEP) also did not affect hormonal contraceptives. Given the limited data available, study authors recommend that "women taking antiretrovirals ... should have access to the full range of hormonal contraceptive options." They note that the effectiveness of a contraceptive method is not the only consideration for women when they decide to plan their reproductive lives.
Targeting Hemostatic Changes in HIV-Associated Tuberculosis May Help Lower Mortality
People with HIV-associated tuberculosis (TB) have a greater tendency toward blood clotting and activation of the endothelial cells that line blood vessels than people living with HIV who do not have TB, a study published in The Journal of Infectious Diseases showed.
These mechanisms contribute to the high mortality rate among people living with HIV and TB. Researchers analyzed clinical data and bodily fluid samples of 59 people who were admitted to a South African hospital with HIV-associated TB. They compared these to data from outpatients at the same hospital who live with HIV, but do not have TB.
Study authors believe that the changes in blood clotting and endothelial activation are due to TB rather than HIV, because they were less pronounced in the outpatient group. Results "suggest that treatment strategies targeting hemostasis, endothelial activation and matricellular homeostasis may be of interest" in the treatment of people with severe HIV-associated TB, study authors concluded.