| 'Hide and seek' costly to HIV|
|In an effort to avoid our immune system, HIV plays a game of hide and seek that at times makes it vulnerable, says a new Australian study.|
The finding may provide insights into the treatment of HIV during the early stages of infection.
When HIV enters a new host it includes a form that researchers call escape mutant.
Research published in the PLoS journal Pathogens reveals that while the escape mutant virus may be better at evading our immune system, it is weaker and replicates slower than the wild-type form.
"When HIV infects a new host it needs to adapt to this new environment," says lead author and PhD student Liyen Loh of the Department of Immunology and Microbiology at The University of Melbourne.
"The mutations often revert to the original wild-type virus, allowing the virus to regain a fitter state, or the changes may be retained, depending on the individual's immune system.
"This explains why some individuals have better clinical outcomes than others."
The researchers from the University of Melbourne and the University of Sydney studied the evolution of the virus using macaque monkeys.
Pressure to change
They infected the animals with different quantities of wild-type SIV (the non-human equivalent of HIV) and escape mutant SIV.
Over the next three months, the researchers measured the growth of the virus to determine the length of time it took for the escape mutant form to revert back to its fitter wild-type state.
"In the absence of immune pressure the virus will not stay in its weakened state, because it is not beneficial for the virus," says Loh.
They found that in animals infected with the escape mutant virus it took 8 days for wild-type to appear, and 8 weeks for them to outnumber the escape mutant form.
They also found that the genetic makeup of the virus affected how fast the virus adapts in the host.
"If [the macaques] get infected with purely one strain of virus it will take longer to adapt to the new host," says Loh.
She says the study only focused on one structural part of the virus that mutates, and that there are many "other bits" that affect how the HIV evolves in an infected individual.