Researchers at the partners AIDS Research Center at Massachusetts General Hospital said that when individuals infected with HIV become infected with a second strain of the virus, the two viral strains can exchange genetic information, creating a third, recombinant strain of the virus.

These multiple viral strains, called superinfection, frequently lead to a loss of immune control of viral levels.

"The implication that recombination events are selected by immune responses identifies a new mechanism for the virus to escape the patient's immune system, which would present additional challenges to vaccine design," one of the study's lead authors, Dr. Hendrik Streeck, said in a statement.

"This finding also has worldwide implications for the development of more complex strains of HIV."

The study is published online in the Journal of Experimental Medicine.