Viral recombination another way HIV fools the immune system

"The first Gag recombination event facilitated escape from the primary immune response, shortly after which the immune response recovered to recognize this mutant strain," Streeck explains. "After the second recombination event and emergence of a more potent mutation, there was a dramatic reduction in the CTL response against both versions, leading to a significant increase in viral loads."

Todd Allen, PhD, of PARC-MGH, the study's senior author adds that, while recombination itself appears to be a random event, recombinant strains that are better able to evade the immune system are likely to become dominant through natural selection. He also stresses that even patients whose immune systems can partially control HIV should avoid a secondary infection that could lead to the development of an uncontrollable, recombinant viral strain.

Streeck notes, "Given the growing frequency of recombinant HIV strains worldwide, we need to better understand how immune system pressures may be driving their development and also determine how frequently patients exposed to a second strain of HIV become superinfected." He is a research fellow in Medicine at Harvard Medical School, where Allen is an associate professor of Medicine.

Additional co-authors of the report are co-lead author Bin Li, PhD, Arne Schneidewind, MD, Adrienne Gladden, Karen Power, Suzane Bazner, RN, Christian Brander, PhD, Eric Rosenberg, MD, and Marcus Altfeld, MD, PhD, of PARC-MGH; Art Poon, PhD, and Simon Frost, PhD, University of California at San Diego; Demetre Daskalakis, MD, New York University School of Medicine; and Rosario Zuniga, PhD, Asociacion Civil IMPACTA Salud y Educacion, Lima, Peru. The study was supported by grants from the National Institutes of Health.

Massachusetts General Hospital (www.massgeneral.org), established in 1811, is the original and largest teaching hospital of Harvard Medical School. The MGH conducts the largest hospital-based research program in the United States, with an annual research budget of more than $500 million and major research centers in AIDS, cardiovascular research, cancer, computational and integrative biology, cutaneous biology, human genetics, medical imaging, neurodegenerative disorders, regenerative medicine, systems biology, transplantation biology and photomedicine.