Researchers believe that subtype D is more virulent than subtype A because D has the ability to bind to key receptors on immune cells, allowing subtype D to kill more quickly. Additional blood analysis showed that with subtype A, the virus bound only to one kind of receptor, CCR5, to infect the cell. But 25 percent of subtype D virus bound to both CCR5 and another receptor, CXCR4. Indeed, two-thirds of those infected with CXCR4-binding virus died within three years.
According to the study's lead researcher, Oliver Laeyendecker, M.S., M.B.A., a senior research associate at The Johns Hopkins University School of Medicine and senior research assistant at the National Institute of Allergy and Infectious Disease, "Knowing a person's HIV subtype is important for the management of the infection because the disease can progress more rapidly in those infected with subtype D and recombinant virus incorporating subtype D than in those with other subtypes."
The Effect of HIV Subtype on Rapid Disease Progression in Rakai, Uganda. Oliver Laeyendecker, Xianbin Li, Miguel Arroyo, Francine McCutchan, Ron Gray, Maria Wawer, David Serwadda, Fred Nalugoda, Godfrey Kigozi, and Thomas Quinn.