Center for HIV/AIDS Vaccine Immunology (CHAVI) in its fourth
year of funding continues to inform new approaches to HIV
vaccine design through discovery of new knowledge about HIV
infection. Earlier CHAVI studies described a “bottleneck” effect
during HIV transmission: A swarm of HIV variants invade the
mucosal surface, but only a few of those viruses initiate
infection. The Viral Sequencing Core led by Dr. Beatrice Hahn
provided the first detailed look at the envelope gene sequence
of the HIV virus that initiates productive infection in the
host. The team sequenced 3451 envelope genes of HIV variants
from 102 subjects infected with clade B-HIV for less than 25
days; their immune systems had not yet produced antibodies to
HIV circulating in their blood. Using an elegant mathematical
model the researchers determined the resemblance between the
envelope sequences of the isolated viruses and the initial
infecting virus. The model used three simple assumptions: With a
genome of 10,000 nucleotides, the circulating