Researchers at Brigham Young University are trying to unlock some of the mysteries surrounding the virus that causes AIDS with a trio of studies addressing unusual cases involving a set of twins, a failed vaccine and a protein "stop sign."The twin identical baby boys received a tainted transfusion and both became HIV-positive a few years ago.Now, one of the twins has a near-normal immune system and pretty good health, while the other boy is five years behind him on the growth chart and has experienced a number of complications.That provocative difference became the foundation of one of the studies, as researchers led by BYU biology department chairman Keith Crandall try to figure out how the virus changed in each twin. They've been joined in the study by scientists at the National Cancer Institute.Crandall said there are competing theories about the differences in their clinical outcomes. One theory is that natural selection drives it, so the results should be similar. The other holds that random genetics plays a role and it therefore cannot be predicted.A second study focuses on an HIV vaccine scientists in Thailand were trying to develop that proved ineffective. Crandall said they hope samples from that case will help them learn more about how the virus evolved and whether vaccinations to guard against HIV show promise."I think the HIV community is still split in terms of how to pursue treatment against HIV infection," Crandall told the Deseret News."There is a strong camp that thinks vaccine is still the way to go. We need to do more intelligent vaccine design," carefully considering everything they've learned in other attempts to create a vaccine that works."Others say no way," he said. "The focus needs to be on drug therapy. But the virus tends to hide out in places where drugs can't get to them."The final study is led by Greg Burton, chairman of BYU's Department of Chemistry and Biochemistry, and Xueyuan Zho, a student at the University of Colorado's Health Sciences department. They confirmed an earlier report that a naturally occurring protein prevents HIV from multiplying. But they've gone further to explain how the protein works, not just what happens."The importance of this study is that we moved ahead from earlier research. The effect was known, but we showed the mechanism," Burton said.