1. Laboratory of Genomic Diversity, Science Applications International Corporation-Frederick,
2. Tumor Immunology Department, University Medical Center St. Radbound, Nijmegen 6525 EX, The Netherlands
3. Intramural Research Support Program, Science Applications International Corporation-Frederick,
4. HIV Drug Resistance Program, National Cancer Institute-Frederick, Frederick, Maryland 21702
5. Zentrum für Moleculare Biologie Heidelberg (ZMBH), D-69120 Heidelberg, Germany