1. Department of Virology, University of Göteborg, S-413 46 Göteborg, Sweden.
2. Department of Hematology, University of Göteborg, S-413 45 Göteborg, Sweden.
3. Department of Surgery, Umeå University Hospital, S-901 85 Umeå, Sweden.
4. Maxim Pharmaceuticals, Inc., San Diego, CA 92122.