[1] UNIV HELSINKI,DEPT MED GENET,SF-00100 HELSINKI 10,FINLAND
[2] UNIV HELSINKI,DEPT VIROL,SF-00100 HELSINKI 10,FINLAND
[3] FINNISH POPULAT & FAMILY WELF FEDERAT,DEPT MED GENET,HELSINKI,FINLAND
[4] FINNISH RED CROSS & BLOOD TRANSFUS SERV,BLOOD TRANSFUS SERV,HELSINKI,FINLAND
[5] WHITEHEAD INST BIOMED RES,DEPT MED GENET,CAMBRIDGE,MA