1. Department of Legal Medicine; Graduate School of Medicine; Chiba University; Chiba 260-8670 Japan
2. Department of Molecular Infectiology; Graduate School of Medicine; Chiba University; Chiba 260-8670 Japan
3. Cardiovascular and Pulmonary Branch; National Heart, Lung, and Blood Institute; National Institutes of Health; Bethesda MD 20892-1590 USA