1. Department of Preventive Environment and Nutrition, Institute of Health Biosciences, University of Tokushima, Tokushima 770-8503, Japan.
2. Department of Microbiology and Parasitology, Gondar College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia.
3. AIDS Research Center, National Institute of Infectious Diseases, Tokyo 2080011, Japan.