Phylogenetic analysis reveals two groups of variations within HSV-1 glycoprotein G by region. The evolutionary history was inferred using the UPGMA method. The tree is drawn to scale, with evolutionary distances in the units of base substitutions per site. There were a total of 165 positions, coding for AA 110 to 164. Phylogenetic analyses were conducted in MEGA4 . Labeled branches represent the number of isolates from the specified region. Sequences shown at the bottom are from the branches highlighted with colored dots, which represent the most common sequence. Positions where sequences V and F differ are in color. The immunodominant region of glycoprotein G is enclosed by a box. The epitope AFPL (underlined, present exclusively in sequence F) is recognized by a common anti-glycoprotein G-1 mAb. The clinical isolate Y3369 discussed herein contains sequence V.