Figure 3.

Phylogenetic trees constructed by using the neighbor-joining method and V3 nucleotide sequences from patients 125, 127, 129, 134, and 224. □, sequences obtained from samples drawn 100–200 days before start of ritonavir treatment; ○, sequences obtained at start ■, sequences obtained early after start; and •, sequences obtained later after start. “NSI” and “SI” denote sequences from patient 129 with nonsyncytium-inducing and syncytium-inducing phenotypes, respectively. The trees were rooted against the database sequence JRCSF, and the length of branch leading to the root has been shortened by a factor of 2.