Figure 1.

Phylogenetic analysis of 157 envelope gp41 sequences from five mother-infant pairs following perinatal transmission. The neighbor-joining tree is based on the distances calculated between the nucleotide sequences from the five mother-infant pairs. Each terminal node represents one gp41 sequence. The numbers on the branch points indicate the percent occurrences of the branches over 1000 bootstrap resamplings of the data set. The sequences from each mother formed distinct clusters and are well discriminated and in confined subtrees, indicating that variants from the same mother are closer to each other than to other mothers' sequences and that there was no PCR cross contamination. These data were strongly supported by the high bootstrap values indicated on the branch points.