1. METHODS Subtype B and F1 PR sequences were matched by average exposure time to PI. Demographic and clinical data were take into account as much as possible. Statistical analyses were performed with Fisher´s exact, Student t and Mann-Whitney U tests, p < 0.05 was considered significant. Differential Resistance Mutation and Polymorphism Acquisition in HIV-1 Protease of Subtypes B and F1 from Children and Adult Patients Ana Teresa Dumans, Cláudia C. Barreto, André F. Santos, Mônica B. Arruda, Thatiana M. Sousa, Esmeralda A. Soares, Adriana O. Afonso, Elizabeth S. Machado, Ester C. Sabino, Alberto Duarte, Rodrigo M. Brindeiro, Amilcar Tanuri and Marcelo A. Soares

2. RESULTS Subtype F1 contained a higher proportion of other polymorphisms. V82L was present in isolates from children. In untreated patients, L63P, A71T, and V77I were more prevalent in subtype B, while L10V, K20R, and M36I in subtype F1. In treated patients, K20M, D30N, G73S, I84V, and L90M were more prevalent in subtype B, while K20T and N88S in subtype F1.

3. CONCLUSIONS Differences in treatment regimens and in viral replication rates may play a role in the differences between drug resistance acquisition in adults and children. Rates of overall drug resistance did not differ between subtypes B and F1 but subtype B accumulates resistance at higher proportion in specific amino acid positions.