RESEARCH METHODS Study Design Observational, Retrospective, Single-center, Single-arm Study of patients treated with raltegravir plus abacavir and lamivudine.
Subject Selection: Inclusion Criteria All consecutive patients fulfilling the following inclusion criteria will be considered: * HIV-1 infected patients, * age \> 18 years, * Human leukocyte antigen (HLA) B5701-negative * treatment-experienced patients with viral suppression (HIV-RNA \<50 copies/mL), who switched from any antiretroviral drug to raltegravir plus abacavir and lamivudine because of toxicity, convenience or other reasons * switch from Protease Inhibitor to Raltegravir in patients on Abacavir and lamivudine, switch from any Nucleoside analog reverse-transcriptase inhibitors (NRTI) combination to abacavir and lamivudine in patients on raltegravir, switch to raltegravir plus abacavir and lamivudine from any other combination will all allow the inclusion in the study * At least one viral load assessed before and at least once after starting the study regimen. Subject Selection: Exclusion Criteria * Documented drug-resistance or virological failure to integrase inhibitors, abacavir or lamivudine before starting the study regimen. * Pregnancy at the start of the study regimen. * HBsAg positive.