Long-term benefit of genotypic-guided therapy and prevalence of multinucleoside resistance in an Italian group of antiretroviral multiexperienced patients.

Multiple nucleoside resistance involves specific genetic changes in the HIV-1 reverse transcriptase gene, such as Q151M mutation and an insertion of two serine aminoacids at RT codon 69. Among 432 patients failing antiretroviral therapy, five (1.15%) harboured viruses with Q151M mutation into the RT gene and no viruses were identified harbouring insertion at codon 69. Also we have studied the long-term benefit of HIV genotypic testing with the failure to reach a viral load below 50 copies/ml within 1 year of antiretroviral therapy using as the primary end-point. A group of 64 HIV-positive antiretroviral multiexperienced patients were examined, all of them failing the current ART. HIV-RNA changed -0.8 log at month 4 and +0.1 log and -0.5 log at months 8 and 12, respectively. The proportion of patients with viral load below 50 copies/ml was 19.3, 32.8, and 28.1% at months 4, 8, and 12, respectively. In multidrug-experienced patients, genotype-guided therapy is not in fact able to achieve complete viral suppression in more than 30% of patients after 1 year of ART. The development of more precise resistance tests and interpretations are needed for better control of HIV replication. Other metabolic/pharmacokinetics factors of poor drug adherence should also be assessed.