Drug-resistant variants are frequently present in both recently and chronically infected therapy-naive patients. Drug-resistant variants are most commonly seen in patients infected with subtype B virus, probably because of longer exposure of these viruses to drugs. However, an increase in baseline resistance in non-B viruses is observed. These data argue for testing all drug-naive patients and are of relevance when guidelines for management of postexposure prophylaxis and first-line therapy are updated.

Background: The prevalence and the origin of HIV-1 subtype B, the most prevalent circulating clade among the long-term residents in Europe, have been studied extensively. However the spatial diffusion of the epidemic from the perspective of the virus has not previously been traced.

Based on the calculated genetic barrier, the rate of drug resistance development may be similar for different HIV-1 subtypes. Because of differences in minor protease substitutions, protease inhibitor resistance could be enhanced in particular subtypes once the relevant major substitutions are selected.

Changes in plasma 4beta-hydroxycholesterol following the initiation of efavirenz- or atazanavir/ritonavir-based antiretroviral therapy reflected the respective net increase and decrease of CYP3A activity of these regimens. The plasma 4beta-hydroxycholesterol level did not indicate a net CYP3A inhibition in the lopinavir/ritonavir arm, possibly because of concomitant enzyme induction.

This study prospectively assessed the impact of treatment modality, virus load, and CD4 cell count of <50 cells/mm(3) on human immunodeficiency virus disease progression. The incidence rate of new AIDS disease or death was 54.8 (95% confidence interval, 48.7-59.9) per 100 person-years of follow-up. Independent predictors related to progression were latest CD4 cell count (relative risk [RR], 0.84/10 mm(3) higher; P<.0001), latest hemoglobin level (RR, 0.79/g/L higher; P<.0001), Pneumocystis carinii pneumonia prophylaxis (RR, 0.49; P<.0001), latest body mass index (RR, 0.93/kg/m(2) higher; P=.002), latest virus load (RR, 1.11/log(10) higher; P=.03), and intensity of treatment (RR, 1.82, P=.004; RR 2.27, P<.0001; RR 2.46, P=.0001; RR 2.33 P<.0006; 5.10, P<.0001, respectively, for 4, 3, 2, 1, or no drugs vs. >or=5 drugs). Although reverse causality cannot be excluded, more intense antiviral treatment appears to decrease the risk of progression in immunocompromised patients.