High accuracy and precision at the lower end of quantification are crucial requirements of a modern HIV viral load (VL) assay, since some clinically relevant thresholds are located at 50 and 200 copies/ml. In this study, we compared the performance of two new fully automated HIV-1 VL assays, Aptima HIV-1 Quant Dx and Cobas HIV-1 (Cobas 6800), with the established RealTi m e m 2000 assay.

Objectives The incidence of sexually transmitted hepatitis C virus (HCV) reinfection is on the rise in HIV-infected men who have sex with men (MSM). Data on natural history of acute hepatitis C and possible factors associated with spontaneous clearance are limited. The aim of this study was to analyse the outcome of HCV reinfections in HIV-positive MSM. Methods A retrospective analysis was carried out on patients with more than one sexually acquired HCV infection who were diagnosed at four major German HIV and hepatitis care centres. Reinfection was defined by genotype or phylogenetic clade switch, detectable HCV RNA after a sustained virological response (SVR) or after spontaneous clearance (SC). Results In total, 48 HIV-positive MSM were identified with HCV reinfection, among them 11 with a third episode and one patient with four episodes. At the first episode, 43 and five patients had an SVR and SC, respectively. The second episode was accompanied by a genotype switch in 29 patients (60%). Whereas 30 and nine patients showed an SVR and SC, respectively, eight patients developed chronic hepatitis. Neither HCV genotype switch nor interleukin-28B genotype was associated with SC. However, SC rates at the second episode were higher for patients with SC at the first episode compared with patients without SC (60 vs. 14%, respectively; P=0.03). Two patients with SC at the first episode were reinfected with the same genotype. Conclusions Multiple reinfections in HIV-infected MSM do occur, with or without genotype switch, and with prior SC of previous episodes. In this large case series, except for SC at the first episode, no factor was of value in clinical decision-making for early therapeutic intervention in acute HCV reinfection.

Purpose of the studyDetermination of HIV‐1 coreceptor tropism is a major prerequisite before starting treatment with a CCR5‐antagonist. While most of the patients currently under treatment with maraviroc are probably infected with HIV‐1 subtype B viruses, recently published data show differences in the distribution of coreceptor tropism in different HIV‐1 subtypes.MethodsIn a Germany‐wide project within the HIV‐GRADE society, V3‐loop sequences of 2466 isolates were analysed with geno2pheno for coreceptor tropism using a FPR cut‐off of 10%. HIV‐1 subtype was determined by using the COMET HIV subtyping tool. Sequences consisted of at least the V3 loop fragment. The ratio of CCR5 vs CXCR4 tropic viruses was calculated for each subtype. A normalized mean for all analyzed subtypes was calculated to extrapolate the overall ratio of coreceptor usage distribution. From this the expected distribution in the particular subtype was calculated and compared to the observed one. Statistical analysis was performed using the chi2 test.Summary of ResultsMost samples were classified as HIV‐1 subtype B (79%, n=1952). Other subtypes present in at least 23 samples were A1 (9.5%, n=234), C (4.8%, n=118), CRF01_AE (2.2%, n=55), G (1.6%, n=39), D (1.1%, n=27), F (0.9%, n=23). The calculated normalized mean distribution over all subtypes was 71% CCR5‐ vs. 29% CXCR4‐tropic viruses. No significant difference compared to the mean distribution could be observed for HIV‐1 subtypes B (71/29%), C (76/24%) and F (70/30%). Higher rates of CXCR4 tropic virus were detected in subtypes D (52/48%, p=0.01) and CRF01_AE (49/51%, p=0.001), while in HIV‐1 subtypes A1 (22/78%, p=0.02) and G (13/87%, p=0.02), a higher rate of CCR5‐tropic virus was observed.ConclusionsOur analysis shows a different distribution of CCR5 and CXCR4 tropic virus in some subtypes. In contrast to other publications, we could not observe a statistically significant difference in subtype C compared to the overall mean distribution, while we could confirm a higher rate of CXCR4‐tropic virus in subtype D, as previously described. Without further data on treatment success of patients with non‐B subtypes under treatment with maraviroc, it remains unclear if subtype‐specific differences in the distribution of tropism are biased by differences in clinical variables before test or if there is a bias in the tropism interpretation system. In the latter case, individual interpretation cut‐offs for different subtypes may be necessary.

7‐11 November 2010, Tenth International Congress on Drug Therapy in HIV Infection, Glasgow, UK

Address: 1Medizinisches Labor Dr. Berg, Berlin, Germany, 2University of Cologne, Cologne, Germany, 3PZB Aachen, Aachen, Germany, 4Medizinisches Labor Dr. Thiele, Kaiserslautern, Germany, 5NRZ fur Retroviren, Erlangen, Germany, 6Labor Lademannbogen, Hamburg, Germany, 7MUC-Research, Munich, Germany, 8Labor Dr. Fenner, Hamburg, Germany, 9University of Frankfurt, Frankfurt, Germany and 10MPI for Bioinformatics, Saarbrucken, Germany * Corresponding author

Background Drug toxicities are limiting factors for the lifelong therapy of HIV infection. The CCR5 receptor antagonist maraviroc showed no long-term toxicities so far. Thus switching from a virologically successful but not well tolerated regimen to maraviroc might be an future option. However, testing of viral tropism is mandatory before the use; tests require a plasma viral load >500 c/ml. In the majority of patients (pts) in larger clinical centers, plasma was frozen before starting antiretroviral therapies. These samples would be available to define viral tropism if it can be excluded that viral tropism changes during virological successful therapy.