Longitudinal sampling is required to maximize detection of intrahost A/H3N2 virus variants

Seasonal human influenza viruses continually change antigenically to escape from neutralizing antibodies. It remains unclear how genetic variation in the intrahost virus population and selection at the level of individual hosts translates to the fast-paced evolution observed at the global level because emerging intrahost antigenic variants are rarely detected. We tracked intrahost variants in the hemagglutinin and neuraminidase surface proteins using longitudinally collected samples from 52 patients infected by A/H3N2 influenza virus, mostly young children, who received oseltamivir treatment. We identified emerging putative antigenic variants and oseltamivir-resistant variants, most of which remained detectable in samples collected at subsequent days, and identified variants that emerged intrahost immediately prior to increases in global rates. In contrast to most putative antigenic variants, oseltamivir-resistant variants rapidly increased to high frequencies in the virus population. Importantly, the majority of putative antigenic variants and oseltamivir-resistant variants were first detectable four or more days after onset of symptoms or start of treatment, respectively. Our observations demonstrate that de novo variants emerge, and may be positively selected, during the course of infection. Additionally, based on the 4–7 days post-treatment delay in emergence of oseltamivir-resistant variants in six out of the eight individuals with such variants, we find that limiting sample collection for routine surveillance and diagnostic testing to early timepoints after onset of symptoms can potentially preclude detection of emerging, positively selected variants.

The significance of low-level viraemia in diverse settings: analysis of the Treat Asia HIV Observational Database (TAHOD) and the Australian HIV Observational Database (AHOD)

OBJECTIVES

The aim of the study was to assess the significance of low-level viraemia (LLV) and the timing of treatment change in low/middle-income country (L/MIC) compared with high-income country (HIC) settings.

METHODS

Patients with virological control following commencement of combination antiretroviral therapy (cART) were included in the study. LLV was defined as undetectable viral load (<50 HIV-1 RNA copies/mL) followed by confirmed detectable viral load < 1000 copies/mL. Virological failure was defined as viral load > 1000 copies/mL. Kaplan-Meier plots of time to virological failure by prior LLV and income category were generated. Regimen changes in the setting of LLV were compared between sites. Sensitivity analysis of rates of LLV and virological failure by person-years and number of tests was conducted for differing definitions of LLV and virological failure.

RESULTS

A total of 1748 patients from HICs and 823 patients from L/MICs were included in the study. One hundred and ninety-six (11.2%) HIC participants and 36 (4.4%) L/MIC participants experienced at least one episode of LLV. Of the patients who underwent regimen switch in HIC settings, the majority changed from a nucleoside reverse transcriptase inhibitor (NRTI)/protease inhibitor (PI) regimen to an NRTI/nonnucleoside reverse transcriptase inhibitor (NNRTI) regimen (26.8%). Very few switches were made in L/MIC settings. Rates of LLV were significantly higher for HICs compared with L/MICs per 1000 person-years (28.6 and 9.9 per 1000 person-years, respectively), but not in terms of the number of tests (9.4 and 7.2 per 1000 tests, respectively). Rates of virological failure per test were significantly higher for L/MICs compared with HICs (30.7 vs. 19.6 per 1000 tests, respectively; P < 0.001). LLV was a significant predictor of virological failure at 2 years in L/MICs [0.25; 95% confidence interval (CI) 0.11-0.50; P = 0.043] but not in HICs (0.13; 95% CI 0.08-0.22; P = 0.523).

CONCLUSIONS

LLV is weakly predictive of virological failure at 2 years in L/MICs but not in HICs. This suggests that interventions targeted at subjects with LLV in L/MICs would help to improve treatment outcomes.

Correlates of non-adherence to antiretroviral therapy in a cohort of HIV-positive drug users receiving antiretroviral therapy in Hanoi, Vietnam

The HIV epidemic in Vietnam is concentrated, with high prevalence estimates among injection drug users and commercial sex workers. Socio-demographics, substance use and clinical correlates of antiretroviral therapy non-adherence were studied in 100 HIV-1 infected drug users receiving antiretroviral therapy for at least 6 months in Hanoi, Vietnam. All study participants were men with a mean age of 29.9 ± 4.9 years. The median duration on antiretroviral therapy was 16.2 ± 12.7 months; 83% reported 'very good' or 'perfect' adherence in the past 30 days on a subjective one-item Likert scale at time of study enrollment; 48% of participants reported drug use within the previous 6 months, with 22% reporting current drug use. Injection drug use with or without non-injection drug use in the past 6 months (95% C.I. 2.19, 1.30-3.69) and years on antiretroviral therapy (95% C.I. 1.43, 1.14-1.78) were correlated with suboptimal adherence. These findings support Vietnam's ongoing scale-up of harm reduction programmes for injection drug users and their integration with antiretroviral therapy delivery. Moreover, results highlight the need to identify and implement new ways to support high levels of antiretroviral therapy adherence as duration on antiretroviral therapy increases.