Susceptibility of Brazilian influenza A(H1N1)pdm09 viruses to neuraminidase inhibitors in the 2014-2016 seasons: Identification of strains bearing mutations associated with reduced inhibition profile.

Neuraminidase inhibitors (NAIs) are the main class of antivirals currently used for the treatment of influenza infections. As influenza viruses are constantly evolving, drug-resistance can emerge resulting in reduced effectiveness of treatment. This study evaluated the presence of molecular markers associated with NAI susceptibility in 724 influenza A(H1N1)pdm09 positive samples from Brazilian surveillance system from the 2014-2016 seasons, including 76 isolates tested for oseltamivir (OST) susceptibility and 23 isolates also tested for zanamivir, peramivir and laninamivir susceptibility. We identified the H275Y (n = 3) and I223K (n = 1) NA substitutions, associated with reduced inhibition (RI) by the NAIs. Noteworthy, no epidemiological links were identified among the patients infected with the mutant viruses. Phylogenetic analysis from NA and hemagglutinin genes showed that mutant viruses were not clustered. All mutant virus strains carried the permissive substitutions V241I and N369K, in addition to the N386K, which has been shown to destabilize the NA structure. Functional NA analysis of one virus containing the H275Y mutation confirmed its highly RI profile to OST and peramivir and demonstrated that it had decreased viral replication and NA thermostability compared to the wild type virus. The remaining tested isolates presented normal inhibition profile to the NAIs tested. In conclusion, the overall frequency of influenza A(H1N1)pdm09 viruses bearing mutations associated with NAI RI was 0.6%, similar to what has been observed in recent global studies.

Oseltamivir-resistant 2009 H1N1 influenza pneumonia during therapy in a renal transplant recipient.

The emergence of oseltamivir-resistant 2009 H1N1 influenza virus (conferred by the H275Y substitution in NA) during therapy or prophylaxis in immunocompromised patients is a serious concern. The optimal therapy for immunosuppressed patients with oseltamivir-resistant 2009 H1N1 influenza virus is unknown and few options exist. We report a 10-yr-old recipient of kidney transplant who was hospitalized with oseltamivir-resistant 2009 H1N1 influenza pneumonia complicated by severe respiratory failure, ARDS, and renal failure requiring institution of ECMO and CRRT. On presentation, treatment with oseltamivir (second course) and broad-spectrum antibiotics was initiated. Immunosuppressive agents were stopped on hospital day (d) 2. On hospital d 7, given his critical status, immunocompromised state, and difficulty in obtaining intravenous zanamivir, after obtaining ethical approval and parental consent, he was treated with intravenous peramivir (through an Emergency Investigational New Drug Application) for two wk. He tolerated the regimen well and his clinical status improved gradually. Several factors may have contributed to virus clearance and survival including recovery of the immune system, aggressive critical care support, and administration of peramivir. Ongoing surveillance is essential to monitor how oseltamivir-resistant H275Y mutant viruses may evolve in the future.

H1N1pdm influenza infection in hospitalized cancer patients: clinical evolution and viral analysis.

BACKGROUND: The novel influenza A pandemic virus (H1N1pdm) caused considerable morbidity and mortality worldwide in 2009. The aim of the present study was to evaluate the clinical course, duration of viral shedding, H1N1pdm evolution and emergence of antiviral resistance in hospitalized cancer patients with severe H1N1pdm infections during the winter of 2009 in Brazil. METHODS: We performed a prospective single-center cohort study in a cancer center in Rio de Janeiro, Brazil. Hospitalized patients with cancer and a confirmed diagnosis of influenza A H1N1pdm were evaluated. The main outcome measures in this study were in-hospital mortality, duration of viral shedding, viral persistence and both functional and molecular analyses of H1N1pdm susceptibility to oseltamivir. RESULTS: A total of 44 hospitalized patients with suspected influenza-like illness were screened. A total of 24 had diagnosed H1N1pdm infections. The overall hospital mortality in our cohort was 21%. Thirteen (54%) patients required intensive care. The median age of the studied cohort was 14.5 years (3-69 years). Eighteen (75%) patients had received chemotherapy in the previous month, and 14 were neutropenic at the onset of influenza. A total of 10 patients were evaluated for their duration of viral shedding, and 5 (50%) displayed prolonged viral shedding (median 23, range=11-63 days); however, this was not associated with the emergence of a resistant H1N1pdm virus. Viral evolution was observed in sequentially collected samples. CONCLUSIONS: Prolonged influenza A H1N1pdm shedding was observed in cancer patients. However, oseltamivir resistance was not detected. Taken together, our data suggest that severely ill cancer patients may constitute a pandemic virus reservoir with major implications for viral propagation.