RESUMO
BACKGROUND: influenza viruses (IFVs) frequently achieve resistance to antiviral drugs, necessitating the development of compounds with novel mechanisms of action. DAS181 (Fludase), a sialidase fusion protein, may have a reduced potential for generating drug resistance due to its novel host-targeting mechanism of action. METHODS: IFV strains B/Maryland/1/59 and A/Victoria/3/75 (H3N2) were subjected to >30 passages under increasing selective pressure with DAS181. The DAS181-selected IFV isolates were characterized in vitro and in mice. RESULTS: despite extensive passaging, DAS181-selected viruses exhibited a very low level of resistance to DAS181, which ranged between 3- and 18-fold increase in EC(50). DAS181-selected viruses displayed an attenuated phenotype in vitro, as exhibited by slower growth, smaller plaque size and increased particle to pfu ratios relative to wild-type virus. Further, the DAS181 resistance phenotype was unstable and was substantially reversed over time upon DAS181 withdrawal. In mice, the DAS181-selected viruses exhibited no greater virulence than their wild-type counterparts. Genotypic and phenotypic analysis of DAS181-selected viruses revealed mutations in the haemagglutinin (HA) and neuraminidase (NA) molecules and also changes in HA and NA function. CONCLUSIONS: results indicate that resistance to DAS181 is minimal and unstable. The DAS181-selected IFV isolates exhibit reduced fitness in vitro, likely due to altered HA and NA functions.
Assuntos
Antivirais/farmacologia , Farmacorresistência Viral , Vírus da Influenza A/efeitos dos fármacos , Vírus da Influenza B/efeitos dos fármacos , Mutação , Proteínas Recombinantes de Fusão/farmacologia , Seleção Genética , Animais , Feminino , Genótipo , Humanos , Vírus da Influenza A/genética , Vírus da Influenza A/crescimento & desenvolvimento , Vírus da Influenza A/patogenicidade , Vírus da Influenza B/genética , Vírus da Influenza B/crescimento & desenvolvimento , Vírus da Influenza B/patogenicidade , Camundongos , Camundongos Endogâmicos BALB C , Infecções por Orthomyxoviridae/patologia , Infecções por Orthomyxoviridae/virologia , Fenótipo , Inoculações Seriadas , Ensaio de Placa Viral , Virulência , Replicação ViralRESUMO
BACKGROUND: DAS181 (Fludase) is a sialidase fusion protein in clinical development as a broad-spectrum anti-influenza virus (IFV) therapeutic agent. Previous reports by other investigators have raised the concern that desialylation of airway epithelium might increase susceptibility to Streptococcus pneumoniae infection. METHODS: To address whether DAS181 would lead to an increased risk of pneumococcal infection, we tested S. pneumoniae colonization after DAS181 treatment of human A549 cells, healthy mice, and mice challenged with a lethal dose of IFV A/PR/8/34 (H1N1) or A/Victoria/3/75 (H3N2), followed by 10(4) cfu of S. pneumoniae (D39) on day 3 or day 7. DAS181 treatment was given 24-48 h after IFV challenge. RESULTS: DAS181 treatment did not increase S. pneumoniae colonization in vitro or in vivo in healthy animals. In IFV-infected mice, DAS181 prevented pneumonia and significantly prolonged survival and inhibited the IFV titer by > or = 3 logs. None of the treated animals showed enhanced S. pneumoniae colonization of the lung. In addition, opportunistic infections with Citrobacter species or Klebsiella species occurred only in mice receiving vehicle, not in animals treated with DAS181. CONCLUSIONS: These data indicate that DAS181 treatment does not exacerbate secondary bacterial infection in mice. DAS181 may reduce the risk of secondary bacterial infection by inhibiting IFV.