Primarily oseltamivir-resistant influenza A (H1N1pdm09) virus evolving into a multidrug-resistant virus carrying H275Y and I223R neuraminidase substitutions

Lessons from resistance analysis in clinical trials of IV zanamivir

Influenza infection causes substantial morbidity and mortality during seasonal epidemics and pandemics. Antivirals, including neuraminidase inhibitors, play an important role in the treatment of severely ill patients infected with influenza. Resistance is a key factor that can affect the efficacy of neuraminidase inhibitors (NAIs). It is a recommendation by regulatory authorities to monitor for resistance during the development of anti-influenza medications. An additional requirement by regulators is to examine amino acid sequences for minority species harbouring resistance substitutions. In a Phase III study of intravenous (IV) zanamivir respiratory samples were analysed for the presence of resistant quasi species using Next Generation Sequencing (NGS). In this study ten resistance substitutions, two of which were treatment emergent, were detected by NGS that otherwise would not have been detectable by Sanger sequencing. None of the substitutions were present at any other timepoints analysed. The effect these mutations have on clinical response is difficult to characterize; in fact, all patients from which these variants were isolated had a successful clinical outcome and the effect on clinical response was therefore likely minimal. Although NGS is becoming a routine method for nucleic acid sequencing and will detect substitutions previously undetected by Sanger sequencing, the value of this technique in identifying minority species with resistance substitutions that are clinically meaningful remains to be demonstrated, particularly with acute infections such as influenza.

Detection of neuraminidase inhibitor-resistant influenza A (H1N1)pdm09 viruses obtained from influenza surveillance in Indonesia

Background:

Influenza antiviral resistance has been shown to occur in many countries and is commonly found in influenza A(H1N1)pdm09 and A(H3N2). In this study, we monitored and investigated the neuraminidase inhibitor resistance of influenza A(H1N1)pdm09 viruses through the influenza surveillance system in Indonesia.

Methods:

A total of 4752 clinical specimens were collected from patients with influenza-like illness and severe acute respiratory infection during the year 2016. An allelic discrimination assay was conducted by a single base substitution or a single-nucleotide polymorphism that is specific to the H275 wild-type and Y275 mutant. Sequencing was performed to confirm the H275Y mutations, and we analysed the phylogenetic relationship.

Results:

The first occurrence of oseltamivir-resistant influenza A(H1N1)pdm09 was observed in the samples from the influenza-like illness surveillance. Two H275Y oseltamivir-resistant viruses (0.74%) out of 272 influenza A(H1N1)pdm09 positives were found. Both of them were collected from untreated patients.

Conclusion:

The number of oseltamivir-resistant influenza A(H1N1)pdm09 viruses in Indonesia is very low. However, it is necessary to continue with active surveillance for oseltamivir resistance in severe and mild cases.

A Review of Clinical Influenza A and B Infections With Reduced Susceptibility to Both Oseltamivir and Zanamivir

Anti-influenza drugs play major roles in the management of severe influenza infections. Neuraminidase inhibitors (NAIs), which are active against all influenza A subtypes and the 2 major influenza B lineages, constitute the only class of antivirals recommended for the control of influenza epidemics and eventual pandemics. Thus, the emergence of NAI resistance could be a major clinical concern. Although most currently circulating influenza A and B strains are susceptible to NAIs, clinical cases of influenza viruses harboring single or multiple NA substitutions or deletions conferring a cross-resistance phenotype to the 2 main NAIs (oseltamivir and zanamivir) have been reported, mostly in immunocompromised individuals. Moreover, such events seem to be more frequent in A(H1N1)pdm09 viruses containing the H274Y substitution together with other NA changes (I222R, E119D/G). This review summarizes the therapeutic regimens leading to the emergence of NAI cross-resistant influenza A and B viruses as well as the virologic properties of such variants.

The therapeutic effects of sodium cromoglycate against influenza A virus H5N1 in mice

Objectives

To identify the protective role of sodium cromoglycate in mice during influenza virus infection.

Design

H5N1 virus‐infected mice were treated with the mast cell stabilizer sodium cromoglycate (SCG) to investigate its therapeutic effect.

Sample

The nose, trachea and lungs from mice were collected.

Main outcome measures

Virus replication and host responses were determined by plaque assay, quantitative PCR, immunohistochemistry, and histology.

Results

SCG‐treated mice survived better than did PBS‐treated mice after H5N1 virus infection. Mild pathological changes with fewer inflammatory cell infiltration and fewer virus antigens were observed in the nose, trachea, and lungs of SCG‐treated mice on days 3 and 5 post‐infection. However, no significant changes in viral load in the lungs were detected between SCG‐ and PBS‐treated mice. Furthermore, significantly decreased expression of interleukin‐6, tumor necrosis factor‐a, Toll‐like receptor 3, and TIR‐domain‐containing adapter‐inducing interferon‐b was detected in the lungs of SCG‐treated mice, and no higher expression of interferon‐c was detected.

Conclusion

These results suggest that SCG has therapeutic roles in H5N1 virus‐infected mice by alleviating the inflammatory response rather than inhibition of viral replication in the lungs.