2013 Jun 11
McKimm-Breschkin JL, Barrett S, Pudjiatmoko, Azhar M, Wong FY, Selleck P, Mohr PG, McGrane J, Kim M.
Commonwealth Scientific and Industrial Research Organisation, Materials
Science and Engineering, Parkville, Victoria, Australia ; Commonwealth
Scientific and Industrial Research Organisation, Australian Animal
Health Laboratory, Geelong, Victoria, Australia.
We have tested the susceptibility to neuraminidase inhibitors of 155
clade 2.1 H5N1 viruses from Indonesia, isolated between 2006-2008 as
well as 12 clade 1 isolates from Thailand and Cambodia from 2004-2007
using a fluorometric MUNANA-based enzyme inhibition assay. The Thailand
and Cambodian clade 1 isolates tested here were all susceptible to
oseltamivir and zanamivir, and sequence comparison indicated that
reduced oseltamivir susceptibility we observed previously with clade 1
Cambodian isolates correlated with an S246G neuraminidase mutation.
Eight Indonesian viruses (5%), all bearing I222 neuraminidase mutations,
were identified as mild to extreme outliers for oseltamivir based on
statistical analysis by box plots. IC50s were from 50 to 500-fold higher
than the reference clade 1 virus from Viet Nam, ranging from 43-75 nM
for I222T/V mutants and from 268-349 nM for I222M mutants. All eight
viruses were from different geographic locales; all I222M variants were
from central Sumatra. None of the H5N1 isolates tested demonstrated
reduced susceptibility to zanamivir (IC50s all <5 nM). All I222
mutants showed loss of slow binding specifically for oseltamivir in an
IC50 kinetics assay. We identified four other Indonesian isolates with
higher IC50s which also demonstrated loss of slow binding, including one
virus with an I117V mutation. There was a minimal effect on the binding
of zanamivir and peramivir for all isolates tested. As H5N1 remains a
potential pandemic threat, the incidence of mutations conferring reduced
oseltamivir susceptibility is concerning and emphasizes the need for
greater surveillance of drug susceptibility.
[PubMed - in process]
Free full text http://www.ncbi.nlm.nih.gov/pubmed/23776615