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|Title:||Sequence analysis of resistance markers in pandemic influenza A (H1N1) 2009 viruses isolated in Portugal|
|Publisher:||Instituto Nacional de Saúde Doutor Ricardo Jorge, IP|
|Abstract:||Backround: In April 2009, a new influenza A (H1N1) virus (AH1N1pdm) was detected circulating in humans. Its rapid widespread transmission led to the declaration by the WHO of an influenza pandemic. This virus had origin in a reassortment between a North American swine lineage (already a triple reassortant, circulating in pigs since the late 1990’s) and a Eurasian swine lineage (which contributed to the AH1N1pdm with the neuraminidase (NA) and matrix (MP) gene segments). The NA inhibition assay is the base test to determine the susceptibility to NA inhibitors (NAI), however it requires virus isolation, and the consequent detection of a resistant viral strain requires confirmation by sequencing of the NA gene segment present in the original biological product. Material and Methods: In Portugal, during the 2009 influenza pandemic, about 16500 clinical samples were tested by the National Influenza Reference Laboratory for the presence of influenza AH1N1pdm virus. From near 8000 AH1N1pdm-positive samples, 153 were isolated in MDCK cells and of these 53 isolates were taken for sequence analysis of the NA and MP gene segments. The NA inhibition assays were performed by the WHO collaborating centre (London). Results: As all AH1N1pdm viruses, sequenced Portuguese isolates carried the S31N change in the M2 protein, which confers resistance to the adamantanes. The most common mutation in N1 neuraminidase associated with resistance to oseltamivir is the H275Y change. From our 53 sequenced isolates, only one carried this mutation. This was from an 8-years-old child with chronic diseases such as a DiGeorge syndrome diagnosed in 2004 and Evans Syndrome with auto-immune haemolytic anaemia diagnosed in 2006. Initially, this child was treated with an underdosing of oseltamivir, however, as the influenza-like syndrome persisted with a suspicion of viral pneumonia, led to the antiviral treatment dose review. The NA inhibition assay confirmed that this virus was resistant to oseltamivir. The NA inhibition assays performed in our viral isolates and accordingly to our sequence data, revealed that the majority of Portuguese AH1N1pdm viruses were sensitive to NAI. All neuraminidases presented the N248D substitution, except for A/Lisboa/35/2009, a viral strain from an early clade (at least, previous to clade 4) as it lacks also V106I amino acid change. Other amino acid substitutions, such as E119V, I223V, Q136K, known to reduce the susceptibility to NAI, were not found in our isolates. Conclusions: The use of conventional sequence analysis for monitoring the molecular markers of antiviral resistance in influenza A virus provides a valuable tool for an early detection of antiviral resistant strains.|
|Appears in Collections:||DDI - Posters/abstracts em congressos internacionais|
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