Disertantes

Andrea Pontoriero

Resumen

Neuraminidase inhibitor susceptibility of influenza viruses circulating in Argentina 2011-2015

Background

Influenza is a major human pathogen associated with high morbidity and mortality. NA inhibitors (NAIs) oseltamivir and zanamivir have been the cornerstone of anti-influenza therapy in recent years. In the 10 years since licensure of NAIs drugs, their use has steadily increased, especially during the pandemic of 2009. Therefore, enhanced surveillance capacity to detect the emergence of NAI-resistant strains of A(H1N1)pdm09 should be developed. Since 2006 in Argentina, it has been possible to perform the detection of the H275Y and E119V substitutions in influenza A(H1N1)pdm09 and A(H3N2) viruses by genotypic methods from the original samples.

Methods

Two rapid genotypic screenings to identify the single nucleotide polymorphism (SNP) encoding H275Y and E119V in influenza A(H1N1)pdm09 and A(H3N2)respectively. These techniques allow differentiation between wild-type and oseltamivir-resistant viruses in clinical specimens. Influenza A(H1N1)pdm09 clinical specimens carrying the H275Y substitutions detected by SNP screening were inoculated in MDCK cells. Besides, Sanger sequences obtained from the original samples and/or isolates carrying the H275Y/E119V substitutions were analyzed using Bio Edit program comparing with other resistant strains worldwide.

Results

Between 2011 and 2015 the National Laboratory Network collected a total of 337,322 samples for respiratory virus diagnosis coming from all the country. Of these, 16,832 (5%) were tested positive for influenza virus. During this period, the NIC received a total of 8,960 (7,539 influenza A and 1,421 influenza B) influenza positive clinical specimens. From the total influenza A samples received at the NIC, 4,225 (56%) were subtyped as A(H3N2) and 2,469 (33%) as A(H1N1)pdm09. The H275Y substitution was found in 25 out of 2,216 influenza A(H1N1)pdm09 samples tested (2 collected in 2011, 1 in 2012, 17 in 2013, 1 in 2014 and 4 in 2015) and E119V change was found in 1 out of 1,515 A(H3N2) samples studied (1 in 2014). Most of the viruses carrying the H275Y/E119V substitutions were collected from patients at risk without oseltamivir therapy.The phylogenetic tree of the H275Y A(H1N1)pdm09 viruses showed that the these strains possessed the changes V241I, N369K, but not the N386K, similar to US strains isolated in 2013-2014 influenza season. The change E119V observed in one strain was confirmed by Sanger sequencing.

Conclusions

The reduced detection of resistant variants to NAI in community specimens indicates that the emergence of NAI-resistant viruses remains low in Argentina, as observed in the rest of the world. This study aims to contribute to better decisions in national health policies and help in medical treatment.