Detection of the influenza A(H1N1)pdm09 virus carrying the K-15E, P83S and Q293H mutations in patients who have undergone bone marrow transplant

Semi-quantitative Influenza A population averages from a multiplex respiratory viral panel (RVP): potential for reflecting target sequence changes affecting the assay

Background

Yearly influenza virus mutations potentially affect the performance of molecular assays, if nucleic acid changes involve the sequences in the assay. Because individual patient viral loads depend on variables such as duration of illness, specimen type, age, and immunosuppression, we examined seasonal population averages of positive tests to smooth inherent variability.

Methods

We studied the population seasonal averages of the semi-quantitative nAMPs for the influenza matrix and hemagglutinin genes in the GenMark (Carlsbad, CA) Respiratory Viral Panel assay between 3 institutions over 3 Influenza seasons.

Results

Population average nAMPs were strikingly consistent between separate institutions, but differed substantially between H3N2 and H1N1 seasons. In the 2012–2013 and 2014–2015 influenza seasons, matrix gene H3N2 nAMP averages were 50–70% less than those of the same assay in the 2013–2014 H1N1 season. Influenza strains representative of these seasons were grown in tissue culture and when the supernatant virus was adjusted to the same copy number using a TaqMan assay, the same relative differences were reproduced in the RVP assay. Because the sequences for the PCR and PCR product detection in the GenMark assay are proprietary, the manufacturer provided single stranded DNA matching the capture probe for the representative H3N2 (3 mismatches) and H1N1 strains (2 different mismatches). Equimolar concentrations of these synthetic DNA sequences gave average nAMP values that closely correlated with the average nAMPS of the representative strains and their respective seasonal averages.

Conclusions

Seasonal averages of semi-quantitative data may provide a means to follow assay performance as a reflection of the effects of molecular drift.

Phylogenetic analyses of influenza A (H1N1)pdm09 hemagglutinin gene during and after the pandemic event in Brazil

Pandemic influenza A H1N1 [A(H1N1)pdm09] was first detected in Brazil in May 2009, and spread extensively throughout the country causing a peak of infection during June to August 2009. Since then, it has continued to circulate with a seasonal pattern, causing high rates of morbidity and mortality. Over this period, the virus has continually evolved with the accumulation of new mutations. In this study we analyze the phylogenetic relationship in a collection of 220 A(H1N1)pdm09 hemagglutinin (HA) gene sequences collected during and after the pandemic period (2009 to 2014) in Brazil. In addition, we have looked for evidence of viral polymorphisms associated with severe disease and compared the range of viral variants with the vaccine strain (A/California/7/2009) used throughout this period. The phylogenetic analyses in this study revealed the circulation of at least eight genetic groups in Brazil. Two (G6-pdm and G7-pdm) co-circulated during the pandemic period, showing an early pattern of viral diversification with a low genetic distance from vaccine strain. Other phylogenetic groups, G5, G6 (including 6B, 6C and 6D subgroups), and G7 were found in the subsequent epidemic seasons from 2011 to 2014. These viruses exhibited more amino acid differences from the vaccine strain with several substitutions at the antigenic sites. This is associated with a theoretical decrease in the vaccine efficacy. Furthermore, we observed that the presence of any polymorphism at residue 222 of the HA gene was significantly associated with severe/fatal cases, reinforcing previous reports that described this residue as a potential virulence marker. This study provides new information about the circulation of some viral variants in Brazil, follows up potential genetic markers associated with virulence and allows infer if the efficacy of the current vaccine against more recent A(H1N1)pdm09 strains may be reduced.