Phylogenetic analysis of pandemic 2009 influenza A virus circulating in the South American region: genetic relationships and vaccine strain match

Spatiotemporal dynamics of influenza A(H1N1)pdm09 in Brazil during the pandemic and post-pandemic periods

Influenza A(H1N1)pdm09 was responsible for the first global flu pandemic in 21st century affecting all the world. In Brazil, A(H1N1)pdm09 is still circulating as a seasonal virus, causing deaths every year. Nevertheless, the viral diffusion process that yearly seeds new influenza strains in the country was not investigated yet. The aim of the current study was to describe the phylodynamics and phylogeography of influenza A(H1N1)pdm09 in Brazil between 2009 and 2014. Neuraminidase sequences from Brazil and other regions of the World were retrieved and analyzed. Bayesian phylogeographic and phylodynamic model approaches were used to reconstruct the spatiotemporal and demographic history of influenza A(H1N1)pdm09 in Brazil (divided in subtropical and tropical regions) and related countries. Our analyses reveal that new influenza A(H1N1)pdm09 lineages are seeded in Brazil in almost each year and the main sources of viral diversity are North America, Europe and East Asia. The phylogeographic asymmetric model also revealed that Brazil, mainly the subtropical region, seeds viral lineages into other countries. Coalescent analysis of the compiled dataset reconstructed the peak of viral transmissions in the winter months of Southern hemisphere. The results presented in this study can be informative to public health, guide intervention strategies and in the understanding of flu virus migration, which helps to predict antigenic drift and consequently the developing of new vaccines.

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.

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

The 2009 pandemic influenza A(H1N1)pdm09 virus emerged and caused considerable morbidity and mortality in the third world, especially in Brazil. Although circulating strains of A(H1N1)pdm09 are A/California/04/2009-like (CA-04-like) viruses, various studies have suggested that some mutations in the viral hemagglutinin (HA) may be associated with enhanced severity and fatality. This phenomenon is particularly challenging for immunocompromised individuals, such as those who have undergone bone marrow transplant (BMT), because they are more likely to display worse clinical outcomes to influenza infection than non-immunocompromised individuals. We studied the clinical and viral aspects of post-BMT patients with confirmed A(H1N1)pdm09 diagnosis in the largest cancer hospital in Brazil. We found a viral strain with K-15E, P83S and Q293H polymorphisms in the HA, which is presumably more virulent, in these individuals. Despite that, these patients showed only mild symptoms of infection. Our findings complement the discovery of mild cases of infection with the A(H1N1)pdm09 virus with the K-15E, P83S and Q293H mutations in Brazil and oppose other studies that have linked these changes with increased disease severity. These results could be important for a better comprehension of the impact of the pandemic influenza in the context of BMT.

Genomic analysis of pandemic and post-pandemic influenza A pH1N1 viruses isolated in Rio Grande do Sul, Brazil

During the 2009 influenza A pH1N1 pandemics in Brazil, the state that was most affected was Rio Grande do Sul (RS), with over 3,000 confirmed cases, including 298 deaths. While no cases were confirmed in 2010, 103 infections with 14 deaths by pH1N1 were reported in 2011. Genomic analysis of the circulating viruses is fundamental for understanding viral evolution and supporting vaccine development against these pathogens. This study investigated whole genomes of six pH1N1 virus isolates from pandemic and post-pandemic periods in RS, Brazil. Phylogenetic analysis using the concatenated genome segments demonstrated that at least two lineages of the virus co-circulated in RS during the 2009 pandemic period. Moreover, our analysis showed that the post-pandemic pH1N1 virus from 2011 constitutes a distinct clade whose ancestor belongs to clade 7. All six isolates contained amino acid substitutions in their proteins when compared to the archetype strains California/04/2009 and California/07/2009. The 2011 isolates contained more amino acid substitutions, and most of their genes were under purifying selection. Based on the amino acid substitutions in HA epitopes from strains isolated in RS, Brazil, in silico analysis predicted a decrease in vaccine efficacy against post-pandemic strains (median 31.562 %) in relation to pandemic ones (median 39.735 %).

Bayesian coalescent analysis of pandemic H1N1 influenza A virus circulating in the South American region

The first influenza pandemic of this century was declared in April of 2009, with the emergence of a novel H1N1 influenza A virus strain (H1N1pdm). Understanding the evolution of H1N1pdm populations within the South American region is essential for studying global diversification, emergence, resistance and vaccine efficacy. In order to gain insight into these matters, we have performed a Bayesian coalescent Markov Chain Monte Carlo analysis of hemagglutinin (HA) and neuraminidase (NA) gene sequences of all available and comparable HA and NA sequences obtained from H1N1pdm IAV circulating in the South American region. High evolutionary rates and fast population growths characterize the population dynamics of H1N1pdm strains in this region of the world. A significant contribution of first codon position to the mean evolutionary rate was found for both genes studied, revealing a high contribution of non-synonymous substitutions to the mean substitution rate. In the 178days period covered by these studies, substitutions in all HA epitope regions can be observed. HA substitutions D239G/N and Q310H have been observed only in Brazilian patients. While substitution D239G/N is not particularly associated to a specific genetic lineage, all strains bearing substitution Q310H were assigned to clade 6, suggesting a founder effect. None of the substitutions found in the NA proteins of H1N1pdm strains isolated in South America appears sufficiently close to affect the drug binding pocket for the three NA inhibitor antivirals tested. A more detailed analysis of NA proteins revealed epitope differences among 2010 vaccine and H1N1pdm IAV strains circulating in the South American region.

Pandemic and seasonal influenza viruses among patients with acute respiratory illness in Kashmir (India)

Please cite this paper as: Koul PA., et al. (2011) Pandemic and seasonal influenza viruses among patients with acute respiratory illness in Kashmir (India). Influenza and Other Respiratory Viruses 5(6), e521–e527.

Background  With the emergence of pandemic influenza A (2009A/H1N1) virus in India, we sought to determine the prevalence and clinical presentations of seasonal and pandemic influenza viruses among acute respiratory illness (ARI) patients from Srinagar, a temperate climate area in northern India, during the peak winter season.

Methods  Combined throat and nasal swabs, obtained from 194 (108 male) presenting with ARI from January to March 2010 (Week 53‐week 10), were tested by RT‐PCR for influenza A and B, including 2009A/H1N1 viruses. HA1 gene of selected 2009A/H1N1‐positive samples was sequenced, and phylogenetic analysis was carried out.

Results  Twenty‐one (10·8%, age 15–80 years, median age 40 years) patients tested positive for influenza viruses: 13 (62%) for 2009A/H1N1 virus, 6 (28·5%) for seasonal influenza A (H3N2), and 2 (9·5%) for influenza B. Twelve of the 13 patients with 2009A/H1N1 presented with febrile ARI, and eight had associated comorbidities. All of the patients recovered. Phylogenetic analysis of HA gene (n = 8) revealed that all strains from Srinagar clustered in 2009A/H1N1 clade seven along with the other 2009A/H1N1 strains from India. Amino acid substitutions in the HA protein defining clade seven (P83S, S203T, and I321V) were found in almost all isolates from Srinagar.

Conclusions  Both seasonal and 2009A/H1N1 viruses appear to be associated with ARI in Srinagar. The 2009A/H1N1 in Srinagar is genetically similar to globally circulating clade 7 strains, with unique signature sequences in the HA gene. Further investigations into ascertain the role of these mutations in possible alteration of the virulence and transmissibility of the virus are needed.