Characterization of 2 Influenza A(H3N2) Clinical Isolates with Reduced Susceptibility to Neuraminidase Inhibitors Due to Mutations in the Hemagglutinin Gene

For most severe viral pandemics such as influenza and AIDS, the exact contribution of individual viral genes to pathogenicity is still largely unknown. A necessary step toward that understanding is a systematic comparison of different influenza virus strains at the level of transcriptional regulation in the host as a whole and interpretation of these complex genetic changes in the context of multifactorial clinical outcomes and pathology. We conducted a study by infecting pigtailed macaques (Macaca nemestrina) with a genetically reconstructed strain of human influenza H1N1 A/Texas/36/91 virus and hypothesized not only that these animals would respond to the virus similarly to humans, but that gene expression patterns in the lungs and tracheobronchial lymph nodes would fit into a coherent and complete picture of the host-virus interactions during infection Much progress has been made in the understanding of the structure and molecular functions of influenza virus (19,35,46,54) and in the sequencing of the virus genome, most notably that of the 1918 pandemic strain (7,57,58,72). New formulations for vaccines are being developed (55, 79), and new prophylactic and therapeutic drugs have provided the human population with a degree of protection and shown promise in mice, even against viruses recombined with the hemagglutinin and neuraminidase genes from the 1918 pandemic flu (69, 73). However, the genetic instability of influenza virus requires a new vaccine every year, and resistance to some of the drugs that prevent uncoating of the virus inside cells (M2 blockers) has already developed (24). Two great enigmas of pandemic influenza, particularly of the 1918 strain, are, apart from their much greater virulence, the reversal in patterns of age-specific mortality and the relatively larger proportion of deaths due to overwhelming primary viral pneumonia rather than secondary bacterial pneumonias (51, 71). The key to these features distinguishing pandemic from ordinary strains lies in the intricacies of host-virus interactions in addition to differences in existing immunity (45).The present study was aimed at establishing a model system in nonhuman primates for the study of host-virus interactions at the genetic level and through the use of cDNA microarrays. A thorough understanding of a successful response to infection with "ordinary" influenza virus, in this case A/Texas/36/91, a strain used to infect humans in experimental settings (30,33), is essential to elucidate how responses to more virulent strains differ and ultimately influence the outcome of infection. In the analysis of the cDNA array data, attention was given to general gene regulation patterns but with a particular focus on genes related to the innate immune response, which is believed to be a key factor in the clinical course and pathology of the disease, particularly during infection with more virulent strains (77). Other functions studied at the transcriptional level included immune cell chemotaxis and tissue transmigration, antigen presentation, T-and...

Section: Discussionmentioning

confidence: 99%

Integration of Clinical Data, Pathology, and cDNA Microarrays in Influenza Virus-Infected Pigtailed Macaques (Macaca nemestrina)

Baskin¹,

Garcı́a-Sastre

Tumpey

et al. 2004

“…We and others have observed changes in the receptor binding properties of the HA protein of H3N2 viruses during the 38 years that they have been circulating in humans (2,21,34). These changes, including a loss of the ability to agglutinate chicken red blood cells (RBC), suggest a recent reduction in the affinity of binding of the HA protein to its receptor, SA.…”

mentioning

confidence: 99%

Alterations in Receptor Binding Properties of Recent Human Influenza H3N2 Viruses Are Associated with Reduced Natural Killer Cell Lysis of Infected Cells

Owen

Yamada

Thompson

et al. 2007

“…The additional glycosylation can also decrease receptor binding activity, presumably due to occlusion of the receptor binding site pocket (1,27). Evolution of influenza A viruses in humans has brought about changes in receptor binding specificity and affinity; specifically, it has been observed that recent H1N1 and H3N2 clinical isolates no longer agglutinate chicken red blood cells (2,22,24,26,37). The fine receptor binding specificity of human influenza viruses is beginning to be understood, and indeed, a new preference of modern H3N2 isolates for binding Neu5Ac␣2,6Gal␤1-4GlcNAc (6ЈSLN) over Neu5Ac␣2,6Gal␤1-4Glc (6ЈSL) was recently described (23).…”

mentioning

confidence: 99%

Infection of Human Airway Epithelium by Human and Avian Strains of Influenza A Virus

Thompson

Barclay

Zambon³

et al. 2006

226

235

We describe the characterization of influenza A virus infection of an established in vitro model of human pseudostratified mucociliary airway epithelium (HAE). Sialic acid receptors for both human and avian viruses, ␣-2,6-and ␣-2,3-linked sialic acids, respectively, were detected on the HAE cell surface, and their distribution accurately reflected that in human tracheobronchial tissue. Nonciliated cells present a higher proportion of ␣-2,6-linked sialic acid, while ciliated cells possess both sialic acid linkages. Although we found that human influenza viruses infected both ciliated and nonciliated cell types in the first round of infection, recent human H3N2 viruses infected a higher proportion of nonciliated cells in HAE than a 1968 pandemic-era human virus, which infected proportionally more ciliated cells. In contrast, avian influenza viruses exclusively infected ciliated cells. Although a broad-range neuraminidase abolished infection of HAE by human parainfluenza virus type 3, this treatment did not significantly affect infection by influenza viruses. All human viruses replicated efficiently in HAE, leading to accumulation of nascent virus released from the apical surface between 6 and 24 h postinfection with a low multiplicity of infection. Avian influenza A viruses also infected HAE, but spread was limited compared to that of human viruses. The nonciliated cell tropism of recent human H3N2 viruses reflects a preference for the sialic acid linkages displayed on these cell types and suggests a drift in the receptor binding phenotype of the H3 hemagglutinin protein as it evolves in humans away from its avian virus precursor.