Neuraminidase and Hemagglutinin Matching Patterns of a Highly Pathogenic Avian and Two Pandemic H1N1 Influenza A Viruses

Abstract

BackgroundInfluenza A virus displays strong reassortment characteristics, which enable it to achieve adaptation in human infection. Surveying the reassortment and virulence of novel viruses is important in the prevention and control of an influenza pandemic. Meanwhile, studying the mechanism of reassortment may accelerate the development of anti-influenza strategies.Methodology/Principal FindingsThe hemagglutinin (HA) and neuraminidase (NA) matching patterns of two pandemic H1N1 viruses (the 1918 and current 2009 strains) and a highly pathogenic avian influenza A virus (H5N1) were studied using a pseudotyped particle (pp) system. Our data showed that four of the six chimeric HA/NA combinations could produce infectious pps, and that some of the chimeric pps had greater infectivity than did their ancestors, raising the possibility of reassortment among these viruses. The NA of H5N1 (A/Anhui/1/2005) could hardly reassort with the HAs of the two H1N1 viruses. Many biological characteristics of HA and NA, including infectivity, hemagglutinating ability, and NA activity, are dependent on their matching pattern.Conclusions/SignificanceOur data suggest the existence of an interaction between HA and NA, and the HA NA matching pattern is critical for valid viral reassortment.

High genetic compatibility and increased pathogenicity of reassortants derived from avian H9N2 and pandemic H1N1/2009 influenza viruses

“…The coexistence of pandemic H1N1/2009 influenza virus and some avian influenza viruses (such as avian H5N1 and H9N2 viruses) in humans and pigs provides an opportunity for the incorporation of avian virus genes into mammalian-adapted viruses that results in the emergence of novel viruses with considerable potential threat to public health. Several studies focused on the reassortment between highly pathogenic avian H5N1 and pandemic H1N1 viruses (29,30). However, all previous influenza pandemic strains evolved from viruses with low pathogenicity (16).…”

Differential Activation of NK Cells by Influenza A Pseudotype H5N1 and 1918 and 2009 Pandemic H1N1 Viruses

“…Preparation of influenza virus pps and coculture with NK cells. Influenza virus pps were generated as described previously (31,58,59). Briefly, influenza virus pps were produced using a retrovirus-based pseudotype system via the expression of influenza virus HA, NA, Gag-Pol, and the green fluorescent protein (GFP) reporter gene in a 293T cell expression system.…”

Special features of the 2009 pandemic swine-origin influenza A H1N1 hemagglutinin and neuraminidase

“…Although immunity is also an important factor, this may explain why certain HA-NA serotype combinations are more common than others and some are never observed. Recent data suggests that combination of 09N1 with 18H1 results in a higher infectivity, however the 09H1 with 18N1 (1918 pandemic N1) does not ( Figure 4) [46]. Because 09H1 and 18H1 are highly similar, it is difficult to say the advantage of 18H1 in this system.…”