Abstract
BackgroundThe world has recently overcome the first influenza pandemic of the 21st century caused by a novel H1N1 virus (pH1N1) which is a triple reassortant comprising genes derived from avian, human, and swine influenza viruses and antigenically quite different from seasonal H1N1 strains. Although the case fatality rates have decreased in many developed countries, the situation is still alarming in many developing countries including India where considerable numbers of new cases are appearing everyday. There is still a high morbidity and mortality of susceptible adult as well as young population without having underlying health issues due to the influenza infection.ResultsTo achieve a better understanding of the risk posed by the pH1N1 and to understand its pathogenicity, we studied the host gene expression response to Indian isolate of pH1N1 infection and compared it with seasonal H1N1 infection. The response was studied at four different time points (4, 8, 16 and 24 h) post infection (hpi) in A549 cells using microarray platform. We found that pH1N1 induces immune response earlier than seasonal H1N1 viruses, but at the later stages of infection there is a suppression of host immune responses. The infection with pH1N1 resulted in considerable decrease in the expression of cytokine and other immune genes namely IL8, STAT1, B2 M and IL4 compared to seasonal H1N1.ConclusionWe propose that the inability to induce strong innate immune response could be a reason for the high transmissibility, pathogenicity and mortality caused by pH1N1 virus.
Highlights
The world has recently overcome the first influenza pandemic of the 21st century caused by a novel H1N1 virus which is a triple reassortant comprising genes derived from avian, human, and swine influenza viruses and antigenically quite different from seasonal H1N1 strains
Virus infection A549 cells were infected with pH1N1 and seasonal influenza viruses at a multiplicity of infection (MOI) of 3 as described earlier [15]
Host gene expression profile in response to pandemic (H1N1) 2009 virus infection The gene expression profile to pH1N1 infection was studied at 4 different time points post infection in order to understand the host responses at different stages of virus infection
Summary
The world has recently overcome the first influenza pandemic of the 21st century caused by a novel H1N1 virus (pH1N1) which is a triple reassortant comprising genes derived from avian, human, and swine influenza viruses and antigenically quite different from seasonal H1N1 strains. In Asia, the most active areas of pandemic influenza virus transmission currently are in parts of India, Bangladesh, Bhutan, Myanmar Nepal, and Thailand. There are reports of 2720 deaths from pandemic H1N1 influenza virus infection in India which is approximately 14% of the total world mortality http:// mohfw-h1n1.nic.in/august.html; http://netindian.in/ news/2010/11/15/0008699/6-h1n1-deaths-india-duringpast-week-govt. The pandemic H1N1 virus is antigenically distinct from seasonal influenza viruses and the majority of human population lacks immunity against this virus [3,4,5]. Animal studies have shown that this virus has a higher replicative power than the seasonal influenza virus [6,7]. The pH1N1 isolates tested in mice and ferrets, were found to be replicating more efficiently than currently circulating human H1N1 viruses [6,7,8]
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