H1N1 novel human influenza virus takes better control of host's immune system

Syed Akbar
Hyderabad:  A team of Indian virologists has cracked the mystery behind the high transmissibility of novel human influenza virus H1N1 finding out that the virus takes over better control of the host's immune system than the seasonable influenza viruses.
Though H1N1 or swine flu virus has subsided after causing havoc during 2009 and 2010, it continues to be a threat in India and other developing countries. Still newer cases of H1N1 are reported from different parts of the country causing concern to health planners.
The team, comprising Dr AK Chakrabarti, Dr S Mukherjee and others, from the National Institute of Virology noted that the high transmissibility of pandemic H1N1 virus is because of its "better subversion of host immune responses compared to the seasonal influenza virus". Moreover, lack of earlier immunity to novel human influenza virus makes it more pathogenic when compared with seasonal H1N1 or common cold.
Since the novel H1N1 virus contains the genes of avian, human, and swine viruses it exhibited a high mortality rate. "We studied the host gene expression response to Indian isolate of pandemic H1N1 infection and compared it with seasonal H1N1 infection. We found that pandemic H1N1 induces immune response earlier than seasonal H1N1 viruses, but at the later stages of infection there is a suppression of host immune responses," the scientists pointed out.
The study by the NIV team showed that the novel influenza virus caused considerable decrease in the expression of cytokine and other immune genes as compared to seasonal H1N1. They noted that the inability to induce strong innate immune response could be a reason for the high transmissibility, pathogenicity and mortality caused by pandemic H1N1 virus.