Phenotypic characteristics of novel swine-origin influenza A/California/07/2009 (H1N1) virus

Background The 2009 novel A(H1N1) virus appears to be of swine origin. This strain causing the current outbreaks is a new virus that has not been seen previously either in humans or animals. We have previously reported that viruses causing pandemics or large outbreaks were able to grow at a temperature above the normal physiological range (temperature resistance, non-ts phenotype), were found to be inhibitor resistant and restricted in replication at suboptimal temperature (sensitivity to grow at low temperature, non-ca phenotype). In this study, we performed phenotypic analysis of novel A(H1N1) virus to evaluate its pandemic potential and its suitability for use in developing a live attenuated influenza vaccine. Objectives The goal of this study is to identify phenotypic properties of novel A(H1N1) influenza virus. Methods A/California/07/2009 (H1N1) swine-origin influenza virus was studied in comparison with some influenza A viruses isolated in different years with respect to their ability to grow at non-permissive temperatures. We also analyzed its sensitivity to gamma-inhibitors of animal sera and its ability to agglutinate chicken, human and guinea pig erythrocytes. Results Swine-origin A/California/07/2009 (H1N1) virus was found to be non-ts and inhibitor resistant and was not able to grow at 25 degrees C (non-ca). We did not find any difference in the ability of the hemagglutinin of A/California/07/2009 (H1N1) virus to bind to erythrocytes of different origin. Conclusion The novel swine-origin A(H1N1) virus displays a phenotype typical of the past pandemic and epidemic viruses. This finding suggests that this virus might be a good wild type parental prototype for live vaccine for potential use for controlling pandemic influenza.