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°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.