Dear Houda and Manpreet - thanks for your interesting discussion on virus inactivation for mouse studies, and for your interest in our 2000 ICB article on oral influenza vaccination.
Using different doses of gamma-irradition (13 - 30 kGy) to inactivate A/Qld influenza was fascinating in terms of the subsequent post-challenge antibody response (presumably related to partial of full virus inactivation prior to oral vaccination). We described this also in an earlier Vaccine publication (Lidbury B.A., et al. (1997). Erythrocytes enhance the immunogenicity of oral vaccination with gamma irradiated influenza virus: increasing the dose of irradiation results in a significant diminution of lung IgA response. Vaccine 15:1529-1537), which provides additional insights on the vaccine preparation.
Try Beta propiolactone to 1/4000 . If you are working with small amounts , increase the inactivating dose. It is useful in such cases to dilute the GLP in sterile distilled water. Allow the mixture gently stirred for 2 hours at laboratory temperature and then overnight at 4 ° C . Intraperitoneally immunization of mice with recall 7 days after can give you satisfactory, I hope.
We have been using a hydrogen peroxide based platform. See Ammanna, Raue & Slifka Nat Med 2012, Walker, Raue & Slifka JV 2012, Pinto et al. JV 2013. Beta propiolactone & Formaldehyde are the traditional methods, but we have found that these while efficacious have 'problems'. The most significant one being the 'trailing' in the kinetics of inactivation when using formaldehyde necessitating long inactivation times and/or elevated temperatures, and the (potential) epitope damage when using either chemical.