What type of solvent do you use? Do you add antigen or pH stabilizers to your solvent (trehalose, sodium azide, HCO3, Mg or Ca ions)?

I have not the answer for your particular case. Formalin inactivation relies on partial denaturation of viral components, and denaturation has consequences on the antigenic properties. In general, effect of formalin on antigenic properties of a virus depend on the virus and its composition, the exact protocol you use (formalin concentration, fresh or not, buffer, temperature, duration of exposition, correct removal of formalin from the final preparation, ...) but also what "antigenic property" you are interested in and the method you use to look for it. Only experimentation can drive to the appropriate inactivation protocol. In order to make the result reproducible, you need fine tuning and recording of the experimental conditions.

Denaturation of antigens during storage at 4°C is also possible, of course ! You must control this step too.

Mr Maciej Przybylski and Mr Huges Tolou, first I would thank you for your reply. I have not added any stabilizers. I had standardized the inactivation time and it takes 12 hours at 4 degrees for 0.3% formalin to inactivate the virus. After this step I have used some volume for my immunization studies and remaining virus (inactivated) was stored in 4 degrees without any treatment, now I would like to use the same for further studies and I wonder weather the inactivated virus has same property or not.

I think that ues for inactivation Formalin must be use neutral (by conc formalin added in NaOH tablet stock solutin of upper solution use ).Forlmalinnadded 0.1% interval at least 5days ,very slow shaking not drustic ,not use stirer and finaly 0.3% .this method is too old chiken virus(New casstle Vaccine shake by hand 3 ~5 times 10L bottle in one time in a day). Virus antigen very quickly lose by added concformalin.

Mr Bartolomeo Gorgoglion, thank you for your answer. Actually, I have confirmed the 100% inactivation by the method you mentioned. My question is, I have this inactivated virus stored at 4 degrees for a month now, and I want to use it for immunization studies and I wonder any changes has taken place..??

Are you checked the Avirulance test? Generally 4 degree C was more suitable temperature for inatcivated viral componants. The level of Antigenicity lose during 4degree C storage only very trace, if it is without any contamination.

The storage of the majority of liquid vaccine inactivated is made in 4 degree for long time without decrease of activity if stabilizers used.

I think that you can use this stock of vaccine ( one month in 4 degree) and make immunisation. You can compare with the first work, if you repet this experiment ( first vaccine and second one month later ) you can fixe some parameter of you product.

Good continuation