Process for obtaining lipid envelope virus sub-units, notably antigens for use as vaccines, the products obtained and their applications

A process for the production of immunogenic heavy subunits of influenza virus, comprising the following steps, carried out at a neutral or basic pH:

• (1) dissolving an amount of chloroform in an aqueous influenza virus suspension to obtain a concentration of chloroform equivalent to or approximating its solubility limit in said suspension, thereafter,
• (2) adding, with stirring, to the preparation so obtained a nonionic detergent while maintaining a single phase system, said detergent being added at the minimal concentration necessary to effect disruption of the virus into heavy immunogenic subunits, and stirring this mixture for a sufficient length of time to obtain said disruption, said heavy subunits comprising neuraminidase and hemagglutinin antigens in their original arrangement attached to fragments of the lipid envelopes of said virus, and
• (3) separating the heavy subunits so obtained from lighter components by applying gradient fractionation methods to the reaction mixture, said lighter components comprising said chloroform, said detergent and other products originating from the disruption of said virus, and said heavy subunits being in the dense fraction of the gradient, wherein an inactivation agent is added to the reaction medium at any time during the process.