Disclosed herein are methods and composition producing a viral vaccine with reduced particle size, particularly for use in the production of influenza virus vaccines.

Disclosed is an adapted Madin-Darby canine kidney cell line capable of suspension culture in the absence of serum, and a chemically-defined medium for culture of the adapted MDCK cell line. Further disclosed are culture methods for growing the adapted MDCK cell line and methods for producing a vaccine from the adapted MDCK cell line grown in the chemically-defined medium.

The invention provides various reverse genetics systems for producing segmented RNA viruses, wherein the systems do not require bacteria for propagation of all of their expression constructs.

Disclosed herein are nanoparticles suitable for use in vaccines. The nanoparticles present antigens from pathogens surrounded to and associated with a detergent core resulting in enhanced stability and good immunogenicity. Dosages, formulations, and methods for preparing the vaccines and nanoparticles are also disclosed.

The present invention provides a method for purification of a virus or virus antigen comprising providing a virus preparation and centrifugation of said virus preparation in a gradient of a sugar established by the addition of two or more buffered sugar layers of different concentration. The method leads to higher yields and reduces unwanted aggregation of the virus or virus antigen by increasing the volume of the peak pool.

The invention provides a composition useful to prepare high titer influenza B viruses, e.g., in the absence of helper virus, which includes internal genes from an influenza B virus vaccine strain or isolate, e.g., one that is safe in humans, for instance, one that does not result in significant disease, that confer enhanced growth in cells in culture, such as MDCK cells, or in eggs.

This invention discloses a method of increasing production of virus-like particles comprising expressing an avian influenza matrix protein. The invention also comprises methods of making and using said VLPs.

The invention provides a composition useful to prepare high titer influenza B viruses, e.g., in the absence of helper virus, which includes internal genes from an influenza B virus vaccine strain or isolate, e.g., one that is safe in humans, for instance, one that does not result in significant disease, that confer enhanced growth in cells in culture, such as MDCK cells, or in eggs.

The invention provides a composition useful to prepare high titer influenza B viruses, e.g., in the absence of helper virus, which includes internal genes from an influenza B virus vaccine strain or isolate, e.g., one that is safe in humans, for instance, one that does not result in significant disease, that confer enhanced growth in cells in culture, such as MDCK cells, or in eggs.

Disclosed herein are nanoparticles suitable for use in vaccines. The nanoparticles present antigens from pathogens surrounded to and associated with a detergent core resulting in enhanced stability and good immunogenicity. Dosages, formulations, and methods for preparing the vaccines and nanoparticles are also disclosed.