Circulation of components during microfluidization and/or homogenization of emulsions
An improved method for the manufacture of an oil-in-water emulsion involves circulation of emulsion components between a first container and a second container via a homogenizer and/or via a microfluidization device. Usefully, all of the emulsion components from the first container are emptied before being returned.
1. A method for the manufacture of an emulsion, the method comprising the step of: (i) formation of a first emulsion having a first average oil droplet size by circulation, comprising (a) at least one type I circulation of transferring the first emulsion components between a first container and a homogenizer and (b) at least one type II circulation of transferring the first emulsion components from a first container to a second container through a homogenizer, and then returning them from the second container to the first container through the same homogenizer.
2. The method according to claim 1 , wherein all of the emulsion components from the first container are passed through the homogenizer into the second container, and then substantially all of the emulsion components from the second container are passed through the homogenizer back into the first container.
3. The method according to claim 1 , further comprising: (ii) microfluidization of the first emulsion to form a second emulsion having a second average oil droplet size which is less than the first average oil droplet size.
4. The method according to claim 1 , wherein the circulation comprises (a) the at least one type I circulation followed by (b) the at least one type II circulation.
5. The method of claim 1 , wherein the homogenizer is a mechanical homogenizer.
6. The method of claim 3 , wherein the homogenizer provides a shear rate of up to 1×10 6 s −1 , and wherein the microfluidization occurs an interaction chamber that provides a shear rate >2.5×10 6 s −1 .
7. The method according to claim 3 , further comprising: (iii) filtration of the second emulsion.
8. The method according to claim 1 , wherein step (i) comprises two or more cycles of transferring the first emulsion's components from the first container to the second container and back again.
9. The method according to claim 1 , wherein during step (ii), the second emulsion is formed by circulating the second emulsion components through a microfluidization device a plurality of times.
10. The method according to claim 9 , wherein the circulation of the second emulsion components comprises transferring the second emulsion components between a first emulsion container and a microfluidization device.
11. The method according to claim 9 , wherein the circulation of the second emulsion components comprises transferring the second emulsion components from a first emulsion container, through a first microfluidization device to a second emulsion container, and then through a second microfluidization device, wherein the first and second microfluidization devices are the same.
12. The method according to claim 11 , wherein after passing through the second microfluidization device, the second emulsion components are returned to the first emulsion container and the circulation from the first container to the second container is repeated one or more times.
13. The method according to claim 1 , wherein the first average oil droplet size is 5000 nm or less.
14. The method according to claim 1 , wherein the number of oil droplets having a size of >1.2 μm in the first emulsion is 5×10 11 /ml or less.
15. The method according to claim 3 , wherein the second average oil droplet size is 500 nm or less.
16. The method according to claim 3 , wherein the number of oil droplets having a size of >1.2 μm in the second emulsion is 5×10 10 /ml or less.
17. A method for preparing a vaccine composition, comprising preparing an emulsion according to claim 1 and combining the emulsion with an antigen.
18. A method for preparing a vaccine kit comprising preparing an emulsion according to claim 1 and packaging the emulsion into a kit as a kit component together with an antigen component.
19. The method according to claim 18 , wherein the kit components are in separate vials.
20. The method according to claim 19 , wherein the vials are made from borosilicate glass.
21. The method according to claim 18 , wherein the emulsion is a bulk adjuvant and the method comprises extracting unit doses from the bulk adjuvant for packaging as kit components.
22. The method according to claim 17 , wherein the antigen is an influenza virus antigen.
23. The method according to claim 22 , wherein the combination of the emulsion and the antigen forms a vaccine composition and wherein the vaccine composition includes about 15 μg, about 10 μg, about 7.5 μg, about 5 μg, about 3.8 μg, about 1.9 μg, about 1.5 μg of hemagglutinin per influenza virus strain.
24. The method according to claim 22 , wherein the combination of the emulsion and the antigen forms a vaccine composition and wherein the vaccine composition includes a thiomersal or 2-phenoxyethanol preservative.