Zika virus purification
Described herein are processes for purifying infectious Zika virus particles and uses of protamine in such processes.
1. A process for purifying infectious Zika virus particles, wherein said process comprises the steps of:
(i) providing a crude harvest (a) comprising infectious Zika virus particles, non-infectious Zika virus particles, and impurities, wherein the impurities are generated from growing Zika virus particles on a cell substrate;
(ii) contacting said crude harvest (a) with an agent comprising protamine to obtain a Zika virus preparation (b) comprising infectious Zika particles, wherein said agent facilitates separation of infectious Zika particles from non-infectious Zika virus particles; and
(iii) further purifying said Zika virus preparation (b) by one or more size exclusion methods, wherein said one or more size exclusion methods comprise
(A) sucrose density gradient centrifugation; and/or
(B) a solid-phase matrix packed in a column comprising a ligand-activated core and an inactive shell comprising pores, wherein the pores comprise a molecular weight cut-off that excludes the Zika virus particles from entering the ligand-activated core, and wherein a molecule smaller than the molecular weight cut-off of the pores can enter the ligand-activated core, thereby collecting the Zika virus particles, and/or
(C) size exclusion chromatography;
to obtain a final Zika virus preparation (c) comprising infectious Zika virus particles, less than 100 ng/mL residual host cell DNA, less than 1 μg/mL residual host cell protein, and less than 1 μg/mL residual aggregates of Zika virus particles.
2. The process according to claim 1 , wherein said agent also facilitates the separation of infectious Zika virus particles from host cell proteins and/or low molecular weight materials.
3. The process according to claim 1 , wherein the final Zika virus preparation (c) comprises less than 10 ng/mL residual host cell DNA, less than 100 ng/mL residual host cell protein, and less than 100 ng/mL residual aggregates of Zika virus particles.
4. The process according to claim 1 , wherein said crude harvest (a) is subjected to one or more pre-purification step(s) prior to step (ii), wherein said one or more pre-purification step(s) comprise
i) filtration using a filter having a pore size equal to or less than 1 μm; and/or
ii) digestion of host cell genomic DNA by enzymatic treatment; and/or
iii) ultra/diafiltration using a hollow fiber membrane having a pore size equal to or greater than 100 kDa.
5. The process according to claim 1 , wherein said agent comprises protamine sulphate.
6. The process according to claim 1 , wherein the infectious Zika virus particles in said final Zika virus preparation (c) are enriched by at least 50% to 95% relative to total Zika virus particles in said crude harvest (a).
7. The process according to claim 4 , wherein said one or more pre-purification step(s) is performed using a filter having a pore size equal to or less than 0.2 μm.
8. The process according to claim 1 , wherein said final Zika virus preparation (c) comprises less than 10% residual impurities relative to impurities in said crude harvest (a).
9. The process according to claim 1 , wherein said Zika virus is propagated in a cell line selected from the group consisting of an EB66 cell line, a Vero cell line, a Vero-αHis cell line, a HeLa cell line, a HeLa-S3 cell line, a 293 cell line, a PC12 cell line, a CHO cell line, a 3T3 cell line, a PerC6 cell line, an MDSK cell line, a chicken embryonic fibroblast cell line, a duck cell line, and a diploid avian cell line.
10. The process according to claim 9 , wherein said cell line is a Vero cell line.
11. The process according to claim 1 , wherein said Zika virus is a live virus, an attenuated live virus, a chimeric virus, a modified live virus, or a recombinant live virus.
12. The process according to claim 1 , wherein said Zika virus is a Zika virus strain of the Asian lineage or an immunogenic variant thereof.
13. The process according to claim 1 , wherein said process resulting in final Zika virus preparation (c) is followed by an inactivation step, wherein the Zika virus is inactivated by formaldehyde.
14. A composition comprising infectious Zika virus particles obtainable or obtained by the process according to claim 1 , wherein said composition contains residual protamine levels that are below the detection limit using size exclusion chromatography.
15. The composition according to claim 14 , wherein said composition contains trace amounts of protamine or fragments thereof that are detectable by mass spectroscopy or other sensitive methods.
16. The composition according to claim 14 for treating and/or protecting from a Zika virus infection.
17. The process according to claim 1 for manufacturing a composition for immunization against a Zika virus infection.
18. The process according to claim 1 , wherein said agent comprises protamine salt.
19. The process according to claim 1 , wherein the infectious Zika virus particles in said final Zika virus preparation (c) are enriched by at least 50% to 95% relative to total Zika virus particles in said crude harvest.
20. The process of claim 5 , wherein the protamine sulphate is between 0.5 to 3 mg/ml.