GB2498112A

GB2498112A - Preparation of a diphtheria toxoid by incubating toxin concentrate with an amino acid and formaldehyde

Info

Publication number: GB2498112A
Application number: GB1302086.2A
Authority: GB
Inventors: Friedrich Blackkolb; Bernd Becker; Martha Reith; Manfred Isenberg; Anne Katrin Hilbert
Original assignee: Novartis AG
Current assignee: Novartis AG
Priority date: 2011-11-11
Filing date: 2011-11-11
Publication date: 2013-07-03
Also published as: GB201302086D0

Abstract

The present invention relates to a process for preparing a diphtheria toxoid comprising the steps of (i) growing a strain of Corynebacterium diphtheriae expressing a diphtheria toxin in a fermentation medium,(ii) separating the diphtheria toxin from the fermentation medium to obtain a diphtheria toxin solution, (iii) preparing a diphtheria toxin concentrate from the diphtheria toxin solution with a diphtheria toxin concentration of at least 2000 Lf/mL, (iv) adding to the concentrate an amino acid and formaldehyde, and (v) incubating the concentrate in the presence of the amino acid and formaldehyde to obtain the diphtheria toxoid. The Corynebacterium diphtheria is grown in a volume of at least 100 litres to provide a yeilkd of at least 140Lf/ml of toxin/ derivative. An alternative embodiment provides a process for producing a diphtheria toxoid comprising growing a strain of Corynebacterium diphtheriae in a medium free of animal-derived components, purifying, adding formaldehyde and incubating, and a further embodiment provides a composition suitable as a vaccine comprising a diphtheria toxoid free from formaldehyde-crosslinked animal-derived components, with a potency of at least 30 IU.

Description

FERMENTATION METHODS AND TIIEIR PRODUCTS

FIELD OF THE INVENTION

The invention relates to a fermentation medium for cultivating Corynebacteriurn diphtheriae. The invention also relates to the use of the fermentation medium in processes for obtaining diphtheria toxin from the (Jdiphtheriae bacteria being cultivated, to the preparation of vaccines using the diphtheria toxin obtained in the processes, and to the toxins themselves. The invention further relates to purification and detoxification processes for preparing diphtheria toxoids from the toxin e.g. for inclusion in a vaccine.

BACKGROUND

Corynebacleriuin c/iphtheriae causes diphtheria. The bacterium produces a toxic protein, diphtheria toxin, which can be treated (e.g. using formalin or formaldehyde) to remove toxicity while retaining the ability to induce protective anti-toxin antibodies after injection. This treatment is referred to as "detoxification" or "toxoiding", and the detoxified toxin is referred to as a "toxoid." The diphtheria toxoids are used in diphtheria vaccines and arc described in more detail in chapter 13 of the book "Vaccines" [1] and in chapter 31 of New Generation Vaccines [21.

Any therapeutic that is administered to humans and has been produced using a biological process has the potential for introducing harmful substances into the human body. Such harmful substances may be part of the medium used during the biological process. For example, animal-derived medium components such as fetal bovine serum bear the risk of containing aberrantly-folded proteins such as prions. Traditionally, diphtheria toxoid was obtained by growing C.diphtheriae in growth medium containing animal-derived components (e.g. in Fenton medium, or in Linggoud & Fenton medium), such as bovine extract and/or casamino acids derived from cow milk.

The use of proteinaceous material of non-animal origin removes this risk. EP-B-l849860 discloses a medium for cultivating C.diphtheriae comprising at least 20% by dry weight of a non-animal proteinaceous material which is a yeast extract [3]. W02005/056773 discloses a C,diphtheriae culture medium for the production of diphtheria toxin, which is substantially free of animal-derived components, and methods for producing the toxin [4]. W02006/042542 discloses a fermentation medium for producing bacterial toxins using a non-animal and non-soya derived protein source [51. W000/50449 discloses a method of purifying diphtheria toxin comprising fermenting a microorganism strain capable of producing diphtheria toxin using glucose as a carbon source. In a preferred embodiment this patent application discloses the use of a growth medium containing no more than 1% yeast extract [61.

Although these media are based on non-animal derived protein sources, and so can decrease contamination risks, none of them results in high yields of diphtheria toxin during industrial production (e.g. using fermenters in the 100-600 L range), and low yields are a drawback of these processes.

It is thus an object of the invention to provide thither and improved fermentation media suitable for use in industrial-scale, high-yield manufacturing of diphtheria toxin for vaccine production.

In traditional processes to prepare diphtheria toxoid, the toxin is treated with formaldehyde in the presence of culture medium components e.g. see Figure 4 of chapter 31 in reference 2. As well as cross-linking and detoxifying the diphtheria toxin, the formaldehyde causes covalent cross-linking of the medium components. This cross-linking means that the animal-derived components, if present in a growth medium, can he irreversibly locked into a human vaccine product. Higher purity toxoids for vaccine use can be obtained by puriliing the toxin before the formaldehyde treatment. Patent Application GB-969772 discloses a method for producing toxoids from diphtheria toxin, comprising treating the toxin in an aqueous medium with formaldehyde in the presence of an aliphatic diamine of molecular weight below 200 which contains a primary or secondary amino group [7]. Frech el al. [8] discloses a physiochemical analysis of two purified diphtheria toxoids: the first was prepared by a conventional process in which the diphtheria toxin was formalinised and then purified; the second was first highly purified and then detoxified. W02005/056773 discloses detoxification of an at least 75% pure diphtheria toxin. Even if high purity is achieved in a purification step preceding detoxification, however, residual animal-derived components of the fermentation medium used to prepare the diphtheria toxin are cross-linked by formaldehyde to the diphtheria toxoid obtained during the detoxification step.

It is a further objcct of the invention to provide a diphtheria toxoid that is free from formaldehyde-crosslinked animal-derived components. It is another object of thc invention to provide further improved processes in which diphtheria toxin is first highly purified and then detoxified.

SUMMARY OF THE INVENTION

A. Fermentation media The invention provides various media for culturing Corynebcwterium diphthcriae. These media allow diphtheria toxin production at an industrial scale in fermenters having production volumes of at least 300 litres, with yields being consistently in the range of 200 Lf/mL to 250 Lf/mL (or higher). The media and processes disclosed herein can even exceed the yields achieved with animal-derived media in producing diphtheria toxin.

In general, the invention provides a fermentation medium suitable for culturing a strain of Corynebacterium diphthericie to produce diphtheria toxin or a derivative thereof, wherein the medium is free from animal-derived components and comprises a nitrogen source, a carbon source, an iron supplement, phosphorus, and growth factors. The medium is particularly useful for high yield, industrial-scale production of diphtheria toxin for preparing vaccines for human use.

In one aspect, the invention provides a fermentation medium stutable for culturing a strain of Corynchacteriurn diphtheriae to produce diphtheria toxin or a derivative thereof, wherein the medium is free of animal-derived components and comprises water, deferrated yeast extract and at least 0.08 M of a disaccharide as a carbon source. In one embodiment, the fermentation medium comprises between 0.08 M and 0.16 M of the disaccharide. In a specific embodiment, the fermentation medium comprises 0.15 M of the dissacharide.

In another aspect, the invention provides a fermentation medium suitable for culturing a strain of Corynebacterium diphtheriae to produce diphtheria toxin or a derivative thereof, wherein the medium is free of animal-derived components and comprises water, deferrated yeast extract, and a salt of Fe(III).

In a further aspect, the invention provides a fermentation medium suitable for culturing a strain of Corynebacterium diphtheriae to produce diphtheria toxin or a derivative thereof; wherein the medium is free of animal-derived components and comprises water and a low-mannan yeast extract. In one embodiment, the low-mannan yeast extract is deferrated.

In yet a further aspect, the invention provides a fermentation medium suitable for culturing a strain of Corynehacterluin diphtheriae to produce diphtheria toxin or a derivative thereof, wherein the medium is free of animal-derived components and comprises water, yeast extract that is free of components with a molecular weight greater than 30 kDa, and a salt of Fe(1l) or Fe(III) at a concentration between 1.5 jiM and3o,.tM.

B. Processes for preparing afrrnzentation medium The invention further provides a process for preparing a fermentation medium of the invention, comprising adding to water (i) a nitrogen source, (ii) a carbon source, and (iii) an iron supplement.

In one aspect, the invention provides a process for preparing a fermentation medium comprises dissolving yeast extract in water to yield a yeast extract solution, deferrating the yeast extract solution to obtain a deferrated yeast extract solution, and adding at least 0.08 M of a disaccharide to the deferrated yeast extract solution to prepare the fermentation medium. In one embodiment, between 0.08 M and 0.16 M of the disaccharide is added to the deferrated yeast extract solution. In a specific embodiment, 0.15 M of the disaccharide is added to the deferrated yeast extract solution.

In another aspect, the invention provides a process for preparing a fermentation medium that comprises dissolving yeast extract in water to make a yeast extract solution; deferrating the yeast extract solution to obtain a deferrated yeast extract solution, and adding a salt of Fe(III) to the deferrated yeast extract solution to prepare the fermentation medium. In one embodiment, the salt of Fe(III) is added to the deferrated yeast extract solution in combination with phosphate and a calcium salt to promote formation of a slow-release formulation of iron.

In a further aspect, the invention provides a process for preparing a fermentation medium, wherein the process comprises preparing a low-mannan yeast extract, and dissolving the low-mannan yeast extract in water to prepare the fermentation medium. In one embodiment, the process further comprises deferrating the low-mannan yeast extract.

In yet a further aspect, the invention provides a process for preparing a fermentation medium, wherein the process comprises dissolving yeast extract in water to make a yeast extract solution, ultrafiltrating the yeast extract solution using a membrane with a molecular weight cut-off greater than 30 kDa, deferrating the yeast extract solution to obtain a deferrated yeast extract solution, and adding a salt of Fe(lI) or Fe(III) to the deferrated yeast extract solution to a final concentration between 1.5 jiM and 30 jiM to prepare the fermentation medium.

C Processes for producing a diphtheria toxin or a derivative thereof The invention further provides a process for growing Corynebacterluin diphtheriae comprising cuhuring a strain of Corynehacteriwn diphtheriae in a fermentation medium of the invention.

In one aspect, the invention provides a process for preparing a diphtheria toxin or a derivative thereof comprising growing a strain of Corynebacteviwn diphtheriae expressing a diphtheria toxin or a derivative thereof in the fermentation medium of the invention and separating the diphtheria toxin or the derivative from the fermentation medium.

In another aspect, the invention provides a process for producing a diphtheria toxin or a derivative thereof comprising preparing a culture of a strain of Corynebacteriurn diphtheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentation medium free of animal-derived components, growing the culture to a concentration of at least 140 Lf/mL of the diphtheria toxin or the derivative in the fermentation medium, and separating the diphtheria toxin or the derivative from the fermentation medium.

11 Processes for producing a diphtheria toxoid The invention provides various processes for producing diphtheria toxoids. These processes ideally involve purification prior to detoxification. thereby minimising or avoiding cross-linking of medium components to the toxoid. Where yeast extracts have been used in the culture medium, the process should remove most (ideally all) residual yeast extract components from the diphtheria toxin prior to formaldehyde treatment, thereby avoiding the cross-linking of potentially-allergenic yeast components to the diphtheria toxoid. The high purity of the final diphtheria toxoid is also advantageous as the addition of preservatives can be avoided which further reduces the potential for adverse reactions during vaccination.

Moreover, if the purified material is concentrated prior to detoxification then it is possible to use smaller volumes during the formaldehyde treatment step. This initial concentration can be achieved, for instance, by several diafiltration steps that result in a more concentrated diphtheria toxin solution. The use of smaller volumes during the detoxification procedure is advantageous as it saves time as well as storage capacity.

Thus, in yet another aspect, the invention provides a process for preparing a diphtheria toxoid comprising growing a culture of a strain of Corynebacleriwn diphiheriac which expresses a diphtheria toxin in a fermentation medium of the invention, purifying the diphtheria toxin from the fermentation medium to obtain a purified diphtheria toxin, adding formaldehyde to the purified diphtheria toxin, and incubating ...4t-,,1,1:h,h,,..:.. fl..-.__ 41,. ,.-Lt-"2.4 III tUhIItLL W}fl ILIH_IIC4 IAJIII IUIII L1L VlUU3.3114) LU ULLflU1 U1 UI}fllLlIU.Ilfl LW1U1U.

In a further aspect, the invention provides a process for preparing a diphtheria toxoid comprising: (i) growing a strain of Corynebacterium diphtheriae expressing a diphtheria toxin or a derivative thereof in a fermentation medium, preferably at a volume of at least 100 litres and/or to provide a yield of at least l4OLf/ml of toxinlderivative; (ii) separating the diphtheria toxin or the derivative from the fermentation medium to obtain a diphtheria toxin solution; (iii) preparing a diphtheria toxin concentrate from the diphtheria toxin solution, wherein the concentration of the diphtheria toxin or the derivative in the concentrate is at least 20-fold higher than the concentration of the diphtheria toxin or the derivative either in the fermentation medium obtained at the end of step (i) or in the toxin solution obtained at the end of step (ii); (iv) adding to the concentrate an amide and formaldehyde, and incubating the concentrate from step (iv) to obtain the diphtheria toxoid. In one embodiment, the concentration of the diphtheria toxin or the derivative in the concentrate in step (iii) is between 20-fold and 36-fold higher than the concentration of the diphtheria toxin or the derivative in the fermentation medium.

In yet a further aspect, the invention provides a process for producing a diphtheria toxoid comprising (i) growing a strain of Corynebacteriwn diphtheriae expressing a diphtheria toxin or a derivative thereof in a fermentation medium comprising yeast extract as the only source of all essential amino acids, (ii) purifying the diphtheria toxin or derivative from the fermentation medium to obtain a purified diphtheria toxin or derivative, (iii) adding formaldehyde to the purified diphtheria toxin or derivative, and (iv) incubating the purified diphtheria toxin or derivative from step (iii) to obtain the diphtheria toxoid.

In yet another aspect, the invention provides a process for producing a diphtheria toxoid for the preparation of a vaccine for liunian use comprising (I) growing a strain of Corynebacterium diphtheriae expressing a diphtheria toxin or a derivative thereof in a fermentation medium that is free of animal-derived components, optionally wherein the fermentation medium comprises yeast extract, (ii) puri'ing the diphtheria toxin or derivative from the fermentation medium to obtain a purified diphtheria toxin or derivative having a purity of at least 1500 Lf/mg nitrogen, (iii) adding formaldehyde to the purified diphtheria toxin or derivative, and (iv) incubating the purified diphtheria toxin or derivative from step (iii) to obtain the diphtheria toxoid.

In another aspect, the invention provides a process for producing a diphtheria toxoid comprising (I) growing a strain of Corynebacteriurn diphtheriae expressing a diphtheria toxin or a derivative thereof in a fermenTation medium that is free of animal-derived components, optionally wherein the fermentation medium comprises yeast extract, (ii) purifying the diphtheria toxin or derivative from the fermentation medium to obtain a purified diphtheria toxin or derivative, wherein the purified toxin or derivative is at least 85% pure, (iii) adding formaldehyde to the purified diphtheria toxin or derivative, and (iv) incubating the purified diphtheria toxin or derivative from step (iii) to obtain the diphtheria toxoid.

In a further aspect, the invention provides a process for producing a diphtheria toxoid comprising (i) growing a strain of Corynebaceeriutn diphtheriae expressing a diphtheria toxin or a derivative thereof in a fermentation medium that is free of animal-derived components, optionally wherein the fermentation medium comprises yeast extract, (ii) puri1ing the diphtheria toxin or defivative from the fermentation medium using anion exchange chromatography to obtain a purified diphtheria toxin or derivative, (iii) adding formaldehyde to the purified diphtheria toxin or derivative, and (iv) incubating the purified diphtheria toxin or derivative from step (iii) to obtain the diphtheria toxoid.

In one particular aspect, the invention provides a process for producing a diphtheria toxoid comprising (i) preparing a solution of a diphtheria toxin or a derivative thereof at a concentration of at least 2000 Lf/mL, (H) adding to the solution (a) an amide at a final concentration of no more than 0.025 M and (b) formaldehyde at a final concentration in the range of 0.75-1%, and (iii) incubating the solution from step (ii) to obtain the diphtheria toxoid. In a specific embodiment, the toxin concentration of the solution prepared in step (i) is about 5000 LlYmL. Similarly, in a further particular aspect the invention provides a process for producing a diphtheria toxoid comprising (i) preparing a solution of a diphtheria toxin at a concentration of at least 2000 LtYmL, (H) adding to the solution (a) no more than 5 nmol of an amide per Lf of the diphtheria toxin and (b) between 40 and 55 nniol formaldehyde per Lf of the diphtheria toxin, and (iii) incubating the solution from step (H) to obtain the diphtheria toxoid. In a specific embodiment, the toxin concentration of the solution prepared in step (i) is about 5000 Lf/mL.

In a specific embodiment, the invention provides a process for preparing a diphtheria toxoid comprising (i) growing a culture of a strain of Corynebacteriu,n diphtheriae expressing a diphtheria toxin in a fermentation medium comprising yeast extract, (ii) puriing the diphtheria toxin from the fermentation medium to obtain a diphtheria toxin solution, (iii) adjusting the concentration of diphtheria toxin in the diphtheria toxin solution to at least 2000 Lf/mL to obtain a diphtheria toxin concentrate, (iv) adding to the concentrate (a) an amide to a final concentration of no more than 0.025 M and (b) formaldehyde to a final concentration in the range of 0.75-1%, and (v) incubating the concentrate from step (iv) to obtain the diphtheria toxoid. In a specific embodiment, the toxin concentration is adjusted to 5000 Lf/mL in step (iii).

In another specific embodiment, the invention provides a process for preparing a diphtheria toxoid suitable for vaccination comprising (1) growing a culture of a strain of Corynebacteriwn diphtheriae expressing a diphtheria toxin in a fermentation medium comprising yeast extract, (ii) purifying the diphtheria toxin from the fermentation medium to obtain a diphtheria toxin solution, (iii) adjust the concentration of diphtheria toxin in the diphtheria toxin solution to at least 2000 Lf/mL to obtain a diphtheria toxin concentrate, (iv) adding to the concentrate (a) no more than 5 nmol of an amide per Lf of the diphtheria toxin and (b) between 40 and 55 nniol formaldehyde per Lf of the diphtheria toxin, and (v) incubating the concentrate from step (iv) to obtain the diphtheria toxoid. In a specific embodiment, the toxin concentration is adjusted to 5000 LVmL in step (iii).

In one embodiment, the invention provides a process for preparing a combination vaccine for human use comprising: (1) preparing a culture of a strain of Corynebaceeriwn diphtheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentation medium free from animal-derived components, comprising a nitrogen source; at least 0.08 M of a carbon source; 1.5 IIM -30 iM soluble Fe2/Fe3; phosphorus; and growth factors; (ii) growing the culture in aerobic conditions to a concentration of at least 140 Lf/mL of the diphtheria toxin or the derivative in the fermentation medium; (iii) separating the diphtheria toxin or the derivative from the fermentation medium, wherein the separation step comprises a centrifugation step and a filtration step; (iv) purifying the diphtheria toxin or the derivative obtained in step (iii) using anion exchange chromatography to obtain a solution comprising a purified diphtheria toxin or derivative; (v) adjusting the concentration of the purified diphtheria toxin or derivative in the solution to at least 2000 Lf/mL to obtain a diphtheria toxin concentrate; (vi) adding to the concentrate (a) an amide to a final concentration of no more than 0.025 M and (b) formaldehyde to a final concentration in the range of 0.75-1%; and (vii) incubating the concentrate from step (vi) to obtain the diphtheria toxoid.

E. Diphtheria toxoids Processes of the invention provide diphtheria toxoids which are better suited for human vaccine use than those which are currently produced. The toxoids are analytically distinct from known toxoids e.g. by their cross-linking, by the absence of cross-linked medium components, by potency, and/or by purity. In preferred embodiments, the diphtheria toxoid obtained by the processes disclosed herein is free from formaldehyde-crosslinked animal-derived components.

In one aspect, the invention provides a diphtheria toxoid for use in human vaccination obtainable by growing a strain of Corynebacteriwn diphtlieriae that expresses a diphtheria toxin in a fermentation medium free of animal-derived components, separating the diphtheria toxin from the fermentation medium, and incubating the diphtheria toxin in the presence of formaldehyde to yield the diphtheria toxoid. In a specific embodiment, the diphtheria toxoid obtainable in this way is cross-linked by formaldehyde to at least one component of the fermentation medium.

The invention also provides a diphtheria toxoid prepared from diphtheria toxin produced by a S Corynebacteriuni diphtheriae bacterium that expresses a diphtheria toxin, wherein the bacterium was grown in a fermentation medium which is free from animal-derived components, and wherein the toxoid is crosslinked to at least one component of the fermentation medium.

In another aspect, the invention provides a diphtheria toxoid for use in human vaccination obtainable by a process comprising (i) growing a strain of Corynebacterium diphtheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentation medium that is free from animal-derived components, optionally wherein the fermentation medium comprises yeast extract, (ii) purifying the diphtheria toxin or derivative from the fermentation medium to obtain a purified diphtheria toxin or derivative, wherein the purified toxin or derivative is at least 85% pure and/or has a purity of at least 1500 Lfimg nitrogen, (iii) adding formaldehyde to the purified diphtheria toxin or derivative, and (iv) incubating the purified diphtheria toxin or derivative from step (iii) to obtain the diphtheria toxoid. In a specific embodiment, the diphtheria toxoid obtained by this process is cross-linked by formaldehyde to at least one component of the fermentation medium.

In a specific embodiment, the invention provides a diphtheria toxoid for use in human vaccination obtainable by a process comprising: (i) preparing a fermentation medium that is free of animal-derived components by dissolving a Iow-mannan yeast extract in water to yield a yeast extract solution, deferrating the yeast extract colution to oblain a defen-ated yeast extract solution, and adding 50 g/L of maltose, a growth factor solution and a salt of Fe(1II) at a concentration between 10-14 lAM to the deferrated yeast extract solution to prepare the fermentation medium, wherein the salt of FeUII) is added in combination with phosphate and a calcium salt to promote formation of a slow-release formulation of iron; (ii) centrifuging the fermentation medium to remove any iron precipitate that may have formed; (iii) ultrafiltering the fermentation medium using a membrane with a molecular weight cut-off greater than 30 kDa; (iv) preparing a culture of a strain of Corynebaciterium diphtheriae that expresses a diphtheria toxin in at least 100 L of the fermentation medium; (v) growing the culture to a concentration of at least 140 Lf/mL of the diphtheria toxin in the fermentation medium; (vi) separating the diphtheria toxin from the fermentation medium by centrifugation to yield a diphtheria toxin solution; (vii) filter-sterilizing the diphtheria toxin solution to yield a sterile diphtheria toxin; (viii) purif'ing the sterile diphtheria toxin to obtain a purified diphtheria toxin; (ix) adding formaldehyde to the purified diphtheria toxin; and (x) incubating the purified diphtheria toxin from step (ix) to obtain the diphtheria toxoid.

In another specific embodiment, the invention provides a diphtheria toxoid for use in human vaccination obtainable by a process comprising: (i) preparing a culture of a strain of Corynebucterium diphtheriae that expresses a diphtheria toxin in at Least 100 L of a fermentation medium that is free of animal-derived components and components with a molecular weight greater than 30 kfla, wherein the fermentation medium comprises (a) water, (b) a deferrated low-mannan yeast extract, (c) 50 gIL of maltose, (d) a growth factor solution comprising magnesium, copper, zinc, manganese, pimelic acid, nicotinic acid and j3-alanine, (e) amnionium ferric citrate at a starting concentration between 10-14 iM, and (f) phosphate; (ii) growing the culture under aerobic conditions to a concentration of at least 200 Lf/mL of the diphtheria toxin in the fermentation medium; (iii) separating the diphtheria toxin from the fermentation medium by centrifligation to yield a diphtheria toxin solution; (iv) filter-sterilizing the diphtheria toxin solution to yield a sterile diphtheria toxin; (v) purifying the sterile diphtheria toxin to obtain a purified diphtheria toxin; (vi) concentrating the purified diphtheria toxin at least 20-fold over the concentration of the diphtheria toxin in the fermentation medium to obtain a diphtheria toxin concentrate; (vii) adding formaldehyde and lysine to the diphtheria toxin concentrate; and (viii) incubating the diphtheria toxin concentrate in the presence of formaldehyde and lysine to obtain the diphtheria toxoid.

In a further specific embodiment, the invention piovides a diphtheria toxoid suitable for use in human vaccination obtainable by a process comprising: (i) growing a culture of a strain of Co;ynebacteriuin diplifheriae expressing a diphtheria toxin in a fermentation medium; (ii) purifying the diphtheria toxin from the fermentation medium using anion exchange chromatography to obtain a solution comprising a purified diphtheria toxin having at least 2000 Lf/mg nitrogen; (iii) adjusting the concentration of the purified diphtheria toxin in the solution to 5000 Lf/niL using diafiltration to obtain a diphtheria toxin concentrate; (iv) adding to the concentrate (a) lysine to a final concentration of 0.025 M and (b) formaldehyde to a final concentration of 1%; (v) incubating the concentrate from the preceding step to obtain a diphtheria toxoid concentrate; (vi) sterile-filtering the diphtheria toxoid concentrate to obtain a sterile solution; (vii) adjusting the concentration of the diphtheria toxoid in the sterile solution to 10000 Lf/mL using diafiltration to obtain a concentrated solution; and (viii) adjnstirig the pH of the concentrated solution to pH 7.5 to obtain a diphtheria toxoid suitable for use in human vaccination.

In another aspect, the invention provides a diphtheria toxoid obtainable by formaldehyde treatment of a diphtheria toxin having a concentration of at least 2000 Lf/mL. The formaldehyde treatment can involve (as disclosed elsewhere herein) adding to a solution of the toxin (a) an amide at a final concentration of no more than 0.025 M and (b) formaldehyde at a final concentration in the range of 0.75-1%. Similarly, the formaldehyde treatment can involve (as disclosed elsewhere herein) adding to a solution of the toxin (a) no more than 5 nmol of an amide per Lf of the diphtheria toxin and (b) between 40 and 55 nmol formaldehyde per Lf of the diphtheria toxin. These amounts of formaldehyde (and, optionally, amide e.g. lysine) are known in the art, but not for treatment of toxin at such a high concentration. The altered ratio provides a toxoid which is molecularly distinct from known toxoids.

The invention also provides a diphtheria toxoid obtainable by a process of the invention as described herein. In particular, the invention provides a diphtheria toxoid obtainable by a process as disclosed in the examples herein (eg obtainable by growing a Cidiphtheriac in the medium of Table 3, puri1ing toxin, and detoxit'ing the toxin, as disclosed herein).

F. C'wnpositions suitable for human vaccination The invention provides a composition suitable for human vaccination comprising a diphtheria toxoid which is free from formaldehyde-crosslinked animal-derived components and has a potency of at least 60 lU/mi. Similarly, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid purified from Corynebacteriwn diphtheriae grown in a culture medium free from animal-derived components and having a potency of at Least 60 lU/mi. In one embodiment, the composition has a monomer:dimer ratio of the diphtheria toxoid in the range of 3: I to 10:1, preferably in the range of3:1 to 6:1 (or 4:1 to 9:1), and the diphtheria toxoid can have an isoelectic point in the range of 4.0 to 5.0. In another embodiment, at least 70% of the toxoid is in monomeric form. In a further embodiment, the composition comprises a protective antigen from at least one pathogen other than Corynehacteriwn diphtheriae. For example, the protective antigen may be selected from hepatitis B virus surface antigen (1-IBsAg), tetanus antigen, pertussis antigen, Hinjluenzae type B capsular saccharidc, a N.ineningitic/is capsular saceharide, S.pneunwniae capsular saccharide, and IPV.

The invention also provides a composition siLitable for human vaccination, comprising a formaldehyde-linked diphtheria toxoid with an isoelectric point in the range of 4.0 to 5.0 and which is free from _Ii_,____I_ I _t___I I 1 r1 ---JurlIIaIuelIytIe-I111&eu UI IIIIIUI-ueIt veil euJIlpuIIellLs, wI]eIeIII Ut ICUSt / 070 01 LJJC t0Xt)IU IS III IlloflulIlerle form. The invention also provides a composition suitable for human vaccination, comprising a formaldehyde-linked diphtheria toxoid which is free from formaldehyde-linked animal-derived components, wherein at least 70% of the toxoid is in monomeric form. As discussed above, these compositions can include a protective antigen from at least one pathogen other than C.diphthcriae.

In one specific embodiment, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid free of fornialdehyde-crosslinkcd animal-derived components and at least one protective antigen from a pathogen other than Corynebacteriuni diphtheriae. In another specific embodiment, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid which is free from formaldehyde-crosslinked animal-derived components and which has a monomer:dimer ratio in the range of 3:1 to 8:1, more preferably in the range of 3:1 to 6:1, and wherein the diphtheria toxoid has an isoelectric point in the range of 5.0 to 4.0. In a further specific embodiment, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid which is free from forinaldehyde-crosslinked animal-derived components and wherein at least 70% of the diphtheria toxoid is in monomeric form.

In yet another embodiment, the invention provides a composition for use in preparing a human vaccine, comprising: (i) between 100-250 Lf/ml diphtheria toxoid which is free from formaldehyde-crosslinked animal-derived components; (ii) between 40-100 Lf/ml tetanus toxoid; wherein the ratio of diphtheria toxoid to tetanus toxoid in the coniposition is between 2:1 and 3:1.. In a particular embodiment, the composition does not comprise any other antigens except diphtheria toxoid and tetanus toxoid.

In a further embodiment, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid of the invention adsorbed to an insoluble aluminium salt adjuvant (e.g. aluminium hydroxide). For instance, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid which is free from formaldehyde-crosslinked animal-derived components and which is adsorbed to an insoluble aluminium salt adjuvant (e.g. aluminium hydroxide).

Similarly, the invention provides a composition suitable for human vaccination, comprising a diphtheria toxoid purified from Corynebaclerium diphtheriae grown in a culture medium free from animal-derived components and having a potency of at least 60 lU/mi, which is adsorbed to an insoluble aluminium salt adjuvant (e.g aluminium hydroxide).

Diphtheria toxoids of the invention can bc used as carrier proteins in saccharide conjugates. Thus, in a thither aspect, the invention provides a conjugate of a bacterial saccharide and a diphtheria toxoid carrier protein, wherein the diphtheria toxoid which is as variously defined above (e.g. which is free from formaldehyde-crosslinked animal-derived components).

In yet a further aspect, the invention provides vaccine formulations comprising the diphtheria toxoid of the invention and compositions comprising the same.

In a specific embodiment, the invention provides a combination vaccine comprising (i) a diphtheria toxoid which is free from fornialdehyde-crosslinked animal-derived components and has a potency of at least 60 lU/mI, and (ii) a protective antigen from at least one pathogen other than Corynebacierium dip/itheriae. The protective antigen may be selected from hepatitis B virus surface antigen (llBsAg), a H. influenzae type B capsular saccharide, and a N.meningitidis capsular saccharide. Preferably, the I IBsAg is free from animal-derived components. Preferably, the J-J.influenzae type B capsular saccharide is free from animal-derived components. Preferably, the N.ineningilidis capsular saccharide is free from animal-derived components.

The invention also provides a combination vaccine comprising (i) a diphtheria toxoid obtainable by formaldehyde treatment of a diphtheria toxin having a concentration of at least 2000 Lt7mL, as described above; and (ii) a protective antigen from at least one pathogen other than Corynebacteriwn diphtheriae, as described above.

In general, the invention also provides a human vaccine comprising a diphtheria toxoid of the invention, wherein (1) the toxoid is adsorbed to an insoluble aluminium salt adjuvant and/or (ii) the vaccine includes a protective antigen from at least one pathogen ether than C. diphtheriae.

G. Processes for preparing compositions suitable for human vaccination in a further aspect, the invention provides a process for preparing a composition suitable for human vaccination, comprising steps of combining: (i) a diphtheria toxoid which is free from formaldehyde-crosslinked arumal-derived components; (U) lIBsAg which is free from animal-derived components; (iii) Hinfluenzae type B capsular saccharide which is free from animal-derived components; and (iv) AT.meningitidis capsular saccharide which is free from animal-derived components.

In one embodiment, the invention provides a process for preparing a human vaccine, comprising mixing a composition that comprises (i) between 100-250 Lf/ml diphtheria toxoid which is free from formaldehyde-crosslinked animal-derived components, and (ii) between 40-100 Lf/m I tetanus toxoid, wherein the ratio of diphtheria toxoid to tetanus toxoid in the composition is between 2:1 and 3:!, with at least one further antigen-containing composition. In a specific embodiment, the process results in a human vaccine that comprises between 20-30 Lf/ml diphtheria toxoid and between 5-15 Lf!mI tetanus toxoid.

The invention also provides a process for preparing a composition suitable for human vaccination, comprising steps of combining: (i) a diphtheria toxoid purified from Corynebacwrium diphtheriae grown in a culture medium free from animal-derived components; (ii) HBsAg which is free from animal-derived components; (iii) Hinjluenzae type B capsular saccharide which is free from animal-derived components; and (iv) N.meningiticlis capsular saccharide which is free from animal-derived components. The composition can include diphtheria toxoid with a potency of at least 60 lU/mi.

DETAILED DESCIUPTION OF THE INVENTION

Fennentation media In one aspect, the invention relates to fermentation media that are suitable for culturing a strain of C.diphe/ieriae to produce diphtheria toxin or a derivative thereof, In order to support bacterial growth, the medium should include a nitrogen source, a carbon source, a phosphorus source, and growth factors. In order to support toxin production by the bacterium, the medium should contain a suitable source of iron.

In preferred embodiments the medium is free from animal-derived components. Thus all components in the medium should be prepared from non-animal sources. The components may, for instance, be prepared from plant sources (e.g. from soy), or may be synthetic, but meat and milk components are not used.

Nitrogen source The nitrogen source of the fermentation medium of the invention is preferably a yeast extract. Yeast extracts are generally obtained by salt-free autolysis of primary yeast and subsequent extensive purification, which renders the yeast extract free from undesired components such as spores and DNA.

In one embodiment, the yeast extract is low in mannans. Methods for preparing low-mannan yeast extracts are known in the art. For example, a low-mannan yeast extract may be prepared from a yeast strain that expresses reduced amounts of mannans. A yeast strain that expresses reduced amounts of mannans (e.g., less than 70% of wild-type levels) is partially deprived of its cell wall integrity, easily releases its intracellular content, and is therefore especially suitable to prepare yeast extracts with little variation from batch to batch. Ideally, a low-mannan yeast strain is able to grow in liquid medium to be suitable for yeast extract preparation on an industrial scale. Such a yeast strain may be a yeast strain in which one or more genes required for mannan expression have been mutated, Alternatively, a naturally occurring yeast strain that expresses low levels of mannans may be used to prepare yeast extract.

Examples for yeast strains with a cell wall having a low mannan content and methods for producing the same are disclosed in references 9 and 10. In particular, naturally occurring yeast strains or chemically or physically mutagenised yeast strains may be screened for low-mannan content in the cell wall using Gram-staining. Gram-positive strains that are also low in electron density of the outer layer of cell wall by electron microscopic inspection are likely to have a low mannan content. Mannan content may be determined by chemical analysis. Alternatively, the low mannan content of the cell wall of the yeast can he confirmed with mannan-specific antibodies or lectins such as concanavalin A. In another embodiment, the yeast extract is an ultrafiltered yeast extract e.g. the product of ultrafiltration of a crude yeast extract. For instance, a step of ultrafiltration can be included during preparation of the yeast extract, or an existing yeast extract can be subjected to ultrafiltration prior to its use in preparing a fermentation medium of the invention. In a specific embodiment, ultrafiltration is used to remove all components with a molecular weight greater than 30 kDa. By removing high-molecular weight components from the yeast extract, spores as well as proteins and DNA that were not sufficiently hydrolysed are removed minimizing batch-to-batch variation between different yeast extract preparations and guaranteeing a highly reproducible fermentation process.

In a further embodiment, the yeast extract is deferrated. As explained below, high iron concentrations inhibit the expression of the diphtheria toxin during the growth of C.diphthericie. Methods for deferrating a ycast extract arc commonly known to the skilled person. For example, the process described by Stainer & Scholtc [11] may be used to precipitate iron from the yeast extract prior to its use in a fermentation medium. Iron can be precipitated by dissolving yeast extract in water, adjusting the pH to 9.3, adding Na2HPO4 and KH2PO4 to the yeast extract solution, heating the solution to 85°C, and adding Cad2. The precipitate is then formed by slowly cooling the solution. Particularly good results were achieved by dissolving yeast extract in water, adjusting the p11 to 9.3, heating the solution to 60°C, adding Na2HPO4 and KI-12P04 to the yeast extract solution, further heating the solution to 79°C, adding CaCI2, further heating the solution to 85°C, and then cooling the solution to 25°C over a period of three hours to allow the iron precipitate to form. The precipitate can be removed e.g. by filtration or centriftigation.

In,, nreferre.d embodiment iiltrnfiltnilinn nnd rlpfprrntntir,n 0f the yeast extrnrt nrc rnnibinprl It nn -----., ..-found that the combination of both ultrafiltration and deferratation of the yeast extract prior to the addition of both the growth factors and an iron supplement resulted in a fermentation medium that yields diphtheria toxin of about 200 Lf/ml or more when used to grow C. diphtheriae.

In another preferred embodiment, the yeast extract is the sole source of all essential amino acids in the fermentation medium. While some amino acids such as fi-alanine and L-cysteine may be added separately as part of the growth factors, yeast extract can provide all amino acids required for the growth of C.diphtimeriae and therefore reduces the number of components needed to prepare the fermentation medium as well the overall cost of providing a chemically defined medium.

In a further embodiment, instead of using a yeast extract, the nitrogen source of the fermentation medium can be selected from a rice wheat peptone, a ricc peptone, a wheat pcptone, a soy peptone, a cotton peptone, a pea peptone, and a potato peptone. In some embodiments, however, a fermentation medium does not include soy peptone.

Carbon SoUrce Various carbon sources have been used to grow C. diphtheriae including glucose and glycerol. The addition of a separate carbon source is not absolutely necessary if a carbon-containing nitrogen source is used (C.diphtheriae can assimilate carbon from amino acids), but growth rates are much higher during fermentation if an additional carbon source is present.

In general, the higher the concentration of the carbon source, the higher the yield of toxin that can he achieved during culture. However, high concentrations of nionosaceharides such as glucose can cause problems due to the increased osmolality of the medium. Thus, in order to provide maximal amounts of a carbon source for optimal growth of C.diphthericte under fermentation conditions, the use of a dissacharide in the fermentation medium is preferred.

In one embodiment, the fermentation medium comprises at least 0.08 M of a disaccharide as carbon source. in another embodiment, the fermentation medium comprises between 0.08 M and 0.16 M of a disaccharide as a carbon source. in a thrther embodiment, the fermentation medium comprises between 0.1 M and 0.15 M of a disaccharide as a carbon source. In a specific embodiment, the concentration of the disaccharide in the fermentation medium of the invention is about 0.15 M. Various disaccharides may be used in the fermentation medium of the invention and in the process of preparing the fermentation medium. Suitable disaccharides include sucrose, lactulose, lactose, maltose, trehalose, and cellobiose. In a specific embodiment, the disaccharide of the fcrmentation medium is a reducing disaccharide such as cellobiose or maltose. in a particular embodiment, the disaccharide is IS maltose.

Excellent yields of diphtheria toxin were achieved, when C.diphlheriae was grown in a fermentation medium supplemented with 50 gIL maltose.

Phosphorus Phosphorus in form of phosphate is an essential component of many biomolecules. For example, DNA, RNA and the phospholipids that form the cell membrane contain phosphate. Therefore, phosphorus is an essential component of the fermentation medium of the invention. If yeast extract is used as a nitrogen source, the addition of phosphorus to the fermentation medium is typically not required because yeast extract contains sufficient sources of phosphate in form of e.g., nucleotides and phospholipids.

Growth fuc/ors During rapid growth of C.diphtheriae in a fermenter, certain components of the fermentation may become rate-limiting. By supplementing the fermentation medium with these components the yield of diphtheria toxin can further be improved. Therefore, these components are generally referred to as "growth factors." Suitable growth factors include magnesium, copper, zinc, manganese, pimelic acid, nicotinic acid and -alanine. in some embodiments, magnesium is provided in form of MgSOe7I-120, copper is provided in form of CuSO45H2O, zinc is provided in form of ZnSO47I-120, and manganese is provided in form of MnCI24H2O.

Iron source High iron conccntrations in a culture medium inhibit the expression of the diphtheria toxin during growth of Cdiphtheriae. Removing excess iron from the medium is therefore necessary to give high-yield toxin production during fermentation of C.diphtheriae. Methods for deferrating culture media are commonly known to the skilled person e.g. as described by Stainer & Scholte [II].

If levels of iron are too low, however, growth of C.diphlheriae is negatively affected. After deferration, therefore, a fermentation medium should still provide a source of iron during growth, but not at levels which prevent the production of diphtheria toxin. The main source of iron in the fermentation medium can stem from the material used as a nitrogen source, which traditionally has been animal-derived. If a yeast extract is used as a source of nitrogen, it may be deferrated to lower the lion concentration to a level that allows high-yield diphtheria toxin production during fermentation. However, if iron levels are so low that bacterial growth is inhibited (e.g after total deferration) the fermentation medium must be supplemented with iron to support growth of C.diphtheriae.

In one embodiment, a fermentation medium comprises a salt of Fe(ITI). One example of a salt of Fe(III) is ammonium ferric citrate. In another embodiment, the fermentation medium comprises a salt of Fe(II).

One example for a salt of Fe(II) is ferrous sulphate heptahydrate. In one embodiment, the starting Fe(II) or Fe(I1l) concentration in a fermentation medium is between 1.5.tM and 30 iM. In another embodiment, the starting Fe(lI) or Fe(III) concentration is between 3-15 liM. In a further embodiment, the starting Fe(TI) or Fe(III) concentration is between 5-13 pM. In a specific embodiment, the starting Fe(II) or Fe(III) concentration is between 10-14 pM.

In order to allow sufficient amounts of iron to be present throughout the fermentation process, hut without IS reaching concentrations which inhibit toxin production, an iron supplement is generally added as a slow-release formulation. Thus, in a specific embodiment, the fermentation medium is supplemented with a slow-release formulation of iron. A slow-release formulation of iron to supplement the fermentation medium can be produced by adding an ammonium ferric citrate solution and a phosphate solution to the fermentation medium prior to its use and by precipitating the iron through addition of a calcium chloride solution. This leads to the formation of a gel-like precipitate that slowly releases iron into the fermentation medium during the fermentation process. Other ways of obtaining a slow-release formulation of iron will be apparent to the skilled person and are likewise encompassed by the invention.

Media Jbrms Fermentation media can be prepared as liquid medium or as solid medium. Alternatively, the fermentation medium may be prepared as dried powder. In one embodiment, solid medium may be prepared by the addition of agar to a liquid medium. A solid medium prepared in accordance with the invention might be especially useful to prepare a master seed bank of C.diphtheriae. The master seed may be used to prepare a working seed. The working seed in turn is used to inoculate the fermentation medium of the invention for growing large amounts of C. diphtheriae in the preparation of diphtheria toxin for use in vaccines.

Media preparation In one aspect the invention relates to a process for preparing the fermentation medium of the invention. In one embodiment, a process for preparing the fermentation medium of the invention comprises adding to water (or to another aqueous liquid) a nitrogen source and a carbon source. Depending on iron levels of the material used as nitrogen source, the process may also comprise adding an iron supplement. Further, the process may comprise adding growth factors and phosphorus.

In a particular embodiment, a process for preparing a fermentation medium of the invention comprises dissolving yeast extract in water, deferrating the yeast extract, and adding a disaccharide to a final concentration of at least 0.08 M (see above).

In another embodiment, the invention relates to a process for preparing a fermentation medium, wherein the process comprises dissolving yeast extract in water, deferrating the yeast extract, and adding a salt of Fe(II) or Fe(lll). The salt of Fe(ll) or Fe(JII) may be added in such a way that a slow release formulation of iron is formed (see above).

In another embodiment, a process for preparing a fermentation medium of the invention can include a step of ultrafiltrating a yeast extract.

In yet another embodiment, the invention relates to a process for preparing a fermentation medium, wherein the process comprises preparing a low-mannan yeast extract and dissolving the yeast extract in water.

Any of the processes described above may be combined to prepare the fermentation medium of the invention. For example, in addition to dissolving yeast extract in water, deferrating the yeast extract, and adding between 0.08 M and 0.16 M of disaccharide, the process for preparing the fermentation medium of the invention may further comprise one or more ultrafiltration step. Alternatively or in addition, a salt of Fe(II) or Fe(Ill) may be added to the fermentation medium prior to its use.

tires of media Fermentation media may be used in a process for growing C.diphtheriae comprising culturing a strain of C.diphtheriae in a fermentation medium of the invention.

In a preferred embodiment, the process for growing Cdiphtheriae comprises inoculating a fermentation medium of the invention with a working seed that is free of animal-derived components and has been prepared without the use of animal-derived components. In the most preferred embodiment, the entire process trom creating a master seed bank to growing (JLdiphehenae in a fermentation medium, via to preparation of a working seed, is performed in the absence of animal-derived components. In another embodiment, the master seed bank and the working seed have been produced by a traditional process using a fermentation medium comprising animal-derived components, but fermentation of C.diphtheriae is perfoimed in medium free from animal-derived components.

C.diphtheriae is cultured in aerobic conditions. Sufficient aeration is important to achieve high growth rates. Sufficient aeration is achieved e.g., by agitation at 580 to 620 rpm in a 300 L vortex fermenter.

Pressurized air may be added to the fermenter at a rate of 60 L/min. An antifoam agent such as an active silicone polymer (e.g., antifoam A) may be added to prevent foam-formation due to agitation.

Industrial fermentation of C.diphtheriae in the past did not achieve high yields of diphtheria toxin when a fermentation medium free of animal-derived components was used. Reference 3 discloses that growing C.diphtheriae in 100 ml. of a fermentation medium free of animal-derived components. comprising yeast extract as the nitrogen source, yielded only 60 Lf/mL of diphtheria toxin. Reference 4 grew C.dip.htheriae in 240 L of a fermentation medium free of animal-derived components comprising yeast extract and all 20 essential amino acids as nitrogen source and yielded only maximally 100 Lf/mL of diphtheria toxin. In reference 5,200 mL of a fermentation medium free of animal-derived components and comprising rice-wheat peptone as the main nitrogen source yielded no more than 118 Lf/mL of diphtheria toxin. When yeast extract was used in place of the rice-wheat peptone, the concentration was even lower at 59 Lf/mL.

In contrast, fermentation media of the present invention are particularly suitable for growing C.diphtheriae to achieve a concentration of diphtheria toxin (or derivative) of at least 140 Lf/mL.

Routinely, toxin concentrations of at least 200 Lf/mL can be achieved. In certain embodiment, the concentration of the diphtheria toxin or the derivative in the fermentation medium exceeds 200 LD'mL and is equal to or greater than 250 IS/niL.

Accordingly, in one aspect, the invention also relates to a process for high-yield, industrial scale production of diphtheria toxin or a derivative thereof Such a process comprises culturing a strain of C.diphtheriae in 100 L or more of a fermentation medium free of animal-derived components, growing the culture to provide a toxin (or derivative) concentration of at least 140 Lf/rnl in the fermentation medium, and separating the diphtheria toxin or the derivative from the fermentation medium. In a preferred embodiment, such a process is used to prepare a diphtheria toxin suitable for use in human vaccine production. In another embodiment, the process is used to prepare a derivative of a diphtheria toxin e.g, a mutant diphtheria toxin such as CRMI97.

In certain embodiments, volumes of at least 100 L of fermentation medium are used with the invention.

For instance, the volume of fermentation medium can be at least 200 L, at least 250 L, at least 300 L, at least 500 L, or at least 600 L. These industrial-scale volumes are suitable for human vaccine production.

In a particular embodiment, the process of the invention yields a concentration of at least 140 Lf/mL of diphtheria toxin or the derivative in the fermentation medium. For instance, a process of the invention can yield a concentration of at least 150 Lf/mL, of at least 200 LtimL, or of at least 250 Lt7mL of diphtheria toxin or the derivative in the fermentation medium.

In a particular embodiment, the invention relates to a process for preparing diphtheria toxin or a derivative thereof comprising growing a strain of C&rynebciclerium diphtherkie expressing a diphtheria toxin or a derivative thereof in the fermentation medium of the invention and separating the diphtheria toxin or the derivative from the fermentation medium.

In one embodiment, separation of the bacteria from the fermentation medium containing the diphtheria toxin or the derivative may he achieved by centrifugation. In another embodiment, separation of the bacteria from the fermentation medium containing the diphtheria toxin or the derivative is achieved by filtration. For example, the fermentation medium containing the diphtheria toxin or the derivative may he sterilized by means of filtration. In some embodiments, centrifugation and filtration are both applied in combination to separate the bacteria from the fermentation medium containing the diphtheria toxin or the derivative. In a particular embodiment, separation by centrifugation takes place prior to filter-sterilization of the fermentation medium containing the diphtheria toxin or the derivative In one embodiment, the filter used for filter-sterilization is not capable of shedding fibres. In another embodiment, the filter used for filter-sterilization comprises a membrane with a pore-size equal to or lcss than 0.22 mm. In a further embodiment, a preservative other than phenol is added to the filter-sterilized fermentation medium containing the diphtheria toxin or the derivative. In a preferred embodiment, no preservative is added to the filter-sterilized fermentation medium containing the diphtheria toxin or the derivative.

Toxin pu'ifl cation In a specific aspect of the invention, the diphtheria toxin used to prepare a diphtheria toxoid is purified prior to the detoxification step. Puri'ing the diphtheria toxin prior to toxoiding reduces cross-linking of components derived from the fermentation medium (e.g., proteins and/or peptides) to the diphtheria toxin during treatment with formaldehyde. Cross-linking of medium components is disadvantageous because it leads to a less homogenous product, which may lead to problems dining quaLity control, and it also has the potential to trap allergens in the toxoid. Purification of the diphtheria toxin prior to detoxification reduces or avoids these disadvantages. The avoidance of animal-derived components in a culture medium, combined with pre-detoxification purification, gives a potent toxoid of very high purity. Even where pre-detoxification purification has been used [8], residual animal-derived components from the C.diphtheriae culture medium will still become covalently cross-linked to the toxin during toxoiding, even though such cross-linked materials might not be readily detectable by routine analytical assays.

In one embodiment of the invention, the diphtheria toxin used for preparing the diphtheria toxoid is at least 85% pure. In a specific embodiment, the diphtheria toxin used for preparing the diphtheria toxoid is at least 90% pure. In another specific embodiment, the diphtheria toxin used for preparing the diphtheria toxoid is at least 95% pure.

In one embodiment, the diphtheria toxin used for preparing the diphtheria toxoid according to the invention has a purity of greater than 1500 Lt7rng nitrogen. In a specific embodiment, the diphtheria toxin used for preparing the diphtheria toxoid has a purity of at least 2000 LtYmg nitrogen. In another specific embodiment, the diphtheria toxin used for preparing the diphtheria toxoid has a purity of at least 2100 LV'mg nitrogen. In a further specific embodiment, the diphtheria toxin used for preparing the diphtheria toxoid has a purity of at least 2700 Lf/mg nitrogen.

The diphtheria toxin or the derivative may be purified from the fermentation medium in a number of ways known to the skilled person. In one embodiment, purification is performed by a method comprising c,ilnt,citp. nn'rnithtinn n n nrtriiInr nrnhnrlin,nnt n,irflrcitnn nf th rflnhtbprn tnvin ni derivative from the fermentation medium is performed by a method comprising anion exchange chromatography, ideally without any further downstream chromatography steps. In a further embodiment, the purification process includes one or more ultrafiltration steps.

In a further embodiment, the purified bulk diphtheria toxin obtained after purification is filter-sterilized and concentrated by means of diafiltration. These steps make it possible to store the purified bulk diphtheria toxin prior to detoxification without degradation due to microbial contamination and loss in activity. Concentrating the bulk has the additional advantage that less cold storage space is needed resulting in cncrgy savings.

Diphtheria toxin and derivatives thereof The invention is defined herein by reference to "diphtheria toxin or a derivative thereof'. Such derivatives are those which arc immunologically cross-reactive with diphtheria toxin i.e. when administered to a guinea pig, the derivative elicits antibodies which cross-react with diphtheria toxin. Many such derivatives are known in the art and are often referred to as numbered "CRM" proteins (cross-reacting material) e.g. CRM9, CRM45, CRM 102, CRMIO3, CRMIO7 [6]. Typically such derivatives are diphtheria toxin mutants which differ from the wild-type toxin by only a few (e.g. 1, 2, 3, 4, or 5) amino acid mutations (single amino acid insertions, substitutions, or dclctions), but truncation mutants (e.g. CRM45) are also known. These mutations can he in the A andlor B subunit of the mature toxin (the A subunit is responsible for the toxin's enzymatic activity, whereas the B subunit is responsible for binding to target host cells).

Where the invention involves a diphtheria toxin derivative, the preferred derivative is CRM 197 [12,13] in which a the wild-type residue Gly-52 in the A subunit is substituted by glutamate, leading to a loss of the toxin's NAD:EF2 ADP-ribosyltransferase activity, in preferred embodiments, however, the invention is used for production of diphtheria toxin (which may subsequently be toxoided) rather than for production of diphtheria toxin derivatives, so the references to derivatives of diphtheria toxin would be ignored.

T.letox4fieation In one aspect the invention relates to a process for detoxifying a diphtheria toxin to prepare a diphtheria toxoid. in one embodiment, the invention relates to a process for preparing a diphtheria toxoid, wherein the process comprises (i) growing a culture of a strain of C.diphtheriae expressing a diphtheria toxin in a fermentation medium that is free of animal-derived components, (ii) puri'ing the diphtheria toxin from the fermentation medium to obtain a purified diphtheria toxin, (iii) adding formaldehyde to the purified diphtheria toxin, and (iv) incubating the purified diphtheria toxin in the presence of formaldehyde to obtain the diphtheria toxoid.

Non-toxic derivatives of diphtheria toxin (e.g. CRM 197) can also be subjected to "detoxification" although in such circumstances the purpose of cross-linking with formaldehyde is generally to stabilise the protein rather than to remove toxic activity.

In one embodiment, the fermentation medium comprises yeast extract. In a specific embodiment, the yeast extract is the only source of all essential amino acids. In a further specific embodiment, the fermentation medium is a fermentation medium of the invention.

The invention also relates to a process for preparing a diphtheria toxoid comprising the steps of (i) growing a strain of C'.diph/heriae expressing a diphtheria toxin or a derivative thereof in a fermentation medium, (H) separating the diphtheria toxin or the derivative from the fermentation medium to obtain a diphtheria toxin solution, (iii) preparing a diphtheria toxin concentrate from the diphtheria toxin solution, (iv) adding to the concentrate an amide and formaldehyde, and (v) incubating the concentrate in the presence of the amide and formaldehyde to obtain the diphtheria toxoid.

Toxin concentration The concentration of the diphtheria toxin or derivative during detoxification is of particular importance in providing a streamlined and efficient industrial process to provide large amounts of diphtheria toxoid for vaccine production. For safety reasons, detoxification with formaldehyde is generally performed over a six-week period. Thus, having large volumes during detoxification requires additional storage space. In addition, detoxification is performed at 36±2°C in an incubator. Hence, using smaller volumes drastically reduces the energy used during the detoxification process. The higher the concentration of the diphtheria toxin or the derivative is during the detoxification step, the smaller is the volume that may be used for detoxification. A 20-fold reduction in volume due to concentration means that the diphtheria toxin or derivative from a 300 L incubator can easily he treated in a 20 L bottle. Thus, the purified bulk diphtheria toxin obtained after purification is preferably concentrated prior to detoxification.

In one embodiment, the concentration of the diphtheria toxin or the derivative in the concentrate is at least 20-fold higher than the concentration of the diphtheria toxin or derivative in the final fermentation medium. In another embodiment, the concentration is at least 25-fold higher e.g. at least 30-fold higher, or at least 35-fold higher.

S In a specific embodiment, the concentration of the diphtheria toxin or the derivative in the concentrate that is detoxified is at least 2000 I;f/mL. in a further specific embodiment, the concentration is at least 3000 LI7mL. In a particular embodiment, the concentration is at least 5000 Lf/mL.

In a preferred embodiment, the starting material of the detoxification process (i.e., the diphtheria toxin or derivative thereof) is obtained by growing a culture of a strain of Corynehacteriwn diphtheriae expressing a diphtheria toxin in a fermentation medium which is free from animal-derived components e.g. which comprises yeast extract (such as the fermentation medium of the invention).

Amide concentration The inclusion of an amide during detoxification with formaldehyde can prevent the cross-linking of diphtheria toxin to give multimeric complexes. However, high concentrations of an amide generally require higher concentrations of formaldehyde. Due to the toxicity of formaldehyde, lower concentrations of an amide during toxoiding are therefore preferred as this results in the use of less formaldehyde and therefore the production of smaller amounts of toxic waste during vaccine production.

in one embodiment, the concentration of the amide added for detoxification is no more than 0.1 NI. In another embodiment, the concentration is no mote than 0.05 M. in a further embodiment, the concentration is no more than 0,025 M. In a particular embodiment, the concentration of the amide used for detoxification is in the range of 0.025 M and 0.1 M. in a specific embodiment, the concentration is about 0.025 M. in a particular embodiment, the amide is an amino acid such as glycine or lysine. It is preferably lysine.

It was found that using 0.025 M lysine in combination with 1% formaldehyde reduces the formation of multimeric complexes and results in a particularly preferred diphtheria toxoid composition in which the vast majority of the diphtheria toxoid is present in monomeric form.

Formaldehyde concentration To prevent adverse reactions during vaccination due to the toxicity of diphtheria toxin, toxicity is destroyed e.g. by incubating the diphtheria toxin concentrate in the presence of formaldehyde. If too high concentrations of formaldehyde are used, the final vaccine prepared with the bulk diphtheria toxoid may contain levels of formaldehyde which arc unacceptable for human use. Thus, only certain ranges in the formaldehyde concentrations may be acceptable to prepare a bulk diphtheria toxoid suitable for use in manufacturing a human vaccine. In one embodiment, the concentration of formaldehyde used for detoxification is in the range of 0.5% and 1%. in another embodiment, the concentration is in the range of 0.75% and 1%. In a specific embodiment, the final concentration of formaldehyde is about 1%.

It has been found that 1% formaldehyde is sufficient to destroy the toxicity of the diphtheria toxin at concentrations of at least 2000 Lf/mL. Even at concentrations of 5000 LfImL diphtheria toxin, no retoxification was observed after 6 weeks storage at 37°C.

Based on these findings, amide concentrations per Lf of diphtheria toxin and formaldehyde concentrations per Lf of diphtheria toxin can be calculated. In a more specific embodiment, the invention therefore relates to a process for preparing a diphtheria toxoid comprising preparing a solution of a diphtheria toxin at a concentration of at least 2000 LtYmL; adding to the solution no more than 5 nmol of an amide per Lf of the diphtheria toxin and between 40 and 55 nmol formaldehyde per Lf of the diphtheria toxin; and incubating the resulting solution to obtain the diphtheria toxoid.

Formaldehyde for detoxification is typically used in the form of fornialin i.e. as an aqueous solution. The formalin may be a saturated water solution, containing about 40 volVo formaldehyde. Formalin can also include small amounts of stabilizers, such as methanol, to limit oxidation and polymerization.

Further processing steps A process for preparing a diphtheria toxoid in accordance with the invention may further comprise one or more filter-sterilization step(s). In one embodiment, the diphtheria toxin concentrate used for detoxification is filter-sterilized prior to the addition of formaldehyde. In another embodiment, the diphtheria toxoid resulting from the detoxification process of the invention is filter-sterilized. In a further embodiment, both the diphtheria toxin concentrate and the diphtheria toxoid are filter-sterilized. Applying one or more filter-sterilization step(s) during preparation of the diphtheria toxoid has the advantage that the use of a preservative to prevent contaminating bacterial growth may be avoided. The avoidance of a preservative may prevent adverse reactions caused by the preservative when a vaccine comprising the diphtheria toxoid of the invention is administered to a human. If a preservative is added to the diphtheria toxoid for storage, a preservative other than phenol is preferred. In a preferred embodiment, no preservative is added to the diphtheria toxoid.

In one embodiment, the process for preparing the diphtheria toxoid may Further comprise a particle filtration step.

In another embodiment, the process may further comprise a step for concentrating the diphtheria toxoid for storage. High protein concentration during storage is preferred as it results in less degradation of the hulk diphtheria toxoid than if the bulk diphtheria toxoid is stored in diluted form. In a specific embodiment, concentration is done by diafiltration. In a particular embodiment, the final concentration of the diphtheria toxoid for storage is 10,000 If/mL. Thus the invention also provides a method for storing diphtheria toxoid in concentrated aqueous form (e.g. for a period of at least 1 week, at least I month, or at least 3 months) wherein the concentration of diphtheria toxoid is at least 5,000 Lffml e.g. at least 7,500 MimI, at least 10,000 LJ7ml, c/c.

In some embodiments, the process for preparing the diphtheria toxoid further comprises a step in which p1-I of the resulting diphtheria toxoid solution is adjusted to between 6-0 and 8.0. At this p14, the diphtheria toxoid is stable and suitable for administration to a human. In a specific embodiment, the pH of the final diphtheria toxoid solution is adjusted to 7.2-7.8. In a more specific embodiment, the pH of the final diphtheria toxoid solution is adjusted to 7.5.

Diphtheria toxoid compositions Employing a process for detoxifying a diphtheria toxin or derivative disclosed herein results in the provision of a diphtheria toxoid that is of higher purity than toxoids prepared in the prior art. In particular, the diphtheria toxoid produced by the methods of the invention is free from formaldehyde-crosslinked animal-derived components. Avoidance of animal-derived components in the fermentation medium and in the detoxification procedure means that the final material is absolutely free from animal-derived components, so that no such components can become covalently cross-linked to thc toxin during toxoiding, whereas prior art toxoids produced after growth in media containing animal-derived S components wilt inevitably contain cross-linked animal-derived components, even though these might not be readily detectable by routine analytical assays. Thus these toxoids of the invention are advantageous because they have a homogcneous composition which is free of materials such as prions etc. In a specific embodiment, a process for detoxi'ing a diphtheria toxin or derivative yields a diphtheria toxoid that is at least 90% pure (i.e. diphtheria toxoid is at least 90% by mass of the protein in the purified material e.g. as assessed by peak areas in I-IPLC analysis). In further specific embodiment, a process for detoxifying a diphtheria toxin or derivative disclosed herein yields a diphtheria toxoid that is at least 95% pure. In another specific embodiment, a process for detoxifying a diphtheria toxin or derivative disclosed hcrein results in a diphtheria toxin that contains yeast coinponcuts in trace amounts Sufficient to cause an allergic reaction.

In a further embodiment, the diphtheria toxoid solution rcsulting from detoxification process of the invention comprises no more than 0.2 g'L free formaldehyde (i.e. formaldehyde in solution that has not formed cross-links with proteins). In a more specific embodiment, the diphtheria toxoid solution resulting from the detoxification process of the invention comprises between 0.1 and 0.15 gIL free formaldchyde.

In another embodiment, a process for detoxifying a diphtheria toxin or derivative yields a diphtheria toxoid with greater than 1500 Lf/mg nitrogen. Thus a preferred diphtheria toxoid solution resulting from the detoxification process of the invention can comprise greater than 1500 Lf/mg nitrogen. In a particular embodiment, the diphtheria toxoid solution resulting from the detnxifir.ntinn process of the invention comprises greater than 2000 LI/mg nitrogen. In a specific embodiment, the diphtheria toxoid solution resulting from the detoxification process of the invention comprises greater than 2100 Ltimg nitrogen. In a further specific embodiment, the diphtheria toxoid solution resulting from detoxification process of the invention comprises greater than 2700 Lf1mg nitrogen.

The invention also relates to combinations of any of the processes described therein. For example, the process for preparing diphtheria toxin or a derivative thereof comprising culturing a strain of C. diphtheriae in the fennentation medium of the invention may be combined with a process for preparing a diphtheria toxoid disclosed herein. Combining these processes is particularly advantageous since it results in a very high-yield industrial production process for providing a highly purified, defined diphtheria toxoid without the need for employing any animal-derived components in the process.

In a further aspect, the invention relates to a diphtheria toxoid, wherein the diphtheria toxoid has a monomer:dimer ratio in the range of 3:1 to 8: and an isoelectrie point in the range of 4.0 to 5.0. In one embodiment, the diphtheria toxin of the invention comprises yeast components in trace amounts insufficient to cause an allergic reaction, but in another embodiment, the diphtheria toxoid of the invention is essentially free from both animal-derived components and from yeast components In a particular embodiment, the diphtheria toxoid of the invention is free from animal-derived components. In a further embodiment, the diphtheria toxoid of the invention comprises less than 0.001 gIL free formaldehyde. In yet a ftrthcr embodiment, the diphtheria toxoid of the invention comprises less than 0.0001 gIL free formaldehyde. In a specific embodiment, the diphtheria toxoid is free of detectable amounts of residual free formaldehyde.

In one embodiment, compositions of the invention comprise a diphtheria toxoid in both monomeric and dimeric form, wherein at least 80% of the diphtheria toxoid is in monomeric form and wherein the composition is free from animal-derived components.

In one aspect, the invention relates to a composition suitable as a vaccine for human use comprising a diphtheria toxoid free of formaldehyde-crosslinked animal-derived components, wherein said composition has a potency of at least 30 Ri per unit dose. In one specific embodiment, a composition of the invention has a monomer:dimer ratio of the diphtheria toxoid in the range of 3:1 to 8:1 and wherein the diphtheria toxoid comprised in the composition has an isoelectric point in the range of 4.0 to 5.0. In another specific embodiment, a composition of the invention comprises the diphtheria toxoid both in monomeric and dimeric form and wherein at least 70% of the diphtheria toxoid is in monomeric form. In some embodiments, a composition of the invention comprises at least one protective antigen from a pathogen other than Corynebacterluin diphtheriae. The protective antigen may he selected from hepatitis B virus surface antigen, tetanus antigen, pertussis antigen, Flib antigen, meningococeal antigen, pneumoeoccal antigen, and IPV antigen.

Vaccine formulations The invention also encompasses vaccine compositions which comprise a diphtheria toxoid of the invention, or which are made by a process using a diphtheria toxoid of the invention. In these compositions, the potency of the diphtheria toxoid should beat least 25 lU/dose e.g at least 50 IU/mL.

These vaccine compositions will generally be combination vaccines i.e. including at least one protective antigen from a pathogen other than C.diphtheriae. The additional protective antigen(s) can be viral and/or bacterial. Typicat bacterial pathogens include, but are not limited to: Clostridluin (elan!, Bordetella pertussis; J-Jaemophilus influenzae type b; /Jeisseria meningitidis, including serogroups A, B, C, Wl35 and/or Y; and Streptococcus pneurnoniae, including serotypes 6B, 14, 19F, and 23K Typical viral pathogens include, but arc not limited to: poliovirus; hepatitis A virus; measles virus; mumps virus; rubella virus; and varicella zoster virus.

Telarna Cg'ostridiwn tetani causes tetanus. Tetanus toxin can be treated to give a protective toxoid. The toxoids are used in tetanus vaccines, and are disclosed in more detail in chapter 27 of reference 1. Thus a combination vaccine of the invention can include a tetanus toxoid. Preferred tetanus toxoids are those prepared by formaldehyde treatment. The tetanus toxoid can be obtained by growing C.tetani in growth medium (e.g. a Latham medium derived from bovine casein), followed by formaldehyde treatment, ultrafiltration and precipitation. The material may then be treated by a process comprising sterile filtration and/or dialysis.

Quantities of tetanus toxoid can be expressed in [V units (see below), defined as the amount of toxoid which, when mixed with one International Unit of antitoxin, produces an optimally flocculating mixture [68], The NIBSC supplies The 1st International Reference Reagent for Tetanus Toxoid For Flocculation Test' [14] which contains 1000 LF per ampoule, by which measurements can he calibrated.

The immunizing potency of tetanus toxoid is measured in international units (IU), assessed by comparing the protection afforded by a composition in laboratory animals (typically guinea pigs) with a reference vaccine e.g. using NIHSC's Tetanus Toxoid Adsorbed Third International Standard 2000' [15,16], which contains 469 IIJ per ainpoule. The potency of tetanus toxoid in a composition of the invention should be at least 35 IU per dose e.g. at least 70 lU/mi.

Pertussis Bordetelkipertussis causes whooping cough. Pertussis antigens in vaccines are either ecilular (whole cell, in the form of inactivated B.pertussis cells; wP') or aceliular (aP'). Thus a combination vaccine of the invention can include a cellular pertussis antigen or an accllular pertussis antigen.

Preparation of cellular pertussis antigens is well documented (e.g. see chapter 21 of reference 1) e.g. it may be obtained by heat inactivation of phase I culture of B.pertussLc. Where acellular antigens are used, one, two or (preferably) three of the following antigens are included: (I) detoxified pertussis toxin (pertussis toxoid, or PT'); (2) fllamentous hemagglutinin (FHA'); (3) pertactin (also known as the 59 kiloDalton outer membrane protein'). These three antigens are preferably prepared by isolation from B.pertussis culture grown in modified Stainer-Scholte liquid medium. PT and FIIA can be isolated from the fermentation broth (e.g. by adsorption on hydroxyapatite gel), whereas pertactin can be extracted from the cells by heat treatment and flocculation (e.g. using barium chloride). The antigens can be purified in successive chromatographic and/or precipitation steps. PT and FHA can be purified by hydrophobic chromatography, affinity chromatography and size exclusion chromatography. Pertactin can be purified by inn exchange chromatography, hydrophobic chromatography and size exclusion chromatography.

FUA and pertactin may be treated with formaldehyde prior to use according to the invention. PT is preferably detoxified by treatment with formaldehyde and/or glutaraldehyde. As an alternative to this chemical detoxification procedure the PT may be a mutant PT in which enzymatic activity has been reduced by mutagenesis [17], but detoxification by chemical treatment is more usual.

Quantities of wP antigens can be expressed in international units (JU). For example, the NIBSC supplies the Third International Standard For Pertussis Vaccine' [18], which contains 46 IU per anipoule. Each ampoule contains the freeze-dried residue of 2.0 ml aliquots of an aqueous solution which contained 10 litres of bacterial suspension (equivalent to 180 opacity units in terms of the U.S. Opacity Standard) diluted with eight litres of M/i 5 Sorensen's buffer p11 7.0. As an alternative to the lU system, the OU' unit ("opacity units") is also used (e.g 4 OU may be about I Ui). The concentration of wP antigen in a composition of the invention is typically at least S lU/mI e.g. 41U/dose.

Quantities of aP antigens are typically expressed in ig. The concentration of PT in a vaccine is typically Sjig/ml, lSpgIml, 2Opg/ml or 50Ig/mI. The concentration of FHA in a vaccine is typically lOpg/nil, I 6j.tg/ml or 50tg/ml. The concentration of pertactin in a vaccine is typically 5ig/ml, 6Lg/ml or lSpg/ml. HTh

Haernophilus infiuenzae type b (Hib') causes bacterial meningitis. Hib vaccines are typically based on the capsular saccharide antigen (e.g. chapter 14 of ref 1), the preparation of which is well documented (e.g. references 19 to 28). The H. influenzae bacteria can be cultured in the absence of animal-derived components. The Hib saccharide is conjugated to a carrier protein in order to enhance its immunogenieity, especially in children. Typical carrier proteins in these conjugates are tetanus toxoid, diphtheria toxoid, the CRM 197 derivative of diphtheria toxin, or an outer membrane protein complex from serogroup B meningococcus. Thus a combination vaccine of the invention can include a J-Iib capsular saccharide conjugated to a carrier protein.

Tetanus toxoid is the preferred carrier, as used in the product commonly referred to as PRP-T'. PRP-T can be made by activating a Hib capsular polysaecharide using cyanogen bromide, coupling the activated saceharide to an adipic acid linker (such as (l-ethyl-3-(3-dimethylaminopropyl) carbodiimide), typically the hydrochloride salt), and then reacting thc linkcr-saccharide entity with a tetanus toxoid carrier protein.

The saccharide moiety of the conjugate may comprise full-length polyribosylribitol phosphate (PRP) as prepared from Hib bacteria, and/or fragments of full-length PRP. Conjugates with a saccharide:protein ratio (ww) of between 1:5 (i.e. excess protein) and 5:1 (i.e. excess saccharide) may be used e.g. ratios between 1:2 and 5:1 and ratios between 1:1.25 and 1:2.5. In preferred vaccines, however, the weight ratio ofsaccharide to carrier protein is between 1:2.5 and 1:3.5. In vaccines where tetanus toxoid is present both as an antigen and as a carrier protein then the weight ratio of saccharide to carrier protein in the conjugate may be between 1:0.3 and 1:2 [29]. Administration of the I Jib conjugate preferably results in an anti-PRY antibody concentration of >0.1 52g/ml, and more preferably >1 tg/ml, and these are the standard response thresholds.

Quantities of Hib antigens are typically expressed in ig of saccharide. The concentration of saceharide in a vaccine is typically between l0-30g/ml e.g. 20g/ml.

Meningococcus Neisseria ineningitidis causes bacterial meningitis. Based on the organism's capsular polysaccharide, various serogroups of N. ineningitidis have been identified, including A, B, C, H, I, K, L, 29E, W 135, X, * Uc Z_. I tfl.. Jv.flWfUflNfltsto ua1⁄4.L1⁄4t1a.a$I L1.I..tl!LUI 1⁄4,IJ Ill LL11⁄4 CIIflcILL.L. UI altl,llaI-ucj lvcu UI11pVIII..IIL. I IlL.

serogroups most associated with disease are A, B, C, W135 andY. Current vaccines against serogroups A, C, W135 andY are based on the capsular saccharide antigens, but this approach is not suitable for serogroup B, and so protein antigens and outer-membrane vesicles are used instead [30]. The capsular saccharides are conjugated to carrier proteins in order to enhance immunogenicity. Typical carrier proteins are tetanus toxoid (as in the NTMENRIXTM product), diphtheria toxoid (as in the MFNACTRATM product), and the CRM197 derivative of diphtheria toxin (as in the MFNVEOTM product). Thus a combination vaccine of the invention can include one or more (e.g. 2, 3, or 4) of capsular saccharides, conjugated to a carrier protein, selected from: (1) serogroup A NmeningitidLc; (2) serogroup C N.meningitidis; (3) serogroup W135 N.meningitidis; and/or (4) serogroup YNaneningitidis; The saccharide moiety of the conjugate may comprise full-length saccharide as prepared from meningococci, and/or fragments thereof Serogroup C saccharides may he prepared from either OAc-4-or OAc-strains. For scrogroup A saccharides, preferably at least 50% (e.g. at least 60%, 70%, 80%, 90%, 95% or more) of the mannosamine residues are 0-acetylated at the C-3 position. Mcningococcal conjugates with a saccharidc:protcin ratio (w/w) of bctween 1:10 (i.e. excess protein) and 10:1 (i.e. excess saccharide) may be used e.g. ratios between 1:5 and 5:1, between 1:2.5 and 2.5:1, or between 1:1.25 and 1.25:1. Administration of a conjugate preferably results in an increase in serum bactericidal assay (SBA) titre for the relevant serogroup of at least 4-fold, and preferably at least 8-fold. SBA titres can he measured using baby rabbit coniplerncnt or human complement [31].

Quantities of meningococcal antigens are typically expressed in pg of saccharidc. The concentration of saccharide in a vaccine is typically between 5-3Opg/ml per serogroup eg. lOpgIml or 2OpgIml.

Pneumococcus Streptococcus pnewnoniae causes bacteria! meningitis. Like Hib and meningococcus, existing vaccines are based on capsu!ar saccharidcs. The S.pneumoniae bacteria can be cultured in the absence of animal-derived components. Thus a combination vaccine of the invention can include a pneumococcal capsular saccharide conjugated to a carrier protein.

It is preferred to include saccharides from more than one serotype of S.pneumoniae, and particularly at least serotypes 6B, 14, 1917 and 23F. Further scrotypes are preferably selected from: 1,3,4,5, 7F, 9V and 18C. For example, mixtures of polysaccharidcs from 23 different serotype are widely used, as are conjugate vaccines with polysaccharides from betwccn 5 and 11 different serotypes [32]. For example, PREVNARTM [33] contains conjugated saccharides from scven serotypes (4, fiB, 9V, 14, I SC, 19F, and 2317), and SYNFLORIXTM contains conjugated saccharidcs from ten serotypes (1, 4, 5, 6B, 7F, 9V, 14, isC, 19F, 23F). Saccharides are preferably conjugated to carrier proteins [e.g. rcfs. 34 to 36]. Typical IS carrier proteins arc tetanus toxoid, diphtheria toxoid, the cRMI97 derivative of diphtheria toxin, and H influenzae protein D. Saccharides in the PREVNARTM product are individually conjugated to CRIvI1 97 by reductive amination, with 2pg of each saccharide per 0.5ml dose (4pg of serotype 6B).

SYNFLORIXTM uses three different carrier proteins and a mixture of different saccharide quantities for the different serogroups.

Quantities of pneumococcal antigens are typically expressed in pg of saccliaride. The concentration of a pneumococca! conjugate, measured as saccharide, is typically between 2 and 20 ig/mi for each serotypc.

Hepatitis B virus Hepatitis B virus (HBV) is a cause of viral hcpatitis. The 1-IBV virion consists of an inner core surrounded by an outer protein coat or capsid, and thc viral core contains the viral DNA genome. The major component of the capsid is a protein known as HBV surface antigen or, more commonly, HT3sAg', which is typically a 226-amino acid polypeptide with a molecular weight of 24 kDa. All existing hepatitis B vaccines contain FIBsAg, and when this antigen is administered to a normal vaccinee it stimulates the production of anti-J-lBsAg antibodies which protect against HBV infection. Thus a combination vaccine of the invcntion can include HBsAg.

For vaccine manufacture, HBsAg can be made in two ways he first method involves purifying the antigen in particulate form from the plasma of chronic hepatitis B carriers, as large quantities of HBsAg are synthesized in the liver and rcleased into the blood stream during an HBV infection. The second way involves expressing the protcin by recombinant DNA methods. HBsAg for use with the method of the invention should be recombinantly expressed in yeast cells. Suitable yeasts include Sarcharornyces (such as S. cerevisiac), Hanensula (such as Hpolymorpha) or Pichia hosts. The yeasts can be cultured in the absence of animal-derived components.

Unlike native 1-IBsAg (i.e. as in the plasma-purified product), yeast-expressed HBsAg is generally non-glycosylated, and this is the most preferred form of HBsAg for use with the invention. Yeast-expressed HBsAg is highly immunogenic and can be prepared without the risk of blood product contamination. Many methods for puri'ing 1-IBsAg from recombinant yeast are known in the art.

The FIBsAg will generally be in the form of substantially-spherical particles (average diameter of about 2Onm), including a lipid matrix comprising phospholipids. Yeast-expressed HBsAg particles may include phosphatidylinositol, which is not found in natural HBV virions. The particles may also include a non-toxic amount of LPS in order to stimulate the immune system [37]. The particles may retain S non-ionic surfactant (e.g. polysorhate 20) if this was used during disruption of yeast [38].

The HBsAg is preferably from HBV subtype adw2.

A preferred method for HBsAg purification involves, after cell disruption: ultrafiltration; size exclusion chromatography; anion exchange chromatography; ultracentrifugation; desalting; and sterile filtration.

Lysates may be precipitated after cell disruption (e.g. using a polyethylene glycol), leaving HBsAg in solution, ready for ultrafiltration.

After purification HBsAg may he subjected to dialysis (e.g. with cysteine), which can be used to remove any mercurial preservatives such as thimerosal that may have been used during HBsAg preparation [39].

Quantities of FIBsAg are typically expressed in micrograms. The concentration of HBsAg in a composition of the invention is preferably less than 60 jig/nil e.g 55 jig/mi, <50 jig/mI, <45 gg/ml, c40 pg/nil, etc. A concentration of about 20 jig/mI is typical e.g lOjig per dose.

Poliovirus Poliovirus causes poliomyelitis. Inactivated polio virus vaccine (IPV), as disclosed in more detail in chapter 24 of reference 1, has been known for many years. Thus a combination vaccine of the invention can include an inactivated poliovirus antigen.

Polioviruses may be grown in cell culture, and a preferred culture uses a Vero cell line, derived from monkey kidney. Vero cells can conveniently be cultured mierocarriers. After growth, virions may be purified using techniques such as ultrafiltration, diafiltration, and chromatography. Where animal (and particularly bovine) materials are used in the culture of cells, they should be obtained from sources that are free from transmissible spongiform encephalopathies (TSEs), and in particular free from bovine spongiform eneephalopathy (BSE). Preferably, polioviruses are grown in cells cultured in medium free of animal-derived components.

Prior to administration to patients, polioviruses must be inactivated, and this can be achieved by treatment with formaldehyde. Polioniyeiitis can he caused by one of three types of poliovirus. The three types are similar and cause identical symptoms, but they are antigenically very different and infection by one type does not protect against infection by others. It is therefore preferred to use three poliovirus antigens with the invention: poliovirus Type 1 (e.g. Mahoney strain), poliovirus Type 2 (e.g MEF-I strain), and poliovirus Type 3 (e.g. Saukett strain). The viruses are preferably grown, purified and inactivated individually, and are then combined to give a bulk trivalent mixture for use with the invention. Quantities of IPV are typically expressed in the DU' unit (the "D-antigen unit" [40]). It is preferred to use between 1-100 DU per polioviral type per dose e.g., about 40 flU of type 1 poliovirus, about 8 DLI of type 2 poliovirus, and about 32 DU of type 3 poliovirus (bitt it is possible to use lower doses than these [41,42] e.g 10-20 flU for type 1,2-4 DU for type 2, and 8-20 flU for type 3.

Where an IPV component is used, and the polioviruses were grown on Vero cells, a vaccine composition preferably contains less than lOngImI, preferably <ing/mi e.g <SOOpg/mi or<50 pg/mi of Vero cell DNA e.g. less than I Ong/mI of Vero cell DNA that is a50 base pairs long.

Preparing a combination vaccine Antigenic components from these pathogens for use in vaccines are commonly referred to by abbreviated names: D' for diphtheria toxoid; T' for tetanus toxoid; F' for pertussis antigens, with Pa' being acellular (e.g. including at least PT. FHA and pertactin) and Pw' being cellular; Hib' for conjugated Hinfluenzae b capsular saccharide; MenA', Meril&', McnC', MenW' and MenY' for the respective ineningococcal serogroups, separate'y conjugated to carrier proteins; IPV' for 3-valent inactivated poliovirus; and Spn' for pneuinococcus.

The following combination vaccines are preferred embodiments of the invention, wherein the D' component is a diphtheria toxoid prepared as disclosed herein: -D, 1 HBsAg -D,T,Pw,HBsAg -D, 1, Pw, HBsAg, Hib -D, 1, Pw, 1 IBsAg, Hib, MenA, MenC -D, 1, Pw, HBsAg, Hib, MenA, MenC, MenWl35 -D, 1, Pw, HBsAg, Hib, MenA, MenC, MenY D, 1, Pw, 1-IBsAg, Hib, MenA, MenC, N4enW 135, McnY -D, 1, Pa, HBsAg -D, T, Pa, Hib -D, 1, Pa, 1-IBsAg, Hib -D, 1, Pa, HBsAg, IPV -D, T, Pa, EffisAg, IPV, Hib -D, 1, Pa, HBsAg, IPV, Hib, Spn -D, 1, Pa, HBsAg, IPV, Nib, MenC -D, 1, Pa, T-lBsAg, IPV, Nib, MenC, MenA -D, 1, Pa, HBsAg, IPV, Nib, MenC, MenY -D, 1, Pa, HBsAg, IPV, Nib, MenC, MenW 135 -D, T, Pa, HBsAg, IPY, Nib, MenC, MenA, MenWl35, MenY These combination vaccines may consist of the antigens listed, or may further include antigens from additional pathogens. Thus they can be used separately, or as components of further vaccines.

When combining antigenic components to prepare a multivalent composition, the antigens can be added individually, or they can be pvc-mixed. Where a combination vaccine comprises D and T antigens and additional antigens, it is preferred to use a pre-mixed D-T component in the preparation of the combination vaccine. This bivalent component can be combined with further antigens. Where I), T and Pw antigens are used, it is preferred to use a pre-mixed D-T-Pw component, and then to use this component in the preparation of the combination vaccine.

Where a D-T mixture is used, the ratio of diphtheria toxoid to tetanus toxoid in the mixture is usually between 2:1 and 3:1 (measured in Lfunits), preferably between 2.4:1 and 2.6:1, e.g. preferably 2.5:1.

Carrier proteins for conjugates Conjugated saceharide antigens include a carrier protein, to which the saceharide is covalently attached, either directly or via a linker. General information on conjugation techniques can be found in ref. 28.

Various proteins are known for use as carriers, and preferred carrier proteins are bacterial toxoids, such as diphtheria toxoid (e.g. produced according to the invention) or tetanus toxoid. Other suitable carrier proteins include, hut are not limited to, the CRMI97 mutant of diphtheria toxin [43,44], the Nmeningitidis outer membrane protein [45], synthetic peptides [46, 7l, heat shock proteins 148,49], pertussis proteins [50,51], cytokines [52], lymphokines [52], hormones [52], growth factors [52], artificial proteins comprising multiple human CD4 I cell epitopes from various pathogen-derived antigens [53] such as Nl9 [54], protein D from H.influenzae [55,56], pneumocoecal surface protein PspA [57], pneumolysin [58], iron-uptake proteins [59], toxin A or B from C.d&icile [60], Sagalactiaé proteins [61], etc. Attachment of a saccharide to a carrier is preferably via a-Nfl2 group e.g. in the side chain of a lysine residue in a carrier protein, or of an arginine residue. Attachment to -Sil groups (e.g. in the side chain of a cysteine) is also possible.

Conjugates with a saccharidc:protein ratio (w/w) of between 1:5 (i.e. excess protein) and 5:1 (i.e. excess saccharide) are preferred.

Compositions may include a small amount of flee carrier. Ignoring any carrier included as a separate antigen, unconjugated carrier is preferably no more than 5% of the total amount of the carrier protein in the composition as a whole, and more preferably present at less than 2% by weight.

As in the SYNFLORIXfM product, it is possible to include more than one type of carrier protein in a composition e.g. to reduce the risk of carrier suppression.

Amounts of conjugates are generally given in terms of mass of saccharide (i.e. the dose of the conjugate as a whole (i.e. carrier + saccharide) is higher than the stated dose) in order to avoid variation due to choice of carrier.

Adjuvants Vaccines of the invention will generally include an adjuvant. The most usual adjuvant for inclusion is an aluminium salt, such as an aluminium hydroxide and/or an aluminium phosphate. Antigens in a combination vaccine can be adsorbed (partially or totally) to aluminium salts.

The ad] uvants commonly known as "aluminium hydroxide" are typically aluminium oxyhydroxide salts, which are usually at least partially crystalline. Aluminium oxyhydroxide, which can be represented by the formula A1O(Oli), can be distinguished from other aluminium compounds, such as aluminium hydroxide Al(OI-I)1, by infrared (lR) speetroscopy, in particular by the presence of an adsorption band at l070cin and a strong shoulder at 3090-3 lOOcnf' (chapter 9 of ref 62), The degree of crystallinity of an aluminium hydroxide adjuvant is reflected by the width of the diffraction band at half height (Wl-IH), with poorly-crystalline particles showing greater line broadening due to smaller crystallite sizes. The surface area increases as WHU increases, and adjuvants with higher Will-! values have been seen to have greater capacity for antigen adsorption. A fibrous morphology (e.g. as seen in transmission electron micrographs) is typical for aluminium hydroxide adjuvants e.g. with needle-like particles with diameters about 2nm. The p1 of aluminium hydroxide adjuvants is typically about II i.e. the adjuvant itself has a positive surface charge at physiological pH. Adsorptive capacities of between 1.8-2.6 mg protein per mg Al4 at p1-i 7.4 have been reported for aluminium hydroxide adjuvants.

The adjuvants commonly known as "aluminium phosphate" are typically aluminium hydroxyphosphates, often also containing a small amount of sulfate (i.e. aluminium hydroxyphosphate sulfate). They may be obtained by precipitation, and the reaction conditions and concentrations during precipitation influence the degree of substitution of phosphate for hydroxyl in the salt. Hydroxyphosphates generally have a P04/Al molar ratio between 0.3 and 1.2. Hydroxyphosphates can be distinguished from strict AIPO4 by the presence of hydroxyl groups. For example, an IR spectrum band at 3 l64cnft (e.g. when heated to 200°C) indicates the presence of structural hydroxyls (chapter 9 of ref. 62). The PO4IAl3 molar ratio of an aluminium phosphate adjuvant will generally be between 0.3 and 1.2, preferably between 0.8 and 1.2, and more preferably 0.95±0.1. The aluminium phosphate will generally be amorphous, particularly for hydroxyphosphate salts. A typical adjuvant is amorphous aluminium hydroxyphosphate with POIAI molar ratio between 0.84 and 0.92, included at 0.6mg A13*/ml. The aluminium phosphate will generally be particulate (e.g. plate-like morphology as seen in transmission electron micrographs, with primary particles in the range of SOnm). Typical diameters of the particles are in the range 0.5-20j.tm (e.g. about 5-t0im) after any antigen adsorption. Adsorptive capacities of between 0.7-1.5 mg protein per mg Alt at pH 7.4 have been reported for aluminium phosphate adjuvants.

The PZC of aluminium phosphate is inversely related to the degree of substitution of phosphate for hydroxyl, and this degree of substitution can vary depending on reaction conditions and concentration of reactants used for preparing the sa!t by precipitation. PZC is also altered by changing the concentration of free phosphate ions in solution (more phosphate = more acidic PZC) or by adding a buffer such as a histidine buffer (makes PZC more basic). Aluminium phosphates used according to the invention will generally have a PZC of between 4.0 and 7.0, more preferably between 5.0 and 6.5 e.g. about 5.7.

The concentration of AI in a composition for administration to a patient is preferably less than 10mg/nil e.g. <.5 mg/mi, <4mg/mi, <3 mg/mi, <2 mg/mI, <1 mg/mi, etc. A preferred range of Al in a composition of the invention is between 0.3 and 1mg/mI or between 0.3-0.5mg/mi. A maximum of 0.85mg/dose is typical.

In one embodiment, diphtheria toxoid is adsorbed onto an aluminium salt adjuvant e.g. is adsorbed to an aluminium hydroxide adjuvant.

in a combination vaccine comprising a tetanus toxoid, the tetanus toxoid may be adsorbed onto an aluminium hydroxide adjuvant, but this is not necessary (e.g. adsorption of between 0-10% of the total tetanus toxoid can be used).

!n a combination vaccine comprising a whole-cell pertussis antigen, the wP antigen is preferably combined with an aluminium hydroxide adjuvant and/or an aluminium phosphate adjuvant.

In a combination vaccine comprising acellular pertussis antigen(s), the pertussis antigen(s) may be adsorbed onto one or more an aluminium salt adjuvants, or may be added in an unadsorbed state. Where pertactin is present in a composition then it is preferably adsorbed onto an aluminium hydroxide adjuvant before being used in the process of the invention. PT and FIIA may be adsorbed onto an aluminium hydroxide adjuvant or an aluminium phosphate before being used in the process of the invention. In preferred embodiments, PT, FHA and pertactin are separately pre-adsorbed to aluminium hydroxide prior to being used in the process of the invention.

In a combination vaccine comprising Hib antigens and an aluminium salt, the fib conjugate may be unadsorbed or can be adsorbed (e.g adsorbed to an aluminium phosphate adjuvant [63]). Adsorption in this way is particularly useful in vaccines comprising D-T-Pw-Hib-l-IBsAg antigens. Other conjugated antigens (e.g meningococcus, pneumococcus) can similarly be adsorbed to an aluminium sail (e.g a phosphate) or can be unadsorbed [64].

IPV antigens are typically not adsorbed to any adjuvant belore being used in a process of the invention, but they can become adsorbed onto aluminium adjuvant(s) originating with other components.

In a combination vaccine comprising HBsAg, the 1-IBsAg can be adsorbed onto aluminium phosphate using the methods described in ret: 65. Adsorption to aluminium phosphate contrasts with the well-known ENGERIXBTM product (where HBsAg is adsorbed to aluminium hydroxide). As mentioned in reference 66, aluminium phosphate can be a better adjuvant for HBsAg than aluminium hydroxide.

Where a process of the invention utilises a component in which diphtheria and tetanus toxoids have been mixed prior to their being combined with HBsAg, this D-T mixture preferably contains an aluminium hydroxide adjuvant, to which the D and T antigens are both adsorbed.

Where a process of the invention utilises a component in which diphtheria toxoid, tetanus toxoid and whole-cell pertussis antigen have been mixed prior to their being combined with HBsAg, this D-T-Pw mixture preferably contains both an aluminium hydroxide adjuvant, to which the D and T antigens are adsorbed, and an aluminium phosphate adjuvant.

When an adjuvant is included in a vaccine of the invention, it can be added at various stages. Antigens can be combined with adjuvants before being used in preparing combination vaccines (e.g. a bivalent D-T mixture can be adsorbed to aiuminiurn salt adjuvant(s) before being used in a process of the invention), but it is also possible to add adjuvant after the antigens have been mixed, or to add a sequence of anti gens to an adjuvant (e.g. to start with an aqueous adjuvant, then to add antigens, either individually or pre-inixed).

Further non-antigen components Vaccine compositions of the invention may comprise carriers, excipients, buffers, etc. To control tonicity, a composition may include a physiological salt, such as a sodium salt. Sodium chloride NaCl) is preferred, which may be present at between 1 and 20 mg/mi In a specific embodiment, the sodium chloride concentration is between 8 and 9 mg/mI (e.g. about 8.5 mg/mI).

Compositions will generally have an osmolality of between 200 mOsm/kg and 400 mOsm/kg, preferably between 240-360 mOsm/kg, and will more preferably fall within the range of 280-320 mOsnVkg.

Osmolality has previously been reported not to have an impact on pain caused by vaccination [67], but keeping osmolality in this range is nevertheless preferred.

Compositions of the invention may include one or more buffer(s). Typical buffers include: a phosphate buffer; a Tris buffer; a borate buffer; a suecinate buffer; a histidine buffer; or a citrate buffer. Buffers will typically be included in the 5-20mM range.

Compositions of die invention may include one or more preservative(s), but in some embodiments the compositions are preservative-free. Preferred compositions are substantially free from mercurial preservatives (e.g. thimerosal) e.g. they contain less than 0.1 gg/ml of mercury, and preferably contains no detectable mercury. This will generally be achieved by removing the mercurial preservative from an antigen preparation prior to its addition in the process of the invention or by avoiding the use of thimerosal during the preparation of the components used to make the composition. However, the presence of trace amounts of a mercurial preservative may be unavoidable if a component (particularly HB5Ag) was treated with such a prescrvative before being used in the composition of the invention. For safety, however, it is preferred that the final composition contains less than about 25 ng/ml mercury.

In some embodiments, the composition comprising the diphtheria toxoid of the invention contains a preservative other than phenol. In one embodiment, the preservative is sodium thimerfonate. in another embodiment, the preservative is 2-phenoxyethanol (2-PE). If 2-PE is used, it is preferably prcsent (a) between 2.5mg and 3.5 ing (e.g. about 3 mg) for every 100 Lf of diphtheria toxoid, and/or (b) between 7 mgand 8 mg(e.g. about 7.5 mg) for every 100 Lf of tetanus toxoid. A 2-PE concentration of between 3 g/l and 8 g/l (e.g. between 4-6 gIl, or about 5 gIl) in the composition of the invention is preferred. In a particular embodiment, the composition of the invention comprises 167 Lf diphtheria toxoid; 67 Lf ftnnnc t,wniA c mci A composition of the invention can be substantially free from surffictants. In particular, the composition of the invention can be substantially free from polysorbate 80 e.g. it contains less than 0.1 ig/ml of polysorbate 80, and preferably contains no detectable polysorbate 80. Where a composition includes J-JBsAg, however, it will usually include polysorbate 20 e.g. if it was used during yeast disruption [38].

The p1-I of a composition of the invention will generally be between 5.0 and 7.5, and more typically between 5.0 and 6.0 for optimum stability or, where a diphtheria toxoid and/or tetanus toxoid is present, between 6.0 and 7.0. A process of the invention nay therefore include a step of adjusting the pH of the bulk vaccine prior to packaging.

Compositions of the invention are preferably non-pyrogenic e.g. containing <1 EU (endotoxin unit, a standard measure; 1 EU is equal to 0.2 ng FDA reference standard Endotoxin EC-2 RSE') per dose, and preferably <0.1 EU per dose.

Compositions of the invention are preferably gluten free.

Compositions of the invention arc preferably sterile.

Compositions of the invention are preferably in aqueous form. During manufacture, dilution of the antigens to give desired final concentrations will usually be performed with WFI (water for injection).

Residual material from individual antigenic components may also be present in trace amounts in a final vaccine composition of the invention. For example, if formaldehyde is used to prepare the toxoids of diphtheria, tetanus and pertussis then the final vaccine product may retain trace amounts of formaldehyde (e.g. less than l0Ag/mI, preferably <5p.tg/ml). Media or stabilizers may have been used during poliovirus preparation (e.g Medium 199), and these may carry through to the final vaccine. Similarly, free amino acids (e.g. alanine, arginine, aspartate, cysteine and/or cystine, glutamate, glutamine, glycine, histidine, proline and/or hydroxyproline, isoleucine, leucinc, lysine, niethionine, phenylalanine, serine, threonine, tryptophan, tyrosine and/or valine), vitamins (e.g. choline, ascorbate, etc.), disodium phosphate, monopotassium phosphate, calcium, glucose, adenine sulfate, phenol red, sodium acetate, potassium chloridc, etc. may be retained in the final vaccine at <lOOp.zg/ml, preferably <l0.tg/m1, each. Other components from antigen preparations, such as neomycin (e.g. neomycin sulfate, particularly from the TPV component), polymyxin B (e.g polymyxin B sulfate, particularly from the 1PV component), etc. may also be present at sub-nanogram amounts per dose. A further possible coniponent of the final vaccine which originates in the antigen preparations arises from less-than-total purification of antigens. Small amounts of B.pertussis, C.diphtheriae, C.tetani and S.cerevisiae proteins and/or genomic DNA may therefore be present. 1'o minimize the amounts of these residual components, antigen preparations are preferably treated to remove them prior to the antigens being used in the process of the invention.

Packaging compositions of the invention The invention can provide bulk material which is suitable for packaging into individual doses, which can then be distributed for administration to patients. Concentrations mentioned above arc typically concentrations in final packaged dose, and so concentrations in bulk vaccine may be higher (e.g. to be reduced to final concentrations by dilution).

Human intramuscular vaccines are generally administered as an individual dosage volume of 0.5m1.

Processes of the invention may thus comprise a step of extracting and packaging a 0.5m1 sample of the mixture into a container. References to 0.Sml doses will be understood to include normal variance e.g. 0.5m10.05ml. For multidose situations, multiple dose amounts will be extracted and packaged together in a single container e.g. SmI for a 10-dose multidose container (or 5.SmI with 10% overfill).

Processes of the invention may comprise a step of packaging the vaccine into containers for use. Suitable containers include vials and disposable syringes (preferably sterile ones).

Where a composition of the invention is packaged into vials, these are preferably made of a glass or plastic material. The vial is preferably sterilized before the composition is added to it. To avoid problems with latex-sensitive patients, vials are preferably sealed with a latex-free stopper. The vial may include a single dose of vaccine, or it may include more than one dose (a multidose' vial) e.g. 10 doses. When using a multidose vial, each dose should be withdrawn with a sterile needle and syringe under strict aseptic conditions, taking care to avoid contaminating the vial contents. Preferred vials are made of colorless glass.

A vial can have a cap (e.g. a Luer lock) adapted such that a pre-filled syringe can be inserted into the cap, the contents of the syringe can be expelled into the vial (e.g. to reconstitute lyophilised material therein), and the contents of the vial can be removed back into the syringe. After removal of the syringe from the vial, a needle can then be attached and the composition can be administered to a patient. The cap is preferably located inside a seal or cover, such that the seal or cover has to be removed before the cap can be accessed.

Where the composition is packaged into a syringe, the syringe will not normally have a needle attached to it, although a separate needle may be supplied with the syringe for assembly and use. Safety needles are S preferred. I-inch 23-gauge, 1-inch 25-gauge and 5/8-inch 25-gauge needles ale typical. Syringes may be provided with peel-off labels on which the lot number and expiration date of the contents may be printed, to facilitate record keeping. The plunger in the syringe preferably has a stopper to prevent the plunger from being accidentally removed during aspiration. The syringes may have a latex rubber cap and/or plunger. Disposable syringes contain a single dose of vaccine. The syringe will generally have a tip cap to seal the tip prior to attachment of a needle, and the tip cap is preferably made of butyl rubber. If the syringe and needle are packaged separately then the needle is preferably fitted with a butyl rubber shield.

Grey butyl rubber is preferred. Preferred syringes are those marketed under the trade name "TipLok"TM.

Where a glass container (e.g. a syringe or a vial) is used, then it is preferred to use a container made from a borosilicate glass rather than from a soda lime glass.

After a composition is packaged into a container, the container can then be enclosed within a box for distribution e.g. inside a cardboard box, and the box will he labeled with details of the vaccine e.g. its trade name, a list of the antigens in the vaccine (e.g. hepatitis B recombinant', etc.), the presentation container (e.g. Disposable Prefilled Tip-Lok Syringes' or lOx 0.5 ml Single-Dose Vials'), its dose (e.g. each containing one 0.Snil dose'), warnings (e.g. For Adult Use Only' or For Pediatric Use Only'), an expiration date, an indication, a patent number, etc. Each box might contain more than one packaged vaccine eg. five or ten packaged vaccines (particLiLarly for vials). If the vaccine is contained in a syringe then the nnrlrn np mT hnw i nirt,,re nf the urifloe *0 The vaccine may be packaged together (e.g. in the same box) with a leaflet including details of the vaccine e.g. instructions for administration, details of the antigens within the vaccine, etc. The instructions may also contain warnings e.g. to keep a solution of adrenaline readily available in case of anaphylaclic reaction following vaccination, etc. A packaged vaccine is preferably stored at between 2°C and 8°C. It should not be frozen.

Vaccines can be provided in hull-liquid form (i.e. where all antigenic components are in aqueous solution or suspension) during manufacture, or they can be prepared in a form where some components are in liquid form and others are in a lyophilized form. Thus a final vaccine can be prepared extemporaneously at the time of use by mixing together two components: (a) a first component comprising aqueous antigens; and (b) a second component comprising lyophilized antigens. The two components are preferably in separate containers (e.g. vials and/or syringes), and the invention provides a kit comprising components (a) and (b). This format is particularly useful for vaccines that include a conjugate component, particularly Hib and/or meningococcal and/or pneumococcal conjugates, as these may be more stable in lyophilized form (whereas D, f, p and HBsAg components are preferably in liquid form).

Thus conjugates may be lyophilised prior to their use with the invention. Further components may also be added prior to freeze-drying e.g. as stabilizers. Preferred stabilizers for inclusion are lactose, sucrose and mannitol, as well as mixtures thereof e.g. lactose/sucrose mixtures, suerose/mannitol mixtures, etc. The final vaccine may thus contain lactose and/or sucrose. Using a sucrose/mannitol mixture can speed up the drying process.

Thus the invention provides a process for preparing a two-container combination vaccine, comprising the following steps: S -preparing an aqueous combination vaccine as described above, but wherein the said one or more antigens does not include a conjugated capsular saccharide antigen; packaging said aqueous combination vaccine in a first container (e.g. a syringe); -preparing a conjugated capsular saccharide antigen in lyophilised form; -packaging said lyophilised antigen in a second container (e.g. a vial); and -packaging the first container and second container together in a kit.

The kit can then be distributed to physicians.

Methods of treatment and administration of the vaccine Compositions of the invention are suitable for administration to human patients, and the invention provides a method of raising an immune response in a patient, comprising the step of administering a composition of the invention to the patient. Compositions of the invention are preferably administered to patients in 0.Sml doses (as discussed above).

The invention also provides a composition of the invention for use in medicine. The invention also provides the use of the composition of the invention in the prevention of at least an infection with C.diphtheriae. Compositions of the invention are preferably vaccines for use in the prevention and/or treatment of at least an infection with C.diphtheriae.

The invention also provides the use of antigenic components as described herein (including diphtheria toxoids of the invention) for use in the manufacture of a vaccine.

In order to have full efficacy, a typical primary immunization schedule for a child may involve administering more than one dose. For example, doses may be at: 0 & 6 months (time 0 being the first dose); at 0, 1,2 & 6 months; at day 0, day 21 and then a third dose between 6 & 12 months; at 2, 4 & 6 months; at 3,4 & S months; at 6, 10 & 14 weeks; or at 0, 1, 2, 6 & 12 months.

Compositions can also be used as booster doses e.g. for children, in the second year of life.

Conipositions of the invention can be administered by intramuscular injection e.g. into the arm or leg Vaccines produced by the invention may be administered to patients at the same time as a separate vaccine e.g. at the same time as a pneumococcal conjugate vaccine such as PrevnarTM, at the same time as an influenza vaccine, at the same time as a rotavirus vaccine, at the same time as a MMR vaccine, etc. Where compositions of the invention include an aluminium-based adjuvant, settling of components may occur during storage. The composition should therefore be shaken prior to administration to a patient. The shaken composition will be a turbid white suspension.

Quantitative unitc for dip/it!, eria toxoid measurement Quantities of diphtheria toxin and/or toxoid in a composition are generally measured in the Lf' unit ("flocculating units", or the "limes flocculating dose", or the "limit of flocculation"), defined as the amount of toxin/toxoid which, when mixed with one International Unit of antitoxin, produces an optimally flocculating mixture [68,69]. For example, the NIBSC supplies Diphtheria Toxoid, Plain' 170], which contains 300 LF per ampoule, and also supplies The 1st International Reference Reagent For Diphtheria Toxoid For Flocculation Test' [71] which contains 900 Jf per ampoule. The concentration of diphtheria toxin or toxoid in a composition can readily be determined using a flocculation assay by comparison with a reference material calibrated against such reference reagents.

Purity of a protein preparation can be expressed by the ratio of specific protein to total protein. The purity of diphtheria toxin/toxoid in a composition is generally expressed in units of Lf diphtheria toxoid per unit mass of protein (nondialysable) nitrogen. For instance, a very pure toxin/toxoid might have a purity of more than 1700 Lf/mg N, indicating that most or all of the protein in the composition is diphtheria toxin/toxoid [72].

The immunizing potency of diphtheria toxoid iii a composition is generally expressed in international units (ILl). The potency can be assessed by comparing the protection afforded by a composition in laboratory animals (typically guinea pigs) with a reference vaccine that has been calibrated in TUs.

NIBSC supplies the Diphtheria Toxoid Adsorbed Third Tnternational Standard 1999' [73,74], which contains 160 IU per anipoLile, and is suitable for calibrating such assays.

A three-dilution assay can be used to determine the potency of the compositions of the invention. After immunization, the guinea-pigs are bled or challenged either by the subcutaneous or by the intraderinal I yuLe. Ifl UI! UI id flL1 ye eli i L)OUIIJ let IL. 1111cC UI C USCU Iii iUCd 01 gunict* pIES. VV lieU gttiuea pigs Li' It Ill-C I C bled, the antitoxin levels of the individual animals are titrated by means of toxin neutralization tests performed using in vim or in vi Ira serological methods that have been validated on vaccines of the types being tested. in one embodiment, diphtheria toxoids produced in fermentation medium comprising animal-derived components are used for validation. The potency of the composition of the invention is calculated using appropriate statistical methods. For three-dilution assays, the limits of the 95% confidence intervals of the estimate of potency is within 50-200% of the estimated potency unless the lower limit of the 95% confidence interval of the estimated potency is greater than 30 ILl per single human dose. In a preferred embodiment, the potency of the composition of the invention is at least 30 IU per single dose. When one-dilution tests are performed, the potency of the test vaccine is demonstrated to be significantly greater than 30 JU per human dose.

General The term "comprising" encompasses "including" as well as "consisting" e.g. a composition "comprising" X may consist exclusively of X or may include something additional eg X --Y. The word "substantially" does not exclude "completely" eg. a composition which is "substantially flee" from Y may he completely free from Y. Where necessary, the word "substantially" may be omitted from the definition of the invention.

The term "about" in relation to a numerical value x means, for example, rI-I 0%.

Unless specifically stated, a process comprising a step of mixing two or more components does not require any specific order of mixing. Thus components can be mixed in any order. Where there are three components then two components can be combined with each other, and then the combination may be combined with the third component, etc. Where an antigen is described as being "adsorbed" to an adjuvant, it is preferred that at least 50% (by weight) of that antigen is adsorbed e.g. 50%, 60%, 70%, 80%, 90%, 95%, 98% or more. It is preferred that diphtheria toxoid and HBsAg are both at least 90% adsorbed, and ideally are totally adsorbed i.e. none is detectable in supernatant after cetrifugation.

DESCRIPTiON OF THE DRAWINGS

Fig. I: Flow chart of a fermentation process according to the invention Fig. 2: Chromatograms of the diphtheria toxin solution before and after anion exchange chromatoaphy Fig. 3: Chromatograms of the diphtheria toxin solution before and after concentrationldiafiltration Fig. 4: Electric focusing gel for samples no. I, 7, 15,41,47 and 55 in comparison to samples prepared by a conventional process in which the crude diphtheria toxin is detoxified prior to purification Fig. 5: Electric focusing gel for samples no. 1,3,9, 15,41,43,49 and 55 Fig. 6: Electric focusing gel for samples no. 5, 25, 45, 11, 51, 17, 37 and 57 Fig. 7: Electric focusing gel for samples no. 7, 27, 47, 13, 53, 19,39 and 59 Fig. 8: Electric focusing gel for samples no. 21, 23, 29, 3!, 33 and 35 in comparison to toxin prior to detoxification buffered at pH7 (lane 2) or pH 8 (lane 9) Fig. 9: Chromatogram of samples with a diphtheria toxin starting concentration of 500 Lf/niL after detoxification with 1% fornialin in the absence of lysine or h the presence of 0.025 M lysine Fig. 10: Chromatogram of samples with a diphtheria toxin starting concentration of 2000 Lf/mL after detoxification with 1% formalin in the absence of lysine or in the presence of 0.025 M lysine Fig. 11: Chromatogram of samples with a diphtheria toxin starting concentration of 5000 Lf/mL after detoxification with 1% formalin in the absence of lysine or in the presence of 0.025 M lysine Fig. 12: Flow chart of a purification and detoxification process according to the invention.

MODES FOR CARRYING OUT THE INVENTION

Example 1: Preparation of dejerrated yeast extract solution PTK yeast extract was purchased from Ohly GmbH (Germany) and deferrated by a process modified from reference I I as summarized in the following paragraphs.

A solution was prepared by dissolving the commercially available PTK yeast extract in water. The yeast extract solution was then heated to 60°C and Na2HPO42H20 and Kl-12P04 was added. The pH of the solution was adjusted to 9.3 by the addition of sodium hydroxide. The solution was further heated to 79°C, and CaCI2 solution was added. Subsequently, the solution was heated to 85°C and incubated for 10 mi Afterward the yeast extract solution was allowed to cool to 25°C over 3 hours.

Any precipitate that had formed was removed by centrifugation. The p11 of the deferrated yeast extract solution was adjusted to 8.4 by the addition of acetic acid. The solution was subjected to ultrafiltration and subsequent sterilization in an autoclave for 90 mm at 134°C. The final composition of the deferrated yeast extract solution is summarized in Table I. Table 1: Composition of the deferrated yeast extract solution Component Amount PTK yeast extract 102.48 g Na2HPO42H10 5.02 g KH2PO4 l.33g CaCI22H20 4.21 g Sodium hydroxide solution 31.10 ml Acetic acid solution (100%) 13.96 nil Water Ad 1000 ml Example 2: Preparation of the fermentation medium In order to prepare the fermentation medium, maltose monohydrate dissolved in water, sodium lactate solution, growth factor solution, water and L-cysteine solution were added to the deferrated yeast extract in the order as listed. In a further step, ammonium Fe(lll) citrate solution and phosphate solution (also in the order as listed) were added. The further addition of calcium chloride solution led to the precipitation of the iron and the formation of an iron-containing gel, which slowly releases iron into the fermentation medium during bacterial growth without inhibiting toxin production. In a final step, the p1-I of the fermentation medium was adjusted to 7.3 by adding 20% acetic acid solution or 10% ammonium solution as needed. The composition of the growth factor solution is provided in Table 2.

Table 2: Composition of the growth factor solution Component Amount MgSO4-7H20 225 g 13-alanine 2.3 g Pimelic acid 150mg Nicotinic acid 4.6 g CnSO45H20 500 mg ZnSO7H2O 500 mg MnCI24H20 240 mg HC125% 2.6 ml Water Ad 1000 ml The final composition of the fermentation medium is shown in Table 3. After all components had been added, the fermentation medium was sterilized in an autoclave for 90 mm at 134°C. The autoclaved fermentalion medium was filtersterilized and stored at 2°C to 10°C.

Table 3: Components of the fermentation medium Component Amount PTK yeast extract 34.38 g Na2HPO42H2O 1684.13 mg K112P04 497.48mg CaCIv2H2O 2.13 g Sodium hydroxide solution 1043 ml Acetic acid solution (100%) 4.69 ml Maltose monohydrate 49.68 g Sodium lactate solution 2.07 ml MgSO4-7H20 1.8 g jI-alanine 18.41 mg Pimelic acid 1.20mg Nicotinic acid 36.83 mg CuSOwSl120 4.00 mg ZnSO47H20 4.00 mg MnCI241120 1.92 mg HC125% 0.70 ml L-cysteine solution 280.19mg Aminonium Fe(l[L) citrate solution 3.23 mg K2HPO43H20 201.48mg Water Ad 1000 ml Example 3: Preparation of crude diphtheria toxin The fermentation medium was inoculated with Corynebacterium diphtheriae from a working seed to prepare a preculture. Both the working seed and the master seed were prepared using the fermentation medium described above.

A fermenter with a total capacity of 300 L was filled with fermentation medium, and the preculture was diluted into the fermentation medium to prepare the main culture. The main culture was incubated at 36°C at 560 rpm for 20 hours. Thereon after incubation was continued at 620 rpm for an additional 24 hours. The fermentation process yielded diphtheria toxin in a concentration of 200 LF/ml to 250 LF/ml.

The culture medium was separated from the bacteria by centrifugation, and the culture supernatant was passed through a filtration cascade starting with a 0.5 jim filter and ending with a 0.2 im filter. Citrate buffer was then added to the resulting crude diphtheria toxin solution and adjusted to a final concentration of 5 mM of citrate. The solution was concentrated by diafiltration against 5 volumes of 5mM citrate pH 6.5 using a regenerated cellulose membrane with a 30 kDa cut-off. This reduced the volume from about 300 L to about 50 L. The retained concentrated diphtheria toxin solution was passed through a 0.2 jim filter. The resulting sterile concentrated diphtheria toxin solution was designated "diphtheria toxin concentrate 1" and was stored until further use.

Prior to purification, a buffer exchange was performed. The diphtheria toxin concentrate I was diafiltered against 5 volumes of 25 mM tris-buffer pH 7.5 using a regenerated cellulose membrane with a 30 kDa cut-off The tris-buffered solution was filtered using Z carbon filtration and passed through a 0.2 pm filter. The resulting sterile, tris-buffered diphtheria toxin solution was designated "diphtheria toxin concentrate 2." A flow chart of the process described in Example 3 is provided in Fig. 1.

Example 4: Fur(fication of the crude diphtheria toxin To further purify the crude diphtheria toxin produced in the fermentation process described in the preceding example, anion exchange chromatography was applied. 50 L fermenter harvests could reproducibly purified using the method described below.

The diphtheria toxin concentrate was loaded onto a Factogel EMD TMAE anion exchange gel matrix column purchased from Merck Chemicals. The purified diphtheria toxin was eluted with 25mM tris/90 mM NaCl buffer pH 7.5. 80% of the protein loaded on the column could be recovered by a simple elution step with the NaCl buffer. The initial volume of 50 1 of crude diphtheria toxin solution was reduced to 10 I purified diphtheria toxin solution. The eluate from the anion exchange column was over 85% pure. A representative ehrornatogram of the diphtheria toxin solution before loading onto and after elution fiom the anion exchange column is shown in Fig. 2.

Subsequently, the eluate was diafiltrated in 0.1 M sodium phosphate p1-I 7.5 to yield a further concentrated and buffered diphtheria toxin solution of greater than 90% purity. A representative chromatogram of the diphtheria toxin solution before and after diafiltration is shown in Fig. 3.

Example 5: Establishing suitable detoxificatia,: conditions The present example describes experiments to determine detoxification conditions that yield an irreversibly detoxified diphtheria toxin (the so called toxoid) that shows no retoxification after 6 weeks storage at 37°C.

The purified diphtheria toxin prepared in Example 4 was dialyzed against PBS at pH 7.0, 7.5 and 8.0. The toxin concentration was determined by turbidity assay and flocculation assay. The results of both assays are summarized in Table 4.

Table 4: Results of turbidity and flocculation assay p11 Turbidity assay [JJ/mLl Flocculation assay ILf/rnL4 7.0 1528 1071 7.5 1564 W71 8.0 3728 2500 A. Establishing suitable formaldehyde and lysine concentrations For each pH, diphtheria toxin, corresponding to 500 Lf/mL was mixed with a defined amount of lM lysine (pH adjusted and sterile filtrated) to giveS ml samples with OM, 0.025M, 0.05M and 0. 1M lysine.

Detoxification was carried out by adding 12.5 p1 (0.25%) formaldehyde (FA) 40% for 2, 3 or 4 days respectively. In total 30 formylation conditions were tested in duplicate (see Table 5).

Table 5: Experimental set-up and sample desianation Lysine concentration pH 7.0 pH 7.5 p14 8.0 Formallu content OM 1 2 21 22 41 42 0.50% 0.025M 3 4 23 24 43 44 0.50% 6 25 26 45 46 0.75% 7 8 27 28 47 48 1.00% 0.05M 9 tO 29 30 49 50 0.50% 11 12 31 32 51 52 0.75% 13 14 33 34 53 54 1.00% O.1M 15 16 35 36 55 56 0.50% 17 18 37 38 57 58 0.75% 19 20 39 40 59 60 1.00% The 60 samples were kept at 37°C without agitation for 6 weeks, subsequently dialysed against IL NaCI solution (8.5 gIL NaCI) with four changes using slide-A-lysers (having a molecular weight cut-off of 10.000) and sterile filtrated. All analytics (see below) were done on this material.

Retoxification Based on the results of a Diphtheria turbidity assay, each sample was diluted with NaCl solution (8.SgIL NaCl) to 50 LfImL (paediatric vaccine) and 3 LfIrnL (adult vaccine), respectively, and stored at 37°C for another 6 weeks. After 3 and 6 weeks, a Vero cell test was carried out to determine the toxicity of the diphtheria toxin preparation.

Vero cell tect To determine the presence of residual diphtheria toxin after detoxification as well as after the retoxification period, a Vero cell test was developed. Vero cells were incubated with different sample dilutions for 72 hours. Subsequently the cell viability was studied microscopically and quantified using an 3-(4,S-dimethylthiazol-2-yI)-2,5-diphenyltetrazolium bromide (MTT) assay. MIT is reduced to purple formazan in living cells. Alternatively, crystal violet was added to the Vero cell culture to detect dead cells. Both tests showed to be very sensitive towards diphtheria toxin. The metabolism of Vero cells was inhibited by less than 0.001 mLfImL toxin.

No toxin could be detected either after detoxification or after 3 and 6 weeks of retoxification conditions.

It can be concluded, that all formylation conditions studied, even those without lysine, gave an irreversible toxoid.

In order to discriminate between the effectiveness of different detoxification conditions several other analytical methods were used.

Amino Acid Analysis No lysine was found in non-hydrolyzed samples No.3, 5, 7, 9, 13, IS, 19 and 47, indicating that the dialysis was very effective. Lysine content after hydrolysis was not determined.

l-IPLC-SEC A size exclusion chromatography (SEC) using TSK 3000 SWXL columns was established to assay the molecular weight distribution of the toxoids. The chromatograms looked fairly similar for all samples with a major monomer peak (83-95%) eluting after approximately 19 mm and a smaller dimer peak (5- 17%)atl7min.

In agreemcnt with the literature the FA treatment lead to only small amounts of diphtheria dimers.

Besides the similarities, subtle differences were found in retention times and the degree of dimerization (see Tables 6 and 7). In general, higher PA concentrations and lower lysine concentralions resulted in lower retention times of the major peak, corresponding to a higher molecular weight of the monomer.

This means that the more FA treatment, the higher the extent of formylation.

Table 6; F[PLC SEC / Retention time of the major peak [mm, in boldl Lysine concentration ph 7.0 pH 7.5 pH 8.0 Formalin content 1 2 21 22 41 42 0.50%

OM

19.65 19.50 19.43 4 23 24 43 44 0.50% 19.37 19.36 19.37 6 25 26 45 46 0.75% 0.025M 19.23 19.32 19.23 3 27 28 47 48 1.00% 19.47 19.08 19.12 10 29 30 49 50 0.50% 19.40 19.33 19.40 11 12 3! 32 51 52 0.75% 0.05M 19.35 19.27 19.37 13 14 33 34 53 54 1.00% 19.13 19.20 19.22 16 35 36 55 56 0.50% 19.72 19.67 19.62 iT 18 37 38 57 58 0.75% 0.IM 19.65 19.50 19.58 19 20 39 40 59 60 1.00% 19.47 19.37 19.52 Table 7: I-IPLC SEC I Dearee of djnierization {% in hold] Lysine concentration pH 7,0 PH 7.5 pH 8.0 Formalin content 1 2 21 22 41 42 0.50%

OM

12.2 13.6 13.0 3 4 23 24 43 44 0.50% 9.4 11.0 9.2 6 25 26 45 46 0,75% 0.025M 9.8 8.7 7.7 7 8 27 28 47 48 1.00% 8.6 7.6 7.9 9 10 29 30 49 50 0.50% 10.2 11.0 7.2 11 12 31 32 51 52 0.75% 0.05M 9.2 5.7 13 14 33 34 53 54 1.00% 8.9 9.3 4.4 16 35 36 55 56 0.50% 10.7 16.6 9.8 17 18 37 38 57 58 0.75% 0.IM 9.4 13.5 9.4 19 20 39 40 59 60 1.00% 9.2 9.5 7.6 The influence of lysine was more pronounced than that of FA, due to the broader variation of this parameter. In the studied range, the pH seemed to have no influence.

Samples devoid of lysine did not behave according to the general trends. They showed longer elution times and higher amounts of dimers, compared to those with O.025M lysine. In the presence of lysine, FA preferably generates N-hydroxymethylated Lysine. This intermediate seems to have a better reactivity with the toxin than FA alone, explaining for the better formylation and the reduced dimerization.

Looking at the samples No.2, 3, 7, 15 and 47 on a Superdex 200 HR 10/30 column gave the same trends.

Formylation worked best with 1% FA 40% and 0.025M lysine. 1FF

Isoeleetric focusing (lEE) was employed to evaluate the extent of FA treatment. Since FA reacts with positive charged amino groups, acidic groups become more prominent. As a result, the p1 drops.

Selected samples No. 1, 7, 15,41,47 and 55 were tested (see Fig. 4). Since a fairly big difference in their chromatographic behaviour became obvious, all 30 samples were studied for their p1 (see Fig. 5-8). The results of these studies are summarized in Table 8.

TableS: p1 range of various diphtheria toxoids

Sample description pI range

Toxoids from conventional production 4.8 -3.5 New detoxification, without lysinc 4.8 -4.0 New detoxification, with O.025M lysine 5.0-4.1 New detoxification, with 0.05M lysine 5.2-4.3 New detoxification, with 0. IM lysine 5.4 -4.4 CRIvI, failing the potency test 5.4 -4.6 In agreement with theoretical considerations, the more PA treatment was applied (as achieved by high FA concentrations and low lysine concentrations), the lower was the p1. Again the influence of lysine was more pronounced than that of FA and no pH dependency was found.

All samples containing none or only 0.0251vi lysine showed a pi range comparable to that of the loxoids from conventional production during which the crude diphtheria toxin is detoxified first before the toxoid is purified. Only their range was narrower, probably reflecting the higher purity of the startthg material.

Higher lysine concentrations, however, lead to a lower degree of forniylation. The p1 pattern of these samples resembled that of a failed CRM sample, raising the assumption that samples with a high p1 might not pass the potency test.

Conclusion

In the studied range, all diphtheria toxin samples were detoxified and did not show retoxification after 6 weeks storage at 3 7°C. Both HPLC and 1FF studies agreed that formylation worked best with 1% FA 40% and 0.025M lysine.

Even though samples without lysine showed to be equally well detoxified, a small amount of lysine seems to be favorable for achieving only low levels of dirnerization.

B. Esiablishing suitable diphtheria toxin concentration and detoxWcation lime Both detoxification at higher toxin concentrations (500-5000 LI) and the detoxification time (14, 28 and 42 days) were investigated. Purified diphtheria toxin concentrate (12,500 LF/mL, 20 mrnollL) was diluted in 0.1 mol/L phosphate buffer and sterilized by filtration. Final toxin concentration and sample composition are shown in Table 9.

Table 9: Comnosition of samples 1-12 Sample No. Diphtheria-toxin Lysine Formalin ___________________ lLf/inLl FM] lOb] 1 500 0 1 2 2000 0 3 5000 0 4 500 0.025 1000 0.025 1 6 2000 0.025 7 3000 0.025 8 5000 0.025 1 9 2000 0.025 2 2000 0.050 2 11 2000 0.025 4 12 2000 0.100 4 For each sample, a volume of 100 mT was prepared. 2,4 and 6 weeks after addition of formaldehyde, S ml. of each sample were removed, dialysed (except for determination of the free formaldehyde concentration) and analysed.

The results of the turbidity test after 12, 28 and 42 days are shown in Table 10.

Table 10: RCSLLItS of the turbidity test after dialysis Sample No. 1hnltdVrJw 14 days 28 days 1 42 days ___________ ILf/mL] ILl/mU lLf/mLl [Lf/mLl 500 216 276 244 2 2000 1454 1354 1196 3 5000 4493 3014 3058 4 500 492 478 374 1000 1097 1066 946 6 2000 2236 2016 2035 7 3000 3089 3170 2860 8 5000 5158 5980 5736 9 2000 2080 1939 2285 2000 2028 2184 2215 11 2000 1830 1716 1716 12 2000 2010 1792 1980 The samples that had been detoxified with formaldehyde and 1ysne showed no loss of activity (Lf7mL) even after 42 days. Samples without lysinc showed lower Lf/mL values than comparable samples with lysine. The biggest decrease in activity was seen after 14 days. After 28 and 42 days the activity decreased only slightly.

All samples were tested for residual toxicity in the Vero cell assay described above and were compared with purified toxin and a standard. The samples gave ED50 values between 100 and 300 Lf/m[ which are io -106 times higher than the values for the toxins. Diphtheria toxoid produced by existing processes give values between 50 -500 Lf/mL. No time dependency of the detoxification process was observed. It seems that detoxification was complete after 14 days. The results of the Vero cell assay for samples 1-12 are summarized in Table II Table II: Results of the toxicity assay using Vero cells I4days 28days 42days 50% value 50% value 50% value __________ ILf/mLl ILVmLI ILffmLl 1 167.20 146.74 238.44 2 187.19 192.86 174.16 3 391.50 176.66 260.2 4 138.66 122.95 135.03 203.20 165.04 200.06 6 206.27 140.82 241.65 7 231.74 200.30 259.97 8 217.26 196.18 308.04 9 149.81 184.65 306.23 128.67 167.13 231.52 II 164.14 151.70 239.53 12 116.40 128.29 190.53 Standard 0.00031 0.00017 0.00071 Standard 0.00045 0.00162 0.00041 Toxin 0.00055 0.00665 0.01234 Toxin 0.00168 0.00682 0.00046 This finding is also supported by the results obtained after determination office formaldehyde. After 14 days of detoxification all samples showed a lower free formaldehyde concentration compared to the initial concentration, but no further formaldehyde was consumed over the following 30 days. The results of the assay for determining the free formaldehyde concentration of samples 1-12 before dialysis are summarized in Table 12.

Table 12: Free formaldehyde concentration Theoretical Starting 14 days 28 days 42 days Value [gil] [WI] [WI] 3.8 3.6 3,0 3.6 2 3.8 3.5 2.9 3.4 3 3.8 3.2 2.7 3.3 4 3.8 2.4 1.9 2.0 3.8 2.3 1.9 1.9 6 3.8 2.2 1.9 1.9 7 3.8 2.4 1.8 1.8 8 3.8 2.0 1.6 1.7 9 7.6 4.8 4.2 4.4 7.6 3.2 3.1 2.6 11 15,2 11.9 10.7 11.7 12 15.2 7.3 6.2 6.3 Analysis of the samples by SEC also showed no further reaction after 14 days detoxification (see Fig. 9- 11). The SEC analysis clearly uncovered the influence of higher toxin concentrations during detoxification in the presence and the absence of lysine. The higher the toxin concentration was, the higher was the fraction of dimers and multirners (see Fig. 9-11). Dinier and multinier formation was observed in the presence and absence of lysine. however, lysine significantly inhibited the cross-linking reaction resulting in the formation of far less dimmers than in its absence (33% dimers in absence of lysine vs. 10% in the presence of 0.025mM lysine at 2000 LF/ml; see Table 11, samples 2 and 6). The percentage of dimers in each ofsamplesl-12 is shown in Table 13.

Table 13: Percentage of dimers 14 days 28 days 42 days Dimer [%] Dimer rio] Dimer [%] 1 9 10 12 2 28 32 33 3 51 56 58 4 2 2 2 5 5 5 6 10 10 10 7 14 14 IS 8 23 23 24 9 9 9 10 9 8 8 11 9 10 10 12 9 9 9 Connecting a light scattering detector with the SEC to look at the molecular weight of the separated peaks confirmed that the major peak was the monomer with a molecular weight of ca. 60 kDa. The minor peaks were dimers with 120 kDa, and in some samples, trimers with 180 kDa or even multimers could be detected.

Example 6: Potency of the diphtheria toxoid prepared by the new processes Potency studies were carried out in accordance with the requirements of the European Pharmacopoeia (1997, third edition, Council of Europe, Strasbourg, France, Assay of diphtheria vaccine (adsorbed), pp. 113-115).

The crude diphtheria toxin was prepared as described in the preceding examples. To further purify and detoxify the crude diphtheria toxin, the purification process described in Example 4 was combined with the optimized detoxification process described in Example 5 resulting in the combined process shown in Pig. 12.

The diphtheria toxin was purified by anion exchange chromatography as described above. The toxin concentration of the eluate was adjusted to 5000 Lf/mL. The concentrated diphtheria toxin solution was detoxified in phosphate buffer pH 7.5 by addition of PA (40% solution) to a final concentration of 1% in the presence of 0.025M lysinc (final concentration) as described in Example 5. The resulting diphtheria toxoid was diluted and subsequently adsorbed to aluminium hydroxide. The composition of the final vaccine formulations are shown in Table 14.

Potency of the vaccine formulations was tested. Pediatric vaccines pass the potency test when the lower confidential limit is at least 30 l.U./dose. The results of the potency studies are summarized in Table 14.

Table 14: Comnosition of the vaccine formulations and potency test data Sample Diphtheria toxin I Tetanus toxin WV Al(OH)3 Osniolality pH Potency 11 cI.-.1 1 I ii fI,I 1 1,,-..,,/,'..T 1 L' [mosm/kg} [I.E/dose] D vaccine 50 --3.24 266 6.20 39 pass (pacdiatric) Dvaccine 50 --3.15 267 6.40 48pass (paediatric) Dvaccine 50 --3.15 267 6,40 35pass (paediatrie) Td-IPV (adult) 4 10 80/16/64 1.95 290 6.86 5 pass Dt vaccine 34 20 -3.28 271 6.37 33 pass (paediatric) DT concentrate* 167 67 -7.36 314 6.30 39 pass tfor the potency test, the concentrate was diluted to 50 LflmL of diphtheria toxin and 30 Lf/mL of tetanus toxin Example 7: Analysis of diphtheria toxoid composition A composition comprising diphtheria toxoid prepared according to the process outline in Fig. 12 was stored at +2-8°C for 0, 6 and 12 months. No preservatives were added to the composition during the entire production process. After each time point, aliquots of the sample were used for potency testing, purity analysis, flocculation assay, HPLC analytics, pH measurement, toxicity and sterility testing and chemical analysis of free lysine, formaldehyde, sodium chloride, sulphate and phosphate content. The results are summarized in Table 1 5, At all time points, the composition widely exceeded purity requirements and potency requirements.

Likewise, the residual formaldehyde concentration was below the allowable limit of 0.2 mg/mI.

Table 15: Stability data and Composition Storage Period (months) Test Items Requirements 0 6 12 Potency Diphtheria e.p. (lU/mI) 1.1. >2.0 10 10 l.l-u.l ____________________________ 6-15 8-14 ___________ Nitrogen Antigenic Purity (LThng N) >1 500 2710 2740 2128 Nitrogen Antigenic Purity (Lf'mg N)/new > 1500 2865 2825 2279 method ____________________________ ___________ __________ ___________ Lfcontent(L9 -10000 10000 8000 Nitrogen first test (mg/mI) Calculation from Lf/mgN and 3.69 3,65 336 _________________________________________ If ___________ __________ ___________ Nitrogen second test (mg/ml)/new method Calculation from LE'mgN and 3.49 3.54 3.51 ___________________________________ Lf _________ _________ _________ Lysin content (nmol/ml) <=550 555 n.t 876 HPLC analytic -Meets Meets Meets _____________________________________________ _______________________________ spec spec spec p11 7.2-7.8 7.54 7.7 7.7 Sodium chloride (mg/mi) 8-9 7.94 8.0 7.95 Formaldehyde(mg/ml) <=0.2 0.100 0.143 0.163 Phosphat (pg/mI) <=15 <=0.10 0.10 <0.l0 Sutfat Not detectable Meets Meets Meets _____________________________________________ _______________________________ spec spec spec Abnormal toxicity negative test Acc.to Ph. Eur Meets Meets Meets _____________________________________________ _______________________________ spec spec spec Toxicity (survivals of 5) 5 (no toxicity) 5 5 5 Sterility test Ace, to Ph. Eur Meets Meets Meets _____________________________________________ _______________________________ spec spec spec e.p. = estimated potency meets spec = meets specification n.t.-=not tested L.l lower limit-upper limit * = Potency is determined as a praevaccine composition like adsorbed diphtheria vaccine for adults It will be understood that the invention has been described by way of example only and modifications may be made whilst remaining within the scope and spirit of the invention.

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EMBODIMENTS

1. A fermentation medium suitable for culturing a strain of Corynebacterium diphiheriac to produce diphtheria toxin or a derivative thereof, wherein the medium is free of animal-derived components and comprises: (i) water; (ii) a nitrogen source; (iii) a carbon source; and (iv) an iron supplement; wherein a culture of Cotynebacterium diphtheriae in at least 100 L of the fermentation medium yields at least 140 LtYmL of the diphtheria toxin or the derivative.

2. The fermentation medium of embodiment I, wherein the Corynebacteriurn diphtheriae culture yields at least 200 LIJmL, optionally 250 Lf/mL, of the diphtheria toxin or the derivative thereof 3. The fermentation medium of embodiment I or 2, wherein the nitrogen source is a yeast extract, said yeast extract being deferrated, and wherein the carbon source is a disaccharide, said disaccharide being present at concentration of at least 0.08 M. 4. The fermentation medium of embodiment 3, wherein the concentration of the disaccharide is between 0.08 M and 0.16 M. 5. The fermentation medium of embodiment 1 or 2, wherein the nitrogen source is a yeast extract, said yeast extract being deferrated, and wherein the iron supplement is a salt of Fe(II1).

6. The fermentation medium of embodiment I or 2, wherein the nitrogen source is a low-mannan yeast extract, optionally wherein said low-mannan yeast extract is deferrated.

7. The fermentation medium of embodiment 1 or 2, wherein the nitrogen source is a yeast extract, said yeast extract being free of components with a molecular weight greater than 30 kDa, and wherein the iron supplement is salt of Fe(l1) or Fe(I11) at a concentration between 1.5 1tM and 30 M. 8. The fermentation medium of embodiment 3 or 6, wherein the iron supplement is a salt of Fe(II) or Fe(1l1).

9. The fermentation medium of embodiment 3, 5 or 7, wherein the yeast extract has a low mannan content.

10. The fermentation medium of embodiment 3, 5 or 6, wherein the yeast extract is free of components with a molecular weight greater than 30 kDa.

II. A process for preparing the fermentation medium according to embodiment 1, whereth the process comprises adding to water: a nitrogen source; a carbon source; and an iron supplement.

12. The process of embodiment II, wherein the nitrogen source is a yeast extract.

13. The process of embodiment 12, wherein the yeast extract is low in matmans.

14. The process of embodiment 12 or 13, comprising ultrafiltrating the yeast extract using a membrane with a molecular weight cut-off greater than 30 kDa.

15. The process of any one of embodiment 12-14, comprising deferrating the yeast extract. 5!

16. The process of any one of embodiments 11-15, wherein the carbon source is a disaccharide, said disaccharide being present at a concentration of at least 0.08 M. 17. The process of embodiment 16, wherein the disaccharide is prcsent at a concentration between 0.08 M and 0. 16 M, 18. The process of any one of embodiments 11-17, wherein the iron supplement is a salt of FeIjlT).

19. The process of embodiment 18, comprising adding the salt of Fe(11I) in combination with phosphate and a calcium salt to promote formation of a slow-release formulation of iron.

20. The process of any one of embodiments 11-17, wherein the iron supplement is a salt of Fe(II) or Fe(III) at final concentration between 1.5 gM and 30 riM.

21. A process for producing a diphtheria toxin or derivative thereof for the preparation of a vaccine for human use comprising: (i) preparing a culture of a strain of Corynebacleriurn dphtheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentation medium comprising: a nitrogen source; at least 0.08 M of a carbon source; 1.5gM -30gM soluble Fe2LIFe3; phosphorus; and growth factors, but being free from animal-derived components; (ii) growing the culture in aerobic conditions to a concentration of at least 140 Lf/mL of the diphtheria toxin or the derivative in the fermentation medium; and (;;; +1w. ci; n1,,hnr' t,-.,-..,. tk.. rlnrh,nth,n frnn, tI-.. £ ,r.+,,tr.n n,rBi,nm n,t,nr,n tbn separation step comprises a centrifugation step and a filtration step.

22. The process of embodiment 21, wherein the concentration is at least 200 Lf'mL of the diphtheria toxin or the derivative.

23. The process of embodiment 21, wherein the concentration is at least 250 LtlmL of the diphtheria toxin or the derivative.

24. The process of any one of embodiments 21-23, wherein the growth factors are selected from magnesium, copper, zinc, manganese, pimelic acid, nicotinic acid and li-alanine.

25. The process of any one of embodiments 21-24, further comprising adding formaldehyde to the purified diphtheria toxin or the derivative and incubating it to obtain a diphtheria toxoid.

26. The process of embodiment 25. further comprising adding an adjuvant, a carrier and/or an excipient to the diphtheria toxoid.

27. A process for preparing a combination vaccine for human use comprising: (i) preparing a culture of a strain of Corynebacterium dip htheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentation medium comprising: a nitrogen source; at least 0.08 M of a carbon source; 2+ 3+ 1.5 gM -30gM soluble Fe /Fe phosphorus; and giowtli factors, but being free from animal-derived components; (ii) growing the culture in aerobic conditions to a concentration of at [east 140 LflmL of the diphtheria toxin or the derivative in the fermentation medium; (iii) separating the diphtheria toxin or the derivative from the fermentation medium, wherein the separation step comprises a centrifugation step and a filtration step; (iv) adding formaldehyde to the diphtheria toxin or the derivative obtained in step (iii) to obtain a diphtheria toxoid; and (v) mixing the diphtheria toxoid with at least one additional protective antigen from a pathogen other than Corynebaclerium diphtheriae to obtain the combination vaccine.

28. A process for preparing a diphtheria toxoid for the preparation of a vaccine for human use comprising: (i) growing a strain of Corynebacterium diphtheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentaLion medium suitable for growing a Cotynebacteriurn diphtheriae culture to yield at least 140 Lf/mL of a diphtheria toxin or a derivative thereof; (ii) separating the diphtheria toxin or the derivative from the fermentation medium to obtain a diphtheria toxin solution; (iii) preparing a diphtheria toxin concentrate from the diphtheria toxin solution, wherein the concentration of the diphtheria toxin or the derivative in the concentrate is at least 20-fold higher than the concentration of the diphtheria toxin or the derivative in the fermentation medium at the end of step (i); (iv) detoxif'ing the diphtheria toxin concentrate to prepare diphtheria toxoid.

29. A process for producing a diphtheria toxoid for the preparation of a vaccine for human use comprising: (i) growing a strain of Corynebacteriwn diphtheriae expressing a diphtheria toxin or a derivative thereof in at least 100 L of a fermentation medium that is free from animal-derived components, optionally wherein the fermentation medium comprises yeast extract; (ii) purifying the diphtheria toxin or derivative from the fermentation medium to obtain a purified diphtheria toxin or derivative, wherein the purified toxin or derivative is at least 85°/b pure and/or has a purity of at least 1500 Lf/mg nitrogen; (iii) adding formaldehyde to the purified diphtheria toxin or derivative; and (iv) incubating the purified diphtheria toxin or derivative from step (iii) to obtain the diphtheria toxoid.

30. A process for producing a diphtheria toxoid for the preparation of a vaccine for human usc comprising: (i) preparing a solution of a diphtheria toxin or a derivative thereof at a concentration of at least 2000 Lf/mL; (H) adding to the solution (a) an amide at a final concentration of no more than 0.025 M and (b) formaldehyde at a final concentration in the range of 0.75-1%; and (iii) incubating the solution from step (H) to obtain the diphtheria toxoid.

31. The process of embodiment 30, wherein the amide is glycine or lysine.

32. The process of embodiment 30 or embodiment 31, wherein the solution of diphtheria toxin is prepared by a process comprising: (1) growing a culture of a strain of Corynehacterium diphtheriae expressing a diphtheria toxin in a fermentation medium free of animal-derived components; (2) purifying the diphtheria toxin from the fermentation medium to obtain a diphtheria toxin solution; and (3) adjusting the concentration of diphtheria toxin in the diphtheria toxin solution to at least 2000 LfYmL.

33. A diphtheria toxoid for use in human vaccination, obtainable by the process of embodiment 29 or 32, wherein the diphtheria toxoid is cross-linked by formaldehyde to at least one component of the fermentation medium.

34. A diphtheria toxoid for use in human vaccination, obtainable by a process comprising: growing a strain of Corynehacteriwn diphtheriae that expresses a diphtheria toxin in a fermentation medium free of animal-derived components; separating the diphtheria toxin from the fermentation medium; and incubating the diphtheria toxin in the presence of formaldehyde to yield the diphtheria toxoid, wherein the diphtheria toxoid is cross-linked by formaldehyde to at least one component of the fermentation medium.

35. A composition suitable for human vaccination, comprising a diphtheria toxoid purified from Corynebacterium diphtheriae grown in a culture medium free from animal-derived components and having a potency of at least 60 lU/mi.

36. The composition of embodiment 35, wherein the composition includes monomeric and dimeric diphtheria toxoid, and the monomer:dimer ratio of the diphtheria toxoid in the range of 3:1 to 8:1 and wherein the diphtheria toxoid has an isoelectric point in the range of 4.0 to 5.ft 37. A composition of embodiment 36, wherein at least 70% of the diphtheria toxoid is in monomeric form.

38. A composition suitable for human vaccination, comprising a formaldehyde-linked diphtheria toxoid with an isoelectric point in the range of 4.0 to 5.0 and which is free from formaldehyde-linked animal-derived components, wherein at least 70% of the toxoid is in monomeric form.

39. The composition of any one of embodiments 35 to 38, comprising a protective antigen from at least one pathogen other than Corynebacteriwn diphtheriae.

40. A composition suitable for human vaccination, comprising (i) a formaldehyde-linked diphtheria toxoid which is free from formaldehyde-linked animal-derived components and (ii) a protective antigen from at least one pathogen other than Cotyne bacterium diphtheriae.

41. The composition of embodiment 40, wherein the diphtheria toxoid has a potency of at least 60 lIJ/ml.

42. The composition of any one of embodiments 39 to 41, wherein the non-diphtheria protective antigen is selected from hepatitis B virus surface antigen (1-iBsAg), tetanus toxoid, a pertussis antigen, a conjugated H.influenzae type B capsular saceharide, a conjugated N.meningitidis capsular saccharide, a conjugated S.pneumoniae capsular saccharide, and/or an inactivated poliovirus.

43. The composition of embodiment 42, wherein the HBsAg is free from animal-derived components.

44. The composition of embodiment 42 or embodiment 43, wherein the H.influenzae type B capsular saccharide is free from animal-derived components.

45. The composition of any one of embodiments 42 to 44, wherein the Nmeningitidis capsular saecharide is free from animal-derived components.

46. The composition of any of embodiments 42 to 45, wherein the composition is composed of: D, T, HBsAg; D, T, Pw, 1-IBsAg; D, T, Pw, 1-IBsAg, Hib; D, T, Pw, HBsAg, Hib, MenA, MenC; D, T, Pw, HBsAg, Hib, MenA, MenC, MenWl35; D, T, Pw, 1-IBsAg, Hib, MenA, MenC, MenY; D, I, Pw, HBsAg, Hib, MenA, MenC, MenW 135, MenY; D, T, Pa, HBsAg; D, T, Pa, Jil3sAg, Hib; D, T, Pa, 1-IBsAg, poliovirus; D, T, Pa, HBsAg, poliovirus, Hib; D, T, Pa, HBsAg, poliovinis, Hib, MenC; D, T, Pa, 1 IBsAg, poliovirus, I-jib, MenC, MenA; D, T, Pa, HBsAg, poliovirus, Hib, MenC, MenY; D, T, Pa, HBsAg, poliovirus, 1-lib, MenC, MenWl35; or D, T, Pa, HBsAg, poliovirus, Hib, MenC, MenA, MenWl35, MenY.

47. A composition for use in preparing a human vaccine, comprising (I) between 100-250 Ltiml diphtheria toxoid which is free from formaldehydc-crosslinked animal-derived components, and (ii) between 40-100 Lf/ml tetanus toxoid; wherein the ratio of diphtheria toxoid to tetanus toxoid in the composition is between 2:1 and 3:1.

48. The composition of embodiment 47, comprising no antigens except diphtheria toxoid and tetanus toxoid.

49. A process for preparing a human vaccine, comprising mixing the composition of embodiment 47 or embodiment 48 with at least one further antigen-containing composition.

50. The process of embodiment 49, wherein the human vaccine comprises between 20-30 Lf/ml diphtheria toxoid and between 5-15 Lf!ml tetanus toxoid.

51. A composition suitable for human vaccination, comprising a diphtheria toxoid which is free from formaldchyde-crosslinked animal-derived components and which is adsorbed to an insoluble aluminium salt adjuvant (e.g. aluminium hydroxide).

52. A diphtheria toxin obtainable by the process of any one of embodiments 21 to 24 or embodiment 28.

53. A diphtheria toxoid obtainable by the process of embodiment 25 or any one of embodiments 29-34.

54. A diphtheria toxoid prepared from diphtheria toxin produced by a Corynebacterium diphtheriae bacterium grown in a fermentation medium which is free from animal-derived components, wherein the toxoid is erosslinked to medium components.

55. A composition suitable for human vaccination, comprising the diphtheria toxoid of embodiment 53 or 54.

Claims

<claim-text>Claims 1. A process for preparing a diphtheria toxoid comprising the steps of (i) growing a strain of Con'nebactej-iu,n thplithenae expressing a diphtheria toxin in a fermentation medium, (ii) separating the diphtheria toxin from the fermentation medium to obtain a diphtheria toxin solution, (iii) preparing a diphtheria toxin concentrate from the diphtheria toxin solution with a diphtheria toxin concentration of at least 2000 LfmL, (iv) adding to the concentrate an amino acid and formaldehyde, and (v) incubating the concentrate in the presence of the amino acid and formaldehyde to obtain the diphtheria toxoid.</claim-text> <claim-text>2. The process of claim 1, further comprising a step of concentrating the diphtheria toxoid for storage.</claim-text> <claim-text>3. The process of claim 2, wherein the concentration of diphtheria toxoid is at least 5,000 Lf/nil.r 4. A process for preparing a diphtheria toxoid comprising: (i) growing a strain of Cotynebacteriwn diphtheriae expressing a diphtheria toxin in a fermentation medium, C preferably at a volume of at least 100 litres and/or to provide a yield of at least I 4OLf/ml CO of toxin/derivative; (ii) separating the diphtheria toxin from the fermentation medium to obtain a diphtheria toxin solution; (iii) preparing a diphtheria toxin concentrate from the diphtheria toxin solution, wherein the concentration of the diphtheria toxin or the derivative in the concentrate is at least 20-fold higher than the concentration of the diphtheria toxin or the derivative either in the fermentation medium obtained at the end of step (i) or in the toxin solution obtained at the end of step (ii); (iv) adding to the concentrate an amino acid and formaldehyde, and incubating the concentrate from step (iv) to obtain the diphtheria toxoid.5. The process of claim 4, wherein the concentration of the diphtheria toxin or the derivative in the concentrate in step (iii) is between 20-fold and 36-fold higher than the concentration of the diphtheria toxin or the derivative in the fermentation medium.6. The process of any one of the preceding claims, wherein the concentration of the amino acid added for detoxification is no more than 0.1 M. 7. The process of any of the preceding claims, wherein the concentration of formaldehyde used for detoxificafion is in the range of 0.5% and 1%.8. The process of any one of the preceding claims, wherein the fermentation medium is free from animal-derived components and comprises a nitrogen source, a carbon source, an iron supplement, phosphorus, and growth factors.9. A process for producing a diphtheria toxoid for the preparation of a vaccine for human use comprising (0 growing a sfrain of Coiynebacteriuin diphtheriae expressing a diphtheria toxin in a fermentation medium that is free of animal-derivcd components, optionally wherein the fermentation medium comprises yeast extract, (ii) punfiuing thc diphtheria toxin from the fermentation medium to obtain a purified diphtheria toxin having a purity of at least 1500 Lf/mg nilrogen, (iii) adding formaldehyde to the purified diphtheria toxin, and (iv) incubating the purified diphtheria toxin from step (iii) to obtain C') the diphtheria toxoid. rC') 10. A diphtheria toxoid obtainable by the process of any one of claims 1-9.CQ 11. A composition suitable for human vaccination, comprising the diphtheria toxoid of claim 10.12. A composition suitable as a vaccine for human use comprising a diphtheria toxoid free of fonnaldehyde-crosslinked animal-derived components, wherein said composition has a potency of at least 30 IU per unit dose.</claim-text>