WO1997023503A1 - Vaccine component - Google Patents

Vaccine component Download PDF

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Publication number
WO1997023503A1
WO1997023503A1 PCT/GB1996/003249 GB9603249W WO9723503A1 WO 1997023503 A1 WO1997023503 A1 WO 1997023503A1 GB 9603249 W GB9603249 W GB 9603249W WO 9723503 A1 WO9723503 A1 WO 9723503A1
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WIPO (PCT)
Prior art keywords
protein
aeromonas
vaccine
composition
fish
Prior art date
Application number
PCT/GB1996/003249
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French (fr)
Inventor
Thomas Henry Birkbeck
Original Assignee
Scottish Salmon Growers Association
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Publication date
Application filed by Scottish Salmon Growers Association filed Critical Scottish Salmon Growers Association
Priority to AU12054/97A priority Critical patent/AU1205497A/en
Publication of WO1997023503A1 publication Critical patent/WO1997023503A1/en

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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07KPEPTIDES
    • C07K14/00Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof
    • C07K14/195Peptides having more than 20 amino acids; Gastrins; Somatostatins; Melanotropins; Derivatives thereof from bacteria
    • CCHEMISTRY; METALLURGY
    • C12BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12NMICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N1/00Microorganisms, e.g. protozoa; Compositions thereof; Processes of propagating, maintaining or preserving microorganisms or compositions thereof; Processes of preparing or isolating a composition containing a microorganism; Culture media therefor
    • C12N1/20Bacteria; Culture media therefor
    • C12N1/205Bacterial isolates
    • AHUMAN NECESSITIES
    • A61MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61KPREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K39/00Medicinal preparations containing antigens or antibodies
    • CCHEMISTRY; METALLURGY
    • C12BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12RINDEXING SCHEME ASSOCIATED WITH SUBCLASSES C12C - C12Q, RELATING TO MICROORGANISMS
    • C12R2001/00Microorganisms ; Processes using microorganisms
    • C12R2001/01Bacteria or Actinomycetales ; using bacteria or Actinomycetales

Definitions

  • the present invention relates to a vaccine component.
  • the present invention relates to an immunogenic component expressed by microorganisms and to vaccines containing such a component.
  • the present invention relates to an immunogenic component obtainable from an Aeromonas organism and to a vaccine composition comprising the component and a vaccine, especially a vaccine against furunculosis.
  • the vaccine composition of the present invention is useful for administration to animals, especially fish.
  • Furunculosis is a significant disease that can infect many species of fish, examples of which include all species of salmon, rainbow trout, brook trout, brown trout, carp, goldfish and wrasse.
  • furunculosis is caused by the bacterium Aeromonas salmonicida.
  • the present invention seeks to provide a vaccine component that can enhance the effectiveness of a vaccine, especially a vaccine against furunculosis.
  • a non-haemolytic protein having cellular immunosuppressive activity but no glycerophospholipid cholesteryl acyl transferase activity, wherein the protein is obtainable from an Aeromonas organism and has the following characteristics:
  • (iii) is cytotoxic to about 10 5 lymphocytes at levels of about 200 ng; and (iv) is cytotoxic to about 10 5 AS2 tissue culture cells at levels of about 200 ng.
  • composition comprising a vaccine and the protein according to the present invention, and optionally a suitable carrier, excipient or diluent.
  • Aeromonas salmonicida strain S9 Aeromonas salmonicida strain S9
  • Aeromonas salmonicida strain S21 Aeromonas salmonicida strain S21
  • a protein according to the present invention in the manufacture of a vaccine composition for immunising an animal, preferably a vertebrate animal.
  • a protein according to the present invention to suppress the cellular immune response in an animal, preferably a vertebrate animal, preferably when the protein is present in a vaccine composition.
  • a eighth aspect of the present invention there is provided the use of the protein according to the present invention in a vaccine composition to enhance the resistance to fish to furunculosis.
  • a ninth aspect of the present invention there is provided a method for enhancing the resistance of fish to furunculosis, wherein the protein according to the present invention is administered to fish.
  • the present invention relates to a hitherto unknown immunogenic protein produced by Aeromonas organisms.
  • the immunogenic protein according to the present invention is sometimes referred to as the Aeromonas Cellular Immunosuppressive Factor, or Aeromonas CIF for short.
  • the protein is obtainable from Aeromonas salmonicida.
  • the protein is purified under conditions wherein the protein is stabilised.
  • the protein is purified by use of a species that is capable of stabilising the protein.
  • the species is a detergent, preferably a detergent that forms two phases at an elevated temperature.
  • the protein is stored in an environment that prevents or hinders proteolytic degradation thereof.
  • the protein has been stored before use at low temperature, for example at about 4°C.
  • the protein is obtainable from Aeromonas salmonicida strain NCIMB 40736 or NCIMB 40737.
  • the vaccine is a vaccine for a fish.
  • the animal is a fish.
  • the fish is a Salmonid.
  • the Salmonid is salmon, preferably Atlantic salmon.
  • the vaccine is a vaccine for immunising against furunculosis.
  • the furunculosis is caused by Aeromonas salmonicida.
  • the vaccine composition is suitable for oral administration to the animal.
  • the protein of the present invention is present in an amount of from about 0.0008 %w/v to about 0.003 %w/v, preferably about 0.0015 %w/v, in the vaccine composition.
  • the protein of the invention is present in the composition in an amount of at least 0.001% by weight of the composition.
  • Aeromonas CIF can enhance the immunising effect of vaccines for animals, in particular those vaccines used for fish, especially vaccines used for immunising against furunculosis.
  • the adaptive immune response of vertebrates can involve both humoral and cellular responses to the administration of foreign antigens.
  • the humoral response involves the production of antibodies whereas the cellular response, or cell-mediated immunity, involves stimulation of T lymphocytes.
  • the protein of the present invention is advantageous because it is non-haemolytic and is capable exhibiting a cellular immunosuppressive activity.
  • the present invention is particularly advantageous for enhancing the immunising effect of a vaccine for administration to salmon for immunising the salmon against furunculosis.
  • a further advantage of the protein of the present invention is that it can enhance the effect of a vaccine for immunising other animals against furunculosis as well enhancing the effect of other vaccines for immunising salmon or other animals.
  • the protein of the present invention is capable of enhancing vaccines against vibriosis (caused by Vibrio anguillarum), Hitra disease or cold-water vibriosis (Vibrio salmonicida), enteric redmouth ( Yersinia rucker ⁇ ), salmonid rickettsial septicaemia (Piscirickettsia salmonis - which is a problem at present in Chile) and viral diseases such as infectious pancreatic necrosis (IPN), infectious haematopoietic necrosis (IHN), viral haemorrhagic septicaemia (VHS), pancreas disease (PD) and plasmacytoid leukaemia.
  • Vibrio anguillarum Vibrio anguillarum
  • Hitra disease or cold-water vibriosis Vibrio salmonicida
  • enteric redmouth Yersinia rucker ⁇
  • salmonid rickettsial septicaemia Pierid ricketts
  • Aeromonas Cellular Immunosuppressive Factor or "Aeromonas CIF” as used herein do not necessarily mean that the protein must be obtained from Aeromonas as the protein may be obtained synthetically or by use of recombinant DNA techniques wherein the gene coding for the protein can be expressed in a suitable host organism, such as E.coli. Alternatively, the protein can be prepared synthetically.
  • non-haemolytic and “not haemolytic” as used herein mean that at most the protein is capable of exhibiting a minimal haemolytic effect. Preferably, the terms mean that the protein is not capable of exhibiting any haemolytic effect.
  • no glycerophospholipid cholesteryl acyl transferase activity means that at most the protein is capable of exhibiting minimal glycerophospholipid cholesteryl acyl transferase activity.
  • the term means that the protein is incapable of exhibiting any glycerophospholipid cholesteryl acyl transferase activity in accordance with the protocol of Lee and Ellis (1990).
  • cytotoxic to 10 5 AS2 tissue culture cells at levels of about 200 ng is not necessarily indicative of an upper or lower level of activity. Instead, it indicates one level wherein cytotoxic activity can be easily observed.
  • cytotoxic to 10 s lymphocytes at levels of about 200 ng is not necessarily indicative of an upper or lower level of activity. Instead, it indicates one level wherein activity can be easily observed.
  • animal as used herein includes any animal, such as a mammal or a fish. Preferably the term means a fish.
  • bacteria as used herein is used in its normal sense - i.e. killed bacteria, usually by treatment with formaldehyde or sometimes by heating, when used as a principal antigenic component of a vaccine.
  • the present invention therefore relates to Aeromonas CIF per se and its use in vaccine compositions.
  • Aeromonas CIF is a very minor protein component of the total extracellular protein and so the presence of Aeromonas CIF in naturally-occurring strains of Aeromonas salmonicida is masked by other proteins.
  • other proteins include proteolytic enzymes and factors which are produced in abundance by Aeromonas strains.
  • An example of one proteolytic factor is the 64kD serine protease (which used to be called the 70kD protease) as reported by Whitby, P. W ., Landon, M. and Coleman, G. (1992). Sheeran, B. and Smith, P.R. (1981) have also reported on a second extracellular protease associated with the fish pathogen Aeromonas salmonicida.
  • Aeromonas CIF can be recovered from a culture of Aeromonas organisms and, in particular, via use of a transposon mutant wherein the proteolytic enzymes and factors, especially the 64 kd serine protease, have been eliminated. Alternatively, the proteolyic enzymes and factors can be inhibited.
  • an example of a inhibitor of protease activity has been reported by Sandvik and Hwaal (1992) who showed that broth cultures of A. salmonicida contain inhibitors of the 64kD serine protease and other proteases such as trypsins from various animal species.
  • Aeromonas CIF has a molecular weight of about approximately 30,000 daltons as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) by the method of Laemmli (1970).
  • the Aeromonas CIF has a pi value of about 5.5 as determined after preparative electrophoresis by the method of Radola (1974).
  • Aeromonas CIF is cytotoxic to macrophages and lymphocytes of the Atlantic salmon and to AS2 tissue culture cells.
  • 200 ng of Aeromonas CIF causes detectable cytotoxicty with 10 5 AS2 cells or lymphocytes.
  • the Aeromonas CIF is not haemolytic.
  • the Aeromonas CIF has no glycerophospholipid cholesteryl acyl transferase activity.
  • Another aspect of the present invention is stabilised Aeromonas CIF.
  • Aeromonas CIF is capable of enhancing the protective properties of vaccines for animals - especially vaccines for fish, more particularly vaccines against furunculosis - the present invention also provides a composition useful as a vaccine against diseases or ailments, such as furunculosis, wherein the composition comprises a vaccine and the protein of the present invention.
  • the composition comprises a bacterin derived from one or more strains of Aeromonas containing Aeromonas CIF, preferably in an amount exceeding 0.001% by weight of the total extracellular Aeromonas proteins of the composition.
  • the composition may be administered to the animal, for example a fish, in any suitable form.
  • the composition can be an injectable composition comprising the Aeromonas CIF in a pharmaceutically acceptable liquid carrier, diluent or excipient, e.g. an aqueous composition.
  • the composition can be an oral composition, comprising the Aeromonas CIF in or on or as an edible carrier, such as an animal feed, especially as a fish feed.
  • the composition may also be an immersion vaccine.
  • a preferred embodiment of the present invention therefore relates to an immunogenic component and a vaccine containing such a component, wherein the vaccine is for administration to fish.
  • a highly preferred embodiment of the present invention therefore relates to an immunogenic component and a vaccine for a fish containing such a component, wherein the vaccine is against organisms implicated in causing furunculosis.
  • the protein is not in its natural environment (i.e. when it has been expressed by the gene coding for the protein when that gene is in its natural environment and is under the control of the promoter with which it is normally associated which is also in its natural environment).
  • the protein has been isolated from Aeromonas or has been prepared by use of recombinant DNA techniques.
  • the present invention therefore provides Aeromonas CIF substantially free from extracellular Aeromonas active protease proteins.
  • Aeromonas CIF substantially free from extracellular Aeromonas active protease proteins.
  • the protein content of the sample preferably comprises at least about 80%, and more preferably at least about 90% Aeromonas CIF.
  • the sample can be an Aeromonas culture extract from which at least the bulk of non-CIF Aeromonas extracellular protein has been removed.
  • a highly preferred embodiment of the present invention relates to the use of Aeromonas CIF to enhance the resistance of fish to furunculosis.
  • the present invention also provides a method for enhancing the resistance of fish to furunculosis wherein Aeromonas CIF is administered to fish in conjunction with a suitable vaccine.
  • compositions comprising a vaccine composition comprising a bacterin derived from one or more strains of Aeromonas, containing Aeromonas CIF.
  • Another highly preferred embodiment of the present invention relates to the production of a composition for immunising an animal, preferably a fish, comprising a vaccine and the protein of the present invention, in which process a culture of, or an extract derived from, one or more strains of Aeromonas is enriched by the addition thereto of Aeromonas CIF.
  • Another highly preferred embodiment of the present invention relates to the use of Aeromonas CIF in a vaccine to enhance the resistance of fish to furunculosis.
  • An improved vaccine such as for immunising against furunculosis, can preferably therefore be prepared by screening existing Aeromonas salmonicida strains to identify one or more that are comparatively high producers of Aeromonas CIF.
  • a bacterin based on such a selected strain will contain an elevated CIF level.
  • an otherwise standard bacterin derived from an Aeromonas salmonicida strain can be improved by the addition of a pure, or concentrated, Aeromonas CIF extract.
  • a CIF-producing strain of Aeromonas such as a strain of Aeromonas salmonicida
  • a nutrient-rich medium such as brain heart infusion broth or tryticase soy broth.
  • An extract from the culture can then be prepared, e.g. by harvesting the culture supernatant and concentration by ultrafiltration.
  • pure Aeromonas CIF can be recovered from the extract by, for example, isoelectric focusing followed by hydrophobic interaction chromatography.
  • Aeromonas CIF can be produced in a different organism, such as Escherichia coli, by transformation of that organism with a gene encoding the Aeromonas CIF protein in active form, or in a form that is non-toxic but nevertheless capable of inducing in fish an immune response.
  • the CIF is naturally associated with the lipopolysaccharide (LPS). If the Aeromonas organism is cultured and a typical bacterin formulation extracted from the culture, the CIF can become separated from the LPS, and it is believed that the CIF may not be as stable in this naked form. However, the extracted CIF can be rendered stable or more stable by, for example, adding a species that will mimick the natural LPS environment. This can be achieved by, for example, purification and/or storage in the presence of suitable detergents, e.g. Triton X-100, Triton X-l 14 or n-octylglucoside. [Triton X is a trade mark of Union Carbide.]
  • the effectiveness of the protein of the present invention is attributable to the interaction of the Aeromonas CIF with the macrophages or lymphocytes of the animal, such as a fish, to stimulate them to an enhanced responsiveness.
  • the cytotoxic effect of Aeromonas CIF against AS-2 cells, and probably also against lymphocytes, is labile at 4°C and even at -20°C in unstabilised preparations (see Table 3 below) whereas the potentiating activity in AVL vaccine is stable for at least a month at 4°C.
  • the two activities are different although they could be properties of the same molecule.
  • the fact that the protein could have two activities could be plausible because other, but different, proteins are believed to exhibit two activities.
  • Bordetella pertussis adenylate cyclase toxin is an enzyme very different from the protein of the present invention, however workers have found that Bordetella pertussis adenylate cyclase toxin has both enzymic (adenylate cyclase) and cytolytic (haemolytic) activities.
  • Bordetella pertussis adenylate cyclase toxin are associated with different domains of the molecule, the enzymic activity being associated with (approximately) residues 1 to 400 and the cytolytic activity being associated with the remainder of the molecule, residues 401 to 1706.
  • Those workers also produced truncated Bordetella pertussis adenylate cyclase toxin molecules which possessed either adenylate cyclase or cytolytic activities respectively, thus confirming that two quite different activities could be associated with a single toxin.
  • use of the protein of the present invention increases the effectiveness of furunculosis vaccines by inducing an effective response in fish against the other factors which the organism produces in relatively small quantities but which have significant physiological impact.
  • a strain of Aeromonas salmonicida was deposited in accordance with the Budapest Treaty at the recognised depositary The National Collections of Industrial and Marine Bacteria Limited (NCIMB) at 23 St Machar Drive, Aberdeen, Scotland, AB2 1RY, United Kingdom, on 8 June 1995 and has the allocated Deposit No. NCIMB 40736.
  • NCIMB National Collections of Industrial and Marine Bacteria Limited
  • Transposon mutant S21 was generated using, as the host, the field isolate A. salmonicida strain 0508 and E. coli BRD 327 containing the suicide vector pRT733 (pJM 103.1 Km R : TnphoA, oriR ⁇ k, mob + for RP4) (Miller and Mekalanos, 1988). S21 does not produce the 64kD serine protease mentioned above (Whitby, P.W., Landon, M. and Coleman, G. (1992)).
  • the protease-deficient strain of Aeromonas salmonicida S21 was cultured in brain heart infusion broth (Oxoid) for 24h at 20°C in 1 litre volumes contained in 2 litre baffled conical flasks.
  • the Sephadex gel was prepared by slowly adding 2.5 g dry, prewashed fine grade Sephadex G-200 to the concentrated culture supernatant (95 ml supernatant and 5 ml 20% Ampholine solution). After rehydration of the gel for 1 hour at 4°C the gel slurry was poured into the mould of an LKB Multiphor II preparative electrofocusing apparatus. After addition of filter paper wicks, electrofocusing was carried out for 18 hours at 1°C (final voltage 1000V). Thirty fractions were obtained and samples were eluted from the Sephadex with 0.9% saline and assayed for cytotoxicity, A280 and pH.
  • cytotoxic fractions pH range 5.5 - 5.9 were bulked, concentrated to ⁇ 1 ml by dialysis against a 7.5% w/v solution of polyethylene glycol (PEG 20000, BDH Ltd.) and loaded onto a column of phenyl-Sepharose CL-4B (30 ml bed volume) equilibrated in 1 M (NH 4 ) 2 SO 4 solution in 0.02M phosphate buffer, pH 7.0.
  • Adsorbed proteins were eluted with a linear gradient of (NH 4 )-SO 4 decreasing from 1 M to zero molar in 0.02M phosphate buffer, pH 7.0 and a gradient of Triton X-100 increasing from 0 to 0.5% in 0.02M phosphate buffer, pH 7.0, total gradient volume, 400 ml). Fractions of 5 ml were collected and fractions 76 and 77 contained the protein of the present invention.
  • the isoelectric point of the protein of the present invention was determined after preparative isoelectric focusing of the proteins when present in concentrated crude culture supernatants in a Sephadex granulated gel following the method of Radola (1974, supra). After elution of proteins from the Sephadex support gel with 0.9% saline, the pH of each fraction was measured at the same temperature as for separation (i.e. 1°C). The protein of the present invention had a measured pi value of about 5.5.
  • Triton X-114 (and similar detergents) is an effective stabiliser of the protein of the present invention (see Table 1 below), has a low CMC (0.02%), is inexpensive and is not toxic to fish (at 0.2% w/v). Furthermore, this detergent forms a single phase with water at temperatures below 30°C but separates into detergent-rich and aqueous phases at temperatures above 30°C, thereby allowing easy recovery of the amphipathic protein of the present invention in the detergent-rich phase.
  • the protein of the present invention after purification by isoelectric focusing was then concentrated by dialysis against polyethylene glycol 20000 to 5.2 mg/ml protein and lOO ⁇ l of this solution was added to 900 ⁇ l 1% Triton X-114 in phosphate buffered saline at 0°C. After periodic mixing for 20 min the solution was incubated at 37°C for 10 min and the phases separated by centrifugation at 12000 x g for 10 min. By SDS-PAGE it was shown that the protein was recovered in high yield in the detergent phase with only traces partitioning in the aqueous phase.
  • the protein could also be extracted from culture supernatants (or whole cultures) by addition of Triton X-1 14 to a concentration of 1%, incubation of the culture at 0 - 4°C for 20 min. incubation at 37°C for 10 min and recovery of the separated phases by centrifugation. From crude cultures or culture supernatants the protein of the present invention was recovered as the dominant protein.
  • volumes of lOO ⁇ l of the cell suspension were dispensed into the wells of a 96-well microtitre plate (flat- bottomed wells) and after culture for 24 h at 20°C the medium was removed and lOO ⁇ l of serial doubling dilutions of Aeromonas CIF in serum-free MEM were added. After incubation for 24 h at 20°C the cell monolayers were inspected with an inverted microscope. The end-point in the titration was the dilution of a sample which destroyed 50% of the monolayer in comparison to MEM-treated control wells.
  • lymphocytes Fractions of cells enriched for lymphocytes and macrophages were obtained by gradient centrifugation of the peripheral blood of Atlantic salmon.
  • lymphocytes appear to be 16-32 times more sensitive to ⁇ the protein of the present invention than macrophages.
  • GCAT glycerophospholipid cholesteryl acyl transferase
  • Aeromonas CIF The gene encoding Aeromonas CIF is identified by, for example, preparation of a gene bank from the DNA of A. salmonicida. Then clones containing the gene for Aeromonas CIF are isolated. The gene is then subcloned and expressed in E. coli following, for example, the teachings of Sambrook et al (1989). In this regard, DNA from the bacteria is partially digested with suitable endonucleases, separated on sucrose gradients and cloned into an appropriate cloning vector such as phage ⁇ gtl 1. Phages carrying and or expressing the gene for Aeromonas CIF are then easily detected using antiserum to Aeromonas CIF. Suitable clones are subcloned and the DNA is transferred to an expression vector for production of sufficient Aeromonas CIF for incorporation into an appropriate vaccine. K. VACCINE COMPOSITION PRODUCTION
  • Aeromonas CIF A quantity (2.5 mg) of Aeromonas CIF was recovered by electrofocusing of a 20 - fold concentrate of 4 litres of 24 h culture supernatant of Aeromonas salmonicida S9 as described above.
  • the Aeromonas CIF solution was adjusted to protein concentrations of 6.2, 3.1 and 1.6 ⁇ g/ml with sterile 0.9% saline and 8 ml of saline. These preparations therefore contained the protein of the present invention in an amount of 0.003 %w/v, 0.0015 %w/v and 0.0008 %w/v, respectively, in the vaccine composition.
  • Vaccine AVL 013 contains formoiised (i.e. formaldehyde-treated) cells of A. salmonicida mixed with an adjuvant which is probably aluminium phosphate.
  • NC IMB The Nat ional Col lect ions of Indust r ial and Marine Bacteria Limi ted ( NC IMB )

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Abstract

A non-haemolytic protein having cellular immunosuppressive activity but no glycerophospholipid cholesteryl acyl transferase activity is described. The protein is obtainable from an Aeromonas organism and has the following characteristics: (i) a molecular weight of about 30,000 Daltons; (ii) a pI value of about 5.5; (iii) cytotoxic to about 105 lymphocytes at levels of about 200 ng; and (iv) cytotoxic to about 105 AS2 tissue culture cells at levels of about 200 ng. The protein is useful for enhancing the immunising effects of vaccines.

Description

VACCINE COMPONENT
The present invention relates to a vaccine component.
In particular, the present invention relates to an immunogenic component expressed by microorganisms and to vaccines containing such a component.
More in particular, the present invention relates to an immunogenic component obtainable from an Aeromonas organism and to a vaccine composition comprising the component and a vaccine, especially a vaccine against furunculosis.
The vaccine composition of the present invention is useful for administration to animals, especially fish.
Furunculosis is a significant disease that can infect many species of fish, examples of which include all species of salmon, rainbow trout, brook trout, brown trout, carp, goldfish and wrasse. In the case of salmon, furunculosis is caused by the bacterium Aeromonas salmonicida.
As furunculosis can occur in many species of fish which are of commercial significance, so the intensive rearing of fish such as salmon, which is practised today on a wide scale, suffers from the disadvantage that the entire stock of fish in a facility can become infected with disease. Moreover, the commercial consequences of a serious disease outbreak can be enormous, particularly in the farming of Atlantic salmon (Salmo salar).
Thus, the desirability of immunising farmed fish against infections and diseases, such as furunculosis, has long been recognised. However, despite the fact that the Aeromonas organism has been the subject of much scientific research, technical progress in preparing a suitable vaccine against furunculosis has been slow. In this regard, various workers have tried to identify the factors, such as extracellular proteins, which might cause the organism to be toxic to fish and which might provide the basis for vaccine compositions to generate immunity against the organism. But the position is complicated because the Aeromonas organism appears to comprise or to generate a wide range of factors which have differing toxic or immunosuppressive activities in fish. Thus, previous research has tended to concentrate on the factors which the organism produces in greatest abundance.
At present there are a few commercially-available vaccines which are recommended for use against furunculosis, but the effectiveness of these vaccines often requires the use of oil-based adjuvant.
The present invention seeks to provide a vaccine component that can enhance the effectiveness of a vaccine, especially a vaccine against furunculosis.
According to a first aspect of the present invention there is provided a non-haemolytic protein having cellular immunosuppressive activity but no glycerophospholipid cholesteryl acyl transferase activity, wherein the protein is obtainable from an Aeromonas organism and has the following characteristics:
(i) a molecular weight of about 30,000 daltons; (ii) a pi value of about 5.5;
(iii) is cytotoxic to about 105 lymphocytes at levels of about 200 ng; and (iv) is cytotoxic to about 105 AS2 tissue culture cells at levels of about 200 ng.
According to a second aspect of the present invention there is provided a composition comprising a vaccine and the protein according to the present invention, and optionally a suitable carrier, excipient or diluent.
According to a third aspect of the present invention there is provided Aeromonas salmonicida strain S9 (NCIMB 40736). According to a fourth aspect of the present invention there is provided Aeromonas salmonicida strain S21 (NCIMB 40737).
According to a fifth aspect of the present invention there is provided a protein according to the present invention or a composition according to the present invention for use in or as a vaccine composition for immunising an animal, preferably a vertebrate animal.
According to a sixth aspect of the present invention there is provided the use of a protein according to the present invention in the manufacture of a vaccine composition for immunising an animal, preferably a vertebrate animal.
According to a seventh aspect of the present invention there is provided the use of a protein according to the present invention to suppress the cellular immune response in an animal, preferably a vertebrate animal, preferably when the protein is present in a vaccine composition.
According to a eighth aspect of the present invention there is provided the use of the protein according to the present invention in a vaccine composition to enhance the resistance to fish to furunculosis.
According to a ninth aspect of the present invention there is provided a method for enhancing the resistance of fish to furunculosis, wherein the protein according to the present invention is administered to fish.
Thus, in its broadest sense, the present invention relates to a hitherto unknown immunogenic protein produced by Aeromonas organisms. In the following commentary, the immunogenic protein according to the present invention is sometimes referred to as the Aeromonas Cellular Immunosuppressive Factor, or Aeromonas CIF for short. Preferably, the protein is obtainable from Aeromonas salmonicida.
Preferably, the protein is purified under conditions wherein the protein is stabilised. Preferably, therefore, the protein is purified by use of a species that is capable of stabilising the protein. Preferably, the species is a detergent, preferably a detergent that forms two phases at an elevated temperature.
Preferably, the protein is stored in an environment that prevents or hinders proteolytic degradation thereof.
Preferably, the protein has been stored before use at low temperature, for example at about 4°C.
Preferably, the protein is obtainable from Aeromonas salmonicida strain NCIMB 40736 or NCIMB 40737.
Preferably, the vaccine is a vaccine for a fish.
Preferably, the animal is a fish.
Preferably, the fish is a Salmonid.
Preferably, the Salmonid is salmon, preferably Atlantic salmon.
Preferably, in the composition, the vaccine is a vaccine for immunising against furunculosis.
Preferably, the furunculosis is caused by Aeromonas salmonicida.
Preferably, the vaccine composition is suitable for oral administration to the animal. Preferably, the protein of the present invention is present in an amount of from about 0.0008 %w/v to about 0.003 %w/v, preferably about 0.0015 %w/v, in the vaccine composition.
Preferably the protein of the invention is present in the composition in an amount of at least 0.001% by weight of the composition.
One of the key advantages of the present invention is that the Aeromonas CIF can enhance the immunising effect of vaccines for animals, in particular those vaccines used for fish, especially vaccines used for immunising against furunculosis.
It is known that the adaptive immune response of vertebrates can involve both humoral and cellular responses to the administration of foreign antigens. The humoral response involves the production of antibodies whereas the cellular response, or cell-mediated immunity, involves stimulation of T lymphocytes. The protein of the present invention is advantageous because it is non-haemolytic and is capable exhibiting a cellular immunosuppressive activity.
As indicated the present invention is particularly advantageous for enhancing the immunising effect of a vaccine for administration to salmon for immunising the salmon against furunculosis. However, a further advantage of the protein of the present invention is that it can enhance the effect of a vaccine for immunising other animals against furunculosis as well enhancing the effect of other vaccines for immunising salmon or other animals. With reference to fish (such as salmon, rainbow trout, brook trout, brown trout, carp, goldfish and wrasse), the protein of the present invention is capable of enhancing vaccines against vibriosis (caused by Vibrio anguillarum), Hitra disease or cold-water vibriosis (Vibrio salmonicida), enteric redmouth ( Yersinia ruckerϊ), salmonid rickettsial septicaemia (Piscirickettsia salmonis - which is a problem at present in Chile) and viral diseases such as infectious pancreatic necrosis (IPN), infectious haematopoietic necrosis (IHN), viral haemorrhagic septicaemia (VHS), pancreas disease (PD) and plasmacytoid leukaemia. In this regard, there are some vaccines that are used against vibriosis, cold-water vibriosis and enteric redmouth. Even though these vaccines are effective, as they induce a humoral response to the bacterial lipopolysaccharide, they can be made more effective if admixed with the protein of the present invention.
The terms "Aeromonas Cellular Immunosuppressive Factor" or "Aeromonas CIF" as used herein do not necessarily mean that the protein must be obtained from Aeromonas as the protein may be obtained synthetically or by use of recombinant DNA techniques wherein the gene coding for the protein can be expressed in a suitable host organism, such as E.coli. Alternatively, the protein can be prepared synthetically.
The terms "non-haemolytic" and "not haemolytic" as used herein mean that at most the protein is capable of exhibiting a minimal haemolytic effect. Preferably, the terms mean that the protein is not capable of exhibiting any haemolytic effect.
The term "no glycerophospholipid cholesteryl acyl transferase activity" as used herein means that at most the protein is capable of exhibiting minimal glycerophospholipid cholesteryl acyl transferase activity. Preferably, the term means that the protein is incapable of exhibiting any glycerophospholipid cholesteryl acyl transferase activity in accordance with the protocol of Lee and Ellis (1990).
The term "cytotoxic to 105 AS2 tissue culture cells at levels of about 200 ng" is not necessarily indicative of an upper or lower level of activity. Instead, it indicates one level wherein cytotoxic activity can be easily observed.
Likewise, the term "cytotoxic to 10s lymphocytes at levels of about 200 ng" is not necessarily indicative of an upper or lower level of activity. Instead, it indicates one level wherein activity can be easily observed.
The term "animal" as used herein includes any animal, such as a mammal or a fish. Preferably the term means a fish. The term "bacterin" as used herein is used in its normal sense - i.e. killed bacteria, usually by treatment with formaldehyde or sometimes by heating, when used as a principal antigenic component of a vaccine.
The present invention therefore relates to Aeromonas CIF per se and its use in vaccine compositions.
Our initial studies relating to the present invention revealed that Aeromonas CIF is a very minor protein component of the total extracellular protein and so the presence of Aeromonas CIF in naturally-occurring strains of Aeromonas salmonicida is masked by other proteins. Examples of those other proteins include proteolytic enzymes and factors which are produced in abundance by Aeromonas strains. An example of one proteolytic factor is the 64kD serine protease (which used to be called the 70kD protease) as reported by Whitby, P. W ., Landon, M. and Coleman, G. (1992). Sheeran, B. and Smith, P.R. (1981) have also reported on a second extracellular protease associated with the fish pathogen Aeromonas salmonicida.
Our further studies relating to the present invention revealed that Aeromonas CIF can be recovered from a culture of Aeromonas organisms and, in particular, via use of a transposon mutant wherein the proteolytic enzymes and factors, especially the 64 kd serine protease, have been eliminated. Alternatively, the proteolyic enzymes and factors can be inhibited. In this regard, an example of a inhibitor of protease activity has been reported by Sandvik and Hwaal (1992) who showed that broth cultures of A. salmonicida contain inhibitors of the 64kD serine protease and other proteases such as trypsins from various animal species. Other examples include use of the inhibitors that can be found in two commercial vaccines, namely Aquavac Furovac 1M (which is a trade mark of and is supplied by Aquaculture Vaccines Ltd.) and Furogen b (which is a trade mark of and is supplied by Aqua Health Ltd.). Our subsequent studies relating to the present invention revealed that the Aeromonas CIF has a molecular weight of about approximately 30,000 daltons as determined by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) by the method of Laemmli (1970). The Aeromonas CIF has a pi value of about 5.5 as determined after preparative electrophoresis by the method of Radola (1974). In addition, we found that the Aeromonas CIF is cytotoxic to macrophages and lymphocytes of the Atlantic salmon and to AS2 tissue culture cells. In this regard. 200 ng of Aeromonas CIF causes detectable cytotoxicty with 105 AS2 cells or lymphocytes. The Aeromonas CIF is not haemolytic. The Aeromonas CIF has no glycerophospholipid cholesteryl acyl transferase activity.
Another aspect of the present invention is stabilised Aeromonas CIF.
As the Aeromonas CIF is capable of enhancing the protective properties of vaccines for animals - especially vaccines for fish, more particularly vaccines against furunculosis - the present invention also provides a composition useful as a vaccine against diseases or ailments, such as furunculosis, wherein the composition comprises a vaccine and the protein of the present invention.
Preferably, the composition comprises a bacterin derived from one or more strains of Aeromonas containing Aeromonas CIF, preferably in an amount exceeding 0.001% by weight of the total extracellular Aeromonas proteins of the composition. The composition may be administered to the animal, for example a fish, in any suitable form. For example, the composition can be an injectable composition comprising the Aeromonas CIF in a pharmaceutically acceptable liquid carrier, diluent or excipient, e.g. an aqueous composition. Alternatively, the composition can be an oral composition, comprising the Aeromonas CIF in or on or as an edible carrier, such as an animal feed, especially as a fish feed. The composition may also be an immersion vaccine. A preferred embodiment of the present invention therefore relates to an immunogenic component and a vaccine containing such a component, wherein the vaccine is for administration to fish.
A highly preferred embodiment of the present invention therefore relates to an immunogenic component and a vaccine for a fish containing such a component, wherein the vaccine is against organisms implicated in causing furunculosis.
In a highly preferable embodiment of the present invention the protein is not in its natural environment (i.e. when it has been expressed by the gene coding for the protein when that gene is in its natural environment and is under the control of the promoter with which it is normally associated which is also in its natural environment). Thus, in this highly preferred embodiment, the protein has been isolated from Aeromonas or has been prepared by use of recombinant DNA techniques.
In one preferred embodiment the present invention therefore provides Aeromonas CIF substantially free from extracellular Aeromonas active protease proteins. With this aspect, there need not be totally pure Aeromonas CIF, although a pure form can be prepared if desired. Rather, it is generally sufficient if most of the proteases have been removed (i.e. eliminated) or have been inactivated.
In one aspect of the present invention there is provided a sample consisting substantially of Aeromonas CIF. In this sample, the protein content of the sample preferably comprises at least about 80%, and more preferably at least about 90% Aeromonas CIF. Thus, in this embodiment, the sample can be an Aeromonas culture extract from which at least the bulk of non-CIF Aeromonas extracellular protein has been removed.
A highly preferred embodiment of the present invention relates to the use of Aeromonas CIF to enhance the resistance of fish to furunculosis. In addition, the present invention also provides a method for enhancing the resistance of fish to furunculosis wherein Aeromonas CIF is administered to fish in conjunction with a suitable vaccine.
Another highly preferred embodiment of the present invention relates to a composition comprising a vaccine composition comprising a bacterin derived from one or more strains of Aeromonas, containing Aeromonas CIF.
Another highly preferred embodiment of the present invention relates to the production of a composition for immunising an animal, preferably a fish, comprising a vaccine and the protein of the present invention, in which process a culture of, or an extract derived from, one or more strains of Aeromonas is enriched by the addition thereto of Aeromonas CIF.
Another highly preferred embodiment of the present invention relates to the use of Aeromonas CIF in a vaccine to enhance the resistance of fish to furunculosis.
An improved vaccine, such as for immunising against furunculosis, can preferably therefore be prepared by screening existing Aeromonas salmonicida strains to identify one or more that are comparatively high producers of Aeromonas CIF. A bacterin based on such a selected strain will contain an elevated CIF level. Alternatively, an otherwise standard bacterin derived from an Aeromonas salmonicida strain can be improved by the addition of a pure, or concentrated, Aeromonas CIF extract.
To prepare a suitable __ero/r»o.. --CIF-rich extract, a CIF-producing strain of Aeromonas, such as a strain of Aeromonas salmonicida, can be cultured by growth in a nutrient-rich medium, such as brain heart infusion broth or tryticase soy broth. An extract from the culture can then be prepared, e.g. by harvesting the culture supernatant and concentration by ultrafiltration. If desired, pure Aeromonas CIF can be recovered from the extract by, for example, isoelectric focusing followed by hydrophobic interaction chromatography.
An alternative preferred method for preparing an improved vaccine, such as for immunising against furunculosis, is to induce a natural Aeromonas strain to produce enhanced levels of CIF by mutation, selective breeding or by genetic engineering. Indeed, in a further alternative, Aeromonas CIF can be produced in a different organism, such as Escherichia coli, by transformation of that organism with a gene encoding the Aeromonas CIF protein in active form, or in a form that is non-toxic but nevertheless capable of inducing in fish an immune response.
At present it is believed that in the living Aeromonas organism the CIF is naturally associated with the lipopolysaccharide (LPS). If the Aeromonas organism is cultured and a typical bacterin formulation extracted from the culture, the CIF can become separated from the LPS, and it is believed that the CIF may not be as stable in this naked form. However, the extracted CIF can be rendered stable or more stable by, for example, adding a species that will mimick the natural LPS environment. This can be achieved by, for example, purification and/or storage in the presence of suitable detergents, e.g. Triton X-100, Triton X-l 14 or n-octylglucoside. [Triton X is a trade mark of Union Carbide.]
Without wishing to be bound by theory it is believed that the effectiveness of the protein of the present invention is attributable to the interaction of the Aeromonas CIF with the macrophages or lymphocytes of the animal, such as a fish, to stimulate them to an enhanced responsiveness. The cytotoxic effect of Aeromonas CIF against AS-2 cells, and probably also against lymphocytes, is labile at 4°C and even at -20°C in unstabilised preparations (see Table 3 below) whereas the potentiating activity in AVL vaccine is stable for at least a month at 4°C. Thus, the two activities are different although they could be properties of the same molecule. The fact that the protein could have two activities could be plausible because other, but different, proteins are believed to exhibit two activities. One such other, different protein is Bordetella pertussis adenylate cyclase toxin. Bordetella pertussis adenylate cyclase toxin is an enzyme very different from the protein of the present invention, however workers have found that Bordetella pertussis adenylate cyclase toxin has both enzymic (adenylate cyclase) and cytolytic (haemolytic) activities. Those workers have also shown that these properties of Bordetella pertussis adenylate cyclase toxin are associated with different domains of the molecule, the enzymic activity being associated with (approximately) residues 1 to 400 and the cytolytic activity being associated with the remainder of the molecule, residues 401 to 1706. Those workers also produced truncated Bordetella pertussis adenylate cyclase toxin molecules which possessed either adenylate cyclase or cytolytic activities respectively, thus confirming that two quite different activities could be associated with a single toxin.
Therefore, in the highly preferred embodiment, it is believed that use of the protein of the present invention increases the effectiveness of furunculosis vaccines by inducing an effective response in fish against the other factors which the organism produces in relatively small quantities but which have significant physiological impact.
A strain of Aeromonas salmonicida, namely S9 (as defined below), was deposited in accordance with the Budapest Treaty at the recognised depositary The National Collections of Industrial and Marine Bacteria Limited (NCIMB) at 23 St Machar Drive, Aberdeen, Scotland, AB2 1RY, United Kingdom, on 8 June 1995 and has the allocated Deposit No. NCIMB 40736.
Transposon mutant S9 of A. salmonicida strain 80628, which is a virulent field isolate from a case of furunculosis in Atlantic salmon, was generated by conjugation with Escherichia coli strain HB101 containing the suicide vector pUW964 (pRK2013 Km::Tn7 xyz: Tn5,TpR, SpR, KmR) (Weiss et al. 1983). Another strain of Aeromonas salmonicida, namely S21 (as defined below), was deposited in accordance with the Budapest Treaty at the recognised depositary The National Collections of Industrial and Marine Bacteria Limited (NCIMB) at 23 St Machar Drive, Aberdeen, Scotland, AB2 1RY, United Kingdom, on 8 June 1995 and then redeposited on 15 December 1995 and has the allocated Deposit No. NCIMB 40737.
Transposon mutant S21 was generated using, as the host, the field isolate A. salmonicida strain 0508 and E. coli BRD 327 containing the suicide vector pRT733 (pJM 103.1 KmR : TnphoA, oriRόk, mob+ for RP4) (Miller and Mekalanos, 1988). S21 does not produce the 64kD serine protease mentioned above (Whitby, P.W., Landon, M. and Coleman, G. (1992)).
The present invention will now be described only by way of example.
CULTURING OF AEROMONAS SALMONICIDA
The protease-deficient strain of Aeromonas salmonicida S21 was cultured in brain heart infusion broth (Oxoid) for 24h at 20°C in 1 litre volumes contained in 2 litre baffled conical flasks.
B. PREPARATION OF AEROMONAS CIF
An inoculum of 10 mis of an overnight culture from the above-mentioned culture was used. The culture supernatant was harvested by centrifugation and the supernatant was concentrated 80-fold using a Millipore "Minitan" ultrafiltration system with a membrane having a cut-off size of 30 kilodaltons. The concentrated culture supernatant was dialysed overnight at 4°C against 4 litres 1% glycine solution. Preparative electrofocusing was carried out in a layer of Sephadex G-200 (Pharmacia) gel in 1% Ampholines (pH range 3.5 - 10; Pharmacia). The Sephadex gel was prepared by slowly adding 2.5 g dry, prewashed fine grade Sephadex G-200 to the concentrated culture supernatant (95 ml supernatant and 5 ml 20% Ampholine solution). After rehydration of the gel for 1 hour at 4°C the gel slurry was poured into the mould of an LKB Multiphor II preparative electrofocusing apparatus. After addition of filter paper wicks, electrofocusing was carried out for 18 hours at 1°C (final voltage 1000V). Thirty fractions were obtained and samples were eluted from the Sephadex with 0.9% saline and assayed for cytotoxicity, A280 and pH. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was also done and cytotoxic fractions (pH range 5.5 - 5.9) were bulked, concentrated to < 1 ml by dialysis against a 7.5% w/v solution of polyethylene glycol (PEG 20000, BDH Ltd.) and loaded onto a column of phenyl-Sepharose CL-4B (30 ml bed volume) equilibrated in 1 M (NH4)2SO4 solution in 0.02M phosphate buffer, pH 7.0. Adsorbed proteins were eluted with a linear gradient of (NH4)-SO4 decreasing from 1 M to zero molar in 0.02M phosphate buffer, pH 7.0 and a gradient of Triton X-100 increasing from 0 to 0.5% in 0.02M phosphate buffer, pH 7.0, total gradient volume, 400 ml). Fractions of 5 ml were collected and fractions 76 and 77 contained the protein of the present invention.
C. MOLECULAR WEIGHT DETERMINATION OF AEROMONAS CIF
Molecular weight estimation was by SDS-polyacrylamide gel electrophoresis using the method of Laemmli ( 1970) with Sigma low molecular weight standards (bovine serum albumin, 66kD; egg albumin, 45kD; glyceraldehyde-3 -phosphate dehydrogenase, 36kD; carbonic anhydrase, 29kD; trypsinogen, 24kD; trypsin inhibitor, 20.1kD and alpha- lactalbumin, 14.2kD). Resolving gels contained 12% (w/v) acrylamide and stacking gels contained 4.5% (w/v) acrylamide.
Protein bands were visualised by silver staining (Oakley et al , 1980). The measured Mr was about 30,000 Daltons as determined by SDS-PAGE. D. ISOELECTRIC POINT DETERMINATION OF AEROMONAS CIF
The isoelectric point of the protein of the present invention was determined after preparative isoelectric focusing of the proteins when present in concentrated crude culture supernatants in a Sephadex granulated gel following the method of Radola (1974, supra). After elution of proteins from the Sephadex support gel with 0.9% saline, the pH of each fraction was measured at the same temperature as for separation (i.e. 1°C). The protein of the present invention had a measured pi value of about 5.5.
E. EXTRACTION OF AEROMONAS CIF USING DETERGENT
The following commentary describes the extraction of the protein of the present from culture supernatant using Triton X-1 14.
Since it is thought that the protein is amphipathic and readily associates with detergent micelles, phase separation was used to simplify the partial purification of the protein. These studies showed that Triton X-114 (and similar detergents) is an effective stabiliser of the protein of the present invention (see Table 1 below), has a low CMC (0.02%), is inexpensive and is not toxic to fish (at 0.2% w/v). Furthermore, this detergent forms a single phase with water at temperatures below 30°C but separates into detergent-rich and aqueous phases at temperatures above 30°C, thereby allowing easy recovery of the amphipathic protein of the present invention in the detergent-rich phase.
The protein of the present invention after purification by isoelectric focusing was then concentrated by dialysis against polyethylene glycol 20000 to 5.2 mg/ml protein and lOOμl of this solution was added to 900μl 1% Triton X-114 in phosphate buffered saline at 0°C. After periodic mixing for 20 min the solution was incubated at 37°C for 10 min and the phases separated by centrifugation at 12000 x g for 10 min. By SDS-PAGE it was shown that the protein was recovered in high yield in the detergent phase with only traces partitioning in the aqueous phase. The protein could also be extracted from culture supernatants (or whole cultures) by addition of Triton X-1 14 to a concentration of 1%, incubation of the culture at 0 - 4°C for 20 min. incubation at 37°C for 10 min and recovery of the separated phases by centrifugation. From crude cultures or culture supernatants the protein of the present invention was recovered as the dominant protein.
F. CYTOTOXICITY OF AEROMONAS CIF TO AS2 CELLS
Cells from the established tissue culture cell line of Atlantic salmon (AS-2) were removed from mono layer culture by trypsinisation and resuspended to a concentration of 106 cells ml" 1 in Eagle's Minimal Essential Medium (MEM; Eagle, 1959), pH 7.3. containing 10% foetal calf serum, 2 mM L-glutamine, 0.075% sodium bicarbonate, 20 mM Tris /HC1 buffer, Non-Essential Amino Acids, 100 international units/ml penicillin, 100 μg/ml streptomycin and 2.5 μg/ml amphotericin B. Volumes of lOOμl of the cell suspension were dispensed into the wells of a 96-well microtitre plate (flat- bottomed wells) and after culture for 24 h at 20°C the medium was removed and lOOμl of serial doubling dilutions of Aeromonas CIF in serum-free MEM were added. After incubation for 24 h at 20°C the cell monolayers were inspected with an inverted microscope. The end-point in the titration was the dilution of a sample which destroyed 50% of the monolayer in comparison to MEM-treated control wells.
The results showed that the protein of the present invention when purified in the absence of a stabiliser routinely had a titre of 1/128 in the assay, equivalent to 200 ng causing detectable cytotoxicity with 105 cells. However, surprisingly, when the protein of the present invention had been stabilised by purification in the presence of 0.1 % Triton X-100 the protein was active in the above assay at dilutions of > 1/2048, such that lOng Aeromonas CIF in a volume of lOOμl serum-free MEM caused a cytotoxic effect with 105 cells. G. CYTOTOXICITY OF AEROMONAS CIF TO LYMPHOCYTES AND MACROPHAGES
Fractions of cells enriched for lymphocytes and macrophages were obtained by gradient centrifugation of the peripheral blood of Atlantic salmon. In assays such as that described above for Atlantic salmon cells the protein of the present invention had a similar cytotoxic titre towards lymphocytes as AS-2 cells (titre of native protein = 1/128 in both cases) but a much lower cytotoxic activity against macrophages (titre of protein = 1/4 to 1/8). Thus lymphocytes appear to be 16-32 times more sensitive to ι the protein of the present invention than macrophages.
H. GCAT ACTIVITY STUDIES OF AEROMONAS CIF
Following the protocol of Lee, K.-K. and Ellis, A.E. (1990) the protein of the present i invention was investigated to determine if it had glycerophospholipid cholesteryl acyl transferase (GCAT) activity. Glycerophospholipid cholesterol acyl transferase is a major lethal exotoxin and cytolysin of Aeromonas salmonicida. The experiments showed that the protein of the present invention does not have glycerophospholipid cholesterol acyl transferase activity according to this protocol.
I. STUDIES OF STABILISATION OF AEROMONAS CIF BY DETERGENTS
In these studies, detergents were added to the protein of the present invention when it had been purified by isoelectricfocusing. The results of these studies were that the activity of protein was enhanced up to 8-fold. The activity of 5 detergents tested is shown in Table 1. From the results, it would appear that the degree of stimulation is related to the critical micelle concentration (CMC) of the detergents used. Greater recoveries of the protein of the present invention, measured by cytotoxicity titre against AS-2 cells, were obtained by incorporating detergent during isoelectricfocusing. The requirement for detergents to be present at at least (preferably greater than) the CMC is confirmed for N-octylglucoside, which has a CMC of 0.7% (see Table 2). Table 1
The effect of various detergents on the cvtotoxic activitv of Aeromonas CIF on AS-2 cells
Detergent Cytotoxicity titre detergent* + cytotoxin detergent alone*
none 64
Triton X-100 256
Triton X-114 512 32
N-octylglucoside 64
N-dodecylglucoside 64 32
N-dodecylmaltoside 128 32 * all detergents were incorporated to 0.1% (w/v)
Table 2
The effect of N-octylelucoside concentration on the cvtotoxic activitv of Aeromonas CIF on AS-2 cells
Concentration of detergent Reciprocal of cytotoxicity titre (% w/v) of peak fraction
none 128
0.1 256
0.2 512
0.7 2048
[0.1 % Triton X-100] 2048 The cytotoxicity of Aeromonas CIF was retained when stored in the presence of 0.1% Triton X-100 (Table 3). Loss of activity of the native Aeromonas CIF on storage at - 20°C was correlated with progressive conversion of the single 30kD band observed on SDS-polyacrylamide gel electrophoresis into a doublet.
Table 3
The stability of the cvtotoxic activitv of Aeromonas CIF prepared in the presence or absence of Triton X-100
Sample Cytotoxicity titre of CIF stored at -20°C for:
0 days 7 days 28 days
CIF purified without Triton X-100 128 32 0
CIF purified with
0.1% Triton X-100 > 2048 * > 2048 > 2048
* greatest dilution tested
J. PREPARATION OF AEROMONAS CIF BY RECOMBINANT DNA
TECHNIQUES
The gene encoding Aeromonas CIF is identified by, for example, preparation of a gene bank from the DNA of A. salmonicida. Then clones containing the gene for Aeromonas CIF are isolated. The gene is then subcloned and expressed in E. coli following, for example, the teachings of Sambrook et al (1989). In this regard, DNA from the bacteria is partially digested with suitable endonucleases, separated on sucrose gradients and cloned into an appropriate cloning vector such as phage λgtl 1. Phages carrying and or expressing the gene for Aeromonas CIF are then easily detected using antiserum to Aeromonas CIF. Suitable clones are subcloned and the DNA is transferred to an expression vector for production of sufficient Aeromonas CIF for incorporation into an appropriate vaccine. K. VACCINE COMPOSITION PRODUCTION
A quantity (2.5 mg) of Aeromonas CIF was recovered by electrofocusing of a 20 - fold concentrate of 4 litres of 24 h culture supernatant of Aeromonas salmonicida S9 as described above. The Aeromonas CIF solution was adjusted to protein concentrations of 6.2, 3.1 and 1.6 μg/ml with sterile 0.9% saline and 8 ml of saline. These preparations therefore contained the protein of the present invention in an amount of 0.003 %w/v, 0.0015 %w/v and 0.0008 %w/v, respectively, in the vaccine composition.
The Aeromonas CIF solutions were then mixed with an equal volume of the furunculosis vaccine AVL 013 (supplied by Aquaculture Vaccines Ltd., Saffron Walden, U.K.). Vaccine AVL 013 contains formoiised (i.e. formaldehyde-treated) cells of A. salmonicida mixed with an adjuvant which is probably aluminium phosphate.
L. TESTING OF VACCINE COMPOSITION IN FISH
A trial was conducted in salmon using the vaccine composition prepared above. Groups of 60 Atlantic salmon, mean weight 30 g were anaesthetised by addition of benzocaine. final concentration 15-20 parts per million, to the tank water and injected with 0.2 ml vaccine. Fish were distributed into four 560 litre tanks with equal numbers from each group in each tank. Fish were maintained at a temperature of 11 -
13°C for 6 weeks and a furunculosis cohabitation challenge was initiated by addition of Atlantic salmon injected with 105 colony forming units of Aeromonas salmonicida strain FCC (1 infected fish per 10 vaccine trial fish). Mortalities were recorded daily for 43 days and bacteriological culture was carried out on the kidney of all dead fish to confirm the presence of Aeromonas salmonicida.
In the control, unimmunised group of 60 fish, 85% died as a result of the challenge and the Relative Percentage Survival (RPS = 100 (1 - (% mortality in vaccinated fish/ % mortality in unvaccinated control fish)) was calculated for each vaccine group (Table 4).
A similar vaccine trial was carried out with fish immunised with vaccines containing Aeromonas salmonicida CIF which had been stored at 4°C for 4 weeks. In this trial mortalities were monitored for 20 days after challenge by cohabitation with A eromonas salmonicida-infected fish (Table 4).
Table 4 Relative Percentage Survival of fish immunised with vaccines containing Aeromonas salmonicida CIF
Vaccine Relative percentage survival with vaccine containing: freshly prepared CIF CIF stored 4 weeks at 4°C
AVL 013 21.6 23.5
AVL 013 + 6.2μg CIF 25.5 39.2
AVL 013 + 3.1μg CIF 29.4 51.0
AVL 013 + 1.6μg CIF 27.5 45.1
(CIF = Aeromonas CIF)
The results of Table 4 indicate that a vaccine based on the Aeromonas CIF enhanced the protection obtained using a conventional furunculosis vaccine. The results also indicate that storage of Aeromonas CIF at 4°C for 4 weeks before incorporation into AVL vaccine did not diminish its ability to potentiate the activity of AVL013. In contrast to this, the RPS values were greater for all doses of Aeromonas CIF tested.
In similar studies, the RPS values for vaccines with stored octylglucoside-stabilised Aeromonas CIF were shown to be greater than for AVL013 alone with 5 of the 6 doses of Aeromonas CIF employed. Other modifications of the present invention will be apparent to those skilled in the art without departing from the scope of the invention.
REFERENCES
Eagle. H. (1959) Science, 130, 432.
Laemmli, U.K. (1970) Nature, 227, 680-685.
Lee, K.-K. and Ellis, A.E. (1990) Journal of Bacteriology, 172. 5382-5393.
Miller, V.L. and Mekalanos, J.J. ( 1988) Journal of Bacteriology, 170, 2575-2583.
Oakley, B.R., Kirsch, D.R. and Morris, R. (1980) Analytical Biochemistry, 105, 361- 363.
Radola, B.J. (1974) Biochim. Biophys. Acta, 386, 181-195.
Sambrook et al. in Molecular Cloning: A Laboratory Manual, 2nd edition, 1989, Cold Spring Harbor Laboratory Press
Sandvik, O. and Hwaal, A.-B. (1992) Journal of Fish Diseases, 15, 131-141.
Sheeran, B. and Smith, P.R. 1981, FEMS Microbiology Letters, 11, 73-76.
Weiss, A.A., Hewlett, E ., Myers, G.A. and Falkow, S. (1983) Infection and Immunity, 42, 33-41.
Whitby, P.W.. Landon, M. and Coleman, G. 1992, FEMS Microbiology Letters 99, 65-72. INDICATIONS RELATI NG TO A DEPOSITED M ICROORGAN ISM
(PCT Rule 13-XJΓ)
A. The indications made below relate to the microorganism referred to in the description on page 12 , lines 20-24
B. I D ENTIFICATION OF DEPOSIT Further deposits are identified on an additional sheet \ ~~\
Name ol depositary institution The Nationa l Col lections of Industrial and Marine Bacteria Limi ted ( NCIMB )
Address of depositary institution (including postal code and country) 23 St Machar Drive Aberdeen AB2 1 RY Uni ted Kingdom
Dale of deposit Accession Number 8 June 1995 NC IMB 40736
C. ADDITIONAL INDICATIONS (leave blank if not applicable) This information is continued on an additional sheet j_J
In respect of those designations in which a European patent is sought, and any other designated state having equivalent legislation, a sample of the deposited microorganism will only be made available either until the publication of the mention of the grant of the patent or after twenty years from the date of filing if the application has been refused or withdrawn or is deemed to be withdrawn, only by the issue of such a sample to an expert nominated by the person requesting] the sample. (Rule 28(4) EPC)
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The indications listed below will be submitted to the International Bureau later (specify the general nature of the indications eg "Accession Number of Deposit")
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D This sheet was received by the International Bureau on:
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Figure imgf000026_0001
INDICATIONS RE LATING TO A DEPOSITED MICROORG AN ISM
Figure imgf000027_0001
A. The indications made below relate to the microorganism referred to in the description on page 1 3 , ImeS 1 ~6
B. IDENTIFICATION OF DEPOSIT Further deposits are identified on an additional sheet ~~~ ]
Name ot depositary institution
The Nat ional Col lect ions of Indust r ial and Marine Bacteria Limi ted ( NC IMB )
Address ot depositary institution (including postal code and country)
23 St Machar Drive Aberdeen AB2 1RY United Kingdom
Dale of deposit Accession Number
8 June 199. NC IMB 40737
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In respect of those designations in which a European patent is sought, and any other designated state having equivalent legislation, a sample of the deposited microorganism will only be made available either until the publication of the mention of the grant of the patent or after twenty years from the date of filing if the application has been refused or withdrawn or is deemed to be withdrawn, only by the issue of such a sample to an expert nominated by the person requesting the sample. (Rule 28(4) EPC)
D. DESIGNATED STATES FOR WHICH INDICATIONS ARE MADE f if the indications are not for all designated Stares/
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Figure imgf000027_0002

Claims

1. A non-haemolytic protein having cellular immunosuppressive activity but no glycerophospholipid cholesteryl acyl transferase activity, wherein the protein is obtainable from an Aeromonas organism and has the following characteristics:
(i) a molecular weight of about 30,000 daltons; (ii) a pi value of about 5.5;
(iii) is cytotoxic to about 105 lymphocytes at levels of about 200 ng; and (iv) is cytotoxic to about 105 AS2 tissue culture cells at levels of about 200 ng-
2. A protein according to claim 2, wherein the protein is obtainable from Aeromonas salmonicida.
3. A protein according to claim 1 or claim 2, wherein the protein is purified by use of a species that is capable of stabilising the protein.
4. A protein according to claim 3, wherein the species is a detergent, preferably a detergent that forms two phases at an elevated temperature.
5. A protein according to any one of claims 1 to 4, wherein the protein is stored before use in an environment that hinders or prevents proteolytic degradation thereof.
6. A protein according to claim 5, wherein the protein is stored before use at low temperature, for example at about 4°C.
7. A protein according to any one of claims 1 to 6 wherein the protein is obtainable from Aeromonas salmonicida strain NCIMB 40736 or NCIMB 40737.
8. A composition comprising a vaccine and the protein according to any one of claims 1 to 7, and optionally a suitable carrier, excipient or diluent.
9. A composition comprising a vaccine and the protein according to any one of claims 1 to 8, wherein the protein is present in an amount of from about 0.0008 %w/v to about 0.003 %w/v, preferably about 0.0015 %w/v, in the composition.
10. A composition according to claim 8 or claim 9, wherein the vaccine is a vaccine for a fish, preferably wherein the fish is a Salmonid.
1 1. A composition according to claim 10, wherein the Salmonid is salmon, preferably Atlantic salmon.
12. A composition according to any one of claims 8 to 1 1, wherein the vaccine is for immunising against furunculosis.
13. A composition according to claims 8 to 12, wherein the furunculosis is caused by Aeromonas salmonicida.
14. Aeromonas salmonicida strain S9 (NCIMB 40736)
15. Aeromonas salmonicida strain S21 (NCIMB 40737)
16. A protein according to any one of claims 1 to 7 or a composition according to any one of claims 8 to 13 for use in or as a vaccine composition for immunising an animal.
17. Use of a protein according to any one of claims 1 to 7 in the manufacture of a vaccine composition for immunising an animal.
18. Use of a protein according to any one of claims 1 to 7 to suppress the cellular immune response in an animal, preferably when the protein is present in a vaccine composition.
19. The invention according to any one of claims 8 to 18 wherein the vaccine composition is suitable for oral administration to the animal.
20. The invention according to any one of claims 8 to 18, wherein the animal is an animal as defined in claim 10 or claim 11.
21. Use of the protein according to any one of claims 1 to 7 in a vaccine composition to enhance the resistance to fish to furunculosis.
22. A method for enhancing the resistance of fish to furunculosis, wherein the protein according to any one of claims 1 to 7 is administered to fish.
23. A protein substantially as hereinbefore described.
24. A vaccine composition substantially as hereinbefore described.
PCT/GB1996/003249 1995-12-22 1996-12-23 Vaccine component WO1997023503A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU12054/97A AU1205497A (en) 1995-12-22 1996-12-23 Vaccine component

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9526433A GB2308367B (en) 1995-12-22 1995-12-22 Aeromonas protein used as a vaccine component
GB9526433.9 1995-12-22

Publications (1)

Publication Number Publication Date
WO1997023503A1 true WO1997023503A1 (en) 1997-07-03

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AU (1) AU1205497A (en)
GB (1) GB2308367B (en)
WO (1) WO1997023503A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002040515A2 (en) * 2000-11-15 2002-05-23 Universität Bern Exoenzyme toxin of aeromonas salmonicida, and uses thereof

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NZ578541A (en) 2006-12-22 2012-04-27 Soluciones Biotecnologicas Innovacion Ltda Dna vaccines for fish

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0384323A1 (en) * 1989-02-20 1990-08-29 Taito Co., Ltd. Composition and process to enhance the efficacy of a fish vaccine
WO1992021370A1 (en) * 1991-06-07 1992-12-10 The Secretary Of State For Scotland In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Fish vaccine for aeromonas salmonicida infection

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0384323A1 (en) * 1989-02-20 1990-08-29 Taito Co., Ltd. Composition and process to enhance the efficacy of a fish vaccine
WO1992021370A1 (en) * 1991-06-07 1992-12-10 The Secretary Of State For Scotland In Her Britannic Majesty's Government Of The United Kingdom Of Great Britain And Northern Ireland Fish vaccine for aeromonas salmonicida infection

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2002040515A2 (en) * 2000-11-15 2002-05-23 Universität Bern Exoenzyme toxin of aeromonas salmonicida, and uses thereof
WO2002040515A3 (en) * 2000-11-15 2002-12-27 Joachim Frey Exoenzyme toxin of aeromonas salmonicida, and uses thereof
GB2389112A (en) * 2000-11-15 2003-12-03 Joachim Frey Novel exoenzyme toxin of aeromonas salmonicida, and uses therefor
US7351550B2 (en) 2000-11-15 2008-04-01 Universitat Bern Exoenzyme toxin of Aeromonas salmonicida, and uses thereof
US7579011B2 (en) 2000-11-15 2009-08-25 Universitat Bern Exoenzyme toxin of Aeromonas salmonicida, and uses therefor
US7851197B2 (en) 2000-11-15 2010-12-14 Universitat Bern Exoenzyme toxin of Aeromonas salmonicida, and uses therefor

Also Published As

Publication number Publication date
GB2308367B (en) 1999-10-13
GB2308367A (en) 1997-06-25
AU1205497A (en) 1997-07-17
GB9526433D0 (en) 1996-02-21

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