WO2009080767A1

WO2009080767A1 - Fish vaccine

Info

Publication number: WO2009080767A1
Application number: PCT/EP2008/068063
Authority: WO
Inventors: Laura Labrie; Fong Sian Wong
Original assignee: Intervet International B.V.
Priority date: 2007-12-21
Filing date: 2008-12-19
Publication date: 2009-07-02
Also published as: CN101903042A; KR20100108373A; TW200936759A; JP2011506577A

Abstract

The present invention relates to a Nocardia-free combination vaccine for combating bacterial infection in fish, to the use of bacteria for the manufacture of such a vaccine, to methods for the preparation of such a vaccine and to a kit-of-parts.

Description

Fish vaccine

The present invention relates to a Nocardia-fτee combination vaccine for combating bacterial infection in fish, to the use of bacteria for the manufacture of such a vaccine, to methods for the preparation of such a vaccine and to a kit-of-parts.

Over the last decades, world- wide a strong increase is seen in the consumption of fish. This equally regards the consumption of cold water fish such as salmon, turbot, halibut and cod, and tropical fish such as Asian sea bass, tilapia, milkfish, yellowtail, amberjack, grouper, snapper and cobia.

As a consequence, an increase has been seen in the number and the size of fish farms, in order to meet the increasing needs of the market.

As is known from e.g. animal husbandry, large numbers of animals living closely together are vulnerable to all kinds of diseases, even diseases hardly known or seen, or even unknown, before the days of large-scale commercial farming. This is equally the case in fish farming. Bacteria found to be pathogenic to fish belong i.a. to the genus Nocardia, Vibrio, Pasteurella, Photobacterium, Tenacibaculum, Flavobacterium, Flexibacter, Cytophaga, Francisella, Mycobacterium, Streptococcus, Lactococcus or Edwardsiella.

Of the Nocardia species, Nocardia seriolae causes chronic problems in warm- water fish. The damage caused in fish farming industry by Nocardial infection has been increasing over the years. In particular yellowtail {Seriolae quinqueradiata), amberjack {Seriolae dumerellϊ), sea bass {Lateolabrax japonicus), yellow croacker {Lamitichthys crocea), Pomfret (Pampus argenteus), Threadfin {Eleutheronema tetradactylum), Snapper (Lutjanus sp), Grouper

(Epinephelus sp) and Trevalli, (Caranx sexfasciatus) have been affected by Nocardia infection.

The disease, often referred to as marine nocardiosis begins as a silent infection. It develops in fry and juvenile fish. The bacteria multiply within major organs such as spleen, liver and kidney.

Because of the low multiplication rate, the bacterium can multiply in fish tissue for a long time before any visual symptoms arise. Therefore, the disease is called chronic. Economic losses are significant, if only for the fact that as a consequence fish weigh often between 300 and 1000 g when the outbreak becomes manifest.

Research indicates that yellowtail sharing tank space with sick juveniles (previously injected with live Nocardia) eventually exhibit internal pathology (white spots in their spleens) after 3 months of cohabitation. In marine finfish culture, Nocardial infections appear to progress more quickly during the summer months when water temperatures reach 24°C or more, but the mortality due to Nocardia is more commonly experienced in the autumn and early winter months, as the fish has to adapt to the new environmental situation and its immune system wanes.

Nocardia seems to be a very poor inducer of the immune system itself, because in spite of the very slow progress of the disease, the immune system does not manage to clear the infection. This may also explain the fact that no efficacious vaccines against Nocardia infection exist. Vaccines comprising live attenuated or inactivated bacteria to a certain extent mimic the natural infection, but if even the natural infection fails to induce an adequate immune response, one would not expect vaccines to perform better.

It is clear that efficacious vaccines are highly needed.

It is an objective of the present invention to provide better vaccines for combating Nocardia infection.

It was surprisingly found now that a Nocardia-fτee combination vaccine comprising bacteria of the species Lactococcus garviae, Pasteurella piscicida (also known as Photobacterium damselae subspecies piscicidae) and Vibrio anguillarum (currently also known as Listonella anguillarum) , not only provides protection against Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum infection as expected, but also and fully unexpectedly provides a significant level of protection against Nocardia seriolae infection. Most surprisingly, this level of protection against Nocardia seriolae infection is significantly higher than that obtained by a monovalent Nocardia seriolae vaccine.

Therefore, a first embodiment of the present invention relates to a Nocardia-fτee combination vaccine for combating Nocardia infection in fish, characterised in that said vaccine comprises bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum and a pharmaceutically acceptable carrier. The working mechanism behind this unexpected finding is currently unknown. It is assumed however that a component present on or attached to the cell surface of the bacteria used, is a powerful stimulator of cross-specific immunity in fish against Nocardia. Cross-specific in this respect means: not induced by Nocardia but nevertheless providing protection against Nocardia.

For the manufacture of such a vaccine, the status of the bacteria; live or inactivated, is not really important. What counts is the fact that the stimulator of cross-specific immunity in fish against Nocardia is still present. This can be i.a. assured by using whole bacterial preparations. As said above, it is not important that the bacteria in the preparation are alive, killed or even fragmented (e.g. by pressing it through a French Press).

The skilled person will appreciate that the method used for inactivation is not very relevant for the activity of the bacteria. Classical methods for inactivation such as UV-radiation, gamma- radiation, treatment with formalin, binary ethylene-imine, thimerosal and the like, all well-known in the art, are applicable. Inactivation of bacteria by means of physical stress, using e.g. a French Press provides an equally suitable starting material for the manufacturing of a vaccine according to the invention. Inactivated bacteria need thus not necessarily be in the form of inactivated whole cells; the cells may be disrupted. Inactivated bacteria have the advantage over live attenuated bacteria that they are very safe.

Therefore, in a preferred form of this embodiment, the invention relates to a combination vaccine according to the invention wherein the bacterial species are inactivated

Live attenuated bacteria are also very suitable, because they by definition carry the factor stimulating the cross-specific immunity against Nocardia. And live attenuated bacteria have the advantage over inactivated bacteria that, especially when given without an adjuvant, they are more effective than inactivated bacteria. Moreover they replicate to a certain extent until they are stopped by the immune system, as a result of which a lower number of cells can be given. A live attenuated bacterium is a bacterium that is less pathogenic than its wild-type counterpart, but nevertheless induces an efficacious immune response. Attenuated strains can be obtained along classical routes, long known in the art such as serial passage, temperature-adaptation, chemical mutagenesis, UV-radiation and the like, or by site- directed mutagenesis.

Therefore, in another preferred form, the invention relates to a combination vaccine according to the invention wherein at least one of the bacterial species is in a live attenuated form.

Vaccines according to the invention can be prepared starting from a bacterial culture according to techniques well known to the skilled practitioner.

Review articles relating to fish vaccines and their manufacture are i.a. by Sommerset, L, Krossøy, B., Biering, E. and Frost, P. in Expert Review of Vaccines 4: 89-101 (2005), by Buchmann, K., Lindenstrøm, T. and Bresciani, in J. Acta Parasitologica 46: 71-81 (2001), by Vinitnantharat, S., Gravningen, K. and Greger, E. in Advances in veterinary medicine 41: 539-550 (1999) and by Anderson, D.P. in Developments in Biological Standardization 90: 257-265 (1997).

Vaccines according to the invention basically comprise an effective amount of bacteria according to the invention and a pharmaceutically acceptable carrier.

The term "effective " as used herein is defined as the amount sufficient to induce an immune response in the target fish that results in a level of pathogenesis that is less that 50% of the pathogenesis seen in non-vaccinated fish under the same conditions, and infected with wild-type Nocardia.

The amount of cells to be administered will depend i.a. on the amount of bacteria of each species used, the condition of the bacteria; attenuated live or inactivated, the presence of an adjuvant and the route of administration.

When starting from commercially available vaccines, the manufacturer will provide this information. Otherwise, man skilled in the art finds sufficient guidance in the references mentioned above and in the information given below, especially in the Examples. As said above, vaccines according to the invention can be prepared starting from a bacterial culture according to techniques well known to the skilled practitioner. In the Example-section, examples of the preparation of a vaccine according to the invention are given.

Generally spoken, vaccines manufactured according to the invention that are based upon inactivated bacteria can be given in general in a dosage of 10³ to 10¹⁰, preferably 10⁶ to 10⁹, more preferably between 10⁸ and 10⁹ bacteria. A dose exceeding 10¹⁰ bacteria, although immunologically suitable, will be less attractive for economical reasons. Vaccines manufactured according to the invention that are based upon live attenuated bacteria can be given in a lower dose, due to the fact that the bacteria will continue replicating for a certain time after administration. Vaccines manufactured according to the invention that are based upon live attenuated bacteria can be given in general in a dosage of 10² to 10⁸, preferably 10³ to 10⁵ bacteria

Examples of pharmaceutically acceptable carriers that are especially suitable in a vaccine according to the invention are sterile water, saline, aqueous buffers such as PBS and the like. In addition a vaccine according to the invention may comprise other additives such as adjuvants, stabilisers, anti-oxidants and others, as described below.

Vaccines manufactured as described in the present invention may in a preferred presentation contain an immunostimulatory substance, a so-called adjuvant. Adjuvants in general comprise substances that boost the immune response of the host in a non-specific manner. A number of different adjuvants are known in the art. Examples of adjuvants frequently used in fish and shellfish farming are muramyldipeptides, lipopolysaccharides, several glucans and glycans and Carbopol(R). An extensive overview of adjuvants suitable for fish and shellfish vaccines is given in the review paper by Jan Raa (Reviews in Fisheries Science 4(3): 229-288 (1996)).

The vaccine may also comprise a so-called "vehicle". A vehicle is a compound to which the bacterium adheres, without being covalently bound to it. Such vehicles are i.a. bio-microcapsules, micro-alginates, liposomes and macrosols, all known in the art. A special form of such a vehicle, in which the antigen is partially embedded in the vehicle, is the so-called ISCOM (European Patents EP 109.942, EP 180.564, EP 242.380).

In addition, the vaccine may comprise one or more suitable surface-active compounds or emulsifiers, e.g. Span or Tween. Thus, in a more preferred form of this embodiment, the combination vaccine according to the invention comprises an adjuvant.

For combination vaccines according to the invention, oil adjuvants usually turn out to be somewhat more efficient.

Oil adjuvants suitable for use in water-in-oil emulsions are e.g. mineral oils or metabolisable oils. Mineral oils are e.g. Bayol^®, Marcol^® and Drakeol^®.

Metabolisable oils are e.g. vegetable oils, such as peanut oil and soybean oil, animal oils such as the fish oils squalane and squalene, and tocopherol and its derivatives.

Suitable adjuvants are e.g. w/o emulsions, o/w emulsions and w/o/w double-emulsions

Very suitable o/w emulsions are e.g. obtained starting from 5-50% w/w water phase and 95-50% w/w oil adjuvant, more preferably 20-50% w/w water phase and 80-50% w/w oil adjuvant.

Thus, in an even more preferred form of this embodiment, the combination vaccine according to the invention comprises an adjuvant, wherein that adjuvant is an oil adjuvant.

As said above, oil adjuvants can roughly be divided in adjuvants comprising mineral oil and adjuvants comprising non-mineral oil. Mineral oil may be somewhat less attractive, both from a food safety point of view and due to the lesions it sometimes gives. Therefore, a preferred oil adjuvant comprises a non-mineral oil.

A more preferred non-mineral oil is e.g. ISA 763A VG oil as commercially obtainable from SEPPIC France

The amount of adjuvant added depends on the nature of the adjuvant itself, and information with respect to such amounts will be provided by the manufacturer.

Often, the vaccine is mixed with stabilisers, e.g. to protect degradation-prone proteins from being degraded, to enhance the shelf- life of the vaccine, or to improve freeze-drying efficiency. Useful stabilisers are i.a. SPGA (Bovarnik et al; J. Bacteriology 59: 509 (1950)), carbohydrates e.g. sorbitol, mannitol, trehalose, starch, sucrose, dextran or glucose, proteins such as albumin or casein or degradation products thereof, and buffers, such as alkali metal phosphates.

Preferably, vaccines as described are presented in a freeze-dried form.

In addition, the vaccine may be suspended in a physiologically acceptable diluent.

It goes without saying, that other ways of adjuvating, adding vehicle compounds or diluents, emulsifying or stabilising a protein are also embodied in the present invention.

Many ways of administration, all known in the art can be applied. The vaccines as described are preferably administered to the fish via injection such as e.g. intraperitoneal injection, immersion, spraying, dipping or per oral. It should be kept in mind however that the route of administration may also depend on the type of vaccine: if the vaccine comprises live attenuated Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria, it could easily be administered by dipping. If on the other hand the vaccine comprises Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria in the form of inactivated bacteria, or more generally spoken if the vaccine can be improved by admixing an adjuvant, the preferred way of administration would be the intraperitoneal route. From an immunological point of view, intraperitoneal vaccination is an effective route of vaccination in fish, certainly for inactivated bacteria, especially because it allows the incorporation of adjuvants.

A convenient way of making a vaccine according to the invention is, to make use of commercially available vaccines. Lactococcus garviae vaccines, Pasteurella piscicida vaccines and Vibrio anguillarum vaccines are commercially available, and/or ways to produce them have been described in the literature.

The administration protocol can be optimized in accordance with standard vaccination practice.

The age of the fish to be vaccinated is not critical, although clearly one would want to vaccinate against Nocardia infection in an early stage. For many fish vaccines it goes that they are administered when the fish have a weight of between 10 and 35 grams. This is a very suitable moment for vaccinating against Nocardia as well. For oral administration the vaccine is preferably mixed with a suitable carrier for oral administration i.e. cellulose, food or a metabolisable substance such as alpha-cellulose or various oils of vegetable or animals origin. Also an attractive method is administration of the vaccine through bio encapsulation whereby live feed is exposed to high concentrations of the vaccine, followed by the feeding of the live- feed organisms to the fish. Particularly preferred food carriers for oral delivery of the vaccine according to the invention are live-feed organisms which are able to encapsulate the vaccine. Suitable live-feed organisms include plankton-like non-selective filter feeders preferably members of Rotifera, Artemia, and the like. Highly preferred is the brine shrimp Artemia sp..

In view of the large number of viruses and organisms pathogenic to fish, it would be beneficial to administer, together with Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria, also one or more other non-Nocardia fish-pathogenic bacteria or viruses, antigens of those bacteria or viruses or genetic material encoding such antigens for the manufacture of a vaccine.

Examples of notorious commercially important fish pathogens are the recently found bacterium causing Big Belly syndrome, as described in Thai Patent Application TH 92840, (An example of this novel bacteria (BB E3F1) has been deposited with the Collection Nationale de Cultures de Microorganisms (CNCM), Institut Pasteur, 25 Rue du Docteur Roux, F-75724 Paris Cedex 15, France, under accession number CNCM 1-3257), Tenacibaculum maritimum, Flavobacterium columnare, Flexibacter maritimus (the old name of Tenacibaculum maritimum), Streptococcus iniae, Streptococcus difficile, Streptococcus agalactiae, Streptococcus dysgalactiae, Edwardsiella tarda, Edwardsiella ictaluri, Mycobacterium maritimum, Francisella sp. as well as viruses such as Nodavirus, Irido virus, Koi herpes virus, Channel Catfish virus.

The advantage of such a combination vaccine is that it not only provides protection against Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum infection as well as Nocardia infection, but also against other diseases.

Therefore, in a preferred embodiment, the Nocardia-fτee combination vaccine according to the invention comprises, in addition to bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum, at least one other microorganism or virus that is pathogenic to fish, or one other antigen of such a microorganism or virus or genetic material encoding said other antigen.

In a more preferred embodiment, at least one other microorganism that is pathogenic to fish, or one other antigen of such a microorganism or genetic material encoding said other antigen are selected from the group of bacteria consisting of the bacterium causing Big Belly syndrome, Flavobacterium columnare, Tenacibaculum maritimum, Streptococcus iniae, Streptococcus difficile, Streptococcus agalactiae, Streptococcus dysgalactiae, Edwardsiella tarda, Edwardsiella ictaluri, Mycobacterium maritimum, Francisella sp., Nodavirus, Irido virus, Koi herpes virus, Channel Catfish virus.

Still another embodiment of the present invention relates to methods for the production of vaccines for combating Nocardia infection in fish. Such methods comprise the step of mixing of Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria in a live attenuated or inactivated form and a pharmaceutically acceptable carrier.

A preferred form of this embodiment relates to methods that additionally comprise the mixing of an adjuvant.

If for the Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum vaccine components, ready-to-use vaccines are used, they can be mixed before administration.

If they are to be administrated orally, mixing prior to administration would be the preferred choice. If the vaccine is administered by injection, for simultaneous administration the components can be mixed, they can also be administered separately or sequentially in a series of consecutive injections.

Regardless the fact that either commercially available Lactococcus garviae vaccines, Pasteurella piscicida vaccines and Vibrio anguillarum vaccines or vaccines prepared as described in the Examples are used, the skilled person would prefer to use that amount of each of the bacteria that is necessary to induce an immune response against each of the bacterial species. Merely as an example: the amount of Lactococcus garviae bacteria in the Nocardia-fτee vaccine according to the invention preferably is sufficient to induce an immune response against Lactococcus garviae infection. The bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum in the combination vaccine can be administered simultaneously, separately or sequentially. They can then, if given within a short interval, nevertheless be considered as a combination vaccine, as is explained below. Simultaneous administration is administration of the Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria at the same moment in time, preferably injected as a mixture. This would of course be the preferred method of administration, due to ease of handling. Separate administration is administration of the Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria (partially or fully) separately at two or more different injection sites, preferably at the same moment in time.

Sequential administration is administration during which the Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum bacteria are administered at different moments in time. It is clear that if separate or sequential injections are given, these would preferably be given at the same day, more preferably within 12, 10, 8, 6, 4, 2 or 1 hour in that order of preference. Even more preferred is administration within 50, 40, 30, 20, 10 or 5 minutes after each other. If the administration of all vaccines of the combination vaccine would take place within 10 minutes, even better 5 or less than 5 minutes, a single moment for handling of each fish would suffice, and would allow an almost instantaneous start of triggering of the immune system.

Another embodiment of the present invention relates to the use of bacteria of at least the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum for the manufacture of a Nocardia-fτee combination vaccine for combating Nocardia seriolae infection in fish.

In a preferred form of this embodiment, the fish in which the Nocardia seriolae infection is to be combated, and for which the vaccine is thus manufactured belongs to the species yellowtail

(Seriolae quinqueradiata), amberjack (Seriolae dumerellϊ), sea bass (Lateolabrax japonicus), yellow croacker (Lamitichthys crocea), Pomfret (Pampus argenteus), Threadfin (Eleutheronema tetradactylum), Snapper (Lutjanus sp), Grouper (Epinephelus sp) or Trevalli, (Caranx sexfasciatus) .

In another preferred form of this embodiment, at least one of the bacterial species used for the manufacture is in a live attenuated form. In still another preferred form of this embodiment, the bacterial species used for the manufacture are inactivated.

In a more preferred form of this embodiment, for the manufacture of said vaccine additionally at least one other microorganism or virus that is pathogenic to fish, or one other antigen of such a microorganism or virus or genetic material encoding said other antigen is used.

In an even more preferred form of this embodiment said other microorganism or virus is selected from the group of bacteria consisting of the bacterium causing Big Belly syndrome, Tenacibaculum maritimum, Flavobacterium columnare, Streptococcus iniae, Streptococcus difficile, Streptococcus agalactiae, Streptococcus dysgalactiae, Edwardsiella tarda, Edwardsiella ictaluri, Mycobacterium maritimum, Francisella sp., Nodavirus, Irido virus, Koi herpes virus and Channel Catfish virus.

Finally, another embodiment relates to a kit of parts, wherein the kit comprises at least two vaccine vials, and these at least two vials together comprise bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum and a pharmaceutically acceptable carrier for combating Nocardia seriolae infection in fish. Merely as an example: if the kit comprises two vials together comprising bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum, this means that each of these three types of bacteria are present in at least one of the vials. As a result the three types of bacteria are all present in the kit. In this example, one vial could comprise Lactococcus garviae, whereas the other vial comprises Pasteurella piscicida and Vibrio anguillarum. Alternatively, one vial could comprise Lactococcus garviae and Pasteurella piscicida, whereas the other vial could comprise Vibrio anguillarum. If the kit comprises e.g. three vials, each type of bacteria can be present in one vial.

Examples. Example 1 Animal husbandry: Test system

Animals

Species: Yellowtail (Seriola quinqueradiata) Source: Wild caught fingerlings

Av. weight at start of Exp. approx. 2Og (18-27g)

Since the fish were wild-caught fingerlings they were free from any previous vaccinations. The fish were placed in a quarantine tank upon arrival until they obtained the correct size for the experiment.

Inclusion-exclusion criteria

Only healthy animals were used. After vaccination, no treatment of sick animals or exclusion of animals was performed.

Water

^■ Salinity: natural sea water 25 - 35 ppt

^■ Temperature: 24⁰C +/- 2°C after vaccination,

26°C +/- 2°C after challenge

Feed

During the pre-treatment period, feed was given ad libitum several times per day. As soon as a sufficient number of fish reached the desired weight of approximately 20 g and were shown to be free of infections they were transferred to experimental tanks. During the experimental period (after vaccination) the fish were fed at 2-3% of their body weight (BW) (adjusted weekly). The amount of feed per Kg body weight was kept as similar as possible for vaccinated and mock-vaccinated fish. At weekly intervals, 10-15 fish per group were weighed in groups to determine the mean fish weight for the recalculation of the feed amount. Fish were starved for 24 hours prior to the vaccination to ensure complete emptying of the gastro-intestinal tract and thereby preventing injury to the internal organs as a result of the injection. After challenge fish were fed 1-3% BW.

Tanks

At the start of the experiment the fish were grouped, vaccinated or mock-vaccinated and subsequently transferred to 500 L tanks. Groups of fish were separated by means of a net placed vertically in the middle of the tank, dividing the tank in two halves. Tank halves were identified by the tank number and a letter (A or B). After challenge fish were housed in 50 L tanks.

Grouping and Dosing

Vaccination

Vaccination was performed by IP injection on the side of the fish, approximately at the end of the pectoral fin. Small hypodermic, single use needles and single use syringes were used. Control fish were mock vaccinated with SVDB (Standard Vaccine Dilution buffer = PBS).

Challenge

Preparation of challenge material

Challenge seed of a wild-type Nocardia seriolae was taken from the <-50°C freezer and allowed to thaw. The contents of the vial was inoculated into Eugon Broth at a rate of 1% (v/v), incubated at 26°C on an orbital shaker with a shaking speed set at 150 RPM for app 67-71h. The OD_660nm of the culture typically was 1.5-1.6 corresponding to an approximate viable cell count of 10⁸ CFU per ml.

This suspension representing a late log phase was used to prepare the challenge suspension. An appropriate dilution was performed in saline and used for injection.

Challenge

Challenge was performed by IP injection. From the experimental groups, fish were injected with 0.1 ml of the standardised bacterial suspensions. Each group was anaesthetized in AQUI-S until sedated and injected intra-peritoneally on the left side of the body just behind the tip of the pectoral fin. Immediately after injection the fish were transferred to their allocated tank and recovery was followed. The fish were starved for 24h prior to challenge to ensure the complete emptying of the gastro-intestinal tract.

EVALUATION OF RESULTS

The results of the challenges performed for each of the vaccine formulations was evaluated by calculating the Relative Percentage Survival (RPS) values for each group as compared to the control group the day that control mortality reached 60% or more. In addition, statistical analysis was performed on final confirmed cumulative mortality between treatment groups and respective controls using a 2x2 contingency table and Fisher's exact test (One tailed, Stat Soft Inc (2004), Statistica, data analysis Software system, version 6).

The RPS values are calculated according to the following formula:

[ % mortality in vaccinated

RPS = \ 1 - ( ) x 100

I % mortality in controls

The antigen concentration in the Examples will often be given in ODU/ml. The ODU/ml is determined as follows: Antigen Concentration (ODU/ml) = (((OD₆₆o)-l + (OD₆₆₀).2)/2)- 0.2118)/0.0018 * DF * 10⁶, wherein (OD₆₆₀).1 + (OD₆₆₀).2 are the OD₆₆₀ values of two OD₆₆₀ measurements and wherein DF is the dilution factor.

AU monovalent vaccines described here were derived from a formalin inactivated N. seriolae antigens and formulated as oil adjuvanted vaccines. The vaccines Vl and V2 were injected using an injection volume of 0.05. The vaccines V3, V4 and V5 were injected after mixing equal volumes of vaccine with vaccine diluent and injection of 0. ImI.

Test articles

Vaccine 1: Type: Monovalent N. seriolae /oil adjuvanted

Formulation 1.OxIO⁷ ODU/ml (5.OxIO⁵ ODU/fish)

Vaccine 2: Type: Monovalent N. seriolae I oil adjuvanted

Formulation 1.OxIO⁶ ODU/ml (5.OxIO⁴ ODU/fish)

Vaccine 3: Type: Monovalent N. seriolae /oil adjuvanted

Formulation 1.OxIO⁷ ODU/ml (5.OxIO⁵ ODU/fish) Vaccine 4: Type: Monovalent N. seriolae I oil adjuvanted

Formulation LOxIO⁶ ODU/ml (5.OxIO⁴ ODU/fish)

Vaccine 5: Type: Monovalent N. seriolae I oil adjuvanted

Formulation 1.OxIO⁵ ODU/ml (5.OxIO³ ODU/fish)

Vaccine Diluent

Type: Standard Vaccine dilution buffer in oil

SVDB

Type: Standard vaccine dilution buffer (SVDB)

The vaccine formulations tested are listed in Table 1. The vaccines are water in oil vaccines formulated as a micro component and mixed with ISA 763A VG oil- vaccine diluent before use.

Table 1. Treatment groups, number of fish for challenges performed at week 3 and week 6.

RPS VALUES

Table 2. RPSβo values of week 3 and week 6 challenges in different vaccine conditions in the minimum antigen trials.

As follows from table 2, survival of vaccinated fish was not significant different from controls (One tailed Fisher exact, p<0.05). Relative percentage of survival and mortality rate for both the vaccinated groups and the control groups are statistically not different.

Example 2

Animal husbandry: Test system

Animals

As for example 1 Inclusion-exclusion criteria

As for example 1

Water

As for example 1 Feed As for example 1

Tanks

As for example 1 Grouping and Dosing

Vaccination

As for example 1 Challenge Preparation of challenge material

As for example 1 Challenge

As for example 1

EVALUATION OF RESULTS

As for example 1

Test articles

Vaccines

Vaccine :

Type: trivalent V. anguillarum/L. garvieae 6.8x10⁸ cells/ml, P. piscicida 1.36x10⁹ cells/ml Injection: 0.1 ml

The vaccine formulations tested are listed in Table 3. The vaccine was a water in oil vaccine formulated as a micro component and was mixed with ISA 763A VG oil- vaccine diluent before use. The antigen used for these vaccines are derived from the normal production strains of P. piscicida, L. garvieae and V anguillarum.

Table 3 : Experimental groups, vaccines used, allocated tank halves after vaccination and challenge.

RPS VALUES

RPS after N senolae challenge (n=15). The asteπsk * indicates statistical differences between vaccinates and controls (One tailed Fisher exact, p<0.05)). Control mortality obtained upon calculation of RPS was 73%.

Table 4 RPSβo values after challenge

10 Statistical analysis

Group RPS

Vaccine 73% P=O 0046*

Control mortality 72%

From this expeπment, table 4, it follows that the relative percentage of survival of the vaccinated group is 73%, whereas at that moment in the control group > 60 % of the fish were dead (actually 72% mortality in the control group). Thus, it can be concluded that vaccines compπsing P piscicida, L garvieae and V anguillarum are able to protect fish against Nocardia infection.

Claims

1) Nocardia-fτee combination vaccine for combating Nocardia infection in fish, characterised in that said vaccine comprises bacteria of the species Lactococcus garviae,

Pasteurella piscicida and Vibrio anguillarum and a pharmaceutically acceptable carrier.

2) Nocardia-fτee combination vaccine according to claim 1, characterised in that at least one of the bacterial species is in a live attenuated form.

3) Nocardia-fτee combination vaccine according to claim 1, characterised in that the bacterial species are inactivated.

4) Nocardia-fτee combination vaccine according to claim 1-3, characterised in that it comprises an adjuvant.

5) Nocardia-fτee combination vaccine according to claim 4, characterised in that the adjuvant is an oil adjuvant. 6) Nocardia-fτee combination vaccine according to claim 4 or 5, characterised in that the adjuvant is a non-mineral oil adjuvant.

7) Nocardia-fτee combination vaccine according to claim 4-6, characterised in that the adjuvant is ISA 763A VG.

8) Nocardia-fτee combination vaccine according to claims 1 -7, characterized in that said vaccine comprises at least one other microorganism or virus that is pathogenic to fish, or one other antigen of such a microorganism or virus or genetic material encoding said other antigen.

9) Nocardia-fτee combination vaccine according to claim 8, characterised in that said at least one other microorganism or virus is selected from the group consisting of the bacterium causing Big Belly syndrome, Tenacibaculum maritimum, Flavobacterium columnare, Streptococcus iniae, Streptococcus difficile, Streptococcus agalactiae, Streptococcus dysgalactiae, Edwardsiella tarda, Edwardsiella ictaluri, Mycobacterium maritimum, Francisella sp., Nodavirus, Irido virus, Koi herpes virus or Channel Catfish virus. 10) Method for the preparation of a Nocardia-fτee combination vaccine according to claim 1 -

9, characterised in that said method comprises the steps of mixing bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum and a pharmaceutically acceptable carrier. 11) Use of bacteria of at least the species Lactococcus garviae, Pasteur ella piscicida and Vibrio anguillarum for the manufacture of a Nocardia-fτee combination vaccine for combating Nocardia seriolae infection in fish.

12) Use according to claim 11 characterised in that the fish belong to the species yellowtail {Seriolae quinqueradiata), amberjack {Seriolae dumerellϊ), sea bass {Lateolabrax japonicus) or yellow croacker {Lamitichthys crocea).

13) Use according to claim 11 or 12, characterised in that at least one of the bacterial species is in a live attenuated form.

14) Use according to claim 11 or 12, characterized in that said bacterial species are inactivated.

15) Use according to claims 11-14, characterized in that for the manufacture of said vaccine additionally at least one other microorganism or virus that is pathogenic to fish, or one other antigen of such a microorganism or virus or genetic material encoding said other antigen is used. 16) Use according to claim 15, characterized in that said other microorganism or virus is selected from the group consisting of the bacterium causing Big Belly syndrome, Tenacibaculum maritimum, Flavobacterium columnare, Streptococcus iniae, Streptococcus difficile, Streptococcus agalactiae, Streptococcus dysgalactiae, Edwardsiella tarda, Edwardsiella ictaluri, Mycobacterium maritimum, Francisella sp., Nodavirus, Irido virus, Koi herpes virus and Channel Catfish virus.

17) Kit of parts characterised in that the kit comprises at least two vaccine vials, said vials together comprising bacteria of the species Lactococcus garviae, Pasteurella piscicida and Vibrio anguillarum and a pharmaceutically acceptable carrier for combating Nocardia seriolae infection in fish.