BIOLOGICAL PREPARATIONS

Abstract: The present invention provides vaccines containing inactivated avian infectious bronchitis virus VLO 10110/AVI/9 and/or an inactivated virus strain serologically related there­ to the immune response to which in birds is enhanced by "priming" with a live heterologous strain of avian infectious bronchitis virus. Immunisation of poultry against infectious bronchitis using such a vaccine does not require initial vaccination or "priming" of the poultry with a live vaccine of the same strain, thus enabling "priming" to be effected using a well-tried conventional live heterologous vaccine, for example a live vaccine to an avian infectious bronchitis virus of the Massachusetts serotype.

Description: This invention relates to novel vaccines for immunising poultry against infectious bronchitis. Infectious bronchitis is a highly contagious respiratory disease of chickens which, in the case of laying hens, may also adversely affect egg production and quality. The use of infectious bronchitis vaccines for immunisation of poultry has now been established for many years. In general, the vaccines contain an infectious bronchitis virus of a particular serotype such as Connecticut or Massachusetts serotypes, the latter being more common in Great Britain and Europe. Combination of different infectious bronchitis serotypes has also been tried, but protection against the respective serotypes is not always optimal. More recently, inactivated infectious bronchitis vaccines containing variant, i.e. new serologically distinct, strains of infectious bronchitis virus have been introduced but they require poultry to be initially immunised or "primed" with a live vaccine; hitherto it has been believed that such "priming" had to be effected using a live vaccine comprising a virus of the same strain as the inactivated virus. We have now found that inactivated vaccines derived from a novel variant strain of avian infectious bronchitis virus and strains which cross-react with this particular variant strain offer protection against such serologically related variant strains and furthermore, immunisation with such vaccines surprisingly does not require initial vaccination or "priming" of the poultry with a live vaccine of the same strain. This enables "priming" to be effected using heterologous live vaccines which may be well tried, conventional live vaccines of established safety and effectiveness. The novel avian infectious bronchitis variant virus strain was isolated from broiler chickens and has been deposited at the Central Veterinary Laboratory, New Haw at Weybridge, United Kingdom registered under the number VLO 10110/AVI/9 and also at the Institut Pasteur, Paris, France registered under the number I-400 deposited on 11th December 1984. This strain, hereinafter referred to as VLO 10110/AVI/9, was shown in virus neutralisation tests to be related but not identical to the Dutch D207 strain but is distinct from the conventional viruses of the Massachusetts serotype commonly used in infectious bronchitis vaccines. By means of cross-neutralisation tests carried out in tracheal organ cultures, it was found that the isolate is not neutralised by antiserum to infectious bronchitis virus M41 or to the H120 vaccine strains of infectious bronchitis virus both of which are of the Massachusetts serotype. Table 1 summarises the results of the various virus neutralisation (VN) tests using the constant-virus variable-serum method. The results indicate that the new variant virus VLO 10110/AVI/9 is distinct serologically and does not belong to the Massachusetts serotype. The oil emulsion vaccines referred to in Table 1 contain the Massachusetts M41 strain and/or the VLO 10110/AVI/9 variant strain of avian infectious bronchitis virus. According to one feature of the invention, therefore, we provide novel vaccines containing inactivated avian infectious bronchitis virus VLO 10110/AVI/9 and/or an inactivated virus strain which cross-reacts significantly therewith, the immune response to which in birds is enhanced by "priming" with a live heterologous strain of avian infectious bronchitis virus. As indicated above, we have found that an inactivated vaccine based on the novel variant strain VLO 10110/AVI/9 of infectious bronchitis virus and/or a strain serologically related thereto does not require poultry to have been initially vaccinated or "primed" with a live vaccine of the same strain. Instead, and unexpectedly we have found that "priming" with a heterologous live vaccine based on a conventional strain (example H120 vaccine) is sufficient to ensure that subsequent vaccination with the vaccine based on the inactivated variant strain gives a boosted immune response. Thus we have found that "priming" with a live attenuated virus vaccine of the Massachusetts serotype such as a live vaccine to any conventional strain of the Massachusetts serotype H120, H52 or M41, or mild Massachusetts (MM) is sufficient to ensure that subsequent vaccination with the inactivated variant strain vaccine to VLO 10110/AVI/9 and/or serologically related strains gives a boosted immune response. The inactivated vaccines to the variant strain VLO 10110/AVI/9 and/or strains cross-reacting significantly therewith may be prepared by conventional means, for example by growing the virus in embryonated eggs. The infectious allantoic fluid having reached a suitable titre e.g. approximately 10 8.0 median ciliostatic doses/ml (8.0 log 10 CD₅₀/ml wherein CD₅₀/ml is as defined in J.K.A. Cook et. al., 1976 Archives of Virology, 50 , 109-118) may then be harvested and inactivated using inactivating agents such as formaldehyde or β-propiolactone. After inactivation the virus may be concentrated and the pH may be adjusted if necessary. The inactivated antigen in an aqueous medium may be mixed with an adjuvant such as aluminium hydroxide or incorporated into an oil emulsion comprising an oil, e.g. paraffin oil, an oil-soluble surfactant, and a water soluble surfactant, the ratio of oil to aqueous phase generally being in the range 2-5:1. Purified paraffin oils which may be used in an adjuvant emulsion include, for example, proprietary products such as Drakeol, Marcol or Puremore, though most grades of liquid paraffin are suitable. An oil such as squalane may also be employed. The most preferred ratio of oil to aqueous phase is about 4:1, the resulting emulsion being stable and of a suitable viscosity for injection. The oil-soluble surfactant is preferably a monoester of a sugar alcohol anhydride, for example sorbitan or mannitan, with a long-chain fatty acid such as oleic, stearic or lauric acid. Arlacel 80® or Span 80® (sorbitan mono-oleate) and Arlacel A® (mannitan mono-oleate) are particularly suitable. The water-soluble surfactant is preferably a polyoxyethylene derivative of a monoester of a sugar alcohol anhydride, such as sorbitan with a long-chain fatty acid such as lauric, oleic or stearic acid. The polyoxyethylene chain preferably contains about 20 oxyethylene units. Tween 80® (polyoxyethylene (20) sorbitan mono-oleate) is particularly suitable. The concentration of the oil-soluble surfactant in the oil phase is preferably in the range 8-12% (w/v), advantageously about 10% (w/v). The concentration of the water-soluble surfactant in the water-phase is preferably in the range of 4 to 4.5% (w/v), advantageously about 4.25% (w/v). The vaccine may advantageously contain inactivated virus obtained from 10⁶ to 10⁸ median ciliostatic doses (6 to 8 log 10 CD 50 ) of the variant strain VLO 10110/AVI/9 (and/or a serologically related strain) per dose of vaccine. The inactivated vaccines will usually be given to the birds at the point of lay at an age of approximately 16-20 weeks by subcutaneous or intramuscular injection, preferably by the intramuscular route. One dose of the inactivated vaccine is usually sufficient and may, for example, consist of 0.25 to 1.00 ml, e.g. 0.5 ml, of the above vaccine, such a dose advantageously containing the antigenic equivalent of 10 6 to 10 8 median cilostatic doses (6 to 8.0 log₁₀ CD₅₀)of the variant virus strain. The inactivated vaccines may contain, in addition to the inactivated variant strain VLO 10110/AVI/9 and/or a strain which cross-reacts significantly therewith one or more additional inactivated virus strains such as those of the Massachusetts serotype for example M41, other strains of infectious bronchitis virus or other viruses such as Newcastle disease virus, infectious bursal disease virus, adeno viruses such as EDS 76 virus, reoviruses, and other viruses. Thus, for example, such vaccines include a monovalent oil emulsion vaccine containing inactivated VLO 10110/AVI/9 alone, a bivalent oil emulsion vaccine containing both inactivated VLO 10110/AVI/9 and inactivated Massachusetts M41, a trivalent oil emulsion vaccine containing VLO 10110/AVI/9, inactivated Massachusetts M41 and Newcastle disease virus or a tetravalent oil emulsion vaccine containing VLO 10110/AVI/9, inactivated Massachusetts M41, Newcastle disease virus and infectious bursal disease virus. As indicated above, the recipients of the inactivated vaccines of the invention may be "primed" using a conventional live infectious bronchitis virus vaccine, for example live attenuated virus vaccine containing an avian infectious bronchitis virus of the Massachusetts serotype such as a live vaccine to a conventional H120, H52, M41 or MM virus. This is sufficient to ensure that subsequent vaccination with an emulsion variant strain vaccine gives a boosted immune response. Infectious bronchitis virus H120 vaccine is preferred as the "priming" vaccine, The "priming" vaccine is given to chickens at up to 12 weeks of age, preferably 3 weeks of age. In addition an optional second "priming" dose or further doses may be given. The vaccine may contain at least 3 log₁₀ median egg infectious doses (EID₅₀) of live attenuated avian infectious bronchitis virus per bird dose. The vaccine may be administered in the drinking water, by eye drop, intranasally or by aerosol spray. In general, the inactivated vaccine should be given at least 4 weeks, more preferably about 13 weeks, after the "priming" vaccine. According to a still further feature of the invention, we provide a kit comprising separately said inactivated virus and said live virus vaccines. The kit comprises multiple dosage units of each of the respective vaccines. Preferably, 500 or 1000 dosage units of each vaccine may be present in the kit. According to yet another feature of the invention, we provide the use of inactivated avian infectious bronchitis virus VLO 10110/AVI/9 and/or a strain cross-reacting significantly therewith, to prepare a vaccine for use in vaccinating birds against avian infectious bronchitis in combination with an initial vaccination with a live vaccine containing a live heterologous avian infectious bronchitis virus. The following examples illustrate the invention. Example 1 (a) Preparation of monovalent oil emulsion vaccine containing inactivated strain VLO 10110/AVI/9 Ten day old SPF embryonated chicken eggs were inoculated via the allantoic cavity with 3-4 log₁₀ CD₅₀ of infectious bronchitis virus strain VLO 10110/AVI/9. After 70 hours incubation at 37°C, the allantoic fluid was harvested. A preservative was added (0.013% thiomersal) and after clarification by low speed centrifugation, virus infectivity was inactivated by incubation with 0.05% β-propiolactone for 2 hours at 37°C. The inactivated allantoic fluid was concentrated by ultrafiltration such that it contained at least the equivalent of 10⁸ CD₅₀/ml. Polysorbate 80 was dissolved in the inactivated viral antigen preparation to a concentration of 4.25%. This was then mixed with a light mineral oil (USP) containing 10% sorbitan monooleate BP in the ratio of 1:4 and emulsified. The vaccine was stored at 4°C. (b) Immunisation One dose, containing at least 3 log₁₀ EID₅₀ of H120 live vaccine, was administered to chickens intranasally at 3 weeks of age. At 16 weeks of age 0.5 ml of the VLO 10110/AVI/9 oil emulsion vaccine (antigenic equivalent 7.0 log₁₀ CD₅₀) was administered to each bird intramuscularly. Mean haemagglutination inhibition (HI) antibody titres to M41 of 7.0 log₂ and to D274 of 8.3 log₂ were obtained 8 weeks after vaccination with the oil emulsion vaccine. Example 2 Preparation of bivalent oil emulsion vaccine containing inactivated strain VLO 10110/AVI/9 and strain M41 (a) Two batches of ten day old SPF embryonated chicken eggs were inoculated via the allantoic cavity with 3-4 log₁₀ CD₅₀ of infectious bronchitis virus strain VLO 10110/AVI/9 or strain M41. After 70-72 hours incubation at 37°C, the allantoic fluid from each batch of eggs was harvested separately. A preservative was added to each (0.013% thiomersal) and after clarification by low speed centrifugation, virus infectivity was inactivated by incubation with 0.05% β-propiolactone for 2 hours at 37°C. The two batches of inactivated allantoic fluid were concentrated by ultrafiltration. Polysorbate 80 was dissolved in the inactivated viral antigen preparations to a concentration of 4.25%. These were then mixed with a light mineral oil (USP) containing 10% sorbitan monooleate BP in the ratio 1:4 and emulsified. The two emulsions were then mixed together in equal volumes and the bivalent vaccine stored at 4°C. (b) Similarly, polyvalent vaccines may be prepared using the above technique but incorporating, in addition, inactivated Newcastle disease virus or inactivated Newcastle disease virus and infectious bursal disease virus. (c) Immunisation One dose, containing at least 3 log₁₀ CD₅₀ of H120 live vaccine was administered to chickens intranasally at 3 weeks of age. At 16 weeks of age 1ml of the bivalent oil emulsion vaccine of (a) above (antigenic equivalent 7.0 log₁₀ CD₅₀ of each virus strain) was administered to each bird intramuscularly. Mean haemagglutination inhibition (HI) antibody titres to M41 of >10.7 log₂ and D274 of 9.0 log₂ were obtained 8 weeks after vaccination with the oil emulsion vaccine. Example 3 Comparative test in "primed" and "unprimed" birds The monovalent oil emulsion vaccine prepared as in Example 1 above, or an equivalent M41 monovalent vaccine or a bivalent oil emulsion vaccine prepared as in Example 2(a) above containing both viral antigens was administered both to 16 week old chickens that had been "primed" with live H120 (a vaccine of the Massachusetts serotype widely used commercially) and to 16 week old chickens which had not been "primed". Haemagglutination inhibition (HI) antibody titres were measured at 4 and 8 weeks after vaccination. Boosted immune responses and relatively high antibody titres to the variant virus were found in birds vaccinated with the monovalent VLO 10110/AVI/9 or the bivalent oil emulsion vaccine which had previously been "primed" with the conventional H120 live vaccine. The antibody titres were considerably higher than the titres induced in "unprimed" birds. (See Table 2). It will be appreciated that the corresponding boosting of antibody titres in respect of the M41 virus when "primed" with H120 vaccine is conventional in that M41 and H120 are of the same serotype. Example 4 Hubbard Comet pullets were reared under commercial conditions on an isolated site. At 0, 4 and 8 weeks of age they were administered live H120 infectious bronchitis vaccine. At 15 weeks of age, serum samples were examined and shown to be free of antibodies to 'variant' strains of infectious bronchitis virus. The birds were transferred to individual bird laying cages in an isolation suite. Half the birds were vaccinated with the bivalent oil emulsion vaccine of Example 2 containing inactivated strain VLO 10110/AVI/9 + inactivated strain M41 and half received no further vaccine. Individual bird egg production including egg colour was recorded daily. At 30 weeks of age, the birds were challenged with a fine aerosol of strain VLO 10110/AVI/9. Vaccination of commercial pullets with a combination of live H120 and inactivated bivalent oil emulsion vaccine was successful in preventing the serious drop in egg production and adverse changes in shell quality that occurred in birds not so vaccinated when challenged at 30 weeks old.

Claims: Vaccines containing inactivated avian infectious bronchitis virus strain deposited with the Institut Pasteur under the accession number I-400 and/or an inactivated virus strain which cross-reacts significantly with said strain the immune response to which in birds is enhanced by priming with a live heterologous strain of avian infectious bronchitis virus. A vaccine as claimed in claim 1 wherein the inactivated avian infectious bronchitis virus is I-400. A vaccine as claimed in claim 1 or claim 2 wherein the inactivated antigen in an aqueous medium is mixed with aluminium hydroxide or an oil emulsion comprising an oil, an oil-soluble surfactant and a water-soluble surfactant. A vaccine as claimed in claim 3 which comprises as an adjuvant an oil emulsion wherein the oil is a paraffin oil or squalane. A vaccine as claimed in claim 3 or claim 4 which comprises as an adjuvant an oil emulsion wherein the ratio of oil to aqueous phase is about 4:1. A vaccine as claimed in any one of claims 1 to 5 which contains inactivated virus obtained from 6 to 8 log₁₀ CD₅₀ of the variant strain I-400 and/or said cross-reacting strain per dose of vaccine. A vaccine as claimed in any one of claims 1 to 6 which contains, in addition to inactivated avian infectious bronchitis virus strain I-400 and/or an inactivated virus strain which cross-reacts significantly with said strain, one or more additional inactivated virus strains. A vaccine as claimed in any of claims 1-7 which contains in addition to said inactivated avian infectious bronchitis virus I-400, inactivated avian infectious bronchitis virus M41. A vaccine as claimed in any of claims 1-7 which contains in addition to said inactivated avian infectious bronchitis virus I-400, inactivated avian infectious bronchitis virus M41 and inactivated Newcastle disease virus. A vaccine as claimed in any of claims 1-7 which contains in addition to said inactivated avian infectious bronchitis virus I-400, inactivated avian infectious bronchitis virus M41, inactivated Newcastle disease virus and inactivated infectious bursal disease virus. A kit comprising separately multiple dosage units of each of an inactivated vaccine containing inactivated avian infectious bronchitis virus strain I-400 and/or a virus strain which cross-reacts significantly with said strain, and a live vaccine containing a live heterologous avian infectious bronchitis virus. Use of inactivated avian infectious bronchitis virus strain I-400, and/or an inactivated virus strain which cross-reacts significantly with said strain to prepare a vaccine for use in vaccinating birds against avian infectious bronchitis in combination with an initial vaccination with a live vaccine containing a live heterologous avian infectious bronchitis virus. Claims for the following Contracting State: AT A process for the preparation of a vaccine containing inactivated avian infectious bronchitis virus strain deposited with the Institut Pasteur under the accession number I-400 and/or an inactivated virus strain which cross-reacts significantly with said Strain the immune response to which in birds is enhanced by priming with a live heterologous strain of avian infectious bronchitis virus, which process comprises incorporating said inactivated virus into an adjuvant or carrier. A process as claimed in claim 1 comprising growing avian infectious bronchitis virus strain I-400 and/or an inactivated virus strain which cross-reacts significantly with said Strain the immune response to which in birds is enhanced by priming with a live heterologous strain of avian infectious bronchitis virus, reacting said virus with an inactivating agent and incorporating the inactivated virus into an adjuvant or carrier. A process as claimed in claim 1 or claim 2 wherein the inactivated avian infectious bronchitis virus is I-400. A process as claimed in any one of claims 1 to 3 wherein the inactivated antigen in an aqueous medium is mixed with aluminium hydroxide or an oil emulsion comprising an oil, an oil-soluble surfactant and a water-soluble surfactant. A process as claimed in claim 4 wherein the adjuvant is an oil emulsion in which the oil is a paraffin oil or squalane. A process as claimed in claim 4 or claim 5 wherein the adjuvant is an oil emulsion in which the ratio of oil to aqueous phase is about 4:1. A process as claimed in any one of claims 1 to 6 comprising incorporating into said adjuvant or carrier inactivated virus obtained from 6 to 8 log₁₀ CD₅₀ of the variant strain I-400 and/or said cross-reacting strain per dose of vaccine. A process as claimed in any one of claims 1 to 7 in which, in addition to inactivated avian infectious bronchitis virus strain I-400 and/or an inactivated virus strain which cross-reacts significantly with said Strain, one or more additional inactivated virus strains is incorporated into said adjuvant or carrier. A process as claimed in claim 8 in which the additional inactivated virus strain is inactivated avian infectious bronchitis virus M41. A process as claimed in claim 8 in which the additional inactivated virus strains are inactivated avian infectious bronchitis virus M41 and inactivated Newcastle disease virus. A process as claimed in claim 8 in which the additional inactivated virus strains are inactivated avian infectious bronchitis virus M41, inactivated Newcastle disease virus and inactivated infectious bursal disease virus. Use of inactivated avian infectious bronchitis virus strain I-400, and/or an inactivated virus strain which cross-reacts significantly with said Strain to prepare a vaccine for use in vaccinating birds against avian infectious bronchitis in combination with an initial vaccination with a live vaccine containing a live heterologous avian infectious bronchitis virus.

Inventors: BOX, PHILLIP GEORGE MOUNT VIEW PYRTON, HOLMES, HARVEY CHARLES
Applicants: PITMAN-MOORE, INC.
Application year: 1985
Main classification: A61K39
IPC codes: A61K39