WATER-IN-OIL EMULSION FOR USE IN THE POTENTATION OF THE IMMUNE SYSTEM OF ANIMALS

Abstract: Intraperitoneal injection of animals with antigen-free water-in-oil emulsions comprising an aqueous phase dis­ persed in a mineral oil by means of an emulsifier was found to induce an immunological response improving the mucos­ al immunity of the animals. The invention relates to these water-in-oil emulsions for use in the immunization of animals by intraperitoneal injection, as well as to antigen-­ free injectable pharmaceutical water-in-mineral oil emul­ sions in which the emulsifier is a mixture of at least one sorbitan fatty acid ester, preferably sorbitan trioleate, and at least one polyoxyethylene sorbitan fatty acid ester, prefer­ ably polyoxyethylene-20-sorbitan trioleate.

Description: Water-in-oil emulsion for use in the immunization of animals. Water-in-oil emulsions have been known as adjuvants for antigens. A well-known water-in-oil adjuvant is Freund's incomplete adjuvant which consists of an emulsion of physiological saline in a light aD mineral oil using Arlacel A (impure form of the ester of mannitol and oleic acid) as the emulsifier. Freund's complete adjuvant contains killed mycobacteria in the aqueous phase. Freund's complete and incomplete adjuvants are used as vehicles for antigens and provoke a substantial increase of the immune response in comparison with the effect of the antigen when administered in physiological saline. Complete Freund's adjuvant induces a general improvement of the immunity, among others by stimulating antibody production. Water-in-oil adjuvants such as Freund's incomplete adjuvant, have been used exclusively as vehicles for antigens, and have been administered by intradermal or intramuscular injection mostly. It was found that antigen-free water-in-oil emulsions comprising an aqueous phase dispersed in a mineral oil by means of an emulsifier can be used successfully for the immunization of animals if these emulsions are administered by intraperitoneal injection. Consequently, the invention relates to a water-in-oil emulsion for use in the immunization of animals by intraperitoneal injection, said emulsion being substantially free of antigen and comprising an aqueous phase dispersed in a mineral oil by means of an emulsifier. Surprisingly, intraperitoneal injection of the present antigenfree water-in-oil emulsions very rapidly induces an immunological response improving the mucosal immunity of the host animal. In the water-in-oil emulsions according to the invention the aqueous phase may be simply water, or physiological saline. If desired, preserving agents suitable for parenteral administration, such as formalin, may be added. A preferred water phase is, for example, an aqueous solution containing 0.85 % by weight of sodium chloride and 0.2 % by volume of formalin. Further, it was found that novel water-in-oil emulsions containing as an emulsifier a mixture of at least one sorbitan fatty acid ester and at least one polyoxyethylene sorbitan fatty acid ester are particularly effective for immunization of animals by intraperitoneal injection. Therefore, the invention relates to a novel injectable pharmaceutical composition comprising a water-in-oil emulsion of an aqueous phase dispersed in a mineral oil by means of an emulsifier consisting of a mixture of at least one sorbitan fatty acid ester and at least one polyoxyethylene sorbitan fatty acid ester, said composition being substantially free of antigen. Preferably, the emulsifier which, according to the invention, is a mixture of at least one sorbitan fatty acid ester and at least one polyoxyethylene sorbitan fatty acid ester, has an HLB-value (hydrophile-lipophile balance) of 5.5-6.3. Excellent results have been obtained with emulsifiers whose fatty acid radicals are derived from oleic acid, especially with mixtures of sorbitan trioleate and polyoxyethylene-20-sorbitan trioleate. In the latter mixtures the volume ratio of sorbitan trioleate to polyoxyethylene-20-sorbitantrioleate is preferably 1:1 to 1.3:1 in view of the stability of the emulsion. The emulsifier may consist of other combinations of sorbitan fatty acid esters and polyoxyethylene sorbitan fatty acid esters as well. In that case the volume ratios are preferably chosen in such a way that the emulsifier has an HLB-value of 5.5-6.3. Preferably, the volume ratio of emulsifier to mineral oil to aqueous phase is about 100:900:700-1000. Such emulsions show excellent stability and injectibility. Their viscosity is about 0.07-0.09 Pa.s (70-90 cP). The mineral oil may be any mineral oil suitable for parenteral purposes. Good results have been obtained with Marcol 52 (Esso), a mixture of paraffins and cycloparaffins in the ratio of 63:37 having a chainpength between 13 and 22 carbon atoms. Preferred emulsifiers are well defined products having the best possible purity. In practice, good results have been obtained with a mixture of Span 85 (ICI, United States of America) and Tween 85 aD (ICI, United States of America). The aqueous phase may be merely water, but preferably a salt such as sodium chloride is added in order to bring the osmotic pressure in agreement with that of the blood. Thus, the aqueous phase may be, for example, a physiological salt solution. Further, preserving agents suitable for parenteral administration may be added, such as formalin etc. A preferred water phase is, for example, a solution of 0.85 % by weight of sodium chloride and 0.2 % by volume of formalin in destilled water. The emulsions according to the present invention may be prepared in a way usual for water-in-oil emulsions. Generally, the mineral oil is first mixed with the emulsifier and then the aqueous phase is added. The emulsion is then prepared by vigorous mixing of the phases by means of a suitable agitating device, such as a colloid mill. The invention is of great importance for the production of mammals, such as pigs, on an industrial scale. The present emulsions have a high stability and are non-pyrogenic. Although the immunizing activity of the antigen-free emulsions according to the invention is not fully understood it is believed that the present emulsions induce immunity against pathogenic organisms present in the host or infecting the host shortly after the administration of the emulsion. The following examples illustrate the invention They are to be construed only as illustration and are not intended as limitations of the invention. Example I Preparation of the emulsion. In a glass vessel 9 parts by volume of mineral oil (Marcol 52) were thoroughly mixed with 1 part by volume of a mixture of sorbitan trioleate (Span 85) and polyoxyethylene-20-sorbitan trioleate (Tween 85) in a volume ratio of 54:46. Then the generator (No. T30G) of an Ultraturrax T45 (Janke & Kunkel) was placed under the surface of the mixture and 8 parts by weight of a water phase consisting of a physiological salt solution (0.85 % by weight of NaCl + 0.2 % by volume of formalin) was gradually added to the mixture with continuous stirring at 10.000 rpm. After addition of the total amount of water phase the emulsification was continued for 1 minute. During the emulsification the vessel was cooled externally with tap-water. The temperature at the end of the process was about 0 45 C. Then the emulsion so obtained was poured into a beaker and the emulsion was cooled to room-temperature with stirring. The 0 emulsion was brought into vials and stored at +4 C. Stability tests. - 1. After storage for more than 1 year at 4 C the emulsions did not show any alterations, and the electrical conductivity of the emulsions appeared to show the original value. 2. After storage for more than 3 months at 370C the present emulsions sometimes showed a thin clear fluid layer on top of the emulsion which was always less than 5 % of the total volume. 3. After ten times shifting the temperature of the emulsions from 40C to 370C and back to 40C the same fluid layer as described under 2. was sometimes observed. 4. The conductivity of the emulsions measured at 200C was always smaller than 0.6 xu Siemens. 5. After centrifugation of the emulsions for 1 hour at 15000 g a thin fluid layer as described under 2. was observed. Example II. Treatment of piglets with the emulsion according to example I. a) Every week (on fridays) during a period of 6-11 months an intraperitoneal injection of 1 ml of the emulsion prepared in accordance with example I was given to half of the piglets (of 5 different pig-breeding farms) born in the 4th week preceding the injection week. On wednesdays following the injection these piglets were weaned. The treated piglets were not separated from the untreated ones. In the year preceding the tests the average mortality of the weaned piglets in the same farms was 12%. During the period of treatment this mortality was about 2%. A significant difference in mortality between the untreated and treated animals could not be observed. An explanation of this phenomenon could be that the treatment of half of the animals would lower the "infection pressure" resulting in less infection in the untreated animals. b) The following test was carried out in order to obtain a better insight in the protective activity of the present emulsion. The test was carried out during a period of 21 weeks in a pigbreeding farm having a production of about 100 piglets per week. All piglets to be weaned on wednesdays were treated on the preceding fridays according to the scheme shown in the following table. At the time of treatment the piglets were 4 to 49 weeks old. The emulsion according to example I was administered intraperitoneally in an amount of 1 ml. The physiological saline was also given intraperitoneally in an amount of 1 ml. Also, the table shows the number of piglets weaned in a particular week. From the beginning to the end of the experiment the 2267 piglets did not receive antibiotics. The piglets left the farm after a period of five weeks after weaning. The emulsion treated, physiologsal saline treated and untreated animals were not seperated from eachother, but were added, every wednesday, to the existing population of about 500 weaned piglets. The percentage mortality in each of the groups during the five weeks after weaning was determined. This percentage is also mentioned in the table. The attached drawing shows the mortality in graphical form. The average mortality in the year preceding the test period was 20% (with use of antibiotics). TABLE. week intraperitoneal injection number of mortality in 5 with weaned weeks after piglets weaning (%) 0 emulsion according to example I 117 10 1 emulsion according to example I 83 1 2 0.85 % NaCl 79 11 3 emulsion according to example I 121 1 4 0.85 % NaCl 95 6 5 nothing 98 15 6 nothing 90 29 7 nothing 114 10 TABLE (continued) week intraperitoneal injection number of mortality in 5 with weaned weeks after piglets weaning (%) 8 0.85 % NaCl 90 8 9 0.85 % NaCl 95 18 10 0.85 % NaCl 85 8 11-21 emulsion according to example I 1200 0-1 As shown by the table the mortality decreases strongly after the first injection with the emulsion, in spite of the fact that the animals did not receive antibiotics. After intraperitoneal injection of physiological saline in week 2 the mortality was 11 %, whereas litters which had received the emulsion in week 1 or week 3 respectively showed a mortality of 1%. The percentage mortality of the animals treated in week 4 with physiological saline increased to 6 % and the percentage mortality of the animals treated in weeks 5 to 7 inclusive increased to an average of about 18 %. Injection with physiological saline of the animals weaned in weeks 8 to 10 inclusive resulted in an average mortality of 11 %. None of the 324 piglets injected with the emulsion in weeks 11 to 13 inclusive died. This excellent result was maintained during the rest of the test. Only two piglets from litters injected with the emulsion in weeks 19 and 20 died from post-weaning disease. The average mortality rates in piglets injected with the emulsion, with physiological saline and without treatment were 0.3 %, 9.9 % and 17.9 % respectively. No sEnificant increase of body temperature was observed in any of the piglets after injection with the emulsion according to example I.

Claims: CLAIMS. 1. A water-in-oil emulsion for use in the immunization of animals by intraperitoneal injection, said emulsion being substantially free of antigen and comprising an aqueous phase dispersed in a mineral oil by means of an emulsifier. 2. The emulsion of claim 1, in which the aqueous phase is water. 3. The emulsion of claim 1 in which the aqueous phase is physiological saline. 4. The emulsion of claim 1 in which the aqueous phase is 0.85 % by weight of sodium chloride and 0.2 % by volume of formalin in water. 5. Injectable pharmaceutical composition comprising a water-in-oil emulsion of an aqueous phase dispersed in a mineral oi2 by means of an emulsifier consisting of a mixture of at least one sorbitan fatty acid ester and at least one polyoxyethylene sorbitan fatty acid ester, said composition being substantially free of antigen. 6. The composition of claim 5 in which the emulsifier has an HLB-value of 5.5-6.3. 7. The composition of claim 5 or 6, in which the fatty acid esters of the emulsifier are derived from oleic acid. 8. The composition of any of claims 5 to 7 in which the emulsifier consists of a mixture of sorbitan trioleate and polyoxyethylene20-sorbitan trioleate. 9. The composition of claim 8, in which the volume ratio of sorbitan trioleate to polyoxyethylene-20-sorbitan trioleate is 1:1 to 1.3:1. 10. The composition of any of claims 5 to 9 in which the volume ratio of emulsifier to mineral oil to aqueous phase is about 100:900:700-1000. 11. The composition of any of claims 5-10 in which the aqueous phase is water. 12. The composition of any of claims 5-10 in which the aqueous phase is physiological saline. 13. The composition of any of claims 5 to 10 in which the aqueous phase is 0.85 % by weight of sodium chloride and 0.2 % by volume of formalin in water. 14. The composition of any of claims 5 to 13 for use in the immunization of animals by intraperitoneal injection.

Inventors: BOKHOUT, BERNARD ADRI, NABUURS, MARIUS JOZEF ANTONIUS, VAN DER HEIJDEN, PHILIPPUS JAN
Applicants: CENTRAAL DIERGENEESKUNDIG INSTITUUT
Application year: 1982
Main classification: A61K39
IPC codes: A61K47, A61K39, A61K9