As is well-known in the field of immunology, "adjuvants" are agents which act in a nonspecific manner to increase an immune response to a particular antigen, thus reducing the quantity of antigen necessary in any given vaccine, as well as the frequency of injection. See, e.g., A. C. Allison, J. Reticuloendothel. Soc. 26:619-630 (1979). A number of aliphatic nitrogenous bases have been proposed for use as immunologic adjuvants, including amines, quaternary ammonium compounds, guanidines, benzamidines and thiouroniums (D. Gall, Immunology 11:369-386 (1966)). Specific such compounds include dimethyldioctadecylammonium bromide (DDA) (available from Kodak) and N,N-dioctadecyl-N,N-bis(2-hydroxyethyl)propanediamine ("avridine"). The use of DDA as an immunologic adjuvant has in fact been widely publicized; see, e.g., the Kodak Laboratory Chemicals Bulletin 56(1):1-5 (1986); Adv. Drug Deliv. Rev. 5(3):163-187 (1990); J. Controlled Release 7:123-132 (1988); Clin. Exp. Immunol. 78(2):256-262 (1989); J. Immunol. Methods 97(2):159-164 (1987); Immunology 58(2):245-250 (1986); and Int. Arch. Allergy Appl. Immunol. 68(3):201-208 (1982). Avridine, also, is well-known as an adjuvant. See, e.g., U.S. Pat. No. 4,310,550 to Wolff, III et al., which describes the use of N,N-higher alkyl-N',N'-bis(2-hydroxyethyl)propane diamines in general, and avridine in particular, as vaccine adjuvants. U.S. Pat. No. 5,151,267 to Babiuk and Babiuk et al., Virology 159:57-66 (1986), also relate to the use of avridine as a vaccine adjuvant. The foregoing references, as well as all other patents, patent applications, and publications cited herein, are hereby incorporated by reference in their entirety.
The present invention is directed to a technique whereby the immunogenic activity of compounds such as those identified above is enhanced. The technique involves admixture of an aliphatic nitrogenous compound such as DDA or avridine with a mineral oil, a vegetable oil, an animal oil, or a mixture thereof. Like the aforementioned nitrogenous compounds, certain oils have also been recognized to have adjuvant activity (see, e.g., U.S. Pat. Nos. 4,310,550, 4,395,394, 4,806,352, 4,867,899, 4,876,094 and 5,102,660). However, the inventors herein have found, surprisingly, that combining the selected nitrogenous compound with one or more such oils provides for superior adjuvant activity, far beyond the simple additive effect which would be expected upon combining the two types of adjuvants. Accordingly, then, the invention is primarily directed to methods and compositions which involve the combination of an aliphatic nitrogenous compound such as DDA or avridine with a selected oil as will be described in further detail below.
It has also been found, surprisingly, that the aforementioned compositions, containing an aliphatic nitrogenous compound and an oil component, have nonspecific immunostimulatory activity. Thus, the invention is also directed to a method for inducing an immune response in an individual by administering the composition of the invention without co-administration of an antigen, i.e., as a nonspecific immunostimulatory composition.