Title:  Method to prevent fertilization in mammals by administering a single dose of zona pellucida derived antigens, liposome and adjuvant

United States Patent:  RE37,224

Assignee:  Dalhousie University (CA)

Filed:  July 23, 1998

A vaccine for the immunocontraception of mammals is described. The vaccine consists of zona pellucida antigens and an adjuvant encapsulated in a liposome delivery system. The liposome delivery system allows for the slow release of antigen resulting in a prolonged immune response. In particular, after a single injection of the vaccine, levels of anti-zona pellucida antibodies were detected for up to 22 months in seals. Thus, the vaccine according to the present invention is effective after a single dose and is therefore very useful in immunocontraceptive protocols.

SUMMARY OF THE INVENTION

The present invention relates to an immunocontraceptive vaccine preparation which comprises zona pellucida antigens incorporated into a liposome delivery system. The liposome system effects the slow release of antigen resulting in an extended period of antibody production and thereby an extended period of contraception. Therefore, the present invention provides a method to achieve immunocontraception of mammals using a single injection of zona pellucida glycoproteins.

Accordingly, the invention provides a vaccine composition for the immunocontraception of a mammal which comprises a zona pellucida derived antigen incorporated into a liposome system.

The invention further provides a vaccine composition capable of inducing the production of antibodies to a zona pellucida antigen, said composition comprising a zona pellucida derived antigen incorporated into a liposome system.

In one embodiment of the present invention, the liposome vaccine composition is freeze-dried and incorporated into a BALLISTIVET biobullet. Such an embodiment makes the vaccine easier to deliver to the animal.

In another aspect, the invention provides a method of preventing fertilization in a mammal which comprises .Iadd.parenterally .Iaddend.administering an effective amount of the above-described vaccine.

DETAILED DESCRIPTION OF THE INVENTION

Isolation and purification of zona pellucide glycoproteins

Zona pellucidaglycoproteins were isolated and purified as described by Yurewicz (in Yurewicz, E. C., A. G. Sacco, and M. G. Subramanian, Structural Characterization of the Mr=55,000 Antigen (ZP3) of Porcine Oocyte Zona Pellucida, The Journal of Biological Chemistry 262: 564-571 (1987). Porcine ovaries were homogenized and the oocytes recovered from the homogenate by sieving through nylon screens of decreasing pore size (500, 350, 200, 175, 100 and 40 .mu.m). The oocytes were homogenized with a glass-teflon apparatus and the homogenate was passed through a 40 um screen to collect the fractured zonae. The fractured zonae were washed with buffer and recollected on the 40 um screen. Zona pellucida glycoproteins were solubilized by incubating the zonae in a water bath (73^oC. for 20 minutes). The fraction obtained (solubilized intact zona pellucida glycoproteins, SIZP) was shown to be at least 95% pure by comparison to a reference standard of ZP using an ELISA assay.

ZP3 was purified from SIZP as described by Yurewicz et al (1987). ZP3 is one of three glycoproteins that make up the mealis zona pellucida. ZP3 is the major macromolecular component of the oocyte zona pellucida and has been shown to be the receptor for sperm.

Porcine ZP has been used to effect immunocontraception in a variety of mammals. Porcine ZP pellucida was used in the present studies for several reasons. Firstly, a comparison of the reactivity of ZP from five mammalian species to rabbit antiserum against porcine ZP indicated that pig ZP was recognized best followed by dog ZP while rat and cat ZP reacted poorly (Maresh, G. A. and B. S. Dunbar. 1987. Antigenic comparison of five species of mammalian zonae pellucida. J. Experimental Zoology 244: 299-307). Since seal and dog are closely related, (Berta, A., C. E. Rae, A. R. Wyss, 1989, "Skeleton of the oldest known pinniped Enaliarctos mealsi", Science 244: 60-62), anti-porcine ZP antibodies will bind to seal zonae. Secondly porcine ZP can also be easily obtained from slaughterhouse pigs. Thirdly, pigs ovulate multiple oocytes and thus provide a rich source of zona pellucida.

Claim 1 of 26 Claims

We claim: .[.

1. A method of preventing fertilization in a mammal for at least twelve months which method consists of a single parenteral administration of an effective amount of a vaccine composition comprising a zona pellucida derived antigen and a Freund's adjuvant in a liposome formulation..]..[.

____________________________________________
If you want to learn more about this patent, please go directly to the U.S. Patent and Trademark Office Web site to access the full patent.