Contraceptive responses of mice immunized with purified recombinant mouse zona pellucida subunit 3 (mZP3) proteins

Abstract

Mouse zona pellucida subunit 3 (mZP3) was tested for efficacy as an immunocontraceptive antigen by comparing the fertility of mice immunized with recombinant mZP3 proteins. Recombinant protein was expressed using either the vaccinia virus T7 mammalian (vmZP3 protein) or baculovirus insect cell (bmZP3 protein)-expression systems. Female BALB/c or wild mice were immunized by i.p. injection using Freund's complete adjuvant and boosted three times with affinity purified recombinant proteins in Freund's incomplete adjuvant. Most mice developed antibodies that crossreacted to the respective mZP3 antigens by ELISA or western blot. In BALB/c mice immunized with vmZP3, fertility and mean litter size were reduced transiently to 25% and 10%, respectively, of those of control mice. However, immunization with bmZP3 did not affect either the fertility or mean litter sizes in BALB/c or wild mice immunized with bmZP3. The results demonstrate that reduction in fertility can be achieved in female BALB/c mice immunized using Freund's adjuvants and recombinant mZP3 protein produced in a mammalian, but not an insect, cell-expression system. Arguments are presented for the likely role of glycosylation of the mZP3 antigen in inducing contraceptive immune responses.

Enhanced contraceptive response by co‐immunization of DNA and protein vaccines encoding the mouse zona pellucida 3 with minimal oophoritis in mouse ovary

“…It appears that there is no correlation between the levels of total IgG antibody and infertility in mice immunized with different regimens except the co‐immunized group. This is similar to reports that not only does the level of IgG antibodies not appear to be associated with infertility, but also there is no correlation between IgG1 or IgG2a antibodies and infertility in mice immunized with recombinant ZP3 proteins or inoculated with murine cytomegalovirus expressing the mZP3 gene 11, 12, 14. However, antibodies against ZP3 are important for infertility as demonstrated in several other studies that high titers of total IgG are associated with infertility in mice immunized with ZP3 peptides or with a recombinant ectromelia virus expressing the mZP3 gene 13, 24, 25.…”

“…Sperm‐egg binding can be blocked by importing another ligand for receptor sites such as antibodies of ZP3 and prevent fertilization. Several studies have demonstrated that vaccines formulated with either native or recombinant ZP antigens can suppress fertility effectively following an active immunization 8–12. However, there is much accumulating evidence to suggest that this approach is associated with adverse autoimmune reactions in the ovaries leading to a deleterious effect on ovarian function 8, 9, 12–14.…”

Development of a contraceptive vaccine for the marsupial brushtail possum (Trichosurus vulpecula): lack of effects in mice and chickens immunised with recombinant possum ZP3 protein and a possum ZP3 antifertility epitope

“…Another issue is how fertility responses in trials such as these may differ from those of the final bait-delivered product as a result of differences in route of immunisation, dose, and antigen presentation. For example, the effects on fertility in mice differ significantly between intramuscular immunisation with recombinant mouse ZP3 and infection with mouse cytomegalovirus expressing mouse ZP3 (Hardy et al 2003;Lloyd et al 2003). Ultimately, a wider range of non-target species will have to be tested to satisfy regulatory requirements before a bait-delivered fertility vaccine could be deployed.…”

“…Mice immunised with recombinant mouse ZP3 expressed from a mammalian cell-expression system show reduced fertility (Hardy et al 2003), and this effect has been traced, at least in part, to a specific 15-21-amino-acid epitope of the protein (Millar et al 1989;Lou et al 1995;Hardy et al 2002Hardy et al , 2003. The initial hypothesis was that this epitope was a sperm-binding 'receptor'.…”

Controlling Animal Populations Using Anti‐Fertility Vaccines

“…2003), Chinese hamster ovary (CHO) systems (Zhao et al. 2004), plant systems (Tacket 2005), viral systems (Hardy et al. 2003), insect systems (Hardy et al.…”