Elsevier

Vaccine

Volume 18, Issues 5–6, 14 October 1999, Pages 416-425
Vaccine

The antigenic and immunogenic properties of synthetic peptide immunocontraceptive vaccine candidates based on gamete antigens

https://doi.org/10.1016/S0264-410X(99)00255-8Get rights and content

Abstract

In this study we have investigated the immunogenicity and antigenicity of synthetic immunocontraceptive vaccine candidates containing T- and B-cell epitopes arranged in different geometries. Two epitopes were selected, a B-cell epitope from fox sperm lactate dehydrogenase C4 and a B-cell epitope from murine zona pellucida protein 3. Both were immunogenic in BALB/c mice when coupled to defined T helper cell determinants, eliciting antibodies which bound to the corresponding B-cell epitope and also to the recombinant protein. Because each of these proteins represent important components in the fertilisation process the results encourage further investigation of synthetic immunocontraceptive vaccines.

Introduction

Anti-fertility vaccines are the subject of current research and evaluation in domestic and wildlife species throughout the world. While immunocontraception offers an attractive alternative to traditional methods of population control, different species require different strategies for suitable and effective control. For example, reversible fertility may be desirable for companion animals while irreversible infertility is appropriate for wild pest populations.

Immunisation with crude gamete extracts often results in a significant decrease in fertility [1] but this strategy is not appropriate for anti-fertility agents because of the large number of antigens that are common to both germ line and somatic cells. Proteins on the surfaces of sperm and ova unique to the gametes have therefore become popular vaccine candidates with several potential antigens identified and characterised [2], [3]. Lactate dehydrogenase C4 isoenzyme (LDH-C4) and zona pellucida glycoprotein 3 (ZP3) are unique to sperm and ova respectively and the surface locations of these antigens (LDH-C4: [4], [5]; ZP3: [6]) and the role of ZP3 in the process of sperm–egg interaction [7] make them ideal immunocontraceptive vaccine targets. Immunisation with purified LDH-C4 has been shown to elicit a specific antibody response and significantly reduce the fertility of mice, rabbits and baboons [8], [9]. Similarly, antibodies specific for particular epitopes on the surface of ZP3 can block the initial sperm–ovum interaction [10] and immunisation with entire ZP3 has been shown to reduce fertility in female primates [11].

For an antibody-inducing immunocontraceptive vaccine to be suitable for release, species specificity must be optimised and autoimmune tissue damage avoided if the effect is to be reversible. Species specificity can be increased substantially through the use of synthetic peptides representing individual B-cell epitopes which are unique to the target species. The selection of defined B-cell epitopes can also prevent side effects associated with immunisation using entire proteins. For example, changes in hormonal profiles and the induction of ovarian histopathology may occur following immunisation with proteins [12], [13], [14]. Short synthetic peptides representing B-cell epitopes are, however, incapable of inducing B-cells to differentiate and produce antibody unless associated with epitopes that are recognised by helper T-cells. Traditionally, carrier proteins, to which the synthetic epitope is coupled, are used to induce the necessary T-cell help. In the case of gamete-derived epitopes such conjugates reduce fertility rates in primates and mice demonstrating the viability of this approach [14], [15]. Conjugation procedures, however, have disadvantages; antigen specificity, for example, may be altered [16], [17], batch to batch variation in the conjugation reaction makes quality control difficult and multiple injections with the same carrier protein may induce either hypersensitivity or immune suppression [18], [19].

An alternative approach to avoid the problems associated with protein carrier-conjugation is to couple the desired epitopes to defined T helper cell epitopes to yield a totally synthetic immunogen. In the present study we have investigated the immunogenicity of candidate contraceptive vaccines based on the assembly of B-cell epitopes for sperm and ova antigens with defined T-cell epitopes from unrelated proteins.

Section snippets

Reagents

Unless otherwise stated, chemicals were of analytical or best available grade. N,N′-dimethylformamide (DMF), trifluoroacetic acid (TFA), O-benzotriazole-N,N,N′,N′-tetramethyl-uronium-hexafluorophosphate (HBTU), 1-hydroxybenzotriazole (HOBt) and diisopropylethylamine (DIPEA) were obtained from Auspep Pty Ltd (Melbourne, Australia). Phenol and triisopropylsilane (TIPS) were from Aldrich (Milwaukee, USA). Trinitrobenzylsulfonic acid (TNBSA) was from Fluka (Switzerland).

Immunogenicity of linear peptides containing GPSL linker

The sequence ENLIEEDKSQ (B1) is present in fox lactate dehydrogenase C4 (LDH-C4) and corresponds to reportedly antigenic sequences in gamete-specific LDH-C4 of other species. When conjugated to diphtheria toxoid as a carrier protein, O'Hern [15] demonstrated that the corresponding epitope from human LDH-C4 induced antibodies and caused a 75% reduction in the fertility of female baboons. In later experiments [24], a defined T helper cell epitope VDDALINSTKIYSYFPSV from tetanus toxoid was used to

Acknowledgements

This work was supported by Grant 980664 from the National Health and Medical Research Council of Australia and funds from both the Cooperative Research Centre for Vaccine Technology and the Cooperative Research Centre for Vertebrate Biocontrol. We thank Dr Laszlo Otvos for the circular dichroism and infrared spectroscopy.

References (30)

  • A.B. Diekman et al.

    Sperm antigens and their use in the development of an immunocontraceptive

    Am. J. Reprod. Immunol. Microbiol.

    (1997)
  • S.A. Beyler et al.

    Binding of antibodies against antigenic domains of murine lactate dehydrogenase-C4 to human and mouse spermatozoa

    Biol. Reprod.

    (1985)
  • M.P. Bradley et al.

    Cloning, sequencing, and characterization of LDH-C4 from a fox testis cDNA library

    Mol. Reprod. Dev.

    (1996)
  • H. Bagavant et al.

    Immunogenicity and contraceptive potential of a human zona pellucida 3 peptide vaccine

    Biol. Reprod.

    (1997)
  • J.E. Lerum et al.

    Immunological impairment of pregnancy in mice by lactate dehydrogenase-X

    Biol. Reprod.

    (1974)
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