Immunocontraception involves eliciting an immune response against eggs, sperm or hormones
so that successful reproduction is prevented. Work in Australasia is aimed at European rabbits
(Oryctolagus cuniculus), red foxes (Vulpes vulpes), house mice (Mus musculus), common
brushtail possums (Trichosurus vulpecula), koalas (Phascolartcos cinereus) and kangaroos
(Macropus spp.), with the vaccines involved all containing self antigens or their relatives. Two
fundamental problems have been inadequately addressed in this research. The first problem is
that it is difficult to obtain strong immune responses against self antigens and so the vaccines
may be ineffective. Most published data on the effect of immunocontraceptives on reproduction
involve the use of an adjuvant of which there are many kinds. The materials enhance the
immune response greatly. The most frequently used is Freund?s adjuvant which can cause
chronic suffering. Its use on wildlife will lead to very negative public perceptions. There has
been no convincing demonstration that successful immunocontraception is possible with any
method of vaccination likely to be used in the field, if success is defined as contraception of a
proportion of the population high enough for management requirements. If it is assumed that
success can be achieved, the second fundamental problem arises with two potential
consequences. Even with adjuvant, a substantial minority of the vaccinated animals remains
fertile. The first consequence is that since failure to be contracepted is likely to be in part
genetic, there is likely to be rapid selection for these non-responders. The method will become
ineffective in a few generations. The second problem is that the offspring of the animals which
breed will have altered immune responses. Their capacities to respond to their own pathogens or
to harbor pathogens of other species in the same ecosystem are likely to be changed. The
presence of chlamydia in P. cinereus and bovine tuberculosis in New Zealand T. vulpecula
means that responses to these pathogens would have to be studied in offspring of
immunocontracepted parents to ensure that the offspring were not more susceptible to them.
New Zealand intentions to put an immunocontraceptive into a T. vulpecula gut worm must be
viewed with caution by Australia. The eggs of transgenic worms will be easily transplanted
either accidentally or deliberately back into Australia, and so infect T. vulpecula in Australia.
The Thymic Repertoire of Neuroendocrine-Related Self Antigens: Biological Role in T-Cell Selection and Pharmacological Implications