Reproduction Abstracts

Domestic dogs and cats, whether feral or owned, cause the death of millions of wildlife animals every year either by hunting and killing or through disease transmission. The reproductive rates of both species are very high and the current approach of surgical sterilization is too slow and ineffective to have a significant impact on feral cat and dog numbers. The ideal product would be a single dose injectable that causes permanent sterility for cats and dogs of both sexes and that could be administered to large numbers of animals in a short time.

Immunocontraception GnRh is a key instigator of both male and female reproduction. The development of delivery systems for continued life long stimulation of antibodies through injectable virus particles is being developed. The virus imbeds itself in muscle cells and produces lifetime antigens. Further reproductive hormones such as Kisspektin (2), FSH, LH or AMH may also be targeted.

High dose/long-term GNRH agonist Constant supply of GnRH leads to downregulation of the receptors and a complete cessation of the reproductive system in both the male and female. The already licenced drug Deslorelin works on this principle for 6–12 months. Attempts are being made to develop new devices to hold and release medication over much longer periods of time.

Cytotoxins delivered to specific sites killing cells that are essential for reproduction could be used. The toxin is conjugated to a specific antibody that binds to the target cells. The problem in reproduction is that the target cells are either in the hypothalamus or the pituitary gland and have to cross the blood-brain barrier.

Gene silencing/gene therapy A specific protein that suppresses reproduction has to be identified. Delivery of the gene via a virus into the cell for the production of the protein must then be achieved. Gene silencing works with small RNA fragments that are inco-operated into the cell’s DNA to turn off certain genes (3). This has not yet been attempted with reproductive genes, but in other human diseases.