Mechanisms of virally vectored immunocontraception

This thesis describes the production and characterisation of a recombinant immunocontraceptive vaccine that has been developed to control rapidly increasing mouse populations as a supplement to current mouse control strategies. It was hypothesised that a live virus engineered to express a fertility antigen could be used to induce an immunocontraceptive response and would be naturally transmitted through the free-living population. The recombinant vaccine was generated by the insertion of a gene expressing the murine ovarian glycoprotein, zona pellucida 3 (ZP3), into the K181 strain of a mouse-specific betaherpesvirus, murine cytomegalovirus. The resultant recombinant virus, designated rK181-mZP3, displayed normal growth kinetics in vitro but demonstrated significantly impaired replication in vivo. Despite this, a single inoculation of 2x104 plaque forming units of rK181-mZP3 induced long-lasting infertility (>250 days) in BALB/c mice. The efficacy of immunocontraception was dependent on the viral dose and the route of inoculation utilised. Infected mice produced ZP3-specific antibodies that were detected bound to the follicular zona pellucida. Ovarian-bound antibody was detected from 14 days post inoculation, and this timing correlated with the initiation of the immunocontraceptive effect in inoculated mice. Immunocontraception was complete in BALB/c mice by 21 days post inoculation. Follicular damage was apparent from 7 days post inoculation and a significant reduction in mature follicles was detected by 21 days post inoculation. By 100 days post inoculation the damage culminated in an overall reduction in follicles of all stages and an altered ovarian architecture. Alternatively, when rK181-mZP3 was inoculated in C57BL/6 or CBA inbred mouse strains, a 10-fold higher dose of virus was required to elicit significant infertility.