Prostatic hypoplasia in bonnet monkeys following active immunization with semisynthetic anti-LHRH vaccine

An active immunization study using semisynthetic anti-luteinizing hormone releasing hormone (LHRH) vaccine was undertaken in adult male bonnet monkeys (Macaca radiata). Four male bonnet monkeys were immunized with LHRH-DT vaccine (100 micrograms/monkey). When the elevation of serum anti-LHRH titers reached an effective concentration, a remarkable decrease in serum testosterone level was observed. The sperm counts at 12 and 20 weeks following immunization in all immunized monkeys were reduced markedly. One representative animal with high antibody titer along with an age-matched control animal was sacrificed 20 weeks following primary immunization. The prostate weight of the immunized monkey was reduced to one-third (0.027) of the control (0.085). A reduction was also observed in other reproductive organs. Remaining animals are being studied for a reversible effect of immunization. Thus the study demonstrates that the size of the prostate can be reduced significantly by inhibition of hypothalamic-pituitary-testicular axis using this anti-LHRH vaccine.