Immunization of male mice with luteinizing hormone-releasing hormone fusion proteins reduces testicular and accessory sex gland function

Genes for ovalbumin-luteinizing hormone-releasing hormone 7 (LHRH-7) and th ioredoxin-LHRH-7 fusion proteins (containing seven LHRH inserts) were const ructed by cassette and mismatch mutagenesis and expressed in Escherichia co li. In experiment 1, 10 mu g of either ovalbumin-LHRH-7 or thioredoxin-LHRH -7 were suspended in Z-max adjuvant and injected three times at 4-wk interv als into postpubertal male BALB/c mice. In experiment 2, the fusion protein s were suspended in Immumax adjuvant and administered in equimolar quantiti es (0.4 nmol per injection) to postpubertal male BALB/c mice. In addition t o injection of these two proteins alone, the proteins were also administere d in different sequences or together in a mixture. Both LHRH fusion protein s induced significant antibody titers, which resulted in a significant decr ease in vesicular gland and anterior prostate weight (measure of biological response) in both experiments. Vesicular gland and anterior prostate weigh t and LHRH antibody titers were significantly correlated in experiments 1 ( r = -0.64) and 2 (r = -0.53). Percentage of animals responding to treatment varied from 40-60% in experiment 1 and from 11-89% in experiment 2, with t he highest responses in treatments that used a combination of both fusion p roteins. The variation in responders and nonresponders was evaluated by est imating antibody K-D from displacement curves. Part, but not all, of the hi gh antibody nonresponders can be explained by antibody affinity.