Development of recombinant ovalbumin-luteinizing hormone releasing hormone as a potential sterilization vaccine

The objective was to develop an immunogenic chimeric ovalbumin-LHRH (ova-LHRH) molecule using genetic engineering. Hybrid ova-LHRH genes with either four or seven LHRH inserts were constructed by cassette mutagenesis and oligonucleotide mismatch mutagenesis. Recombinant ova-LHRH proteins were over-expressed in E, coli strain BL21 (DE3) using a pET expression system, which expresses a target protein with a C-terminal His-Tag, The C-terminal His-Tag allows purification by metal chelation chromatography. The antigenicity and biological effects of these recombinant proteins were tested in mice. In experiment 1, 17 female 7 wk old BALB/c mice were randomly divided into three groups. Six mice were injected with 50 mu g of the recombinant ovalbumin (ova) protein. Five mice were injected with 50 mu g of the recombinant protein with four LHRH inserts (ova-LHRH-7). Six mice were injected with 50 mu g of the recombinant protein with seven LHRH inserts (ova-LHRH-7). One primary immunization using Freund's complete adjuvant was followed by one booster using incomplete adjuvant. Mice were killed 2 wk after the booster, blood collected, and the reproductive tract removed and weighed. Only ova-LHRH-7 decreased (P < 0.01) uterine-ovarian weight (89 +/- 11 mg) vs control (138 +/- 6 mg) and ova-LHRH-4 (126 +/- 16 mg). The genetically engineered molecule with seven LHRH inserts induced LHRH antibody titers which were significantly correlated (r = - 0.79) with biological response. In experiment 2, the recombinant ova-LHRH-7 was evaluated at two doses with the adjuvants Zmax and Immumax. Seventy female 6-8 wk old BALB/c mice were randomly divided into seven groups of 10 mice each. Anti-LHRH titers were detected in all of the ova-LHRH-7 immunized mice. Significant decreases were shown in uterine-ovarian weight of the mice by the immunization with 30 mu g of ova-LHRH-7 and Zmax (P < 0.005) or 10 mu g of ova-LHRH-7 with Immumax (P < 0.025). These data show that the recombinant ova-LHRH-7 protein could have potential as an effective sterilization vaccine. (C) 1999 Elsevier Science Ltd. All rights reserved.