Technical note: recombinant LHRH fusion protein suppresses estrus in heifers.

Abstract

A recombinant luteinizing hormone-releasing hormone (LHRH) fusion protein was evaluated for its effectiveness in suppression of estrus in heifers. Eight heifers were randomly assigned to two equal treatment groups. Treatments consisted of recombinant ovalbumin-LHRH-7 or recombinant ovalbumin (control). This recombinant chimeric fusion protein consisted of ovalbumin with seven LHRH peptides (ovalbumin-LHRH-7). The plasmid for this protein was expressed in E. coli and was collected and purified as an insoluble protein. One milligram of the respective proteins was suspended in 2 mL of Z-Max adjuvant and administered by intramammary injection three times at 7-wk intervals. Luteinizing hormone-releasing hormone antibody binding was elevated in heifers treated with ovalbumin-LHRH-7 compared to ovalbumin-treated heifers (P < .05). Serum progesterone concentrations (< 1 ng/mL) indicate that the estrous cycle of the four heifers treated with ovalbumin-LHRH-7 was suppressed for a time period ranging from 60 to 238 d, which was different from control heifers (P < .01). Serum progesterone for the control heifers continued to exhibit cyclic profiles over the experimental period. This preliminary study in heifers demonstrated that a chimeric LHRH fusion protein induced elevated concentrations of circulating LHRH antibodies that suppressed estrus for an average of 122 +/- 41 d.

LHRH Fusion Protein Immunization Alters Testicular Development, Ultrasonographic and Histological Appearance of Ram Testis

“…1999). Also, OL protein was evaluated for its effectiveness in suppression of oestrus in heifers (Sosa et al. 2000; Stevens et al.…”

Histological Investigation of Testicular and Accessory Sex Glands in Ram Lambs Immunized Against Recombinant GNRH Fusion Proteins

“…Active immunization against GnRH and its analogues has a significant effect on fertility in males and females of different species (7)(8)(9)(10). Immune neutralization of GnRH decreased gonadotroph hormones and sex steroids, with eventual gonadal atrophy.…”

Immunization of beef heifers against gonadotropin-releasing hormone prevents luteal activity and pregnancy: Effect of conjugation to different proteins and effectiveness of adjuvants1

“…Proteins that have been eonjugated to GnRH for immunization are thyroglobulin (Bereu et al, 1977), KL (Adams and Adams, 1986), OA (Johnson et al, 1988), equine serum albumin (Goubau et al, 1989b), HSA (Schanbacher, 1982), and BSA (Fraser et al, 1974;Hauger et al, 1977;Traywick and Esbenshade, 1988). In an attempt to reduce the variability in titers in heifers immunized against GnRH, a recombinant DNA technique has been developed to fuse GnRH to the carrier protein (van der Zee et al, 1995;Sosa et al, 2000;Stevens et al, 2005).…”

“…Conjugation of GnRH to a carrier protein and emulsion with an adjuvant is neeessary to produce antibodies. Immunization of cattle against GnRH has been accomplished by conjugation of GnRH to a carrier protein (Johnson et al, 1988;Wettemann and Castrée, 1994;Prendiville et al, 1995) or by recombinant DNA techniques (van der Zee et al, 1995;Sosa et al, 2000;Hemandez et al, 2005). Booster immunizations increase antibody titers, and the number of boosters necessary to achieve adequate antibody titers may vary among individuals and species.…”