Biological activities of recombinant equine luteinizing hormone/chorionic gonadotropin (eLH/CG) expressed in Sf9 and Mimic insect cell lines.

This study compares the properties of equine luteinizing hormone (eLH) and chorionic gonadotropin (eCG) produced in different insect cells to those of naturally occurring versions of these hormones. The differences between natural and recombinant versions are noted, along with observations on any resulting biological activity.

Background and Methods

• The study focuses on equine luteinizing hormone (eLH) and chorionic gonadotropin (eCG), two hormones that play crucial roles in the reproductive systems of animals. The molecular structures of these hormones are very similar, but eCG contains more glycosylated and sialylated subunits which give it a longer half-life in blood.
• Recombinant versions of the eLH/CG hormones were produced in two types of insect cells – Sf9 and Mimic. The Mimic cells are modified versions of the Sf9 cells and contain genes that allow them to synthesise complex carbohydrates, giving the hormones they produce a different structure and properties.

Results and Conclusion

• The eLH/CG expressed in Mimic cells had a higher molecular weight, which was expected due to their ability to produce more complex carbohydrates. However, their molecular weight was still lower than the naturally occurring eCG derived from pregnant mare plasma.
• The recombinant eLH/CG hormones were found to be active in in vitro (lab-based) luteinizing hormone and follicle-stimulating hormone (FSH) bioassays. This suggests that despite their structural differences, the recombinant hormones had similar activity levels to natural eCG.
• The recombinant hormones did not show significant in vivo (in the body) bioactivity, regardless of the method of production. This was seen in both the specific FSH assay and the specific eCG assay.
• The study authors suggested that this lack of in vivo bioactivity might be due to insufficient terminal sialylation of the carbohydrate chains in the recombinant hormones. Without proper sialylation, these hormones might be rapidly removed from the blood, preventing them from carrying out their biological functions.