Computational and biological approach for studying structure-function of inhibin chimeric peptide antibodies in Clarias batrachus

Inhibins are heterodimeric glycoproteins that belong to transforming growth factor-β superfamily. The present study was aimed at structural elucidation of immunogenic inhibin chimeric peptide (ICP) using immunoinformatics tools, to develop anti-ICP antibodies and to understand the mechanism of interaction between HPG-axis and anti-ICP antibodies in adult female Clarias batrachus. Homology modelling predicted that the ICP adopts a turn and random coil, which was further confirmed by circular dichroism (CD). Competitive binding ELISA with ICP and different unrelated peptides confirmed that the developed anti-ICP antiserum is highly specific and critical for the direct interaction to the inhibin-α subunit. The anti-ICP antibodies increased the mRNA transcript levels of follicle stimulating hormone receptor (FSHr), luteinizing hormone receptor (LHr), activin receptor type I (Act RI) and activin receptor type II (Act RII). Further, the serum concentrations of follicle stimulating hormone (FSH), 17β-estradiol (E2) and progesterone increased significantly in anti-ICP antisera treated groups compared to control. Modelled inhibin-α and ICP exhibits better interaction with each other through two salt bridge formations. Also, ICP showed better interaction with betaglycan through positive and polar-based interactions. The results of the present study suggest that immunoneutralization of inhibin bioactivity, confirms the physiological role of inhibin as a component of ovarian feedback mechanism regulating FSH secretion through augmentation of gonadotropin and activin receptor signalling pathways that could affect the reproductive success in fishes.