Screening and Preliminary Identification of Inhibin α Subunit-Specific Nanobodies Through High-Throughput Sequencing Combined with Mass Spectrometry.

Inhibin, a water-soluble protein emitted by the gonads, plays a pivotal role in regulating the release of follicle-stimulating hormone (FSH) from the pituitary gland, which, in turn, influences follicular growth, gamete production, and the secretion of associated hormones. We performed high-throughput sequencing of the nanobody gene in the lymphocytes of Bactrian camels before and after inhibin α protein immunization followed by mass spectrometry analysis of specific antibodies to this protein in the serum following immunization to screen for inhibin α subunit-specific nanobodies. Seven inhibin α-specific nanobodies, namely Nb-1712, Nb-1971, Nb-2000, Nb-799, Nb-2004, Nb-1737, and Nb-338, were identified through high-throughput sequencing and mass spectrometry. Following the construction and expression of a prokaryotic expression vector, five of these nanobody proteins were successfully produced. These proteins demonstrated high affinity for inhibin α in the indirect enzyme-linked immunosorbent assay. Notably, nanobodies Nb-1737, Nb-1971, and Nb-2004 significantly downregulated Inha and upregulated Fshb gene expression, enhancing follicle-stimulating hormone secretion. In female mice, these three nanobodies promoted follicular development and led to a numerical increase in litter size (average ~10%, with Nb-2004 showing a 14.93% increase), although the differences were not statistically significant. These findings demonstrate their potential to regulate reproductive function. We identified 7 inhibin α subunit-specific nanobody genes from a Xinjiang Bactrian camel's lymphocyte genome through high-throughput sequencing and mass spectrometry. We also compared their relative binding affinities and characterized their biological functions, thereby providing key theoretical guidance and technical support for increasing FSH levels.