Immunization against recombinant GnRH-I alters testicular structure in an experimental boar model

Abstract

The aim of this study was to evaluate and to compare testicular tissue in immunized and control boars. Eighteen male piglets, aged 12 weeks, were vaccinated twice intramuscularly with a maltose-binding protein-gonadotropin-releasing hormone I hexamer peptide (MBP-GnRH-I6). Blood samples were taken at 12, 18, 21 and 24 weeks of age. Serum concentrations of testosterone and GnRH-I antibodies were determined by radioimmunoassay. The pigs were sacrificed 6 weeks after the second immunization. Testicular weight and size were recorded and tissue samples were collected for histological examination. The results demonstrated that active immunization against MBP-GnRH-I6 increased serum GnRH-I antibody levels (P < 0.05) and reduced serum concentrations of testosterone (P < 0.05) when compared with controls. Histological studies performed on testicular tissue revealed clear signs of atrophy in the MBP-GnRH-I6 immunized pigs, and a significant reduction (P < 0.05) in paired testes weight and size were seen in the treated boars. Microscopically, the mean diameter of the seminiferous tubules was markedly reduced (P < 0.01). Spermatogonia were visible, as well as few spermatocytes, but no spermatozoa were detected in the seminiferous tubules. Ultramicroscopic analysis of testicular tissue revealed an increase in the thickness of the basement membrane and extensive damage in the cell organelles of the treated animals, including small spermatogonial size, decreased number of mitochondria and endoplasmic reticulum in the primary spermatocyte and spermatid, a shallow hollow for nuclear membranes in Sertoli cells and mitochondrial vacuolation in Leydig cells. We conclude that MBP-GnRH-I6 induces severe atrophy in the testes of immunized boars.

Effect of early immunocastration on testicular histology in pigs

“…Interstitial endocrine cells were shrunken and had both a small nucleus and limited cytoplasmic area. Similar results have been reported by other studies (Einarsson et al 2011;Kubale et al 2013;Li et al 2015). These changes in the morphology of interstitial endocrine cells were consistent with a loss of function and the decrease in testosterone and androstenone (Kubale et al 2013).…”

“…According to Original Paper Veterinarni Medicina, 63, 2018 (01): 18-27 doi: 10.17221/121/2017-VETMED the manufacturer's instructions, the vaccine's primary dose can be administered no earlier than at eight weeks. In fact, researchers have used various vaccination schedules, with the primer dose being administered at 11-16 weeks and the booster dose at 18-21 weeks (Einarsson et al 2009;Batorek et al 2012;Kubale et al 2013;Li et al 2015;Shi et al 2016;Needham et al 2017). In these cases, the eff ect of vaccination may persist for as long as 22 weeks (Zamaratskaia et al 2008;Einarsson et al 2009).…”

“…These changes include a reduced diameter of the seminiferous tubules, a reduced number of interstitial endocrine cells and a reduction of germinal epithelium ). These immunocastration effects persist for 22-26 weeks after the second/booster vaccination, as manifested in androstenone and skatole levels, the size of reproductive organs (Einarsson et al 2011;Han et al 2017) and histomorphological traits observed using light and/or electron microscopy (Kubale et al 2013;Li et al 2015;Han et al 2017).…”