Detection and partial characterization of an anti-steroidogenic peptide from the humoral immune system of the chicken

Isolation and potential immunological characterization of TPSGLVY, a novel bursal septpeptide isolated from the bursa of Fabricius

The bursa of Fabricius is central immune organ unique to birds, and the extract is immunocompetent in stimulating B cell differentiation and enhancing antibody production. However, except for bursin, the active peptides from the bursa of Fabricius are little reported. In the paper, a novel bursal septpeptide (BSP-II) with the amino acids sequence of TPSGLVY was identified and similar to the MGC53864 protein of Gallus gallus. We investigated the effects of BSP-II on the immune response in terms of the antibodies titers (IgG1 and IgG2alpha), the levels of interferon-gamma and interleukin-4 cytokines, spleen cell lymphocyte proliferation, and the T-lymphocyte subtype composition. It was noteworthy that BSP-II potentiates the Th1 and Th2-type immune responses in dose-dependent manner. BSP-II had specific enhancing effects on the hybridoma SP2/0 cell proliferation at two different serum concentrations (20% and 5%), but had no connection with the dose of BSP-II. The antibody secreting level of hybridoma SP2/0 cells rose in 5% and 20% serum when the concentrations of BSP-II increased. Also, BSP-II had effect on the viabilities of tumor cells (Hela and SP2/0). All the results indicated that BSP-II was able to significantly induce various immune responses and involved in the cell viability of different tumor cell lines. Our observations implied that BSP-II might be a novel biological active factor from the bursa of Fabricius with immunomodulatory activities.

Characterization of intraperitoneal, orthotopic, and metastatic xenograft models of human ovarian cancer

Improvement of ovarian cancer patient outcome requires well-characterized animal models in which to evaluate novel therapeutics. Xenograft models are frequently used, but with little discussion of disease histology. The objectives of this study were to inject 11 ovarian cancer cell lines intraperitoneally (ip), and a subset intrabursally (ib; orthotopic), into nude mice and to analyze the resulting pathologies. Eight of 11 lines injected ip formed tumors within 3 months at variable rates with the following histological subtype distribution: one endometrioid, one serous, one clear cell, and five undifferentiated. Only mice injected with A2780-cp cells presented with ovarian-specific metastases (11 of 88), and the survival time of these animals was significantly shorter, which may be attributed to the higher proliferation rate as determined by Ki67 positivity. Additional analysis of the influence of the ovarian microenvironment on cell characteristics was conducted with ib injection of two cell lines (OVCA 429 and ES-2). The site of injection did not affect the tumor histology, the effect on proliferation was cell-type dependent, and the tumor take rate (cell survival) was negatively affected for OVCA 429 cells. The animal models described herein represent histologically distinct models of both early and late stage ovarian cancer useful for evaluation of therapeutics.

Effect of bursal anti-steroidogenic peptide and immunoglobulin G on neonatal chicken B-lymphocyte proliferation

In attempts to identify antibodies for Bursal Anti-Steroidogenic Peptide (BASP), rabbit serum was observed to reduce phorbol ester-stimulated chicken B-lymphocyte proliferation comparable to BASP. These experiments investigated the effects of IgG on B-lymphocyte proliferation. In Experiment 1, 3% rabbit serum decreased B-lymphocyte proliferation. In Experiment 2, 2 mg/ml of intact rabbit IgG or 0.65 mg/ml of IgG papain digest products, Fab and Fc, decreased B-lymphocyte proliferation. The combination of BASP and either Fab or Fc was observed to have at least an additive anti-proliferative effect. In Experiment 3, 0.01 mg/ml of either rabbit or chicken IgG, or 1.0 mg/ml of rabbit or 0.01 mg/ml of chicken Fab, Fc, and the pepsin digestion product F(ab')(2) was observed to have an anti-proliferative effect. No combined effects of BASP and IgG or IgG digest products were observed for this experiment. In Experiment 4, 12 mg/ml of chicken egg yolk IgG or 1.2 mg/ml Fab was found to suppress B-lymphocyte proliferation. Additionally, an additive effect of 12 mg/ml of IgG with BASP was again observed. The present studies suggest that IgG and its digestion products reduce phorbol-stimulated B-lymphocyte proliferation in vitro and combined treatment with IgG and BASP may have at least an additive anti-proliferative effect on B-lymphocyte proliferation.

Relationship of bursal anti-steroidogenic peptide (BASP) and histone H1

Previous in vitro research from our laboratory has demonstrated the existence of a protein purified from the chicken bursa of Fabricius, with potent antisteroidogenic and antiproliferative action on granulose cells and lymphocytes, respectively called Bursal anti-steroidogenic peptide (BASP). This protein is heat-labile, basic, and amino- and carboxy-terminus blocked. In highly purified form, the protein presents as a doublet on SDS-PAGE electrophoresis with an apparent MW of approximately 29 and approximately 32 kDa. Recently, Nanoflow Q-TOF Mass Spectrometry amino acid sequencing allowed determination of a convincing partial amino acid sequence, strongly suggesting a probable relationship of BASP with histone H1. Bursal cDNA expression library screening, using an antibody produced against BASP, also identified a clone with a sequence matching histone H1. Presently, we have demonstrated that SDS-PAGE electrophoresis of highly purified and bioactive BASP, and commercially-available calf thymus derived histone H1, produced similar doublets at approximately the same apparent MW, and that the electrophoretic profile of these 2 preparations were strikingly similar following 2 dimensional gel electrophoresis. The BASP doublet produced on SDS-PAGE was recognized by a commercially available monoclonal antibody recognizing a highly conserved region of histone H1. Furthermore, calf thymus histone H1 was found to suppress mitogen-stimulated chicken B-cell proliferation in a concentration-related manner, similar to the action of BASP. These data indicate that BASP shares substantial structural homology with, and may be identical to, histone H1.

Bursal anti-steroidogenic peptide (BASP): modulation of mitogen-stimulated bursal-lymphocyte DNA synthesis

The present study examined the effects of bursal anti-steroidogenic peptide (BASP) on mitogen-induced DNA synthesis in bursa-derived B-lymphocytes in short-term culture. Partially purified extracts of chicken bursa of Fabricius tissue, containing BASP, significantly (P < 0.05) reduced DNA synthesis in bursal-lymphocytes exposed to increasing concentrations of phorbol 12,13-dibutyrate (PDB). Following these initial observations, BASP, further purified from bursal extracts using sequential rpHPLC fractionation, was observed to reduce (P < 0.05) both B-lymphocyte PDB-stimulated DNA synthesis and ovarian granulosa cell progesterone biosynthesis with bioactivity observed at similar retention times in each assay, suggesting that each bioactivity may be due to the same or similar molecules. A similar BASP-enriched fraction was not effective in altering basal levels of DNA synthesis in chick embryonic kidney cells. Subsequently, BASP was further purified by several sequential chromatographic methods including: C-18 rpHPLC (preparative rpHPLC followed by a semi-preparative rpHPLC column), cation exchange chromatography, molecular sieve HPLC chromatography, and SDS-PAGE. Biologically active material was observed at approximately 29 or 34 kDa. Protein concentration was determined and bioactivity was evaluated. Anti-proliferative effects of this partially purified BASP on bursal-lymphocytes was observed at concentrations as low as 1.6 micrograms ml-1, with complete suppression of mitogen-stimulated DNA synthesis observed at approximately 25 micrograms ml-1. This partially purified BASP was also efficacious for attenuation of ovarian granulosa cell progesterone biosynthesis at concentrations as low as 0.4 microgram ml-1, with complete suppression of gonadotrophin-stimulated progesterone biosynthesis observed at approximately 0.8 microgram ml-1. While BASP is efficacious for attenuation of both granulosa cell steroidogenesis and bursal-lymphocyte proliferation, these data suggest that BASP is much more potent with regard to anti-steroidogenic activity.

Effect of bursal antisteroidogenic peptide (BASP) on chicken embryonic pituitary secretion of growth hormone (GH) and prolactin (PRL): evaluation in a reverse hemolytic plaque assay (RHPA)

Using the reverse hemolytic plaque assay described in the present investigation, a secretagogue activity of bursal antisteroidogenic peptide (BASP) for growth hormone (GH) or prolactin (PRL) secretion was observed in chicken Day 20e pituitary cell monolayers. Partially purified BASP (ppBASP), at all concentrations evaluated (0.25 BEQ/ml, 0.75 BEQ/ml, or 1.5 BEQ/ml), induced PRL secretion by isolated lactotrophs above (P < 0.05) basal levels during the 2- and 6-hr incubation. At the 18-hr time point, neither ppBASP nor vasoactive intestinal polypeptide (VIP) was efficacious (P < 0.05) in causing an elevation in PRL-secreting cells above basal levels. ppBASP, at all concentrations evaluated (0.25 BEQ/ml, 0.75 BEQ/ml, or 1.5 BEQ/ml), caused an increase in the percentage of GH-secreting cells above (P < 0.05) basal levels during the 18-hr incubation. When evaluating the 2-hr time point alone, ppBASP, at 0.75 or 1.5 BEQ/ml, significantly (P < 0.05) elevated the percentage of GH-secreting cells to above basal levels. After the 6-hr incubation, ppBASP at 0.25 or 0.75 BEQ/ml, was efficacious in causing elevated (P < 0.05) GH secretion above basal levels. The present study indicates a secretagogue activity of BASP on PRL or GH secretion by chicken embryonic anterior pituitary cells in vitro.

BASP-induced suppression of mitogenesis in chicken, rat and human PBL

The purpose of the present investigation was to extend previous research conducted by our laboratory which demonstrated the suppressive effects of chicken bursa of Fabricius-derived bursal anti-steroidogenic peptide (BASP) on neonatal-chick B-lymphocyte mitogenesis. To test these anti-proliferative effects on lymphocytes derived from older animals, and to evaluate the phylogenetic applicability of these findings to other species, we evaluated the ability of BASP to alter proliferative indices in peripheral blood lymphocytes derived from adult chickens, rats and humans. Data from the present series of experiments confirm and extend our previous findings and suggest an anti-proliferative effect, exerted by BASP, on pools of isolated PBL from chickens, rats and humans, when measuring 3H-thymidine incorporation following mitogenic stimulation. While the present data was derived from limited numbers of pooled PBL, these findings may be indicative of a potential extra-bursal function of BASP on lymphocyte function.

Effect of bursal anti-steroidogenic peptide (BASP) on cortisol biosynthesis in ACTH-stimulated canine adrenocortical carcinoma cells in vitro

Previous studies from our laboratory have demonstrated that bursal anti-steroidogenic peptide (BASP) inhibits progesterone biosynthesis from ovine luteinizing hormone-stimulated chicken ovarian granulosa cells. In the present investigation, we evaluated the efficacy of BASP for reducing cortisol secretion from normal canine adrenocortical cells and neoplastic adrenocortical cells from a dog with Cushing's syndrome. Treatment of adrenocortical cells derived from either normal healthy dogs or a cushingoid dog with adrenocorticotropic hormone (ACTH; 0-10 nM) caused an approximately two-fold increase in cortisol production from both normal or tumor derived adrenocortical cells. Small but significant decreases (up to 34%) in cortisol production were observed from normal and tumor derived canine adrenocortical cells when exposed to increasing concentrations of BASP (0.0-0.15 bursal equivalents; BEQ). Incubation of adrenocortical carcinoma cells or normal adrenocortical cells with ACTH (0-10 nM) and BASP (0.0-0.15 BEQ) increased cyclic AMP formation up to 2.5-fold. Interestingly, BASP suppressed basal cortisol production from tumor derived adrenocortical cells to normal levels when compared to the basal cortisol levels from normal derived adrenocortisol cells. Data from the present studies indicate that BASP is capable of suppressing basal and ACTH-stimulated cortisol production from normal or tumor derived adrenocortical cells in vitro. The possible clinical efficacy of homologous canine BASP on canine adrenal function or chicken BASP in other species of animals remains to be evaluated.

Bursal antisteroidogenic peptide alters the activity of steroidogenic enzymes in chicken granulosa cells

We have previously reported that a peptide from chicken bursa of Fabricius, bursal antisteroidogenic peptide (BASP), inhibits luteinizing hormone-stimulated progesterone biosynthesis by chicken ovarian granulosa cells. The objective of this study was to determine the site(s) of BASP inhibition within the steroidogenic pathway of chicken granulosa cells. The effects of BASP on key steroidogenic enzymes, including adenylyl cyclase (AC), phosphodiesterase, the cholesterol side-chain cleavage enzyme complex and 3 beta-hydroxysteroid dehydrogenase were determined. Luteinizing hormone (10 ng/tube) stimulated a fivefold increase in granulosa cell progesterone production that was inhibited by BASP (0.06, 0.12 or 0.25 bursal equivalents) in a dose-dependent manner. Luteinizing hormone stimulated a sixfold increase in cyclic 3',5'-adenosine monophosphate (cAMP) formation, and this increase was potentiated by BASP in a dose-dependent manner. In addition, BASP stimulated cAMP formation in the absence of luteinizing hormone without affecting progesterone production. The AC activator forskolin (0.1 mM) stimulated a 4.5-fold increase in progesterone synthesis, which was inhibited by BASP. In the presence of forskolin. BASP increased cAMP formation in a dose-dependent manner. A fivefold increase in progesterone synthesis induced by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (1.0 mM) was inhibited by BASP. In the presence of 3-isobutyl-1-methylxanthine, BASP increased cAMP formation in a dose-dependent manner. Finally, 22(R)-hydroxycholesterol (250, 500, 1,000, or 2,500 ng/tube) or pregnenolone (50, 100, 200, or 500 ng/tube) resulted in up to 15- or 10-fold increases in progesterone production, respectively. Increasing concentrations of BASP caused a dose-dependent suppression of the conversion of 22(R)-hydroxycholesterol, but not pregnenolone, to progesterone. The inhibition of steroidogenesis by BASP is not associated with reduced cAMP levels, and BASP appears to strongly stimulate AC activity. In addition, these findings suggest that BASP may limit the availability of progesterone precursors by inhibiting the activity of the cholesterol side-chain cleavage enzyme complex.

The effect of the humoral immune system-derived bursal anti-steroidogenic peptide (BASP) on corticosteroid biosynthesis in avian, porcine and canine adrenal cortical cells

Utilizing avian, porcine and canine adrenocortical cells, we have examined the effect of bursal anti-steroidogenic peptide (BASP) on adrenocorticotropin (ACTH) and dibutyryl cyclic AMP (DB-cAMP)-stimulated corticosteroid and cAMP formation. BASP significantly (P < 0.05) suppressed corticosteroid production from adrenocortical cells derived from chickens, pigs and dogs. BASP significantly increased cAMP formation (up to 10-fold) in a dose-related manner. These findings suggest that BASP structure and activity may be conserved between chicken, porcine and canine species.