Germ cell development in equine testis tissue xenografted into mice

Grafting of testis tissue from immature animals to immunodeficient mice results in complete spermatogenesis, albeit with varying efficiency in different species. The objectives of this study were to investigate if grafting of horse testis tissue would result in spermatogenesis, and to assess the effect of exogenous gonadotropins on xenograft development. Small fragments of testis tissue from 7 colts (2 week to 4 years of age) were grafted under the back skin of castrated male immunodeficient mice. For 2 donor animals, half of the mice were treated with gonadotropins. Xenografts were analyzed at 4 and 8 months post-transplantation. Spermatogenic differentiation following grafting ranged from no differentiation to progression through meiosis with appearance of haploid cells. Administration of exogenous gonadotropins appeared to support post-meiotic differentiation. For more mature donor testis samples where spermatogenesis had progressed into or through meiosis, after grafting an initial loss of differentiated germ cells was observed followed by a resurgence of spermatogenesis. However, if haploid cells had been present prior to grafting, spermatogenesis did not progress beyond meiotic division. In all host mice with spermatogenic differentiation in grafts, increased weight of the seminal vesicles compared to castrated mice showed that xenografts were releasing testosterone. These results indicate that horse spermatogenesis occurs in a mouse host albeit with low efficiency. In most cases, spermatogenesis arrested at meiosis. The underlying mechanisms of this spermatogenic arrest require further investigation.

Proteomic profiling distinguishes astrocytomas and identifies differential tumor markers

Methods to permit more precise delineation of astrocytomas of different grades may have therapeutic utility. The authors selectively microdissected pure populations of cells from normal brain and astrocytomas. They performed two-dimensional protein gel electrophoresis (2DGE) followed by protein sequencing. Differential expression was confirmed immunohistochemically. 2DGE identified proteomic patterns and proteins that differentiated normal brain from tumor and distinguished astrocytomas of increasing grade.

A random search methodology for examining parametric uncertainty in water quality models

The advent of the modern high-speed digital computer has tremendously enhanced the utility of Monte Carlo methods for evaluating complex environmental simulation models. In particular, random searching is becoming popular, as thousands of model runs can now be executed quickly and with minimal effort. Indeed, the issues of computational burden and inefficiency, hitherto the bane of random searching, are now receding. This paper presents one such method, uniform covering by probabilistic rejection (UCPR), which combines a pure random search with a probabilistic rejection algorithm that significantly enhances its efficiency. Using nearest-neighbor distances, an ensemble of points in a predefined parameter sampling domain migrates to locate and define a final distribution of optimal parameter vectors, thus providing a realistic depiction of parameter uncertainty. In a prototypical case study of the Oconee River (Georgia, USA), UCPR and regionalized sensitivity analysis, are employed for identifying the parameters of sediment-transport-associated nutrient dynamics, a dynamic river water quality model. Results indicate the existence of a complex interactive parameter structure, evidenced by multiple sets of optimal points widely dispersed over a broad domain of feasible parameter values.

93 CALCIUM REMOVAL INCREASES THE PROTECTIVE EFFECTS OF β-CYCLODEXTRIN PLUS CHOLESTEROL ON PORCINE SPERM DURING COLD SHOCK

Porcine sperm are extremely sensitive to the damaging effects of cold shock and cryopreservation. Cholesterol-binding molecules, such as 2-hydroxypropyl-�-cyclodextrin (HBCD), improve post-thaw and post-cooling porcine sperm viability when added to an egg yolk-based extender, but also enhance sperm capacitation in other species. Depending upon the environmental cholesterol content, HBCD can act either as a cholesterol shuttle or sink to increase or decrease, respectively, sperm plasma membrane cholesterol content. Increasing the sperm cholesterol to phospholipid ratio reduces cold shock sensitivity whereas decreasing the ratio initiates the process of sperm capacitation. An increase in protein tyrosine phosphorylation correlates with sperm capacitation and has been shown to be dependent upon the presence of extracellular calcium. Sperm intracellular calcium also increases during cold shock. The objective of this study was to determine the combined effects of extracellular calcium and membrane cholesterol manipulation on porcine sperm viability and protein tyrosine phosphorylation following cold shock (10�C for 10 min). Viability was assessed using CFDA/propidium iodide staining. Protein tyrosine phosphorylation, previously shown to correlate with porcine sperm capacitation, was evaluated via antiphosphotyrosine (clone 4G10) immunoblots. We report here that following cold shock, porcine sperm incubated in defined medium containing both 0.8 mM HBCD and 0.5 mM cholesterol 3-sulfate (ChS) incubated in the absence of added extracellular calcium and the presence of 6 mM EGTA have significantly improved viability (90.5 � 6.3%, n = 3) when compared with cold-shocked sperm incubated in either the same medium with calcium (46.1 � 3.8%), without HBCD or ChS (26.5 � 7.4% with calcium; 46.5 � 13.1% without calcium), or with HBCD alone (17.0 � 7.4% with calcium, 36.8 � 7.5% without calcium). As we have found previously, treatment with 0.8 mM HBCD plus 0.5 mM ChS completely inhibited the increase in protein tyrosine phosphorylation induced by the cold shock treatment. Although protein tyrosine phosphorylation correlates with porcine sperm capacitation, the ability of cold shock treatment to induce the same phosphorylation pattern indicates that other processes or pathways may contribute to its appearance. Removing extracellular calcium consistently decreased, but did not completely eliminate, the protein tyrosine phosphorylation induced by cold shock. These results indicate that cold shock-induced protein tyrosine phosphorylation is not dependent upon, but can be modulated by, extracellular calcium. The combined effects of calcium, HBCD and ChS on viability suggest that porcine sperm viability following cold shock is best maintained by removing extracellular calcium and increasing membrane cholesterol content via the cholesterol shuttle activity of HBCD. This work was supported by grants from PA Dept. Ag. (ME 443291) and the NIH (5-K08-HD041430).

309 THE SPERMATOGENIC CYCLE IN MAMMALIAN TESTIS XENOGRAFTS

Grafting of immature testis tissue from different mammalian donor species into mouse hosts results in production of spermatozoa from the donor species. Xenografting of testis tissue from rhesus monkeys, pigs, and sheep accelerates sperm production. To determine whether this shortened time to sperm production is due to the reduced spermatogenic cycle length, we applied bromodeoxyuridine (BrdU) incorporation to analyze the spermatogenic cycle in porcine and ovine testis xenografts. Testes from 1-2-week-old Yorkshire cross pigs and 1-week-old Suffolk sheep were cut into small fragments (approximately 1 � 1 � 2 mm) and eight fragments were grafted under the back skin of each castrated male immunodeficient NCR nude recipient mouse (n = 7 for pig, n = 5 for sheep). Mice were given BrdU (100 mg/kg i.p.) at 7 months (porcine tissue) or 6 months (ovine tissue) post-transplantation. Mice carrying porcine tissue were sacrificed 1 h, 9 days or 18 days after BrdU injection. Mice with ovine testicular tissue were sacrificed 1 h, 11 days or 22 days after BrdU injection. Analysis time points were chosen based on the reported length of the spermatogenic cycle in pigs and sheep (approximately 9 days and 11 days, respectively). All eight stages of the spermatogenic cycle were analyzed to identify the most advanced germ cells labeled in each time period after BrdU injection. All seminiferous tubules containing full spermatogenesis were analyzed. Histologically, 51.8% (range 7 to 98%, n = 2040 tubules) of seminiferous tubules from porcine grafts, and 64.4% (range 2 to 92%, n = 2903 tubules) of seminiferous tubules from ovine grafts presented complete spermatogenesis. In porcine grafts, the most advanced germ cells labeled 1 h after BrdU injection were primary spermatocytes in pre-leptotene/leptotene at stage I of the spermatogenic cycle. At 9 days and 18 days after injection, the most advanced labeled germ cells were primary spermatocytes at pachytene at stage I and elongating spermatids at late stage II, respectively. In ovine grafts, the most advanced labeled germ cells at 1 h, 11 days and 22 days were pre-leptotene/leptotene at stage II, primary spermatocytes at the pachytene at stage I and elongating spermatids at stage II, respectively. These results indicate that each spermatogenic cycle in porcine and ovine testis xenografts lasts around 9 days and 11 days, respectively. Therefore, the length of the spermatogenic cycle is conserved in porcine and ovine testis xenografts and shortened time to sperm production is likely due to accelerated maturation of the testicular somatic components, such as Sertoli cells. This work was supported by NIH R01 RR17359-01.

Differential gene expression in hematopoietic progenitors from paroxysmal nocturnal hemoglobinuria patients reveals an apoptosis/immune response in 'normal' phenotype cells

Paroxysmal nocturnal hemoglobinuria (PNH) is an acquired stem cell disorder characterized clinically by intravascular hemolysis, venous thrombosis, and bone marrow failure. Despite elucidation of the biochemical and molecular defects in PNH, the pathophysiology of clonal expansion of glycosylphosphatidylinositol-anchored protein (GPI-AP)-deficient cells remains unexplained. In pursuit of evidence of differences between GPI-AP-normal and -deficient CD34 cells, we determined gene expression profiles of isolated marrow CD34 cells of each phenotype from PNH patients and healthy donors, using DNA microarrays. Pooled and individual patient samples revealed consistent gene expression patterns relative to normal controls. GPI-AP-normal cells from PNH patients showed upregulation of genes involved in apoptosis and the immune response. Conversely, genes associated with antiapoptotic function and hematopoietic cell proliferation and differentiation were downregulated in these cells. In contrast, the PNH clone of GPI-AP-deficient cells appeared more similar to CD34 cells of healthy individuals. Gene chip data were confirmed by other methods. Similar gene expression patterns were present in PNH that was predominantly hemolytic as in PNH associated with aplastic anemia. Our results implicate an environmental influence on hematopoietic cell proliferation, in which the PNH clone evades immune attack and destruction, while normal cells suffer a stress response followed by programmed cell death.

267 TESTIS TISSUE XENOGRAFTING AS A BIOASSAY FOR GERM CELL DEVELOPMENTAL POTENTIAL IN EQUINE CRYPTORCHID TESTES

In domestic animals, spermatogenic differentiation is blocked in abdominally retained testes exposed to core body temperature. It is not known if undifferentiated germ cells are retained in long-term cryptorchid equine testes, nor is it known whether any surviving germ cells retain their ability to progress through spermatogenesis. If functional germ cells do persist in equine abdominal testes, then the possibility exists that offspring could be derived even from bilaterally cryptorchid individuals. Previously, we reported an in vivo model where completion of spermatogenesis with production of spermatozoa capable of fertilization occurred in fragments of testicular tissue from immature mice, domestic animals, and monkeys grafted under the skin of immunodeficient mice. Therefore, spermatogenic development in testis tissue xenografts can serve as an in vivo assay system for the developmental potential of germ cells. The objective of this study was to investigate if cryptorchid horse testes that had been exposed to core body temperature for 1–3 years had retained developmentally competent germ cells. Small fragments of abdominally cryptorchid testis tissue (about 1 mm3) from three donor horses (1-, 2-, and 3-year-old Quarterhorse) were grafted under the back skin of castrated male immunodeficient mice (n = 8, 6, and 3 recipient mice, respectively). At the time of grafting, donor tissue did not contain differentiated germ cells. Histological examination of the testis xenografts was performed between 5 and 45 weeks post-transplantation. Weight of the seminal vesicles in the host mouse was recorded as an indicator of bioactive testosterone produced by the xenografts. By 28 weeks after grafting, pachytene spermatocytes were observed in xenografts from all cryptorchid donor testes. While haploid gametes would be expected to be present in xenografted testis tissue from descended equine testes by 35 weeks after grafting, spermatogenesis did not progress through meiosis in the cryptorchid grafts. In all recipient animals where spermatogenic differentiation occurred, the weight of the seminal vesicles in the castrated host mice was restored to pre-castration values, indicating that xenografts were capable of releasing biologically active testosterone. These results indicate that even after 3 years of exposure to core body temperature, equine cryptorchid testes contain germ cells capable of differentiation. It remains to be investigated if supplementation of exogenous gonadotropins might support post-meiotic differentiation of germ cells in cryptorchid equine testes xenografts. This work was supported by USDA 03-35203-13486.

268 GERM CELL DEVELOPMENT IN EQUINE TESTIS TISSUE XENOGRAFTED INTO MICE

Grafting of testis tissue from immature animals under the back skin of immunodeficient mice results in complete spermatogenesis, albeit with different levels of efficiency in different species. While spermatogenesis develops comparably to that in the donor species in xenografts from pigs, sheep and goats, spermatogenic differentiation is less efficient in testis tissue from cats and bulls. Testicular maturation was significantly accelerated in rhesus monkey testis grafts whereas timing was similar to that in the donor species in cats and bulls. The objective of this study was to investigate if grafting of immature horse testis tissue would result in spermatogenesis in a mouse host. Small fragments of testis tissue (about 1 mm3) from four sexually immature colts (2-week-old Standardbred, 5- and 8-month-old ponies, 10-month-old Warmblood) were grafted under the back skin of castrated male immunodeficient mice (n = 5, 5, 10 and 5 recipient mice, respectively). Histological examination of the testis xenografts was performed between 14 and 50 week post-transplantation. Weight of the seminal vesicles in the host mouse was recorded as an indicator of bioactive testosterone produced by the xenografts. At the time of grafting, the seminiferous cords of the donor testis tissue form 2-week-, 5-month- and 8-month-old colts contained only immature Sertoli cells and gonocytes. No spermatogenic differentiation occurred in xenografts from the 2-week-old colt and testosterone production was minimal. Pachytene spermatocytes were observed in testis grafts from the 5- and 8-month-old donors from 14 weeks onward. Spermatogenesis did not proceed through meiosis in grafts from the 5-month-old donor. Recipient mice carrying xenografts from the 8-month-old donor received exogenous gonadotropins (equine chorionic gonadotropin and human chorionic gonadotropin, 10 I.U./day for 2 months, beginning 14 weeks after grafting) and condensing spermatids were observed by 35 weeks after grafting. In donor tissue from the 10-month-old colt, pachytene spermatocytes were present in about 50% of tubules at the time of grafting. After 14 weeks, xenografts showed fewer differentiated germ cells than the donor tissue. However, at 35 weeks after grafting, condensing spermatids were observed, indicating that differentiated germ cells were initially lost and spermatogenesis was subsequently reinitiated. In all castrated host mice where spermatogenic differentiation occurred, the weight of the seminal vesicles was restored to pre-castration values showing that xenografts were releasing bioactive testosterone. These results indicate that horse spermatogenesis can occur in a mouse host albeit with low efficiency. Testicular maturation was not accelerated. In most cases, spermatogenesis appeared to become arrested at meiosis. The underlying mechanisms of this spermatogenic arrest require further investigation. Although equine testis xenografts produced testosterone, supplementation of exogenous gonadotropins might support post-meiotic differentiation. This work was supported by USDA 03-35203-13486.

193 TESTIS TISSUE XENOGRAFTING TO PRESERVE GERM CELLS FROM A CLONED BANTENG CALF

In April 2003, two banteng (Bos javonicus) calves were born after heterologous nuclear transfer of donor cells from a genetically valuable individual frozen in 1978. One of the cloned banteng calves died at one week of age. The calf was found to have one scrotal and one abdominally cryptorchid testis. In an attempt to preserve male germ cells from this valuable animal, parts of each testis were shipped on ice to the University of Pennsylvania for xenografting. Grafting of testis tissue from immature domestic animals and monkeys under the back skin of immunodeficient mice can result in complete spermatogenesis, albeit with different levels of efficiency in different species. The objective of this experiment was to investigate if grafting of immature banteng testis tissue would result in spermatogenesis in a mouse host. Small fragments of tissue (about 1 mm, 3 each) from both testes were grafted under the back skin (4 pieces of scrotal testis on the right side and 4 pieces of retained testis on the left side) of 6 castrated male immunodeficient mice. Histological examination of the testis xenografts was performed 3, 6, 9, 12, and 15 months after transplantation. Weight of the seminal vesicles in the host mouse was recorded as an indicator of bioactive testosterone produced by the xenografts. At the time of grafting, both testes contained seminiferous cords with immature Sertoli cells and gonocytes. At 3, 6, and 9 months after grafting, pachytene spermatocytes were present in the xenografts of the scrotal testis whereas no germ cell differentiation was observed in grafts from the retained testis. However, spermatogenesis in grafts of the scrotal testis did not proceed further through meiosis in grafts analyzed at 12 and 15 months after grafting, with pachytene spermatocytes still the most advanced germ cell type present in grafts recovered 15 months after grafting. The weight of the seminal vesicles in the castrated host mice was restored to pre-castration values showing that xenografts were releasing bioactive testosterone. These results indicate that banteng spermatogenesis was initiated in the mouse host but became arrested at meiosis as observed previously in xenografts of immature bovine or equine testis. Therefore, haploid germ cells could not be recovered. This represents the first example of trying to preserve fertility from a rare, valuable newborn animal by testis tissue xenografting. While xenografting presents a previously unavailable option for preservation of male germ cells from immature individuals, the efficiency of sperm production in testis xenografts appears to be variable and has to be determined empirically for different donor species. This work was supported by USDA 03-35203-13486.

High-throughput sample preparation procedures for the quantitation of a new bone integrin ανβ3 antagonist in human plasma and urine using liquid chromatography–tandem mass spectrometry

High throughput LC-MS/MS assays to quantitate a new alpha(nu)beta(3) bone integrin antagonist (I) in human plasma and urine have been developed using instruments programmed to automate sample preparation procedures. Packard liquid handling system-MultiPROBE II EX was programmed for preparing calibration standards in control plasma and urine, acidifying all standards, quality control (QC), and clinical samples with necessary dilutions, and adding the internal standard to the acidified samples. TOMTEC Quadra 96 was programmed to perform the solid phase extraction (SPE) process on a 3M 96-well mixed phase cation standard density (MPC-SD) plate to isolate the analytes from the sample matrix. The extract collected from both types of matrices was directly injected into reversed-phase LC-MS/MS system with a Turbo Ion Spray (TIS) interface in the positive ionization mode. The plasma and urine assays have the calibration range of 0.5-1500 and 2-6000 ng/mL, respectively. Validation of the automated and the manual plasma assays showed that application of MultiPROBE II to sample preparation gave comparable accuracy and precision. Overall, the automated approaches with minimum manual intervention enhanced the throughput of sample preparation.

Molecular genetic and proteomic analysis of synchronous malignant gliomas

Described is a patient with concurrent discrete gliomas: a pleomorphic xanthoastrocytoma with anaplastic features and an anaplastic oligoastrocytoma. The distinct and morphologically dissimilar tumors demonstrated similar genetic abnormalities by loss of heterozygosity and comparative genome hybridization. Clonality and proteomic analyses highlighted an independent origin for the two tumors. Proteomic methods may prove useful in cases where the differential diagnosis and pathogenetic origin of tumors are uncertain, as well as more globally for its ability to provide insight into specific expression of proteins that may serve as unique markers of tumorigenesis or as novel targets of therapy.

Influence of ORP variation, carbon source and nitrate concentration on denitrifying phosphorus removal by DPB sludge from dephanox process

The effect of added carbon source and nitrate concentration on the denitrifying phosphorus removal by denitrifying phosphorus removal bacteria sludge was systematically studied using batch experiments, at the same time the variation of ORP was investigated. Results showed that the denitrifying and phosphorus uptake rate in the anoxic phase increased with the high initial anaerobic carbon source addition. However, once the initial COD concentration reached a certain level, which was in excess of the PHB saturation of Poly-p bacteria, residual COD carried over to the anoxic phase inhibited the subsequent denitrifying phosphorus uptake. This was equal to supplementing the external carbon source to the anoxic phase, furthermore the higher the external carbon source concentration the more powerful the inhibition caused. High nitrate concentration in the anoxic phase increased the initial denitrifying phosphorus rate. Oncethe nitrate was exhausted, phosphate uptake changed to phosphate release. Moreover, the time of this turning point occurred later with the higher nitrate addition. On the other hand, through on-line monitoring the variation of the ORP with different initial COD concentration, it was found that ORP could be used as a control parameter for phosphorus release, but it is impossible to utilize ORP for controlling the dinitrification and anoxic phosphorus uptake operations.

T cell receptor VB repertoire diversity in patients with immune thrombocytopenia following splenectomy

In recent years, a pathophysiological role for T cells in immune thrombocytopenia (ITP) has been established. We applied cDNA size distribution analysis of the T cell receptor (TCR) beta-variable (VB) complementarity-determining region 3 (CDR3) in order to investigate T cell repertoire diversity among immune thrombocytopenia patients who had either responded or not responded to splenectomy, and compared them to normal controls. ITP patients who had had a durable platelet response to splenectomy showed a mean 2.8 +/- 2.1 abnormal CDR3 size patterns per patient, similar to healthy volunteers (2.9 +/- 2.0 abnormal CDR3 size patterns). In contrast, patients unresponsive to splenectomy demonstrated evidence of significantly more clonal T cell expansions than patients who had responded to splenectomy or controls (11.3 +/- 3.3 abnormal CDR3 size patterns per patient; P < 0.001). Of the VB subfamilies analysed, VB3 and VB15 correlated with response or non-response to splenectomy, each demonstrating oligoclonality in non-responding patients (P < 0.05). These findings suggest that removal of the spleen may lead directly or indirectly to reductions in T cell clonal expansions in responders, or that the extent of T cell clonality impacts responsiveness to splenectomy in patients with ITP.

[The relationship between anticardiolipin antibodies and fetal intrauterine growth retardation]

To investigate the relationship between anticardiolipin antibodies(ACA) and fetal intrauterine growth retardation(IUGR), serum ACA was determined in 60 pregnant women by enzyme linked immunosorbent assay(ELISA). Binding index(BI) of ACA-IgM or ACA-IgG in cases with IUGR(n = 30) was significantly higher than that in normal pregnant women(n = 30) (P < 0.05). There was no obvious relationship between the weight of neonate and BI of ACA-IgM(r = 0.1904), ACA-IgA(r = 0.1829) or ACA-IgG(r = 0.2013) in IUGR group. Increased ACA-IgM had a negative association with C3 (r = -0.4108, P < 0.05) and C4(r = -0.4092, P < 0.05), respectively. After routine therapy for IUGR during 27-35 weeks' gestation, the weights of neonates were 2436.87 +/- 437.29 gram in ACA-IgG positive group(n = 15) and 2905.33 +/- 195.95 gram in ACA-IgG negative group(n = 15). There was a statistical significance between these two groups(P < 0.01). It is concluded that ACA may play an important role in the pathogenesis of IUGR. The determination of ACA is also useful for early diagnosis and treatment of IUGR.

Histamine receptor type coupled to nitric oxide-induced relaxation of guinea-pig nasal mucosa

1 The aim of this study was to characterize the histamine receptor type mediating relaxation of the vascular bed of the nasal mucosa from the guinea-pig, and to determine the role of cyclo-oxygenase products and nitric oxide in this relaxant response to histamine. These studies were performed in isolated nasal mucosae examined in vitro to obtain potencies of histamine receptor-type selective agonists in causing vasorelaxation and to determine affinities of histamine receptor antagonists for inhibiting histamine-induced relaxation. 2 After contraction of nasal mucosae with noradrenaline, histamine caused a maximal relaxation response that was 75 +/- 6% of the contraction caused by noradrenaline with a mean EC50 value of 4.3 +/- 0.5 microM. Neither dimaprit (H2-receptor selective) nor R-alpha-methylhistamine (H3-receptor selective) caused significant relaxation of nasal mucosae. In contrast, betahistine (H1-receptor selective) caused an 81 +/- 7% relaxation of noradrenaline-induced tone with an EC50 value of 15 +/- 1 microM. 3 pA2 experiments were performed to obtain KB values of chlorpheniramine (H1-receptor selective) and diphenhydramine (H1-receptor selective) for blocking histamine-stimulated relaxation of nasal mucosae. KB values for chlorpheniramine (0.87 nM) and diphenhydramine (7.4 nM) were consistent with their interaction at the H1-receptor type. Additionally, neither 10 microM cimetidine (H2-receptor selective) nor 1 microM thioperamide (H3-receptor selective) had any effect on the relaxation curve for histamine. 4 In the presence of 10 microM indomethacin (cyclo-oxygenase inhibitor), histamine caused a maximal relaxation response of 73 +/- 5% of the noradrenaline-induced tone with an EC50 value of 2.9 +/- 0.2 microM, which was not different from control values (EC50 = 5.0 +/- 0.4 microM; maximal relaxation = 71 +/- 6%). In contrast, 200 microM NG-nitro-L-arginine (nitric oxide synthase inhibitor) completely inhibited histamine-induced relaxation of nasal mucosae. 5 In conclusion, data from the present study suggest only the H1-receptor type mediates relaxation of nasal mucosal blood vessels to histamine, and histamine-induced relaxation of nasal mucosae is entirely dependent on nitric oxide production.

Synthetic peptide epitope-based polymers: controlling size and determining the efficiency of epitope incorporation

The assembly of synthetic peptide-based vaccines that incorporate multiple epitopes is a major goal of vaccine development, because such vaccines will potentially allow the immunization of outbred populations against a number of different pathogens. We have shown that free radical-induced polymerization of individual peptide epitopes results in the incorporation of multiple copies of the same or different epitopes into high molecular weight immunogens (O'Brien-Simpson, N.M., Ede, N.J., Brown, L.E., Swan, J. & Jackson, D.C. (1997) Polymerization of unprotected synthetic peptides: a view toward synthetic peptide vaccines. J. Am. Chem. Soc.119, 1183-1188; Jackson, D.C., O'Brien-Simpson, N., Ede, N.J. & Brown, L.E. (1997) Free radical induced polymerization of synthetic peptides into polymeric immunogens. Vaccine 15, 1697-1705). The ability to control the size of these polymers, to determine the physical and chemical properties of the backbone material and also to know the extent to which individual peptide epitopes are incorporated are important manufacturing considerations and form the subject of this study. We show here that the polymerization process is highly efficient with at least 70% of peptides incorporated into the resulting polymer, that acrylamide and acryloylated amino acids can be used as comonomers with peptide epitopes in the polymerization reaction and that the choice of the comonomer can influence the properties of the resulting polymer. We also show that the size of chain growth polymers is restricted in the presence of chain transfer agents, that the resulting polymer size can be predicted and that there is little or no difference in the immunogenicity of polymers that range in apparent molecular size between 18 kDa and 335 kDa. The successful polymerization of peptide epitopes with an acryloyl-amino acid creates the potential for introducing different physical and chemical properties into artificial protein immunogens.

The central role played by peptides in the immune response and the design of peptide-based vaccines against infectious diseases and cancer

Vaccines are one of the most cost effective methods of improving public health thereby increasing the quality of life. Prophylactic and therapeutic treatment by vaccines can prevent infectious diseases and some cancers and could also be used in the treatment of autoimmune disorders. An appreciation of this potential has resulted in a burgeoning literature which not only describes the scientific efforts being made into designing new and improved vaccines but also drives the efforts being made by public health organizations world-wide in delivering vaccines to the community. At the forefront of technologies being applied to the design of vaccines is the use of synthetic peptides; the chemical technologies used to assemble peptides have made great strides over the last decade and assembly of hi-fidelity peptides which can be of high molecular weight, multimeric or even branched is now almost routine. Together with the advances in peptide technology our understanding of the molecular events that are necessary to induce immune responses has also made great strides. The central role that peptides play in immune recognition is now recognised and rules are emerging that are being applied to the construction of peptide-based vaccines that, in the right context, can induce humoral (antibody) and cellular (cytotoxic and helper T cell) immune responses. Synthetic peptides are exquisitely placed to answer questions about immune recognition and along the way to provide us with new and improved vaccines.

Poxvirus infection rapidly activates tyrosine kinase signal transduction

Viruses have evolved a number of strategies to gain entry and replicate in host target cells that, for human immunodeficiency virus (HIV) and the poxvirus, myxoma virus, involve appropriating chemokine receptors. In this report we demonstrate that activation of multiple intracellular tyrosine phosphorylation events rapidly ensues following virus adsorption to NIH 3T3.CD4.CCR5 cells and affects the ultimate level of myxoma virus replication. UV-inactivated myxoma virus induces the rapid phosphorylation of CCR5 on tyrosine residues, the association of CCR5 with Jaks and p56(lck), and their phosphorylation-activation within minutes of virus adsorption. Additionally, we provide evidence for myxoma virus-inducible signal transducers and activators of transcription (Stat) and insulin receptor substrate (IRS) activation. In contrast to CCR5 activation effected by HIV Env protein, these myxoma virus-inducible phosphorylation events are not sensitive to pertussis toxin treatment. Moreover, in cells that are non-permissive for myxoma virus infection, we provide evidence that myxoma virus fails to invoke this tyrosine phosphorylation cascade. Consistent with the observation that infection of CCR5-expressing cells is blocked by herbimycin A and the Jak 2 inhibitor, tyrophostin AG490, we infer that viral infectivity may be dependent on non-G-protein-coupled signal transduction pathways triggered by the infecting myxoma virus particle. This provides a novel post-binding mechanism by which viruses can co-opt a cellular receptor to permit productive virus infection.