Theileria parasites secrete a prolyl isomerase to maintain host leukocyte transformation.

Infectious agents develop intricate mechanisms to interact with host cell pathways and hijack their genetic and epigenetic machinery to change host cell phenotypic states. Among the Apicomplexa phylum of obligate intracellular parasites, which cause veterinary and human diseases, Theileria is the only genus that transforms its mammalian host cells. Theileria infection of bovine leukocytes induces proliferative and invasive phenotypes associated with activated signalling pathways, notably JNK and AP-1 (ref. 2). The transformed phenotypes are reversed by treatment with the theilericidal drug buparvaquone. We used comparative genomics to identify a homologue of the peptidyl-prolyl isomerase PIN1 in T. annulata (TaPIN1) that is secreted into the host cell and modulates oncogenic signalling pathways. Here we show that TaPIN1 is a bona fide prolyl isomerase and that it interacts with the host ubiquitin ligase FBW7, leading to its degradation and subsequent stabilization of c-JUN, which promotes transformation. We performed in vitro and in silico analysis and in vivo zebrafish xenograft experiments to demonstrate that TaPIN1 is directly inhibited by the anti-parasite drug buparvaquone (and other known PIN1 inhibitors) and is mutated in a drug-resistant strain. Prolyl isomerization is thus a conserved mechanism that is important in cancer and is used by Theileria parasites to manipulate host oncogenic signalling.

Polyethylenimine-mediated in vivo gene transfer of a transmembrane superantigen fusion construct inhibits B16 murine melanoma growth.

Immunotherapy has been proposed as a therapeutic strategy in advanced-stage melanomas in which other therapeutic options have little effect. The Staphylococcus enterotoxin A (SEA) has been used to stimulate an antitumoral immune response but its use is hampered by severe systemic side effects. Here, we show that SEA can be targeted to melanoma cells to limit these side effects. More specifically, we used a nonviral vector, the cationic polymer, polyethylenimine (PEI), to express a transmembrane SEA fusion construct (pSEA-TM) in B16F10-induced subcutaneous melanoma in mice. The efficacy of this in vivo transfection was enhanced by concomitant infusion of epinephrine to induce local vasoconstriction. In these conditions, repeated injections of pSEA-TM/PEI complexes elicited a significant response, as evidenced by tumor growth inhibition, without systemic adverse effects. T cell infiltration of the tumors, together with positive lymphocyte proliferation tests, suggested local and systemic immune responses. Altogether, PEI-mediated targeting of SEA to melanoma tumor cells in vivo efficiently stimulates the antitumor immune response without inducing the side effects observed with systemic administration of SEA.

Peptide hormone covalently bound to polyelectrolytes and embedded into multilayer architectures conserving full biological activity.

We report the development of new bioactive coatings of biomaterials based on the alternate deposition of oppositely charged polyelectrolytes. We selected polylysine (PLL) and poly(glutamic acid) (PGA) for the polyelectrolytes and murine melanoma cells as a biological test model system. These cells respond specifically to a small peptide hormone, alpha-melanocortin, which is a potent stimulator of melanogenesis. We show that a synthetic alpha-melanocortin derivative, covalently coupled to PLL forming the outer layer of a multilayer film remains as biologically active as the free hormone. Furthermore, the long time activity of the hormone is maintained when embedded in multilayer architectures whereas its short time activity depends on integration depth. The embedding of bioactive molecules not only anchors them irreversibly on the biomaterial, but opens also the possibility to control their activity. In comparison to conventional coating methods, polyelectrolyte multilayers are easy to prepare and retain their biological activity after storage as dry material. These very flexible systems allow broad medical applications for implant and tissue engineering.

Enhancement of gene delivery by an analogue of alpha-MSH in a receptor-independent fashion.

In order to transfect melanoma specifically by receptor-mediated endocytosis we prepared dioctadecyl aminoglycylspermine (lipospermine)--DNA complexes with [Nle(4),D-Phe(7)]-alpha-MSH(4--10), a pseudo-peptide analogue of alpha-melanocyte stimulating hormone (alpha-MSH) linked to a thiol-reactive phospholipid. With these complexes we obtained an up to 70-fold increase of transfection with B16-F1 melanoma cells. However when B16-G4F, an alpha-MSH receptor negative melanoma cell line was transfected, an up to 700-fold increased transfection efficiency was observed. The peptide hormone analogue was equally efficient when it was only mixed with lipospermine--DNA complexes without covalent coupling. In addition to melanoma cells we also obtained up to 30-fold increased transfection with BN cells (embryonic liver cells). Our data show that an alpha-MSH analogue increased transfection independently of the MSH receptor expression but reaches efficiencies approaching those obtained with peptides derived from viral fusion proteins. The absence of targeting of constructs containing [Nle(4),D-Phe(7)]-alpha-MSH(4-10) can probably be attributed due to the relatively modest number of MSH receptors at the surface of melanoma. We suggest, however, that the peptide hormone analogue used in this study has membrane-active properties and could be of interest as helper agent to enhance non-viral gene delivery presumably by endosomal-destabilizing properties.

Analysis of [3H]bremazocine binding in single and combinatorial opioid receptor knockout mice.

Despite ample pharmacological evidence for the existence of multiple mu-, delta- and kappa-opioid receptor subtypes, only three genes encoding mu-(MOR), delta-(DOR) and kappa-(KOR) opioid receptor have been cloned. The KOR gene encodes kappa(1)-sites, which specifically bind arylacetamide compounds, and the possible existence of kappa-opioid receptor subtypes derived from another kappa-opioid-receptor gene, yet to be characterized, remains a very contentious issue. kappa(2)-Opioid receptors are described as binding sites typically labelled by the non-selective benzomorphan ligand [3H]bremazocine in the presence of mu-, delta- and kappa(1)-opioid receptor blocking ligands. To investigate the genetic origin of kappa(2)-opioid receptors, we have carried out homogenate binding experiments with [3H]bremazocine in brains of single MOR-, DOR-, KOR- and double MOR/DOR-deficient mice. Scatchard analysis showed that 68+/-12% of the binding sites arise from the MOR gene, 27+/-1% from the DOR gene and 14.5+/-0.2% from the KOR gene, indicating that the three known genes account for total [3H]bremazocine binding. Experiments in the presence of mu-, delta- and kappa(1)-opioid receptor suppressor ligands further showed that non-kappa(1)-opioid receptor labelling can be accounted for by binding to both the mu- and delta-opioid receptors. Finally, [3H]bremazocine binding experiments performed on brain membranes from the triple MOR/DOR/KOR-deficient mice revealed a complete absence of binding sites, confirming definitively that no additional gene is required to explain the total population of [3H]bremazocine binding sites. Altogether the data show that the putative kappa(2)-opioid receptors are in fact a mixed population of KOR, DOR and predominantly MOR gene products.

Mice deficient for delta- and mu-opioid receptors exhibit opposing alterations of emotional responses.

The role of the opioid system in controlling pain, reward and addiction is well established, but its role in regulating other emotional responses is poorly documented in pharmacology. The mu-, delta- and kappa- opioid receptors (encoded by Oprm, Oprd1 and Oprk1, respectively) mediate the biological activity of opioids. We have generated Oprd1-deficient mice and compared the behavioural responses of mice lacking Oprd1, Oprm (ref. 6) and Oprk1 (ref. 7) in several models of anxiety and depression. Our data show no detectable phenotype in Oprk1-/- mutants, suggesting that kappa-receptors do not have a role in this aspect of opioid function; opposing phenotypes in Oprm-/- and Oprd1-/- mutants which contrasts with the classical notion of similar activities of mu- and delta-receptors; and consistent anxiogenic- and depressive-like responses in Oprd1-/- mice, indicating that delta-receptor activity contributes to improvement of mood states. We conclude that the Oprd1-encoded receptor, which has been proposed to be a promising target for the clinical management of pain, should also be considered in the treatment of drug addiction and other mood-related disorders.

T cell receptor beta chain usage in myelin basic protein-specific rat T lymphocytes.

Myelin basic protein (MBP)-specific T cell lines and clones have been established from rats of the major histocompatibility complex (MHC)-compatible Lewis and BS strains. All lines and clones are MHC class II restricted and share the CD4+ phenotype. The cells proliferate specifically in response to either a peptide representing amino acids #68-88 of guinea pig MBP, to residues #47-67 or to an unidentified myelin antigen which is distinct from MBP. All lines and clones specific for MBP express the same T cell receptor (TcR) variable (V) beta chain element, which is homologous to the mouse V beta 8.2 gene segment. Three lines/clones with the same antigen fine specificity have identical V beta D beta J beta junctions on the protein level, a region which represents part of the potential antigen-binding portion of the TcR; two of the lines express members of the V alpha 2 family. These results suggest biased usage of TcR V beta elements in rat T cells specific for MBP. Our findings broaden the basis for a rational therapeutic strategy to specifically intervene in the rodent model system of experimental allergic encephalomyelitis.

IgD/lambda plasmocytoma with immunoglobulin kappa light-chain genes in the germ-line configuration.

Human immunoglobulin (Ig) genes are rearranged in an ordered sequence of events during B-cell differentiation: starting at the IgH locus, a productive VHDJH rearrangement leads to the expression of mu chains. Light-chain gene rearrangements have been found in pre-B cells which express mu chains. In these cells rearrangements of Ig kappa light-chain genes precede that of lambda genes. In an IgD/lambda-producing plasmocytoma, however, we found an apparent exception to this rule: the kappa genes were not rearranged. Together with the observation that roughly 90% of human IgD plasmocytomas produce lambda light-chain proteins, the finding reported here leads us to suggest that lambda light-chain genes are rearranged preferentially in IgD-producing plasma cells. Ig gene rearrangement, isotype switch, and the phenomenon of isotypic and allelic exclusion are discussed with special reference to our findings.

Suppression of experimentally induced autoimmune encephalomyelitis by cytolytic T-T cell interactions.

Down-regulatory phenomena have been described in several experimental models of tissue-specific, T-cell-mediated autoimmunity. For example, resistance to active induction of experimental autoimmune encephalomyelitis (EAE) can be induced by pretreating animals with non-pathogenic inocula of autoantigen or effector cells. Moreover, animals that have recovered from one EAE episode are resistant to subsequent induction of EAE. In some models, resistance to EAE has been transferred with immune cells to naive recipients. These experiments, which were based on transfers of unseparated immune cell populations, are difficult to interpret. Immune suppression circuits are known to be complex and involve various distinct cellular subsets. To further complicate the issue, resistance to EAE can be transferred not only by suppressor cells, but also by encephalitogenic effector cells injected in 'subclinical' doses. We describe now the isolation of homogeneous T lymphocyte lines from the spleens of Lewis rats that had recovered from T-cell-mediated EAE (tEAE) caused by the MBP-specific T cell line S1. These spleen-derived T line cells express the CD8 phenotype and specifically respond to determinants on the inducing S1 line, but not to the autoantigen MBP. Furthermore, the anti-S1 cells selectively lyse the encephalitogenic S1 T line in vitro and efficiently neutralize their encephalitogenic capacity in vivo.

Mammalian T-lymphocyte antigen receptor genes: genetic and nongenetic potential to generate variability.

T lymphocytes of higher vertebrates are able to specifically recognize a seemingly unlimited number of foreign antigens via their receptors, the T cell antigen receptors (TCRs). T lymphocytes mature by passing through the thymus and acquire antigen specificity by expressing the TCR molecules on their cell surface. Genetic and somatic diversification mechanisms give rise to the enormous degree of TCR variability observed in mature T cells: germline and combinatorial diversity as well as junctional and the so-called N-region diversity. In contrast to the situation in immunoglobulin genes somatic hypermutation does not seem to play a significant role in TCR diversification. It is argued here that the enzyme terminal nucleotidyl-transferase is potentially a major factor in generating the immense diversity. We propose furthermore that this enzyme ensures the flexibility of T cell responses to novel antigens by random insertion of so-called N-region nucleotides. Apart from the physiological functions of TCR genes any involvement in the etiology of T cell neoplasia remains to be proven.