Dugbe virus ovarian tumour domain interferes with ubiquitin/ISG15-regulated innate immune cell signalling.

The ovarian tumour (OTU) domain of the nairovirus L protein has been shown to remove ubiquitin and interferon-stimulated gene 15 protein (ISG15) from host cell proteins, which is expected to have multiple effects on cell signalling pathways. We have confirmed that the OTU domain from the L protein of the apathogenic nairovirus Dugbe virus has deubiquitinating and deISGylating activity and shown that, when expressed in cells, it is highly effective at blocking the TNF-α/NF-κB and interferon/JAK/STAT signalling pathways even at low doses. Point mutations of the catalytic site of the OTU [C40A, H151A and a double mutant] both abolished the ability of the OTU domain to deubiquitinate and deISGylate proteins and greatly reduced its effect on cell signalling pathways, confirming that it is this enzymic activity that is responsible for blocking the two signalling pathways. Expression of the inactive mutants at high levels could still block signalling, suggesting that the viral OTU can still bind to its substrate even when mutated at its catalytic site. The nairovirus L protein is a very large protein that is normally confined to the cytoplasm, where the virus replicates. When the OTU domain was prevented from entering the nucleus by expressing it as part of the N-terminal 205 kDa of the viral L protein, it continued to block type I interferon signalling, but no longer blocked the TNF-α-induced activation of NF-κB.

Wound healing in MIP-1alpha(-/-) and MCP-1(-/-) mice.

A salient feature of normal wound healing is the development and resolution of an acute inflammatory response. Although much is known about the function of inflammatory cells within wounds, little is known about the chemotactic and activation signals that influence this response. As the CC chemokines macrophage inflammatory protein-1alpha (MIP-1alpha) and monocyte chemotactic protein-1 (MCP-1) are abundant in acute wounds, wound repair was examined in MIP-1alpha(-/-) and MCP-1(-/-) mice. Surprisingly, wound re-epithelialization, angiogenesis, and collagen synthesis in MIP-1alpha(-/-) mice was nearly identical to wild-type controls. In contrast, MCP-1(-/-) mice displayed significantly delayed wound re-epithelialization, with the greatest delay at day 3 after injury (28 +/- 5% versus 79 +/- 14% re-epithelialization, P < 0.005). Wound angiogenesis was also delayed in MCP-1(-/-) mice, with a 48% reduction in capillary density at day 5 after injury. Collagen synthesis was impeded as well, with the wounds of MCP-1(-/-) mice containing significantly less hydroxyproline than those of control mice (25 +/- 3 versus 50 +/- 8 microg/wound at day 5, P < 0.0001). No change in the number of wound macrophages was observed in MCP-1(-/-) mice, suggesting that monocyte recruitment into wounds is independent of this chemokine. The data suggest that MCP-1 plays a critical role in healing wounds, most likely by influencing the effector state of macrophages and other cell types.

Quantification of epitope-specific MHC class-II-restricted T cells following lymphocytic choriomeningitis virus infection.

CD4(+) T cells are critical for the control of many viruses; however, the numbers of virus-specific CD4(+) cells that are expanded following infection are unknown. We have addressed this issue by enumerating virus-specific, MHC class-II-restricted T cells following infection of mice with lymphocytic choriomeningitis virus (LCMV). We have found that the numbers of T cells that produce interferon-gamma in response to stimulation with three different class-II-restricted LCMV epitopes increase from undetectable numbers in noninfected animals to between 4 x 10(5) and 2 x 10(6) cells per spleen at the peak of the T cell response. This contrasts with the numbers of virus-specific class-I-restricted T cells which expand to 1 x 10(7) to 2 x 10(7) cells per spleen during the same time period. We could not reproducibly detect virus-specific class-I-restricted or class-II-restricted T cells that produced interleukin-4 at any time following LCMV infection, indicating that infection with this virus induces a predominantly type 1 cytokine response. In contrast to the rapid decrease in the numbers of class-I-restricted T cells, the numbers of LCMV-specific class-II-restricted T cells declined gradually following the peak of the T cell response. We demonstrate, therefore, that following infection with LCMV there is expansion of both class-I-restricted and class-II-restricted virus-specific T cells; however, the degree of expansion of class-II-restricted T cells is substantially less than that observed for class-I-restricted cells. Furthermore, the downregulation phase of the class-II-restricted response is protracted compared with the precipitous contraction of the antiviral CD8(+) T cell response.

Virus-specific, CD8+ major histocompatibility complex class I-restricted cytotoxic T lymphocytes in lymphocytic choriomeningitis virus-infected beta2-microglobulin-deficient mice.

Following infection with lymphocytic choriomeningitis virus (LCMV), normal adult mice generate virus-specific, major histocompatibility complex (MHC) class I-restricted cytotoxic T lymphocytes (CTL) which clear the virus after intraperitoneal infection or cause death following intracranial (i.c.) infection. We have investigated the response of beta2-microglobulin-deficient (beta2m-) mice of the H-2d haplotype (KOD mice) to LCMV infection. Unlike H-2b beta2m- mice, which generate CD4+ MHC class II-restricted CTL in response to LCMV, KOD mice generate high levels of CD8+ MHC class I-restricted, virus-specific CTL. These CTL are specific for the LCMV nucleoprotein epitope (residues 118 to 126) in association with the Ld class I molecule, analogous to the CTL response in wild-type mice. KOD mice are also susceptible to lethal LCM disease, with 75 to 80% of the mice dying 7 to 9 days following i.c. infection with virus. Similar to results with normal mice, lethal LCM disease in KOD mice is prevented by in vivo depletion of CD8+ T cells prior to i.c. infection. In contrast to wild-type mice, however, KOD mice cannot control LCMV and become persistently infected. Overall, these results demonstrate that beta2m is not an absolute requirement for presentation of endogenous antigen on Ld or for induction of virus-specific Ld-restricted CTL in vivo.

Fas-dependent CD4+ cytotoxic T-cell-mediated pathogenesis during virus infection.

beta 2-Microglobulin-deficient (beta 2m-) mice generate a CD4+ major histocompatibility complex class II-restricted cytotoxic T-lymphocyte (CTL) response following infection with lymphocytic choriomeningitis (LCM) virus (LCMV). We have determined the cytotoxic mechanism used by these CD4+ CTLs and have examined the role of this cytotoxic activity in pathogenesis of LCM disease in beta 2m- mice. Lysis of LCMV-infected target cells by CTLs from beta 2m- mice is inhibited by addition of soluble Fas-Ig fusion proteins or by pretreatment of the CTLs with the protein synthesis inhibitor emetine. In addition, LCMV-infected cell lines that are resistant to anti-Fas-induced apoptosis are refractory to lysis by these virus-specific CD4+ CTLs. These data indicate that LCMV-specific CD4+ CTLs from beta 2m- mice use a Fas-dependent lytic mechanism. Intracranial (i.c.) infection of beta 2m- mice with LCMV results in loss of body weight. Fas-deficient beta 2m- Jpr mice develop a similar wasting disease following i.c. infection. This suggests that Fas-dependent cytotoxicity is not required for LCMV-induced weight loss. A potential mediator of this chronic wasting disease is tumor necrosis factor (TNF)-alpha, which is produced by LCMV-specific CD4+ CTLs. In contrast to LCMV-induced weight loss, lethal LCM disease in beta 2m- mice is dependent on Fas-mediated cytotoxicity. Transfer of immune splenocytes from LCMV-infected beta 2m- mice into irradiated infected beta 2m- mice results in death of recipient animals. In contrast, transfer of these splenocytes into irradiated infected beta 2m- Jpr mice does not cause death. Thus a role for CD4+ T-cell-mediated cytotoxicity in virus-induced immunopathology has now been demonstrated.

A point mutation in HLA-A*0201 results in failure to bind the TAP complex and to present virus-derived peptides to CTL.

Mutating the HLA-A*0201 heavy chain from threonine to lysine at position 134 (T134K) results in a molecule that presents exogenous peptide, but cannot present endogenously derived antigen. This is reflected in diminished cell surface expression and altered intracellular trafficking of T134K. The failure of T134K to present endogenous antigen can be overcome by using an ER targeting sequence, suggesting that the antigen presentation defect is restricted to TAP-dependent peptide loading. The ability of T134K to load peptide in a TAP-dependent manner is dramatically reduced compared with HLA-A*0201. By coimmunoprecipitation there is no detectable association of the T134K molecule with the TAP complex. Thus, T134K selectively affects TAP association and peptide loading, suggesting a requirement for the direct interaction of MHC class I heavy chain and the TAP complex for efficient presentation of endogenous antigen.

Natural killer cell activity in lymphocytic choriomeningitis virus-infected beta 2-microglobulin-deficient mice.

We have investigated the induction and role of natural killer (NK) activity in lymphocytic choriomeningitis virus (LCMV)-infected beta 2-microglobulin-deficient (beta 2m-) mice. We demonstrate that LCMV infection is more effective than polyinosinic:polycytidylic acid (poly I:C) at stimulating NK activity in beta 2m- mice. In addition, beta 2m- NK cells respond poorly to in vitro treatment with IL-12. The target specificity of the virally induced NK cells is similar to that previously reported for chemically induced beta 2m- NK cells. In both cases they can lyse YAC-1 tumor cells but are unable to kill beta 2m- or beta 2m+ T cell blasts. We have also found that the time course of induction of NK and cytotoxic T lymphocyte (CTL) activity by LCMV in beta 2m- mice is delayed compared with normal mice. Maximal NK and CTL activity is attained at day 8 and 10 post-infection respectively in beta 2m- mice compared with day 4 and 6-8 in B6 mice. Whereas normal mice die approximately 7 days following intracranial infection with LCMV, the course of disease in beta 2m- mice is protracted and characterized by a marked loss of body weight. We show that although the CD4+ CTL response in these mice is intimately involved in mediating weight loss, the virus-induced NK cells do not appear to play a role in the disease.

Genetic evidence for difference between intracellular and extracellular peptides in influenza A matrix peptide-specific CTL recognition.

During the course of extensive mutagenesis of HLA-A2.1, we examined influenza A matrix peptide (FMP)-specific CTL recognition of HMy2.C1R (C1R) cells expressing mutant HLA-A2.1 molecules, sensitized with synthetic peptide, FMP 58-66, (exogenous peptide), or infected with influenza A virus (endogenous peptide). Most mutants showed equivalent presentation of exogenous and endogenous peptides to FMP-specific CTL. However, five of the mutants differed in this property. Two of the five mutants, F9L and T134K, present exogenous peptide to FMP-specific CTL, but fail to present endogenous peptide to CTL. Western blot analysis using anti-matrix protein Ab indicates that the matrix protein is expressed in these mutants after infection with virus. Interestingly, transfection of these two mutants with a minigene encoding FMP 58-66 results in efficient lysis by FMP-specific CTL. Peptide-binding assays demonstrate that the two mutations dramatically decrease the binding of FMP. However, these mutants bind FMP as well as wild type in the presence of exogenously added human beta 2-m, suggesting that the lower affinity for beta 2-m leads to the inability to present endogenous peptide. The remaining three mutants, Y27N, Q32K, and S132C, fail to present exogenous peptide, but present endogenous peptide to FMP-specific CTL. Pulse-chase analyses followed by endoglycosidase-H treatment show that the rate of maturation and processing of the five mutant HLA-A2 molecules in C1R cells is identical to that of wild type. Overall, this study suggests that the assembly and subsequent recognition of endogenous peptide differs from that of exogenous peptide.

Transfer of lymphocytic choriomeningitis disease in beta 2-microglobulin-deficient mice by CD4+ T cells.

In this study we have investigated the role of CD4+, MHC class II-restricted cytotoxic T lymphocytes (CTLs) in the disease caused by lymphocytic choriomeningitis virus (LCMV) in beta 2-microglobulin deficient (beta 2m-) mice. Intracranial (i.c.) infection with LCMV resulted in death of six out of 11 beta 2m- mice. Mice that survived showed a marked loss in body weight. Death and loss of body weight could be prevented by immunosuppressing the mice with irradiation or cyclosporine prior to i.c. injection of LCMV. This treatment also prevented induction of virus-specific, MHC class II-restricted CTL following peripheral inoculation with LCMV. In vivo depletion of CD4+ cells with antibody also prevented death following i.c. injection whereas in vivo depletion of CD8+ cells had no effect. Disease could be transferred to recipient beta 2m- mice by adoptive transfer of beta 2m- derived immune spleen cells. Transfer of non-immune spleen cells did not result in illness. In vitro treatment of immune spleen cells with anti-CD4 antibody and complement eliminated class II-restricted CTL activity and also prevented mortality of recipients after adoptive transfer. Treatment with anti-CD8 antibody had no effect. We were unable to transfer LCM disease to beta 2m- recipients by adoptive transfer of immune spleen cells from C57BL/6 mice. These results suggest that, unlike normal mice, the pathology of LCM disease in beta 2m- mice is dependent upon virus-specific, CD4+CD8-, MHC class II-restricted T cells.

Interleukin-8-stimulated polyphosphoinositide hydrolysis in human peripheral blood lymphocytes.

We have attempted to provide evidence for the production of inositol phosphate (IP) metabolites as an indication of specific receptor-mediated signal transduction in human peripheral blood lymphocytes (PBL) in response to interleukin-8 (IL-8). IP metabolites were measured, after loading of PBL with [3H]-D-myo-inositol, by anion exchange high-performance liquid chromatography (HPLC) and liquid scintillation counting of collected fractions. In addition, inositol-1,4,5-trisphosphate (IP3), in extracts from unlabeled cells, was measured using a specific radioligand binding assay. Compared with phytohemagglutinin (PHA), which stimulated an increase in IP metabolites and, specifically, IP3 by greater than threefold, human recombinant (hr) IL-8 (1 nmol/L) also stimulated an increase in IP metabolites, as measured by HPLC, and a greater than threefold increase in IP3. The increase in IP3 was observed as early as 15 seconds after stimulation with hrIL-8, reaching maximal levels by 30 seconds. To further assess the signal transduction mechanism involved, the protein tyrosine kinase inhibitor genistein was added to the cells 10 minutes before stimulation with hrIL-8. After preincubation of PBL with this inhibitor, the generation of IP3 in response to PHA (5 micrograms/mL) and hrIL-8 (1 nmol/L) was inhibited by 42% and 51% of control values, respectively. In contrast to the production of IP metabolites, there were only small increases in intracellular calcium in response to hrIL-8 when compared with PHA.

In-vivo studies of the action spectrum and time course for release of transforming growth factor-alpha by ultraviolet irradiation in man.

Transforming growth factor-alpha (TGF-alpha) is a growth-promoting cytokine which enhances epithelial proliferation and is secreted by a wide variety of tumour cells. It is also present in normal human epidermis and its overproduction may be responsible for epidermal hyperproliferation in psoriasis. Ultraviolet (UV) B irradiation of human skin leads to epidermal damage and significant subsequent hyperplasia after approximately 24 h, whereas UVA irradiation has little such effect and predominantly damages the dermis. The relative efficacies of UVB and UVA in releasing TGF-alpha were studied in 10 subjects of skin types I and II using a skin-chamber technique and a specific TGF-alpha radioimmunoassay. Significantly elevated concentrations of immunoreactive TGF-alpha were detected in samples after 24 h in UVB-irradiated compared with unirradiated skin. Samples at earlier time points from UVB- and UVA-exposed skin contained measurable levels of TGF-alpha but these were not significantly elevated above the levels found in samples from unirradiated areas. These results, which suggest the UVB irradiation increases release of TGF-alpha from human skin at 24 h, indicate that TGF-alpha may be implicated in UVB-induced epidermal hyperplasia.

Inhibitory effect of cyclosporin A on erythroid and stromal colonies.

Cyclosporin A is used to prevent graft-versus-host disease (GvHD) following bone marrow transplantation (BMT) and it has been implicated in reducing the time to engraftment for leukaemia and aplastic anaemia patients. To evaluate the effect of cyclosporin A on engraftment, the proliferative capacity of bone marrow progenitors (CFU-E, CFU-F and CFU-C) was assessed both in vitro and following treatment with cyclosporin A over a 9-week period using an animal model. Cyclosporin had a differential effect on the haemopoietic progenitors, with the myeloid series unaffected at therapeutic concentrations. Both erythroid and stromal progenitors were significantly inhibited at similar concentrations. The mechanism by which cyclosporin A enhances engraftment remains unclear; however, it is not mediated by enhancing any of the haemopoietic progenitors.

Effect of cyclosporin on immune complex deposition in murine glomerulonephritis.

Chronic glomerulonephritis (GN) was induced in N/M mice by daily injections of human serum albumin (HSA). The glomerular lesion was similar to that observed in human membranous GN and was characterized by intense mesangial and capillary loop immunofluorescent staining for HSA, IgG and C3. Electron microscopic examination revealed numerous electron-dense deposits in the mesangium and along the subepithelial side of the glomerular basement membrane, the latter deposits being associated with membranous spikes. Chronically injected mice that had been treated with cyclosporin (CsA) from Day 1 had different patterns of immune complex deposition. Mesangial deposition was apparently unaltered but no subepithelial deposits or spikes were evident. In addition, only two out of 21 HSA-injected mice which began CsA treatment on Day 21 had subepithelial deposits. There was no significant difference in serum levels of HSA-specific IgG between the three groups of mice. CsA treatment would therefore appear to ameliorate the immunopathology of antigen-induced glomerulonephritis in this model without affecting serum antibody levels, and may be of therapeutic value in the treatment of human membranous GN.

New cytokines and receptors make their debut in San Antonio.

Two exciting developments were reported at the recent Seventh International Lymphokine Workshop. First, a number of recently cloned cytokines and cytokine receptors were described, proving that there is still a great deal to be learned about the most fundamental aspects of cell-cell communication. Second, advances were reported in the understanding of post-receptor signalling at both cytoplasmic and nuclear levels.