Biomedical subjects

I A Ramshaw

Publications and source records attributed to I A Ramshaw.

At least 19 recordsLinked to original sources

PubMed1999

IFN-gamma is critical to the control of murine autoimmune encephalomyelitis and regulates both in the periphery and in the target tissue: a possible role for nitric oxide.

NO and IFN-gamma have normally been considered cytotoxic and proinflammatory molecules, respectively, in the setting of the central nervous system inflammatory disease autoimmune encephalomyelitis (EAE). Using mice lacking the ligand binding chain of the IFN-gamma receptor (IFNgammaR-/-), we have previously shown that IFN-gamma is not essential for myelin oligodendrocyte glycoprotein peptide (MOG35-55) induced EAE expression but is in fact essential for its down-regulation. Here we examined the downstream molecular and cellular mechanism(s) of IFN-gamma regulation and demonstrate that neither IL-4 nor IL-10 appear to play a role in down-regulation nor do various lymphoid cell populations. Cells of the macrophage lineage are key to down-regulation as evidenced by the fact that peritoneal exudate cells from IFNgammaR+/+ mice inhibit Ag-driven proliferation of IFNgammaR-/- lymphocytes, whereas IFNgammaR-/- peritoneal exudate cells do not. High levels of reactive nitrogen intermediates are detected in the former cultures but not the latter, and the inhibition of proliferation is reversible with an inhibitor of inducible NO synthase, indicating a key role for NO in down-regulation. Studies with bone marrow chimeras indicate that down-regulation occurs not only systemically but also within the target tissue. These data suggest that IFN-gamma down-regulates EAE by inducing inducible NO synthase and subsequently NO production, both by macrophages in the periphery and, by inference, microglia and astrocytes in the target tissue.

Amino Acid Sequence↗

PubMed1999

Genetic vaccination strategies for enhanced cellular, humoral and mucosal immunity.

In this article, we describe several novel genetic vaccination strategies designed to facilitate the development of different types of immune responses. These include: i) the consecutive use of DNA and fowlpoxvirus vectors in "prime-boost" strategies which induce greatly enhanced and sustained levels of both cell-mediated immunity and humoral immunity, including mucosal responses; ii) the co-expression of genes encoding cytokines and cell-surface receptors, and the use of immunogenic carrier molecules, for immune modulation and/or improved targeting of vector-expressed vaccine antigens; and iii) the expression of minimal immunogenic amino acid sequences, particularly cytotoxic CD8+ T-cell determinants, in "polytope" vector vaccines. The capacity to modulate and enhance specific immune responses by the use of approaches such as these may underpin the development of vaccines against diseases for which no effective strategies are currently available.

Animals↗

PubMed1999

Immunogenicity of a human immunodeficiency virus (HIV) polytope vaccine containing multiple HLA A2 HIV CD8(+) cytotoxic T-cell epitopes.

Compelling evidence now suggests that alphabeta CD8 cytotoxic T lymphocytes (CTL) have an important role in preventing human immunodeficiency virus (HIV) infection and/or slowing progression to AIDS. Here, we describe an HIV type 1 CTL polyepitope, or polytope, vaccine comprising seven contiguous minimal HLA A2-restricted CD8 CTL epitopes conjoined in a single artificial construct. Epitope-specific CTL lines derived from HIV-infected individuals were able to recognize every epitope within the construct, and HLA A2-transgenic mice immunized with a recombinant virus vaccine coding for the HIV polytope also generated CTL specific for different epitopes. Each epitope in the polytope construct was therefore processed and presented, illustrating the feasibility of the polytope approach for HIV vaccine design. By simultaneously inducing CTL specific for different epitopes, an HIV polytope vaccine might generate activity against multiple challenge isolates and/or preempt the formation of CTL escape mutants.

AIDS Vaccines↗

PubMed1998

Loss of antiviral cytotoxic T-lymphocyte activity during high-level antigen stimulation.

High levels of antigenic stimulation can result in deactivation of CD8+ T cells through a variety of mechanisms, including insufficient T-cell help. In the present study, an adoptive transfer system was established in which ovalbumin (OVA)-specific CD8+ T cells were transferred to irradiated mice infected with a recombinant vaccinia virus encoding OVA (VV-OVA). Prolonged activation of OVA-specific CD8+ T cells resulted in a proliferative block in these cells, although cytotoxic function was maintained. Unlike naive and recently activated OVA-specific T cells, these nonproliferative cytotoxic CD8+ T cells did not have antiviral activity following further transfer to mice infected with VV-OVA. Provision of interleukin-2 (IL-2) at the site of virus infection using a recombinant virus encoding antigen and IL-2, as well as the addition of helper T cells, had no effect on the generation of these dysfunctional T cells. Thus, there was no evidence that lack of T-cell help was responsible for CD8+ T-cell deactivation in this model.

Animals↗

PubMed1998

Infertility in mice induced by a recombinant ectromelia virus expressing mouse zona pellucida glycoprotein 3.

Population control has become a major problem in many wildlife species. Fertility control through immunocontraception has been proposed as a method for reducing population size. We have tested the concept that immunocontraception can be achieved with a recombinant ectromelia virus expressing an ovary-specific antigen, the mouse zona pellucida 3 (ZP3) glycoprotein. Female mice infected with the recombinant virus produced autoimmune antibodies against ZP3 and were infertile for 5-9 mo after infection. For almost half the infertile mice, immunity to ZP3 was associated with a disruption of ovarian follicular development and the depletion of mature follicles without observable oophoritis. Mice returned to fertility as the anti-ZP3 antibody level in the serum decreased. Reinfection of the mice with the recombinant virus boosted the anti-ZP3 response and restored infertility.

Animals↗

PubMed1998

Enhanced T-cell immunogenicity and protective efficacy of a human immunodeficiency virus type 1 vaccine regimen consisting of consecutive priming with DNA and boosting with recombinant fowlpox virus.

The induction of human immunodeficiency virus (HIV)-specific T-cell responses is widely seen as critical to the development of effective immunity to HIV type 1 (HIV-1). Plasmid DNA and recombinant fowlpox virus (rFPV) vaccines are among the most promising safe HIV-1 vaccine candidates. However, the immunity induced by either vaccine alone may be insufficient to provide durable protection against HIV-1 infection. We evaluated a consecutive immunization strategy involving priming with DNA and boosting with rFPV vaccines encoding common HIV-1 antigens. In mice, this approach induced greater HIV-1-specific immunity than either vector alone and protected mice from challenge with a recombinant vaccinia virus expressing HIV-1 antigens. In macaques, a dramatic boosting effect on DNA vaccine-primed HIV-1-specific helper and cytotoxic T-lymphocyte responses, but a decline in HIV-1 antibody titers, was observed following rFPV immunization. The vaccine regimen protected macaques from an intravenous HIV-1 challenge, with the resistance most likely mediated by T-cell responses. These studies suggest a safe strategy for the enhanced generation of T-cell-mediated protective immunity to HIV-1.

AIDS Vaccines↗

PubMed1997

Recombinant viruses as vaccines and immunological tools.

Recombinant viruses have been investigated as candidate vaccines, and have also been used extensively as immunological tools. Recent advances in this area include the following: the construction and testing of a recombinant simian immunodeficiency virus encoding human interferon-gamma; the development of new vectors such as recombinant poliovirus; and the generation of polyepitope vaccines. Basic immunological research has benefited from the use of recombinant viruses to further understand the role of molecules such as CD40 ligand, nitric oxide and interleukin-4.

AIDS Vaccines↗

PubMed1997

DNA immunization.

DNA immunization has recently emerged as a highly promising approach for the prevention and therapy of a wide range of infectious and non-infectious diseases. Here, we review the rapid development of this field and recent advances in our understanding of some of the mechanisms by which DNA vaccines stimulate the immune system.

Animals↗

PubMed1997

DNA vaccination against virus infection and enhancement of antiviral immunity following consecutive immunization with DNA and viral vectors.

Recent demonstrations of the immunogenicity of antigens encoded in DNA plasmids following delivery by various routes have heralded a new era in vaccine development. In this article, we review progress in DNA-based antiviral immunoprophylaxis. Preclinical studies have already established the immunogenicity of DNA plasmids encoding protective antigens from a wide variety of viral pathogens and work published in recent months has raised real prospects of broadly protective DNA vaccination against infections with influenza virus and HIV. We also describe a consecutive immunization protocol consisting of a priming dose of vaccine antigen encoded in DNA plasmids followed by a booster with the same antigen encoded in recombinant fowlpox virus vectors. We have used this strategy to generate protective antiviral cell-mediated immunity and sustained, high-level antibody responses both systemically and at mucosae, and to elucidate immunological mechanisms underlying the development of immunity to antigens delivered in DNA vectors.

Animals↗

PubMed1997

DNA vaccines for the treatment of autoimmune disease.

DNA vaccines represent one of the most significant developments in vaccine technology in recent years. Although, in general, studies have primarily focused on the induction of protective immune responses against infectious pathogens, the technology may prove useful for other immune-related diseases, including autoimmunity. Autoimmune disease results from a breakdown in tolerance to self antigens; however, the same fundamental immunological reactions that control immune responses to foreign antigens are also likely to operate during the course of autoimmune disease. These include the reciprocal regulation of Th cell subsets. Th1 cells appear to be involved in many organ-specific autoimmune diseases while suppression of disease is associated with cells of the Th2 phenotype. It has been possible, therefore, to suppress many of the pathological consequences of autoimmunity by manipulating the Th1/Th2 cell balance. The induction of Th2 responses by DNA immunization might therefore be expected to have a profound effect on the course of autoimmune disease. Indeed, we have demonstrated that DNA immunization can protect animals against the autoimmune central nervous system inflammatory disease, experimental autoimmune encephalomyelitis (EAE). As many other autoantigens have now been identified, the application of this technology to other autoimmune diseases warrants investigation.

Animals↗

PubMed1997

Cytokine enhancement of immune responses important for immunocontraception.

To be effective, an immunocontraceptive vaccine should elicit strong, sustained antibody responses. Circulating antibodies may block the function of hormones and target some gamete antigens, but the most effective inhibition of fertilization will probably be achieved by antibodies in the reproductive tract. It may also be beneficial to administer vaccine antigens with strong adjuvants, such as cytokines, in order to achieve high specific antibody titres. In this review recent findings concerning the role of cytokines in the regulation of antibody responses, particularly at mucosae, are described and prospects for immunization for immune responses which may be important for fertility control are discussed. On the basis of these findings, a model system for the delivery of vaccine antigens to the immune system in vaccinia, fowlpox or DNA plasmid vectors along with type-2 cytokines, such as interleukin-4 (IL-4), IL-5 and IL-6, as B cell adjuvants is presented. Studies such as these in the areas of antigen delivery and enhancement of immune responses are aimed at providing new options for fertility control, particularly via oral vaccination.

Animals↗

PubMed1997

Interleukin-7 enhances cell-mediated immune responses in vivo in an interleukin-2-dependent manner.

We have engineered recombinant vaccinia virus vectors expressing murine interleukin-7 (IL-7) in order to study the activity of this factor during virus infection. Virus-encoded IL-7 dramatically increased splenic cellularity in infected mice and enhanced the proliferative activity of T cells and their capacity to secrete IL-2 and IL-6, but not IFN-gamma, TNF-alpha or IL-4. Numbers of splenic CD4+ and CD8+ T lymphocytes were elevated two- to threefold. IL-7 also mediated a marked enhancement of both antigen-specific and nonspecific cellular immune activity. Total splenic antiviral cytotoxic T cells (CTL), natural killer (NK), and lymphokine-activated killer cells (LAK) responses were augmented significantly in mice given VV-HA-IL-7 compared with those given control virus, with accelerated clearance of the former. The enhanced antiviral cellular immune activity mediated by IL-7 was critically dependent on IL-2 produced by the host, but occurred independently of IFN-gamma. The ability of IL-7 to induce cellular immune responses in vivo may have applications in antiviral immunotherapy, particularly in cases of immunodeficiency.

Animals↗

PubMed1997

Cytokines and immunity to viral infections.

In this review, we discuss two broad approaches we have taken to study the role of cytokines and chemokines in antiviral immunity. Firstly, recombinant vaccinia viruses were engineered to express genes encoding cytokines and chemokines of interest. Potent antiviral activity was mediated by many of these encoded factors, including IL-2, IL-12, IFN-gamma, TNF-alpha, CD40L, Mig and Crg-2. In some cases, host defense mechanisms were induced (IL-2, IL-12, Mig and Crg-2), whilst for others, a direct antiviral effect was demonstrated (IFN-gamma, TNF-alpha and CD40L). In sharp contrast, vector-directed expression of IL-4, a type 2 factor, greatly increased virus virulence, due to a downregulation of host type 1 immune responses. Our second experimental approach involved the use of strains of mice deficient for the production of particular cytokines or their receptors, often in combination with our engineered viruses. Mice deficient in either IFN-gamma, IFN-gamma R, IFN-alpha/beta R, TNFRs, CD40 or IL-6 were, in general, highly susceptible to poxvirus infection. Surprisingly, not only the TNFR1, but also the TNFR2, was able to mediate the antiviral effects of TNF-alpha in vivo, whilst the antiviral activity observed following CD40-CD40L interaction is a newly defined function which may involve apoptosis of infected cells. Through the use of perforin-deficient mice, we were able to demonstrate a requirement for this molecule in the clearance of some viruses, such as ectromelia virus, whilst for others, such as vaccinia virus, perforin was less important but IFN-gamma was essential.

Animals↗

PubMed1996

IFN-gamma plays a critical down-regulatory role in the induction and effector phase of myelin oligodendrocyte glycoprotein-induced autoimmune encephalomyelitis.

129/Sv mice are resistant to induction of experimental autoimmune encephalomyelitis (EAE) induced with myelin oligodendrocyte glycoprotein peptide (MOG35-55). Mice of this strain lacking the gene coding for the ligand-binding chain of the IFN-gamma receptor develop EAE with high morbidity and mortality. Spleen cells from sensitized IFN-gammaR-/- mice proliferated extensively when stimulated with MOG peptide in culture and produced high levels of IFN-gamma and TNF but no detectable IL-4. Transfer of spleen cells from sensitized IFN-gammaR-/- mice produced EAE in both IFN-gammaR+/+ and IFN-gammaR-/- recipients. Disease was severe in IFN-gammaR-/- recipients and mortality high (77%). Surviving mice remained moribund until termination of the experiments. IFN-gammaR+/+ recipients developed disease of equal severity, but with no mortality, and recovered significantly. These results indicate that IFN-gamma is not essential for the generation or function of anti-MOG35-55 effector cells but does play an important role in down-regulating EAE at both the effector and induction phase of disease.

Amino Acid Sequence↗

PubMed1996

Nitric oxide production is increased during murine vaccinia virus infection, but may not be essential for virus clearance.

Recent reports have highlighted a potential antiviral activity for nitric oxide (NO). The purpose of this study was to investigate the production of NO in mice during vaccinia virus (VV) or herpes simplex virus type 1 infection, and to assess the role of NO in clearance of VV. Reactive nitrogen intermediates (RNI; NO and its stable oxidation products, nitrite and nitrate) were significantly elevated in the plasma of mice infected with these viruses. Furthermore, spleen cells from virus-infected mice produced elevated RNI levels following stimulation in vitro with LPS. NO production during VV infection was critically dependent on the cytokines tumor necrosis factor and interferon-gamma, and on the presence of both CD4+ and CD8+ T lymphocytes. Treatment of VV-infected mice with the nitric oxide synthase inhibitor N(G)-methyl-L-arginine did not alter the course of infection, suggesting that NO may not be essential for the clearance of this virus.

Animals↗

PubMed1996

Interleukin-4 mediates down regulation of antiviral cytokine expression and cytotoxic T-lymphocyte responses and exacerbates vaccinia virus infection in vivo.

Interleukin-4 (IL-4) promotes the growth of Th2-type cells while down regulating the development of Th1-type cells. It has been suggested that the actions of this factor inhibit Th1-type effector activity in vivo and may underlie the development of diseases normally controlled by cell-mediated immune responses. Here, we show that clearance of recombinant vaccinia viruses (VV) engineered to express the gene for murine IL-4 is markedly delayed in mice compared with control recombinant VV. While antiviral antibody levels and NK activity in mice given control virus or IL-4-expressing virus were similar, antiviral cytotoxic T-lymphocyte responses were profoundly suppressed throughout the course of infection with the latter. Limiting dilution analysis of IL-4-virus-infected spleens revealed a marked reduction in numbers of cytotoxic T-lymphocyte precursors. Furthermore, reverse transcriptase PCR analysis of splenic mRNA prepared from mice infected with the IL-4-expressing VV showed a marked down regulation of IL-12, gamma interferon, and IL-2 gene expression compared with that from mice given control virus. IL-4 also inhibited the production of nitric oxide (NO), a potent mediator of antimicrobial activity. Together, these data show that IL-4 markedly suppresses the development of antiviral cell-mediated immune responses in vivo with deleterious effects on virus clearance.

Animals↗

PubMed1996

A recombinant vaccinia virus encoding inducible nitric oxide synthase is attenuated in vivo.

To investigate the role of nitric oxide during vaccinia virus (VV) infection of mice, a recombinant VV encoding the inducible nitric oxide synthase (iNOS) gene (VV-HA-iNOS) was constructed. Following infection of immunocompromised or immunocompetent mice, the virus was highly attenuated compared with a control recombinant VV. Athymic and sublethally irradiated mice survived infection with 10(7) PFU of VV-HA-iNOS, a dose that resulted in uniform mortality in mice infected with the control recombinant VV. Attenuated virus growth was evident as early as 24 h following infection, suggesting that NO had direct antiviral activity. We have previously shown that treatment of mice with the inhibitor of NO production N(G)-methyl-L-arginine did not influence the course of VV infection in mice. The present study has indicated that NO can potentially exert an antiviral effect during murine VV infection. We propose that during VV infection, nitric oxide production contributes to the control of virus growth, but that in its absence, other antiviral mechanisms are sufficient to mediate fully effective virus clearance.

Animals↗

PubMed1995

The role for host-immune factors in the in vivo antiviral effects of tumour necrosis factor.

This report examines the host-immune response to vaccinia virus in mice exposed to tumour necrosis factor (TNF). Exposure to TNF was done via two approaches; (1) mice were treated with TNF in complex with a specific anti-TNF antibody (Ab 301) which enhances the antiviral efficacy of this cytokine, prior to vaccinia virus (VV) infection; and (2) mice were infected with a recombinant VV which encodes the murine TNF gene (VV-HA-TNF). The antiviral effect induced by TNF plus Ab 301 in CBA/H mice was not sensitive to sub-lethal gamma irradiation, indicating that a proliferative immune cell population was not responsible for the observed attenuated VV growth. This was further evidenced by NK cell and CTL studies which showed, when compared to controls, that TNF plus Ab 301 treated animals had decreased spleen NK cell and CTL activities. This suggests that a non-specific factor, effective earlier than day 2 postinfection, was responsible for the restriction of VV growth. To further investigate this possibility, mice were treated with either the TNF/Ab 301 regimen, or infected with VV-HA-TNF, and their peritoneal exudate cells (PEC) examined during early VV infection. Control recombinant VV infection resulted in an increase in neutrophil numbers, and TNF/Ab 301 treatment before infection did not increase this further. VV-HA-TNF infection of mice, however, induced a massive but transient increase in the number of neutrophils, suggesting that this cell population was important to the in vivo restriction of VV-HA-TNF growth.

Animals↗