Structure and conformation of helical nucleic acids: rebuilding program (SCHNArP).

We present a program, SCHNArP, for rebuilding double-helical nucleic acid structures from a set of helical parameters. The parameter sets are based on mathematically reversible schemes that allow direct comparison of data from experimental X-ray crystal structures analyzed using the analysis program, SCHNAaP (see accompanying paper), and structures built using the rebuilding program, SCHNArP. The program uses either local CEHS helical parameters or global helical parameters.

Structure and conformation of helical nucleic acids: analysis program (SCHNAaP).

We present a new versatile program, SCHNAaP, for the analysis of double-helical nucleic acid structures. The program uses mathematically rigorous and fully reversible procedures for calculating the structural parameters: the Cambridge University Engineering Department Helix computation Scheme (CEHS) is used to determine the local helical parameters and an analogous procedure is used to determine the global helical parameters. These parameters form a complete set that conforms to the "Cambridge Accord" on definitions and nomenclature of nucleic acid structure parameters.

Type I interferons enhance production of IFN-gamma by NK cells.

In murine models, challenge with different viral and parasitic infection is closely associated with the production of type I interferons (IFN-alpha/beta) and NK cell production of interferon-gamma (IFN-gamma). Therefore, we wished to determine if IFN-alpha/beta had a role in the regulation of NK cell production of IFN-gamma. IFN-alpha/beta alone stimulated low levels of IFN-gamma production by purified populations of IL-2 activated NK cells but in combination with IL-12 resulted in the production of significant levels of IFN-gamma.

The role of the polyamine inhibitor eflornithine in the neuropathogenesis of experimental murine African trypanosomiasis.

The treatment of late-stage human African trypanosomiasis is complicated by a post-treatment reactive encephalopathy, also referred to as a 'reactive arsenical encephalopathy', that may be fatal. This study used a well established experimental mouse system to assess the use of the trypanostatic drug, eflornithine, in the management of this post-treatment reaction. Female CD-1 mice infected with an eflornithine-resistant trypanosome stabilate and treated with the trypanocidal compound diminazene aceturate on or after day 21 post-infection develop a reactive encephalopathy and relapsing parasitaemia.

Construction of double-helical DNA structures based on dinucleotide building blocks.

We present a new method for building full 3-D structures of DNA sequences. A database of the conformational properties of dinucleotide steps has been compiled using X-ray crystal structures of oligonucleotides. The protocol uses these dinucleotides as building blocks to generate three dimensional structures of any required sequence in any required conformation.

Role of interleukin-10 in regulation of T-cell-dependent and T-cell-independent mechanisms of resistance to Toxoplasma gondii.

Interleukin-10 (IL-10) is a cytokine which can inhibit T-cell and natural killer (NK) cell functions associated with cell-mediated immunity to intracellular infections. The production of IL-10 by mice infected with Toxoplasma gondii has been implicated in the suppression of lymphocyte proliferation observed during acute toxoplasmosis, as well as susceptibility to infection with this parasite. We have used C57BL/6 mice which lack a functional IL-10 gene (IL-10(-/-) mice) to investigate the role of IL-10 in acute toxoplasmosis.

IL-10 is required to prevent immune hyperactivity during infection with Trypanosoma cruzi.

Previous studies have associated the production of IL-10 with suppression of the protective cell-mediated immune response to Trypanosoma cruzi. To further understand the role of IL-10 in the resistance to and pathogenesis of Chagas' disease, we infected C57BL/6 wild-type (IL-10 +/+) or C57BL/6 IL-10 knockout (IL-10 -/-) mice with the virulent Tulahuen strain of T. cruzi.

The role of the CD28/B7 interaction in the regulation of NK cell responses during infection with Toxoplasma gondii.

We examined the role of the CD28/B7 interaction in regulation of NK cell activity. Cells transfected with B7 enhanced IL-12-induced production of IFN-gamma by IL-2-activated, CD28+ NK cells, but not by resting CD28- NK cells. The ability of B7 transfectants to enhance NK cell production of IFN-gamma was dependent on the intracellular adhesion molecule-1/LFA-1 interaction and could be inhibited by TGF-beta, but not IL-10.

DNA base-stacking interactions: a comparison of theoretical calculations with oligonucleotide X-ray crystal structures.

Experimental data on the conformational properties of dinucleotides taken from high-resolution X-ray crystal structures of oligonucleotides have been compared with theoretical energy calculations on the base-stacking interactions. The conformational properties of the dinucleotides determined by calculation agree well with the experimental data, which shows that the method used for computing the stacking interactions is reliable. In addition, the calculations provide insight into the origins of the major trends that are observed in the experimental data.

Treatment with interleukin 12 in combination with atovaquone or clindamycin significantly increases survival of mice with acute toxoplasmosis.

The capacity of interleukin 12 (IL-12) to potentiate drugs in the treatment of murine toxoplasmosis was examined. IL-12 (100 ng/injection), atovaquone (10 mg/kg of body weight/day), or clindamycin (5 mg/kg/day) administered alone caused delayed time to death or minimal survival rates. In contrast, significant survival rates resulted when the same dose of IL-12 was used in combination the same doses of atovaquone (P=0.

Interleukin-12-mediated resistance to Trypanosoma cruzi is dependent on tumor necrosis factor alpha and gamma interferon.

The aim of this study was to determine if interleukin-12 (IL-12) has a role in the immune response to Trypanosoma cruzi. Infection of BALB/c mice with the virulent Tulahuen strain of T. cruzi is characterized by a high-level parasitemia, pathology in the heart associated with the presence of amastigotes, and death during the acute phase of the disease.

Sequence-dependent DNA structure.

The three-dimensional structure of DNA depends subtly on its sequence, and this property is used by the proteins that regulate gene expression to locate their target sequences. Despite the large body of experimental data that has been accumulated on the relationship between sequence and DNA structure, we still do not fully understand the molecular basis for these properties, nor can we predict a three-dimensional structure from a given sequence. We have been using computer modelling to tackle these problems.

IL-1 beta is required for IL-12 to induce production of IFN-gamma by NK cells. A role for IL-1 beta in the T cell-independent mechanism of resistance against intracellular pathogens.

Mice with the severe combined immunodeficiency (SCID) possess an IFN-gamma-dependent mechanism of resistance to the intracellular pathogens Toxoplasma gondii and Listeria monocytogenes that is dependent on IL-12-induced production of IFN-gamma by NK cells. In this report we demonstrate that IL-1 beta is required for IL-12 to stimulate production of IFN-gamma by NK cells, and that IL-1 is important in IL-12-mediated resistance to T. gondii in vivo.

Preferential activation and expansion of human peripheral blood gamma delta T cells in response to Toxoplasma gondii in vitro and their cytokine production and cytotoxic activity against T. gondii-infected cells.

Studies were conducted to determine if gamma delta T cells participate in the immune response to Toxoplasma gondii. Preferential expansion of human gamma delta T cells occurred when peripheral blood T cells from either T. gondii-seronegative or seropositive individuals were incubated with autologous PBMC infected with the parasite.

Definitive identification of a gene that confers resistance against Toxoplasma cyst burden and encephalitis.

Control of resistance to cyst burden following per-oral infection with Toxoplasma gondii has been mapped previously to a region of mouse chromosome 17 of approximately 140 kb. This region is contiguous with and contains the class I gene, Ld. Resistance to development of toxoplasmic encephalitis has also been reported to be controlled by genes in this region of H-2.

Transforming growth factor-beta inhibits interleukin-12-induced production of interferon-gamma by natural killer cells: a role for transforming growth factor-beta in the regulation of T cell-independent resistance to Toxoplasma gondii.

Severe-combined immune deficient (SCID) mice have been found to resist infection with the intracellular protozoan parasite Toxoplasma gondii via interleukin (IL)-12 stimulation of interferon (IFN)-gamma production by natural killer (NK) cells. Previously, we demonstrated the presence of increased levels of transcripts for transforming growth factor-beta (TGF-beta) in the brains and lungs of SCID mice infected with T. gondii, leading us to investigate the role of TGF-beta in the mechanism of resistance to T.

Roles of gamma interferon and other cytokines in suppression of the spleen cell proliferative response to concanavalin A and toxoplasma antigen during acute toxoplasmosis.

Suppressed splenocyte proliferation in response to mitogen and toxoplasma lysate antigen (TLA) is observed in mice acutely infected with Toxoplasma gondii. Recently, we reported that NG-monomethyl-L-arginine (NMMA), an inhibitor of reactive nitrogen intermediate (RNI) production, partially restored proliferative responses of splenocytes from infected mice. In the present study we have examined the effect of NMMA on production of cytokines by splenocytes from mice acutely infected with T.

Studies on the role of interleukin-12 in acute murine toxoplasmosis.

Interleukin-12 (IL-12) is important in the regulation of resistance to Toxoplasma gondii in mice with severe combined immunodeficiency (SCID). The protective ability of IL-12 in SCID mice appears to be through its activity on natural killer (NK) cells to induce production of interferon-gamma (IFN-gamma). In this study we assessed the role of IL-12 in the acute stage of toxoplasmosis in immunocompetent mice.

Enhancement of intracellular replication of Toxoplasma gondii by IL-6. Interactions with IFN-gamma and TNF-alpha.

Toxoplasma gondii is a major pathogen of immunocompromised hosts, and one defense mechanism against the parasite is activation of macrophages (M phi) for toxoplasmacidal activity by IFN-gamma after triggering by TNF-alpha. IL-6, IFN-gamma, and TNF-alpha are cytokines involved in inflammatory responses and are induced by T. gondii infection.

Immunopathogenesis of toxoplasmic encephalitis.

The incidence of toxoplasmic encephalitis (TE) has increased with the increasing numbers of patients with immunodeficiencies, in whom reactivation of latent Toxoplasma infection may occur. This highlights the important role of the immune response in maintaining infection with Toxoplasma gondii in a latent form. Because the brain is the most commonly affected site of latent infection and because it is anatomically unique in regard to the immune system, understanding the systemic immune response to infection within the brain is important.

Immunocytochemical detection of cytokines in the lymph nodes and brains of mice resistant or susceptible to toxoplasmic encephalitis.

BALB/c mice develop toxoplasmic encephalitis (TE) but the pathology resolves; in contrast, CBA/Ca mice develop progressive TE. Immunohistochemical analysis revealed peak staining for interferon-gamma (IFN-gamma) and tumor necrosis factor (TNF) in lymph nodes of both strains on day 7 of infection, with elevated levels of IFN-gamma and TNF persisting in CBA/Ca mice. TNF was present in the central nervous systems (CNS) of both strains of mice and correlated with severity of pathology.