Moloney murine leukemia virus protease expressed in bacteria is enzymatically active

Replication of Moloney murine leukemia virus requires a readthrough translation mechanism to generate the Gag-Pol polyprotein. One of the final products of this polyprotein is the protease (PR), which is required to generate the mature virion proteins. The assembly of Gag and Gag-Pol polyprotein into a virion followed by activation of the viral protease is necessary to produce a mature, infectious particle. These events are believed to occur near the cell membrane just prior to the budding of the virion. We report here the autoproteolytic activity of the viral PR when a Gag-PR fusion protein is expressed in E. coli. Efficient cleavage at the p12/CA, CA/NC and NC/PR junctions was observed. Thus the Moloney murine leukemia virus PR is capable of cleaving its substrates in the absence of specific host factors.

Alterations of oncogenes, tumor suppressor genes and growth factors in hepatocellular carcinoma: with relation to tumor size and invasiveness

OBJECTIVE

To make a better understanding of the molecular mechanisms involved in recurrence and metastasis of the hepatocellular carcinoma (HCC), some invasion related oncogenes, and growth factors have been investigated.

METHODS

The studies were separately carried out, the results of which were summarized in this article with relation to tumor size and invasiveness of HCC.

RESULTS

The aberration rates of p53 and CDKN2 in HCC were 45.9% and 36.4% respectively, which were higher in invasive HCC compared with non-invasive HCC. H-ras expression was positive in 29.3% of HCC, which was associated with recurrence and extrahepatic metastasis of HCC. Intralesional injection of H-ras antisense gene markedly inhibited the tumor growth and metastasis of HCC in nude mice. The positive rates of transforming growth factor (TGF)-alpha, epidermal growth factor receptor (EGFR) and c-erbB-2 were 45.7%, 47.1% and 92.3% respectively. The expression of EGFR was closely related to TGF-alpha, which was related to HCC recurrence. But no obvious difference of TGF-alpha or c-erbB-2 expression was found between HCC with and without recurrence, or with and without extrahepatic metastasis. Expression of nm23/tissue inhibitor of metalloproteinase (TIMP)-2 was positively associated with the prognosis of HCC patients (Log-rank, P < 0.001). The alterative rates of above-mentioned genes and growth factors in small HCC were slightly lower than that in large ones, but no significant difference was shown except the p53 mutation.

CONCLUSIONS

The p53/CDKN2 mutation, over-expression of H-ras/EGFR, were associated with the invasiveness and recurrence of HCC. H-ras antisense gene might be of potential implication in the control of HCC recurrence and metastasis. Expression of nm23/TIMP-2 was closely related to the prognosis of HCC patients. Biological characteristics remained critical points to the prognosis even in small HCC.

Energetics of two-step binding of a chromophoric reaction product, trans-3-indoleacryloyl-CoA, to medium-chain acyl-coenzyme-A dehydrogenase

We previously demonstrated that the UV/visible spectrum of a chromophoric ligand, trans-3-indoleacryloyl-coenzyme-A (IACoA), is red-shifted (due to polarization of its carbonyl group) upon binding to pig kidney medium-chain acyl-CoA dehydrogenase (MCAD). The transient kinetic data revealed that the overall binding occurred in two steps. The first (fast) step involved the formation of an MCAD-IACoA collision complex in which the electronic structure of IACoA remained unchanged (the "colorless" complex), followed by a slow isomerization step with a concomitant red-shift in the IACoA spectrum (the "colored" complex) [Johnson, J. K., Wang, Z. X., and Srivastava, D. K. (1992) Biochemistry 31, 10564-10575]. To ascertain the energetics of the above two-step process, we investigated the temperature dependence of the spectral changes, binding constant of the MCAD-IACoA complex, and the rate constants for the conversion between the colorless and colored complexes. The data revealed that as the temperature of the incubation mixture of MCAD and IACoA ([IACoA] >> [MCAD] > Kd) increases from 12 to 35 degrees C, the resultant spectral peak of the MCAD-IACoA complex (lambda max = 417 nm) decreases. However, in this temperature range, the equilibrium constant for the second (isomerization) step remains unaffected. Isothermal titration calorimetric studies for the binding of IACoA to MCAD reveal that the overall binding energy at 25 degrees C (delta G degree = -7.4 kcal/mol) is contributed almost equally by the enthalpic (delta H degree = -3.7 kcal/mol) and entropic (T delta S degree = 3.7 kcal/mol) changes. As the temperature increases, both delta H degree and T delta S degree decrease proportionately, resulting in a strong enthalpy-entropy compensation effect. The temperature dependence of delta H degree yields a delta Cp degree value of -0.24 kcal/mol. The data presented herein throw light on the energetic consequences for the binding of IACoA to MCAD, the apparent similarity between the van't Hoff and calorimetric enthalpies, enthalpic and entropic contributions during the polarization of the carbonyl group of IACoA, and the overall structural-functional features of the enzyme-ligand complex as well as enzyme catalysis.

Efficient transfer of genes into murine cardiac grafts by Starburst polyamidoamine dendrimers

Starburst dendrimer, a structurally defined, spherical macromolecule composed of repeating polyamidoamino subunits, was investigated to augment plasmid-mediated gene transfer efficiency in a murine cardiac transplantation model. The grafts were directly injected with naked pCH110, a plasmid encoding beta-galactosidase (beta-Gal), or pCH110-dendrimer complex, and reporter gene expression determined by X-Gal staining. The grafts injected with pCH110-dendrimer demonstrated widespread and extended beta-Gal expression in both myocytes and the graft infiltrating cells from 7 to 28 days, compared to the grafts injected with naked pCH110 that expressed beta-Gal only in myocytes for less than 14 days. p alphaMHC-vIL-10, as plasmid encoding viral interleukin-10 (vIL-10) under the control of alpha-myosin heavy chain promoter, was able to prolong allograft survival from 13.9 +/- 0.9 days to 21.4 +/- 2.3 days (p < 0.005). When dendrimer G5EDA was used with p alphaMHC-vIL-10, 60-fold less DNA resulted in significant prolongation of graft survival to 38.6 +/- 4.7 days (p < 0.0005). The dose of DNA, the charge ratio of DNA to dendrimer, and the size generation of the dendrimers were all determined to be critical variables for prolongation of allograft survival in this model system. Thus, the use of the Starburst dendrimer dramatically increased the efficiency of plasmid-mediated gene transfer and expression. Production of immunosuppressive cytokines at higher amounts for longer periods of time in a greater expanse of tissue enhanced the immunosuppressive effect and prolonged graft survival further.

Promoter attenuation in gene therapy: interferon-gamma and tumor necrosis factor-alpha inhibit transgene expression

One of the major limitations to current gene therapy is the low-level and transient vector gene expression due to poorly defined mechanisms, possibly including promoter attenuation or extinction. Because the application of gene therapy vectors in vivo induces cytokine production through specific or nonspecific immune responses, we hypothesized that cytokine-mediated signals may alter vector gene expression. Our data indicate that the cytokines interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) inhibit transgene expression from certain widely used viral promoters/enhancers (cytomegalovirus, Rous sarcoma virus, simian virus 40, Moloney murine leukemia virus long terminal repeat) delivered by adenoviral, retroviral or plasmid vectors in vitro. A constitutive cellular promoter (beta-actin) is less sensitive to these cytokine effects. Inhibition is at the mRNA level and cytokines do not cause vector DNA degradation, inhibit total cellular protein synthesis, or kill infected/transfected cells. Administration of neutralizing anti-IFN-gamma monoclonal antibody results in enhanced transgene expression in vivo. Thus, standard gene therapy vectors in current use may be improved by altering cytokine-responsive regulatory elements. Determination of the mechanisms involved in cytokine-regulated vector gene expression may improve the understanding of the cellular disposition of vectors for gene transfer and gene therapy.

Purification and cloning of hepatocyte growth factor activator inhibitor type 2, a Kunitz-type serine protease inhibitor

Hepatocyte growth factor (HGF) activator is a serine protease responsible for proteolytic activation of HGF in response to tissue injury and thus plays an important role in the regulation of biological functions of HGF in regenerating tissue. We previously purified an inhibitor of HGF activator (HGF activator inhibitor type 1, HAI-1) from the conditioned medium of a human stomach carcinoma cell line MKN45 and cloned its cDNA. HAI-1 is a novel member of the Kunitz family of serine protease inhibitors. In the present study, we purified a second type of HGF activator inhibitor (HAI-2) from the conditioned medium of MKN45 cells and molecularly cloned its cDNA. The cDNA sequence revealed that HAI-2 is derived from a precursor protein of 252 amino acids and contains two Kunitz domains, indicating that HAI-2 is also a member of the Kunitz family of serine protease inhibitors. The primary translation product of HAI-2 has a hydrophobic sequence in the COOH-terminal region, suggesting that, like HAI-1, HAI-2 is produced in a membrane-associated form and secreted in a proteolytically truncated form. Because HAI-2 and HAI-1 are potent inhibitors specific for HGF activator, they may be involved in regulation of proteolytic activation of HGF in injured tissues.

Adenovirus-mediated gene transfer of viral interleukin-10 inhibits the immune response to both alloantigen and adenoviral antigen

Although adenoviral vectors are attractive for gene transfer, their effectiveness is limited by host antiviral immune responses. In this study, we determined if host antiallograft and antiviral immunity could be diminished with an adenoviral vector encoding the immunosuppressive cytokine viral interleukin-10 (vIL-10). AdSV40vIL-10, a vIL-10-expressing adenoviral vector with an SV40 promoter, induced significant prolongation of murine cardiac allograft survival to 32.2 +/- 1.7 days compared to 14.2 +/- 1.0 days for controls (p < 0.01). This effect was specific for vIL-10 encoding vector and could be inhibited by anti-vIL-10 monoclonal antibody (mAb). In vivo administration of adenovirus facilitated the generation of adenovirus-specific cytotoxic T lymphocytes (CTL), whereas treatment with AdSV40vIL-10 prevented CTL priming and generation of virus-specific immunity. AdSV40vIL-10 also induced extended expression of a beta-galactosidase reporter from a co-injected LacZ-encoding adenoviral vector. These results demonstrate that adenovirus-mediated gene transfer and expression of vIL-10 prolong allograft survival and inhibit the immune response to adenoviral antigens, thereby improving the persistence of the vector and extending transgene expression. The efficacy of adenoviral vectors can be improved by incorporating immunosuppressive genes into the vector.

[The study of resonant multi-photon ionization mechanism in the vapour of sodium]

By two-photon resonant three-photon ionization and two-photon hybrid resonant three-photon ionization in Na2-Na the different ion current strength with different temperature was measured. The result was discussed.

Electrical stimulation prevents immobilization atrophy in skeletal muscle of rabbits

OBJECTIVE

To investigate the effect of unilateral cast immobilization with and without surface electrical stimulation (ES) on the tibialis anterior (TA) muscle of rabbits.

DESIGN

Prospective randomized trial.

SETTING

University medical school.

ANIMALS

53 New Zealand White rabbits (aged 54 to 63 days, weight 1.73 to 1.91 kg). METHODS AND INTERVENTION: Random assignment, for a 3-week period, to one of four groups: C group (control group), I group (immobilization group), S group (group of electrical stimulation which was stimulated isometrically at 50 Hz, 30 minutes per day, 5 times a week), and IS group (immobilization group which, like the S-group, received electrical stimulation).

OUTCOME MEASURES

Muscle wet wight, muscle fiber cross-sectional area, muscle fiber types, and muscle capillary supply.

RESULTS

Muscle wet weight decreased significantly in the I group by 19% (p < or = .05), with a corresponding significant reduction in the total muscle fiber cross-sectional area of 26% (p < or = .05). No significant changes were observed in muscle wet weight and muscle fiber cross-sectional area in the S and IS groups. Interstitial fibrosis was observed in the I group and occasionally in the IS group. No significant changes in the total number of muscle fiber types I and II were found in all experimental groups. The capillary supply of the S and IS groups did not change significantly. However, capillary-to-fiber ratio was significantly reduced by 20% with a simultaneously nonsignificant increase in capillary density (capillaries/mm2) of 11% (p > .05) in the I group. Furthermore, muscle fiber regeneration was observed predominantly in the I group.

CONCLUSIONS

In this experimental model, ES effectively prevented immobilization-induced muscle atrophy by minimizing reduction of muscle fiber cross-sectional area, interstitial fibrosis, and impaired blood supply.

Retinoid X receptor-specific ligands synergistically upregulate 1, 25-dihydroxyvitamin D3-dependent transcription in epidermal keratinocytes in vitro and in vivo

We have examined the mechanism by which endogenous retinoid X receptor (RXR), vitamin D3 receptor (VDR), and cognate ligands regulate nuclear 1,25-dihydroxyvitamin D3 (D3) signaling in epidermal keratinocytes from skin, a physiologic D3 target. In vitro, RXR and VDR-specific antibodies identified endogenous RXR and VDR bound to a vitamin D3-responsive element (DR3) as heterodimers (VDR-RXR). In cultured keratinocytes, 9-cis retinoic acid (9cRA), a panagonist for RXR and retinoic acid receptor (RAR), and an RXR-selective agonist, SR11237, synergized with D3 to activate DR3 via endogenous as well as overexpressed VDR-RXR, whereas both of these RXR agonists alone were ineffective. In contrast, SR11237 did not synergize with but antagonized an RAR-selective ligand activation of a retinoic acid-responsive element (DR5) via endogenous RAR-RXR. Furthermore, expression of RXR mutated in transactivation domain AF-2 inhibited endogenous VDR-RXR activity over DR3. This mutant efficiently bound to DR3 as VDR-RXR but showed reduced capacity to transactivate DR3 in response to D3 and SR11237. In vivo, D3 and SR11237 synergistically induced the naturally occurring D3-responsive 24-hydroxylase gene in epidermis of mouse skin, whereas SR11237 alone was ineffective. Our data suggest that allosteric changes caused by VDR in DR3-bound VDR-RXR do not block access of ligands to RXR. RXR ligand-induced conformational changes permit VDR-RXR, via both VDR and RXR activation function domains, to mediate maximal D3 signaling in keratinocytes.

Hepatocyte growth factor activator inhibitor, a novel Kunitz-type serine protease inhibitor

Hepatocyte growth factor (HGF) activator is a serine protease that is produced and secreted by the liver and circulates in the blood as an inactive zymogen. In response to tissue injury, the HGF activator zymogen is converted to the active form by limited proteolysis. The activated HGF activator converts an inactive single chain precursor of HGF to a biologically active heterodimer in injured tissue. The activated HGF may be involved in the regeneration of the injured tissue. In this study, we purified an inhibitor of HGF activator from the conditioned medium of a human MKN45 stomach carcinoma cell line and molecularly cloned its cDNA. The sequence of the cDNA revealed that the inhibitor has two well defined Kunitz domains, suggesting that the inhibitor is a member of the Kunitz family of serine protease inhibitors. The sequence also showed that the primary translation product of the inhibitor has a hydrophobic sequence at the COOH-terminal region. Inhibitory activity toward HGF activator was detected in the membrane fraction as well as in the conditioned medium of MKN45 cells. These results suggest that the inhibitor may be produced as a membrane-associated form and secreted by the producing cells as a proteolytically truncated form.

[Computer image analysis of 20 tiny medicinal seeds]

Twenty tiny medicinal seeds were determined by computer image analysis. The diameter, perimeter, area, volume and irregular parameter of the seeds are presented.

Transcriptional repression by Oshox1, a novel homeodomain leucine zipper protein from rice

This paper describes the characterization of Oshox1, a cDNA clone from rice encoding a member of the homeodomain-leucine zipper (HD-Zip) class of putative transcription factors. Oshox1 maps to chromosome 10 and belongs to a family of related rice genes. Two-hybrid assays showed that Oshox1 protein can homodimerize, but can also form heterodimers with an Arabidopsis HD-Zip protein. This suggests that protein-protein interactions may also occur between different HD-Zip proteins in rice, which would provide enormous versatility for generating specific gene-control mechanisms. Oshox1 mRNA could be detected in various rice tissues at different developmental stages, with highest levels in embryos, shoots of seedlings, and leaves of mature plants. Transgenic expression of Oshox1 in Arabidopsis retarded growth and affected leaf size and shape, indicative of a role as developmental regulator. In vitro and in vivo DNA-binding studies revealed that Oshox1 interacts with the pseudopalindromic sequence CAAT(C/G)ATTG, confirming that the protein represents a transcription factor. Oshox1 was found to repress reporter gene activity in rice suspension cells, most likely by a mechanism of active transcriptional repression. Repression was strictly dependent on the presence of upstream Oshox1 binding sites in the reporter gene constructs and a function of the N-terminal region of Oshox1, preceding the homeodomain.

Neutrophil emigration in the lungs

Neutrophil emigration into the lung occurs in response to inflammatory mediators in the interstitium and the airspace. Emigration through the pulmonary microvasculature occurs through two pathways, one that requires CD11/CD18 and ICAM-1 and one that does not: Which pathway is utilized is determined by the stimulus. The ability of a stimulus to upregulate ICAM-1 by inducing the production of pro-inflammatory cytokines including TNF-alpha appears to determine the selection of the CD11/CD18, ICAM-1, ICAM-1-dependent pathway Recently, a third pathway has been identified that requires CD11/CD18 but not ICAM-1. The ligand for this pathway, as well as the ligands for CD11/CD18, ICAM-1-independent adhesion have not been identified. During recurrent pneumonia, the adhesion molecules required for emigration are different than those utilize during acute inflammation in previously normal lung tissue. For example, studies investigating the role of CD11/CD18 in recurrent pneumonia induced by P. aeruginosa, a stimulus which elicits CD11/CD18-dependent emigration initially, showed that when the organisms are instilled at the same site 7 days after the initial instillation, most emigration occurs through CD11/CD18-independent mechanisms. These studies suggest that when an acute stimulus is placed at a site of resolving inflammation, new pathways of adhesion are recruited. Whether these molecules are the same ones mediating acute CD11/CD18-independent adhesion remains to be determined. In summary, neutrophil emigration in the lung can occur through several adhesion pathways, which pathway is utilized can change during the inflammatory process, and cytokines participate in the selection of the pathway.

The roles of CD11/CD18 and ICAM-1 in acute Pseudomonas aeruginosa-induced pneumonia in mice

Neutrophil accumulation in response to Pseudomonas aeruginosa in the lungs is mediated through CD11/CD18. This study determined the roles of CD11a, CD11b, and intercellular adhesion molecule (ICAM)-1 in P. aeruginosa-induced pneumonia and compared the function of ICAM-1 using Abs or ICAM-1 mutant mice. Anesthetized BALB/c mice pretreated with either Abs against CD11a, CD11b, ICAM-1, or rat IgG received intratracheal instillation of P. aeruginosa for 4 h. In other studies, ICAM-1 mutant and wild-type mice received either anti-ICAM-1 Ab or rat IgG followed by instillation of P. aeruginosa. The data show that Abs against CD11a, CD11b, and ICAM-1 in BALB/c mice inhibited neutrophil emigration by 79, 81, and 56%, respectively. ICAM-1 mutant mice showed no inhibition of neutrophil emigration compared with wild-type mice. Pretreatment with anti-ICAM-1 Ab inhibited neutrophil emigration in wild-type (129/SvxC57) mice by 67% but had no effect in ICAM-1 mutant mice, suggesting that the Ab was acting specifically through recognition of its Ag. We conclude that CD11a and CD11b are required for neutrophil emigration. The observed function of ICAM-1 varies depending on the method by which it is inhibited. Abs may overestimate function by altering other cellular functions or mutant mice may develop alternative pathways of emigration.

The roles of CD11/CD18 and ICAM-1 in acute Pseudomonas aeruginosa-induced pneumonia in mice

Neutrophil accumulation in response to Pseudomonas aeruginosa in the lungs is mediated through CD11/CD18. This study determined the roles of CD11a, CD11b, and intercellular adhesion molecule (ICAM)-1 in P. aeruginosa-induced pneumonia and compared the function of ICAM-1 using Abs or ICAM-1 mutant mice. Anesthetized BALB/c mice pretreated with either Abs against CD11a, CD11b, ICAM-1, or rat IgG received intratracheal instillation of P. aeruginosa for 4 h. In other studies, ICAM-1 mutant and wild-type mice received either anti-ICAM-1 Ab or rat IgG followed by instillation of P. aeruginosa. The data show that Abs against CD11a, CD11b, and ICAM-1 in BALB/c mice inhibited neutrophil emigration by 79, 81, and 56%, respectively. ICAM-1 mutant mice showed no inhibition of neutrophil emigration compared with wild-type mice. Pretreatment with anti-ICAM-1 Ab inhibited neutrophil emigration in wild-type (129/SvxC57) mice by 67% but had no effect in ICAM-1 mutant mice, suggesting that the Ab was acting specifically through recognition of its Ag. We conclude that CD11a and CD11b are required for neutrophil emigration. The observed function of ICAM-1 varies depending on the method by which it is inhibited. Abs may overestimate function by altering other cellular functions or mutant mice may develop alternative pathways of emigration.

Gene transfer of transforming growth factor-beta 1 prolongs murine cardiac allograft survival by inhibiting cell-mediated immunity

Delivery of immunosuppressants directly to allografts using gene transfer and gene therapy approaches may inhibit immune activation while avoiding the systemic toxicity of conventional immunosuppression. Cardiac grafts from allogeneic (C57BL/6, H-2b) donors were transplanted into CBA/J (H-2k) recipients in a heterotopic, non-vascularized model pSVTGF-beta 1, a plasmid encoding murine transforming growth factor-beta 1 (TGF-beta 1) under the control of an SV40 promoter, was directly injected into grafts at surgery and prolonged survival from 12.0 +/- 0.7 to 25.1 +/- 2.1 days (p < 0.001) in a dose-dependent manner. Plasmid gene transfer-induced immunosuppression was localized to the area of the graft because plasmid injected remote from the graft did not prolong allograft survival and systemic immunity was not influenced by local gene transfer. Limiting dilution analysis of graft-infiltrating cells demonstrated that gene transfer reduced the precursor frequency of donor-specific cytotoxic T lymphocytes (CTL) and activated and total interleukin-2 (IL-2) producing helper T lymphocytes (HTL) in graft-infiltrating cells, whereas CTL generation and HTL precursor frequency in splenic lymphocytes were not altered. Additional data revealed that gene transfer inhibited the priming of TH0 cells and the conversion of primed TH1 cells to activated cells without the participation of TH2 suppressors. These data demonstrate that gene transfer of plasmid DNA encoding TGF-beta 1 in vivo suppresses local T cell immunity, which prolongs allograft survival.

Blockade of multiple costimulatory receptors induces hyporesponsiveness: inhibition of CD2 plus CD28 pathways

T-lymphocyte activation requires engagement of the T cell receptor with antigen-major histocompatibility complex, and simultaneous ligation of costimulatory pathways via the lymphocyte receptors CD2 and CD28/ CTLA4. Anti-CD2 monoclonal antibody (mAb) blocks the interaction of the antigen-presenting cell receptor CD48 with its ligand CD2, whereas CTLA4Ig binds with high affinity to the antigen-presenting cell ligands B7-1 and B7-2, blocking their interaction with CD28/CTLA4. We tested the immunosuppressive effects of simultaneously blocking both costimulatory pathways. Using donor C57BL/6J (H2b) hearts transplanted to CBA/J (H2k) recipients, anti-CD2 mAb plus CTLA4Ig administered at the time of transplantation prolonged cardiac allograft mean survival time to >120 days compared with untreated controls (12.2+/-0.5 days, P<0.01), anti-CD2 mAb alone (24.8+/-1.0 days, P<0.01), or CTLA4Ig alone (55.0+/-2.0 days, P<0.01). Retransplantation of these recipients with donor-specific and third-party grafts demonstrated that hyporesponsiveness and tolerance were achieved. In vitro stimulation of lymphocytes from tolerant recipients with donor-specific alloantigen resulted in normal cytotoxic T lymphocyte and mixed lymphocyte reaction responses, showing that clonal deletion or anergy did not occur, but that graft adaptation or suppression likely helped to maintain long-term graft survival. In vitro combinations of anti-CD2 mAb and CTLA4Ig suppressed the generation of allogeneic cytotoxic T lymphocytes (58%) and the mixed lymphocyte reaction (36%); CTLA4Ig was more effective in this regard and the two agents were not synergistic. Anti-CD2 mAb and CTLA4Ig suppressed mitogen-driven proliferation in differential fashions, suggesting that they affected independent signaling pathways. Anti-CD2 mAb and CTLA4Ig also inhibited interleukin (IL)-2, IL-4, and IL-2 receptor (CD25). These data indicate that anti-CD2 mAb plus CTLA4Ig induces hyporesponsiveness and tolerance. The mechanism is likely related to the initial disruption of independent pathways of T-lymphocyte activation leading to antigen-specific long-term graft survival.

A novel murine model for the assessment of human CD2-related reagents in vivo

CD2 is a T cell surface glycoprotein that mediates both cell-cell adhesion and transmembrane signal transduction. To construct a model for the in vivo evaluation of human (h)CD2 function and hCD2-related reagents, hCD2 transgenic mice and murine (m)CD2 knockout mice were crossed, and the F2 generation selected for mCD2-hCD2+ animals by fluorescent flow cytometry. The mCD2-hCD2+ mice are healthy and have a normal distribution of mCD3, mCD4, and mCD8 in thymus, spleen, and lymph node. Therefore expression of the hCD2 transgene does not appear to disrupt normal T cell development. The functionality of hCD2 was demonstrated by T lymphocyte proliferation upon stimulation by combined anti-CD2 plus anti-CD2R (anti-T11(2) plus anti-T11(3)) mAbs. Anti-T11(2) plus anti-T11(3) anti-human CD2 mAbs also induced proliferation of mCD2+hCD2+ F1 lymphocytes, but not mCD2+hCD2- wild-type murine lymphocytes. Either an anti-murine or the human CD2 specific (anti-T11(1)) mAbs inhibited proliferation in alloantigen, PHA, or anti-CD3 mAb stimulated cultures and inhibited only cells bearing the appropriate cognate CD2. In vivo studies of immune function yielded results consistent with these in vitro assays. Thus, anti-T11(1) mAb suppressed contact sensitivity in vivo in the transgenic/knockout mice. mCD2-hCD2+ mice treated with anti-T11(1) or LFA-3 fusion proteins also showed significant prolongation of cardiac allograft survival. This prolongation was associated both with depletion and down-modulation of CD2 on remaining T cells. These data suggest that the transgenic/knockout mice provide a useful in vivo model for the assessment of hCD2-related reagents and CD2 function, free from any potential interactions with mCD2 and mCD2 ligands.

[Flavonoids in the rhizome of Sparganum stoloniferum Buch.-Ham]

Two compounds were isolated from the rhizome of sparganum stoloniferum. Based on the physicochemical constants and spectral data, they were identified as kaempferol and 5',7,3',5-tetrahydroxy-flavanonol-3-O-beta-D-glu.

A novel murine model for the assessment of human CD2-related reagents in vivo

CD2 is a T cell surface glycoprotein that mediates both cell-cell adhesion and transmembrane signal transduction. To construct a model for the in vivo evaluation of human (h)CD2 function and hCD2-related reagents, hCD2 transgenic mice and murine (m)CD2 knockout mice were crossed, and the F2 generation selected for mCD2-hCD2+ animals by fluorescent flow cytometry. The mCD2-hCD2+ mice are healthy and have a normal distribution of mCD3, mCD4, and mCD8 in thymus, spleen, and lymph node. Therefore expression of the hCD2 transgene does not appear to disrupt normal T cell development. The functionality of hCD2 was demonstrated by T lymphocyte proliferation upon stimulation by combined anti-CD2 plus anti-CD2R (anti-T11(2) plus anti-T11(3)) mAbs. Anti-T11(2) plus anti-T11(3) anti-human CD2 mAbs also induced proliferation of mCD2+hCD2+ F1 lymphocytes, but not mCD2+hCD2- wild-type murine lymphocytes. Either an anti-murine or the human CD2 specific (anti-T11(1)) mAbs inhibited proliferation in alloantigen, PHA, or anti-CD3 mAb stimulated cultures and inhibited only cells bearing the appropriate cognate CD2. In vivo studies of immune function yielded results consistent with these in vitro assays. Thus, anti-T11(1) mAb suppressed contact sensitivity in vivo in the transgenic/knockout mice. mCD2-hCD2+ mice treated with anti-T11(1) or LFA-3 fusion proteins also showed significant prolongation of cardiac allograft survival. This prolongation was associated both with depletion and down-modulation of CD2 on remaining T cells. These data suggest that the transgenic/knockout mice provide a useful in vivo model for the assessment of hCD2-related reagents and CD2 function, free from any potential interactions with mCD2 and mCD2 ligands.

[Interspecific difference and intraspecific variation of coumarins in Cnidium species]

According to the results of TLC and assay of coumarins, the interspecific difference of coumarins in 4 Cnidium species is obvious, and 4 chemotypes have been found in Cnidium monnieri.

Therapeutic effect of Gag-nuclease fusion protein on retrovirus-infected cell cultures

Capsid-targeted viral inactivation is a novel protein-based strategy for the treatment of viral infections. Virus particles are inactivated by targeting toxic fusion proteins to virions, where they destroy viral components from within. We have fused Staphylococcus nuclease (SN) to the C-terminal end of Moloney murine leukemia virus Gag and demonstrated that expression of this fusion protein in chronically infected chicken embryo fibroblasts resulted in its incorporation into virions and subsequent inactivation of the virus particles by degradation of viral RNA. Release of particles incorporating Gag-SN fusion proteins into the extracellular milieu activates the nuclease and results in destruction of the virion from within. By comparing the effects of incorporated SN and SN*, an enzymatically inactive missense mutant form of SN, on the infectivity of virus particles, we have clearly demonstrated that nucleolytic activity is the antiviral mechanism. Expression of Gag-SN fusion proteins as a therapeutic agent causes a stable reduction of infectious titers by 20- to 60-fold. The antiviral effect of capsid-targeted viral inactivation in our model system, using both prophylactic and therapeutic approaches, suggests that a similar anti-human immunodeficiency virus strategy might be successful.

Characterization of long-term survivors of human immunodeficiency virus type 1 infection

A small population of HIV-1-infected individuals remains clinically healthy and immunologically normal for more than ten years. We have studied ten subjects who have been asymptomatic with normal and stable CD4+ lymphocyte counts, despite 12 to 16 years of HIV-1 infection, to gain information on the determinants of nonprogression. Multiple methods were used to determine the viral load in their blood. Plasma cultures were uniformly negative for infectious virus. However, particle-associated HIV-1 RNA was detectable in four subjects using a sensitive branched DNA amplification assay. In peripheral blood mononuclear cells (PBMC), infectious HIV-1 was quantified in three subjects using a standard limiting-dilution culture method. Infectious virus was recovered from another subject using a CD8-depleted culture. In contrast, six subjects had no detectable infectious virus in PBMC. All had detectable viral DNA in PBMC by a quantitative polymerase chain reaction assay, but the copy numbers were low, ranging from 10 to 100 copies per 10(6) PBMC in all but two subjects. Overall, the viral burden in the plasma and PBMC of long-term survivors was orders of magnitude lower than those typically found in progressors. Possible mechanisms for low levels of HIV-1 in vivo were examined experimentally.

[Study on the death of Escherichia coli induced by hydrostatic pressures]

The effect of hydrostatic pressure on the death of E. coli was studied in this paper. The results indicated that E. coli could be killed by hydrostatic pressure above 800 bar. At 2300 bar E. coli was totally killed in 30 minutes. The time course of E. coli death induced by pressure indicated that the most E. coli was killed in the first 10 minutes after the pressure was applied. It was also found that the lower temperature favored killing E. coli under pressure.

Enforced interaction of one molecule of plastocyanin with two molecules of cytochrome c and an electron-transfer reaction involving the hydrophobic patch on the plastocyanin surface

Laser flash photolysis is used to study the photoinduced electron-transfer reaction cyt(III)//pc(II) + 3Zncyt --> cyt(III)//pc(I) + Zincyt+ at pH 7.0 and 25 degrees. In the covalent (symbol//) complex cyt(III)//pc(II) the acidic patch in cupriplastocyanin is directly cross-linked to the basic patch in ferricytochrome c. The triplet state of zinc cytochrome c reduces the pc(II) moiety, not the cyt(III) moiety, of the covalent complex. The reaction is strictly bimolecular in the entire range of ionic strength studied, from 1.25 mM to 1.00 M. The two reactants interact only transiently, in a collisional complex, and do not form a persistent complex cyt(III)//pc(II)/Zncyt. Because noncovalent (symbol/) association of three separate protein molecules is far less probable than association of the covalent complex and another protein molecule, we conclude that, without the aid of covalent cross-links, one molecule of plastocyanin will not form a ternary complex with two molecules of cytochrome c, cyt/pc/cyt. Dependence of the rate constant on ionic strength is analyzed in terms of van Leeuwen theory of electrostatic interactions, which recognizes the importance of dipole moments of the proteins. This analysis shows that 3Zncyt reacts with the hydrophobic patch in the pc(II) moiety of the covalent complex cyt(III)//pc(II). At high ionic strength, at which electrostatic interactions are practically abolished, the blue copper site is reduced with approximately equal rates via the hydrophobic patch in the pc(II) moiety of the complex and via the acidic patch in free pc(II). This is evidence that the two distinct patches on the plastocyanin surface are comparable in their intrinsic "conductivity" for electrons coming to the copper site. Positively charged and electroneutral redox partners tend to react at the acidic patch (although not necessarily at the initial docking site in this broad patch) for electrostatic, not electronic, reasons. Earlier theorectical studies disagreed about the relative electronic conductivities of the two patches. This experimental study corroborates very recent theoretical studies that found the two patches to be comparable in the efficiency of electron transfer.

Retrovirus-mediated transfer of viral IL-10 gene prolongs murine cardiac allograft survival

A murine heterotopic, nonvascularized cardiac allograft model was used to examine the effects of the immunosuppressive cytokine, viral IL-10 (vIL-10), delivered by gene transfer on graft rejection. Retroviral-mediated gene transfer and expression of vIL-10 significantly prolonged allograft survival, without conventional systemic immunosuppression, from 12.1 +/- 0.8 days to 39.4 +/- 2.5 days (p < 0.0001). The effect was specific, dose dependent, and restricted to the site of transplantation. PCR analysis demonstrated specific expression of the transferred gene within the allograft. Analysis of the cellular infiltrate in the allografts showed a reduction in T cells and alloantigen-specific cytotoxic T cells and IL-2 producing helper T cells. Thus, the transient local expression of a gene encoding an immunosuppressive protein within a graft can generate local immunosuppression, making gene therapy a viable approach for facilitating transplantation.

Retrovirus-mediated transfer of viral IL-10 gene prolongs murine cardiac allograft survival

A murine heterotopic, nonvascularized cardiac allograft model was used to examine the effects of the immunosuppressive cytokine, viral IL-10 (vIL-10), delivered by gene transfer on graft rejection. Retroviral-mediated gene transfer and expression of vIL-10 significantly prolonged allograft survival, without conventional systemic immunosuppression, from 12.1 +/- 0.8 days to 39.4 +/- 2.5 days (p &lt; 0.0001). The effect was specific, dose dependent, and restricted to the site of transplantation. PCR analysis demonstrated specific expression of the transferred gene within the allograft. Analysis of the cellular infiltrate in the allografts showed a reduction in T cells and alloantigen-specific cytotoxic T cells and IL-2 producing helper T cells. Thus, the transient local expression of a gene encoding an immunosuppressive protein within a graft can generate local immunosuppression, making gene therapy a viable approach for facilitating transplantation.

Anti-CD2 monoclonal antibody-induced receptor changes. II. Interaction of CD2 and CD3

Anti-CD3 monoclonal antibodies (mAbs) and anti-CD2 mAbs each prolong allograft survival and cause transient downmodulation of homologous receptor expression. Anti-CD2 mAbs also act synergistically with anti-CD3 mAbs to prolong allograft survival and induce tolerance. The effect of combined anti-CD2 and anti-CD3 mAb treatment on receptor expression was further analyzed with an in vitro model. The anti-CD2 mAb 12-15 caused CD2 expression on purified splenic T cells to decrease from 72.6% [mean channel fluorescence (MCF) 0.68] to 41.5% (0.45) total positive cells while CD3 expression remained unchanged [69.1% (3.47) to 76.4% (4.04)]. The anti-CD3 mAb 2C11 caused CD2 expression to increase from 72.6% (0.68) to 93.0% (1.74) while CD3 expression decreased from 69.1% (3.47) to 62.6% (2.15). The combination of anti-CD2 plus anti-CD3 preserved CD2 expression (72.6 to 71.1%) while still decreasing CD3 expression [69.1% (3.47) to 69.9% (2.37)]. Modulation of CD2 and CD3 expression was similar on mixed splenic T lymphocytes and isolated CD4 and CD8 subsets. Modulation did not change with the addition of the cytokines IL-1, IL-2, IL-4, IL-6, IL-10, TNF alpha, or TGF beta. Kinetic studies showed that modulation of CD2 was rapid, persistent, and of the same magnitude from Day 1 to Day 7 of culture while CD3 downmodulation was transient. The results of transcriptional analysis and receptor distribution suggested that downmodulation was due to receptor internalization while upmodulation was due to increased transcription. Analysis of expression of other adhesion molecules demonstrated that CD11a, CD18, CD44, CD45, CD48, CD54, and CD62L were significantly increased by either anti-CD2 or anti-CD3 mAbs while the combination was not synergistic. However, anti-CD3 significantly decreased VLA-4 alpha (CD49d) expression and anti-CD2 enhanced this decrease. Conversely anti-CD3 significantly increased IL-2R (CD25) expression and anti-CD2 profoundly inhibited the increase. These results show that anti-CD2 and anti-CD3 mAbs significantly modulate CD2 and CD3 expression on T cells and modulation is accompanied by changes in the array of other T cell surface receptors. Changes in cell surface receptor display may provide an additional explanation for the synergistic effect of anti-CD2 plus anti-CD3 in prolonging allograft survival.

[Studies on Cnidium fruits by stereological method and computer image analysis]

The fruits, pollen grains, vascular bundles, stomata and endosperm cells of 4 Cnidium species were studied and determined by stereological method and computer image analysis technique. Statistical data were presented. In the volume of fruit and the area of vascular bundle, Cnidium dahuricum is the biggest, then C. salinum, C. japonicum and C. monnieri successively. In the volume of pollen grain,C. salinum is the biggest, followed by C. dahuricum, C. japonicum and C. monnieri in succession. In the volume of endosperm cell, C. dahuricum is also the biggest, and then C. japonicum, C. salinum and C. monnieri in order.

Inter- and intraclade neutralization of human immunodeficiency virus type 1: genetic clades do not correspond to neutralization serotypes but partially correspond to gp120 antigenic serotypes

We have studied genetic variation among clades A through E of human immunodeficiency virus type 1 (HIV-1) at the levels of antibody binding to gp120 molecules and virus neutralization. We are unable to identify neutralization serotypes that correspond to the genetic clades. Instead, we observe that inter- and intraclade neutralization of primary isolates by HIV-1-positive sera is generally weak and sporadic; some sera show a reasonable degree of neutralization breadth and potency whereas others are relatively sensitive to neutralization, but no consistent pattern was found. However, a few sera were able to neutralize across clades with significant potency, an observation which may have implications for the feasibility of a broadly effective HIV-1 vaccine involving humoral immunity. Serological assays measuring anti-gp120 antibody binding also failed to identify serotypes that correspond precisely to the genetic clades, but some indications of clade-specific binding were observed, notably with sera from clades B and E. A representative protein for each clade (A through E) was selected on the basis of its specificity, defined as high seroreactivity with sera from individuals infected with virus of that clade and lower reactivity with sera from individuals infected with viruses from other clades. The seroreactivity patterns against these five proteins could be used to predict the genotype of the infecting virus with moderate success.

[The relation between p53 mutations and tumor invasiveness of human hepatocellular carcinoma]

We have combined the polymerase chain reaction (PCR) with the HaeIII enzyme restriction analysis to study the mutations at codon 249 of p53 gene in L02 human liver cell line, Bel-7402, SMMC-7721 human hepatocellular carcinoma cell lines and 19 surgical specimens of hepatocellular carcinoma (HCC) and their surrounding non-cancer liver tissues. None of the three cell lines and the non-cancer liver tissues was found to have p53 mutation; but 10 of 19 HCC samples (52.6%) had p53 point mutations, and the p53 gene mutated more frequently in HCC with incomplete capsule, intrahepatic metastasis, or multiple nodules than in those with well encapsulated (70% vs 33.3%, P < 0.05), no intrahepatic metastasis (71.4% vs 41.6%, P < 0.05) and single nodule (83.3% vs 38.5%, P < 0.05). These suggested that the codon 249 was a mutational hotspot of the p53 gene in human HCC seen in China, and p53 mutations may be related to invasiveness of human HCC.

Effect of schisanhenol on function and surface shape of rat neutrophils

AIM

To study the regulatory effect of Schisanhenol (Sal) on function of rat neutrophils.

RESULTS

It was found that Sal (1, 10, and 100 mumol.L(-1)) inhibited neutrophil activities such as chemotaxis, phagocytosis, and superoxide anion production in vitro in a concentration-dependent manner. Changes of surface morphology of neutrophils were observed by scanning electron microscopy, showing that the ruffles and pseudopods on neutrophil surface increased under the stimulation by chemotactic peptide N-formyl-Met-Leu-Phe (FMLP). When pretreated with Sal 100 mumol.L(-1), the ruffles and pseudopods disappeared and the surface became smooth. Sal 100 mumol.L(-1) decreased the cytosolic calcium concentration of neutrophils and increased the intracellular cAMP level.

CONCLUSION

These data suggested that Sal could inhibit the function of rat neutrophils through affecting the cytosolic free calcium and cAMP level besides its anti-oxidant activity.

Anti-CD2 monoclonal antibody-induced receptor changes: down modulation of cell surface CD2

Anti-CD2 mAbs suppress T cell immunity and prolong allograft survival in vivo while inducing the down-modulation of CD2 expression. Manipulation of cell surface molecules may be important in inducing tolerance, so down-modulation of CD2 expression on T cells by anti-CD2 mAbs was further defined with an in vitro model. The anti-CD2 mAb 12-15 caused CD2 expression on purified splenic T cells to decrease from 83.4 to 22.7% total positive cells while CD3, CD4, and CD8 expression remained unchanged. The expression of other adhesion molecules, LFA-1 alpha (CD11a), LFA-1 beta (CD18), Pgp-1 (CD44), CD45, MEL-14 (L-selectin), and VLA-4 alpha (CD49d), were all increased as a result of anti-CD2 treatment, whereas CD25 (IL-2R), CD48 (CD2 ligand), and ICAM-1 (CD54) remained unchanged. Kinetics showed that CD2 down-modulation was persistent and at the same magnitude from day 1 through day 7 of culture. Anti-CD2 mAb could down modulate CD2 on both CD4 and CD8 splenic lymphocyte subsets, thymocytes, and the T cell lymphoma EL-4; and, non-T cells did not seem to participate in the process of modulation. Mechanistic studies of mAb action showed that, in addition to 12-15, other anti-CD2 mAbs could cause down-modulation of T cell CD2 expression in an epitope and isotype dependent fashion and that CD2 down-modulation correlated with inhibition of receptor-driven T cell stimulation. Intact antibody, including the Fc portion, was required to induce CD2 down-modulation, and additional experiments suggested an interaction with an Fc gamma R other than Fc gamma RII or Fc gamma RIII. CD2 down-modulation did not change with the addition of the cytokines IL-1, IL-2, IL-6, IL-10, TNF alpha, or TGF-beta 1. These results show that anti-CD2 mAbs significantly and persistently down-modulate CD2 on various T cell subpopulations. The mAbs must interact with both the CD2 receptor and an Fc gamma R. CD2 down-modulation is accompanied by changes in the array of other T cell surface receptors that may contribute to mechanisms of anti-CD2-induced immunosuppression.

P-selectin/ICAM-1 double mutant mice: acute emigration of neutrophils into the peritoneum is completely absent but is normal into pulmonary alveoli

Neutrophil emigration during an inflammatory response is mediated through interactions between adhesion molecules on endothelial cells and neutrophils. P-Selectin mediates rolling or slowing of neutrophils, while intercellular adhesion molecule-1 (ICAM-1) contributes to the firm adhesion and emigration of neutrophils. Removing the function of either molecule partially prevents neutrophil emigration. To analyze further the role of P-selectin and ICAM-1, we have generated a line of mice with mutations in both of these molecules. While mice with either mutation alone show a 60-70% reduction in acute neutrophil emigration into the peritoneum during Streptococcus pneumoniae-induced peritonitis, double mutant mice show a complete loss of neutrophil emigration. In contrast, neutrophil emigration into the alveolar spaces during acute S. pneumoniae-induced pneumonia is normal in double mutant mice. These data demonstrate organ-specific differences, since emigration into the peritoneum requires both adhesion molecules while emigration into the lung requires neither. In the peritoneum, P-selectin-independent and ICAM-1-independent adhesive mechanisms permit reduced emigration when one of these molecules is deficient, but P-selectin-independent mechanisms cannot lead to ICAM-1-independent firm adhesion and emigration.

Multiple vectors effectively achieve gene transfer in a murine cardiac transplantation model. Immunosuppression with TGF-beta 1 or vIL-10

The application of gene transfer techniques to organ transplantation offers the potential for modulation of immunity directly within an allograft without systemic side effects. Expression vectors and promoter elements are important determinants of gene transfer and expression. In this study, various vectors (naked plasmid DNA, retroviral vector, herpes simplex viral vector, and adenoviral vector) with various promoters (RSV-LTR, SV40, MuLV-LTR, HCMVie1) were directly compared to demonstrate the successful gene transfer and expression of beta-galactosidase in murine myoblasts in vitro and within murine heterotopic, nonvascularized cardiac isografts or allografts in vivo. Expression of transferred genes was not toxic to cells and strength of expression varied according to the type of vector. Plasmid DNA was expressed in myocytes, retroviral vector was expressed in the graft infiltrating cells, and herpes simplex and adenoviral vectors were expressed in both myocytes and graft-infiltrating cells. Preliminary studies evaluated the ability of these vectors to deliver immunologically important signals. Allografts injected with pSVTGF-beta 1, a plasmid-encoding transforming growth factor beta 1 (TGF-beta 1) under the control of the SV40 promoter, showed significant prolongation of graft survival of 26.3 +/- 2.5 days compared with 12.6 +/- 1.1 days for untreated allografts, and 12.5 +/- 1.5 days for the allografts injected with control plasmid (P < 0.05). Allografts injected with MFG-vIL-10, a retroviral vector encoding viral interleukin-10 under the control of the MuLV-LTR, showed prolongation of graft survival of 36.7 +/- 1.3 days versus 12.6 +/- 1.1 days for the untreated allograft, and 13.5 +/- 2.0 days for the allografts injected with control retroviral vector (P < 0.001). Both vectors were transcriptionally active in vivo and did not appear to have toxic effects. Gene therapy for transplantation can induce transient expression of immunologically relevant molecules within allografts that impede immune activation while avoiding the systemic toxicity of conventional immunosuppression.

Retinoic acid antagonizes basal as well as coal tar and glucocorticoid-induced cytochrome P4501A1 expression in human skin

Cytochrome P4501A1 is known to be expressed in skin and thus has been implicated in the pathogenesis of skin cancer due to certain environmental carcinogens. Retinoic acid (RA) has been used in chemoprevention of certain skin and other epithelial cancers. Therefore, we used Northern and Western analysis to determine the effect of externally applied RA on basal P4501A1 expression. RA reduced basal levels of P4501A1 mRNA and protein by 68 (n = 14, P = 0.005) and 75% (n = 7, P = 0.04) respectively. RA application also reduced basal levels of P4501A2 (another P4501A1 subfamily member) mRNA by 93% (n = 7, P = 0.001) as determined by reverse transcription-polymerase chain reaction. Interestingly, P4501A1 mRNA expression induced by coal tar or glucocorticoid (clobetasol) was reduced 46 (n = 10, P = 0.003) and 69% (n = 5, P < 0.05) respectively by RA co-application. Downregulation of basal P4501A1 expression and antagonism of coal tar mediated P4501A1 induction by RA may be a mechanism involved in chemo-prevention of skin and other epithelial cancer by RA.

Virologic and immunologic characterization of long-term survivors of human immunodeficiency virus type 1 infection

BACKGROUND

In most subjects infected with human immunodeficiency virus type 1 (HIV-1), clinical or laboratory evidence of immunodeficiency develops within 10 years of seroconversion, but a few infected people remain healthy and immunologically normal for more than a decade. Studies of these subjects, termed long-term survivors, may yield important clues for the development of prophylactic and therapeutic interventions against the acquired immunodeficiency syndrome.

METHODS AND RESULTS

We studied 10 seropositive subjects who remained asymptomatic with normal and stable CD4+ lymphocyte counts despite 12 to 15 years of HIV-1 infection. Plasma cultures were uniformly negative for infectious virus. However, particle-associated HIV-1 RNA was detected in four subjects with a sensitive branched-DNA signal-amplification assay, whereas in five others the levels of HIV-1 RNA were too low to detect. Infectious HIV-1 was detected in peripheral-blood mononuclear cells (PBMC) of three subjects by standard limiting-dilution cultures, and infectious virus was recovered from another subject with use of a CD8-depleted culture. The other six subjects had no detectable infectious virus in their PBMC. A quantitative polymerase-chain-reaction assay revealed that all subjects had detectable but low titers of viral DNA in PBMC. Overall, the viral burden in the plasma and PBMC of long-term survivors was orders of magnitude lower than that typically found in subjects with progressive disease. There was no in vitro evidence of resistance by host CD4+ lymphocytes to HIV-1 infection. However, long-term survivors had a vigorous, virus-inhibitory CD8+ lymphocyte response and a strong neutralizing-antibody response. In two subjects the kinetics of viral replication were consistent with the presence of a substantially attenuated strain of HIV-1.

CONCLUSIONS

Subjects who remain asymptomatic for many years despite HIV-1 infection have low levels of HIV-1 and a combination of strong virus-specific immune responses with some degree of attenuation of the virus.

CD3 and CD2 ligation alters CD49d epitope expression

The combination of anti-CD2 plus anti-CD3 monoclonal antibodies (mAbs) synergistically prolongs allograft survival and induces antigen-specific tolerance. Since altered expression of cell surface molecules might be important for tolerance induction, the effect of anti-CD2 and anti-CD3 mAbs on the expression of adhesion molecules was analyzed on splenic T cells with an in vitro model. The anti-CD2 mAb, 12-15, alone had no effect on the expression of integrin alpha 4-chain epitopes recognized by two anti-CD49d (VLA-4 alpha) mAbs, R1-2 and PS/2. The anti-CD3 mAb, 2C11, caused R1-2 epitope expression to decrease, while PS/2 epitope expression remained unchanged. The combination of anti-CD2 and anti-CD3 mAbs further decreased R1-2 epitope expression while preserving PS/2 epitope expression. The expression of integrin beta 1 and beta 7 chains, each of which form heterodimers with alpha 4 chains, also remained unchanged. Expression of other integrin, selectin, or immunoglobulin superfamily molecules (CD11a, CD18, CD44, CD45, CD48, CD54 and CD62L) were all significantly increased by anti-CD2 or anti-CD3 mAbs. Decreased R1-2 epitope expression was anti-CD3 dependent and specifically augmented by anti-CD2 mAb. CD2-regulated decreases in R1-2 epitope expression correlated with increased cAMP and could be prevented by addition of high doses of IL-2 but was not affected by the addition of other cytokines. R1-2 alpha 4 epitope expression could be specifically restored by the divalent cation Mn2+, which also increased functional binding to the VCAM-1 ligand. Significantly, the R1-2 but not the PS/2 mAb prolonged graft survival in a cardiac allograft model. These results show that anti-CD2 and anti-CD3 mAbs selectively decrease integrin alpha 4 chain epitope expression on T cells through conformational regulation. Decreased expression of a CD49d epitope is unique in comparison to the up-modulation of other T-cell adhesion receptors. These changes correlate with functional effects and provide an additional mechanistic explanation for the synergistic effect of anti-CD2 plus anti-CD3 in producing tolerance.

Increased cAMP and cAMP-dependent protein kinase activity mediate anti-CD2 induced suppression of anti-CD3-driven interleukin-2 production and CD25 expression

Anti-CD2 monoclonal antibody (mAb) can act synergistically with anti-CD3 to produce tolerance and diminish the anti-CD3-induced cytokine syndrome. Since interleukin(IL)-2 production and IL-2 receptor (IL-2R; CD25) expression are important determinants of CD3-driven T cell activation, the effects of anti-CD2 on anti-CD3-induced CD25 expression and IL-2 production were analyzed and related mechanistically to CD2-stimulated cAMP signaling with an in vitro model of T cell activation. The anti-CD2 mAb, 12-15, alone had no effect on splenic T cell CD25 expression and IL-2 production, while the anti-CD3 mAb, 145-2C11, caused significant increases in both CD25 expression and IL-2 production. The addition of anti-CD2 inhibited anti-CD3-induced increases in CD25 and IL-2. The inhibitory signal delivered by anti-CD2 was effective in many forms of T cell activation, since other stimuli which increased CD25, such as concanavalin A, phytohemagglutinin, and Staphylococcal enterotoxin B (SEB), could also be inhibited by anti-CD2. The inhibitory effect of anti-CD2 on CD25 could not be reversed by high doses of supplemental IL-2 added to the culture. Anti-CD2 increased cytoplasmic cAMP in a dose- and time-dependent manner. Reagents that increased cytoplasmic cAMP such as forskolin, cholera toxin, and 3'-isobutyl-1-methylxanthine could mimic the inhibitory effect of anti-CD2 on anti-CD3-driven CD25 expression. Anti-CD2 also increased the activity of cAMP-dependent protein kinase (PKA). H8, a PKA antagonist, blocked the inhibitory effect of anti-CD2 on CD25 expression, further confirming the role of PKA in CD2-induced negative signaling. The use of paired agonists to PKA demonstrated that a type I PKA was the preferential enzyme isoform stimulated by CD2 ligation. These findings show that increased cAMP and PKA activity mediate anti-CD2-induced suppression of anti-CD3-driven IL-2 production and CD25 expression, and provide mechanisms for anti-CD2-induced immunosuppression and inhibition of the cytokine syndrome associated with anti-CD3 treatment.

Design of a cryogenic videocamera-recorder and image processing system and calculation of volumes of red cells

Since Rowe reported that the storage technique for red cells at very low temperatures had been realized successfully, many experts who work in the fields of cryobiology and medicine have turned their attention to this storage technique for tissues and organs. Since the first quantitative cryomicroscope was made successfully about 20 years ago, it has been possible to observe changes in shape and phase. Particularly the image processing technique has laid the foundation for quantitative analysis of the relationship between changes in shape and damage from freezing of cells and cooling rate and storage temperature. In this work, we constructed a system consisting of a cryomicroscope, a videocamera-recorder, and an image processor. We carried out many experiments with red cells in cold storage and have established a model for calculating the volumes of red cells. In our experiments we also dynamically traced the shape changes of cells with various experimental parameters.

CTLA4Ig prolongs allograft survival while suppressing cell-mediated immunity

T cell activation is the result of antigen-specific interactions with the TCR/CD3 complex and costimulation via other T cell surface receptors. Prevention of costimulation can result in clonal anergy. CTLA4Ig is a fusion protein that binds with high-affinity to the B7/BB1 ligand and blocks the interaction of this ligand with CD28 and CTLA4. We explored the immunosuppressive effects of CTLA4Ig in a murine nonvascularized heterotopic cardiac transplant model and in a model of cell mediated immunity. CTLA4Ig administered in vivo for two days at the time of transplantation resulted in significant prolongation of allograft survival (55 +/- 2.0 vs. 12.2 +/- 0.5 days for control, P < 0.03). Administration at later times or to previously primed animals produced no prolongation of graft survival. CTLA4Ig administered during in vivo immunization to the hapten TNP suppressed the contact sensitivity response and inhibited the subsequent in vitro generation of secondary TNP-specific CTL. CTLA4Ig administered in vivo had no effect on subsequent primary alloantigen-specific CTL or MLR responses--however, when added to culture the fusion protein inhibited the MLR response by 80%, but not the alloantigen-specific CTL response. CTLA4Ig inhibited CD4+ and CD8+ proliferative and cytokine responses to alloantigen. Flow cytometry showed no changes in distribution of subpopulations of T cells. These results confirm the immunosuppressive activity of CTLA4Ig in vivo in an allograft model and show that both CD4+ and CD8+ T cells are suppressed by CTLA4Ig. The most efficacious time of administration is during priming of the immune response at the time of antigen presentation.

Targeting of human immunodeficiency virus-infected cells by CD8+ T lymphocytes armed with universal T-cell receptors

We have developed an immunotherapeutic approach with potential application in the treatment of viral and malignant disease. We show that primary CD8+ T cells isolated from peripheral blood can be genetically modified by retroviral transduction to express high levels of universal (major histocompatibility complex-unrestricted) chimeric T-cell receptors specific for human immunodeficiency virus (HIV) antigens. Two classes of HIV-specific URs in which the antigen-binding domain is comprised of either CD4 or a single-chain antibody are capable of activating a number of T-cell effector functions in response to target cells, including cytolysis, in a highly sensitive and specific manner. Importantly, we have addressed a number of issues which, although particularly relevant to the clinical application of this approach in the treatment of HIV infection, may also impact on the potential of UR immunotherapy for other disease targets. The UR immunotherapeutic system is particularly suited for evaluation in the clinical setting.

Photoinduced electron transfer from the triplet state of zinc cytochrome c to ferricytochrome b5 is gated by configurational fluctuations of the diprotein complex

The intracomplex electron-transfer reaction 3Zncyt/b5(III)-->Zncyt+/b5(II) within electrostatic and covalent complexes of zinc(II) cytochrome c and ferricytochrome b5 is studied by laser flash photolysis. Kinetic effects of protein cross-linking and of solution viscosity are interpreted in terms of dynamic mobility of the associated proteins with respect to each other. The rate constant for the monoexponential reaction in the electrostatic complex is 3.5 x 10(5) s-1 in aqueous solution; this value is independent of protein concentration and ionic strength, but it decreases markedly as viscosity is raised by addition of glycerol or sucrose. The multiexponential reaction in the covalent complex was analyzed also in terms of the stretched exponential, exp[-(kt)n]. The best fit requires k = 6.8 x 10(4) s-1 and n = 0.56 in aqueous solution; this rate constant is independent of protein concentration and ionic strength, but it decreases slightly as viscosity is raised. Fitting of the viscosity dependence to a simple two-state kinetic model yields a rate constant of 3.0 x 10(5) s-1 for rearrangement of the electrostatic complex 3Zncyt/b5(III) from the initial docking configuration to a different, more reactive, configuration. The corresponding rate constant for rearrangement of the electrostatic complex 3Zncyt/pc(II) containing plastocyanin, determined previously, is 2.5 x 10(5) s-1. Evidently, the intracomplex reaction in both electrostatic complexes is gated by a rearrangement process.(ABSTRACT TRUNCATED AT 250 WORDS)

Gene transfer for transplantation. Prolongation of allograft survival with transforming growth factor-beta 1

OBJECTIVE

The authors tested the ability of plasmid gene transfer to express transforming growth factor-beta 1 (TGF-beta 1), prolong allograft survival, and evaluate promoter effects on gene expression.

SUMMARY BACKGROUND DATA

Delivery of immunosuppressants directly to allografts using gene transfer and gene therapy approaches may inhibit immune activation while avoiding the systemic toxicity of conventional immunosuppression. Candidate genes include soluble cytokines, which could be expressed at low levels throughout the graft while inducing a local immunosuppressive effect. Transforming growth factor-beta 1 is a soluble cytokine that has pleiotropic immunosuppressive effects.

METHODS

Cardiac grafts from syngeneic (CBA/J, H-2k) or allogenic (C57BL/6, H-2b) donors were placed into CBA/J recipients. Purified plasmid DNA-encoding murine TGF-beta 1 or beta-galactosidase (Lac Z) under the control of RSV, SV40, MMTV, or pancreatic elastase promoters was injected into grafts at surgery. The Lac Z expression was determined by histologic examination and TGF-beta 1 expression by graft survival. Cytotoxic T lymphocyte and flow cytometric analyses were performed to evaluate the immunosuppressive effects of TGF-beta 1 in vitro.

RESULTS

Plasmid DNA-encoding TGF-beta 1 prolonged survival from 12.6 +/- 1.1 days to 26.3 +/- 2.5 days (p < 0.02, Student's t test). The SV40 promoter was superior to the MMTV promoter in its ability to prolong survival. The effects of the plasmids were specific because Lac Z, antisense TGF-beta 1 inserts, or pancreatic elastase promoter did not prolong allograft survival. Histologic examination demonstrated Lac Z expression at least 14 days post-transplant in myocardial cells. Both RSV and SV40 promoters were effective in this respect, while a control null promoter was not. Toxicity testing showed that gene transfer of TGF-beta 1 did not alter survival or histology of syngeneic grafts. In addition, plasmids and purified TGF-beta 1 protein were not toxic to myoblasts in vitro. Recombinant TGF-beta 1 inhibited cytotoxic T lymphocyte generation and altered T cell surface receptor expression and subset expansion in vitro.

CONCLUSION

Gene transfer/therapy with plasmid DNA encoding TGF-beta 1 in vivo achieves immunologic effects that prolong allograft survival. Multiple promoters effectively induce plasmid expression, which is achieved in cardiac myocytes for at least 2 weeks without toxicity or adverse systemic effects. Transforming growth factor-beta 1 inhibits immune responses by different mechanisms, revealed by in vitro analysis of T cell cytolytic function, subset distribution, and receptor display.

Anti-CD48 (murine CD2 ligand) mAbs suppress cell mediated immunity in vivo

With the identification of murine CD48 as a homolog of the human CD2 ligand LFA-3 (CD58) and as a ligand itself for murine CD2, the anti-murine CD48 mAb HM48-1 was administered intravenously to investigate the role of CD48 in cell mediated immunity in vivo. Anti-CD48 mAb diminished the contact sensitivity response to the hapten trinitrophenol (TNP). mAb also inhibited in vivo priming for the subsequent generation of secondary, TNP-specific, cytotoxic T lymphocytes (CTL) in vitro. The inhibitory effect was most effective in the afferent or inductive phase of immunity for CTL, while anti-CD48 mAb was most inhibitory for the efferent or elicitative phase of contact sensitivity. Addition of anti-CD48 mAb directly to secondary CTL cultures also completely inhibited CTL generation, while addition to the lytic assay showed only minimal inhibition of CTL activity. Combining cells from mAb treated and untreated animals showed no evidence for suppressor cells. Further experiments revealed that mAb administered in vivo, as well as to culture, inhibited development of primary, alloantigen-specific CTL in vitro. Mixed lymphocyte reaction and phytohemagglutinin proliferation were partially suppressed by mAb administered in vivo or in vitro, whereas other mitogenic responses remained unaffected. Flow cytometric analysis revealed a moderate down modulation of CD48, CD3 and CD8 after treatment with anti-CD48. However, this did not represent T cell depletion since CD2, Thy-1.2 and Ig expression did not change. These results support a major unrecognized role for CD48 in diverse aspects of cell mediated immunity, affecting both CD4+ and CD8+ effector T cell function.(ABSTRACT TRUNCATED AT 250 WORDS)