Biomedical subjects

A T Kozhich

Publications and source records attributed to A T Kozhich.

At least 19 recordsLinked to original sources

PubMed2000

Biphasic ocular inflammatory response to endotoxin-induced uveitis in the mouse.

OBJECTIVE: To examine the kinetics and mechanisms of endotoxin-induced uveitis in the mouse. METHODS: C3H/HeN mice were injected subcutaneously with 0.3 mg of Salmonella typhimurium lipopolysaccharide (LPS) in 0.1 mL of phosphate-buffered saline solution or phosphate-buffered saline solution alone in 3 separate experiments; mice were killed after 1, 3, 5, and 7 days. In 2 other separate experiments, mice were killed 1, 3, 6, and 24 hours after LPS injection. All eyes were collected for histological examination, immunohistochemical analyses, aqueous protein level determination, and reverse transcriptase-polymerase chain reaction for ocular interleukin (IL)1alpha, IL-6, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor messenger RNA (mRNA). Enzyme-linked immunosorbent assay was used to measure tumor necrosis factor alpha and IL-6 levels in aqueous and serum samples. RESULTS: Results were consistent for all experiments. Numbers of ocular inflammatory cells and levels of aqueous protein peaked 1 and 5 days after LPS injection. Control mice did not develop inflammation. Serum and aqueous IL-6 and ocular IL-6 mRNA levels peaked at 1 day and subsided at 3 days. However, ocular IL-1alpha, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor mRNA appeared, peaked, and subsided at 3, 5, and 7 days, respectively. Predominant infiltrating cells were neutrophils at 1 day and macrophages at 5 days. Although no ocular inflammatory cells were detected before 24 hours after LPS injection, tumor necrosis factor alpha mRNA was noticed at 1 hour, peaked at 3 hours, and disappeared at 6 hours and granulocyte-macrophage colony-stimulating factor mRNA was spotted only at 3 hours after LPS injection. CONCLUSIONS: The ocular inflammatory response to C3H/ HeN mouse endotoxin-induced uveitis is biphasic for 7 days. The first wave appears at day 1 and subsides by day 3. A second, higher peak appears at day 5. The 2 inflammatory waves are related to the kinetics of the different cytokines released in the eye. This is in contrast to the rat monophasic endotoxin-induced uveitis model, which has only one peak of intense inflammation associated with cytokine release. CLINICAL RELEVANCE: A biphasic inflammatory response associated with cytokine release lasting several days is observed in C3H/HeN mice with endotoxin-induced uveitis. Because human anterior uveitis has a tendency to be recurrent in nature, this might be a better experimental model.

Animals↗

PubMed2000

Recurrent intraocular inflammation in endotoxin-induced uveitis.

PURPOSE: Endotoxin-induced uveitis (EIU) in rats and mice peaks 24 hours after endotoxin injection and is commonly assumed to be a monophasic disease. This study examined intraocular inflammation at later time points to determine whether endotoxin injection can induce recurrent intraocular inflammation in strains of mice with high or moderate levels of susceptibility to EIU. METHODS: EIU was elicited in two mouse strains with high (C3H/HeN) and moderate (FVB/N) susceptibility, by means of intraperitoneal injections of Salmonella typhimurium endotoxin. Inflammatory cells in the anterior and posterior segments of the eye were counted by a masked observer on histologic sections of eyes from 1 to 17 days after endotoxin injection. RESULTS: A bimodal distribution of inflammatory cell infiltration was noted in eyes from C3H/HeN mice. As previously reported, inflammation peaked at 24 hours after endotoxin injection. However, a second, more pronounced peak of intraocular inflammation occurred approximately 5 days after endotoxin injection. FVB/N mice had a single peak of intraocular inflammation 4 days after injection. CONCLUSIONS: Endotoxin injection in C3H/HeN elicits recurrent intraocular inflammation. The previously unrecognized second peak of inflammation is more severe than the initial inflammatory disease. Studies on this second inflammatory peak may be useful in determining the pathogenesis of recurrent uveitis in humans.

Animals↗

PubMed1999

Blocking ICAM-1 (CD54) and LFA-1 (CD11a) inhibits experimental allergic conjunctivitis.

Cell adhesion molecules are critical for the homing and migration of leukocytes into inflamed tissues. We investigated the role of ICAM-1 and LFA-1 in a previously described experimental model of ragweed (Rw)-induced allergic conjunctivitis. SWR/J mice were treated intraperitoneally 6 and 1 h prior to topical challenge with Rw with injections of anti-ICAM-1 monoclonal antibody (mAb), anti-LFA-1 mAb, both anti-ICAM-1 and anti-LFA-mAbs, or rat IgG. Blocking ICAM-1 or LFA-1 reduced the clinical signs of allergic conjunctivitis. Treatment with anti-ICAM-1 or anti-LFA-1 mAbs also significantly inhibited cellular infiltration into the conjunctiva. The greatest inhibitory effect was achieved with the combination of antibodies against both cell adhesion molecules. Since antibodies against ICAM-1 and LFA-1 significantly inhibit the development of the clinical and histologic signs of allergic conjunctivitis, they may be useful for treating patients with ocular allergy.

Animals↗

PubMed1998

A novel murine model of allergic conjunctivitis.

Allergic conjunctivitis affects over 40 million patients per year in the United States. Here we present the first murine model that incorporates the clinical, cellular, and humoral parameters of allergic conjunctivitis, including a ragweed-induced Th2-type cytokine production by lymphocytes. SWR/J mice were immunized with short ragweed pollen in aluminum hydroxide. Ten days after immunization, allergic conjunctivitis was induced by one topical application of ragweed pollen onto the eye. Immediate response was characterized by chemosis, redness of the conjuctiva, and lid edema. Histopathology and immunohistochemistry showed dense conjunctival infiltration with polymorphonuclear leukocytes, macrophages, and CD4+ T lymphocytes. In addition, ragweed-specific IgG1 and IgE serum levels were significantly higher in immunized animals, and high levels of IL-4 and IL-5 were detected in supernatants from ragweed-activated lymphocytes. This reproducible model is a well-suited instrument for testing the pathophysiology and future therapies of allergic conjunctivitis.

Allergens↗

PubMed1997

Immunogenicity and immunopathogenicity of an autoimmune epitope are potentiated by increasing MHC binding through residue substitution.

We have previously shown that in Lewis rats, peptide 273-283 (TWEGSGVLPCV) of rat interphotoreceptor retinoid-binding protein (IRBP) serves as a "surrogate" epitope for pathogenic lymphocytes sensitized against peptide 1181-1191 (SWEGVGVVPDV) of bovine IRBP. Yet, peptide 273-283 itself causes experimental autoimmune uveoretinitis (EAU) only at 200 nmol/rat, whereas peptide 1181-1191 is pathogenic even at 0.2 nmol. This difference was attributed to the higher affinity of 1181-1191 to MHC molecules. Here we demonstrate that substitution of putative MHC binding-residues of peptide 273-283 with the corresponding ones of 1181-1191 results in increased binding to MHC and in remarkably elevated immunologic capacities. Analogs of 273-283 were synthesized, in which residues 277 and 282 were substituted with one or both the corresponding amino acids of peptide 1181-1191, V and D, respectively. The main findings were: 1) substitutions drastically increased MHC affinity, namely, 273-283(V277,D282) >> 273-283(D282) >>> 273-283; 2) the substituted analogs were much more immunogenic than the native peptide, inducing cellular responses at much lower doses; 3) the analogs were more antigenic in vitro than the native peptide; 4) the analogs were exceedingly pathogenic; peptide 273-283(V277,D282) caused disease even at 0.02 nmol/rat; and 5) the analogs were superior to the native peptide in their capacity to stimulate production of IFN-gamma by sensitized lymphocytes. Thus, enhancement of affinity of an autoimmune peptide for MHC molecules increases both immunogenicity and pathogenicity.

Amino Acid Sequence↗

PubMed1997

Blocking both E-selectin and P-selectin inhibits endotoxin-induced leukocyte infiltration into the eye.

The initial contact between leukocytes and the vascular endothelium at sites of inflammation is mediated by selectins. The purpose of this study was to investigate the role of the two selectins expressed on the vascular endothelium, E-selectin and P-selectin, in the pathogenesis of endotoxin-induced uveitis. Endotoxin-induced uveitis was produced in female C3H/HeN mice using Salmonella typhimurium endotoxin injected into one hind footpad. At the time of endotoxin injection mice were treated with an intraperitoneal injection of a monoclonal antibody against E-selectin or P-selectin, a combination of both anti-selectin antibodies, or isotype-matched control antibodies. In a second set of experiments, antibody treatment was administered 6 hr after endotoxin injection, when inflammatory cells are already entering the eye. Ocular inflammation was graded histologically by a masked observer. When administered at the time of endotoxin injection, anti-P-selectin antibody decreased ocular inflammation by 37% compared to control animals (P = 0.05). There was no statistical decrease in ocular inflammation in animals treated with anti-E-selectin antibody. The combination of anti-P-selectin and anti-E-selectin antibodies decreased infiltrating inflammatory cells by 61% (P < 0.01). When treatment was delayed until 6 hr after endotoxin injection, the combination of anti-P-selectin and anti-E-selectin antibodies again decreased ocular inflammation by 60% (P < 0.01). Immunohistochemical staining showed decreased ICAM-1 expression in the eyes of animals treated with the combination of anti-P-and anti-E-selectin antibodies. Blocking both P-selectin and E-selectin resulted in a significant decrease in endotoxin-induced intraocular inflammation.

Animals↗

PubMed1997

Effect of gallium nitrate on experimental autoimmune uveitis.

Gallium nitrate (GN) has been shown to inhibit T cell-mediated inflammatory disease. The purpose of our study was to test the effect of gallium nitrate (GN) on experimental autoimmune uveitis (EAU). Experimental autoimmune uveitis was induced in male Lewis rats immunized with retinal S-antigen. Rats received subcutaneous injections of GN or saline one day prior to immunization and 1, 4, 7, 10, 13, 16, and 19 days after immunization. Ocular inflammation was graded clinically and histologically by masked observers, and in vitro assays of cell-mediated and humoral immunity were performed. GN significantly inhibited the development of EAU graded clinically (P = 0.001) and histologically (P = 0.002). Treatment with GN also resulted in a small (30-41%) decrease in the lymphocyte responses to retinal S-Antigen and a small (12-37%) reduction in antibody production to S-antigen. These data show that GN suppresses the development of EAU, and inhibits both lymphocyte proliferative responses to antigen and antibody production.

Animals↗

PubMed1996

Intraocular inflammatory disease (uveitis) and the use of oral tolerance: a status report.

Intraocular inflammatory disease, or uveitis, is a disorder that mostly affects children and young adults. It is the cause of about 10% of the severe visual handicap in the United States. Many of the severe, sight-threatening uveitic conditions are thought to be driven by putative autoimmune mechanisms, often with high-dose oral prednisone use as treatment, along with cytotoxic agents, antimetabolites, and cyclosporine adjunctively. The feeding of the uveitogenic retinal S-Ag to rats immunized with the same antigen resulted in clinical protection. A pilot study in which two patients, one with pars planitis and the other with Behcet's disease, were fed with the retinal S-Ag resulted in these patients' immunosuppressive medication being decreased and/or stopped. The trial also provided us with information concerning dosage and expected immune responses. A randomized, masked study looking at the effect of feeding retinal antigens to uveitis patients is ongoing.

Administration, Oral↗

PubMed1994

A pathogenic autoimmune process targeted at a surrogate epitope.

Immunization with the retinal interphotoreceptor retinoid-binding protein (IRBP) induces in a variety of animals an inflammatory eye disease, experimental autoimmune uveoretinitis (EAU). We have previously shown that sequence 1181-1191 of bovine IRBP (BOV 1181-1191) is immunodominant and highly uveitogenic and immunogenic in Lewis rats. Sequence 1181-1191 of the rat IRBP (RAT 1181-1191) differs from BOV 1181-1191 by two residues, at positions 1188 and 1190, that are pivotal for the immunological activity of the bovine epitope. Here we show that, unlike its bovine homologue, RAT 1181-1191 did not induce EAU or an immune response in Lewis rats. The immunological inactivity of RAT 1181-1191 in Lewis rats is due at least in part to its poor affinity toward the antigen-presenting cells of these rats, as shown by its failure to compete with binding of BOV 1181-1191 to Lewis adherent spleen cells. Moreover, unlike all other known autologous homologues of immunopathogenic epitopes, RAT 1181-1191 was not recognized by lymphocytes sensitized against BOV 1181-1191 and failed to stimulate proliferation, uveitogenic capacity or signal transduction in these cells. These findings thus suggest that RAT 1181-1191 is not a likely target for lymphocytes sensitized against BOV 1181-1191 in the process in which these cells recognize IRBP in the rat eye and trigger the inflammatory reaction of EAU. Our data further suggest that the target for the disease-inducing lymphocytes is sequence 273-283 of the rat IRBP: (a) sequence 273-283 is highly conserved and is identical in the bovine and rat proteins; (b) determinant 273-283 is a "repeat" of 1181-1191 in the fourfold structure of IRBP and shares seven residues with BOV 1181-1191; (c) rat peptide 273-283 is recognized by lymphocytes sensitized against BOV 1181-1191 and stimulates them for proliferation and for acquisition of uveitogenicity; and (d) moreover, sequence 273-283 is superior to BOV 1181-1191 in its capacity to generate uveitogenicity in lymphocytes sensitized against this bovine peptide. The present study thus describes for the first time a system in which an autologous homologue of an immunopathogenic epitope is inactive and a "surrogate" determinant apparently serves as the target for lymphocytes sensitized against the immunopathogenic peptide.

Amino Acid Sequence↗

PubMed1994

Synthetic peptides in the determination of hepatitis A virus T-cell epitopes.

Computer search for probable T-epitopes of hepatitis A virus capsid proteins was performed using an integrated set of programs. Eight segments of the VP1, VP2, VP3 and VP4 proteins were chosen and synthesised. Five peptides previously examined as probable B-epitopes were used as well. All the peptides were tested for their ability to stimulate proliferation of lymph node T-cells primed with synthetic peptides. Almost all predicted T-epitopes affected the T-cell proliferation. None of the peptides had mitogenic activity. We demonstrated that regions 17-33 and 276-298 of VP1 are possible immunodominant promiscuous sites activating lymphocytes of all mouse haplotypes.

Amino Acid Sequence↗

PubMed1994

[Modeling antigenic determinants of the hepatitis A virus using synthetic peptides].

Monoclonal and polyclonal anti-hepatitis A (HAV) antibodies were used to search for peptides mimicking the antigenic determinants of HAV. Synthetic peptides VP1 115-139, VP1 117-139, VP1 126-139, VP2 69-99, VP2 80-99, VP3 45-57, VP3 137-150, were shown to bind the anti-HAV antibodies in ELISA. Peptides VP1 115-139, VP1 117-139, VP2 69-99 were utilized to produce the antipeptide antibodies. Mice were immunized with the free peptides or with their conjugates with ovalbumin. Only the free VP2 69-99 caused formation of HAV binding antibodies.

Amino Acid Sequence↗

PubMed1993

[2D-1H-NMR-study of the conformation of transmembrane segments of C, E, and G bacteriorhodopsin].

Conformations of synthetic peptides, analogues of the membrane spanning segments C (residues 67-106), E (128-162) and G (190-233) of bacteriorhodopsin Halobacterium halobium were studied by two-dimensional 1H-NMR spectroscopy. Peptides were solubilized in the mixture chloroform-methanol (1:1), 0.1 M LiC1O4. The spectrum resonances were assigned by means of phase-sensitive DQF-COSY, TOCSY and NOESY techniques. Interproton nuclear Overhauser effects were derived from NOESY spectra. Amide protons with slow deuterium exchange rates were determined. Analysis of the obtained data showed that segments C, E and G form right-handed alpha-helices including residues 77-101, 131-159 and 198-227, respectively.

Amino Acid Sequence↗

PubMed1993

[Solid-phase synthesis of peptides modelling the transmembrane segment of bacteriorhodopsin].

Peptides modelling transmembrane segments C, D, E and G of bacteriorhodopsin were obtained by solid phase method using the conventional Boc strategy. Protected peptides were assembled on PAM polystyrene support. Side chain protecting groups were: Tos for Arg, Bzl for Thr and Ser, cHx for Asp and Glu, Bzl(Cl2) for Tyr, For for Trp, Z(Cl) for Lys. Syntheses were performed on a modernized Beckman 990 synthesizer in the automatic mode. Double couplings by a preformed hydroxybenzotriazole ester were used for all residues. Qualitative and quantitative ninhydrine tests were used to monitor coupling efficiency. Removal of protecting groups and peptide cleavage were achieved by hydrogen fluoride, containing p-cresol and p-thiocresol as scavengers. Preparative reverse phase HPLC was used for purification. Peptide structure and homogeneity were confirmed by amino acid analysis, 1H-NMR and analytical HPLC.

Amino Acid Sequence↗

PubMed1992

Effective method for synthetic peptide immobilization that increases the sensitivity and specificity of ELISA procedures.

A procedure is described for the immobilization of synthetic peptide antigens on a plastic solid phase for performing ELISA. The use of a streptavidin-biotinylated peptide system for coating microplates with peptide antigen markedly increased both the sensitivity and the specificity compared to a standard ELISA based on synthetic peptides. The procedure was used for the detection of HIV-1-specific antibodies.

Amino Acid Sequence↗

PubMed1992

Antibodies to MHC class II peptides are present in HIV-1-positive sera.

Seventy-five per cent of sera from HIV-1-infected individuals bind to the human B-lymphoma cells bearing the major histocompatibility class II molecule in enzyme-linked immunosorbent assay (ELISA). The binding is caused by the antibodies against the class II molecule present in the serum samples which prevent the interaction of murine anti-HLA.DR monoclonal antibody with B lymphoma in FACS analysis. The three highly conserved amino acid sequences in alpha- and beta-chains of the class II molecule and three homologous fragments in HIV-1 gp120 and gp41 were identified by computer search and synthesized. Using these peptides it was demonstrated that 28-48% of HIV-positive sera contain antibodies that cross-react with the peptide of HIV-1 origin and with the peptide from the class II molecule as well.

Amino Acid Sequence↗

PubMed1992

[Study of the antigenic structure of human immunodeficiency virus using synthetic peptides].

In a search for synthetic peptide antigens fit to detect anti-HIV antibodies, a set of algorithms were used to predict the probable antigenic determinants of gag, pol, env and nef proteins of HIV-1 and HIV-2. Over forty peptides were synthesized by the solid-phase method. The reactivity of the peptide antigens was evaluated in ELISA on panels of HIV-1/2-positive sera. Application of the synthetic peptides for the early HIV diagnostics was examined.

Amino Acid Sequence↗

PubMed1992

[Mechanisms of immunodeficiency in HIV infection and ways of overcoming it].

Though antibodies against HIV-1 appearing in the course of infection are successfully used for the diagnostic purposes, their accumulation on the earlier step leads to: firstly, to the rapid generation of the immunodeficiency by different mechanisms and secondly, to inefficiency of immunotherapy. One of the causes for immunodeficiency seems to be antibodies which are induced in the HIV-infected person by the HIV peptides homologous to the MHC class II molecules by their amino acid sequences. 73% of HIV-1 positive sera are shown to react with human B-lymphoma cells expressing surface class II molecule. The binding is caused by the antibodies preventing the murine monoclonal anti-HLA.DR Ab interaction with B-lymphoma. Three amino acid sequences are identified in both alpha- and beta-chain of the HLA.DR antigen, these sequences being homologous to HIV-1 gp120 or gp42 molecules for 50 to 70%. Using synthetic peptides it was shown that HIV-1-infected persons contain antibodies which cross-react to the homologous peptides of the HIV-1 and of the MHC class II. It is supposed that such antibodies shield the class II molecule on the surface of their own antigen-presenting cell which may lead to immunodeficiency caused by the anti-HIV-1 antibody.

Acquired Immunodeficiency Syndrome↗

PubMed1991

The octapeptide corresponding to the region of the highest homology between alpha-interferon and thymosin-alpha 1 effectively competes with both cytokines for common high-affinity receptors on murine thymocytes.

The octapeptide corresponding to human interferon-alpha 2 (Hu IFN-alpha 2) sequence 131-138 has high affinity to murine thymocyte receptors (Kd = 4.2 x 10(-12) M, about 700 receptors per cell). The peptide receptor binding is inhibited by both Hu rIFN-alpha 2 (Ki = 8.6 x 10(-10) M) and thymosin-alpha 1 (TM-alpha 1) (Ki = 3 x 10(-7) M) as well as by the octapeptide homologous to the TM-alpha 1 sequence 16-23 (Ki = 4.5 x 10(-7) M). The peptide from IFN-alpha 2 (131-138) activates murine thymocyte blast transformation at a concentration of 10(-11) M in the presence of 2.5 micrograms/ml of concanavalin A.

Amino Acid Sequence↗