Biomedical subjects

R Szigeti

Publications and source records attributed to R Szigeti.

At least 19 recordsLinked to original sources

PubMed1989

Polyoma T-antigen-derived synthetic peptides induce polyoma-virus-specific macrophage migration inhibition.

Synthetic peptides, 2 derived from the sequence common to small, middle and large T-antigen, and I derived from the sequence unique for middle T, activated lymphocytes from polyoma-virus-immunized, but not from control mice, to release the lymphokine migration inhibitory factor (MIF). In contrast, purified, bacterially grown, full-length small T-antigen and a middle T-antigen mutant Py 1387T MT (lacking 37 C-terminal amino acids) did not induce lymphokine release, although they were capable of inducing an anti-polyoma TSTA response in vivo.

Animals↗

PubMed1989

Epstein-Barr virus (EBV) antigen-specific leukocyte migration inhibition in infectious mononucleosis. II. Kinetics of sensitization against five EBV-encoded nuclear proteins and the latent membrane protein.

The T cell-mediated immune response of infectious mononucleosis (IM) patients to five Epstein-Barr virus (EBV)-determined nuclear antigens, EBNAs, and to the membrane antigen associated with growth-transformed cells (latent membrane protein, LMP) was measured by the leukocyte migration inhibition (LMI) assay. Two different antigen sources were used: extracts from cells that only expressed EBNA-1, EBNA-2, or LMP after transfection with the corresponding EBV-DNA fragment, and synthetic peptides deduced from the corresponding genes. Patients in the acute phase of the disease failed to respond to EBNA-1, -5, -6, and LMP, but became responsive during convalescence. The majority of the patients responded to EBNA-2 and/or EBNA-3 in the acute phase (9/15 and 12/15, respectively). The response to EBNA-2 and/or EBNA-3 in the acute phase (9/15 and 12/15, respectively). The response to EBNA-3 disappeared more often in convalescence than the response to EBNA-2: 6 of 15 patients were negative to EBNA-2 and 12 of 15 to EBNA-3 during recovery. In addition to its value in the assessment of host sensitization to virus EBV antigens, these studies and the derived hypotheses also provide certain predictions about the predominant antigen expression in the EBV-infected host under normal and pathological conditions that can be subjected to direct experimental tests.

Adolescent↗

PubMed1988

Activation of B lymphocytes with human serum-treated zymosan.

C3 fragments fixed on zymosan particles were presented to resting human B lymphocytes. The opsonized zymosan (Ops-Z) particles induced release of leukocyte migration inhibitory factor, a slight decrease in mIgD, and a slight increase in the activation marker Blast-2. The B cells did not proceed further along the pathway of activation: they did not respond to B cell growth factor (BCGF) and Ops-Z did not synergize with other activators for BCGF response either. Thus, we found that interaction between C3 fragments and CR2 initiates the activation of human B lymphocytes, but this is limited to the early phase.

Antigens, Surface↗

PubMed1988

The effect of synthetic peptides corresponding to Fc sequences in human IgG1 on various steps in the B cell activation pathway.

The influence of synthetic peptides comprising sequences in the exposed positions of the Fc region of human IgG 1 was tested on B lymphocyte activation. CH 2 domain peptides having an inhibitory effect on antibody-dependent cellular cytotoxicity, as well as the whole Fc fragment, induced the appearance of the early signs of activation on resting B lymphocytes such as increase in cell volume and HLA-DR antigen expression or leukocyte migration inhibitory factor production. The peptides did not induce proliferation of resting B cells even when B cell growth factor (BCGF)-containing supernatants were added. Exposure to Fc fragment, however, induced a weak proliferation which was significantly enhanced by BCGF. On the other hand, both the Fc fragment and the CH 2 or CH 3 domain peptides enhanced the IgM synthesis of human blood mononuclear cells when a suboptimal dose of pokeweed mitogen was present. This effect was lost when Fc fragment or the peptides were added on the third day of culture. These results suggest that the early steps of B cell activation can be induced by Fc fragment and by small molecular weight Fc peptides, which are potential ligands of Fc receptors. The Fc fragment activates B cells to the state where they respond to BCGF, but the peptides do not possess this activity. Furthermore, both Fc fragment and Fc peptides are able to enhance the IgM synthesis, when accessory cells and the appropriate differentiating factors are present.

Amino Acid Sequence↗

PubMed1988

Immunomodulatory effect of synthetic peptides corresponding to sequences within the CH2 and CH3 domain of human IgG1.

The Fc region of IgG is known to be the source of small peptides possessing immunomodulatory function. Results are summarized showing the effect of synthetic peptides composed of surface exposed residues of C gamma 2 or C gamma 3 domains on different steps of human B lymphocyte activation cycle. Both the CH2 (289Thr-301Arg) and CH3 (407Tyr-416Arg) peptides as well as the whole Fc fragment enhanced the IgM synthesis of PWM or PMA + CaI activated lymphocytes. This effect was exerted at the early phase of B cell activation. The incubation of separated resting B cells with Fc fragments or CH2 peptides resulted in increase of cell volume and in expression of HLA-DR antigen. On the other hand, LIF production was induced both by CH2 and CH3 peptides. It was also shown that Fc peptides induce IL-1 release from monocytes. The results suggest that the CH2 and CH3 domain peptides exert their effect partly directly, by activating resting B cells, rendering the cells more susceptible to other stimuli; and moreover, by enhancing the humoral response by triggering the release of IL-1.

B-Lymphocytes↗

PubMed1988

Antibodies in human sera against the Epstein-Barr virus encoded latent membrane protein (LMP).

Antibodies reactive with the Epstein-Barr (EBV)-encoded latent membrane protein, LMP, were detected in human sera. Membrane fractions of the EBV-carrying Raji cells and a fusion protein (LMFP), that represents the carboxy part of LMP, were used as antigens. These were assayed by the reduction of the leukocyte migration inhibition (LMI) reaction. Reactivity with LMFP was detected in 10 of 14 sera from patients with Burkitt's lymphoma (BL) and in 3 of 23 sera from healthy EBV-seropositive individuals. The antibody levels were higher in the BL sera. Since the tumor cells do not express LMP, this may be due to the high virus load in the patients.

Antibodies, Viral↗

PubMed1988

Characterization of the serological response in man to the latent membrane protein and the six nuclear antigens encoded by Epstein-Barr virus.

A total of 116 sera from healthy individuals and from patients with Burkitt's lymphoma (BL), nasopharyngeal carcinoma (NPC) or rheumatoid arthritis (RA) were studied with respect to antibody responses to each of the seven known transformation-associated Epstein-Barr virus (EBV)-encoded antigens [latent membrane protein (LMP) and six nuclear proteins (EBNAs 1 to 6)]. The antibodies were detected using modified standard immunoblotting techniques. Antibodies to LMP were detected for the first time in sera from 6/27 (22%) healthy, EBV-immune individuals (seropositive for the viral capsid antigens). An increased incidence of anti-LMP antibodies was found in EBV-immune sera from patients with BL (17/24 positive; 71%), NPC (21/33; 64%), and RA (16/21; 76%). Antibodies to EBNA 1 were detected in all EBV-immune sera at a standard 1:20 dilution. Antibodies to the other EBNAs were detected in only a proportion of these sera (20 to 95%) at the same dilution. Only minor disease-associated differences in the incidence of these antibodies were observed, the most consistent being that RA sera had a higher incidence of antibodies to EBNAs 2 to 6 compared with healthy controls. Testing of the sera at a 1:100 dilution suggested that there were some disease-related differences in the titres of anti-EBNA antibodies. At this serum dilution, a reduced incidence of antibodies to EBNA 2 was seen in NPC (6/31) compared with RA (18/19) and healthy EBV-seropositives (16/26); antibodies to EBNA 3 were detected at an increased incidence in BL (8/15) and NPC (16/31) compared with control sera (7/26); antibodies to EBNA 4 were detected at increased incidence in BL (5/15) and RA (6/19) compared with control sera (1/26); and antibodies to EBNA 6 were detected at increased incidence in NPC (19/31) and RA (7/19) compared with control sera (3/26).

AIDS-Related Complex↗

PubMed1988

Studies on leukocyte migration inhibitory factor (LIF) produced by activated T and B cells.

Human T and B cells produce leukocyte migration inhibitory factor (T-LIF and B-LIF, resp.). Some properties of T-LIF and B-LIF were compared in this study. T cells were activated by PHA or by a synthetic peptide, representing the Epstein-Barr virus (EBV) nuclear antigen, EBNA1, B cells were exposed to polyclonal activators, anti-IgM or EBV. The kinetic profile of T-LIF and B-LIF released into the culture supernatants from 6 hrs until 24 hrs after activation was identical and termed "peak 2". B cells, in addition, released LIF activity after 30-60 min ("peak 1"). Molecular weight determinations by HPLC gel filtration showed that both peaks contained activity in fractions around 70 Kd. B-LIF also showed a lower molecular weight activity peak. T-LIF and B-LIF activity was equally abrogated with a rabbit anti- human LIF serum. Polymixin-B, a protein kinase C inhibitor and verapamil, a calcium channel-blocking drug, inhibited antigen-induced T-LIF and B-LIF present in "peak 2", whereas the lysosomotropic chloroquine abrogated "peak 1" early activity. We conclude that T-LIF and B-LIF are identical or very similar molecules. B cells might store presynthetized LIF in lysosomic granulae which will be degranulated very early after activation. The second peak represents de novo LIF synthesis, that requires external calcium and intact protein kinase C activity.

B-Lymphocytes↗

PubMed1987

Cellular and humoral immune responses to synthetic peptides deduced from the amino-acid sequences of Epstein-Barr virus-encoded proteins in EBV-transformed cells.

Ten synthetic peptides containing 18-22 residues deduced from the amino-acid sequences of the EBV-encoded latent-infection-associated membrane protein (LMP) and the 2 principal nuclear antigens, EBNA-1 and EBNA-2, were tested for their ability to induce lymphokine release from sensitized T-cells of EBV-seropositive donors, as measured by the leukocyte migration inhibition assay (LMI). Only one of the 10 free peptides induced EBV-specific LMI. After Sepharose-coupling, 4 additional peptides were regularly active. In parallel, the sera of the same and other donors were screened for synthetic peptide-binding antibodies, as measured by an ELISA assay. Antibodies to 9 of the 10 peptides were detected in 25-80% of EBV-antibody-positive, but not in EBV-antibody-negative sera. A comparison of the two responses indicates that the humoral immune system tends to react with more epitopes on a given protein than the cellular immune system. Furthermore, the antibody reactivity pattern to different epitopes is more variable from individual to individual than the T-cell response. Also, the epitopes detected by antibodies and sensitized T-cells are often not identical.

Amino Acid Sequence↗

PubMed1987

Stable transfection of a human lymphoma line by sub-genomic fragments of Epstein-Barr virus DNA to measure humoral and cellular immunity to the corresponding proteins.

An Epstein-Barr virus (EBV)-negative human lymphoid B-cell line, DG75, was stably transfected with recombinant selection vectors that carry a subfragment of the BamHI WYH region (nucleotides 44664 to 50628), the BamHI K fragment, or a subfragment of the EcoRI D region (nucleotides 166614 to 170149) of B95-8 EBV DNA. These fragments contain the coding exons for the EBV-determined nuclear antigens EBNA2 and EBNA1, and the membrane antigen LMP, respectively. Antigen expression of the cells was detected by immunofluorescence. EBNA2 was expressed in 80-100% of the transfected cells, in contrast to EBNA1 which was expressed in only 25%, and LMP in only about 5% of the cells. Humoral antibody responses were measured by immunofluorescence and compared to cellular immunity as determined by the leukocyte migration inhibition (LMI) technique. Extracts from transfected cell lines expressing EBNA1, EBNA2 or LMP elicited an LMI response with cells from healthy EBV-seropositive individuals whereas the extract from the parental DG75 cell line did not. The results demonstrate the value of stably transfected cell lines expressing a defined EBV antigen for the monospecific analysis of host responses to the EBV-encoded antigen complex in growth-transformed cells.

Antibody Formation↗

PubMed1987

Defective cell-mediated response to EBV-transformed B cells in a healthy individual with regular EBV antibody titers.

We have analyzed the EBV-related immune parameters of a healthy EBV-seropositive individual (ST) who has regular antibody titers but defective inhibitory capacity toward the growth of autologous EBV-infected B cells. This in vitro function reflects the EBV-specific memory because it does not occur in experiments performed with cells of seronegative individuals. An analysis of events following in vitro EBV infection showed that lymphocytes of ST behaved in some tests in the same way as those collected from seronegative individuals. These parameters were: lack of gamma-IFN production 24 hr after EBV infection; low production of soluble factors that inhibit EBV-induced B-cell proliferation; lack of generation of LCL selective cytotoxicity after repeated stimulation with autologous LCL; and high proportion of EBNA-positive cells in 7-day-old EBV-infected cultures. On the other hand, cellular memory to the virus detected by the production of IL-2 24 hr after infection, and by the production of LIF upon exposure to EBV-encoded antigens, conformed with the results obtained with seropositive individuals. T-cell-mediated inhibition of EBV-induced B-cell growth in vitro has been regarded as a corollary of in vivo control of EBV-infected B cells. However, it is absent or has a low efficiency in certain disease categories which are not accompanied by risk of B-EBV growth. Our results with a healthy individual also indicate that several mechanisms contribute to a harmless life-long virus carrier state.

Adult↗

PubMed1987

Studies on the polyoma tumor-specific transplantation antigen (TSTA): selection and characterization of TSTA-negative segregants from somatic hybrids.

Two polyoma-TSTA-negative variants were selected independently from a polyoma fibrosarcoma/Moloney lymphoma somatic hybrid, by repeated passages in polyoma-virus-preimmunized mice. One of the variants had lost all its polyoma DNA, while the other only retained a deleted piece of its integrated polyoma DNA. In contrast to the parental hybrid clone, none of the variants produced detectable amounts of T-antigens. This finding indicates that a detectable expression of the products of the polyoma virus early genome, the T-antigens, is important either directly or indirectly for the expression of TSTA.

Animals↗

PubMed1987

Activation of B lymphocytes by Epstein-Barr virus/CR2 receptor interaction.

Epstein-Barr virus (EBV) infects and transforms human B lymphocytes. The virus receptor was shown to be identical to the complement receptor CR2. The consequences of EBV/CR2 receptor interaction on B lymphocyte activation were analyzed by infection of B cells with the transforming (B95-8) and the nontransforming (P3HR1) virus strains and with UV-inactivated B95-8 virus. Similar to mitogens and antibodies against surface IgM and CR2 receptor, transforming and nontransforming EBV induced the release of leukocyte migration inhibitory factor (LIF). LIF production occurred early after infection and was not affected by irradiation of the B95-8 virus with doses of UV-light which prevented the expression of viral functions. B lymphocytes infected with UV-inactivated virus responded to T cell-derived B cell growth factors. The results demonstrate that binding of EBV to the CR2 receptor activates the B cells. Progression of the infected cells in the activation pathway required helper cell-derived factors or signals provided by the intact viral genome. The nontransforming P3HR1 virus induced a low level of RNA synthesis and increase of cell size and major histocompatibility complex class I antigen expression. Only the transforming virus induced expression of EBV nuclear antigens and cellular DNA synthesis.

Antibodies↗

PubMed1987

Analysis of Epstein-Barr virus-specific and non-specific immune functions in a patient during the development of a non-Hodgkin's lymphoma.

A 57-year-old woman who presented with a reactive non-malignant lymphadenopathy was observed subsequently during the development of a nodular centroblastic non-Hodgkin's B-cell lymphoma. The Epstein-Barr virus (EBV)-specific antibody profile and EBV-specific and non-specific cell-mediated immune functions were determined at first presentation, and at various times during progression, in order to determine whether EBV was causally involved in the lymphoma and to assess in general the patient's cell-mediated immune function. At presentation, an immunodeficient status was suggested by an EBV-specific antibody profile indicative of an activated persistent infection; high antibody titers to viral capsid antigen (VCA) and early antigens (EA), but a low level of antibodies to EBV nuclear antigen (EBNA) confirmed by lack of leukocyte migration inhibition in response to EBNA (LMI-EBNA). The number of positive cells reactive with OKIa1 monoclonal antibody was significantly depressed, as was also the natural and interferon-activated killing (NK-IAK). After emergence of the lymphoma, NK-IAK reactivity and spontaneous lymphocyte DNA synthesis augmented in parallel with an increase in the frequency of Leu-7+ blood lymphocytes. The EBV-specific cell-mediated response, reflected by the outgrowth inhibition (OI) test was abolished in parallel with a decrease in the frequency of OKT3- and OKT4-positive lymphocytes.

Cell Migration Inhibition↗

PubMed1986

Radiation leukemia virus-transformed immunocompetent T cells. II. Antigen-induced macrophage migration inhibition factor and leukocyte migration inhibition factor production.

OVA-specific T cells were immortalized by infection with radiation leukemia virus (RadLV). Some clones derived from such population were shown to exhibit helper activity. We then tested clones without such function and found among them some that secreted macrophage migration inhibition factor (MIF) and leukocyte migration inhibition factor (LIF) upon exposure to the antigen in vitro. The lymphokine-producing clones, which were Thy-1+, Ly-1+ and Ly-2-, did not secrete MIF and LIF constitutively. Like other antigen-specific T cells, the immortalized clones could not be stimulated by free soluble antigen but required macrophages for presentation and for triggering the lymphokine production. The antigen-activated clones exclusively produced MIF and LIF, but not interleukin 2 or colony-stimulating factor. They neither provided helper activity nor induced delayed-type hypersensitivity. The data suggest that the T-cell clones carry the antigen receptors and that their antigen-inducible biological function is restricted to the migration inhibitory factor production.

Animals↗

PubMed1986

Epstein-Barr virus (EBV) antigen-specific leukocyte migration inhibition (LMI) in infectious mononucleosis (IM). I. Kinetics and response to a membrane protein on EBV-transformed cells.

Cell-mediated immune response of mononucleosis (IM) patients to Epstein-Barr virus (EBV)-determined antigens was measured by the leukocyte migration inhibition (LMI) assay. Patients in the acute phase of the disease failed to respond to partially purified nuclear antigen, EBNA, or to cell extracts that contained EBNA as the predominant EBV antigen. They showed a strong specific response to cell extracts enriched in early antigen (EA) and virus capsid antigen (VCA). The LMI response to EBNA appeared in convalescence in parallel with EBNA-specific antibodies, slightly later in children than in adults. Membrane fractions of EBV-carrying, virus nonproducer Raji cells induced an EBV-specific LMI at approximately the same time. A bacterial fusion protein containing the hydrophilic part of the virus-coded membrane antigen of latently EBV-infected cells also induced an EBV-specific response that parallelled the LMI reaction elicited by the Raji membrane fraction. This is in line with our previous finding (D. Sulitzeanu et al., J. Virol. 58, 230, 1986) that this fusion protein shares an epitope with Raji cell membranes.

Adolescent↗

PubMed1986

Leukocyte migration inhibition demonstrates a human T-cell response to a membrane protein expressed in latent Epstein-Barr virus infection.

Leukocyte migration inhibition tests show that lymphocytes of Epstein-Barr virus-seropositive individuals recognize a Raji cell membrane antigen and a membrane protein encoded by Epstein-Barr virus in latently infected cells. Antiserum against the latter blocks the leukocyte migration inhibition triggered by both preparations, suggesting that the two antigens are associated with the same protein complex.

Antigens, Surface↗

PubMed1986

Leukocyte migration inhibition detects cross-reacting antigens between cells transformed by Epstein-Barr virus (EBV) and EBV-like simian viruses.

The leukocyte migration inhibition (LMI) technique was used to measure the T cell-mediated immune response of Epstein-Barr-virus (EBV)-seropositive human donors to antigens associated with B cell lines of simian origin, transformed by simian EBV-like viruses, Herpesvirus papio (HVP), H. pan, H. gorilla and H. pongo. Extracts of cell lines carrying three of the four simian viruses (from gorilla, chimpanzee and orangutan) induced a positive LMI response, whereas lines carrying baboon-derived HVP were ineffective. None of the simian virus-transformed lines elicited an LMI reaction in human EBV-seronegative individuals. Leukocytes from patients with acute infectious mononucleosis (IM) failed to respond to any of the lines transformed by EBV or the simian EBV-like viruses. Such lines express the virally encoded nuclear antigen, but have only a low level of viral cycle-associated antigens. Extracts of the EBV-carrying human cell line P3HR-1 induced with 12-O-tetradecanoylphorbol-13-acetate to express high levels of early and virus capsid antigens (EA, VCA, respectively) however, elicited a strong response with leukocytes from patients with acute IM. During convalescence, IM patients became responsive to EBV, H. gorilla-, H. pan- and H. pongo-transformed lines, indicating that the LMI reaction induced by these simian virus-transformed lines was directed against the antigens expressed in immortalized cells rather than against antigens of the lytic cycle. It is highly probable that this reaction reflects a cross-recognition of the nuclear antigens associated with these four transforming viruses (excluding H. papio) at the level of human T cells.

Antibodies, Viral↗