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J Menezes

Publications and source records attributed to J Menezes.

At least 73 records · Page 4Linked to original sources
PubMed1991

Role of Vicia villosa-adherent CD8+ T cells in the immune response to Epstein-Barr virus.

Epstein-Barr virus (EBV) is a lymphotropic human herpesvirus which is also a polyclonal B-cell activator. We show here that Vicia villosa-adherent CD8+ T (VV-T) cells, which have a contrasuppressive activity, play an important role in the B-cell response to EBV and that T-helper cells are not required for antibody production against EBV particles. We have examined this activity by measuring anti-EBV IgM antibody production by B cells in vitro in the presence and the absence of both T-helper and VV-T cells. The presence or absence of T-helper cells did not affect antibody production. Our results suggest that the antigen-presenting activity of VV-T cells was virus specific, while the contrasuppressive activity was not. Control experiments carried out in parallel using human cytomegalovirus (CMV) produced similar results also for CMV-specific IgM production. Taken together, our data lead us to hypothesize that VV-T cells might also play other roles in EBV infections: on the one hand, by presenting EBV to B cells, VV-T cells could contribute to the spread of viral infection of B lymphocytes, as the latter are the exclusive targets for EBV immortalization within the immune system; on the other hand, by inhibiting the effect of T-suppressor cells on T-helper cells, VV-T cells could indirectly help the latter maintain their lymphokine producing activity, especially interleukin-2 and interferon-gamma production, which in turn could directly or indirectly (i.e., by stimulating natural killer and T cells) contribute to control of the EBV infection.

Antibodies, Viral↗
PubMed1991

Epstein-Barr virus (EBV) glycoprotein gp350 expressed on transfected cells resistant to natural killer cell activity serves as a target antigen for EBV-specific antibody-dependent cellular cytotoxicity.

Cell surface-associated viral glycoproteins are thought to play a major role as target antigens in cellular cytotoxicity and antiviral immunosurveillance. One such glycoprotein is the Epstein-Barr virus (EBV)-encoded glycoprotein 350 (gp350), which is expressed on both virion envelope and EBV producer cells and carries the virus attachment protein moiety. Although it is known that some antibodies to gp350 can neutralize the virus, the role of this glycoprotein in EBV-specific cellular cytotoxicity is not yet clear. We describe here a study in which we successfully used a new approach to demonstrate that gp350 is a target antigen for EBV-specific antibody-dependent cellular cytotoxicity (ADCC). Transfection of gp350-negative cells resistant to natural killer (NK) cell activity (i.e., Raji) with a recombinant vector (pZIP-MA) containing the gene encoding the EBV-gp350 and the neomycin resistance gene enabled us to isolate cell clones with a stable and strong expression of gp350 on their surface membranes. ADCC determined by using two clones clearly demonstrated that gp350 is the target of the EBV ADCC. Interestingly, this ADCC was comparable to that obtained against the EBV-superinfected (coated) Raji cell expressing the same percentage of gp350 positivity as the two clones. No cytotoxic activity was detected against either nontransfected (gp350-negative) Raji cells or cells transfected with the vector [pZIP-neo-SV(X)1] lacking the gp350 gene. In addition to demonstrating that gp350 is a target molecule for EBV-specific ADCC, our approach in using NK-resistant transfectants provides a lead for probing the role of cell surface-associated viral antigens in specific cellular killing and immunosurveillance.

Antibodies, Monoclonal↗
PubMed1991

Human herpesvirus 6 induces interleukin-1 beta and tumor necrosis factor alpha, but not interleukin-6, in peripheral blood mononuclear cell cultures.

The human herpesvirus 6 (HHV-6) is known to interact intimately with cells of the immune system. Here we report that HHV-6 is a potent inducer of interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha (TNF-alpha) in cultures of peripheral blood mononuclear cells. In contradistinction, HHV-6 has no effect on IL-6 synthesis. Maximal IL-1 beta and TNF-alpha gene transcription, as detected by polymerase chain reaction amplification analysis, is observed at 12 and 6 h postinfection, respectively. Release of IL-1 beta and TNF-alpha into the culture supernatants peaked at 24 h and gradually decreased with time. Heat-inactivated virus was unable to stimulate IL-1 beta and TNF-alpha syntheses, whereas UV-irradiated virus retained the full monokine-inducing potential of the native particle. Preincubation of viral preparation with neutralizing anti-HHV-6 antibody resulted in the abrogation of this cytokine-inducing effect, whereas treatment of cells with phosphonoacetic acid (an inhibitor of viral DNA polymerase activity) had no effect on the ability of the virus to stimulate monokine release. These results indicate that HHV-6 can exert a strong immunomodulatory effect by stimulating the cells of myeloid lineage to produce these cytokines.

Base Sequence↗
PubMed1990

Comparative study of herpes simplex virus receptor expression on human lymphoid cells.

Lymphocytes represent key cells of the immune system and play an important role against viral infections. However, the expression and quantification of virus receptors on lymphoid cells have, in most cases, not been studied. We report here a study of the expression of herpes simplex virus (HSV) receptors by different human lymphoid cell types. Using flow cytometry and fluorescein isothiocyanate-conjugated HSV1 (F-HSV1) we analyzed virus binding to fresh and mitogen-stimulated B and T lymphocytes and established monoclonal lymphoid cell lines (LCL). The study included analysis of (a) virus binding in relation to cell size; (b) specificity of the virus binding using virus-specific monoclonal and polyclonal antibodies as well as heparin, an inhibitor of HSV attachment to cells; and (c) HSV1 receptor density on various targets. The results show that HSV1 binds to all the cell types tested, including some cell lines which were found negative for virus replication. This binding was specifically inhibited with either purified human anti-HSV1 F(ab)'2 or heparin. Stimulation of peripheral blood leukocytes with phytohemagglutinin resulted in a remarkable increase of receptor density on T lymphocytes. B cells showed an increase in receptor density only following PBL stimulation with pokeweed mitogen. The density of HSV1 receptor on fresh T and B lymphocytes is significantly lower than that on mitogen-stimulated cells and LCL; this indicates that mitogenic activation or transformation of lymphocytes leads to an upregulation of the expression of cellular receptors for HSV1 and may in turn explain why HSV replicates only in stimulated and not in resting fresh lymphocytes.

Antibodies, Monoclonal↗
PubMed1990

The effect of indomethacin, prostaglandin E2 and interferon on the multiplication of herpes simplex virus type 1 in human lymphoid cells.

The control of latency and reactivation of herpesvirus (HSV) infection is poorly understood. The activation of latent HSV is usually associated with a local or systemic rise in prostaglandins (PGs). It is possible that PGs may act indirectly by suppressing the inhibitory effect of interferon (IFN) on HSV replication. IFN has also been shown to decrease the number of herpetic recurrences and to speed up the healing of lesions. We investigated the effect of indomethacin (IND: a non-steroid anti-inflammatory drug which inhibits PGE2), PGE2, IFN-alpha and various combinations thereof on HSV-1 replication in established human lymphoid cells: Raji and Raji-HSV (a persistently infected subpopulation of Raji cells which continuously produces HSV-1 particles). We found that, in contrast to exogenous PGE2, IND suppressed HSV-1 replication in both cell lines. Attempts to overcome the inhibitory effect of IND by addition of PGE2 were unsuccessful. IFN also inhibited HSV-1 replication when a low multiplicity of infection was used. Moreover, the inhibition of HSV-1 multiplication was more marked in cultures treated with IFN in the presence of IND. PGE2 did not decrease or reverse the protective effect of IFN. Our results also suggest that the effects of PGE2, IND and IFN on HSV-1 replication depend on the multiplicity of infection. Further, the present observations together with previously published data would indicate that the inhibitory effect of IND on HSV-1 replication is independent of cell type or origin, while the enhancing effect of PGE2 on virus growth may depend on these factors.

Animals↗
PubMed1990

Peripheral blood lymphocytes resistant to Epstein-Barr virus immortalization manifest high natural killer (NK) type activity against NK-resistant target cells.

Epstein-Barr virus (EBV) readily immortalizes human peripheral blood lymphocytes (PBL) in vitro. We found recently that PBL from two EBV-seropositive healthy adults were exceptionally resistant to immortalization by EBV. In contrast to PBL from other EBV-seropositive donors sensitive to immortalization by EBV (S-PBL), the "resistant" PBL (R-PBL) respond to EBV infection with an early interleukin-2 (IL-2) synthesis and high interferon gamma (IFN gamma) production. In order to determine whether these differences in cytokine responses between R-PBL and S-PBL could be associated with a detectable difference in lymphocyte cytotoxicity, we compared the natural killer (NK) activity of R-PBL and S-PBL effectors by using both NK-sensitive (i.e. K562) and NK-resistant (i.e. Raji) targets. We found that, while effectors from EBV-infected R-PBL and S-PBL cultures exhibited comparable NK activity against the K562 targets, they differed remarkably in their cytolytic activity against Raji cells. At days 3 and 5 of culture, effectors from EBV-infected R-PBL showed a significantly higher lytic activity against Raji targets, whereas S-PBL did not. Culture of EBV-infected R-PBL and S-PBL effectors in the presence of recombinant IL-2 (rIL-2) for 5 days resulted in increases of their lytic activity against Raji cells, whereas pretreatment of these effectors with recombinant IFN gamma (rIFN gamma) was found to increase only R-PBL cytotoxicity. These results suggest that the resistance of R-PBL to EBV immortalization could be associated with a lymphokine-mediated early cellular cytotoxic response of the NK/LAK (lymphokine-activated killer cell) type against EBV-infected cells.

Adult↗
PubMed1990

Epstein-Barr virus receptor expression on human CD8+ (cytotoxic/suppressor) T lymphocytes.

In 1977 we showed that cells of a human lymphocytic leukaemia-derived T line (Molt-4) have receptors for Epstein-Barr virus (EBV). More recently, EBV-positive human T cell lymphomas have been recognized and human T cell lines containing the EBV genome have been established in vitro. To understand better the interaction of EBV with T cells, we decided to determine first whether human peripheral blood T lymphocytes express receptors for EBV. Using flow cytometry we examined the binding of both lymphocyte-transforming (B95-8) and non-transforming (P3HR-1) strains of EBV to T lymphocyte subpopulations, using a double labelling technique with T cell-specific phycoerythrinated monoclonal antibodies (Leu 2a) and fluoresceinated viral preparation. Our results suggest that, in general, about 50% of the CD8+ (or suppressor/cytotoxic) T cell subpopulation from both EBV-seropositive and -seronegative individuals can bind EBV. EBV receptor expression on these T cells was about 10 and 51 times less than that on Molt-4 and Raji (an EBV receptor-positive B cell line) cells, respectively. The specificity of this binding was demonstrated by the inhibition of attachment of viral preparations preincubated with a monoclonal antibody directed against the viral ligand (gp240/350), and by preincubating these target T cells with unlabelled virus. We were unable to detect EBV-induced antigens in infected T cells, suggesting that, as in Molt-4 cells, virus internalization may not occur in fresh T cells and/or that the virus receptor may not be completely functional. We were also unable to detect C3d (or CR2) receptors on these T cells, or to inhibit virus attachment by treating the targets with an anti-CR2 monoclonal antibody (OKB7), suggesting that the EBV receptor on CD8+ peripheral blood lymphocytes is different from that on B cells.

Cell Line↗
PubMed1990

Effect of monoclonal antibodies to Epstein-Barr virus envelope glycoproteins on Epstein-Barr virus neutralization and binding to target cell receptors. A comparative analysis.

Viral envelope glycoproteins are important in antiviral immunity; however, their precise role in both generating virus-neutralizing antibodies as well as in viral binding to target cell receptors remains largely unexplored. We studied nine monoclonal antibodies (MoAbs) to Epstein-Barr virus (EBV) envelope glycoproteins in order to define the role(s) of their respective epitopes in both EBV neutralization and binding to cellular receptors. Only four MoAbs neutralized EBV infectivity, one requiring complement, and only 1 of these 4 did inhibit EBV binding to target cell receptors. Our results suggest that (1) the epitopes recognized by a majority of these MoAbs play no role in viral neutralization and (2) that the majority of epitopes recognized by the neutralizing antibodies play no role in EBV binding to target cell receptors. This and previous studies would also suggest that only one epitope is involved in EBV binding to its receptor or that, until now, we were able to identify only one EBV-neutralizing MoAb (i.e., 72A1) which is specific for the receptor-binding viral epitope. It is probable that the epitope recognized by 72A1 MoAb is the only glycoprotein domain with a dual role, i.e., in EBV neutralization and binding to target cell receptors.

Antibodies, Monoclonal↗
PubMed1989

Differential interleukin-2 and interferon-gamma production by human lymphocyte cultures exceptionally resistant to Epstein-Barr virus immortalization.

Epstein-Barr virus (EBV) readily immortalizes human peripheral blood lymphocytes (PBL) in vitro. However, during the past several years, we found that PBL from two exceptional EBV-seropositive healthy adult individuals were refractory to immortalization by EBV. We report here a study aimed at learning about the immunobiological features which differentiate these EBV-resistant (R) PBL from others which are susceptible (S) to EBV immortalization. Results of this investigation indicate that: (a) Following EBV infection, R-PBL produced significantly higher amounts of interferon gamma (IFN-gamma) than S-PBL. There were however no differences in regard to interferon alpha production between these two types (R and S) of EBV-infected cultures. (b) R-PBL had a maximal interleukin-2 (IL-2) production by S-PBL occurred at least 48 hr later, i.e., at Day 7. (c) The percentage of non-B cells expressing the IL-2 receptor was also higher in EBV-infected R-PBL than S-PBL. (d) In contrast, expression of IL-2 receptors after EBV infection was higher on B cells from S-PBL than on B cells from R-PBL. Interestingly, no differences were noted in regard to IL-2 receptor expression between R-PBL and S-PBL treated with mitogens (i.e., phytohemagglutinin and pokeweed mitogen). (e) Finally, using anti-IL-2 and anti-IFN-gamma antibodies in EBV-infected R-PBL cultures, we were able to obtain EBV-induced immortalization of these cultures. Taken together, these results suggest that an early IL-2 synthesis and high IFN-gamma production by EBV-infected PBL play an important role against lymphocyte immortalization by EBV.

Antigen-Antibody Reactions↗
PubMed1989

Interleukin-2 induced killer cell activity against Epstein-Barr virus-immortalized human B cells.

Interleukin-2 (IL-2) activated killer (LAK) cells, generated in vitro by treating peripheral blood lymphocytes (PBL) with human IL-2, are able to lyse a wide variety of target cells without restriction by major histocompatibility complex (MHC) molecules. Earlier observations from this and other laboratories indicated that patients with Epstein-Barr virus (EBV) induced infectious mononucleosis, a self-limiting viral disease, have high EBV-non-specific natural killer (NK) cell activity. Since the effect of LAK cells on EBV-immortalized B lymphocytes has not yet been studied, we decided to investigate LAK cell activity against autologous and heterologous B lymphocytes immortalized in vitro by EBV and other EBV genome-positive and -negative targets of malignant origin. LAK activity was determined by 51Chromium release assay. The results obtained show that LAK activity was not specific for EBV and was not MHC-restricted. Results of experiments using NK cell reactive monoclonal antibodies suggest that the cytotoxicity is due predominantly to activated NK cells. Our observations suggest that LAK cells may be very effective for immunotherapy in patients with chronic or progressive EBV infections and EBV-induced lymphoproliferative diseases.

Antibodies, Monoclonal↗
PubMed1988

Infection of a murine T-cell line with a retrovirus carrying c-myc decreases the interleukin-2 cell dependence by a nonautocrine mechanism.

A murine interleukin-2 (IL-2)-dependent T-cell line, CTLL-2, was infected with a retrovirus carrying the mouse c-myc cDNA and the Tn-5 neogene. Transduced cells were selected in the presence of Geneticin sulfate (G418); these cells were shown to express both the endogenous and the transduced c-myc genes. The IL-2 requirement of these cells was then found to be significantly reduced. The cells did not express IL-2 mRNA nor did they produce an activity mitogenic for CTLL-2 cells. This suggests that the reduction of IL-2 dependence observed following retroviral transduction of c-myc is caused by a nonautocrine mechanism.

Animals↗
PubMed1988

Tac expression induced by Epstein-Barr virus is restricted on non-transformable B lymphocytes.

During the course of a comparative study dealing with the immortalization of lymphocytes from a large number of normal healthy donors, we found that B cells of two of these individuals could not be immortalized by Epstein-Barr virus (EBV) under the standard conditions. The expression of the Tac antigen on the membrane of EBV-infected B cells from these two donors was compared with that of B cells from EBV immortalization-susceptible ones. The method used was two-colour immunofluorescence cytofluorometer analysis. We found that the Tac antigen expression was significantly and repeatedly reduced in the case of the two immortalization-resistant donors. This difference might be related to a genetic control of the resistance to EBV-immortalization.

B-Lymphocytes↗
PubMed1988

Differences in Epstein-Barr virus (EBV) receptors expression on various human lymphoid targets and their significance to EBV-cell interaction.

This study was aimed at quantitating, by means of fluorescence-activated cell sorter (FACS), EBV binding to different types of target cells, and at learning about a possible relation between EBV receptor density and the fate of cell-surface bound virus. We used fluoresceinated virus preparations of two strains of EBV (B95-8: lymphocyte transforming strain; P3HR-1: non-transforming strain) to analyze quantitatively the expression and density of EBV receptors on different human lymphoid cell lines and on B lymphocytes from both EBV-seropositive and -seronegative donors. FACS analysis was also used as a tool to approximate the cell surface area of the different lymphoid cells examined. Our results indicate that: (a) after accounting for the difference in cell surface dimensios, the fluorescence intensity of EBV-bound Raji (a B line) cells was three to four times higher per unit area than that of EBV-bound fresh B lymphocytes from an EBV-seropositive donor; (b) Molt-4 (a T line) cells bound about 21-fold less P3HR-1 EBV and 6-fold less B95-8 EBV than Raji cells per unit area; (c) B lymphocytes from EBV-seronegative adult donors bound only about one third as much virus as B cells from seropositive individuals; (d) two B lymphocyte sub-populations can be identified in the peripheral blood in regard to their ability to bind EBV, regardless of the EBV antibody status of the donor; (e) the EBV receptor on Molt-4 cells appears structurally different from the one found on Raji cells since EBV binding to Molt-4 cells was not blocked by a monoclonal antibody (OKB7) specific to the complement receptor (CR2). Further, in contrast to Raji cells, Molt-4 expressed a differential binding activity for each of the two EBV strains used. Taken together, the important differences observed in regard to EBV attachment to various targets also appear to relate to the fate of cell-surface bound virus: i.e., virus penetration might be determined, at least in part, by the density of EBV receptors on the target cell surface; thus the receptor density may play a major role in viral infection.

Antibodies, Monoclonal↗
PubMed1988

Human gamma interferon induction by staphylococcal protein A: effector cells, kinetics and the effect of prostaglandin, indomethacin, ibuprofen and aspirin.

Soluble staphylococcal protein A (SpA) induces the synthesis of gamma-interferon (gamma-IFN) by human peripheral blood lymphocytes (PBL). To investigate the kinetics of this gamma-IFN induction and the effector cells involved, we used a highly purified SpA preparation, PBL from healthy volunteers, and a CPE-inhibition gamma-IFN assay with Sindbis virus in human fibroblasts. The production of SpA-induced gamma-IFN (SpA-gamma-IFN) peaked 48 h after the addition of SpA to cultures of PBL and decreased after 72 h. Subpopulations of PBL were purified by depletion using specific monoclonal antibodies and complement; CD4+ or OKT4+ (T4: helper/inducer) cells were able to produce SpA-gamma-IFN in the absence of CD8+ or OKT8+ (T8: suppressor/cytotoxic) or B-cells. PBL pre-incubated with SpA for more than 72 h inhibited gamma-IFN production by autologous fresh PBL; this inhibition segregated with the T8 subpopulation and was not due to cytotoxicity. SpA-gamma-IFN titers increased markedly when CD3+ or OKT3+ (T3) or T4 cells were incubated with a small number (2-10%) of adherent monocytes, whereas larger numbers (greater than 20%) decreased the yield of SpA-gamma-IFN. This decreased yield was probably mediated by prostaglandin E2 (PGE2) of monocyte origin: the presence of PGE2 was demonstrable in these cultures by radioimmunoassay, and the addition of indomethacin reversed the inhibitory effect of large numbers of monocytes; further, treatment of T-cells with exogenous PGE2 also led to an inhibition of SpA-gamma-IFN. Ibuprofen and aspirin also had an effect comparable to indomethacin on SpA-gamma-IFN production. These observations indicate that the production of SpA-gamma-IFN is by T4 lymphocytes, is enhanced by limited numbers of accessory cells (monocytes), and is also regulated by T8 cells via monocyte PGE2.

Aspirin↗
PubMed1987

IgG from Epstein-Barr virus infectious mononucleosis patients inhibits interleukin-2 production.

Patients with Epstein-Barr virus (EBV)-associated dissorders usually demonstrate evidence of immunosupression during active disease. Sera of some patients with EBV-induced infectious mononucleosis (IM), contain an IgG-blocking factor (IM-IgG) which inhibits in vitro cell-mediated immune responses and which we postulate plays an important role in viral immunosuppression. We had shown earlier that Isoprinosine (an immunostimulator) has a counterinhibitory effect on this IM-IgG activity. Here we describe evidence showing for the first time that the immunosuppressive activity of IM-IgG is aimed at inhibition of interleukin-2 (IL-2) synthesis and does not affect IL-2 receptors.

Binding, Competitive↗
PubMed1987

Epstein-Barr virus immunosuppression: II. Generation of nonspecific suppressor T lymphocytes in vitro.

We have previously shown that antigen-specific T-suppressor (Ts) cells can be generated in vitro by antigens of Epstein-Barr virus (EBV). However, patients with EBV-associated disorders and particularly those with EBV-induced infectious mononucleosis characteristically have nonspecific Ts cells in their peripheral circulation. To explore this apparent paradox, we have now examined the interaction of EBV antigens with either an unrelated antigen (tuberculo-protein-PPD) or a T-cell mitogen (phytohemagglutinin-PHA) in the in vitro generation of Ts cells. Our findings are: (1) the presence of unrelated antigens results in the generation of nonspecific Ts cells in a system wherein an EBV antigen (in excess) alone otherwise induces only antigen-specific Ts cells; (2) the unrelated antigen may be present in a wide range of concentrations and (3) can contribute to nonspecific Ts cell generation when added as long as 2 days after initiation of induction by EBV antigen; (4) the unrelated antigen must be recognized by the sensitized lymphocytes in order for nonspecific Ts cells to be induced; and most interestingly (5) when a second, immunologically different, EBV antigen is substituted for the unrelated antigen (PPD), again nonspecific Ts cells are induced in this system. We propose that the presence of unrelated (or multiple) antigens, in addition to the antigen-specific Ts cell-inducing antigen, contributes to the generation of nonspecific Ts cells in vivo, and that this phenomenon may be important in infections, malignancies, and immunodeficiency states.

Antibodies, Monoclonal↗