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Biomedical subjects

D Oth

Publications and source records attributed to D Oth.

At least 19 recordsLinked to original sources

Prolongation of survival in retrovirally induced T cell lymphoma by dietary omega 6 fatty acid.

C57BL/Ka mice were fed diets rich in omega 3 or omega 6 polyunsaturated fatty acids and inoculated with the thymic lymphoma-inducing retrovirus RadLV. Mice receiving the omega 3 diet died significantly sooner than those receiving the omega 6 diet. Of the three known mechanisms by which fatty acids can exert antiviral activity, namely, modification of membrane fluidity, modulation of immune response, and synthesis of metabolites with antiviral activity, the first two can be eliminated in the model under study. It is therefore concluded that differences in survival are due to fatty acid metabolites with distinct antiviral activities.

Animals

Inhibition of tumor necrosis factor-alpha transcription by Epstein-Barr virus.

Tumor necrosis factor-alpha (TNF-alpha), which is produced mainly by monocyte/macrophage cells, has diverse physiological functions on lymphoid cells. Moreover, it has been shown that TNF-alpha exhibits antiviral activities. Here we report that Epstein-Barr virus (EBV), a B lymphotropic human herpes virus that interacts intimately with the immune system, exerts a strong inhibitory effect on TNF-alpha production by lipopolysaccharide-treated peripheral blood leukocytes as well as by monocytic cell lines, HL-60 and U-937. Flow cytometric analysis following staining with OKB7 monoclonal antibody showed that about 20% of cells from these monocytic lines express the CR2 antigen. Direct binding of fluorescein isothiocyanate-labeled EBV indicated that the virus binds to approximately 22% of cells of both monocytic lines. However, no virus-specific antigens were detected in the infected cells by immunofluorescence, suggesting that the infection was of the abortive type. The use of UV- or heat-inactivated EBV and inhibitory effect on TNF-alpha synthesis. These results suggest that infectious virus is necessary to obtain such an inhibitory effect. Analysis of TNF-alpha mRNA by polymerase chain reaction amplification indicated that the EBV suppressive effect is manifested at the transcriptional level. In contrast, EBV did not inhibit interleukin 1 mRNA production by these cells. These results indicate that EBV interacts directly with monocytes/macrophages to exert its immunomodulatory effect.

Antibodies, Monoclonal

Synthetic peptides corresponding to the F protein of RSV stimulate murine B and T cells but fail to confer protection.

We have previously located a major neutralization site of the fusion protein of respiratory syncytial virus (RSV) in the polypeptide region extending from amino acids Ile221 to Glu232. In this report, 8 peptides corresponding to the six major hydrophilic regions of the F1 subunit were selected to analyse their immunogenic and protective capacities as well as their ability to block the high neutralization activities of 4 monoclonal antibodies (MAbs). Only 5 of the 8 peptides tested induced specific antibodies while all induced an in vitro interleukin-2 response of splenocytes from immunized mice. Peptide 3 (Ile221-Phe237) was able to elicit neutralizing antibodies, confirming our previous hypothesis concerning the location of a neutralization site. However, immunization with the latter did not induce significant reduction of virus in lungs of BALB/c mice upon challenge, probably due to an inadequate level of circulating neutralizing antibodies. Interestingly, peptides 2 (Asn216-Glu232), 3 (Ile221-Phe237), and 5 (Ser275-Ile288) blocked in vitro neutralization by four different F1 specific MAbs. A hypothesis is proposed to explain these results.

Amino Acid Sequence

Modulation of CD4 expression on lymphoma cells transplanted to mice fed (n - 3) polyunsaturated fatty acids.

Groups of adult AKR mice were fed well defined fats controlled diet regimens. These consisted of either saturated (beef tallow: 'BT') or (n - 3) polyunsaturated (fish oil: 'FO') fatty acids supplementation to basal mix mouse food. In other groups, the basal mix was given without any fat supplement ('NF'). Six weeks or more after the initiation of these diet regimens, mice received intraperitoneal injection of histocompatible RDM-4 lymphoma cells. Ascites RDM-4 tumors were harvested approximately two weeks later, and some of their physicochemical properties were studied. It was repeatedly found that: (1) the tumor grew considerably faster in the FO-fed donor than in the BT- or NF-fed donors; (2) cell membrane fluidity, content of C20(n - 3) and of C22(n - 3) fatty acids were significantly higher in the FO groups than in both BT and NF groups, while the content of C20(n - 6) and 22:4(n - 6) fatty acids was concomitantly decreased; (3) expression of the CD4 cell surface marker was always significantly diminished in the FO groups, whereas other markers such as CD8, H2K, Thy-1 and LFA-1 were not affected. Similar results were obtained, whether fats constituted from 1% to 16% by weight of the food intake. Use of a recently selected line of the RDM-4 lymphoma, exhibiting higher CD4 marker expression, resulted in similar observations. On the other hand, CD4 expression on cells from lymphoid organs of healthy adult AKR mice was not detectably modulated by the dietary fats.

Animals

Enhancement of interleukin-2 activity by liposomes.

The present report demonstrates that liposomes increase the interleukin-2 (IL-2) dependent proliferation of cytotoxic T-lymphocyte line (CTLL) cells used for the measurement of IL-2 activity. This effect was better observed with suboptimal doses of IL-2 and low concentrations of lipids. The increased IL-2 dependent proliferation is not due to a direct effect of liposomes on CTLL cells but rather to an interaction between IL-2 and liposomes. An interaction between IL-2 and components of fetal calf serum is also demonstrated. The results indicate that liposomes may interfere with IL-2 bioassay but also show the possibility of potentiating IL-2 activity for therapeutic purposes.

Animals

Susceptibility of RDM4 lymphoma cells to LAK-mediated lysis is decreased in tumor bearers fed fish oil high fat regimen.

RDM4 lymphoma cells were grown intraperitoneally in genetically compatible AKR mice fed either regular mouse chow, or diet supplemented with either saturated fat (hydrogenated beef tallow = HBT) or unsaturated fat (fish oil = FO). It was observed that the lymphoma cells number was significantly greater in FO-fed hosts and lower in HBT-fed hosts, than in the mice fed regular chow. The tumor bearers diet did not dramatically influence the rate of DNA synthesis of RDM4 cells, as measured by [3H]thymidine uptake in culture, a few hours after harvesting from the peritoneal cavity. It was repeatedly found that FO feeding of the tumor bearers elicited an increased resistance of RDM4 cells to lysis by LAK effectors, as appraised in vitro by 51Cr release test and in vivo by the "Winn assay". Different FO percentage of the diet (16%, 8%, 4%) resulted in comparable reduction of susceptibility of RDM4 cells to lysis by LAK effectors. Lipid analysis showed that RDM4 cells grown in mice fed FO diet or HBT diet differed markedly in their fatty acid composition and that their resistance to lysis by LAK cells correlated with the quantity of oxidizable fatty acids especially of the n-6 type.

Animals

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

Lymphokine release as measurement of anti-mouse hepatitis virus type 3 (MHV3) cellular reactions in various mouse lines exhibiting differential susceptibilities to MHV3-induced paralysis.

We found that susceptibility to Murine Hepatitis Virus, type 3 (MHV3)-induced paralysis is controlled by genes of the H-2 complex. In this article, we compared MHV3 antigen specific cellular reactions, in congenic mice harbouring different H-2 genes (or gene). In a first set of experiments, paralysis susceptible (B10.A x A/J)F1, partly susceptible (B10.AQR x A/J)F1 and resistant (B10.Q x A/J)F1 hybrids were infected with live MHV3. Three weeks or more post-infection (p. i.), the spleens and peritoneal exudate (PE) cells from the mice were put into culture. Killed MHV3 was added to cultures, and antigen specific lymphokine production and utilization were measured: IL-1 production by PE cells after 24 hr in culture, IL-2 production by splenocytes after 24 hr in culture, IL-2 utilization (as appraised by splenocyte proliferation) after 96 hr in culture. No clearcut difference, resulting from genetic disparity, could be observed in the antigen-specific responses. In a second set of experiments, mice were primed with ultra-violet radiation killed MHV3. In that case, increases of IL-1 production by PE cells, of IL-2 production by splenocytes and splenocyte proliferation were always observed, compared to PE cells and splenocytes from non-primed (control) donor mice. However, in latter case, addition of MHV3 antigen to cultures did not result in augmentation of antigen specific IL-2 production and utilization. Here again, no genetic effect was observed. We conclude from these results that MHV3 infection elicited strong lymphokine responses, but that antigen-specific IL-1 and IL-2 production did not correlate with the susceptibility to MHV3-induced paralysis.

Animals

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

[Role of liposomes in the presentation of HIV envelope glycoprotein and the immune response in mice].

The role of antigen presentation in the induction of humoral as well as cell-mediated immune responses has been investigated by anchoring HIV-1 envelope glycoprotein (gp 160/120) into the phospholipidic bilayer of preformed liposomes to produce HIV-Immunosomes. HIV-Immunosomes induced high titres of HIV-specific antibodies when tested by ELISA, IFA and neutralization, whereas equal amounts of purified glycoprotein alone produced lower antibody response. Similarly, HIV-Immunosomes induced antigen-specific Interleukin-2 production and blastogenic response upon restimulation with the same antigen, in animals vaccinated with HIV-Immunosomes, whereas no secondary response was observed in animals vaccinated with equal amounts of purified gp 160/120. Taken together, these results underline the importance of antigen presentation in the establishment of an adequate immune status and show the potential of HIV-Immunosomes as vaccine against AIDS.

Animals

Interactions between lymphoid cells and a thymic stromal cell line in vitro.

In the present study, we have optimalized the adherence assay to allow monitoring of the level of contact between thymocytes and a thymic epithelial cell line, E-5, in vitro. This type of interaction is not MHC-restricted, thus is unlikely to participate in the education of thymocytes to self. It was also shown that adherence does not vary from strain to strain, except for B6lpr/lpr immunodeficient mice which showed a markedly decreased adherence. This might be caused by the high level of L3T4-, Lyt-2- thymocytes in these mice (Davignon et al., 1985), since enriched double negative cells were shown not to adhere to E-5 cells. Preliminary characterization of adhering thymocytes suggests an heterogeneous mature phenotype. These cells appear around day 16 of fetal life and increase gradually until birth to remain constant throughout life. On the basis of contact duration, two populations of adhering thymocytes exist: one spontaneously detached after 1.5 hr, refractive to further adherence and the other which adheres for up to 14 hr. Contact between lymphoid and E-5 cells was shown to induce PHA responsiveness.

Animals

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

Enhancement of antigen-specific interleukin 2 production by adding liposomes to rabies antigens for priming.

Antigen-specific IL-2 production was assessed, using splenocytes from rabies immune mice incubated for 24 h with rabies virus antigen. The antigenic material used for in vivo priming was either purified glycoprotein from rabies virus, or the inactivated virus. The time between priming, harvesting and restimulation of the splenocytes was 7 days. It was found that when antigenically inert liposomes were injected, together with antigenic material, to the prospective splenocyte donor mice, IL-2 production was enhanced. This augmentation was observed particularly when priming was performed with the inactivated rabies virus.

Animals

Interleukin-2 production in vitro: a new approach to the study of rabies vaccine immunogenicity as appraised by testing different glycoprotein presentations.

When injected as an immunosome presentation (molecules anchored to preformed liposome), rabies glycoprotein (GP) is capable of protecting animals against rabies either before or after viral infection. The presentation of the GP molecules in the correct form seems to be essential for the induction of antirabies protection. This condition must be taken in account in the making-up of a rabies subunit vaccine. In order to study the relationship between the immune responses induced by the rabies GP and its protective activity, different presentations of the GP were prepared. Purified glycoprotein molecules were associated under different physical forms: liposome-anchored, self-aggregated (rosettes) and associated with the viral lipids (virosomes). These presentations appeared different on electron microscopy. They also exhibited differences in the expression of an immunodominant epitope and in their protective activity. The non-specific immune response, as appraised by interferon production and natural cytotoxicity, was induced at a high level only by the purified viral particles. Specific immune responses (namely virus neutralizing antibody and interleukin-2 production) was induced at high levels only by the viral particle and by the liposome-anchored glycoprotein. A parallelism has previously been established between protection by glycoprotein preparations and interleukin-2 production in primed mice splenocytes. This suggests that the measure of interleukin-2 production in vitro could be used to evaluate the capability of a rabies antigen to induce a T-cell response and to confer protection.

Animals

Interleukin 2 increases protection against experimental rabies.

Vaccination with either whole inactivated rabies virus or immunosome (rabies glycoprotein anchored on liposomes) induces a high level of interleukin 2 (IL 2) production after in vitro specific stimulation of splenocytes from primed mice (9). On the contrary, infection with a live rabies virus does not specifically induce the production of IL 2: splenocytes from ill mice previously infected with wild rabies virus cannot be specifically stimulated by rabies antigens, whereas they can be non-specifically stimulated by a mitogen (Concanavalin A (Con A]. When injected in mice, exogenous IL 2 (purified rat IL 2 or human recombinant IL 2) exhibits an adjuvant effect on rabies virus vaccine or subunit vaccine tested in a pre-exposure potency test (NIH test). When injected in hamsters, according to a post-exposure potency test (infection with a wild rabies virus followed by vaccination), IL 2 has no adjuvant effect on the rabies vaccine. Nevertheless, when injected alone, IL 2 protects thirty to fifty percent of the infected animals treated (1 hour, 3 and 7 days post-infection) with 10 international units of human recombinant IL 2.

Animals

Induction, by adriamycin and mitomycin C, of modifications in lipid composition, size distribution, membrane fluidity and permeability of cultured RDM4 lymphoma cells.

Adriamycin and mitomycin C were previously found to modulate the sensitivity of lymphoma cells to lysis by certain effectors of immunity and this modulation was dependent on drug concentration. In the present studies, RDM4 lymphoma cells were treated with different concentrations of the two drugs for 24 h in culture. These treatments resulted in changes in the lipid composition, membrane fluidity, cell size distribution, and permeability to 51CrO4, Trypan blue, Acridine orange and trimethylaminodiphenylhexatriene (TMA-DPH) of the cells. Changes in some of these parameters, as a function of drug concentration, resulted in dose-response curves which were bell-like shaped, hence paradoxical similarities between non-drug-treated cells and cells treated with higher drug concentrations were observed.

Animals

Protection from mouse hepatitis virus type 3-induced acute disease by an anti-nucleoprotein monoclonal antibody. Brief report.

Fusion of MHV-3-immune splenocytes from MHV-3-resistant A/J murine strain, with NS myeloma cells produced several hybridomas. Among eight hybridoma clones, the 1E7A4H1 clone secreted kappa IgG2a apparently directed against the nucleoprotein of the MHV-3 virion. The monoclonal antibody was able to neutralize the in vitro cytopathic effect of MHV-3 on cultured L2 cells, and was detected by indirect immunofluorescence on MHV-3-infected cultured YAC cells. In addition, it conferred a significant protection against MHV-3-induced acute disease, if injected intraperitoneally to C57BL/6 mice before inoculation with MHV-3.

Animals