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At least 37 records · Page 2Linked to original sources
PubMed1991

Vaccination with Legionella pneumophila membranes induces cell-mediated and protective immunity in a guinea pig model of Legionnaires' disease. Protective immunity independent of the major secretory protein of Legionella pneumophila.

We have examined the capacity of Legionella pneumophila membranes to induce cell-mediated immune responses and protective immunity in a guinea pig model of Legionnaires' disease. Guinea pigs immunized by aerosol with L. pneumophila membranes developed strong cell-mediated immune responses to L. pneumophila membranes as demonstrated by cutaneous delayed-type hypersensitivity and in vitro splenic lymphocyte proliferation. Guinea pigs immunized by aerosol or by subcutaneous inoculation with L. pneumophila membranes developed strong protective immunity against lethal aerosol challenge with L. pneumophila. Overall, in six independent experiments, 39 of 49 (80%) guinea pigs immunized with L. pneumophila membranes survived challenge compared with 2 of 40 (5%) sham-immunized controls (P = 2 x 10(-13). In contrast, guinea pigs immunized by aerosol with formalin-killed L. pneumophila did not develop either a strong cell-mediated immune response to L. pneumophila antigens or protective immunity to lethal aerosol challenge. The capacity of L. pneumophila membranes to induce protective immunity was independent of the major secretory protein of L. pneumophila, which we previously demonstrated is an immunoprotective molecule. Purified L. pneumophila membranes did not contain detectable major secretory protein (MSP) on immunoblots; immunization of guinea pigs with L. pneumophila membranes did not induce anti-MSP antibody; and guinea pigs developed comparable protective immunity after immunization with membranes from either an L. pneumophila strain that secretes the major secretory protein or an isogenic mutant that does not. This study demonstrates that (a) immunization with L. pneumophila membranes but not formalin-killed L. pneumophila induces strong cell-mediated immune responses and protective immunity, (b) L. pneumophila membranes contain immunoprotective molecules distinct from the major secretory protein of L. pneumophila, and (c) L. pneumophila membranes have potential as a vaccine against Legionnaires' disease.

Aerosols↗
PubMed1990

Cells involved in the immune response. XXXVII. Antigen-specific suppressor cells, capable of secreting an antigen-specific suppressor factor, migrate from the thymus to the spleen following primary immunization.

The splenic mononuclear cells (MNC) of rabbits 7-14 and 30-48 days following primary intravenous immunization with sheep erythrocytes generated large numbers of antibody-secreting or plaque-forming cells (PFC) in secondary immune responses induced in vitro, whereas the splenic MNC obtained from rabbits 18-30 days following primary intravenous immunization generated poor secondary immune responses (few PFC) in vitro. However, these latter splenic MNC depleted of T cells consistently generated many PFC in the secondary immune response in vitro. Furthermore, the splenic MNC of rabbits thymectomized prior to day 3 following primary intravenous immunization also generated good secondary immune responses in vitro, irrespective of the time of killing post-immunization, whereas the splenic MNC of rabbits thymectomized after day 7 following primary immunization generated poor secondary immune responses in vitro. These results indicate that the depressed ability of the splenic MNC, obtained from rabbits killed between days 18 and 30 post-primary immunization, to generate significant secondary immune responses in vitro is due to suppressor T cells. The suppressor cells are referred to as immune spleen suppressor cells or ISSC. It was demonstrated that the suppression by the ISSC is antigen-specific and that the ISSC secrete an antigen-specific suppressor factor referred to as immune spleen suppressor factor or ISSF. It is concluded that the ISSC are generated in the thymus within a few days following primary immunization, that they migrate to and infiltrate the spleen between days 3 and 7 following primary immunization, and that they suppress or down-regulate further antibody synthesis via the secretion, locally of ISSF.

Animals↗
PubMed1992

Defence mechanisms and immune evasion in the interplay between the humane immune system and Plasmodium falciparum.

Immunity to P. falciparum malaria is developed as a result of long term exposure to the parasite and depends on immunological memory. The key directors in immune recognition and regulation of the immunological responses are the T-cells. It seems reasonable to propose that immunity is acquired when a critical mass of T-cells, recognizing relevant malaria antigens, has been developed. These T-cells mediate immunity by regulating macrophage and B-cell activity, but they may also act directly as cytotoxic cells on infected hepatocytes and through production of parasite-toxic cytokines. The potential immune effector mechanisms against P. falciparum are many. The relative importance of each in protection is unknown and protection seems to be mediated through different mechanisms according to the degree of exposure to malaria and the pattern of malaria transmission. Since immunity to malaria is not an absolute phenomenon, many effector mechanisms are probably working together in (partially) protected individuals. Immunity to P. falciparum is acquired after years of exposure to the parasite and several disease episodes. The protracted course to clinical immunity indicates that the parasite interfere with development of immunity. Several mechanisms seem to be operating. 1) Induction of the immune response to some macromolecules is avoided because the parasites are living inside host cells during part of their life cycle, and the reaction to other molecules is apparently avoided by mimicry of host molecules. 2) Immune recognition is hampered by the extraordinary diversity of antigen phenotypes in the parasite population. 3) Immune regulation is obstructed by immune suppression. During P. falciparum malaria such suppression is characterized by a profoundly diminished in vitro proliferative response to malaria antigens, which probably is precipitated by defects in the early events of T-cell activation and inhibition of IL-2 function elucidated, but soluble factors secreted either by the parasites, or by host cells as a result of exposure to the parasite, seem to be involved. 4) Immune effector mechanisms in the liver and the spleen are avoided by sequestration of the mature parasites to the vascular endothelium. The interplay between the human defence system and the malaria parasite governs the symptomatology, the pathology and the development of immunity to the disease. These interactions are extremely complex, and only partly understood. Figure 1 summarizes my view on how these interactions could explain the characteristics of acquired immunity to P. falciparum.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Immunity to sexual stages of human malaria parasites: immune modulation during natural infections, antigenic determinants, and the induction of transmission-blocking immunity.

Four antigens of Plasmodium falciparum have so far been identified as targets of transmission-blocking antibodies; three of them (Pfs 230, 48/45) are detectable in gametocytes and expressed on gametes, the fourth (Pfs 25) appears only after fertilization. Epitope analyses of each antigen were made with competitive immunoassays, and the extent of antigenic diversity determined amongst numerous isolates of P. falciparum. There was minimal variation within one of the two epitopes on Pfs 230 both of which induce transmission-blocking antibodies. The epitopes on Pfs 25 to which blocking monoclonal antibodies respond showed a variability amongst different isolates by immunofluorescence which was unexpected in view of sequence data on the molecule. Five epitope regions have been identified on Pfs 48/45 and antibodies to them interact in a complex manner. Antigenic diversity affecting these epitopes was minimal. In P. vivax malaria much greater polymorphism was seen amongst gamete surface antigens. Natural P. falciparum infections induce antibody responses to gametocyte/gamete surface antigens that will suppress infectivity to mosquitoes but these responses may involve reactivity with any of a series of different epitopes, interactions between antibodies, and may be sequential. In P. vivax infections antibody to the sexual stage antigens may suppress or enhance transmission depending on the antibody level. Cytokine production induced by sexual stage antigens may also modulate transmission, by rendering gametocytes non-infective. Experimental studies showed marked MHC-restriction of immune responses to gamete antigens (but not to the Pfs 25 zygote antigen); the evidence from studies in humans is less convincing. Antibody responses to the sexual stage antigens seem to be more frequent in persons who have experienced only one or a few attacks of malaria as opposed to those who have been exposed frequently. Some form of down-regulation may therefore be occurring.

Animals↗
PubMed1992

Cotton rats previously immunized with a chimeric RSV FG glycoprotein develop enhanced pulmonary pathology when infected with RSV, a phenomenon not encountered following immunization with vaccinia--RSV recombinants or RSV.

In studies conducted in the 1960s, children previously immunized with a formalin-inactivated respiratory syncytial virus (RSV) vaccine (FI-RSV) developed a greater incidence and severity of pulmonary disease during subsequent natural RSV infection than did controls. It was previously shown that cotton rats immunized with FI-RSV or immunoaffinity-purified fusion (F) glycoprotein developed enhanced pulmonary histopathology following intranasal challenge with RSV. In the present studies, various forms of immunization, including parenteral inoculation of an immunoaffinity-purified F glycoprotein or a chimeric FG glycoprotein produced in insect cells using a baculovirus vector (Bac-FG), intradermal infection with a vaccinia-F recombinant (Vac-F) or intranasal infection with an adenovirus-F recombinant (Ad-F) or RSV, were compared for immunogenicity, efficacy and ability to alter the host so that enhanced pulmonary histopathology developed during RSV infection 3 months after immunization. Immunization of cotton rats with F glycoprotein, Bac-FG, Vac-F, Ad-F or infection with RSV induced high levels of ELISA-F antibodies, but the antibodies induced by purified F glycoprotein of Bac-FG had low levels of neutralizing activity. Immunization with Vac-F or Ad-F, or infection with RSV induced a high level of resistance to pulmonary RSV replication, whereas animals immunized with Bac-FG or FI-RSV were only partially protected. Following RSV challenge, animals immunized with purified F glycoprotein or Bac-FG developed the highest levels of bronchiolar and alveolar histopathology, those immunized with FI-RSV had intermediate levels, and those immunized with Vac-F or RSV had histopathology scores at control levels. Ad-F immunized animals had elevated scores of bronchiolar but not alveolar histopathology; however, this finding was not reproducible. Passive transfer of pooled immune sera from animals infected with RSV or Vac-F and Vac-G was highly protective, whereas pooled sera from animals immunized with Bac-FG failed to protect the lungs against RSV challenge. Increased pulmonary histopathology was not observed in the passively immunized animals following RSV challenge, suggesting that the histopathology was mediated by RSV-specific T cells. These data indicate that subunit F glycoprotein or chimeric FG vaccines share with FI-RSV the properties of (i) induction of F antibodies with low neutralizing activity and (ii) enhancement of pulmonary histopathology during subsequent RSV infection. These observations confirm the need for caution in studies involving the administration of RSV subunit vaccines to seronegative humans.

Animals↗
PubMed1991

Effector phenotypes and mechanisms of antitumor immune reactivity of tumor-immunized and tumor-bearing mice in two syngeneic tumors.

By using two different syngeneic tumors, Meth A sarcoma and RL male 1 lymphoma of BALB/c origin, the present study was designed to investigate the subset(s) of T cells mediating in vivo antitumor immune responses and some of the effector mechanisms of in vivo protective immunity in BALB/c mice immunized against tumor or bearing tumor. Spleen cells from the mice immunized against Meth A tumor or bearing Meth A tumor inhibited the growth of Meth A tumor in the Winn assay. In the Meth A-immunized mice, L3T4+ (CD4+) cells played a major role in mediating the inhibitory activity against Meth A tumor growth, whereas in the Meth A-bearing mice, the antitumor protective immunity was mediated by both L3T4+ and Lyt-2+ (CD8+) cells. Spleen cells from the Meth A-immunized or Meth A-bearing mice were not able to generate cytotoxic T lymphocytes (CTL) directed against Meth A tumor after the in vitro restimulation of spleen cells with mitomycin C (MMC)-treated Meth A cells, while fresh spleen cells from the Meth A-immunized or Meth A-bearing mice were able to induce the strong delayed-type hypersensitivity (DTH) responses to Meth A tumor. The DTH response to Meth A tumor was mediated by L3T4+ cells in the Meth A-immunized mice and by both L3T4+ and Lyt-2+ cells in the Meth A-bearing mice. In the similar experiments performed in the RL male 1 lymphoma, the antitumor activity in spleen cells from the RL male 1-immunized or RL male 1-bearing mice depended on Lyt-2+ but not L3T4+ cells in the Winn assay. When spleen cells from the RL male 1-immunized or RL male 1-bearing mice were cultured with MMC-treated RL male 1 cells for 5 days, an appreciable CTL response to RL male 1 tumor was induced. These results suggest that the nature of tumor and/or tumor antigens determines which T cell subset is required to exhibit the protective immunity against tumor and thus the different effector mechanisms could be induced in the different tumor models. Furthermore, these data support the conclusion that antitumor T cell responses are affected by the immune state of host to tumor.

Animals↗
PubMed1992

Immunity to B16 melanoma in mice immunized with IL-2-secreting allogeneic mouse fibroblasts expressing melanoma-associated antigens.

Co-presentation of weak tumour-associated antigens along with strongly immunogenic determinants leads to the development of an anti-tumour immune response in recipients syngeneic with the tumour. Tumour immunity develops in mice immunized with tumour cells modified by the introduction of cDNA for interleukin-2 (IL-2). Here, we report the anti-tumour response following immunization with an IL-2-secreting cell construct that expresses tumour-associated antigens, along with allogeneic major histocompatibility antigens. The construct was prepared by transfecting LM(TK-) mouse fibroblasts (H-2k) with genomic DNA from B16 melanoma cells syngeneic in C57BL/6J mice (H-2b). Transfectants expressing melanoma-associated antigens (MAA) were then infected with an expression-competent retroviral vector containing a cDNA specifying human IL-2. Cytotoxicity toward B16 cells was detected for as long as 5 months in both spleen and macrophage cell populations in C57BL/6J mice immunized with the IL-2-secreting cells. Mice immunized with non-IL-2-secreting, MAA-positive allogeneic cells developed melanoma immunity as well, but to a lesser extent. Immunity to 2 tumour-cell lines expressing the H-2d haplotype and to YAC-1 cells was detected in peritoneal macrophages, but not in spleen cells from C57BL/6J mice immunized with the cell construct, indicating that the response to B16 cells was only partially specific. C57BL/6J mice immunized with the IL-2-secreting cell construct survived significantly longer, following an injection of viable B16 cells, than mice in various control groups. The contribution of allogeneic antigens to the melanoma immunity was indicated by the failure of mice syngeneic with LM(TK-) cells to develop melanoma immunity following immunization with non-IL-2-secreting, MAA-positive cell constructs. The formation of IL-2 partially compensated for the lack of allogeneic antigens.

Animals↗
PubMedDate not supplied

Analyses of the primary in vitro responsiveness of non-immune porcine peripheral blood mononuclear cells with reference to immunization by African swine fever virus antigen and treatment with leucine methyl ester.

Peripheral blood mononuclear cells (PBMC) from non-immune pigs were immunized in vitro using African swine fever (ASF) virus antigen with concomitant mitogenic stimulations known to have varying effects on B and T lymphocyte activity. None of these conditions, including those previously reported as being successful for the in vitro immunization of non-immune porcine PBMC with ASF virus antigen, supported the induction of specific antibody. Due to the reports on in vitro immunization of human PBMC, attempts were made to control suppressor cell activity in the porcine PBMC from non-immune pigs through L-leucine methyl ester (Leu-OMe) treatment. Upon immunization of the Leu-OMe treated PBMC with ASF virus antigen, concomitant with mitogen or cytokine stimulations, no specific antibody production was detected. Nevertheless, aspecific porcine immunoglobulin secretion was observed. Further analysis of the PBMC responsiveness demonstrated that 2.5 mM Leu-OMe (the dose recommended for use with human PBMC) suppressed mitogen-induced porcine lymphocyte proliferation, but in the absence of any detectable cytotoxicity. In fact, both anti-ASF virus antigen specific immunization and stimulation with "T-lymphocyte" mitogens were suppressed, whereas pokeweed mitogen stimulation of B lymphocyte aspecific immunoglobulin secretion was unaffected. Consequently, it was not possible to immunize in vitro non-immune porcine PBMC with ASF virus antigen as had been previously reported, nor was it possible to transfer the technology successfully used with non-immune human PBMC to the in vitro stimulation/immunization of non-immune porcine PBMC. The furtherance of this work will require greater insight into the immunobiological parameters and dynamics of the stimulation of non-immune porcine peripheral blood leukocytes, which are not as simple as previously reported, nor the same as identified with human PBMC.

African Swine Fever↗
PubMed1976

Mediation of cytotoxic immune responses against human tumor-associated antigens by xenogeneic immune RNA.

Xenogeneic immune RNA (I-RNA), extracted from the lymphoid organs of sheep or guinea pigs immunized with human tumor cells, mediated in vitro cytotoxic immune responses that were directed specifically against tumor-associated antigens of human tumor target cells. Normal human peripheral blood lymphocytes from healthy donors became markedly more cytotoxic for human tumor target cells after being incubated with I-RNA extracted from the lymphoid organs of animals that had been immunized with that particular tumor. Gastric carcinoma, malignant melanoma, and carcinoma of the breast were studied. Lymphocytes incubated with RNA from animals immunized with only complete Freund's adjuvant evidenced no increased cytotoxic activity. RNA extracted from the lymphoid organs of animals immunized with normal skin fibroblasts that were autologous to the immunizing tumor, when incubated with normal allogeneic lymphocytes, also mediated cytotoxic immune reactions against tumor target cells. These immune responses probably were directed principally against normal transplantation antigens. However, when lymphocytes that were autologous to the immunizing tumor and/or the tumor target cells were incubated with RNA from animals immunized with autologous normal fibroblasts, cytotoxicity did not increase. Only I-RNA extracted from donor animals specifically immunized with tumor cells mediated cytotoxic antitumor immune responses when incubated with autologous lymphocytes.

Animals↗
PubMed1975

Control of the immune response. I. Depression of DNA synthesis by immune lymph node cells.

The DNA response in the regional lymph nodes draining the site of immunization with contact sensitizing agents was assessed by measuring the uptake of radioactive iododeoxyuridine. The DNA response in the regional lymph nodes reached a peak on day 3 after immunization and fell to pre-immunization levels by day 6. The hypothesis was tested that lymph node cells from mice immunized with picryl chloride might depress the DNA response to the same antigen. Immune lymph node cells were injected intravenously and the recipient mice were immunized with picryl chloride on the same day. The immune cells depressed the DNA response on day 4 by an average of about 60 per cent. Smaller but significant depression also occurred on day 3. The cells responsible for the depression appeared in the regional lymph nodes 3-4 days after immunization and disappeared by day 21. The transfer of small numbers of immune cells (less than 2-5 X 10(6)) increased the DNA response in recipients 4 days after immunization with picryl chloride. The depression of the DNA response was largely specific. Pooled data from ten experiments showed that cells immunized with 4-ethoxymethylene-phenyl oxazolone ('oxazolone') caused no depression of the DNA response to picryl chloride, although in two of these experiments significant depression of about 21 per cent was seen. Similar results were obtained when immune cells were injected into mice immunized with 'oxazolone'.

Animals↗
PubMed1975

Bacteriocinogenic Clo DF13 minicells of Escherichia coli synthesize a protein that accounts for immunity to bacteriocin Clo DF16: action of the immunity protein in vivo and in vitro.

The Clo DF13 plasmid-specific immunity protein is able to prevent the inhibitory effect of cloacin DF13 on in vitro protein synthesis. We have shown, by gel filtration, that direct binding of the Clo DF13 immunity protein to cloacin occurs in vitro. This cloacin DF13-immunity protein complex is rather stable, and the cloacin present in the complex is no longer able to cause inhibition of in vitro protein synthesis. The binding of immunity protein to cloacin DF13 is rather specific because the Clo DF13 immunity protein does not bind to in vitro inactive cloacin and binds very poorly to the closely related bacteriocin colicin E3. Furthermore, we present data which strongly suggest that in vitro at least a fourfold excess of immunity protein is required to ensure that every cloacin molecule is inactivated by cloacin-immunity protein complex formation. Only a fraction (an about equimolar amount) of the immunity protein molecules, however, actually binds to cloacin DF13. The existence of an immunity protein-cloacin complex in vivo was concluded from the observation that cloacin, purified by chromatography on diethyl-(2-hydroxypropyl)-aminoethyl Sephadex in the absence of urea, contains an about equimolar amount of a second protein which comigrates with immunity protein on sodium dodecyl sulfate-polyacrylamide and urea-polyacrylamide gels. In an in vitro protein-synthesizing system, this component appeared to behave identical to the Clo DF13 immunity protein. The purified immunity protein-containing cloacin was at least 80 times less active in inhibiting in vitro protein synthesis, compared to cloacin, free of immunity protein. These data imply that few, if any, cloacin DF13 molecules are present in cloacinogenic cells as active, free cloacin molecules.

Bacterial Proteins↗
PubMed1977

Adoptive transfer of immunity from mice immunized with ribosomes or live yeast cells of Histoplasma capsulatum.

This investigation was designed to compare the role of lymphoid cells and immune serum in protective immunity induced by immunization with ribosomes or live yeast cells of Histoplasma capsulatum. Spleen cells, peritoneal cells, and serum from C3H mice immunized with Histoplasma ribosomes or live cells were transferred intravenously to separate groups of syngeneic recipients. All recipients along with a set of immunized and control mice were challenged intravenously with 4 x 10(6) yeast cells of H. capsulatum, and protection was assessed. Immunization with ribosomes or live cells provided 90 to 100% protection. Mice receiving filtered spleen cells or peritoneal cells from donors immunnized with live cells showed 90 to 100% protection; 80 to 90% protection was observed for mice receiving cells from ribosome-immunized donors. In contrast, no evidence of protection was seen in mice receiving serum from either live-cell- or ribosome-immunized mice. Peritoneal cells were far more efficient than spleen cells in adoptive transfer of immunity. The adoptive immunity in recipients persisted for at least 3 weeks after transfer, the longest period tested in the present study. These results indicate that the immunity elicited by immunization with Histoplasma ribosomes or live cells is mediated by a cellular mechanism.

Animals↗