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D Moskophidis

Publications and source records attributed to D Moskophidis.

At least 37 records · Page 2Linked to original sources
PubMed1992

Immunosuppression by lymphocytic choriomeningitis virus infection: competent effector T and B cells but impaired antigen presentation.

Lymphocytic choriomeningitis virus (LCMV) may cause a severe immunosuppression in mice. Its pathogenesis is apparently dependent on LCMV-specific CD8 effector T cells that mediate the destruction of virus-infected cells which are normally essentially involved in immune responses. Evaluation of various LCMV isolates in this study established a general correlation between their tropism for lymphohemopoietic cells and immunosuppression. When immune responses were assessed as the capacity of mice to mount an anti-vaccinia virus cytotoxic T cell response or an IgG response to vesicular stomatitis virus (VSV), after a primary LCMV infection, LCMV-Armstrong, WE, Clone 13 and Docile were increasingly immunosuppressive in a dose-dependent fashion with respect to both extent and duration. Analysis of lymphocyte subpopulations showed variable effects of the various LCMV isolates that did not reveal patterns readily explaining immunosuppression. To evaluate whether LCMV infection affected T and/or B cell functions directly or whether antigen presentation was impaired, adoptive transfer experiments were performed. Untreated or irradiated but uninfected normal recipient mice receiving adoptively transferred T or B cells from LCMV-WE or Docile-infected immunosuppressed donor mice responded within 30%-100% of normal ranges in both assay systems. In contrast, when T or B cells from normal donors were transferred to irradiated or non-irradiated LCMV-immunosuppressed recipients, they failed to mount a significant cytotoxic T cell response against vaccinia virus or an IgG response to VSV. Thus, the T and B cells from LCMV-immunosuppressed mice were able to function within normal ranges; in contrast, histologically and functionally, antigen presentation was severely impaired in LCMV-immunosuppressed mice.

Animals↗
PubMed1992

Suppression of virus-specific antibody production by CD8+ class I-restricted antiviral cytotoxic T cells in vivo.

The question of whether virus-induced immunosuppression includes the antibody response against the infecting virus itself was evaluated in a model situation. Transgenic mice expressing the T-cell receptor (TCR) specific for peptide 32-42 of lymphocytic choriomeningitis virus (LCMV) glycoprotein 1 presented by Db reacted with a strong transgenic cytotoxic T-lymphocyte (CTL) response starting on day 3 after infection with a high dose (10(6) PFU intravenously [i.v.]) of the WE strain of LCMV (LCMV-WE); LCMV-specific antibody production in the spleen was suppressed in these mice. Low-dose (10(2) PFU i.v.) infection resulted in an antiviral antibody response comparable to that of the transgene-negative littermates. The induction of suppression of LCMV-specific antibody responses was specifically mediated by CD8+ TCR transgenic CTLs, since the LCMV-8.7 variant virus (which is not recognized by transgenic TCR-expressing CTLs because of a point mutation) did not induce suppression. In addition, treatment with CD8 monoclonal antibody in vivo abrogated suppression. Once suppression had been established, it was found to be nonspecific. The abrogation of antibody responses depended on the relative kinetics of the antibody response involved and the kinetics of the anti-LCMV CTL response. Analysis of T- and B-cell subpopulations showed no significant changes, but immunohistochemical analysis of spleens revealed extensive destruction of follicular organization in lymphoid tissue by day 4 in transgenic mice infected with LCMV-WE but not in those infected with the CTL escape mutant LCMV-8.7. Impairment of antigen presentation rather than of T or B cells was also suggested by adoptive transfer experiments, showing that transferred infected macrophages may improve the anti-LCMV antibody response in LCMV-immunosuppressed transgenic recipients; also, T and B cells from suppressed transgenic mice did respond in irradiated and virus-infected nontransgenic mice with antibody formation to LCMV. Such virus-triggered, T-cell-mediated immunopathology causing the suppression of B cells and of protective antibody responses, including those against the infecting virus itself, may permit certain viruses to establish persistent infections.

Animals↗
PubMed1991

In vitro selection of lymphocytic choriomeningitis virus escape mutants by cytotoxic T lymphocytes.

Cytotoxic T lymphocyte (CTL)-mediated cytolysis is induced via the interaction of the specific T-cell antigen receptor and the peptidic viral antigen associated with the major histocompatibility complex class I antigen. Here we demonstrate in vitro that lymphocytic choriomeningitis virus (LCMV) can escape the cytotoxic activity of LCMV-specific cloned CTLs by single amino acid changes within the recognized T-cell epitope defined by residues 275-289 of the LCMV glycoprotein [LCMV-GP-(275-289)]. LCMV-infected fibroblasts at a multiplicity of infection of 10(-3) exposed to virus-specific CTL at an effector-to-target cell ratio of 4:1 4 hr after infection was optimal for virus mutant selection. The selections were carried out with three LCMV-GP-(275-289)-specific CTL clones expressing T-cell antigen receptors containing the identical variable gene segments V alpha 4 and V beta 10 but different junctional regions; selection was also possible with LCMV-GP-(275-289)-specific cytotoxic polyclonal T cells. The most common escape mutation was an amino acid change of asparagine (AAT) to aspartic acid (GAT) at position 280; an additional mutation was glycine (GGT) to aspartic acid (GAT) at position 282. The results presented show that relevant point mutations within the T-cell epitope of LCMV-GP-(275-289) occur frequently and that they are selectable in vitro by CTLs.

Amino Acid Sequence↗
PubMed1991

Lower receptor avidity required for thymic clonal deletion than for effector T-cell function.

Clonal deletion in the thymus plays a major part in T-cell tolerance to self antigens. But the mechanism of negative selection, its fine specificity and the threshold of affinity and avidity remains unknown. We have now examined these aspects of negative selection with mice expressing a transgenic T-cell receptor with specificity for lymphocytic choriomeningitis virus (LCMV) glycoprotein in association with the class I H-2Db molecule. These mice were rendered tolerant to LCMV by neonatal infection with mutant LCMVs bearing point mutations in the T-cell epitope recognized by the transgenic T-cell receptor. Variant LCMVs were also tested for their ability to elicit antiviral responses in transgenic mice in vivo and in vitro. Comparison in vivo revealed that a low-avidity receptor interaction, which was unable to induce effector T cells in the periphery, was still sufficient for clonal deletion in the thymus.

Amino Acid Sequence↗
PubMed1991

Production of random classes of immunoglobulins in brain tissue during persistent viral infection paralleled by secretion of interleukin-6 (IL-6) but not IL-4, IL-5, and gamma interferon.

The activities of cytokines were determined in cerebrospinal fluid (CSF) and serum of mice persistently or intracerebrally acutely infected with lymphocytic choriomeningitis (LCM) virus (LCMV). In contrast to CBA/J (LCMV carrier) mice that responded with low levels of LCMV-specific antibody, high-responder NMRI (carrier) mice showed antibody production by B cells outside of lymphoid organs. The B cells that had infiltrated the brains of LCMV carrier mice exhibited no preferential immunoglobulin isotype or subtype virus-specific antibody production. Phenotypic analysis of the brain infiltrates in virus carrier mice revealed dominance of CD4+ T cells in contrast to virtual absence of CD4+ and dominance of CD8+ in mice with acute LCM. In NMRI but not in CBA/J carrier mice, significant concentrations of interleukin-6 (IL-6) were detected in CSF and serum; IL-2, IL-4, IL-5, granulocyte-macrophage CSF (GM-CSF), and gamma interferon (IFN-gamma) were not elevated. In contrast, during acute, lethal LCM, IL-6 and IFN-gamma were found at high concentrations, and IL-4, IL-5, and GM-CSF were detectable in CSF and serum, but virus-specific antibody-producing cells were not (yet) detectable in the brain. Thus, distinct cytokine patterns are found in acute versus chronic LCMV infection of the brain: in LCM carrier mice, local random-class immunoglobulin production correlated with the absence of IL-2, IL-4, IL-5, and IFN-gamma but active secretion of IL-6.

Animals↗
PubMed1990

Viral escape by selection of cytotoxic T cell-resistant virus variants in vivo.

Viruses persist in an immune population, as in the case of influenza, or in an individual, as postulated for human immunodeficiency virus, when they are able to escape existent neutralizing antibody responses by changing their antigens. It is now shown that viruses can in principle escape the immunosurveillance of virus-specific cytotoxic T cells by mutations that alter the relevant T-cell epitope.

Amino Acid Sequence↗
PubMed1990

Virus-specific delayed-type hypersensitivity (DTH). Cells mediating lymphocytic choriomeningitis virus-specific DTH reaction in mice.

We had previously shown that the local lymphocytic choriomeningitis virus-induced delayed-type hypersensitivity (DTH) reaction in mice consists of two well delineated phases that are mediated by CD8+ and CD4+ T lymphocytes, respectively. These findings have been confirmed and extended by showing that the first CD8+ cell-dependent part of the response was enhanced by either the presence of CD4+ cells or systemic treatment with IL-2 and that it developed in the absence of detectable numbers of mononuclear phagocytes, whereas the later CD4+ cell part required monocytes or related elements. Furthermore, in the DTH reaction that was elicited with noninfectious viral Ag in mice previously immunized by infection, only the CD4+ cells participated. Thus, the two phases of the lymphocytic choriomeningitis-viral DTH reaction are principally different, which has to be taken into account when trying to assess the relevance of DTH during this virus infection.

Animals↗
PubMed1989

Enumeration of single IFN-gamma-producing cells in mice during viral and bacterial infection.

A solid phase immunoenzymatic technique was employed for detecting single IFN-gamma-producing cells (IFN-gamma PC) in the mouse. After infection with lymphocytic choriomeningitis virus or Listeria monocytogenes, the numbers of IFN-gamma PC in spleens began to rise on day 4, attained maxima on days 7 and 8, and declined thereafter. Negative selection in vitro by use of mAb and C allowed phenotypic identification of the producer cells; most, if not all, carried Thy-1, and approximately one half expressed CD4, the other half, CD8. Depletion of cells in vivo by treatment of mice with mAb led to somewhat different results; again, anti-Thy-1 antibody eliminated essentially all IFN-gamma PC, but considerably more than 50% were either CD4+ or CD8+, suggesting regulatory interactions between these T lymphocyte subsets with regard to generation of the lymphokine.

Animals↗
PubMed1989

Virus-induced delayed-type hypersensitivity reaction is sequentially mediated by CD8+ and CD4+ T lymphocytes.

After subcutaneous inoculation into the hind foot of a mouse, the lymphocytic choriomeningitis (LCM) virus multiplies locally, attaining 10(7)-10(8) mouse infectious units per g of tissue; elimination commences around day 7. About 1 day earlier, the foot begins to swell, which is regarded as a delayed-type hypersensitivity (DTH) reaction. To answer the question of whether the local inflammatory response is involved in virus clearance, we needed to known what cells mediate both these phenomena. With three different procedures--namely, depletion in vivo of defined cells by treatment of mice with monoclonal antibodies ("serologic surgery"), adoptive immunization with negatively selected cells, and adoptive immunization with cells from mice differing at the major histocompatibility gene complex--it is shown that the LCM virus-induced local DTH reaction consists of two phases that are sequentially mediated by (first) class I-restricted cytotoxic/suppressive CD8+ and (second) class II-restricted helper/inducer CD4+ T lymphocytes. In contrast, for virus elimination only the former subset of T lymphocytes was found to be needed. Thus, an association may exist between the CD8+ cell-mediated component of the local DTH response and control of the infection, but the CD4+ cell-mediated part appears to be of doubtful antiviral relevance.

Animals↗
PubMed1989

Mechanism of recovery from acute virus infection. IX. Clearance of lymphocytic choriomeningitis (LCM) virus from the feet of mice undergoing LCM virus-specific delayed-type hypersensitivity reaction.

As shown previously, after inoculation into the footpad of a mouse the lymphocytic choriomeningitis (LMC) virus multiplies locally. Beginning on day 6 or 7 after infection, the foot undergoes a delayed-type hypersensitivity (DTH) reaction which consists of two distinct phases that are mediated by CD8+ cells and CD4+ cells, respectively, and at about the same time the virus is eliminated. In general, for terminating infection of the mouse with LCM virus the CD8+ cytotoxic/suppressive T lymphocyte (CTL) is essential; we have now determined the cells that mediate control of the virus in a tissue undergoing a specific DTH reaction. Depletion, in infected mice, of all T lymphocytes by treatment with anti-Thy-1 monoclonal antibody prevented virus elimination from the foot, and the same was true when the CD8+ CTLs were removed. Depletion of the CD4+ helper/suppressor subset only marginally impaired the ability of the mice to rid themselves of the virus. The conclusion that here too the principal antiviral element is the CD8+ CTL was confirmed by experiments in which footpad-infected mice were adoptively immunized with virus-immune splenocytes from syngeneic mice selected for subclasses of T lymphocytes, or from mice differing in defined regions of the major histocompatibility complex (MHC), and also by experiments in which monocytes were virtually absent. However, CD8+ CTL alone or cells from MHC recombinant mice with identity in class I loci were never as antivirally active as unseparated splenocytes from syngeneic donor mice. Since the CD8+ cells' performance could be optimized by interleukin-2, we assume that the CD4+ T lymphocytes function as accessory cells; the same probably applies to monocytes.

Animals↗
PubMed1987

Mechanism of recovery from acute virus infection. IV. Questionable role of mononuclear phagocytes in the clearance of lymphocytic choriomeningitis virus from spleens of mice.

After intravenous infection of mice with 10(3) infectious units (IU) the WE strain lymphocytic choriomeningitis (LCM) virus multiplied in the spleens (as in all other major organs), reaching more than 10(8) IU/g of tissue on days 4 to 5. Subsequently, the virus was quickly eliminated, being below detectability usually by day 10. During the time of virus clearance, the mononuclear phagocytes (MNP) of the spleen were activated as revealed by suppression of growth of Listeria monocytogenes and increase of cell-associated hydrolytic enzymes. In athymic nude mice, in whom the MNP system is assumed to be permanently activated, the virus replicated slightly but reproducibly less than in their euthymic counterparts. However, when the MNP were activated by Corynebacterium parvum, virus in spleens attained higher concentrations than in mice not so treated, and the rate of elimination was not altered. In mice whose MNP had been damaged by injection of dextran sulfate 500, the spleen virus titers were also increased, but the subsequent immune elimination was slightly delayed. Activation of spleen MNP was not evident at the time virus was rapidly cleared as a result of transfusion of LCM-immune T lymphocytes. Adoptive immunization was as successful in mice that had been pretreated with gamma-rays or cyclophosphamide, suggesting that replicating cells or their descendants, in particular monocytes, did not participate measurably in the process of elimination. Pretreatments of recipients with dextran sulfate 500 reduced the efficacy of transfused LCM-immune T lymphocytes, but this compound probably directly affected the cells. We interpret these findings to mean that the LCM virus in the mouse's spleen is controlled by a mechanism in which MNP do not play an essential role.

Animals↗
PubMed1987

Antiviral antibody-producing cells in parenchymatous organs during persistent virus infection.

In mice persistently infected with lymphocytic choriomeningitis virus (LCMV), the parenchymatous organs contain infiltrates of mononuclear cells, the sizes and numbers of which vary between strains and become more numerous and extensive when the animals grow older. Histologically, these were found to possess a tissue-like structure, and by use of immunohistologic procedures they were shown to contain plasma cells secreting IgM and IgG. Cells of kidneys, livers, brains, and spleens of LCMV carrier mice were dispersed by digestion with trypsin, leukocytes were separated by density gradient centrifugation, and numbers of cells producing antibodies against LCMV were determined by use of a solid-phase immunoenzymatic technique. In all these organs, cells producing LCMV-specific IgM and IgG antibodies were demonstrated, the latter more numerous than the former. Their numbers correlated with numbers and extent of the lymphoid cell infiltrates. The blood of the same mice was essentially free of antiviral antibody-forming cell. The proportion of cells producing LCMV-specific antibodies to all cells producing Ig of any specificity varied between organs, being lowest in spleen, intermediate in liver and kidney, and highest in the brain, where in individual mice up to 90% of all active cells produced virus-specific antibodies. The LCMV carrier mouse should prove to be a useful animal model to investigate antibody production in parenchymatous organs during persistent virus infections.

Aging↗
PubMed1987

The immune response of the mouse to lymphocytic choriomeningitis virus. V. High numbers of cytolytic T lymphocytes are generated in the spleen during acute infection.

In the spleens of C57BL/6J (B6) and CBA/J (CBA) mice undergoing acute infection with lymphocytic choriomeningitis (LCM) virus, lymphocytes with the ability to develop in vitro into LCM virus-specific cytolytic clones were enumerated by use of the limiting dilution method. At intervals after virus inoculation, defined numbers of cells were cultivated with virus-infected syngeneic stimulator cells and T cell growth factor in multiple wells of microculture plates. After 7 days, individual cell cultures were tested for their ability to cause release of 51Cr from infected and uninfected syngeneic target cells. In cultures seeded with spleen cells from uninfected mice or from mice infected 3 days previously, no cytolytic activity was observed. On day 5, cells developing into LCM virus-specific cytolytic effector cells were detected. They rose in numbers, and on days 8 to 9 after infection, values of approximately 1/10 and 1/200 in B6 and CBA mice, respectively, were calculated. A low proportion of microcultures proved cytolytic also for noninfected syngeneic target cells, but the counts thus released were consistently much lower than the counts set free from infected targets, and no regular dose-response relationships existed between seeded cells and positive cultures. Determination of cell surface antigens of responder cells by negative and positive selection procedures disclosed that they were predominantly T lymphocytes and expressed Lyt-2 but not L3T4 surface markers. Lysis by the great majority of LCM virus-specific clones was restricted by products of the major histocompatibility gene complex (MHC), but a few lysed, in addition, allogeneic infected or uninfected targets; however, a consistent pattern of alloreactivity was not observed. Furthermore, cells of a proportion of the cultures also lysed uninfected YAC cells. Probably this natural killer-like activity was acquired by T lymphocytes during prolonged cultivation. We conclude that most spleen cells that during acute infection with LCM virus attained the ability to develop in vitro into LCM virus-specific cytolytic clones were derived from MHC-restricted Lyt-2+, L3T4- antigen-specific cytolytic T lymphocytes and their activated precursors.

Acute Disease↗
PubMed1987

Mechanism of recovery from acute virus infection: treatment of lymphocytic choriomeningitis virus-infected mice with monoclonal antibodies reveals that Lyt-2+ T lymphocytes mediate clearance of virus and regulate the antiviral antibody response.

After intravenous infection of mice, lymphocytic choriomeningitis virus multiplied in spleens and livers, attaining highest concentrations on days 4 to 6. The subsequent clearance was as rapid, and 8 to 10 days after inoculation, infectivity was usually below detectability. During the effector phase of virus elimination, both cytotoxic T-cell (CTL) activity and the number of cells producing antiviral antibodies were high. Monoclonal antibodies directed against T lymphocytes and T-lymphocyte subsets were inoculated once intravenously 5, 6, or 7 days after infection of the animals, and the effects on antiviral immune responses, as well as on elimination of virus from the organs, were determined. Treatment with anti-Thy-1 and anti-Lyt-2 antibodies blocked elimination of the virus and profoundly diminished the activity of spleen CTLs but reduced the antibody response partially (anti-Thy-1) or increased it (anti-Lyt-2). In contrast, treatment with the anti-L3T4 antibody had essentially no effect on either virus elimination or CTL response but abolished antibody production. We conclude that Lyt-2+ (cytotoxic-suppressive) T lymphocytes are needed for elimination of the virus and also regulate the humoral response but that antiviral antibodies are not essential for control of the infection.

Acute Disease↗