PubMed Health⌕ Search

Biomedical subjects

M J Reddehase

Publications and source records attributed to M J Reddehase.

At least 37 records · Page 2Linked to original sources
PubMed1997

Bone marrow failure by cytomegalovirus is associated with an in vivo deficiency in the expression of essential stromal hemopoietin genes.

Bone marrow (BM) failure associated with cytomegalovirus (CMV) infection is a feared complication after clinical BM transplantation. Experiments in long-term BM cultures have indicated that BM stromal cells (BMSC) are targets of productive CMV infection, but an in situ infection of BM stroma remained to be documented, and the pathomechanism is open to question. Here we describe a murine in vivo model of lethal CMV aplastic anemia (CMV-AA). The reconstitution of hematopoietic progenitor cells expressing stem cell factor (SCF) receptor was found to be defective in CMV-AA. While murine CMV replication in permissive parenchymal tissues is cytolytic, the hematopoietic cord was found to be a site of very limited virus production with foci of reticular BMSC expressing the intranuclear viral IE1 protein, but with only a few BMSC positive for viral genome in the in situ hybridization. XX-XY BM chimeras were established in order to quantitate Y-chromosome-tagged BMSC by a PCR specific for the male-sex-determining gene Tdy. This approach revealed that murine CMV infection is not associated with a significant loss of BMSC. Despite the physical integrity of the stromal network, the functional integrity of the stroma was impaired. While housekeeping genes were expressed normally in BMSC of infected mice, the expression of genes encoding the essential hemopoietins SCF, granulocyte colony-stimulating factor, and interleukin-6 was markedly reduced. In conclusion, the mechanism of BM failure is not a stromal lesion but an insufficient stromal function. These findings explain CMV-AA as a manifestation of multiple hemopoietin deficiency.

Anemia, Aplastic↗
PubMed1994

The conditions of primary infection define the load of latent viral genome in organs and the risk of recurrent cytomegalovirus disease.

Recurrence of cytomegalovirus (CMV) from latency is a frequent cause of disease in immunocompromised patients. To date, there is no explanation for the diversity in the clinical manifestations. Primary infection can occur perinatally or later in life, and inevitably results in latent infection. Seropositivity for antibodies against CMV is indicative of latent infection, but is insufficient as a predictor for the risk of recurrence. As a model for this important medical problem, we compared the risks of murine CMV recurrence from latency established after neonatal primary infection and after infection at adult age. The risk of CMV recurrence was high only after neonatal infection. The copy number of latent viral genome in tissues was identified as the key parameter that determines the overall and organ-specific risks of recurrence. Latent CMV burden and risk of recurrence were related to the extent of virus multiplication during primary infection. The presence of latent CMV in multiple organs provides the molecular basis for stochastic events of recurrence in single organs or in any combination thereof. These findings are discussed as a concept of multifocal CMV latency and recurrence. It provides a rationale for the diversity in the clinical outcome of CMV disease.

Animals↗
PubMed1994

Porcine T-cell receptors: molecular and biochemical characterization.

Two subclasses of CD3 associated T-cell receptors (TcR) have been described so far, consisting of either an alpha and beta chain (TcR alpha beta) or a gamma and delta chain (TcR gamma delta). Of the two subclasses, the TcR alpha beta is the one predominantly expressed on peripheral T lymphocytes of humans and rodents. TcR gamma delta T lymphocytes represent only a minor subset in these species. Among all mammalian species studied so far, swine showed the most diversified composition of the T-lymphocyte population characterized by the expression of CD4 and CD8 differentiation antigens. Besides CD4+CD8- and CD4-CD8+ T lymphocytes, CD4+CD8+ and CD4-CD8- T lymphocytes are prominent in the extrathymic T-lymphocyte compartment. Because of the lack of specific monoclonal antibodies (mAb), to date the porcine TcR can only be characterized with biochemical and molecular biological methods. TcR on porcine peripheral blood T lymphocytes with the phenotype CD4+ and/or CD8+ are characterized as 46-48 kDaR heterodimers which were supposed to represent the porcine TcR alpha beta. Biochemical analyses of the CD4-CD8- T lymphocytes revealed three distinct TcR gamma delta; all are characterized by a 40 kDa delta chain but differed in their gamma chains. One gamma chain with a molecular mass of 38 kDaR is preferentially expressed on CD4-CD8- T lymphocytes derived from peripheral blood; another chain with molecular mass of 37 kDaR is evenly distributed between CD4-CD8- T lymphocytes from blood and lymphoid tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

The establishment of cytomegalovirus latency in organs is not linked to local virus production during primary infection.

Recovery from primary cytomegalovirus (CMV) infection is associated with resolution of the productive infection without clearance of the virus genome from affected organs. The presence of latent CMV genome in multiple organs provides the molecular basis for recurrence of CMV within multiple organs, and explains the diversity in the organ manifestations of recrudescent CMV disease during states of immunodeficiency. As a part of a unifying concept of multifocal CMV latency and recurrence, previous work has demonstrated the importance of primary virus replication for the overall load of latent CMV in organs and the risk of recurrence. In the present report, the establishment of CMV latency was studied in a murine model in which the course of primary infection in the immunocompromised host after syngeneic bone marrow transplantation was modulated by a CD8+ T cell immunotherapy. The antiviral CD8+ effector cells limited virus replication in all organs and protected the recipients from lethal CMV disease, but after resolution of the productive infection virus DNA remained. Interestingly, the copy number of latent virus DNA in tissue did not quantitatively reflect the preceding virus production in the respective organ. Specifically, in contrast to the case in the lungs and the salivary glands, virus replication in the spleen was suppressed by CD8+ T cells to below the limit of detection; yet, virus DNA was also detected in the spleen during latency and accordingly, virus recurrence in the spleen could be induced. These findings demonstrate that the control of virus replication in a particular organ does not prevent the establishment of latency in that organ.

Animals↗
PubMed1993

Expression of gamma/delta T cell receptors in porcine thymus.

Swine possess an extraordinarily high number of T lymphocytes with the phenotype CD4-CD8- in peripheral blood as well as in lymphoid tissues. This subpopulation is subdivided into at least four subsets defined by the expression of CD2 and three biochemically distinct gamma/delta T cell receptors. The four subsets differ largely in their pattern of lymphoid homing in that CD2- subsets, historically referred to as null lymphocytes, predominate in the circulating pool, whereas CD2+ subsets are enriched in lymphoid tissues. Here we document the expression of all three types of gamma/delta T cell receptors by CD4-CD8- porcine thymocytes, which provides the first evidence for a thymic origination of all subsets of porcine gamma/delta T lymphocytes. The biochemical analysis shows that three distinct gamma-chains form disulfide-bonded cell surface heterodimers with a common delta-chain and that glycosylation of all chains is already completed within the thymus. Surprisingly, CD2- subsets, which are known to be enriched among thymic emigrants and which numerically predominate in peripheral blood, are underrepresented in the thymus, suggesting a high export rate.

Aging↗
PubMed1993

Lungs are a major organ site of cytomegalovirus latency and recurrence.

Recurrence of infectious virus from the latent viral genomes is the initiating event in the pathogenesis of cytomegalovirus (CMV) disease during states of immunodeficiency. Interstitial pneumonia is a frequent manifestation of posttransplantation CMV disease, in particular after bone marrow transplantation and heart and lung transplantations. Recurrence can occur within the transplant derived from a latent infected donor as well as within latently infected organs of the transplant recipient. The reason for a predilection of the lungs as a site of CMV pathology is so far unknown. In a murine model of CMV latency, the lungs were identified as an authentic site of latent infection, since the viral genome remained detectable in lung tissue even after it was cleared to an undetectable level in blood and bone marrow. A comparison between the lungs and the spleen, the previously most thoroughly investigated site of murine CMV latency, revealed a 10-fold-higher burden of latent viral genome for the lungs. Most important, the organ-specific risk of in vivo recurrence was found to correlate with the organ-specific viral genomic load. This new finding thus characterizes the lungs as a high-risk organ for CMV recurrence, and this fact may explain in part why interstitial pneumonia is a frequent manifestation of recurrent CMV infection.

Animals↗
PubMed1992

Molecular modeling of an antigenic complex between a viral peptide and a class I major histocompatibility glycoprotein.

Computer simulation of the conformations of short antigenic peptides (5-10 residues) either free or bound to their receptor, the major histocompatibility complex (MHC)-encoded glycoprotein H-2 Ld, was employed to explain experimentally determined differences in the antigenic activities within a set of related peptides. Starting for each sequence from the most probable conformations disclosed by a pattern-recognition technique, several energy-minimized structures were subjected to molecular dynamics simulations (MD) either in vacuo or solvated by water molecules. Notably, antigenic potencies were found to correlate to the peptides propensity to form and maintain an overall alpha-helical conformation through regular i,i + 4 hydrogen bonds. Accordingly, less active or inactive peptides showed a strong tendency to form i,i + 3 hydrogen bonds at their N-terminal end. Experimental data documented that the C-terminal residue is critical for interaction of the peptide with H-2 Ld. This finding could be satisfactorily explained by a 3-D Q.S.A.R. analysis postulating interactions between ligand and receptor by hydrophobic forces. A 3-D model is proposed for the complex between a high-affinity nonapeptide and the H-2 Ld receptor. First, the H-2 Ld molecule was built from X-ray coordinates of two homologous proteins: HLA-A2 and HLA-Aw68, energy-minimized and studied by MD simulations. With HLA-A2 as template, the only realistic simulation was achieved for a solvated model with minor deviations of the MD mean structure from the X-ray conformation. Water simulation of the H-2 Ld protein in complex with the antigenic nonapeptide was then achieved with the template-derived optimal parameters. The bound peptide retains mainly its alpha-helical conformation and binds to hydrophobic residues of H-2 Ld that correspond to highly polymorphic positions of MHC proteins. The orientation of the nonapeptide in the binding cleft is in accordance with the experimentally determined distribution of its MHC receptor-binding residues (agretope residues). Thus, computer simulation was successfully employed to explain functional data and predicts alpha-helical conformation for the bound peptide.

Computer Simulation↗
PubMed1992

Hematopoietic stem cell deficiency resulting from cytomegalovirus infection of bone marrow stroma.

Cytomegalovirus (CMV) recurrence from latency is a major risk factor in bone marrow transplantation (BMT). Owing to the immunodepletive treatment, ablation of the immune control of latent CMV is responsible for recurrence and cytopathogenic spread of the virus in vital tissues. There is increasing evidence for reconstituting bone marrow being itself a target tissue of CMV. By inhibiting post-transplantation hematopoiesis, CMV is causal for maintenance of the immunocompromised state, which leads to a prolonged phase of persistent virus replication. Based on results in a murine model of BMT and concurrent CMV infection, we discuss possible mechanisms of CMV-mediated bone marrow graft failure. It is concluded that an irremediable damage of bone marrow stroma by CMV is responsible for a reduced rate of regeneration of the marrow-repopulating, pluripotent stem cell.

Bone Marrow↗
PubMed1992

Pathogenesis of classical swine fever: B-lymphocyte deficiency caused by hog cholera virus.

Hog cholera, also known as classical or European swine fever, is caused by hog cholera virus, a member of the genus Pestivirus. It is shown here that the end stage of lethal infection in the natural host is associated with a dramatic depletion preferentially of B lymphocytes in the circulatory system as well as in lymphoid tissues. Already at the onset of disease, viral replication in lymphoid tissues demarcates the germinal centers, and the viral genome remains localized to that site as the disease progresses even after morphologic disintegration of the follicular structure. A block in B-lymphocyte maturation by infection and destruction of germinal centers is discussed as a key event in the pathogenesis of acute, lethal hog cholera.

Animals↗
PubMed1992

Rabies virus neuritic paralysis: immunopathogenesis of nonfatal paralytic rabies.

Two pathogenetically distinct disease manifestations are distinguished in a murine model of primary rabies virus infection with the Evelyn-Rokitnicky-Abelseth strain, rabies virus neuritic paralysis (RVNP) and fatal encephalopathogenic rabies. RVNP develops with high incidence in immunocompetent mice after intraplantar infection as a flaccid paralysis restricted to the infected limb. The histopathologic correlate of this monoplegia is a degeneration of the myelinated motor neurons of the peripheral nerve involved. While, in this model, fatal encephalopathogenic rabies develops only after depletion of the CD4 subset of T lymphocytes and without contribution of the CD8 subset, RVNP is identified as an immunopathological process in which both the CD4 and CD8 subsets of T lymphocytes are critically implicated.

Animals↗
PubMed1992

Principles of cytomegalovirus antigen presentation in vitro and in vivo.

Cytomegaloviruses are members of the ubiquitous family of herpesviruses. They escape immunological clearance and persist throughout life in the infected host. Yet, the stability of the balance of this virus-host interaction is dependent upon the state of the cellular immune response, and usually requires the function of specific CD8 T lymphocytes. In a mouse model, the major antigen that triggers protective CD8 T lymphocytes has been characterized as a nonameric amino acid motif of a nonstructural virus protein. Analysis of the naturally presented peptide has led to the conclusion that the sequence of an antigenic epitope is not the only parameter that decides upon its efficient presentation. Furthermore, the virus has developed regulatory functions that can prevent antigen presentation in productively infected cells. Contradictions between in vivo and in vitro findings are resolved in a hypothesis postulating an essential contribution of cytokines to the in vivo control of productive cytomegalovirus infection.

Amino Acid Sequence↗
PubMed1991

Efficient processing of an antigenic sequence for presentation by MHC class I molecules depends on its neighboring residues in the protein.

Processing of endogenously synthesized proteins generates short peptides that are presented by MHC class I molecules to CD8 T lymphocytes. Here it is documented that not only the sequence of the presented peptide but also the residues by which it is flanked in the protein determine the efficiency of processing and presentation. This became evident when a viral sequence of proven antigenicity was inserted at different positions into an unrelated carrier protein. Not different peptides, but different amounts of the antigenic insert itself were retrieved by isolation of naturally processed peptides from cells expressing the different chimeric proteins. Low yield of antigenic peptide from an unfavorable integration site could be overcome by flanking the insert with oligo-alanine to space it from disruptive neighboring sequences. Notably, the degree of protection against lethal virus disease related directly to the amount of naturally processed antigenic peptide.

Alanine↗
PubMed1991

Redistribution of critical major histocompatibility complex and T cell receptor-binding functions of residues in an antigenic sequence after biterminal substitution.

Residues critical for establishing a trimolecular interaction with a major histocompatibility complex (MHC)-encoded receptor and a T cell antigen receptor (TcR) were determined for an antigenic nonapeptide. The N-terminal residue proved to be involved in binding of the peptide to both receptors and the C-terminal residue was essential for MHC binding. While substitution of either of these critical terminal residues by alanine resulted in an almost complete loss of peptide antigenicity, simultaneous substitution of both created a new functional ligand for the same MHC molecule and the same TcR. Notably, in the biterminally substituted peptide, the core residues took on new roles in the trimolecular interaction in that a residue critical in the authentic nonapeptide for TcR binding became critical for MHC binding and former spacer residues became essential to various degrees for the interaction with either receptor or both. Thus, apparently, the loss of the terminal residues' contribution was at least partially compensated by a redistribution of the roles among the remaining residues. These results reflect a cooperative contribution of all residues of an antigenic peptide to its binding to both receptors and thus challenge a static definition of agretope and epitope as MHC and TcR binding sites.

Amino Acid Sequence↗
PubMed1991

The role of CD4 and CD8 T cells in viral infections.

Presentation of viral antigens to T cells does not require uptake by 'professional' antigen-presenting cells. Viruses have specialized to enter the cells in which they replicate. Virus entry, uncoating and new viral protein synthesis can load both the cytosolic and the endosomal pathway of antigen processing, resulting in viral peptide presentation to CD8 and CD4 T cells by MHC class I and II molecules, respectively. Although a role of CD8 T cells in the control of viral infection has been well documented, current research interest centers on the contribution of the different CD4 T-cell subsets.

Animals↗
PubMed1991

Resting porcine T lymphocytes expressing class II major histocompatibility antigen.

The immune system of swine is unique in that the expression of CD4 and CD8 antigens defines four subpopulations of resting, extrathymic (CD1-) T lymphocytes in the circulation as well as in lymphoid tissue. Here it is documented that the specialty of the porcine T lymphocyte compartment extends to the expression of class II MHC (SLA) antigens. While the TCR gamma/delta CD4-CD8- as well as the TCR alpha/beta CD4+CD8- subpopulation both lack MHC II, the TCR alpha/beta CD4-CD8+ and the CD4+CD8+ subpopulation, the latter of which is private to swine, both do express MHC II. As opposed to human T lymphocytes, expression of porcine MHC II is not transient and restricted to lymphoblasts but is imminent in small, resting T lymphocytes of the two CD8-expressing subsets, even though also in swine activation can induce MHC II. Activation-induced extrathymic acquisition of MHC II without reversal can be discussed as one possible way of how MHC II+ T lymphocytes are generated. Alternatively, MHC II antigens should already be expressed by thymic progenitors. Remarkably, all CD1+CD4-CD8+ and most CD1+CD4+CD8+ thymocytes lack MHC II, yet, a minor subset with the phenotype CD4hiCD8hi expresses MHC II. One may speculate that these cells do not undergo thymic selection and represent the progenitors of the unusual, swine-typic MHC II+CD4+CD8+ extrathymic T lymphocytes.

Animals↗
PubMed1991

Rescue of myeloid lineage-committed preprogenitor cells from cytomegalovirus-infected bone marrow stroma.

The effect of murine cytomegalovirus on myelopoiesis was studied in long-term bone marrow culture to find an in vitro correlate for the lethal virus interference with bone marrow reconstitution (W. Mutter, M. J. Reddehase, F. W. Busch, H.-J. Bühring, and U. H. Koszinowski, J. Exp. Med. 167:1645-1658, 1988). The in vitro generation of granulocyte-monocyte progenitors (CFU-GM) discontinued after infection of the stromal cell layer, whereas the proliferation and differentiation of CFU-GM to granulocyte-monocyte colonies remained unaffected. A protocol was established to probe the functional integrity of earlier hematopoietic cells. Pre-CFU-GM (the progenitors of the CFU-GM) could be recovered from an infected bone marrow donor culture by transfer onto an inductive recipient stromal cell layer. Thus, at least in vitro, infection of bone marrow stroma appears to be the only cause of the defect in myelopoiesis.

Animals↗