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Biomedical subjects

P Hammerl

Publications and source records attributed to P Hammerl.

12 recordsLinked to original sources
PubMed2001

Nucleic acid for the treatment of cancer: genetic vaccines and DNA adjuvants.

Despite some interesting pilot experiments more than a century ago, nucleic acid has only recently been added to the list of agents used for the prevention and therapy of cancer. Two distinct features of nucleic acids are used for this purpose: in DNA and RNA vaccines, genetic information for pathogen- or tumor-derived antigens is delivered to the host who then produces the encoded antigen and initiates an immune response. In DNA adjuvants, immunostimulatory sequences (CpG motifs) present in DNA of bacterial origin are used. Such sequences are delivered in the form of oligonucleotides or within the sequence of DNA vaccine. In addition, CpG oligonucleotides by themselves have successfully been used to stimulate the immune system in an antigen-independent manner for the treatment of experimental tumors. DNA and RNA vaccines for the treatment and prevention of cancer and other diseases suffer from two some shortcomings: insufficient immunogenicity and--in the case of RNA--low stability. A variety of strategies are being explored to improve the efficacy of nucleic acid vaccines (genetic vaccines) especially for self-antigens in the case of cancer. Among the most recent improvements are self-replicating RNA vaccines and replicase-based DNA-vaccines in which antigen expression is under the control of an alphaviral replicase. Despite highly promising results in many animal tumor models the efficacy of nucleic acid vaccines and adjuvants in the clinic remains to be seen.

Adjuvants, Immunologic↗
PubMed2001

Designing immune responses with genetic immunization and immunostimulatory DNA sequences.

Genetic immunization or DNA vaccination represents a rapidly developing technology with new perspectives for the prevention and therapy of infectious diseases and it offers new approaches for the treatment of autoimmunity, tumors and even allergy. DNA vaccines are comprised of plasmid DNA which encodes antigen molecules directly in the transfected cells of a target organism. In contrast to protein-induced immune responses, DNA vaccines stimulate both humoral and cell-mediated immune reactions. In the present review we present a palette of unique features of genetic immunization like the effect of CpG motifs, the influence of mode and site of gene delivery and the modulation of immune responses by co-delivery of cytokines, colony stimulating factors, adhesion molecules and other stimulatory molecules. In addition, modulation of the immune response via translation, processing and presentation will be discussed, which in sum demonstrate the elegant possibilities of genetic immunization to induce tailor-made immune responses.

Animals↗
PubMed2000

Phenotypic characterization of alveolar monocyte recruitment in acute respiratory distress syndrome.

In 49 acute respiratory distress syndrome (ARDS) patients, the phenotype of alveolar macrophages (AMs) was analyzed by flow cytometry. Bronchoalveolar lavage (BAL) was performed within 24 h after intubation and on days 3-5, 9-12, and 18-21 of mechanical ventilation. The 27E10(high)/CD11b(high)/CD71(low)/ 25F9(low)/HLA DR(low)/RM3/1(low) AM population in the first BAL indicated extensive monocyte influx into the alveolar compartment. There was no evidence of increased local AM proliferation as assessed by nuclear Ki67 staining. Sequential BAL revealed two distinct patient groups. In one, a decrease in 27E10 and CD11b and an increase in CD71, 25F9, HLA DR, and RM3/1 suggested a reduction in monocyte influx and maturation of recruited cells into AMs, whereas the second group displayed sustained monocyte recruitment. In the first BAL from all patients, monocyte chemoattractant protein (MCP)-1 was increased, and AMs displayed elevated MCP-1 gene expression. In sequential BALs, a decrease in MCP-1 coincided with the disappearance of monocyte-like AMs, whereas persistent upregulation of MCP-1 paralleled ongoing monocyte influx. A highly significant correlation between BAL fluid MCP-1 concentration, the predominance of monocyte-like AMs, and the severity of respiratory failure was noted.

Adult↗
PubMed1999

Surfactant protein A down-regulates proinflammatory cytokine production evoked by Candida albicans in human alveolar macrophages and monocytes.

Surfactant protein A (SP-A) has been implicated in the regulation of pulmonary host defense and inflammatory events. We analyzed the impact of SP-A on the Candida albicans-induced cytokine response in human alveolar macrophages (AM) and its precursor cells, the monocytes, which rapidly expand the alveolar mononuclear phagocyte pool under inflammatory conditions. Both recombinant human SP-A and natural canine SP-A were employed. SP-A dose-dependently down-regulated the proinflammatory cytokine response of AM and monocytes to both viable and nonviable Candida, including TNF-alpha, IL-1beta, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1. In contrast, SP-A did not affect the baseline liberation of these cytokines. The release of the antiinflammatory cytokines IL-1 receptor antagonist and IL-6 was not inhibited by SP-A under baseline conditions and in response to fungal challenge. The inhibitory effect of SP-A on proinflammatory cytokine release was retained upon reassembly of the apoprotein with natural surfactant lipids and in the presence of serum constituents, for mimicry of plasma leakage into the alveolar space. It was not reproduced by the homologous proteins complement component C1q and type IV collagen. It was independent of Candida-SP-A binding and phagocyte C1q receptor occupancy, but apparently demanded SP-A internalization by the mononuclear phagocytes, effecting down-regulation of proinflammatory cytokine synthesis at the transcriptional level. We conclude that SP-A limits excessive proinflammatory cytokine release in AM and monocytes confronted with fungal challenge in the alveolar compartment. These data lend further credit to an important physiological role of SP-A in regulating alveolar host defense and inflammation.

Blood Proteins↗
PubMed1996

A non-expressed transgene as a cell marker for the investigation of cellular traffic after splenic autotransplantation.

The investigation of cellular interactions during the regeneration of splenic transplants depends upon distinguishing host cells from graft derived cells. As a cell marker which, in contrast to many other marker systems, does not affect histocompatibility, the non-expressed transgene mMT-HGHRH-1 was introduced by mating into NMRI inbred mice to generate the transgenic mouse line BSM. By transplanting non-transgenic NMRI splenic tissue into transgenic BSM hosts, host derived cells could be identified in the transplants by in situ hybridization after regeneration. In a reciprocal approach, implant derived cells were detected in a transgenic transplant after 3 weeks of regeneration in a non-transgenic host. Relative amounts of transgenic cells in transplant cross-sections were estimated from the signal intensity of autoradiographs by densitometry and computer analysis. This approach could be broadly applied in studies of transplantation systems.

Animals↗
PubMed1993

Particulate nitrocellulose as a solid phase for protein immobilization in immuno-affinity chromatography.

The use of nitrocellulose paper as a solid phase matrix for protein immobilization and its application in immunoaffinity chromatography is described. Pieces of nitrocellulose paper were frozen in liquid nitrogen and ground to a powder (NCP) which was then fractionated according to particle size by repeated sedimentation/resuspension cycles in water. The flow properties of different NCP fractions were compared with those of Sephadex G-50. Protein binding capacity and binding dynamics were investigated in a model system with bovine serum albumin (BSA) in phosphate buffered saline. Applications of the material are illustrated by batch chromatography for the removal of anti-carrier protein antibodies from a hapten antiserum and by affinity purification of a hapten-specific antibody fraction using NaSCN elution from haptenated NCP. Furthermore, the applicability of the material in column chromatography is demonstrated by elution of a monospecific fraction of anti-fluorescein antibodies from a hapten/carrier mixed bed column by excess of soluble hapten. The results demonstrate that NCP chromatography appears to be a cheap and useful alternative to many other chromatographic media used for protein immobilization.

Animals↗
PubMed1993

Improvement of antisera raised against complex antigen mixtures by the use of heterologous sources of antigen for immunization.

Polyspecific antisera against antigen mixtures are important tools for many experimental purposes. However, following immunization with extracts containing a great number of different proteins, many antigens remain non-immunogenic. Therefore, the improvement of the antibody spectrum of antisera is an essential goal in maximising the power and applicability of many serological analyses. In the present report we demonstrate that the additional use of heterologous (i.e., antigenically related, but not identical) antigen mixtures for immunization increases the variety of antibodies in polyspecific antisera as well as the antibody titer against weak immunogens.

Animals↗
PubMed1992

A method for the detection of serologically crossreacting antigens both within and between protein mixtures: the western cross blot.

The method described in the present paper permits the detection of antigenically related proteins within or between different antigen mixtures. For this purpose two separate SDS-polyacrylamide gels are run (the antigen mixture is applied to the entire width of the gel) and each gel is blotted on to a separate nitrocellulose paper. One sheet ('donor sheet') is incubated with antiserum and placed on to the other blot ('receptor sheet') so that the antigen bands are perpendicular to each other. Subsequently the antibodies from the donor sheet are blotted on to the receptor sheet in alkaline borate buffer containing 1 M NaSCN, which dissociates antigen-antibody complexes. After the removal of the donor sheet the receptor sheet containing the transblotted antibodies is equilibrated in phosphate-buffered saline in order to reconstitute the binding conditions. Antibodies which have bound to receptor antigens during this equilibration period are detected by the use of a peroxidase labelled 2nd antibody. Because each band on the donor sheet crosses each band on the receptor sheet during the transfer, the antibodies from each band of the donor sheet are able to react with each antigen band of the receptor sheet. The validity of the method was established by demonstrating the crossreactivity of a polyclonal antiserum against the intact bovine gamma globulin molecule with the heavy and light chain subunits (and partial reduction products of the molecule) and the absence of crossreactivity between heavy and light chains. In a second experiment crossreacting antigens of different molecular weight were detected within several strains of Escherichia coli. In addition, comparisons of different strains of Escherichia coli revealed crossreacting antigens of identical as well as of different molecular weight.

Blotting, Western↗
PubMed1988

Antigenic competition in the immune response against protein mixtures: strain-specific non-immunogenicity of Escherichia coli antigens.

Antigenic competition is argued to impair the immune response on the level of accessory cell-dependent antigen presentation to responsive T-cells (regulated by MHC encoded Ir gene products). A possible influence of these mechanisms on in vivo immunization with antigen mixtures was investigated by using cytoplasmic extracts of four different strains of Escherichia coli as antigen sources for immunizing rabbits. The immune response against these antigen mixtures was tested by crossed immune electrophoresis (CIE) and immunoblotting (IB) in a homologous system (a given antigen extract of one strain against the corresponding antisera) and in the heterologous system (antigen extract of one strain against the antisera of different other strains). Several proteins were non-immunogenic in the extract of one strain but elicited good antibody responses in other strains. One of the strain-specific non-immunogenic proteins was purified and revealed a normal immune response upon immunization. The data suggest that different antigenic competition effects are induced by different protein compositions of antigen mixtures. This strain-specific competition seems to determine the immunogenicity of certain molecules (and not only the immunogenic properties of the molecules themselves). Furthermore this method offers a practical approach to increase the antibody production against weak immunogens in antigen mixtures.

Animals↗