Sybille Müller

Characterization of conserved properties of hemagglutinin of H5N1 and human influenza viruses: possible consequences for therapy and infection control

BackgroundEpidemics caused by highly pathogenic avian influenza virus (HPAIV) are a continuing threat to human health and to the worlds economy. The development of approaches, which help to understand the significance of structural changes resulting from the alarming mutational propensity for human-to-human transmission of HPAIV, is of particularly interest. Here we compare informational and structural properties of the hemagglutinin (HA) of H5N1 virus and human influenza virus subtypes, which are important for the receptor/virus interaction.ResultsPresented results revealed that HA proteins encode highly conserved information that differ between influenza virus subtypes H5N1, H1N1, H3N2, H7N7 and defined an HA domain which may modulate interaction with receptor. We also found that about one third of H5N1 viruses which are isolated during the 2006/07 influenza outbreak in Egypt possibly evolve towards receptor usage similar to that of seasonal H1N1.ConclusionThe presented results may help to better understand the interaction of influenza virus with its receptor(s) and to identify new therapeutic targets for drug development.

Live Simian Immunodeficiency Virus Vaccine Correlate of Protection: Local Antibody Production and Concentration on the Path of Virus Entry

We sought design principles for a vaccine to prevent HIV transmission to women by identifying correlates of protection conferred by a highly effective live attenuated SIV vaccine in the rhesus macaque animal model. We show that SIVmac239Δnef vaccination recruits plasma cells and induces ectopic lymphoid follicle formation beneath the mucosal epithelium in the rhesus macaque female reproductive tract. The plasma cells and ectopic follicles produce IgG Abs reactive with viral envelope glycoprotein gp41 trimers, and these Abs are concentrated on the path of virus entry by the neonatal FcR in cervical reserve epithelium and in vaginal epithelium. This local Ab production and delivery system correlated spatially and temporally with the maturation of local protection against high-dose pathogenic SIV vaginal challenge. Thus, designing vaccines to elicit production and concentration of Abs at mucosal frontlines could aid in the development of an effective vaccine to protect women against HIV-1.

AIDS epidemic at the beginning of the third millennium: time for a new AIDS vaccine strategy.

Current expansion of AIDS pandemic significantly accelerates AIDS vaccine research resulting in development and clinical testing of several AIDS vaccine candidates. At the same time, available experimental and clinical data demonstrate that current AIDS vaccine strategy is unsuccessful resulting in development of inefficient and harmful vaccines. This overview briefly summarizes reported results which point out the requirement for moratorium on the current clinical trials of HIV-1 gp120/160 vaccines and urgent need for development of a new, efficient and safe AIDS vaccine strategy.

MTS-conjugated-antiactive caspase 3 antibodies inhibit actinomycin D-induced apoptosis.

Caspase 3 is critically involved in the pathway of apoptosis. We have conjugated a MTS-transport-peptide to monoclonal and polyclonal anti-caspase-3 antibodies to suppress Actinomycin D-induced apoptosis in human lymphoma T cells. The advantage of using trans-membrane antibodies compared to conventional apoptosis inhibitors is their specific target recognition in the living cell and their lower toxicity compared to conventional apoptosis inhibitors. We could show that a MTS-transport-peptide modified monoclonal anti-caspase-3 antibody reduces Actinomycin D induced apoptosis, as shown by DNA ladder electrophoresis and cell death ELISA. These results indicate that antibodies have a therapeutic potential to inhibit apoptosis in a variety of diseases.

Bacteria and zymosan opsonized with histone, dextran sulfate, and polyanetholesulfonate trigger intense chemiluminescence in human blood leukocytes and platelets and in mouse macrophages: Modulation by metabolic inhibitors in relation to leukocyte-bacteria interactions in inflammatory sites

Human blood leukocytes and platelets and mouse peritoneal macrophages emit very rapid and very intense Luminol-dependent chemiluminescence (CL) signals when treated with streptococci, staphylococci, or with zymosan, which have been preopsonized with arginine-rich histone, dextran sulfate or polyanetholesulfonate (liquoid). Liquoid alone at 10–30μg/2×105 leukocytes also triggers intense CL responses in the absence of a carrier. Strong CL can also be triggered, and at the same levels, when the various polyelectrolytes are simply mixed with the bacteria or zymosan and added to the leukocyte suspensions. The CL responses induced by the polyelectrolyte-bacteria complexes greatly exceed those triggered in leukocytes by antibody-complement-coated particles. Liquoid also shows a unique property of markedly augmenting CL signals which have already been induced by other ligand-coated bacteria or zymosan particles. Streptococci and staphylococci were found to be much superior to zymosan, Gram-positive bacilli, orE. coli as carriers for the various polyelectrolytes in the CL reaction. Neither protamine sulfate, lysozyme, myeloperoxidase, crystalline ribonuclease (all cationic in nature), chondroitin sulfate, heparin, nor alginate sulfate acted as ligands for triggering CL, when used to opsonize bacteria or zymosan. The induction of CL in blood leukocytes by the various ligand-coated bacteria is markedly inhibited by azide, KCN catalase, aminotriazole, and EDTA, agents known to inhibit the production of oxygen radicals following stimulation of leukocytes by opsonized bacteria. Two children diagnosed for chronic granulomatous diseases (CGD) of childhood and an apparently healthy sister of one of the male patients completely failed to respond with CL either to the polyelectrolyte-bacteria complexes, liquoid or antibody-coated bacteria and zymosan. It is proposed that liquoid be employed for the rapid screening of defects in certain oxygen-dependent metabolic processes in both PMNs and macrophages. It is also suggested that polyelectrolytes like the ones described in this study may markedly enhance the bactericidal properties of leukocytes and macrophages towards both extracellular and intracellular microorganisms and may perhaps also augment the tumoricidal effects of activated macrophages.

TransMabs: cell-penetrating antibodies, the next generation

Intracellular proteins are becoming attractive targets in diagnosis and for therapy such as in signal pathways, on enzymes, transcription factors and structural proteins. Antibodies have been used therapeutically for extracellular pathogens and for targeting cell-surface antigens. Antibodies normally do not pass easily through intact cellular or subcellular membranes in living cells. Methods to shuttle antibodies into living cells are either labour-intensive and/or compromise the structural and functional integrity of the cell or require the integration of genes for heavy and light chain production through gene therapy approaches. A new technology platform, ‘SuperAntibody Technology’, enables antibodies to be shuttled into living cells without harming them. Such cell-penetrating antibodies open new diagnostic and therapeutic windows. The term ‘TransMabs’ has been coined for these antibodies. Proof of principle has been achieved with a 17-amino acid peptide with membrane translocating properties, conjugated with anti-caspase-3 antibody. Such a TransMab inhibits significantly invitro apoptosis-related events, such as caspase-3 activity, DNA fragmentation and spectrin cleavage. Anti-ca-spase-3 TransMab, therefore, could be utilised to inhibit apoptosis in a variety of diseases, such as Alzheimer’s, Huntington’s and P-arkinson’s. Unlike peptide inhibitors available at present, this TransMab is not expected to have invivo toxic side effects and can only target activated forms of the enzyme. This paper discusses the advantages and limitations of cell-penetrating antibodies (TransMabs) compared with existing small molecule drug development approaches.

Live Simian Immunodeficiency Virus Vaccine Correlate of Protection: Immune Complex–Inhibitory Fc Receptor Interactions That Reduce Target Cell Availability

Principles to guide design of an effective vaccine against HIV are greatly needed, particularly to protect women in the pandemic’s epicenter in Africa. We have been seeking these principles by identifying correlates of the robust protection associated with SIVmac239Δnef vaccination in the SIV-rhesus macaque animal model of HIV-1 transmission to women. We identified one correlate of SIVmac239Δnef protection against vaginal challenge as a resident mucosal system for SIV-gp41 trimer Ab production and neonatal FcR-mediated concentration of these Abs on the path of virus entry to inhibit establishment of infected founder populations at the portal of entry. In this study, we identify blocking CD4+ T cell recruitment to thereby inhibit local expansion of infected founder populations as a second correlate of protection. Virus-specific immune complex interactions with the inhibitory FcγRIIb receptor in the epithelium lining the cervix initiate expression of genes that block recruitment of target cells to fuel local expansion. Immune complex–FcγRIIb receptor interactions at mucosal frontlines to dampen the innate immune response to vaginal challenge could be a potentially general mechanism for the mucosal immune system to sense and modulate the response to a previously encountered pathogen. Designing vaccines to provide protection without eliciting these transmission-promoting innate responses could contribute to developing an effective HIV-1 vaccine.

Avoiding deceptive imprinting of the immune response to HIV-1 infection in vaccine development.

Lymphocyte clonal restriction is caused by priming the immune system with an antigen and has been referred to infectious disease study as “original antigenic sin” (OAS), described first for influenza by Francis []. OAS is a dominant feature of a normal immune response. Benefits of OAS come from the initial contact with the pathogen, which induces immunological memory. Memory is achieved by priming B and T cells of an immunologically naive host, and confers protection against infection with the antigen-related pathogen.Thus, a restricted antibody response to viral or parasite antigens is not per se pathogenic. However, the interplay between a “locked-in” immune response and the high genetic variation of the pathogenic agent can result in a deception of the immune system. In the following, clonal restriction of the immune response to HIV is described by giving examples of restricted anti-HIV antibody formation in maternally infected children.Clonal restriction results in host resistance of infected individu...Lymphocyte clonal restriction is caused by priming the immune system with an antigen and has been referred to infectious disease study as “original antigenic sin” (OAS), described first for influenza by Francis [[1]]. OAS is a dominant feature of a normal immune response. Benefits of OAS come from the initial contact with the pathogen, which induces immunological memory. Memory is achieved by priming B and T cells of an immunologically naïve host, and confers protection against infection with the antigen-related pathogen. Thus, a restricted antibody response to viral or parasite antigens is not per se pathogenic. However, the interplay between a “locked-in” immune response and the high genetic variation of the pathogenic agent can result in a deception of the immune system. In the following, clonal restriction of the immune response to HIV is described by giving examples of restricted anti-HIV antibody formation in maternally infected children. Clonal restriction results in host resistance of infected individuals to emerging HIV variants and quasispecies. The problems of classical approaches of vaccine design in AIDS and the lack of protection in vaccinated patients is reviewed.

Protective effects of anti-ricin A-chain antibodies delivered intracellularly against ricin-induced cytotoxicity

AIM To evaluate the ability of anti-ricin A-chain antibodies, delivered intracellularly, to protect against ricin-induced cytotoxicity in RAW264.7 cells. METHODS Anti-deglycosylated ricin A-chain antibody and RAC18 anti-ricin A-chain monoclonal antibody were delivered intracellularly by encapsulating in liposomes or via conjugation with the cell-penetrating MTS-transport peptide. RAW264.7 cells were incubated with these antibodies either before or after ricin exposure. The changes in cytotoxicity were estimated by MTT assay. Co-localization of internalized antibody and ricin was evaluated by fluorescence microscopy. RESULTS Internalized antibodies significantly increased cell viability either before or after ricin exposure compared to the unconjugated antibodies. Fluorescence microscopy confirmed the co-localization of internalized antibodies and ricin inside the cells. CONCLUSION Intracellular delivery of antibodies to neutralize the ricin toxin after cellular uptake supports the potential use of cell-permeable antibodies for post-exposure treatment of ricin intoxication.

The anti-idiotypic antibody 1F7 selectively inhibits cytotoxic T cells activated in HIV-1 infection

Circulating CD8+ T lymphocyte numbers rise substantially following infection with HIV‐1. This expanded CD8+ T cell population includes HIV‐specific CTL and CTL that kill activated uninfected CD4+ lymphocytes. Experimental, epidemiological and clinical evidence supports the possibility that expansion of CD8+ CTL contributes to CD4+ T cell depletion and disease progression in human HIV infection. Therefore, modulation of CD8+ T cell numbers or of certain CD8+ CTL activated in HIV‐infected individuals may be beneficial. It was found that 1F7, a mAb against an idiotype common to anti‐HIV and anti‐simian immunodeficiency virus (SIV) antibodies, selectively inhibited both anti‐HIV CTL and CTL against uninfected CD4+ T cells. Alloantigen‐specific CTL and NK cells from either HIV‐infected individuals or controls were unaffected by 1F7. Prolonged incubation of CD8+ T cells from HIV‐infected individuals with 1F7 induces apoptosis, which was shown to be reflected functionally in reduced total CTL activity and in especially reduced CTL activity against uninfected CD4+ lymphocytes. The selective reactivity of 1F7 with certain CD8+ CTL could be applied towards the modulation of CD8+ T cell responses involved in AIDS pathogenesis.