The release of microparticles from eukaryotic cells is a well-recognized phenomenon. We demonstrate here that the chemokine receptor CCR5, the principal co-receptor for macrophage-tropic human immunodeficiency virus (HIV)-1, can be released through microparticles from the surface of CCR5+ Chinese hamster ovary cells and peripheral blood mononuclear cells. Microparticles containing CCR5 can transfer the receptor to CCR5- cells and render them CCR5+. The CCR5 transfer to CCR5-deficient peripheral blood mononuclear cells homozygous for a 32-base-pair deletion in the CCR5 gene enabled infection of these cells with macrophage-tropic HIV-1. In monocytes, the transfer of CCR5 could be inhibited by cytochalasin D, and transferred CCR5 could be downmodulated by chemokines. A transfer of CCR5 from peripheral blood mononuclear cells to endothelial cells during transendothelial migration could be demonstrated. Thus, the transfer of CCR5 may lead to infection of tissues without endogenous CCR5 expression. Moreover, the intercellular transfer of membrane proteins by microparticles might have broader consequences for intercellular communication beyond the effects seen for HIV-1.

Antimicrobial peptides are effectors of innate immunity, providing their hosts with rapid non-specific defence against parasitic invaders. In this report, the effects are assessed of two well-characterized antimicrobial amphipathic peptides (melittin and cecropin) on human immunodeficiency virus 1 (HIV-1) replication and gene expression in acutely infected cells at subtoxic concentrations. Production of infectious, cell-free virus was inhibited in a dosedependent manner, with ID 50 values in the range 0n9-1n5 µM for melittin and 2-3 µM for cecropin. Analysis of the effect of melittin on cell-associated

The tyrosine kinase inhibitor imatinib (Gleevec, Novartis Pharmaceuticals Corporation; Basel, Switzerland) is a powerful drug for treatment of chronic myelogenous leukemia (CML) and other malignancies. It selectively targets various tyrosine kinases, thereby leading to growth arrest of respective cancer cells. Given its wide application, it is of high importance to know all related underlying molecular mechanisms. We had previously found that imatinib increases the cellular clearance of intracellular protein aggregates by targeting the abl pathway and thereby upregulating lysosomal activity. Here, we describe that imatinib dose dependently activates the cellular autophagy machinery in mammalian cells, independently of tissue type, species origin or immortalization status of cells. Autophagy is an archetypical cellular degradation mechanism implicated in many physiological and pathophysiological conditions. Our data link for the first time the process of autophagy with the mode of action of imatinib. Induction of autophagy might represent an additional mechanism of imatinib to induce growth arrest, promote apoptosis in cancer cells and eventually even promote tumour regression. Leukemia (2007) 21, 936-942.

Despite worldwide eradication of naturally occurring variola virus, smallpox remains a potential threat to both civilian and military populations. New, safe smallpox vaccines are being developed, and there is an urgent need for methods to evaluate vaccine efficacy after immunization. Here we report the identification of an immunodominant HLA-A*0201-restricted epitope that is recognized by cytotoxic CD8 ؉ T cells and conserved among Orthopoxvirus species including variola virus. This finding has permitted analysis and monitoring of epitope-specific T cell responses after immunization and demonstration of the identified T cell specificity in an A*0201-positive human donor. Vaccination of transgenic mice allowed us to compare the immunogenicity of several vaccinia viruses including highly attenuated, replication-deficient modified vaccinia virus Ankara (MVA). MVA vaccines elicited levels of CD8 ؉ T cell responses that were comparable to those induced by the replication-competent vaccinia virus strains. Finally, we demonstrate that MVA vaccination is fully protective against a lethal respiratory challenge with virulent vaccinia virus strain Western Reserve. Our data provide a basis to rationally estimate immunogenicity of safe, second-generation poxvirus vaccines and suggest that MVA may be a suitable candidate.

Although desirable for safety reasons, the host range restrictions of modified vaccinia virus Ankara (MVA) make it less applicable for general use. Propagation in primary chicken embryo fibroblasts (CEF) requires particular cell culture experience and has no pre-established record of tissue culture reproducibility. We investigated a variety of established cell lines for productive virus growth and recombinant gene expression. Baby hamster kidney cells (BHK), a well-characterized, easily maintained cell line, supported MVA growth and as proficient expression of the E. coli lacZ reporter gene as the highly efficient CEF, whereas other cell lines were non-permissive or allowed only very limited MVA replication. Importantly, no virus production occurred in patient-derived infected primary human cells. These results emphasize the safety and now improved accessibility of MVA for the development of expression vectors and live recombinant vaccines.

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Lizarbe, and K. yon der Mark. 1983. Anat. Rec. 206:373-383). We have studied the expression of genes that typify osteogenic differentiation in mandibular condyles during in vitro cultivation. RNAs of the genes for collagen type I, osteonectin, alkaline phosphatase, and bone gla protein were sequentially expressed in progenitor cells and hypertrophic chondrocytes during culture. Osteopontin expression peaked in both the early and the late phase of the differentiation process. The data indicate a distinct sequence of expression of osteoblast-specific genes during osteogenic differentiation and new bone formation in mandibular condyles.